Solar or Wind???

walt

.
Jun 1, 2007
3,511
Macgregor 26S Hobie TI Ridgway Colorado
Daily Power usage pie chart..

Load / Amp hours
VHF radio / 0.76
car stereo / 4.5
cabin lights / 1.2
computer / 8
depth finder / 0.68
Fridge / 35

(the electric fridge completely dominates the power usage by a large margin)
 

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walt

.
Jun 1, 2007
3,511
Macgregor 26S Hobie TI Ridgway Colorado
One more somewhat interesting thing if you are considering a fridge. This is a Mac forum and also has some folks who have X and M models with the larger outboards. I looked at one 70 hp outboard and it had a 28 amp alternator and it likely puts out that current over a large rpm range - way more than the 5 or 6 amp you might get with an under 10 hp. This gets closer to the current generation capability of larger boats and also is probably adequate backup for solar if the weather doesn’t cooperate for a few days. Backup for not getting solar would be running the outboard for about an hour - maybe even at idle (just guessing on the idle)
 
Feb 26, 2004
22,759
Catalina 34 224 Maple Bay, BC, Canada
... I looked at one 70 hp outboard and it had a 28 amp alternator and it likely puts out that current over a large rpm range - way more than the 5 or 6 amp you might get with an under 10 hp. This gets closer to the current generation capability of larger boats and also is probably adequate backup for solar if the weather doesn’t cooperate for a few days. Backup for not getting solar would be running the outboard for about an hour - maybe even at idle (just guessing on the idle)
Walt, the math doesn't work.

1. Most inboard engines have at least 55A alternators (except for many Yanmars with 35A ones; most M25 series engines on Universals that came with Catalinas have 55A OEM alternators).

2. Many if not most skippers who cruise (i.e., not marina hoppers) have upgraded their alternators to 75, 90 or 100 A or more, with external regulation.

3. Idle doesn't get much output, from any alternator unless it is specifically designed and selected for high output at low rpms. And most of us know that running an engine at idle is bad for the engine and doesn't charge very much.

4. Unless the fridge is super low draw AND/OR the box is super insulated, the rule of thumb for a fridge is 50-60 AH per day (24 hours). An hour run time with even the largest alternator mentioned (i.e., 100A) will simply NOT replenish that in an hour, especially at idle.

The design criteria for a solar system is to be able to replenish one's daily use by solar input and to NOT depend on motor backup. IIRC, Sumner covered this stuff pretty well in his website writeups.
 

walt

.
Jun 1, 2007
3,511
Macgregor 26S Hobie TI Ridgway Colorado
Walt, the math doesn't work.

Stu, am I supposed to guess which math doesnt work?

Most outboard "here" are under 10 hp. Some have rectifiers only and only put out full charge at high rpms. Some of the newer under 10 hp outboards have a rectifier plus "regulator" (such as the Tohatsu and Nissan 9.8 hp) but they still only put out about 5 or 6 amps.

Did you check which forum you were posting to?

FYI, your number of 50 to 60 amp hours per day makes the fridge a much larger problem for trailer boats that use an under 10 hp outboard. The 35 amp hour number came from Sumner - who I think probably did a good job of estimating how much power is needed.
 
Apr 29, 2010
209
MacGregor m25 Erieau, Ontario, Canada
Walt, the math doesn't work.

1. Most inboard engines have at least 55A alternators (except for many Yanmars with 35A ones; most M25 series engines on Universals that came with Catalinas have 55A OEM alternators).

2. Many if not most skippers who cruise (i.e., not marina hoppers) have upgraded their alternators to 75, 90 or 100 A or more, with external regulation.

3. Idle doesn't get much output, from any alternator unless it is specifically designed and selected for high output at low rpms. And most of us know that running an engine at idle is bad for the engine and doesn't charge very much.

4. Unless the fridge is super low draw AND/OR the box is super insulated, the rule of thumb for a fridge is 50-60 AH per day (24 hours). An hour run time with even the largest alternator mentioned (i.e., 100A) will simply NOT replenish that in an hour, especially at idle.

The design criteria for a solar system is to be able to replenish one's daily use by solar input and to NOT depend on motor backup. IIRC, Sumner covered this stuff pretty well in his website writeups.
Fair enough, but you wrote this on the c34 forum:

" Your energy budget will tell you how many days that will last you. That is, add up all the loads times how many hours per day you use them, which will give you needed amp hours per day. (BTW, with your 440 AH bank, you will do JUST FINE!)

A 100 amp alternator will put out 100 amps at a certain speed. Jeff's right about the output curve. Plus, if you're anchored, you won't be running the engine at max speed, only about 1500 rpm.

If motoring you'll get more out of the alternator.

So, say with inefficiencies and slow motoring or just at high idle when anchored, you get 75 amps out of the alternator.

If you've used up all 154 amp hours, it'd take you two hours to put it back.
"


So wouldn't a 100 amp alternator replace the 60 amp hours for the fridge in a little less than an hour at a fast idle or am I missing something?

My Mac is a clean slate electrically and I want to do it up correctly.
 

Sumner

.
Jan 31, 2009
5,254
Macgregor & Endeavour 26S and 37 Utah's Canyon Country
....So wouldn't a 100 amp alternator replace the 60 amp hours for the fridge in a little less than an hour at a fast idle or am I missing something? .
One thing that is overlooked is that the battery is not going to charge at the same rate and the amps it is able to use from the alternator will depend not on the alternator's output but the batteries ability to accept.

On the Mac we have 2 12 volt group 27 batteries at the moment. We were out day after day and kept them at over 50% charge. A few times if I felt they were getting discharged more than I liked before night fall or were discharged more than I liked in the morning we would run the generator with the 12 volt car alternator. it is a GM 3 wire, I have a 1 wire on my hot rod.



With the 3 wire you can use a switch on the field. It is important if you are hand starting the engine that is powering the alternator as it makes it possible to pull the starter rope without the alternator putting a load on at the time trying to produce electricity.

Used with the batteries at or above 50% the most I ever saw it putting out was about 24 amps, way below the 60 amp rating. That was only for the first few minutes of charge and they it would continue downwards from that point and within 30 minutes or less it would only be putting about 10-12 amps into the batteries. At this point we are at diminishing returns so I would stop and let the solar top the batteries off while they also supplied the power for the fridge. The fridge didn't discharge the batteries much since it was only on during the day for about 9-10 hours and the panels were working very well for about 6 of those hours.

A lager alternator would do nothing to increase the charge time with our batteries. Now there are other charge circuits that can be made that can force a charger to charge at a higher rate than the batteries acceptance rate. I didn't feel the need to go that way as you need to be very careful doing this.

The lager alternators come into their own when cruisers with lager boats have larger battery banks that can accept more and when at times they draw them down below 50%.

On the amp/hrs per day for the fridge remember this is the numbers I feel good about for our 63 quart Edge Star in Florida with mid 80 degree cabin temps and adding 2-3 warm drinks a day to the fridge and other food when we did get ashore. Different fridge or different use will mean more or less than the 35 amp/hrs. I feel ours is using during those time. It was less in Nov./Dec. when the cabin was in the 40's at night and 60'd during the day but also there was less daylight hours for the panels and the sun was lower in the sky.

I've lived in the northwest two different times and both times from mid-June to almost Sept. there was a lot of sun and long days. I think we would be fine there during those months but not the rest of the year, but I wouldn't be cruising then anyway.

One has to determine their needs/wants and then work around that. I use to backpack and take canoe trips that were 8-10 days and had no fridge and had a great time. We started with an ice box, actually 2 in the boat, One with food and ice and the other with just ice or frozen food until it defrosted. For us we didn't like this situation due to where we went and how we used the boat (much different than most). We found it restricting where we went and how long we were able to stay there. Upper Priest Lake in Idaho has no marinas so we weren't able to stay there as long as we would of liked to. Even Priest Lake didn't have a lot and planning on where we were on the lake to get to one was a pain. Lake Powell is a similar situation. Forget marinas in parts of Florida like the 10,000 Islands and the Everglades and even in the Keys they aren't everywhere. Due to weather you can't always stay on a set schedule that will put you where ice is and it is amazing that one really big problem in parts of Florida is actually finding a place you can go ashore for supplies. We also just aren't marina people although we recognize a lot of people really enjoy them. If you are only staying in them to recharge batteries they aren't cheap and a few nights will start to buy a lot of solar.

One solution for someone that doesn't need solar most of the time is making some mounts for the panels that make adding or removing them easy. Say have a 100 watt panel on the boat all the time and just add another 100 watt for trips. 200 watts will take care of a fridge like ours about anyplace one is going to sail. If you start dipping into the low 50% range start shutting things down. Another option is buying one of the small generators for $100 or less and stow it away with a compatible charger and take it out those few times you might need to help the solar out.

The other option that costs more and is more work is to make is a permanent fridge with Stu's 'super insulation'. We did that on the Endeavour and it is almost twice the size of the portable and yet uses about 2/3's the amp/hours. Most of the big boats that have fridges are not super insulated and do have the amp/hr. usage that Stu commented on.

So determine your goals and work towards a solution, there is one,

Sumner
 
Last edited:
Apr 29, 2010
209
MacGregor m25 Erieau, Ontario, Canada
Thanks Sumner.

That helped a lot in understanding the solar/alternator charging system.

Frank
 

walt

.
Jun 1, 2007
3,511
Macgregor 26S Hobie TI Ridgway Colorado
Sumner, first, thanks for putting out the numbers you have seen on your setup, they are useful to me and Im sure others.

I’m a little surprised by the acceptance numbers however – but I also have no data points myself. I wonder what acceptance limited bulk charging current Maine Sail has has seen with two golf cart batteries in good shape and a “smart” charger?

Battery acceptance is due to both the charger and the battery. The charger is trying to put current into the battery and it is measuring the voltage while doing so. If the voltage rises to some set point, the charger cuts back as the battery cant “accept” more charge at some voltage limit (or voltage algorithm). As an example, I have two charging sources on my boat and they have slightly different battery acceptance numbers. My outboard will start to cut back current when it detects the battery voltage is near 13.4 and will nearly have shut off when the voltage is near 13.6 volts. We could assume that this is the acceptance limit of the battery – except that the solar charge controller (with a microprocessor) thinks this is far from the acceptance limit and it will keep pumping all the amps of current available into the battery long after the outboard charging has shut off. So the same battery has different acceptance from the outboard charger vs.. the solar charge controller – because they limit at different voltage profiles.

You’re diagram shows #8 wire. I thought you had 4 gauge between the battery and the charger but if you are using 8 gauge, might be another reason you had relatively low current. You’re batteries are up near the front of the boat and the gas charger is near the rear so when its putting current out to the batteries (on the other end of the boat), it is sensing the voltage for when to cut back – at the generator. If you have a round trip of say 50 foot of 8 gauge wire, that has a resistance of maybe .03 ohms. This doesn’t seem like much but would drop 0.6 volts at 20 amps. So the sensing on the generator would think the battery voltage is 0.6 volts higher than it actually is and would cut back the current too soon.

Also, as batteries age, their internal impedance goes up. Since the higher impedance results in a higher battery voltage as current is being put into it, the charger also limits current sooner than would occur for a new battery. The two golf cart battereis may also have inherently lower internal impedance vs. the two 12 volt battereies, dont know.

The rule of thumb numbers are useful and using 35 amp hours per day for a fridge like Sumner has seems like a good number for this application. It would be useful to also have a rule of thumb number for about how much current you can jam into say two golf cart batteries "in bulk mode" and my guess is that numbers between 24 amps to 12 amps might be too low. Note that the bulk charging range for two golf cart batteries (50 to say 80%) is nearly double the 35 daily amp hours the fridge uses.

I think you may be able to get higher acceptance with a 110 VAC gas generator and a smart chager placed near the batterires. For example, my 6 amp charger will put out exactly 6 amps into my batteries if they are in bulk mode so I assume a 30 amp charger would do the same assuming a large enough battery and in bulk charging range (and my guess is that two six volt batteries in bulk mode would meet this?). If you have the charger near the battery with proper wire size, I think you could assume it would charge in bulk to voltage like 14.4 volts so I believe it would keep on charging the battery long after the auto alternator for Sumner’s data point (where the charger and the battery are also separated by a long wire run). If the gas generator (which would now be AC) were still at the back of the boat, the wire run to the charger would be at 110 VAC and this has no influence on the battery acceptance.

The power at 30 amps and 13 volts is only 390 watts so a under 30 pound 1000 watt AC generator would work fine for this (typically just a little over 2 hp gas motor). But… if you’re going through all this hassle in the first place, if you used a 2000 watt AC generator, you can also add a microwave oven to the boat (might as well - you are now well into the RV sailboat configuration..)

But, I hope anyone that puts a generator on a boat considers the noise. In Feb I was in a campground and a neighbor had a very quiet generator on "all the time". We were “commenting” on it during dinner and on the water, sound carries a lot further. But I think you probably could find times to run a “very quiet” generator when it would not be rude to others around you. And the higher the amps you can pump into the batteries, the less time it needs to run,.
 
Feb 6, 1998
11,665
Canadian Sailcraft 36T Casco Bay, ME
Sumner, first, thanks for putting out the numbers you have seen on your setup, they are useful to me and Im sure others.

I’m a little surprised by the acceptance numbers however – but I also have no data points myself. I wonder what acceptance limited bulk charging current Maine Sail has has seen with two golf cart batteries in good shape and a “smart” charger?

Battery acceptance is due to both the charger and the battery. The charger is trying to put current into the battery and it is measuring the voltage while doing so. If the voltage rises to some set point, the charger cuts back as the battery cant “accept” more charge at some voltage limit (or voltage algorithm). As an example, I have two charging sources on my boat and they have slightly different battery acceptance numbers. My outboard will start to cut back current when it detects the battery voltage is near 13.4 and will nearly have shut off when the voltage is near 13.6 volts. We could assume that this is the acceptance limit of the battery – except that the solar charge controller (with a microprocessor) thinks this is far from the acceptance limit and it will keep pumping all the amps of current available into the battery long after the outboard charging has shut off. So the same battery has different acceptance from the outboard charger vs.. the solar charge controller – because they limit at different voltage profiles.

You’re diagram shows #8 wire. I thought you had 4 gauge between the battery and the charger but if you are using 8 gauge, might be another reason you had relatively low current. You’re batteries are up near the front of the boat and the gas charger is near the rear so when its putting current out to the batteries (on the other end of the boat), it is sensing the voltage for when to cut back – at the generator. If you have a round trip of say 50 foot of 8 gauge wire, that has a resistance of maybe .03 ohms. This doesn’t seem like much but would drop 0.6 volts at 20 amps. So the sensing on the generator would think the battery voltage is 0.6 volts higher than it actually is and would cut back the current too soon.

Also, as batteries age, their internal impedance goes up. Since the higher impedance results in a higher battery voltage as current is being put into it, the charger also limits current sooner than would occur for a new battery. The two golf cart battereis may also have inherently lower internal impedance vs. the two 12 volt battereies, dont know.

The rule of thumb numbers are useful and using 35 amp hours per day for a fridge like Sumner has seems like a good number for this application. It would be useful to also have a rule of thumb number for about how much current you can jam into say two golf cart batteries "in bulk mode" and my guess is that numbers between 24 amps to 12 amps might be too low. Note that the bulk charging range for two golf cart batteries (50 to say 80%) is nearly double the 35 daily amp hours the fridge uses.

I think you may be able to get higher acceptance with a 110 VAC gas generator and a smart chager placed near the batterires. For example, my 6 amp charger will put out exactly 6 amps into my batteries if they are in bulk mode so I assume a 30 amp charger would do the same assuming a large enough battery and in bulk charging range (and my guess is that two six volt batteries in bulk mode would meet this?). If you have the charger near the battery with proper wire size, I think you could assume it would charge in bulk to voltage like 14.4 volts so I believe it would keep on charging the battery long after the auto alternator for Sumner’s data point (where the charger and the battery are also separated by a long wire run). If the gas generator (which would now be AC) were still at the back of the boat, the wire run to the charger would be at 110 VAC and this has no influence on the battery acceptance.

The power at 30 amps and 13 volts is only 390 watts so a under 30 pound 1000 watt AC generator would work fine for this (typically just a little over 2 hp gas motor). But… if you’re going through all this hassle in the first place, if you used a 2000 watt AC generator, you can also add a microwave oven to the boat (might as well - you are now well into the RV sailboat configuration..)

But, I hope anyone that puts a generator on a boat considers the noise. In Feb I was in a campground and a neighbor had a very quiet generator on "all the time". We were “commenting” on it during dinner and on the water, sound carries a lot further. But I think you probably could find times to run a “very quiet” generator when it would not be rude to others around you. And the higher the amps you can pump into the batteries, the less time it needs to run,.
Sumners acceptance issues are most likely:

#1 Self sensed alt / voltage drop issues eg: alt sees its own voltage before wire & termination VD and batt terminals are lower thus lower accepted current.

#2 Sulfated batteries eg: Sulfated batteries come up to limiting voltage far too quickly the begin limiting current.


It is most likely a combination of #1 & #2 but his alt is far larger than two G-27 flooded batts can comfortably accept thus he will hit limiting voltage far earlier......

I have done this test numerous times with healthy batteries. This is but one example:

125Ah Group 31 "Deep Cycle" battery fed a 20% of "C" charge rate, or 25A, after being discharged to 50% SOC. It took 1.7 Hours in bulk or constant current charging to hit absorption voltage. If your batteries come up to limiting voltage, with 20% of "C" faster, then there is a voltage or battery issue.

2 Min = 12.59V / 25A = BULK / Constant Current
10 Min = 13.0V / 25A
20 Min = 13.12V / 25A
30 Min = 13.22V / 25A
40 Min = 13.33V / 25A
50 Min = 13.45 / 25A
60 Min = 13.6V / 25A
70 Min = 13.76 / 25A
80 Min = 13.95 / 25A
90 Min = 14.16V / 25A
100 Min = 14.39 / 25A
102 Min = 14.4V / 24.5A = ABSORPTION VOLTAGE / Attained Voltage Limiting
 

Sumner

.
Jan 31, 2009
5,254
Macgregor & Endeavour 26S and 37 Utah's Canyon Country
You are right that I do have #4 wire now. When I put in the first 40 watt panel and didn't have the elect. start Tohatsu I had #8 for the ground and the positive wire. When I went to 180 watts of solar I used the two #8's as my ground and put in the #4 as the positive.

The batteries are not deep cycle 6 volt but as I've mentioned 2 12 volt RV/Marine batteries that as we know are more car battery vs. true deep cycle batteries. Were they sulfated? I don't know but I kind of doubt it as they were both pretty new at the time with one being about 4 months newer. Same brand, same type and both less than a year old and had been kept charged with the 40 watt panel before adding the other 140 watts..

If I would of put a 6 amp charger on them I'm sure they would of accepted that but remember I never let the batteries below 50% and usually charged way ahead of that because I didn't want them going down below there. I think if I would of let them go down to say 40% or so I probably would of seen initial charging rates of over 40 amps for a bit before it started dropping. I don't like running the generator so when I do I'm watching what is going on and turning it off as soon as I'm down to 12 amps or there abouts.

The solar really took care of over 90% of our needs. Remember we only ran the generator/alternator about maybe 6 hours total in 7 weeks of being out continuously. That isn't much, maybe 30 minutes every 3rd to 4th day on the average. Considering that I don't see initial charge rates of 22-24 amps as being out of line.

The guy we bought our Endeavour from said he ran the diesel to charge about an hour in the morning and an hour in the evening which I read a lot of people do cruising. That was with 4 deep cycle 6 volt batteries. Even doing that they were pretty shot when we bought the boat. I can't see putting all of those hours on a diesel just to charge batteries. Solar is a much better and way cheaper option in the long run for someone that is a cruiser.

Let's remember these are real numbers not theory, so what someone else can expect in real use using similar equipment. If someone duplicated our setup I'll bet they would get pretty similar results and is the reason I've posted the results.

Some of the acceptance might of been using a GM alternator but I think it has more to due with the battery types being used at the time,

Sumner

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Sumner

.
Jan 31, 2009
5,254
Macgregor & Endeavour 26S and 37 Utah's Canyon Country
....It is most likely a combination of #1 & #2 but his alt is far larger than two G-27 flooded batts can comfortably accept thus he will hit limiting voltage far earlier.......
I think that is the case and the fact that they were never fully down to 50%.

On your test was that 25 amps going into 4 deep cycle 6 volt batteries? If so that would be about like my 2 12 volts accepting 12 1/2 amps about what they are doing once I switch over to the solar.

I still think some of it has to mainly do with the RV/Boat batteries acting like regular car starting batteries.

Another reason why we will switch over to true deep cycle batteries when these are shot and why I've suggested to others to do the same if they are replacing batteries,

Sumner

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walt

.
Jun 1, 2007
3,511
Macgregor 26S Hobie TI Ridgway Colorado
Sumner, you sold the big boat.. Must be happy and sad.. but you can now spend time on the Mac – which is still going to be a good thing.

edit - woops.. I mis read that.. the guy you BOUGHT the boat from (not SOLD). Sorry..

Maine Sail, exactly what I was wondering. For your data point, a 125 amp hour battery (single group 31) was able to take in 41.66 amp hours (at 25 amps and 100 minutes) in bulk charging. So I think its probably a reasonable assumption that the 1000 watt gas generator with 110 VAC output and a good quality 30 amp “smart” charger could put out near 30 amps into a 225 amp hour set of golf cart batteries in bulk mode (which is about a 70 amp hour range for the golf cart battereis). FYI, I had picked a 30 amp charger to keep the price down somewhat and I like the weight of the 1000 watt gas gensets (under 30 pounds), the 2000 watt ones get closer to 50 pounds.

This is another somewhat interesting thing since we are discussing solar powering a high current load like a fridge.

I have two different setups (one being my sailboat) where a small solar panel is keeping a battery charged (through a solar charge controller) while I am not around. One thing to always remember about any type of solar charge controller is that they are a piece of electronic equipment that must get power to operate and they almost always get their power from the battery. They do not get their power to operate from the solar panel.

So if you have some situation where you have a load on the battery that exceeds what the solar panel is putting out, this will draw the battery voltage down. This could be a string of cloudy days, snow covering the panel or in a case I had, the panel got blown by the wind so it was no longer pointed at the sun.

If whatever the load is keeps on draining the battery, at some point it the battery voltage can go below what the solar charge controller needs for its electronics to run. So even if the sun comes back and now is putting out great charge from the panel, the charge controller is still looking at battery voltage to run – but it may be too low. So even though you now have good solar, the charge controller wont turn on and the battery will continue to drain to zero.

Which brings up something to consider if you have a fridge on solar and want to leave the boat for a while.. I think those fridges have some sort of 12 volt “low voltage disconnect”. In the case of the solar panel and multiple days of cloudy weather, you would want the fridge to shut off at a HIGHER voltage than the solar controller needs to operate. For example, if the solar charge controller needed 10 volts for the electronics to work and the fridge turned off at 11.5 volts, hopefully your unattended system would recover when the sun returned. But if the fridge turned off at 9 volts and but the solar charge controller was dead at 10… you might come back to find a dead system even in bright sunlight.

This has happened to me with a PWM type controller and I’ve heard of this happening also with MPPT controllers.. Its also why you cant use any type of charge solar charge controller to bring up a very low battery – the charge controller just never turns on.

On my boat, I manage this by simply having the solar daily output MUCH higher than what is needed to keep the battery from discharging. With the fridge power by solar, I just would not leave it running unattended for too long.
 
Feb 6, 1998
11,665
Canadian Sailcraft 36T Casco Bay, ME
I think that is the case and the fact that they were never fully down to 50%.

On your test was that 25 amps going into 4 deep cycle 6 volt batteries? If so that would be about like my 2 12 volts accepting 12 1/2 amps about what they are doing once I switch over to the solar.

I still think some of it has to mainly do with the RV/Boat batteries acting like regular car starting batteries.

Another reason why we will switch over to true deep cycle batteries when these are shot and why I've suggested to others to do the same if they are replacing batteries,

Sumner

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Sumner it was a 20% of "C" / Ah Capacity charge rate. Battery was a 125Ah group 31. Just like your Group 27's it is an "adapted" for marine use battery.

20% of "C" occurs very similarly across all flooded batts.

100Ah battery = 20A Charge Rate
125Ah battery = 25A Charge Rate
90Ah battery = 18A Charge Rate

2 group 27 Deep Cycle batteries are likely 90Ah each or 180Ah's for the two:

180Ah Battery = 36A of current to hit 20% of "C"

12.5A would be a 7% of "C" charge rate.

The simple rule for current limiting / attaining absorption voltage is this:

The HIGHER the charge current rate the sooner you hit voltage limiting / absorption

The LOWER the charge current rate the later you hit voltage limiting / absorption
 

Sumner

.
Jan 31, 2009
5,254
Macgregor & Endeavour 26S and 37 Utah's Canyon Country
....125Ah Group 31 "Deep Cycle" battery fed a 20% of "C" charge rate, or 25A, after being discharged to 50% SOC. It took 1.7 Hours in bulk or constant current charging to hit absorption voltage. If your batteries come up to limiting voltage, with 20% of "C" faster, then there is a voltage or battery issue.

2 Min = 12.59V / 25A = BULK / Constant Current
10 Min = 13.0V / 25A
20 Min = 13.12V / 25A
30 Min = 13.22V / 25A
40 Min = 13.33V / 25A
50 Min = 13.45 / 25A
60 Min = 13.6V / 25A
70 Min = 13.76 / 25A
80 Min = 13.95 / 25A
90 Min = 14.16V / 25A
100 Min = 14.39 / 25A
102 Min = 14.4V / 24.5A = ABSORPTION VOLTAGE / Attained Voltage Limiting
I take it from the constant 25 amp charging rate that you weren't using an alternator but a charger where you could set the charge rate. Is that right?

If so I'd be interested in seeing your test done with an alternator similar to the GM one I used. I had found charging circuits that I could of made that would of allowed us to set the charge rate from the alternator. They would of overrode the internal charging circuit that was dropping the rate as the battery became charged. You can find this info on some of the home solar sites where people that are off the grid do supplementary charging with a charging system like what I made. It is also where I found the info on building the generator/alternator system. The auxiliary circuits allow you to set the charge rate like I saw in your example above but you do need to keep track of what is going on when charging in this manner. I decided against that as I just didn't see the need since what we have is working so well.

Now with 200 watts of solar vs. the 180 we had I really think that if at times I just limited my computer time or maybe cut the CPAP back by an hour or so we could keep the batteries over 50% on just the solar alone and run the fridge normally with not need for auxiliary charging.

No Walt we didn't sell the Endeavour but right now we are going through some health issues with Ruth where I don't think we will be able to take the Mac out again. With the larger solar array on the Endeavour and maybe by increasing it we might be able to take trips with the Endeavour. Time will tell and no the Mac isn't up for sale. If we can't deal with the situation on the Endeavour it might be up for sale. For those of you that are waiting for retirement to take your dream trips maybe rethink that. We are extremely thankful for the trips we did get to take. They will be memories we will always have,

Sumner
 

walt

.
Jun 1, 2007
3,511
Macgregor 26S Hobie TI Ridgway Colorado
Sumner, I wonder if you could also run a voltage sensing wire from your regulator right to the battery? This would need to have a voltage sense plus its own ground. I have to measure voltages all the time for work and if the measurement is sensitive, you always make sure that wires sensing voltage have no current flowing through them. This might get a little complicated because what ever is sensing has to have both the sense line and the ground with no current flowing in them. The ground might be a little complicated. Also, didn’t those old style regulators cut back the charging in the 13.6 volt range? I think newer ones go to over 14 volts. If you look at Maine Sails data, the battery voltage got up to 13.6 volts at one hour - but still kept up for another 40 minutes at the same peak current going up to 14.4. Maybe a "smart regulator" on your setup would also help get the amps up.

Just out of interest, using Maine Sails 20% of C for charging, "in theory", you could put up to 45 amps (remember this is bulk charging only) into a set of golf cart batteries rated at 225 amp hours.

The link below is a 40 amp charger for about $400 and if wired correctly, should really be able to dump the charge into the batteries fast - cutting back on how long the generator was run. 40 amps is still just 520 watts at 13 volts so the 1000 watt generator should be still able to handle this. This is getting a little expensive (if you get the Honda or Yamaha 1000W genset) but this would really minimize how long the charger would run. Thsi setup would also only add maybe 35 pounds total to the boat.

http://www.defender.com/product.jsp?path=-1|328|2289962|2289967&id=1512432
 

Sumner

.
Jan 31, 2009
5,254
Macgregor & Endeavour 26S and 37 Utah's Canyon Country
Sumner, I wonder if you could also run a voltage sensing wire from your reguator right to the battery? This would need to have a voltage sense plus its own ground. I have to measure voltages all the time for work and if the measurement is sensitive, you always make sure that wires sensing voltage have no current flowing through them. This might get a little complicated becasue what ever is sensing has to have both the sense line and the ground with no current flowing in them. The ground might be a little complicated. Also, didnt those old style regulators cut back the charging in the 13.6 volt range? I think newer ones go to over 14 volts. If you look at Maine Sails data, the battery voltage got up to 13.6 volts at one hour - but still kept up for another 40 minutes at the same peak current going up to 14.4. Maybe a "smart regulator" on your setup would also help get the amps up. ....
I guess I have to ask why? Why do anything different than what we were doing? 7+ weeks and only having to use the charging system for 6 hours total to me is getting the job done. Why complicate it more? I think most full time cruisers would be ecstatic with those results and with the 200 watts now the results would even be better.

The GM alternator is a new type and charges at 14.3 volts initial.

On the Endeavour we upped it to 480 watts and the fridge uses less. I planned no generator/charger for that boat, but would have our Honda 2000 on board just in case we ever needed 110 power.

I guess I still don't understand all of the 'questioning' and 'trying to improve' what we used since it worked so well. Maybe build your own system and report back with the results,

Sumner
 

walt

.
Jun 1, 2007
3,511
Macgregor 26S Hobie TI Ridgway Colorado
Why change anything for you? No good reason but I think for someone else looking into this, they may want to do things different.

Your case worked just fine but here is what you got for a 5 hp motor plus a 60 amp alternator.. Using the 24 amps for 1/2 hour and then about 12 amps, you were first getting about 324 watts max and then half that. This maybe needs about 1 hp gas motor or less to generate but you are carrying around the weight of a 5 hp. Same argument for the alternator, way under utilized.

For someone considering this now, the 1000 watt gas generator and a 40 amp battery charger might cost more but I would guess weigh a LOT less. And for a good set of golf cart batteries in bulk charging, should put out over double the power you were getting - and for a lot longer time. The Honda and Yamaha generators also have the noise problem "sort of" figured out. No matter what, someone looking into this needs to deal with the CO issue.
 

Sumner

.
Jan 31, 2009
5,254
Macgregor & Endeavour 26S and 37 Utah's Canyon Country
Walt when we are carrying a month's worth of food, fuel, water and waste do you think the 20-30#'s difference in weight of what we were using an what you are suggesting really makes any difference.

We did build and use what we have. It isn't jsut talk. I also suggested what you are suggesting earlier in this post as I don't expect 99% of the people out there to build what I did.

I knew I shouldn't of returned to this post and don't see why you want to make it about what we have done. Do your own thing and report back and quit picking what I did apart.

Sumner
 
Feb 6, 1998
11,665
Canadian Sailcraft 36T Casco Bay, ME
I take it from the constant 25 amp charging rate that you weren't using an alternator but a charger where you could set the charge rate. Is that right?

If so I'd be interested in seeing your test done with an alternator similar to the GM one I used. I had found charging circuits that I could of made that would of allowed us to set the charge rate from the alternator. They would of overrode the internal charging circuit that was dropping the rate as the battery became charged. You can find this info on some of the home solar sites where people that are off the grid do supplementary charging with a charging system like what I made. It is also where I found the info on building the generator/alternator system. The auxiliary circuits allow you to set the charge rate like I saw in your example above but you do need to keep track of what is going on when charging in this manner. I decided against that as I just didn't see the need since what we have is working so well.

Now with 200 watts of solar vs. the 180 we had I really think that if at times I just limited my computer time or maybe cut the CPAP back by an hour or so we could keep the batteries over 50% on just the solar alone and run the fridge normally with not need for auxiliary charging.

No Walt we didn't sell the Endeavour but right now we are going through some health issues with Ruth where I don't think we will be able to take the Mac out again. With the larger solar array on the Endeavour and maybe by increasing it we might be able to take trips with the Endeavour. Time will tell and no the Mac isn't up for sale. If we can't deal with the situation on the Endeavour it might be up for sale. For those of you that are waiting for retirement to take your dream trips maybe rethink that. We are extremely thankful for the trips we did get to take. They will be memories we will always have,

Sumner
The Delco internal voltage regulators vary in absorption voltage set points, as low as 13.8V to as high as 15.0V, but they are simple constant current / constant voltage regulators. It was not until well after the 10SI alts etc. that they added temp compensation to protect the alternator from cooking itself..

This means either you are at absorption voltage, and it is "limiting voltage", or you are in BULK or constant current. These regs only do two things, CC (bulk) & CV (absorption) just like any charge source will. The battery is what limits current the alternator only limits voltage WHEN AT ABSORPTION VOLTAGE or when it THINKS the batteries are at absorption voltage. If the alt is sensing voltage at itself it can begin liming voltage far too early....

My test would be identical if I used an alt set to 25A and the voltage was set to 14.4V, basic Ohm's law... The only things that change the outcome are size of the current source or changing the voltage set point.
 

walt

.
Jun 1, 2007
3,511
Macgregor 26S Hobie TI Ridgway Colorado
I thought all I did was suggest some minor improvements - then answered why when asked.

FYI, I think you did do a good job on what you set up for how you use the boat. And, its always easier to find an improvement when you know what someone else did and have some data from what they did.

I will never use this boat (classic 26) to cruise like that.. just about everyone who I see try ends up getting a larger boat. I use it more as a very trailerable "weekender" that sails fairly well so weight is always important to me. These are about the smallest 26 ft boats out there and have a small sail plan - which works fine on the light weight boat. No problem at all if someone else uses the boat more for comfort however - as I get older that also becomes more important to me.

Anhow.. I think some useful stuff came out here..