Alternator sizing
- Thread starter Scott B
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While it can be done it's not easy nor is it cheap. Pulley off sets often need to be milled at a machine shop or spacers added to keep the belt in alignment. If you are going to move from 3/8" to 1/2" you'd probably be better served to go to a double pulley system as the PITA of doing so would be better justified. The crank, water pump and alt pulleys all must be in alignment and this can involve much headache, shimming and milling. I have yet to see anyone making a specific kit of pulleys to do an upgrade like this for certain engine models.
Also keep in mind that for every 25 amps of alternator output roughly 1hp of engine is consumed. At peak output a 100 amp alt can consume 4hp.
On a 20hp diesel a 100 amp alt can use nearly 20% of the available horsepower for brief periods. On a one lunger 10hp diesel you can hit nearly 40%..Balmar.net said:
Assuming you're talking about SIX VOLT golf cart batteries, like Trojan T105s, a four-battery bank would have 450 amp-hours.
Each T105 is rated at 225 amp-hours at 6 VDC. To get 12 Volts with four of them, you would need to have two sets of two wired in parallel, with each set connected in series. That gives each set 225 amp-hours at 12VDC and the total for the four batteries is 450 amp-hours at 12 VDC.
When you wire batteries in series, you don't add the amp-hours—the amp-hours remain the same, but the voltage doubles. When you wire batteries in parallel, you add the amp-hours, but the voltage remains the same. Here, you're doing both.
If you're planning on using a smart regulator with temperature compensation to charge the batteries, you could go with as large as a 150-amp alternator or so. The minimum alternator you'd probably want to use is 100-amps or so. Same thing with the AC-powered battery charger—you'll probably want something in the range of 90-140 amps or so, provided it is a temperature-compensated, three-stage, intelligent charger to minimize charging times.
Each T105 is rated at 225 amp-hours at 6 VDC. To get 12 Volts with four of them, you would need to have two sets of two wired in parallel, with each set connected in series. That gives each set 225 amp-hours at 12VDC and the total for the four batteries is 450 amp-hours at 12 VDC.
When you wire batteries in series, you don't add the amp-hours—the amp-hours remain the same, but the voltage doubles. When you wire batteries in parallel, you add the amp-hours, but the voltage remains the same. Here, you're doing both.
If you're planning on using a smart regulator with temperature compensation to charge the batteries, you could go with as large as a 150-amp alternator or so. The minimum alternator you'd probably want to use is 100-amps or so. Same thing with the AC-powered battery charger—you'll probably want something in the range of 90-140 amps or so, provided it is a temperature-compensated, three-stage, intelligent charger to minimize charging times.
it is a system
You should not just go enlarging things just for the sake of enlarging them. You need to do your home work to find the best solution to YOUR sailing habits.
A day-sailor that can connect to shore power may not even need and alternator.
Some one who motors a lot can get by with a smaller alternator.
A cruiser will want as large an alternator (and battery bank) as practical to limit re-charging and running the engine at anchor. That is what drives most cruisers to "go solar and wind"
I would suggest you get a copy of my spread sheet and fill it out. then you can see how all the stuff effects your system. you may get some insights as to how to "spread the load" so as to reduce or eliminate your need for more generating capacity.
william-roosa@us.army.mil
You should not just go enlarging things just for the sake of enlarging them. You need to do your home work to find the best solution to YOUR sailing habits.
A day-sailor that can connect to shore power may not even need and alternator.
Some one who motors a lot can get by with a smaller alternator.
A cruiser will want as large an alternator (and battery bank) as practical to limit re-charging and running the engine at anchor. That is what drives most cruisers to "go solar and wind"
I would suggest you get a copy of my spread sheet and fill it out. then you can see how all the stuff effects your system. you may get some insights as to how to "spread the load" so as to reduce or eliminate your need for more generating capacity.
william-roosa@us.army.mil
Battery life
Scott, Could it be your group 27's are near the end of thier life? I have 4 golf carts and on weekends out I never go below 75% capacity running fridge, TV, lights and my wife even uses a hair drier.
The other thing to check is your shore charger - mine was original equipment and it was the problem. I replaced it with a 3 stage Xantrex 40 and also have a 3 stage regulator on the alternator.
I would not go above 80 amps due to the power draw on the engine - I have a yanmar 27 hp.
Get the battery monitor and you will find where your power is being consumed - you would be amazed at what some of the old lights draw.
I also read an article once and remember this - old batteries don't die - they are murdered.
Scott, Could it be your group 27's are near the end of thier life? I have 4 golf carts and on weekends out I never go below 75% capacity running fridge, TV, lights and my wife even uses a hair drier.
The other thing to check is your shore charger - mine was original equipment and it was the problem. I replaced it with a 3 stage Xantrex 40 and also have a 3 stage regulator on the alternator.
I would not go above 80 amps due to the power draw on the engine - I have a yanmar 27 hp.
Get the battery monitor and you will find where your power is being consumed - you would be amazed at what some of the old lights draw.
I also read an article once and remember this - old batteries don't die - they are murdered.
Don, the 2 -27's are original, 2005. I added another battery when we bought the boat, but the marina hooked it up to the one original for the house bank and left the other original as the engine batt. This may have "murdered" the original although I switched them around last year.
We spend most weekends out and at least one full week per season, we've had it for 2 seasons and have averaged 30 nights on the hook per season. During the week it's hooked to shore power Sun. night to Fri. night, we keep food in the fridge and I like cold beer Fri. night. I looked at the charger last year and recollect it was Xantrex, it is original.
After all this discussion, I'll probably get 4 SIX VOLT ( for dawg ) GC batteries, 440 Ah, from Sam's Club, add a LinkLite battery moniter, stick with the original 80 amp alt and see how we do this season.
I did get the spreadsheet from Bill, ( thanks BTW) and check our energy consumption. It lookes like a very detailed spreadsheet, so will have to spend some time with it.
After that, maybe we'll just have to get a bigger boat with bigger battery capacity.
We spend most weekends out and at least one full week per season, we've had it for 2 seasons and have averaged 30 nights on the hook per season. During the week it's hooked to shore power Sun. night to Fri. night, we keep food in the fridge and I like cold beer Fri. night. I looked at the charger last year and recollect it was Xantrex, it is original.
After all this discussion, I'll probably get 4 SIX VOLT ( for dawg ) GC batteries, 440 Ah, from Sam's Club, add a LinkLite battery moniter, stick with the original 80 amp alt and see how we do this season.
I did get the spreadsheet from Bill, ( thanks BTW) and check our energy consumption. It lookes like a very detailed spreadsheet, so will have to spend some time with it.
After that, maybe we'll just have to get a bigger boat with bigger battery capacity.
Maine Sail, Perhaps I'm missing something, or don't understand your calculations. If I have a 440Ah bank and take it to 50% I then have 220Ah remaining. If I then charge to 90% capacity I will have 396 Ah in the bank (440x90%). Now I only have 176 Ah available if I am not taking the bank below 50% on the subsequent cycle (396-220=176). If there is an error in my calculations please explain.
Dennis your math is spot on. On a 440 ah bank at an 80% re-charge you would have only 132 amp hours available before hitting the 50% capacity level. At a 90% of capacity recharge you would have 176 usable amp hours. I mistakenly, in a rush, used only half the bank in my calculations in post #18 when I meant to use the entire bank for calculation purposes.. Good catch!!
Ross, I'll start the weekend at full and I'm assuming that with a monitor I'll keep an eye on the Ah and run the engine as required to top the batteries. Some weekends we motor for 3 - 3 1/2 hours with no or very little wind to get to our favorite spots. or if the wind is dead on we'll motor instead of doing 4 hours of 10-15 min. per tack.
Scott, if your batteries are up when you leave the dock it doesn't matter how long you run the engine getting to where you are going, your battery is charged after two days on the hook you need to run for several hours to recharge the battery. If you used 160 AH you have to put that back by running the engine or plugging into the grid. If you have an eighty amp alternator you must run at least two hours, but if you have a 400 ah bank and draw down 250 ah you must run at least 3 1/2 hours to put it back. After the three and a half hours you can run for a week and you won't build a reserve.
Ross—
If he's used 160 Amp-hours from a fully charged bank of 440 amp-hours, it will take a lot longer than 2 hours to put it back with an 80 amp alternator, since the charge acceptance rate drops dramatically once the batteries reach about 85% capacity. From 280-374 amp-hours, it'll probably take as much as the alternator can put out, but then the charge acceptance rate will start dropping, and getting from 374-440 amp-hours again may take as long as ten hours.
This is one reason Xantrex and a lot of cruising boats use the 35%/85% rule. They size the battery bank so that the actual required usage is only about 35% of the bank's actual size, and generally count on regularly charging the batteries to only 85% most of the time, with only an occasional charge up to 100% to help prevent sulfation and other problems. Charging the batteries from 50-85% takes far less time than charging the batteries from 85-100%.
If he's used 160 Amp-hours from a fully charged bank of 440 amp-hours, it will take a lot longer than 2 hours to put it back with an 80 amp alternator, since the charge acceptance rate drops dramatically once the batteries reach about 85% capacity. From 280-374 amp-hours, it'll probably take as much as the alternator can put out, but then the charge acceptance rate will start dropping, and getting from 374-440 amp-hours again may take as long as ten hours.
This is one reason Xantrex and a lot of cruising boats use the 35%/85% rule. They size the battery bank so that the actual required usage is only about 35% of the bank's actual size, and generally count on regularly charging the batteries to only 85% most of the time, with only an occasional charge up to 100% to help prevent sulfation and other problems. Charging the batteries from 50-85% takes far less time than charging the batteries from 85-100%.
So I should be aiming to keep it in the 85% range until I get back to shore. Usually on the longer trips there are days where we motor all day, so should be enough to keep the batteries up.
Stu, I definitley want to read through your posts and try to understand it along with Calder etc., but my absorption rate for this stuff right now is less than than 10% and my Ah remaining are running very low with the economy in the condition it's in. I'm in construction, so learning new "boat knowledge" is way down the absoprtion rate right now. I really appreciate being able to come on here and having the combined knowledge at least point me in the right direction, which you all have. As much as I have a passion for sailing and enjoy learning new things, I need sailing to relax my brain and put it into crusie mode.
Alternator Too Big - Max Charge Rates
If anybody is still interested I found an excellent explanation on this site http://www.mpoweruk.com/chargers.htm of why it is bad news to have too high a charge rate or too large an alternator. There is lots of other good stuff there too.
An extract follows:-
Charge Termination
Once a battery is fully charged, the charging current has to be dissipated somehow. The result is the generation of heat and gasses both of which are bad for batteries. The essence of good charging is to be able to detect when the reconstitution of the active chemicals is complete and to stop the charging process before any damage is done while at all times maintaining the cell temperature within its safe limits. Detecting this cut off point and terminating the charge is critical in preserving battery life. In the simplest of chargers this is when a predetermined upper voltage limit, often called the termination voltage has been reached. This is particularly important with fast chargers where the danger of overcharging is greater.
Safe Charging
If for any reason there is a risk of over charging the battery, either from errors in determining the cut off point or from abuse this will normally be accompanied by a rise in temperature. Internal fault conditions within the battery or high ambient temperatures can also take a battery beyond its safe operating temperature limits. Elevated temperatures hasten the death of batteries and monitoring the cell temperature is a good way of detecting signs of trouble from a variety of causes. The temperature signal, or a resettable fuse, can be used to turn off or disconnect the charger when danger signs appear to avoid damaging the battery. This simple additional safety precaution is particularly important for high power batteries where the consequences of failure can be both serious and expensive.
Charging Times
During fast charging it is possible to pump electrical energy into the battery faster than the chemical process can react to it, with damaging results.
The chemical action can not take place instantaneously and there will be a reaction gradient in the bulk of the electrolyte between the electrodes with the electrolyte nearest to the electrodes being converted or "charged" before the electrolyte further away. This is particularly noticeable in high capacity cells which contain a large volume of electrolyte.
There are in fact at least two key processes involved in this chemical conversion. One is the "charge transfer", which is the actual chemical reaction taking place at the interface of the electrode with the electrolyte and this proceeds relatively quickly. The other is the "mass transport" or "diffusion" process in which the materials transformed in the charge transfer process are moved on from the electrode surface, making way for further materials to reach the electrode to take part in the transformation process. This is a relatively slow process which continues until all the materials have been transformed.
Both of these processes are also temperature dependent.
If anybody is still interested I found an excellent explanation on this site http://www.mpoweruk.com/chargers.htm of why it is bad news to have too high a charge rate or too large an alternator. There is lots of other good stuff there too.
An extract follows:-
Charge Termination
Once a battery is fully charged, the charging current has to be dissipated somehow. The result is the generation of heat and gasses both of which are bad for batteries. The essence of good charging is to be able to detect when the reconstitution of the active chemicals is complete and to stop the charging process before any damage is done while at all times maintaining the cell temperature within its safe limits. Detecting this cut off point and terminating the charge is critical in preserving battery life. In the simplest of chargers this is when a predetermined upper voltage limit, often called the termination voltage has been reached. This is particularly important with fast chargers where the danger of overcharging is greater.
Safe Charging
If for any reason there is a risk of over charging the battery, either from errors in determining the cut off point or from abuse this will normally be accompanied by a rise in temperature. Internal fault conditions within the battery or high ambient temperatures can also take a battery beyond its safe operating temperature limits. Elevated temperatures hasten the death of batteries and monitoring the cell temperature is a good way of detecting signs of trouble from a variety of causes. The temperature signal, or a resettable fuse, can be used to turn off or disconnect the charger when danger signs appear to avoid damaging the battery. This simple additional safety precaution is particularly important for high power batteries where the consequences of failure can be both serious and expensive.
Charging Times
During fast charging it is possible to pump electrical energy into the battery faster than the chemical process can react to it, with damaging results.
The chemical action can not take place instantaneously and there will be a reaction gradient in the bulk of the electrolyte between the electrodes with the electrolyte nearest to the electrodes being converted or "charged" before the electrolyte further away. This is particularly noticeable in high capacity cells which contain a large volume of electrolyte.
There are in fact at least two key processes involved in this chemical conversion. One is the "charge transfer", which is the actual chemical reaction taking place at the interface of the electrode with the electrolyte and this proceeds relatively quickly. The other is the "mass transport" or "diffusion" process in which the materials transformed in the charge transfer process are moved on from the electrode surface, making way for further materials to reach the electrode to take part in the transformation process. This is a relatively slow process which continues until all the materials have been transformed.
Both of these processes are also temperature dependent.
Georgian bay battery
Hello, I think we might sail the same boat. Hunter 33. Ours is a 2005.
We are on are second set of batteries. Started with 2 and one house. Added one more house.
Third year replaced all three with four house. one starter and two 80 solar panels.
I believe your alternator is a 60 amp. Thats on the wish list. The cadilac alternator will run you 900 to 1200 dollars. The solar panel cost me about 1200 and it works great. Keeps them charged at 13 amps all day from 10 on if there is sun.
The alternator is a big ticket item. Do you spend the money on that our solar.
I have a great guy that can set you up with solar. He sails out of Hindsons.
tmackinlay@sympatico.ca his name is Tim. Great guy. tell Jason gave you his name.
He can even set you up with a great wireless antenna for internet if you want.
Happy sails
Anika Lela
Hello, I think we might sail the same boat. Hunter 33. Ours is a 2005.
We are on are second set of batteries. Started with 2 and one house. Added one more house.
Third year replaced all three with four house. one starter and two 80 solar panels.
I believe your alternator is a 60 amp. Thats on the wish list. The cadilac alternator will run you 900 to 1200 dollars. The solar panel cost me about 1200 and it works great. Keeps them charged at 13 amps all day from 10 on if there is sun.
The alternator is a big ticket item. Do you spend the money on that our solar.
I have a great guy that can set you up with solar. He sails out of Hindsons.
tmackinlay@sympatico.ca his name is Tim. Great guy. tell Jason gave you his name.
He can even set you up with a great wireless antenna for internet if you want.
Happy sails
Anika Lela
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