My unscientific battery endurance test!

[doehunter]

It seems like the board's kinda slow so I thought I'd share my recent test.
Last year I installed a refrigerator and ran it on the batteries to see how long I could let it go. I started that test with only one 50 watt solar panel and not so good batteries. I think I ran about 5 days.
Since then I fried the fridge power supplies and replaced them and this is my 1st time to run it since then. I set it at 34 F. and it goes from about 31 to 36F. during its cycle.

This time I started with new-ish batteries and 2, 50 watt panels.
The fridge runs anywhere from 3.5 to 6 or so amps (about 4.5 on average) and the load seen on my meter is the difference between the load and the solar input.

Half of the week we had very cloudy days and some rain, so I think It could have been better than the results I ended up with. Anyway, I tried to get unloaded and loaded numbers every day while it was running on the batteries and solar. I ran the lights, stereo, and fans only when I was on the boat fooling around, so the fridge was the only real load.
8-24-13, - 7:30am, 12.4vdc unloaded.
8-24-13, - -----------12.0vdc @ +4.4 amps.
8-25-13, -3:00pm, 13.2vdc unloaded @ -2.8 amps. (charging)
8-25-13, -------------12.6vdc loaded@ 1.2 amps. (4.5 amp load less 3.3 amp charge?)
8-26-13,- time?, ----12.4vdc @ 0.0 amps
8-26-13,--------------11.8vdc @ 4.2 amps
8-27-13, 7:30pm, - 12.3vdc @ 0.3 amps
8-27-13, - didn't get a loaded condition
8-28-13, 6:00pm,---12.4vdc @ 0.2 amps
8-28-13, -------------11.8vdc @ 4.5 amps
8-29-13, 7:30pm,---12.1vdc @ 0.5 amps
8-29-13,--------------11.4vdc @ 5.1 amps
8-30-13, 6:30pm,---12.0vdc @ 0.0 amps
8-30-13,--------------11.2vdc @ 5.5 amps

When the fridge kicked in I head a noise like a warning. I think the charge controller did it? Anyway, I figured I pushed it far enough at that point and put the fridge back on AC power.
So I got almost 7 days out of it. I opened the fridge each day and blew in warm air so I didn't have to wait for it to cycle on.
In real life it'll be opened many times per day and there will be other loads as well. I'm not sure how useful this was but it was interesting.

I might do it again and leave the stereo and one cabin light running for the entire time. That might get closer to real world loading. (maybe over the top?)
It's obvious though that when I take my vacation I'll need to be on shore power about very 3rd night at least, so I'll have to make arrangements for that. Right now I don't have an official on board charger. Just an old fashioned battery charger and extension cord.
Jim

 

[Don S/V ILLusion]

What you did is analogous to partially filling, emptying a portion, refilling (to some uncertain %), more pouring out and more refilling a bucket of water without telling us or you how big the bucket is or how much you refilled it every time.

It's hard to draw any real conclusions without knowing both and especially if the bucket started out full.

 

[doehunter]

What you did is analogous to partially filling, emptying a portion, refilling (to some uncertain %), more pouring out and more refilling a bucket of water without telling us or you how big the bucket is or how much you refilled it every time.

It's hard to draw any real conclusions without knowing both and especially if the bucket started out full.

Hmmmm,
Well I started out with full batteries, and only a few things in the fridge.
Sunlight was not consistent.
I can kinda see your point though, and as I said I know it's not really scientific but it kinda tells me I can trust it for 5 or 6 days if I need to.
I guess the real test will happen on the water.

 

[Sumner]

I'd say that with 100 watts of solar what you got for results were about what I'd expect. The noise might of been the fridge. I think that it has a low voltage cutoff so that if you are using it in a vehicle you can still get it started. When we use ours on the road I unplug it at night as I don't want to end up with a dead battery in the morning.

We found that in almost 2 months on the water with the same fridge and no shore power and 180 watts of solar we still had to run the gen-set about 3-4 hours total run time in that time period to supplement the solar. We had somewhat higher usage with a number of hours on the computer each day and my CPAP machine at night. Without that load I think 150-180 watts of solar would probably keep the batteries up for the fridge and other light usage.

Be careful with the car charger on the water it could be very dangerous. We use to use one at home on the land before getting the panels. If I was going to use one on the water in a marina I'd get a marine one and make darn sure my 110 to shore was done properly,

Sum

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[doehunter]

I wonder if the newer solar panels are more efficient? While mine are new to me, they are old technology. You can't even buy them anymore.
It would be nice if I could be self sufficient for 7 days. I'm not there.
I'm guessing I'll run out of power in about 4.
I might look into getting an onboard charger but I don't understand how that's any different than my old car charger.

 

[Sumner]

I might look into getting an onboard charger but I don't understand how that's any different than my old car charger.

The marine ones are built to a higher standard to keep the 110 away form the 12 volt. In the water if you have any stray 110 getting into the 12 volt and the 12 volt goes also to say your outboard and it is in the water that is a real danger to people who might be swimming nearby or to say a diver cleaning a bottom near you.

It isn't just the charger, but the 110 coming from the shore and how it is wired in the boat to avoid the above happening or some of the shore power outlets in marina have faulty wiring or the hot and neutral are accidentally reversed.

I'd at least put in a ground fault outlet on your end in the boat at the end of the shore power line and connect the charger to that.

I'd sure hate to think I was responsible for a death in the water. Here are a couple links...

http://www.westmarine.com/webapp/wc...10001&page=Ten-Deadly-Conditions#.UifaGH_JJj4

http://www.westmarine.com/webapp/wc...10001&page=Ten-Deadly-Conditions#.UifaGH_JJj4

http://qualitymarineservices.net/Neutral-Ground Bond, Exchange Article, 12-2005.pdf

Have fun on your trip,

Sum

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[doehunter]

thanks Sumner,
Interesting reading. I don't have my motor connected yet. It's on my bucket list though! As little as I run my motor and as the small amount it would add makes it kinda low on my list of priorities. (although I guess every little bit helps)
I hope I can spring for a proper on board charger before my vacation. Minimum, I'll have a good heavy extension cord and a GFI.

 

[Yosi]

I wonder if the newer solar panels are more efficient? While mine are new to me, they are old technology. You can't even buy them anymore.
It would be nice if I could be self sufficient for 7 days. I'm not there.
I'm guessing I'll run out of power in about 4.
I might look into getting an onboard charger but I don't understand how that's any different than my old car charger.

Doehunter, I have a solar company producing panels in china from technology we develop in Silicon Valley. Solar technology is constantly improving, but if I had my guess I'd say that those sold for consumer use (RV, marine etc) are several generations old because for a standard solar company that market is negligible in size. Those who make such products most likely buy old stock that manufacturers can't sell for large installations. Yet, a newer panel would probably be more efficient than an old one.

As far as efficiency goes, there are two types: mono/multi crystalline silicon based and thin film. You can easily distinguish: if you see a bunch of square wafers inside its crystalline. If its all one large black film, it is thin film. In clear sun conditions the silicon based will far outperform thin film. However, in haze and excessive temperatures thin film will at least equal and may outperform crystalline. So, for example, if you are in Monsoon prone area, thin film is recommended. In US, crystalline is better.

We make a hybrid product that captures the benefit of both, but we don't have consumer product (other than panels you see on roofs).

I hope this is helpful.

 

[centerline]

doehunter,
what are you using for a charge controller?... and as for the "new-ish" batteries, I am assuming that means 2 batteries, and the term new-ish is relative to many things that may prevent them from falling into the catagory of "good strong batteries"...
what type and size of batts are they?

the fridge shouldnt pull 6 amps for very long before it drops back to about 3.5...

im a bit surprised that with two batteries, 100watts of solar couldnt keep slightly ahead of the fridge in your area.....

also, how well insulated is the fridge? is it a top loader or a side door model... could you unplug it at night to save any power, or would it warm up so much that it would consume the power anyway as it cooled itself down again... with the insulation factor being equal, a top loader would be the most efficient, and a full one is more efficient than an empty one, and a temp of 40degrees should be plenty cool for a refridgerator....

 

[Sumner]

doehunter,
what are you using for a charge controller?... and as for the "new-ish" batteries, I am assuming that means 2 batteries, and the term new-ish is relative to many things that may prevent them from falling into the catagory of "good strong batteries"...
what type and size of batts are they?

the fridge shouldnt pull 6 amps for very long before it drops back to about 3.5...

im a bit surprised that with two batteries, 100watts of solar couldnt keep slightly ahead of the fridge in your area.....

also, how well insulated is the fridge? is it a top loader or a side door model... could you unplug it at night to save any power, or would it warm up so much that it would consume the power anyway as it cooled itself down again... with the insulation factor being equal, a top loader would be the most efficient, and a full one is more efficient than an empty one, and a temp of 40degrees should be plenty cool for a refridgerator....

He is running an Edgestar 63. Ours seems to start at about 5-6 for a very short time and then goes to 3 1/2. In Florida in the spring with daytime highs around 90 and nighttime in the 70's I felt we were using about 35 amp/hr a day for the fridge with it set at 37. We did unplug ours at night and it would be about 45 in the morning and take most of the day to get back down. All told it ran about 40% of the time (24 hour period). Next time we won't unplug it at night.

Over a number of days both sunny and clear I'll guess he is averaging 25-30 amp/hr a day from the 100 watts. If that is true sooner or later even with 2 or more batteries he will find himself in the hole :cry:. We did with 180 over time, but our loads where also greater. I think with the 200 now we will be pretty good indefinitely,

Sum

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[Maine Sail]

Hmmmm,
Well I started out with full batteries,

8-24-13, - 7:30am, 12.4vdc unloaded.

Your data points to batteries that started at approx 70% SOC... 12.4V translates to approx 70% SOC.. Unfortunately in order to get an accurate representation of SOC the batteries need to rest for a long while with no loads or charging. Based on some of those voltages your bank is either undersized for the load or at below 50% SOC which is not good for longevity. On Monday I capacity tested a single 125Ah battery at a 6.25A constant load. Even at a known 50% SOC it was still holding 11.93V with the 6.25A load. The battery turned up a capacity of 117Ah's at 8 years old.. Not bad.......

You have data such as this:

8-30-13,--------------11.2vdc @ 5.5 amps

Compare that with the 8 year old 125Ah battery above and it may give you an indication of how healthy, undersized or what SOC your bank was at.

I happen to be in the shop right now and just measured a pile of batteries I have kicking around. All have been rested for a minimum of five days and some resting for as long as four weeks.

*Lifeline AGM 6V = 6.430 X 2 = 12.86V (resting for approx four weeks)

*US Battery DC31 = 12.853V (resting since Monday)

*Deka DC-27 = 12.732V (resting for approx two weeks)
*Deka DC-27 = 12.733V (resting for approx two weeks)

*Deka GC2 6V = 6.371V X 2 = 12.742V (resting for approx two weeks)

*Ultrapower/JCI Group 27 = 12.714V (resting for approx three weeks)

Wal*Mart US Battery Group 29/31 = 12.718V (resting for approx four weeks)

These are very typical resting voltages of "full" LA batteries.. All voltages recorded with NIST Certified/Calibrated Fluke 179 DVM..

 

[walt]

Yosi, does your company have a web site? The "hybrid" system sounds interesting. Hopefully since I asked here everyone would be comfortable with you posting it (at least I hope).

Cant help but to think anyone with a fridge on one of these small boats sure is a candidate for a battery monitor especially if your running a very minimum battery bank (like 2 batts) and that is pretty much your total battery reserve. Especially important since the relatively heavy load of a fridge could easily leave you without DC power fairly quickly (and no power to the fridge means food spoiling). Looking at Doe Hunters initial posting, voltages are all over the place depending on what is loaded or charging. For example on 8-25 there was a reading of 13.2 and one day later there was a reading of 11.8. But he still got four more days out of the batteries (which might have been pushing the 50% rule of thumb). With the battery monitor, you would know things like exactly what your net amp hours are each day you’re out - way more accurate than trying to read battery SOC from the voltage. Extra info like this would be valuable if for example you wanted to run an auto pilot one day into the trip or even leave a chart plotter on all day and not worry about food spoiling because the battery was too discharged.

 

[Yosi]

Thanks for your interest Walt. website is www.sunpreme.com. We developed a thin film junction that is deposited over crystalline silicon. It gives us high efficiency competitive with traditional crystalline (which is what all Chinese companies do) but also gives us the better performance in haze and extreme temperatures. We developed the only panel that passed hurricane wind certification (over 180mph) and only panel selected for installation in Antarctica.

 

[doehunter]

wow,
that's a lot to take in!
I'm not very electrically savvy but I'm learning a little all the time.
During my testing I had a mix of very cloudy/rainy and sunny days.
Before I started it, my boat had been sitting in the driveway for months. No loads.
A few weeks earlier I checked the battery water and it was a little low so I filled them back up.. Not sure if that affected them or not. Also, the place I bought them from is not a battery store, it's a generic sporting goods store. Academy Outdoors.
Maybe they aren't the best? Not sure. I think they are grp 24., combo starting/deep cycle batteries. I don't remember the capacity.
Yeah, the fridge starts up at around 6 amps for a few minutes and then goes down to about 3.5-4-4.5. It seems to be different at times. I was showing it at max load to show the max voltage sag after the fridge kicked on.
I do know that even though my test wasn't very scientific, it kind of backed up what I saw the 1st time I did it last year. I got about 5 days back then with mismatched batteries and starting out with only 50 watts for the 1st day.
I had wondered if it's worth it to turn the fridge off at night. It seems like it would use the same power because it would have to go from a lot warmer temp in the mornings to the desired temp in the afternoon instead of just maintaining.
Bottom line is I'm not even close to being self sufficient. But, I think I can last for a 3 day weekend, and on my vacation I can anchor out a night or two before having to go to a slip and recharge. I'll probably only be on the water about 5 days, depending on how I feel at the time.

 

[Sumner]

....I had wondered if it's worth it to turn the fridge off at night. It seems like it would use the same power because it would have to go from a lot warmer temp in the mornings to the desired temp in the afternoon instead of just maintaining.

I won't turn it off in the future. In 75-90 deg. temps it would go from 35-37 at about 9 pm when I turned it off and by morning it was 44-45 and would take all day of continuous running to get it back down to 35-37. It was loaded and we would add 2-4 warm cans of pop/beer to it each day. So it would run about 10 hours and be back down about 6-7 at night and then not really come on till I plugged it in the next morning. So 24 into 10 is about a 40% run time for the 24 hours.

It never faltered but I really didn't like it running continuous like that so in the future it will stay plugged in and will cycle on/off over the 24 hours.

One advantage to what I did was I never ran the batteries under 12 volts at night and in the morning if they went there when the fridge was turned on then...

...we ran the gen-set. That way the gen-set was charging the batteries and running the fridge. We never ran the gen-set more than 30 minutes before turning it off and only did this 7-8 days in the 7+ weeks, so considering that we will just leave the fridge plugged in unless something else comes up,

Sum

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[doehunter]

Up date,
I learned a lesson this weekend.
I've been thinking that my voltage drop under load was a lot. I assumed my batteries were the issue and I almost bought new batteries. I decided to do one last test to confirm, I'm glad I did.
I put a volt meter right on the battery and compared it to the volt meter in my panel.
About 7:30 am, so not much sunlight on my solar panel and almost no load.
I had about 12.45 volts showing on both meters.
The fridge kicked on and my panel meter read 11.7 volts, while the meter at the battery read 12.31!
Then I turned on everything in the boat, cranked the stereo way up, and made my load 10.5 amps. The panel meter read, just under 11 volts, while the meter on my battery read 12.2 volts.
So, I think that's a good indication that my batteries are fine and I have a bottle neck somewhere in my wiring.
I took out my panel and measured everywhere and I was not getting full voltage to it.
I looked under the galley where the PO had a main on/off switch and a fuse.
The fuse holder and the wires coming out of it were very warm!
hmmmm. I took that section out. Now I have #10 wires all the way from my batteries through that switch and on to the breaker panel where all the circuits connect to.
Now, even with a big load the two meters read almost the same.
The moral to the story is "size matters"!

 

[Sock Puppet]

Thanks for the update! That's good info.

 

[vizwhiz]

Do you plan to put a larger fuse (still with appropriate rating) back in for protection?

 

[walt]

Good point to consider the fuse.

In this case (and assuming proper fusing in the initial configuration), the wire gauge went from smaller diameter to larger diameter so if there was a short, the existing fuse would still blow and the wire would be even less likely to burn. The existing fuse would still protect the wire in a short.

It’s the opposite case where the fuse would need to be re-sized. I.e., if you had a fuse sized for some wire and then you changed the wire to a smaller diameter, now you would not know which would blow first - the fuse or the wire. So it would be wise to re-consider the fuse size if you change to a smaller diameter wire.

But in this case of going to a larger diameter wire, as long as the fuse doesn’t nuisance blow, whatever is in there should still be OK after the gauge change.

 

[doehunter]

the PO only had the basic factory wiring that was for the nav lights (the little extension cord wires!) and he added a VHS radio. He put in a main on and off switch in the neg wire under the galley and all the branch negatives went there too. It was the only switch in the boat.
Since then I've added quite a lot of things AND moved my batteries to the V berth.
I now have a fuse in the positive wire right at the battery so, I removed the old fuse in the negative wire and it's short length of smaller wire. Now I have #10 running from the neg side of the battery to the main on/off switch and then up to my breaker panel.
Should I also have a fuse in the neg wire up close to the battery? I figured the one on the positive side was enough.
All of the branch circuits have either a breaker or an inline fuse.
Well, except for my fridge and it really needs one. All of the breakers were already in use and I think I forgot to put in a fuse for it. I need to check that.
I even got rid of the cheesy little 12 volt cigarette lighter style plug it came with and have it hard wired in. It needs a fuse where I made that connection.
I was in the boat last night, finished my cabinet install and was listening to some music. Just for fun I cranked it up really loud and watched the volt meter.
It used to jump around a lot when I did that. I have 4 indoor/outdoor house speakers and the volt meter dropped a lot with surges from the stereo.
http://www.frys.com/product/3985308?site=sr:SEARCH:MAIN_RSLT_PG

Now it only has very slight dips. Hardly perceptible. It pulls about 1.5 to 2 amps like that, give or take.
I'm in the middle if switching all my lighting to led. I installed one over the galley and I think it pulls about .1amp!
I installed a cheap stick on one in the head and it's really bright.
I still need to do my nav lights.