pianotuna
Regina, SK, Canada
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Hi mena,
Self discharge does vary by battery and chemistry and age. I know you are aware there are almost no constants in the battery business. It is always a slippery slope. You have an almost brand new bank.
Regards, Don
Kustom Koach Class C 28'5" 256 watts Unisolar, 875 amp hours in two battery banks 12 volt batteries, 2500 MSW watt inverter.
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mena661
Southern California
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pianotuna wrote:Hi mena,
Self discharge does vary by battery and chemistry and age. I know you are aware there are almost no constants in the battery business. It is always a slippery slope. You have an almost brand new bank. Yeah, I know. Thanks though. I can probably use that data to tell when they start going south. Once I get my IR thermometer, I'm going to start keeping a spreadsheet of battery temp vs SG vs voltage. once I get the "trends and tendencies" down then I won't need to do as many hydrometer tests to know where my batts are at.
2009 Newmar Canyon Star 3205, Ford F53 V10
Trojan L16 6V's 740 Amp-hours
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KendallP
Grants Pass, OR
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SteveAE wrote:Sometimes we engineering types can get too wrapped up in theoretical, rather than empirical, data...
Can I PLEASE get an "AMEN???"
However in this case, I agree with mena. This experimental horse has been beaten to death many times over. He wants to start with 200W. That won't cut it for a reasonably quick recharge from, say 50% SOC.
Solar is great and is especially great for batteries when it keeps them from getting down near 50%. Shallow DODs make for long, healthy battery lives.
Mene-dog's concerns are valid. He wants to minimize the time that the cells are left in a low SOC in order to best stave off hardened sulfation. Again... WAY dead horse for some of us around these boards, but certainly not common knowledge we expect everyone else to hold.
Cheers,
Kendall
1986 Winnebago Chieftain 22RC
Our Camper (with no payments)
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smkettner
Southern California
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We need some imperical data on 200w charging 4x L16 from 50%.
I think it will not be nearly as bad as the common knowledge seems to express.
But then Mena would need to actually need to allow discharge to 50% 
2001 F150 SuperCrew
2006 Keystone Springdale 249FWBHLS
675 watts solar
Send a PM if I missed something
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Salvo
California
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I would say 200W will make a tremendous improvement. He wouldn't have to keep a large battery bank either.
smkettner wrote:
I think it will not be nearly as bad as the common knowledge seems to express.
But then Mena would need to actually need to allow discharge to 50%
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KendallP
Grants Pass, OR
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Not sure whether or not you've looked at mena's usage, but he lieka' da' juice!
Returning from a foggy boondocking session... even with a 200W panel could easily leave him well below 50%. But, yeah. Let's just take the 50%, to make it easy.
I gotta' run out to a meeting. So someone please provide a rough estimate of how long it would take to supply 360 Ah from a 200W panel with 50% cloud cover plus a controlled overcharge at 15.5V for, say 2 hours.
(Hint) I'm betting it's not gonna' get done in day. 
If so... please tell me where I can get me THAT 200W panel!!!
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pianotuna
Regina, SK, Canada
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Hi KendallP,
It is rather worse than that. 200 watts of panels might do 180 watts on a really perfect day. On a day such as you are describing I'd derate to 90 watts.
370 amp-hours =~4800 watt-hours. At 90 watts and five hours per day....ten to eleven days.
On the other hand I'm "charging" my 500 amp-hour bank at the moment--at 0.2 amps @ 13.6 volts.
Back to the salt mines for me.
Ok, it is over cast and I turned on the fridge to load the battery bank. I'm getting 4 amps @ 13.5 volts from 256 watts of Uni-solar panels in a series parallel configuration. It is overcast with some breaks in the clouds. So 54 watts @ 1:50 p.m. Mountain time, or about 1/5 of rated output. Temperature is 15.6 C (about 60 F)
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Salvo
California
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Looks like fuzzy math to me.
We talking about the same guy? Here's his usage:
We're not heavy users but we use a decent amount of power. We have yet to get below 85% SOC though.
Total usage from his 740 AH batteries is:
Trip usage = 740 AH * (1-0.85) = 111 AH
Is that over a 3-day period? If so, usage per day is:
Usage per day = 111 AH / 3 = 37 AH
In winter I record 30 AH of battery charging per day from 130W.
If he gets a 200W panel, charging per day is:
Charge per day = 30AH * 200W / 130W = 46 AH
I call that a tremendous boost!
Cal
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mena661
Southern California
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smkettner wrote:We need some imperical data on 200w charging 4x L16 from 50%.
I think it will not be nearly as bad as the common knowledge seems to express.
But then Mena would need to actually need to allow discharge to 50% I have an electric blanket that MAY run off my 300W inverter that I need to do some testing on. 
KendallP wrote:Not sure whether or not you've looked at mena's usage, but he lieka' da' juice! Yeah, I'm no BFL but I like to use stuff. For Salvo, my bank was designed for rain outs and cooler weather. I have to admit when I designed it, I didn't know about capacity shrinkage when the weather gets cooler or I would've added another pair of L16's. I'm hoping the 200W will make up for some heater usage during the day and float and equalize (periodically...and hopefully that's programmable) them at home. The DW wanted to be able to hole up in the 5er and watch TV all day if we were rained out or snowed in while camping.
EDIT: Salvo, usage averages 150Ah per 3 day trip.
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pianotuna
Regina, SK, Canada
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Hi mena,
You aren't me either. I do strange and wonderful things such as never using propane to cook. A thousand watt hot plate eats into a battery bank lickety split.
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