Two battery banks instead of one long parallel string

Bloom · November 2013

Thanks to everyone for the education. I've been reading and searching and making drawings... I know that my equipment is not the best. Its been called crap. But it is what I have and could afford at the time. I seriously thought about buying a better system but this one works (for now!). Until its broken, I'll continue to use it and improve my knowledge. For my small system, I learned a lot from reading and re-reading http://handybobsolar.wordpress.com/the-rv-battery-charging-puzzle-2/ It is an RV based article but I found it very useful, in addition to the hundreds if not thousands of forum topics I've read and the awesome pictures.

To my utter disappointment, I found that my PV array isn't strong enough to charge my full bank of seven batteries. In addition, it is unwise to have seven batteries in parallel according to the advice I received. So, what I pondered was - making two separate banks of three parallel batteries in each. According to the 5%ers, I'll be right on the ragged edge of being able to fully charge my 315ah bank. Since my cabin isn't occupied full time, the bank has plenty of time to sit uninterrupted and charge. What I was thinking is that I could arrange the second bank on a marine battery switch between the batteries and the charger. It would allow me to utilize the back-up bank if I get cloudy weather for an extended period at the cabin.

I've seen this set-up discussed in another topic but it was for a much larger system than mine. I would like to draw out my idea but I use long hand and have not seen even ONE chicken scratch drawing shared LOL. Maybe I missed it - its a big forum. I'm thinking of fusing each bank of course, putting the marine battery switch on the positive leads. The negatives from the batteries I'd connect to a large (300a) bus bar.

It seems feasible. I'd like to do something to be able to salvage the batteries if they're still good. I'll check them with the hydrometer when I get there. I'm going next week so I'm hoping to have my ducks in a row before I get there. No phone service (or internet) and getting something, should I forget or break something is a wasted day travelling.

I would appreciate any advice.

Kind Regards,
Bloom

westbranch · November 2013

Re: Two battery banks instead of one long parallel string

best advice I can think of is to borrow/rent a small inverter (quiet) generator and take along a battery charger and boost all those batteries while you are there, now, so they will not deteriorate over the winter.

vtmaps · November 2013

Re: Two battery banks instead of one long parallel string

Bloom wrote: »

I'll check them with the hydrometer when I get there. I'm going next week so I'm hoping to have my ducks in a row before I get there. No phone service (or internet) and getting something, should I forget or break something is a wasted day travelling

Don't forget to take a gallon of distilled water for the batteries.

westbranch wrote: »

best advice I can think of is to borrow/rent a small inverter (quiet) generator and tank along a battery charger and boost all those batteries while you are there, now, so they will not deteriorate over the winter.

Good advice! And boost them one-at-a-time. If they are parallel when you charge them, you will not be charging them evenly.

--vtMaps

8n-bob · November 2013

Re: Two battery banks instead of one long parallel string

Agreeded take a generator and charge each cell separately.
You might take 2 gallons of distilled water just to be safe.
The big thing is to get thdm charged so they dont sit in sub 32 temps Bad for the batts

Good Luck and have fun
BobO

westbranch · November 2013

Re: Two battery banks instead of one long parallel string

8n-bob wrote: »

take a generator and charge each cell separately.

BobO one minor correction to your statement, you will be charging each BATTERY, not cell, individually. Your batteries are made up of 6 cells , of which you need to check the SG of each.

hth

Bloom · November 2013

Re: Two battery banks instead of one long parallel string

Thanks for the responses! I will take the advice offered and charge each one individually after they're disconnected from the bank. The batteries were topped off with water about two months ago, so I'll bring a couple of gallons of distilled with me. That was a great reminder. I have a charger and generator already at the cabin.

After I try to breathe life into these batteries I was thinking to try a SunSaver Dual Battery Controller http://www.solar-electric.com/modubachco25.html . With the amount of time between visits to the cabin, it should work great. Although I will have to rewire my panels to 12V. So far it looks like a good solution, IF i have enough batteries alive... If not, plan B - whatever that might be.

Thanks again,
Bloom

8n-bob · November 2013

Re: Two battery banks instead of one long parallel string

westbranch wrote: »

BobO one minor correction to your statement, you will be charging each BATTERY, not cell, individually. Your batteries are made up of 6 cells , of which you need to check the SG of each.

hth

OOPS My Bad. I guess I was a little tired when I wrote that. Charging a cell would be a real trick

It will not be the first time I have stood corrected, and probably not the last.

westbranch · November 2013

Re: Two battery banks instead of one long parallel string

No problem, we all can get the terms mixed up... for example I have a 12 cell 24V battery (2V cells) but each cell (2V) is in a separate case so could also be called a 2V battery as it is stand alone. There are also 4V batteries made up of 2- 2V cells and 6V batteries made up of 3- 2V cells.

Two battery banks instead of one long parallel string

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