# Need help-w-batteries!



## TheRiver (Mar 31, 2012)

I have 2 deep cell and 2 Reg car batteries. 1 deep cell and 1 car are new, and, 1 deep cell and 1 car are reconditioned. I want to eventually hook them to wind or solar to charge but for now I have them hooked together to run a trolling motor(haven't tested yet). Would this setup work with an inverter to be a source of back up power(not for whole house, but "some" electricity). Really wondering about mixing the 2 kinds for a battery bank.


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## FatTire (Mar 20, 2012)

the short answer is no. the trouble with batteries is, the strong cells feed the weaker cells, and the weaker cells are a black hole. you could make it work, short term, but i dont think thats the question you are asking. 

the single biggest hurdle to off grid solar is batteries. both in terms of maintenance and initial cost, batteries are a big limiting factor


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## mosquitomountainman (Jan 25, 2010)

The answer is "yes" ... and "no." You could hook them together in parallel circuits and run a trollling motor or inverter from them. Like FT said though, the weak batteries will feed off the strong ones until the strong batteries are no better than the weak ones. (Kind of like communism.)

The battery bank will never be more efficient than the weakest battery in the bank. We purchase all of our batteries for the battery bank at the same time. Each battery is identical. When one fails we can take it out of the system and use those that are left awhile longer or we replace all of the batteries. We do not put new batteries in with old batteries or mis-matched batteries.

If you run batteries with different capacities (as in deep cycle with automotive batteries) the lower capacity batteries will reach a state of discharge sooner and the stronger batteries will try to recharge them until they are all equal voltage.

If it was me and I had no other options I'd run the inverter off one battery at a time and switch it to the next one as they discharged.


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## MrDean (Jun 29, 2012)

Re batteries.

You can not combine different brand or type batteries.
You can not combine batteries that are different in age more than 6 months. The new batteries quickly take on the charactistics of the older battery.


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## mosquitomountainman (Jan 25, 2010)

FatTire said:


> ...the single biggest hurdle to off grid solar is batteries. both in terms of maintenance and initial cost, batteries are a big limiting factor


The single biggest hurdle to off grid solar is electrical demand ... not batteries.

We have a neighbor who uses a 65 watt panel and one deep cycle battery. He runs a 12 volt television from it. He leans the panel against a tree and brings out his battery to charge it off the panel then takes it back in the cabin at night.

The cost to live off-grid will depend mostly on how much power you need. If you think you need to live the same way off-grid as you do under grid power you'd better have a pile of money 'cause you're going to need it. However, if you can seriously cut down on your electrical needs you can get by with a lot less.

In our system it costs us about $15.00 per month and that's almost all related to replacing batteries every few years. The *solar panels are the priciest component initially *but have a twenty-plus year life expectancy so your per-year cost is lower. The same is true of charge controllers and inverters. Now I don't know about others on this board but we can live with a $15.00 per month power bill. (But then we're also set up to live entirely without electricity if the need arises.)

It's important with any solar power system to set it up properly balanced with the right amount of charging and battery capacity in relation to electrical usage. Otherwise your battery life can be shortened significantly.


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## TheRiver (Mar 31, 2012)

Thank guys, that is what I needed to know! You all kept me from making a big mistake.


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