Old and new batery with load !!

Dec 3, 2012 07:15 pm
Old and new batery with load !!

I know everybody say that it is not good to add new batery to an old batery bank

But it is still true with a constand load ?
I do have my freezer always took 2.5 amp from the bank
in this case i think that the batery cannot interact together ?

if i swicth off my freezer i see that my old bank 450 amp/h is charging my new bank 200 amp/h with 0.5 amp

I had a baterie monitor for the Both bank old and new who are in paralel , and one baterie monitor on the new bank

but then i put back the freezer, i get in Total minus 2.5 amp from the two bank , and  minus 1 amp from the new bank
that mean minus 1.5 old bank and 1 amp new bank

SO what to you think about mixing old and new baterie in this case
with a constant load
26 Posts
May 10, 2013 03:52 pm
Re: Old and new batery with load !!

I don't think there is a problem with it.  In fact, I think it is a fair way to extend the life of older, weaker batteries by giving them a strong buddy to prevent from over-draining.  I don't think the type of load is particularly important.  As long as they are in parallel and not in series, the newer, stronger battery will charge the older, weaker one if its voltage drops quicker.  Overall, your capacity will be bigger than if you throw away the old one and only use the new one, so there's no use doing that.  Your loads shouldn't notice any difference. 

I've been using a 550 Ah bank of Rolls Surrette batteries for five years, and added a second identical bank three years after I bought the first one.  These are the core of my off-grid house electrical system.  The older bank does tend to hold slightly less charge, and the newer one keeps it from draining as fast as it otherwise would.  These batteries are expected to last 15-20 years and I imagine I will probably add a third identical bank in the next few years and eventually start rotating them out as the first one nears its life expectancy.  Assuming of course we haven't converted to hydrogen or something by then.
May 7, 2014 09:29 pm
Re: Old and new batery with load !!

I know everybody say that it is not good to add new batery to an old batery bank

There's nothing wrong with that, my grandpa actually did the same thing.

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