Battery replacement

Stdyhand · November 2013

I have read several places not to add new batteries to an existing battery bank, at least if it is beyond 6 months or so. I've read to replace the whole battery bank. What do most do if a battery dies prematurely but the rest are still good?

The reason I ask is because I'm still tossing around the idea of a forklift battery. I know they weigh a lot, but that isn't really a problem for me. I have the means of moving it. The reason I was still considering it is because if I have to replace an entire bank just because one battery dies, why not just use a forklift battery and move the entire thing as one one unit?

If I can replace a dead cell in an existing bank when using individual batteries then I'll probably go with a complete battery bank. I was looking at a bank of 16 Surrette 6v, 400 Ah S530 for just shy of 6 grand. They have a warranty and its already complete so it saves me having to make the cables, but I'm not sure what to do because of the number of posts I've seen about not mixing new batteries with used ones.

If a battery was to die and I had to replace the bank, I'd be better off going with a forklift battery since it's cheaper.

Blackcherry04 · November 2013

Re: Battery replacement

Where I have replaced them they will equalize to the rest of the bank in a couple months ( capacity ). Batteries equalize ( Voltage ) to each other all the time with a stronger battery feeding into the other weaker ones, especially if the are in a parallel string. They will charge at different rate, but it's hardly noticeable.

Where it does becomes a issue, it's more economic, if you have a 6 year old bank are you going to add a $500 battery ?? Sometimes that is a hard call. The better you maintain a bank and keep it healthy, the less chance of it happening, it's usually a sulfate dendrite that shorts one out.

I have a customer with a bank of 8, GC-2's every year he replaces two and removes the 2 oldest, it's his thing, seems to work without issue. In a parallel bank the first two batteries on the positive end always carry more load, use more water and age faster.
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niel · November 2013

Re: Battery replacement

generally we've said within a year if not abused, but if a cell dies then what choice do you have if the other cells are all good and it's say 1.5yrs old? i'd just replace the one in that case. not ideal to replace all of them in an economic sense if one is willing to sacrifice a tad of capacity from a new one to match up with the other older batteries, but if all are a good portion through their lifespan you would certainly want to replace them all then. it is a bit of a rule of thumb, but is not something to be held to too rigidly and is a personal decision as to the best course for you to take and can be one of indecision at times. ask yourself if you know and feel all you other batteries are still in good shape and if you answer yes then ask yourself if you would feel a new one in the mix would lose a good deal of capacity if mixed in with the others. if not then replace that one with a new one and if it would lose too much in your opinion then replace them all.

you also need to consider the normal lifespan of the battery in question as a battery normally meant to exceed 10 years a 2 or 3 year span of time may be a good area to consider replacing only the bad cell or battery. i would consider the replacement for all more readilly in a 2 or 3 year timespan for a battery that has a typical lifespan of 3-5 years as this would be to replace in under 1 year for certain.

now can you say for instance replace a battery whose type lasts 3-5 years after 3 years? yes, but the new battery will be dragged down to the same capacity and abilities as the older ones that aren't in as good of shape. in cases like this it can be a waste of $ as other batteries can soon die off.

in blackcherries' example of someone swapping out the oldest every 2 years i don't think is a good idea to continue beyond a replacement or 2.

westbranch · November 2013

Re: Battery replacement

Don't forget to compare a larger capacity battery to this setup. 2 48 Volt batteries at 400 Ah is a lot of battery to manage monthly... you could get an ~ 800Ah battery and only have 8 cells to manage.

SolInvictus · November 2013

Re: Battery replacement

Stdyhand wrote: »

I have read several places not to add new batteries to an existing battery bank, at least if it is beyond 6 months or so. I've read to replace the whole battery bank.

That is bad advise. Adding a new battery degrades it to the level of the old batteries. It is worth it if there is a lot of life left in the old batteries. If the battery array is near the end of its life and you have parallel connections, just run it with one less battery provided their voltage remains high enough under load.

In my first battery array (4 series strings connected in parallel) I had one cell in an L-16 battery that always had a low specific gravity. It became worse over time no matter how many times I connected a charger to it to give it extra power. After 4 years, I replaced the 6V battery with a new one. For about a year I connected a parallel wire between the new battery and an adjacent one to ensure that the new battery would discharge into the old one at night. This kept the voltages on the batteries in the series string equal until the new battery degraded to the level of the older batteries. That battery array lasted 14 years.

Battery replacement

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