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Old and new batteries together


TheOracle

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I had a dead battery in my one-year-old 100Ah 48V battery bank (4 batteries in series). I replaced the dead battery with a new one. I know it is not a good idea, but I preferred this option rather than to buy 4 new batteries. I do plan to add a battery balance wich will hopefully help to prolong the new batteries life.

My question is, where should I put the new battery to minimise the negative effects?  At the positive or negative terminal or in the middle.

It is an off-grid system with an Axpert 5Kva inverter.

Your suggestions will be appreciated

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1 hour ago, TheOracle said:

At the positive or negative terminal or in the middle.

Put it at the positive end. All those electrons have a way of drifting down to the negative side, so rather add the extra capacity at the top where there is more room... :-P

Okay, I'm kidding! That previous line was complete nonsense that I sucked from my left thumb. It doesn't matter where you put it, since it is a series string it makes no difference whatsoever. Put it somewhere where you'd remember, or mark it :-)

And you must get the balancer asap, because that battery is going to undercharge because of the lower internal resistance.

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6 minutes ago, plonkster said:

Put it at the positive end. All those electrons have a way of drifting down to the negative side, so rather add the extra capacity at the top where there is more room... :-P

I read this thought hmm never heard of this before but I would not argue to much with Plonky. Caught hook line and sinker.:lol:

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15 minutes ago, Chris Hobson said:

I read this thought hmm never heard of this before but I would not argue to much with Plonky. Caught hook line and sinker.:lol:

That said, have you ever noticed how the cell at the end of the battery seems to fail first? It's almost as if there is something to it...

My theory is that it has to do with temperature. In a car, the one right at the end is usually the one closest to the engine heat. Even in a home bank, chances are the one at the end is closest to the door or some such thing that means it sees temperature differently. That's my theory of course.

In this application, the chronic undercharging will kill it faster than anything else. It makes no difference where you put it :-)

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What I've done (manually) in the past, is in late absorb, put a 12V automotive lamp across the high battery (you're going to have 3 high cells though, I expect), that forces the voltage up on the low cell. Might see you through until you can get the balancer. But my case is a bit different with a 24V bank, I had the problem that while the charger was charging at 28.8V, instead of having two batteries at 14.4V, I had one at 13.8V and the other one at 15V. This is bad because the other one is now losing electrolyte. I eventually got my imbalance under control, just using this as an example. Check your batteries to make sure you don't have a high spot like that.

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Hi Guys, I am terribly sorry about the delay of the balancers.

They are nearly a month at customs, and I still battle to get them satisfied?

Wonder sometimes whether it is really possible :wub:

I have ordered another batch this morning and will fly it in with DHL, which should take about 3 days. Will keep you posted.

Sorry again Guys !!!!!

 

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