Replace one Lead Acid battery in a 48V series set

[esal]

Hello,

I have 4 lead-acid batteries 200AH C20 connected in series for my 48V system. I have noticed that the voltage drops quickly until 44V which means one battery is failing. In fact I have measured each battery at that voltage and one of them shows 8 V which is less than the other 3.

I don't want to replace the whole bank, Can I just replace the defected one with another battery of same specs?

PS: I have tried equalizing the set several times to heal the faulty battery but it doesn't fully recover it.

Thanks

[SunEagle]

It can be done but the problem most people run into concerning existing battery banks is that just replacing a "bad" unit tends to hurt the new unit because the others are older and will shorten the life of the new one resulting in another bad unit