Will older genny battery ruin new house batteries???

[Skuza]

I remember reading something that an older battery will suck juice from new ones and its a good idea to replace them all. The genny battery is circa '04 but still works fine. This year we replaced the house batteries (deep cycle wet cells) and am wondering if the genny battery is gonna affect the new ones now. Thoughts???

 

[Stray Cat]

Since the generator is on its own DC battery circuit, I say that it will not affect the new batteries....

 

[Presentation]

I’d love to hear what Frank has to say, I’m not an expert.

From what I understand, the ‘replace them both’ philosophy is correct when you are talking about two deep cycle batteries that are cross connected, usually in parallel.

When cross connected, a dead battery can drain a good battery. The reason this is a issue is when you bring a good battery all the way down to no change at all, being pulled down to 0% charge from the bad battery, this damages the good battery.

So you can damage your brand new battery with your old battery when cross connected.
That is why the ‘replace them both’ philosophy has merit.

The generator should have a starting battery. With proper care they can go 8 years or even a bit longer. Deep cycle batteries last about 4 to 6 years or about 150 deep cycles, whichever comes first.

A standard battery will be damaged if you bring it down to 0% charge. Even a deep cycle battery will last much longer if you don’t bring it all the way down to 0% remaining.
You can greatly reduce battery life by over charging, letting them get fully discharged or not keeping water in them.

Plus I agree with Jeff; if the battery is isolated, why change both?

 

[The Bill Collector]

In my boat the generator battery is isolated and therefor would not be able to pull down the others.....your configuration may vary.

 

[fwebster]

On the 400DA, the generator is isolated, completely separate from the other 2 banks...........so when you listen to your tunes all day and run the house batteries down, you can still crank the generator and re-charge.

You run into problems when you replace onlya portion of the batteries in a bank. The weaker battery causes the convertor to apply more voltage than needed to the entire bank and will cook a new battery to death.

 

[Skuza]

Thanks all!