Tale of Two batteries

[Crewdog]

I know there's a good battery discussion going on, but wanted to post this experience.

I recently replaced my 2 house batteries.

I first did a load test, with batteries disconnected from circuit, with a Schumacher Load Tester:

Both house batteries came up with same reading.

After replacement, I took both batteries home and did a load test as follows:

Hooked up a 2 amp DC load and battery one ran for about 40 hours; i think you could say this battery was good for 80 amp hours, and maybe could have had some more serviceable life in the boat.

Battery two ran for 4 hours, so i think this was rated at 8 amp hours. this battery went to the recycler.

Now I know there's some IEEEs out there who can say what the effect of one bad or low battery in a parallel circuit will be.

 

[sheral]

Can you tell us what the make and composition is of your batteries? I only ask because living off grid, the options of batteries available to us are staggering, now more than ever. In addition, the companies and their track records of making quality batteries are numerous and varied... For example, many of the AGM's are made in the USA and many are made in China. I installed some AGM's made in China (only because the client wouldn't spend the money required to purchase the USA made AGM's) and they are beginning to fail after four years. While there are a multitude of reasons they could fail - AGM's like to get fully recharged much more often than lead acid - often USA made batteries just are better made and last longer.

 

[NorthernFocus]

...Now I know there's some IEEEs out there who can say what the effect of one bad or low battery in a parallel circuit will be.

Not an IEEE nor EE nor etc. But how a "bad" battery affects a parallel system depends on what is wrong with it. In your example, if the battery was maintaining voltage but had no capacity, it wasn't hurting the other battery. Simply wasn't doing any good. However, if one cell shorts in a parallel set, it can't maintain voltage and will drag the whole bank down.

By the way drawing a battery all the way down with a low amp load as you described is really bad for them.

 

[Crewdog]

Can you tell us what the make and composition is of your batteries?

Although there is great merit in replacing stock AGM batteries with flooded, i went ahead and just swapped out for exact replacement with the stock UB 121100 AGM battery.

By the way drawing a battery all the way down with a low amp load as you described is really bad for them.

Sorry, should have mentioned the batteries when tested on bench at home were only drawn down to 12 volts.

 

[Levitation]

12.0 is a deep discharge

http://www.energymatters.com.au/compone ... discharge/