Two AGM in Parallel. One gets warm.

[allendick]

I have two GPL-8DL batteries in parallel.

They are of uncertain age, but I have used them for 4 years here in Mexico. They seem to have reasonable capacity still but I have not tried to measure.

The boat sits at a dock with the 110V charger on float, and a solar system on float as well. I believe the charger settings for both are correct.The Heart monitor shows 1.8 Amps charge at the moment. The positive lead goes off one and the negative off the other so that should not be a cause of imbalance.

My concern is that today I noticed one battery is noticably warm to the touch at 36ºC. The other is at 29ºC, and the inside of the hull where they sit is at 24ºC.

This implies to me that one battery is discharging through the other in a loop and that one battery is defective.

Am I correct in assuming it is time for new batteries?

If so, the easiest thing physically is to just replace them with similar new batteries, but I am wondering if I should do that, get golf cart batteries, or consider one of the newer sorts -- carbon foam or lithium?