Battery charge rate after sitting 6 months

[idroba]

I just hooked up the batteries in both my Caravel and Argosy after they have been sitting for 6 months with no charge or discharge. They are always left in the trailer but totally disconnected from everything. I use a pair of 6 volt golf cart batteries in both rigs. The Argosy has complete monitoring for charge/discharge rate with a shunt type digital ammeter which reads to tenths of an amp. The converter/charger is a PD 9245, 3 stage charger with charge wizard.


I turned on the converter/charger in the Argosy and it started charging at 3.2 amps. In 15 minutes it had dropped to 1.6 amps. I then lost interest as it is obvious by the very low recharge rate that there was virtually no self discharge in the 6 month of storage.

It is important to remember, these batteries were totally disconnected, with absolutely no load on them, and the tops are clean and dry. If you have any drain on them, no matter how small the results will be different. I use a Perko switch to disconnect my batteries, but the same thing is accomplished with removal of all connections to either the positive or negative side of the batteries.

In hot weather there may be more storage self discharge than I experience, I don't know. In hot weather mine are connected and in use for the camping season.

I have read statements that a flooded cell battery will self discharge at the rate of 10% a month or in 6 months would lose 60% of it's charge, and must be recharged periodically in storage. My experience over many years and many RV's is that this is just not true. This test just confirms my observations.

I thought I would post the information at any rate.

[r carl]

Did you happen to take a voltage reading before you charged them?

[idroba]

Yes, 12.7 volts, indicating full charge. But the very low charge current also shows that. If they are discharged as when boondocking, the PD converter/charger will sometimes go to a 40 + amp charge to begin with when first run on my generator or grid power.

[r carl]

I checked my 3 yr old batteries the other day and they read 12.7 volts so I figure im good for another year.

[Jammer]

The self-discharge rate increases with the age of the batteries.

It is also affected by plate design. Plates with higher cadmium content have higher self-discharge rates. The cadmium improves durability with repeated deep cycling.