Solar Battery Charge Issue

[KenS999]

Hello I have a 100W Renogy solar suitcase charging two AutoZone Duralast lead acid Marine deep cycle group 24 batteries. Batteries are 3 years old. Lately I have noticed the charging cycle time drastically increasing especially during the absorption phase of the charge cycle. Charging is now nearly twice as long as before. I have cleaned and inspected the terminals and connections. I have checked individual cell fluid levels as well. These batteries have been babied and never taken below 12.3V. My power usage requirements are minimal and have not increased.

I am wondering if these batteries are just getting long in the tooth as far as charging cycles? Would investing in a good specific gravity battery tester be the next step?

Thanks, Ken

[pianotuna]

1. fully charge the battery bank

2. equalize the battery bank

3. get a good temperature compensated hydrometer.

[KD4UPL]

Does your charge voltage ever get up to around 14.4 volts? If not, the batteries may be sulfated from being chronically under charged.
I agree, 100 Ah isn't much for 150 Ah of capacity. You ought to have at least a c/10 charge rage which would be 15 amps. That would take at least 250 watts of solar on a good day with a MPPT charge controller.

[3_tons]

KenS999 wrote:
Hello I have a 100W Renogy solar suitcase charging two AutoZone Duralast lead acid Marine deep cycle group 24 batteries. Batteries are 3 years old. Lately I have noticed the charging cycle time drastically increasing especially during the absorption phase of the charge cycle. Charging is now nearly twice as long as before. I have cleaned and inspected the terminals and connections. I have checked individual cell fluid levels as well. These batteries have been babied and never taken below 12.3V. My power usage requirements are minimal and have not increased.

I am wondering if these batteries are just getting long in the tooth as far as charging cycles? Would investing in a good specific gravity battery tester be the next step?

Thanks, Ken

Sounds like your batteries may need to be equalized (cells restored to equal) as the plates may be sulfated. This is normally done every month or two by a controlled over charge of about 14.8-15.1v for about 20 minutes or so which returns the sulfate back into it’s chemical soup...This should help to reduce the battery’s internal resistance...

3 tons

[Lwiddis]

I stay away from any battery that lists cold cranking amps (CCA) except to start my vehicles.

[Gdetrailer]

100W is not much more than 5A worth of charging, a trickle at best for maybe 4-5hrs peak in the summer.. Splitting that between two batteries and now you are talking about 2.5A each for a few hrs per day..

Are you using solar only?

Solar and shore power?

[Lwiddis]

Marine batteries are a compromise between true deep cycle batteries and starting batteries. Barely fair at both jobs...long slow discharges running RV lights, TVs etc...and short high energy for starting engines, and good at neither. Replace them with true deep cycle batteries