Winter battery Voltage

[Jfrano]

So have new glass mat batteries on my R29, as of a few months ago, stored boat on trailer in NJ. When I visit, has been every weekend the batteries are at 12.7 v . I have pulled fuses for the constant draw items. Is that a normal drop from week to week?

 

[BB marine]

While charging the battery will show voltage has high has the charger output when fully charged which is 14.2 AGM and 14.7 for wet cell flooded. Once the charger is off and the battery is not receiving a charge or delivering a charge to a load. A fully charged battery in good condition should stay 12.6V to 12.9. Your batteries seem to be maintaining a charge right in range. I would say completely normal.

 

[Jfrano]

Yeah!!

What is the normal discharge over time if there is nothing demanding on the battery
Thanks
Joe

 

[knotflying]

It all depends on battery condition. A good battery without any draw in cold weather should hold its charge.

 

[Red Raven]

For new UB12100 AGM batteries that are installed in a lot of the Fluid Motion boats the self discharge rate is about 10% over three months at 25C.

Curt

 

[BB marine]

For new UB12100 AGM batteries that are installed in a lot of the Fluid Motion boats the self discharge rate is about 10% over three months at 25C.

Curt

Curt's posted spec is correct for all AGM batteries in good condition. Approximate of 1% to 3% self discharge a month = about 10% for 3 months. The percent of discharge can be deceiving if you are talking voltage drop. A fully charged battery that reads 12.7V (voltmeter) and has lost 10% of its charge over 3 months would read approximately 12.5V. , 50% discharge reads approximately 12.0V. I am posting this clarification only because Joe was asking about voltage drop in his first post and then discharge in his second question. A 10% drop in voltage would be close to 80% discharge.

 

[Red Raven]

For new UB12100 AGM batteries that are installed in a lot of the Fluid Motion boats the self discharge rate is about 10% over three months at 25C.

Curt

Curt's posted spec is correct for all AGM batteries in good condition. Approximate of 1% to 3% self discharge a month = about 10% for 3 months. The percent of discharge can be deceiving if you are talking voltage drop. A fully charged battery that reads 12.7V (voltmeter) and has lost 10% of its charge over 3 months would read approximately 12.5V. , 50% discharge reads approximately 12.0V. I am posting this clarification only because Joe was asking about voltage drop in his first post and then discharge in his second question. A 10% drop in voltage would be close to 80% discharge.

Good point Brian. Thanks for clarifying!

Curt