BCM Community

Bus Discussion => Bus Topics ( click here for quick start! ) => Topic started by: Iver on October 13, 2009, 12:14:42 AM

Title: Battery storage and charging....
Post by: Iver on October 13, 2009, 12:14:42 AM
 I have a Xantrex inverter (Freedom Marine 3000w) with a link 1000 remote. I have the charger set so the lights indicate 50% charge remaining.
My house bank has 6-6v gel batteries.  The system works very well.  For storage purposes (3 or 4 months), what is best for the batteries:
      * Leave the charger on all the time.
or  * Charge the batteries and then turn the charger off until the lights indicate they need charging again.
or  * Disconnect the batteries from the system and monitor them until they need charging.
I must have some kind of drain on the batteries when they are sitting because they usually only last about a month unused before they indicate they need charging.
         Thanks,  Iver
Title: Re: Battery storage and charging....
Post by: gumpy on October 13, 2009, 04:10:58 AM
I leave mine on float when parked.
Title: Re: Battery storage and charging....
Post by: Tony LEE on October 13, 2009, 04:12:44 AM
Gel and AGM batteries have much lower self-discharge rates than normal flooded-cell batteries.

Said to be 1 to 3% per month at standard temperature.

I've read recommendations that for periods of up to 6 months, these batteries are better off being fully-charged with a quality 3-stage charger and then completely disconnected from all chargers and monitors.

Lots of phantom loads such as gas alarms and even some battery monitors and idle chargers can draw enough current to flatten even large batteries over a few weeks.
Leaving a charger connected all the time also runs the risk of it failing and perhaps either severely overcharging it or discharging the battery.
With the battery entirely disconnected, all you have to consider is the self discharge and that is quite predictable and easy to monitor once a month using a digital voltmeter.

Self-discharge varies with temperature - faster discharge in hot weather.