Any one know the cutoff? I want to use it for a fan.

M4-AK

Yes... Thanks. What is the lowest safe voltage I can drain it to before I should recharge.

M4-AK

Geez, I figured someone knew.

M4-AK

From a chart in a Trace inverter owners manual, a 50% discharged battery will be 12.1 volts, at 77F, that has been at rest for 3 hours. You shouldn't drain it more than 50% or so on a regular basis if you want it to last. Since this voltage will vary with temperature and recent charge/discharge this may not be a good way to judge the condition. Better to use time, and discharge it less than 50% of its A-Hr capacity between chargings. The time you can run it is half the A-Hr capacity divided by the current draw of the fan. Be sure to use a special gel cell charger, since a regular charger will over charge a gel cell, and ruin it over time.

Thanks for the help. I am surprised at the half way cutoff. That seriously compromises usage of the battery capacity. Oh well.

Again thanks for the help.

M4-AK

The cut off was a surprise to me too..

This is one disadvantage of using lead-acid batteries.  When we designed our (don't laugh at me !) Y2K backup power plan,
we had to double the capacity of our lead-acid battery bank at the last second to allow for this.  I ended up with over 16 of the large L16 batteries in my basement !  (we had planned on charging w/ diesel generator during the day and using battery power via inverter at night)

It is not wise to deep discharge these batteries and it
is pretty important to use a good charger (with conditioning capabilities) when charging.