Battery Life

[dsherburn]

I returned from a trip and left my R23 on the trailer and left the refrigerator running. I had intended to go back out, empty the fridge and turn off the house batteries. However, something came up, I didn't get out there, and I completely drained the house batteries.

I know completely discharging is horrible for the batteries. Assuming they charge back up, how much damage to the battery life have I done? What is the best way to measure the (new) life or capacity of these batteries?

 

[knotflying]

You did not mention what type batteries. AGM can be abused more than flooded. Your charger may have a reconditioning/desulfation mode and this will clean the pads. How long will they last after a complete discharge has to do with age and what happened in the past so there is no exact formula. Best thing to do is charge them up and see how well they are holding the charge.

 

[BB marine]

I'm not sure of the right way to get an accurate count of " new life capacity". I can give an example of a similar incident battery discharge, different reason. I installed new AGM NorthStar batteries in the boat. A month after installing them I trailered the boat to Wisconsin. Before leaving I turned on the refrigerator and loaded it, but forgot to move the latch on the top of the door to hold the door closed. 5 hours later arriving at our destination I opened the pilot house door and saw that the refrigerator had unloaded and the door was open. The new Northstar house bank (2 batteries) I had the thruster Parallel switch off, had discharged, the analog volt meter showing 10.5 Volts which is more than 100% discharge. We launched and tied the boat to our slip, plugged in ,turned the charger on and began to recharge. after 15 months, so far no battery issues. I left the batteries hooked up, battery switches off this winter for 2 months. When I returned to the boat to check on it the house bank registered the same voltage as the engine and thruster that were not effected by the full discharge. 12.6 V slightly lower than full charge which should be expected after letting them sit for a couple months. My guess is if you charged them soon after the full discharge and did not give them time to sulfide the batteries should be ok. The best test is use them and see if you notice a difference in capacity.