I went to the boat this weekend and topped off the batteries after they’ve been sitting for the first half of the winter. I watched my Victron SmartShunt log to see how much current they absorbed, and I was able to get a screenshot to demonstrate just how little self-discharge happens to AGM’s in cool weather.
Here’s what my SmartShunt saw:
Yes, that’s really one minute from initial connection to the point where charge current was well below one amp. That’s less than 0.05 amp hours absorbed into my 200+ AH house bank. Pretty clear evidence of the slow self-discharge of AGM’s.
The house bank is 2 Group 31 Deka Intimidator AGM’s, both new as of this July, with 105 AH each. There are two other batteries (engine and thruster) not monitored by the shunt but also charged by the same charger. Those are an Intimidator AGM Group 24 and 27, both from 2014. The charger (a Xantrex TrueCharge 2, 20 A) reverted to float within 5 minutes.
The house bank sat with the ground cables disconnected and no charging sources for 60 days in temperatures averaging probably around 40. The engine and thruster batteries sat for about a month since I did 20 hour load tests and recharged each of them.
Here’s what my SmartShunt saw:
Yes, that’s really one minute from initial connection to the point where charge current was well below one amp. That’s less than 0.05 amp hours absorbed into my 200+ AH house bank. Pretty clear evidence of the slow self-discharge of AGM’s.
The house bank is 2 Group 31 Deka Intimidator AGM’s, both new as of this July, with 105 AH each. There are two other batteries (engine and thruster) not monitored by the shunt but also charged by the same charger. Those are an Intimidator AGM Group 24 and 27, both from 2014. The charger (a Xantrex TrueCharge 2, 20 A) reverted to float within 5 minutes.
The house bank sat with the ground cables disconnected and no charging sources for 60 days in temperatures averaging probably around 40. The engine and thruster batteries sat for about a month since I did 20 hour load tests and recharged each of them.
