Hello,
I have two dead 6v batteries (Crown CR220, similar to Trojan T105) after just 13 months of use. According to the dealer the problem lies in the charge characteristics that are pre-set in my mppt 100/50. Charge voltage appears to be too low to fully charge the batteries, which apparently kills them over time. The Victron app however, showed the batteries going in absorption and float phase just about every single day. Which did not make me suspect chronic undercharging.
Some specifics:
2x 6v batteries 220Ah wet cell deep discharge in series (12V system) - 550 Wp solar panels - victron mppt 100/50
Mean depth of discharge ~ 50Ah/night or ~20-30% - extreme dod ~50% maybe 10% of the time - Max load normal use at night 50% of time @~9A
Charge characteristics: bulk working up to 14,2V - absorption @13,8V (I’ve now learned this is too low for those type of battery) - float @13,8V Max charge from solar ~35A. Symptoms of failing batteries: they don’t hold their charge, solar just keeps on charging in bulk (Up to 300% of normal Ah) and batteries get super hot. Extreme Loss of electrolyte.
my questions: is there a chance I am just being told off by the dealer, are 6V batteries of this type in this setup just a bad idea, or is it definitely a user error and do I need to change settings for future similar batteries? Follow up: how come the charge program shows float charge if the batteries are not fully charged?
