daklein
New Member
- Joined
- May 8, 2020
- Messages
- 190
Wow, that was a big drop in the SOC estimation, from about 75 down to 20. Dropped into the battery protection mode and connected to the grid even though it was still on-peak hours. I just happened to notice looking at the monitoring. If the grid had not been available, it would have shut off the inverters, and then we would have noticed right away....
Cloudy winter solstice days, family all at home cooking on the electric range all day, HPWH, everyone's computer going, all the lights (I'm always having to turn lights back off....), all that's too much for empty batteries.
Folks with the DC solar trailers and sometimes poor condition batteries seem to get this often, but this is the first time I've had this occur that I know of. I believe mine was just sitting in Vegas for a year, float charging from solar, only a little low on water when I got it, and they've seemed to be in good condition so far.
SOC estimation for lead acid batteries is tricky, I'm not complaining, mostly just amused and offering commentary. I've seen jumps in the SOC before, just not to this degree.
There are two lithium battery banks that do most of the daily cycling, AC coupled behind the SI inverters to run the loads at night, if they get charged from solar. The FLA battery connected to the SI inverters mostly stays near zero current, the other batteries charge or discharge to keep the FLA near zero when possible, except when bigger loads first come on.
When it connects to the grid off-peak, if I know it's going to, but the FLA is still pretty full, I set it to just run the house loads without charging the FLA (set inverter current to .4A @240vAC. The other option which works sometimes is to let it go into silent mode which accomplishes the same thing. But often, it will get back up over 95% SOC and disconnect from grid before getting into silent mode, then goes back down to whatever I have the lower SOC set to 88-92 usually. I don't like cycling the FLA for no good reason, it wastes energy and takes away some battery life.
I imagine that my shenanigans with keeping the FLA batteries very often near zero current do not help the inverters' SOC estimation. Error in counting current will be a larger percentage of the relatively small currents. Maybe the voltage is also less representative of the battery state due to surface charge.
Cloudy winter solstice days, family all at home cooking on the electric range all day, HPWH, everyone's computer going, all the lights (I'm always having to turn lights back off....), all that's too much for empty batteries.
Folks with the DC solar trailers and sometimes poor condition batteries seem to get this often, but this is the first time I've had this occur that I know of. I believe mine was just sitting in Vegas for a year, float charging from solar, only a little low on water when I got it, and they've seemed to be in good condition so far.
SOC estimation for lead acid batteries is tricky, I'm not complaining, mostly just amused and offering commentary. I've seen jumps in the SOC before, just not to this degree.
There are two lithium battery banks that do most of the daily cycling, AC coupled behind the SI inverters to run the loads at night, if they get charged from solar. The FLA battery connected to the SI inverters mostly stays near zero current, the other batteries charge or discharge to keep the FLA near zero when possible, except when bigger loads first come on.
When it connects to the grid off-peak, if I know it's going to, but the FLA is still pretty full, I set it to just run the house loads without charging the FLA (set inverter current to .4A @240vAC. The other option which works sometimes is to let it go into silent mode which accomplishes the same thing. But often, it will get back up over 95% SOC and disconnect from grid before getting into silent mode, then goes back down to whatever I have the lower SOC set to 88-92 usually. I don't like cycling the FLA for no good reason, it wastes energy and takes away some battery life.
I imagine that my shenanigans with keeping the FLA batteries very often near zero current do not help the inverters' SOC estimation. Error in counting current will be a larger percentage of the relatively small currents. Maybe the voltage is also less representative of the battery state due to surface charge.
