justinm001
Solar Addict
- Joined
- Dec 18, 2022
- Messages
- 1,538
Yesterday I was out of town and my wife met me driving a Tesla model3 which we just bought the other day for an xmas present for my daughter so still getting used to it all. This was our first trip out of town and since my daughter goes to UK (Lexington, KY) and we're in Columbus, OH she'll be making about 200mile trips so hopefully the LR battery will work, although Cincy is right in the middle and I'm sure she can find 10 places to stop and charge. Anyways, She was in a hurry and charged up at the supercharger enough where it said she'd have enough range... apparently not. When she pulled up she had 60mi range and 88mi's away from home with the only supercharger 25miles the opposite direction. (tesla to j1772 adapter was in my mailbox so could only use Tesla chargers).
Bright Idea! Plug the car into the RV and I can run the 20kw genny and get the range. Problem is I rarely use the genny and last time i was low on fuel so it sucked all the fuel so takes a bunch of attempts to start... but I figured I had about 8kw of battery left in the RV and have 10kw inverters split phase so wouldn't be an issue to set the tesla to charge at 5kw and give an hour to get the genny to start (forgot to plug the battery charger back into the genny battery and could tell was a bit low).
Get it plugged in and was working but tripped the battery BMS. Figured I had a heater/water heater or air compressor running and went over the 10kw so turned all those off and reset the batteries. Happened again and I knew I wasn't near the limit. Got the genny working and reset everything then left it running which the batteries were at like 20%. Ran for a couple hours all good with the tesla set to 32a then for some reason the genny died and everything blew again, but all good since we had enough charge.
I realized earlier in the day when I removed my batteries I didn't put the cable between the batteries in the correct spot so the batteries weren't syncing. Fixed this.
Doing a postmortem this morning and determined the current being reported by my battery BMS is different than what my lynx was sometimes over 20 amps. When my BMS reported to Victron that it alarmed its showing my charge control limit was changed from 95 to 47.5 for some reason. Now this was when the batteries comm cable wasn't connected properly but that's why its 95 instead of 190.
Unfortunately this cerbogx is connected to the 48v batteries so when the bms blew it took out the logging so I can't see what happened exactly.
I'm wondering why the charge current limit changed from 95 to 47.5 and if that alarm that the BMS sends is actually the bms issue.
The batteries went into SCP alarm and not OCP, although it could have been OCP then when they restarted SCP from the inverters precharge having issues.
The max current I'm reporting is 172amps which the Tesla charger max's out at 32A/240v which computes to 147amps at 52V. Even with conversion losses and other items on I don't think I could have gotten above 172 amps to trip the 190amp limit. And certainly not the 200amp limit I should have with 2 batteries. 172 to 190 is 18amps and at 52v is 936w and at 200amps that's an additional 1456watts.
I'm also seeing a variation between the current reported by the inverters, the shunt and then the battery BMS which only other thing on the system is the MPPT which wasn't getting much of anything as it was gross out and most of this was in the evening. I'm not sure if its just because of reporting variances or cabling or what but I believe its all 4/0 gauge wiring which is overkill for 48V system. Could be 2/0 gauge though which would explain it. I'll have to check.
This is all assuming the Tesla charger actually limits its usage properly and there's not weird spikes. I was using a 50ft 50a extension cord too so maybe that could be the cause.
This is my first time with large 240V draw and able to properly test the system. Would love any input you have at all. In the future I plan on doing this often (especially when I can get my hands on a cybertruck as it'll be my toad) and having the generator autostart/stop when batteries are 20-40% which I'm thinking is more efficient than running it the entire time. Not just for fuel efficiency but also generator cooling as I removed a huge cooling system to capture space for my inverters and trying to get better cooling without taking up more space
Bright Idea! Plug the car into the RV and I can run the 20kw genny and get the range. Problem is I rarely use the genny and last time i was low on fuel so it sucked all the fuel so takes a bunch of attempts to start... but I figured I had about 8kw of battery left in the RV and have 10kw inverters split phase so wouldn't be an issue to set the tesla to charge at 5kw and give an hour to get the genny to start (forgot to plug the battery charger back into the genny battery and could tell was a bit low).
Get it plugged in and was working but tripped the battery BMS. Figured I had a heater/water heater or air compressor running and went over the 10kw so turned all those off and reset the batteries. Happened again and I knew I wasn't near the limit. Got the genny working and reset everything then left it running which the batteries were at like 20%. Ran for a couple hours all good with the tesla set to 32a then for some reason the genny died and everything blew again, but all good since we had enough charge.
I realized earlier in the day when I removed my batteries I didn't put the cable between the batteries in the correct spot so the batteries weren't syncing. Fixed this.
Doing a postmortem this morning and determined the current being reported by my battery BMS is different than what my lynx was sometimes over 20 amps. When my BMS reported to Victron that it alarmed its showing my charge control limit was changed from 95 to 47.5 for some reason. Now this was when the batteries comm cable wasn't connected properly but that's why its 95 instead of 190.
Unfortunately this cerbogx is connected to the 48v batteries so when the bms blew it took out the logging so I can't see what happened exactly.
I'm wondering why the charge current limit changed from 95 to 47.5 and if that alarm that the BMS sends is actually the bms issue.
The batteries went into SCP alarm and not OCP, although it could have been OCP then when they restarted SCP from the inverters precharge having issues.
The max current I'm reporting is 172amps which the Tesla charger max's out at 32A/240v which computes to 147amps at 52V. Even with conversion losses and other items on I don't think I could have gotten above 172 amps to trip the 190amp limit. And certainly not the 200amp limit I should have with 2 batteries. 172 to 190 is 18amps and at 52v is 936w and at 200amps that's an additional 1456watts.
I'm also seeing a variation between the current reported by the inverters, the shunt and then the battery BMS which only other thing on the system is the MPPT which wasn't getting much of anything as it was gross out and most of this was in the evening. I'm not sure if its just because of reporting variances or cabling or what but I believe its all 4/0 gauge wiring which is overkill for 48V system. Could be 2/0 gauge though which would explain it. I'll have to check.
This is all assuming the Tesla charger actually limits its usage properly and there's not weird spikes. I was using a 50ft 50a extension cord too so maybe that could be the cause.
This is my first time with large 240V draw and able to properly test the system. Would love any input you have at all. In the future I plan on doing this often (especially when I can get my hands on a cybertruck as it'll be my toad) and having the generator autostart/stop when batteries are 20-40% which I'm thinking is more efficient than running it the entire time. Not just for fuel efficiency but also generator cooling as I removed a huge cooling system to capture space for my inverters and trying to get better cooling without taking up more space
