OTRwSolar
Solar Enthusiast
- Joined
- Apr 5, 2021
- Messages
- 208
I'm using a Daly Smart 4S 200a BMS with 4 3.2 200ah cells. With a 110a load the cells are producing 12.90v, however, the output of the BMS is only producing 12.15v.
That's a huge .75v drop. The 12.15v reading is being taken on the output of the BMS (same reading on both sides of the BMS black output cable---ruling out this cable as a problem). I've also checked the voltage on both sides of the BMS blue (input) battery (-) cable---both sides read 12.90v (while under >110a load)---ruling out a problem with that cable, too.
In any case, that's a huge voltage drop that's internal to the BMS itself. The BMS is not reporting any faults. It will support a 110a load for 30-60 minutes without an issue. Unfortunately, I can only discharge my cells to about 20-25% at 110a before the low voltage alarm on my inverter activates. If I use a >110a load, it alarms even earlier.
I know the mosfets will drop the voltage somewhat, but .75v seems a bit unreasonable. Is this the price we pay for a higher rated (>120a) BMS? I have a friend of mine with an off-the-shelf LifeBlue LifePo4 100ah battery that produces 100a at 12.65v.
That's a huge .75v drop. The 12.15v reading is being taken on the output of the BMS (same reading on both sides of the BMS black output cable---ruling out this cable as a problem). I've also checked the voltage on both sides of the BMS blue (input) battery (-) cable---both sides read 12.90v (while under >110a load)---ruling out a problem with that cable, too.
In any case, that's a huge voltage drop that's internal to the BMS itself. The BMS is not reporting any faults. It will support a 110a load for 30-60 minutes without an issue. Unfortunately, I can only discharge my cells to about 20-25% at 110a before the low voltage alarm on my inverter activates. If I use a >110a load, it alarms even earlier.
I know the mosfets will drop the voltage somewhat, but .75v seems a bit unreasonable. Is this the price we pay for a higher rated (>120a) BMS? I have a friend of mine with an off-the-shelf LifeBlue LifePo4 100ah battery that produces 100a at 12.65v.
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