AGM to lithium iron phosphate upgrade
- Thread starter Dh1288
- Start date
Thanks!
RCinFLA
Solar Wizard
- Joined
- Jun 21, 2020
- Messages
- 3,565
You did not mention LFP AH size. Keep maximum bulk current less then 0.5C.
If you plan on long term float I would drop float voltage to 26.8vdc.
LV cutoff is a bit more complicated then lead-acid batteries and you have to play with based on your battery size, cable size, maximum inverter loading, and BMS LV cutout.
Should strive to always have inverter shut down for low battery first, not the BMS. I would start with 23.2v to 24v. If inverter trips out on heavy loads back it down a little more. If you have to push inverter LV cutout too close to BMS LV cutout then you may need heavier (or shorter) battery cables.
That inverter probably has a LV cutoff timer which is time required to stay below LV cutoff voltage before it registers a LV cutoff. It can help a lot to prevent hair trigger trips on surge or a heavy load for moderate time that drags down voltage at inverter terminals. Set it for a few minutes. BMS likely also has a LV cutoff timer but you might not know what it is , have any control over it and pot luck on different BMS's.
Problem with too much battery cable resistance voltage drop is you can get a situation that you can't set inverter LV cutoff high enough to avoid inverter trip on heavy load and still have it high enough that the BMS LV cutout doesn't trip first when battery is drained down with light loads.
If you plan on long term float I would drop float voltage to 26.8vdc.
LV cutoff is a bit more complicated then lead-acid batteries and you have to play with based on your battery size, cable size, maximum inverter loading, and BMS LV cutout.
Should strive to always have inverter shut down for low battery first, not the BMS. I would start with 23.2v to 24v. If inverter trips out on heavy loads back it down a little more. If you have to push inverter LV cutout too close to BMS LV cutout then you may need heavier (or shorter) battery cables.
That inverter probably has a LV cutoff timer which is time required to stay below LV cutoff voltage before it registers a LV cutoff. It can help a lot to prevent hair trigger trips on surge or a heavy load for moderate time that drags down voltage at inverter terminals. Set it for a few minutes. BMS likely also has a LV cutoff timer but you might not know what it is , have any control over it and pot luck on different BMS's.
Problem with too much battery cable resistance voltage drop is you can get a situation that you can't set inverter LV cutoff high enough to avoid inverter trip on heavy load and still have it high enough that the BMS LV cutout doesn't trip first when battery is drained down with light loads.
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Thanks! I think it's 170 ah, the new power block by Big Battery.
