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Hedges

I See Electromagnetic Fields!
Joined
Mar 28, 2020
Messages
8,428
The BMS can't control anything (except disconnect) unless it has a data link to the inverter/charger. Some systems do.

But so far, all I've seen is temperature limit to cut out charge. Never a series of steps or a curve to adjust charge.
I think better EVs do regulate current (and temperature). From what I've seen of BMS and batteries for solar applications, I would say determine what max charge current is possible and set temperature limits accordingly. Then heat batteries to avoid disconnect if desired.
 

Stepandwolf

Solar Addict
Joined
Nov 14, 2020
Messages
635
The BMS can't control anything (except disconnect) unless it has a data link to the inverter/charger. Some systems do.

But so far, all I've seen is temperature limit to cut out charge. Never a series of steps or a curve to adjust charge.
I think better EVs do regulate current (and temperature). From what I've seen of BMS and batteries for solar applications, I would say determine what max charge current is possible and set temperature limits accordingly. Then heat batteries to avoid disconnect if desired.
Is there something in my configuration or diagram you are suggesting I change? You mentioned the Cerbo, but was that a firm suggestion and it would resolve these other issues you raise? Guys like the Explorist who uses every Victron part he can't doesn't have a Cerbo in any of his configs. I don't know if it does the same thing, or even close, but I know some people are using a pi for additional functionality. I do know the sales guy sold me a part that wasn't in my config that attaches to the inverter, something he said I had to have, VE dongle?

Seems a GX or pi could be added later. Thanks very much!
 

Hedges

I See Electromagnetic Fields!
Joined
Mar 28, 2020
Messages
8,428
I don't have experience with Victron, just going by what I have read here. I tried to find things in the Cerbo or other documents, but not sure.

If you have PV and charge controller capable of delivering more current than your battery is supposed to get (maybe 0.5C for lithium, 0.12C for FLA, 0.2C for some AGM), then I would suggest a mechanism to limit what is delivered so battery gets target current, but allow more when it is used by inverter. I think hybrids do that (because they see and control PV, battery, AC), Victron does that (with battery shunt and a controller), and AC coupled systems like Sunny Island do that.

If your PV is less than battery's max charge current, no problem.

If using lithium, I think low temperature charge disconnect should be set to a temperature higher than 0 degrees C, if available charge current is too high for zero degrees C. From that posting I linked, that appears to be about 0.1C. If battery is charged at too high a current while too cold, it reported plates out lithium causing permanent loss of capacity.

Besides a low-temperature cutout, you might heat/cool battery to where it should be. That avoids having the cutout occur. But even with LiFePO4 we now have a fire reported, so best to have batteries located where nothing would be lost except for them.

I think charge controllers with lithium setting ought to have a battery temperature sensor and ramp down current when too cold or too hot, but I haven't seen that feature offered.

"VE Dongle"


Appears to give Bluetooth monitoring, parameter setting, firmware updates. But I don't think it provides battery shunt monitoring together with the type of control I was talking about.
 

Stepandwolf

Solar Addict
Joined
Nov 14, 2020
Messages
635
I don't have experience with Victron, just going by what I have read here. I tried to find things in the Cerbo or other documents, but not sure.

If you have PV and charge controller capable of delivering more current than your battery is supposed to get (maybe 0.5C for lithium, 0.12C for FLA, 0.2C for some AGM), then I would suggest a mechanism to limit what is delivered so battery gets target current, but allow more when it is used by inverter. I think hybrids do that (because they see and control PV, battery, AC), Victron does that (with battery shunt and a controller), and AC coupled systems like Sunny Island do that.

If your PV is less than battery's max charge current, no problem.

If using lithium, I think low temperature charge disconnect should be set to a temperature higher than 0 degrees C, if available charge current is too high for zero degrees C. From that posting I linked, that appears to be about 0.1C. If battery is charged at too high a current while too cold, it reported plates out lithium causing permanent loss of capacity.

Besides a low-temperature cutout, you might heat/cool battery to where it should be. That avoids having the cutout occur. But even with LiFePO4 we now have a fire reported, so best to have batteries located where nothing would be lost except for them.

I think charge controllers with lithium setting ought to have a battery temperature sensor and ramp down current when too cold or too hot, but I haven't seen that feature offered.

"VE Dongle"


Appears to give Bluetooth monitoring, parameter setting, firmware updates. But I don't think it provides battery shunt monitoring together with the type of control I was talking about.
Yes. that is it. I have only seen it in one wiring diagram and even in that case, I was asked why it was in the diagram. I see lots of people using Victron Connect to "talk" to their devices, but I thought the devices already supported VE Direct without extras. I have since looked at some videos on this thing. Doesn't seem to give you any info you don't get from the shunt or charge controller. If I saw right, you might be able to use it to turn the inverter off and on as well as determine if it inverts or charges or both. It also has a way to limit incoming amperage, but didn't know that was a thing.

Thanks
 
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