Xantrex C-60 issue.

littleharbor2

I'm basically bench testing a 12 volt 305 ah. LiFePo4  battery build I'm doing for a friend for his RV. I have the battery connected to an inverter for load and the C-60 for charging, It appears to start out working fine but then CC goes open circuit soon after connecting. This open circuit voltage causes the BMS to cut off charging due to an over voltage situation. Could there be an issue with the C-60?

Dave Angelini

Seems like there could be an issue. Really old electronics with a relay on the output going to a BMS...

I get that there is an allure to old things. I just received the commissioning flag from my Dads boat that was sunk in the Philippines in 1944.

OK, maybe put a 12v auto incandescent in parrallel. Bill would probably say that if he were not in
Taiwan

Hope you are out fishing in the Sea!

littleharbor2

Dave Angelini said:

Seems like there could be an issue. Really old electronics with a relay on the output going to a BMS...

I get that there is an allure to old things. I just received the commissioning flag from my Dads boat that was sunk in the Philippines in 1944.

OK, maybe put a 12v auto incandescent in parrallel. Bill would probably say that if he were not in
Taiwan

Hope you are out fishing in the Sea!

That's really cool Dave. Proudly displayed.
Thanks for the tip. I'll give it a try. 

BB.

What do you mean by the CC goes "open circuit"? Open circuit, to me, means the CC turns off (no current flow from array to battery bank).

It sounds like you are saying that the battery bus voltage climbs to (or towards) Voc-array (open circuit voltage of the array?). And at that point, the BMS shuts down to "save the Li Ion battery"....

The first thing I can think of--Is the C60 configured to 24 VDC battery bank while the Li Ion+BMS is 12 volts?

https://mwands.net/pdf_files/schneider/xantrex-c-series-manual.pdf

Another possible issue... Is the controller configured for Charge Controller or Diversion Controller? If a configuration jumper is in the wrong place or missing, that could cause configuration issues (see manual link above).

-Bill

littleharbor2

BB. said:

What do you mean by the CC goes "open circuit"? Open circuit, to me, means the CC turns off (no current flow from array to battery bank).

It sounds like you are saying that the battery bus voltage climbs to (or towards) Voc-array (open circuit voltage of the array?). And at that point, the BMS shuts down to "save the Li Ion battery"....

The first thing I can think of--Is the C60 configured to 24 VDC battery bank while the Li Ion+BMS is 12 volts?

https://mwands.net/pdf_files/schneider/xantrex-c-series-manual.pdf

Another possible issue... Is the controller configured for Charge Controller or Diversion Controller? If a configuration jumper is in the wrong place or missing, that could cause configuration issues (see manual link above).

-Bill

Hi Bill, Thanks for your reply. Pretty sure the BMS is shutting down for some reason and the controller, not seeing the battery shows the open circuit voltage of the PV array.  Interesting that you mention the CC being set for 24 volts. It was, but I corrected that. Otherwise, the controller is set up properly in charge mode.

BB.

Yep, if BMS Turns Off the battery--Then the C60 would probably hit Voc-array. C60s are PWM--Pulse Wave Modulation controllers... They simply turn on/off for multiple times per second. The battery bank is supposed to "buffer" the bus voltage.

We are back to which happened first--Chicken or the egg question. The BMS is supposed to monitor the battery (and higher end BMS will monitor each cell voltage)--And disconnect the battery if limits (over and under voltage, over current, out of range temperature, etc.) are exceeded.

A possible "hidden issue"--If the BMS measures per cell voltage, you could have an "over voltage cell" and still have a "nominal" 12 volt battery bus voltage. Read about "cell equalization" for this battery/BMS and see if there is an "approved procedure" to EQ the cells (discharge the high cell, charge up the low cells--This may take hours or longer--Assuming the cells are all OK).

Monitor the battery voltage during charging and see if he 12 volt bus voltage exceeds the BMS cutoff voltage.

Does the BMS have a diagnostic port that allows you to dump logs/parameters?

If you have a spare 12 volt car battery--Might be worth testing the C60 on that battery to figure out if the C60 or Battery are the "issue"...

-Bill

littleharbor2

The cell voltage differential is only 0.002 vdc, high to low, plus the cells are sitting at 3.447 average voltage so the over voltage issue looks to be elsewhere. I have the C-60 bulk voltage charge setting at 14.0 now, still wants to go open circuit. I am going to try a different cc in the morning.

BB.

The battery bus is going >15.xx volts because the BMS turned off the battery connection and the C60 output is either zero volts or 20.xx volts... At this point, the C60 may be working as expected (no battery, no regulated/stable 12 volt battery bus voltage)

The question is what is the battery bus voltage when the BMS has the battery "On", and the C60 is charging?

Is the battery bus going >15.xx volts then the BMS turns off... Or is the Battery bus at 13.8 volts then the BMS shuts down for no apparent reason (and battery bus goes Voc-array--Or zero to 20 volts).

-Bill

littleharbor2

I get the feeling we're going in circles here, (Chicken or Egg). Ha Ha. Well the CC-60 was set at 14 volts and showing full battery. The BMS alarm is showing overvoltage shutdown event. If the C-60 is going above 14 volts briefly, I haven't seen it. But of course it would only take a fraction of a second for the BMS to shut down.

I can't get to it today so, Sunday is the first time to swap out components and try again.

Bill, thanks for your help in staying  with me here. I'll definitely post what the problem is/was when I figure it out. 

BB.

Generally, the battery if charged to 80-90% full, should still have enough "buffer room" (I.e. 10% * 305 AH = 30 AH).

I don't know your charging current (or state of charge--These are just examples of how the math can work)--If you are charging (at the time the BMS goes "dark") a 90% full 305 AH battery), then the last 10% would take:

30.5 AH (last 10% to fill) / 10 AH = 3.05 Hours to take battery full and potentially trip the BMS
30.5 AH (last 10% to fill) / 60 Amps (C60 max current) = 1/2 hour for last 10% to trip BMS

If the battery is already 100% full, then (in theory) any charging current takes the battery over 100% and (sometime soon?) trip the BMS to shut down.

One thing you can try is to discharge the battery by 10-20% (i.e., 30-60 AH), then try charging with the C60 and see if the BMS still goes dark.

Or as Dave suggested--Put a good size 12 volt light bulb (or other load) on the battery to discharge a bit.

Note: You can have the light on while charging--But if the BMS shutdown and you have enough array current, you could over voltage the test load and burn out the bulb (or other loads).

If you do not have one, an AC+DC Current Clamp DMM (digital multi-meter) can help debugging--Such as measuring actual charging/discharging current. A couple of examples:

https://www.amazon.com/UNI-T-Digital-Handheld-Resistance-Capacitance/dp/B0188WD1NE (inexpensive, usually "good enough" for smaller solar systems)
https://www.amazon.com/Auto-Ranging-Resistance-Klein-Tools-CL800/dp/B019CY4FB4 (mid-price range. More features, larger Amp measurement capacity).

-Bill

littleharbor2

I do have a ac/dc clamp meter. The charging current was minimal, less than 5 amps.

I have swapped out the cc and inverter and for now it seems to be working correctly.