Renogy 50a dc-dc charger with mppt killing everything.

[Antmeister]

I cant seem to find a post on what im experiencing, so im going to post this.
Xmas eve I bought a renogy dc to dc charger with mppt 50a. I went to their website and downloaded a manual, because the one supplied is in chinese.
I copied the wiring diagram which is pretty simple, a 12 year old could do it.
It charges fine at 51a, but my issue is when i shut my engine off. My bms goes into melt down and all of a sudden I see this. My cells go outta wack for no apparent reason and everything shuts down. Its wired in correctly through my bms. when driving it charges nicely aswell. but shutting it down does something and i cant see what. Im thinking about adding a switch in the side of the alternator and shutting that off before i shut the engine off.
PLEASE NOTE, MY CELLS ARE ALL BALANCED BEFORE DRIVING AND SHUTTING MY ENGINE OFF.

 

[sunshine_eggo]

Induced current from EM field proximity?

Where are your BMS sensing wires (or the BMS itself) relative to conductors?

 

[Antmeister]

Induced current from EM field proximity?

Where are your BMS sensing wires (or the BMS itself) relative to conductors?

Thanks for the fast reply.
the wires are on the bms yes.
I had no need for the ignition switch because i have a non smart alternator.

 

[AntronX]

Verify cell voltages with multi meter.

 

[Antmeister]

Verify cell voltages with multi meter.

theyre exactly as it shows on the bms. then after about 2 minutes they correct fast and my power comes back on.
I thought it was my bms software causing the issue and i used other softwares and it still does it. Ive replaced my bms and it still does this.

 

[AntronX]

theyre exactly as it shows on the bms.

Then your cell 3 is fully discharged and cell 4 is over 100% charge. Balance your cells.

 

[Antmeister]

Then your cell 3 is fully discharged and cell 4 is over 100% charge. Balance your cells.

the cells are balanced fine, When I bought them a few months ago I checked them and they were all fine. Its only since I installed this Dc to Dc charger everythings going wrong. When my solar is chucking 25 amps in on a sunny day, nothing happens and my cells are fine.
What i dont get is why my bms is letting the cells go under and over charge. Its set to protect the cells and it doesnt seem like its doing its job.

 

[Antmeister]

ok here is a photo of my battery atm.
cell number 2 has always dragged a bit behind slightly, but when solar comes in it levels out with the rest.

 

[Partimewages]

How did you check the balance when new.

 

[sunshine_eggo]

ok here is a photo of my battery atm.
cell number 2 has always dragged a bit behind slightly, but when solar comes in it levels out with the rest.

that doesn't indicate balance. Voltage only represents balance above 3.4V and below 3.1V. In the operating range even a notably imbalanced battery will report near identical cell voltages.

 

[AntronX]

theyre exactly as it shows on the bms.

Did you verify each cell voltage with separate voltage tester? Its impossible for a cell to go 3.7V then back to 3.25V like nothing happened. You likely have problems with your BMS.

 

[Antmeister]

How did you check the balance when new.

A friend has all the equipment in his shop. so we charged them all up then put them together for a few days to equilize out. then tested the cell voltages and discharged and recharged them up to the rated 305a as advertised when they were bought. They also came from a good source here in the UK.

 

[Antmeister]

Did you verify each cell voltage with separate voltage tester? Its impossible for a cell to go 3.7V then back to 3.25V like nothing happened. You likely have problems with your BMS.

Ive used 2 different BMS and they do the same thing.

 

[AntronX]

Post pictures of your setup. Show how your BMS and DC-DC are wired.

 

[Antmeister]

Post pictures of your setup. Show how your BMS and DC-DC are wired.

Right, so I had a look at my dc to dc to make sure everything was tightened and not loose. It turns out my bvs wasnt in correctly. I may need a new one because it doesn't Click and hold ?‍.
Could the bvs be my issue?

 

[mikefitz]

Could the bvs be my issue

Depends where it was connected at the battery. The Renogy does not need the battery sence, bvs, to operate.
My guess is that you made a connection direct to the battery cells rather than the BMS output.

 

[Antmeister]

Depends where it was connected at the battery. The Renogy does not need the battery sence, bvs, to operate.
My guess is that you made a connection direct to the battery cells rather than the BMS output.

Everything goes to bms, NOT the battery. The only wire going to battery is the + positive, From dc to dc. The neg wire goes to the bms. I think I'm sending this back to amazon, it's clearly not working correctly and was warned by numerous Ppl to get the victron One.

 

[TacomaJoe]

BVS?

 

[Antmeister]

BVS?

Battery voltage Sensor

 

[Texas-Mark]

I think I'm sending this back to amazon, it's clearly not working correctly and was warned by numerous Ppl to get the victron One.

Not sure how this unit could be causing the symptoms you are seeing. You are getting a cell OV when your battery is only at 13.1V. You say the cells are balanced, but the second picture shows the pack voltage at only 12.98v. IMO you need to top balance the cells.