Eco Battery BMS issue or is my controller dying?

[Bowhunt24]

Hi all, appreciate any insight here. Back in Sept I converted my 36v PDS with the Eco Battery 38v/105 kit. Install went great, fired right up and didn't have any issues until recently.

A couple weeks back I was headed home at around 26% battery life. While at cruising speed something tripped (assuming the BMS) cart died. Turned it off and back on (classic move)and it came back on again but at 6% batt life. I made it home..barely. Didn't think too much of it other than a random gremlin or something.

Now fast forward to today after several uses over the past couple weeks with no issues, it keeps tripping to the point where you can't drive the cart. When lightly pressing the accelerator you will here the solenoid engage and the cart will start moving, as soon as you press the accelerator any harder and draw more amps, it trips and cuts power. Until you let up on the accelerator and let the solenoid reset. Then you can accelerate again but same thing happens right away. Again, "it tripping" I'm assuming is the battery BMS acting faulty? From what I could see on the gauge, when the amp draw was around 30 -50 is when it would trip. If you continued to hold down the accelerator, it still showed about a 1-2 amp draw, then back to zero when letting the accelerator up.

The battery will show closer to 40v output when fully charged, so maybe the slightly higher voltage is cooking my solenoid or controller? I have a call with eco battery tomorrow to try and troubleshoot it, hopefully isolate if it's the battery or something else.

Maybe this is a sign I need to install my new navitas controller that's been sitting on my work bench :D

[augiedoggy]

Its sounds like how it would behave if the pack was almost dead and needs to be recharged .. Too bad you cant see whats going on with the cells state of charge. Or maybe you can? I thought I read the app is finally being rolled out for these.

[Pat911]

Yes, sounds like either a low SOC issue or a single low cell problem. Best thing to do is contact Eco directly. Their support is great.

[TheCartBoy]

Trying leaving it on the charger for a few hours, give the BMS some time to balance the cells. Just a guess that you may have a cell at lower voltage and this causes the BMS to go into protection mode.

[jasonojordan]

Agree with the above local gurus. This sounds like what my cart does when I am in my final 5% of SOC and hit mud or loose sawdust and pull voltage down lower than normal on my pack causing the bms to momentarily trip.

[augiedoggy]

Originally Posted by TheCartBoy

Trying leaving it on the charger for a few hours, give the BMS some time to balance the cells. Just a guess that you may have a cell at lower voltage and this causes the BMS to go into protection mode.

There would almost have to be something wrong for this to just happen after charging once the packs already been balanced but I agree thats what it seems like by the symptoms.. Do we know if the battery gauge that comes with these has to be cycled a few times to be reliable? The op did mention it dropped 10% just by turning it off and back on at one point?

Is it just doing this as the battery is closer to needing a recharge?

[TheCartBoy]

No idea how it's calculating the SOC. I believe Coulomb counting is the typical method, but maybe on a reset it looks at open circuit voltage of the cells and has a look up table to corelate voltage to SOC. Maybe it uses the lowest voltage cell to set the SOC.

[Volt_Ampere]

Voltage to SOC does not work at all for LiFePO4 cells. Coulomb counting is really the only way to do it and that is tricky because it depends on knowing when you have a full charge to start with at 100%.

[augiedoggy]

Originally Posted by Volt_Ampere

Voltage to SOC does not work at all for LiFePO4 cells. Coulomb counting is really the only way to do it and that is tricky because it depends on knowing when you have a full charge to start with at 100%.

Thats likely why the coulomb counter I just bought says to completely drain the battery prior to turning it on and charging.

[Bowhunt24]

Thanks everyone! Love this community, everyone has deep knowledge and is super helpful.

Couple quick updates...The problem seemed to have stopped after a fair amount of fussing around with on/off, tow switch, charging and unplugging, battery on then off, who knows what I did, but it's running normally now. I'm afraid to drive it too far away from my garage though, but seems to go under full load without tripping.

It's a gremlin.

Also, what is the acronym SOC? **EDIT: State of charge. Got it.**

Thanks again all! Calling Eco Batt today and all of this input will make the call so much easier. :)