EG4 12V battery can't handle load but BMS shows is fine

[justinm001]

I have 2 400AH 12V EG4-LL batteries the original. Apparently the BMS firmware can't be updated and according to the BMStools I have D-4S400AH-P00-ZTR-V1.0 models. I've been having major issues where whenever I put any decent load my voltages drop and everything resets in my RV. In such I've updated everything to 1000a Lynx, 4/0 gauge wiring with wires going between each battery and from each battery lug to Lynx power in right infront of it.

Because of this issue I decided to rip everything out and test it. I plugged in my Quattro 5000/12v inverter directly into 1 battery with no fuse or anything else. I then attached a voltmeter to the battery lugs and applied a load. All while the battery was plugged into my laptop monitoring using the BMStools software.

Pulling just 103 watts from my inverter caused the voltage to drop to 10.3V at the lug and 10.39V according to the inverter. All while the BMS is showing 13.3V with a SOC of 96%

I then plugged in to shore and Absorption charging set in pumping 70W/4.9A into the batteries and reporting 14.27V on inverter and 14.22V on voltmeter at lug. BMS showing 13.310V with a 2.520A charge rate.

What should I do now? I'm about to do the same test with a small 24AH lithium battery I have to make certain its the EG4 battery. Also will do the same with the identical battery.

 

[jberger]

These are the used batteries you bought, correct?
(just trying to make sure we are still talking about the same units)
Did the original purchaser have the same or similar issue?
Any alarms or entries in the datalog tab?

Internally, these batteries have 16 cells, connected into 4 blocks representing the 4 cells shown on the BMS Display. So you can't always trust that blocks are internally balanced since there is just one sensor per (4).
I'd say you either have a bad BMS, a severely imbalanced cell pack or a bad individual cell that is held up by it's adjoining cellmates, but drops quickly under load.

You can pop the top and check the voltages on the individual cells.

What about the other battery? Same issue or is it just this one?

 

[justinm001]

These are the used batteries you bought, correct?
(just trying to make sure we are still talking about the same units)
Did the original purchaser have the same or similar issue?
Any alarms or entries in the datalog tab?

Internally, these batteries have 16 cells, connected into 4 blocks representing the 4 cells shown on the BMS Display. So you can't always trust that blocks are internally balanced since there is just one sensor per (4).
I'd say you either have a bad BMS, a severely imbalanced cell pack or a bad individual cell that is held up by it's adjoining cellmates, but drops quickly under load.

You can pop the top and check the voltages on the individual cells.

What about the other battery? Same issue or is it just this one?

Yes same used batteries. No clue if they had similar issues. I'll check the datalog tomorrow when its plugged in right now its showing 2035 date entries with ??? saying 48.520 total voltage.

I've had this setup almost a year now on my other RV and always had issues with voltage dropping under loads, it just seems to be worse. It's like some loads work better than others. I typically have 130w or so flat usage and can get 500-600w but when trying to turn on any heavy loads like an AC it fails. Even if I have a 1500w AC running on shore, if I disconnect it'll have this issue. When the voltage drops my whole 12V system shuts off and everything restarts so its a pain.

Same thing was happening when I turned off either one of the batteries or both were on. It's driving me crazy.

What's odd is most of the time it works fine and I can pull 1000w or so its really just with large loads or random. But for example even on 30 amp shore today I was running 1 AC unit (1500w) and after about 5 minutes the 12v power reset meaning the voltage dropped. Whenever voltage drops my firefly resets which turns off 12V power to the ac thermostats. I also have led lights flickering a bit, sometimes worse than others.

Monday I get my 48V batteries so will setup the new 48V quattro although I plan on running both systems, where 48v inverter feeds into 12V so gotta get this thing working.

I'm not sure if it's the batteries that can't handle the load or my inverter drawing too much power randomly, but if that's the case should I be seeing my batteries drop under 12V? I thought the BMS would handle this and shut down the batteries. Also I should be able to handle 400amps (2x200) comfortably I thought.

I did switch off my batteries and rewire everything in preparation for the 48V system this morning and noticed I was getting voltage on my Lynx even though the batteries are off. I'm thinking it's my Gen charge option (button that connects genny FLA to lithium to help start 20k genny) that isn't working right.... gotta test. I have an issue where my genny autostart controller shuts off as soon as it tries to start so that battery might be almost dead. I've had the coach a couple months and still going through everything

 

[justinm001]

upon further diagnosis I just found out my on/off switch on one battery is turning the lights on the front off but not turning off the terminals and I'm reading 13.5V with my battery tester. So I gotta have a bad BMS. Now should I try to warranty with signature solar or can I easily swap the BMS out with something else? I bought them used and I know the switch worked fine before so I'm certain its nothing with the seller.

That was with the #1 master battery above that I pulled and bench tested. #2 battery turns on/off fine but I haven't done much testing as its harder to get to and can barely reach the on/off switch.

I'm also thinking about if its easy enough to switch this to 48V and maybe do the same with #2. Then I could just get rid of my 12V inverter and add a 2nd 48V in split phase. Only my lights and water pump run 12V and I have a 12V genny battery so could use that hooked up to a 48V to 12V charger or 120v to 12V charger or maybe a couple little lithium batteries i have instead. Not sure what would work best

 

[justinm001]

Still having this issue with 12V. To recap I have shore to 48V quattro5000w then to 12V quattro5000w then to my panels. I have it setup to run 100amps from 48V inverter to 12V and 30amp shore to 48V. If I remove the 12V inverter and run from 48V to panels it works flawlessly. The 12V shouldn't be doing anything as the most amperage reported is 42amps and I have 100amps passthru before it even inverts. I have powerassist and UPS disabled on both inverters.

Trying to diag this. I have about 800w idle with a stereo and dehumidifier set to nonstop do it doesn't cycle. I'm then trying to run 3 AC units. Whats odd is this is happening like 5-10 minutes AFTER the 3rd compressor kicks in and not all the time... sometimes it'll work for 30 minutes and then will turn off. I just ran 2 ACs only and it happened.

What happens is I get low 12V error and VRM is showing my voltage is dropping below 7V. To test this more I currently have 2 CerboGx's one for 12V and another for 48V these are on their own separate battery so they don't turn off. I also have a 1000a jump pack hooked up to the 12V inverter with the 1 400ah EG4 battery so when it restarts it doesn't blow my BMS charging the capacitors. I know my 12V is dropping very low because all 12V is on a firefly system and it shuts off the lights and everything.

I'm assuming its not the battery as its doing it with the jump pack plugged in so can handle a huge rush. So that leaves the inverter or something on my 12V. My coach is complicated and its definitely possible there's something on 12V causing it.