HELP, off grid, discharged lithiums, huge storm coming

[ADDvanced]

Shed System: 2x200AH AmpereTime Lithiums, 3x 240W 24v solar panels, & a renogy rover 60A MPPT charger, small 400w inverter.

I am currently living in a shorty school bus with a smaller solar system (2x100w panels, 20a MPPT charger, 2x100Ah AGMs).

The weather has been bad, snowing for 3 days with no sun, so the power was running low on the bus. The shed was at 100% power, because i have 3 24v panels wired in series so even on overcast days, it manages to keep the power up to 100%. Anyway, last night, the bus was running low on power, so I turned the inverter on in the shed, and ran an extension cord to the bus, and put a battery charger on the bus batteries. This worked great.... except it was new years, celebrations were happening, and I passed out and left it plugged in.


Cue to this morning. Wifi is down (in the shed). Go out to the shed, and the Rover MPPT charger display is showing the batteries are at 0%, and are showing 5 volts. What do I do? I tried flipping it around, and putting a battery charger on the ampere time/lithium batteries to see if I could wake them up so the solar could start charging them, but I watched as the voltage went DOWN when I hooked up the charger

Okay, update, I disconnected the batteries from everything and checked with a meter, they are showing 11.4V.... where do I go from here? 11.4V should be high enough to charge, but the Renogy Rover was showing 0% SOC. ??? Very confused this system has been working fine for months.

 

[John Frum]

What is the voltage of the discharged batteries?
What is the temperature of the discharged batteries?
Does Amper time have a low temp cutoff?
Is there solar available?
Is the solar charge controller seeing enough voltage on the system side to attempt to charge?

 

[BentleyJ]

Sounds like the BMS did its job and disconnected, if that is the case the battery cells are most likely OK. Not sure what the BMS wake up procedure is on an Ampere Time brand battery.
As J F points out in the above post there may be more than one condition causing the BMS to disconnect or if its temp related vs. voltage related then the battery will not take a charge.

 

[John Frum]

Now that smart BMSs are available I would never purchase a battery that doesn't expose an interface to the BMS.

 

[B-Mod]

Charge them from your bus power?

 

[John Frum]

I tried flipping it around, and putting a battery charger on the ampere time/lithium batteries to see if I could wake them up so the solar could start charging them, but I watched as the voltage went DOWN when I hooked up the charger.

Hopefully that is because the discharge batteries were drawing current.

 

[ADDvanced]

Okay, update, I disconnected the batteries from everything and checked with a meter, they are showing 11.4V.... where do I go from here? 11.4V should be high enough to charge, but the Renogy Rover was showing 0% SOC. ??? Very confused this system has been working fine for months.

 

[ADDvanced]

I've been messing with it and it looks like the MPPT charger is trying to charge teh batteries, but then it kicks off almost immediately and I get an "over voltage" error. i've tried lowering the boost voltage in the settings to see if that would help, but so far no dice.

 

[ADDvanced]

Okay, another update. I hit up all the autoparts stores in the area, and walmart, and I only found one battery charger capable of charging lithium batteries, but it was only 3A. I figured it was better than nothing, so I bought that, turned the inverter on in the bus, plugged in an extension cord and left the 3A charger hooked up to the 2x200AH lithiums that were only reading 11.7V. When I turned the charger on, it the little display said "charging.... 2%" and I waited a few minutes, and it said 3%. I left it plugged in and charging for a few hours, went to check on it, and it said "Fully charged", which I knew was BS, there is no way a 3A charger can bring a 400AH battery bank to 100% charge in a few hours. I unplugged the charger, and the Rover MPPT charger was displaying the battery voltage as still just 11.7V. The 3A charger now will not charge these batteries, as it thinks they are fully charged.

IDK wtf to do. Would really appreciate any advice, it will just NOT STOP FUCKING SNOWING, I ahve not seen the sun in 5 days and the forecast is for another 5 days of snow.

 

[PreppenWolf]

If it were me, I'd put a dumb chargers on it. Just one of the regular car battery packs. Set it to 5A and let it run for 5-6hrs. Then check voltage and put the lithium charger on.

It could be the BMS is now locking out the batteries as well. If that's the cause, you'll need to cut the battery case open, remove the BMS, charge the cells, then reinstall the BMS.

 

[ADDvanced]

The only dumb chargers I can find are for lead acid, not lithium, and from what I understand the voltage wouldn't be high enough (12v instead of 14v). Am I incorrect on this? I have a dumb 6A charger somewhere.

Would using jumper cables from a car work instead? I know lithium can take a ton of power very quickly, so would that be better than using a charger?

 

[PreppenWolf]

I would not use jumper cables from another battery to this one because I'm not sure what the BMS can handle for amps. I would use the Lead Acid charger for 4-6hrs and track the voltage each hour. 6A should be perfectly fine. Any lead acid charger should put out at least 13.5V, ideally 14.2V-ish. Just like a car alternator.

 

[MisterSandals]

so I turned the inverter on in the shed, and ran an extension cord to the bus, and put a battery charger on the bus batteries.

This should work the other way around and get your shed batteries to at least 75% charged (maybe more).

The only dumb chargers I can find are for lead acid, not lithium, and from what I understand the voltage wouldn't be high enough (12v instead of 14v). Am I incorrect on this? I have a dumb 6A charger somewhere.

I don't understand what you are trying to do. You want most of your power in your bus where you are living, right?
If you don't NEED to use the shed, the batteries in your shed are fine sitting at 11.7V until the sun comes out again.

 

[PreppenWolf]

I think his issue is the system will not charge his batteries in that state.

 

[MisterSandals]

I think his issue is the system will not charge his batteries in that state.

Ok, but it sounds like OP charged the batteries with the little charger so they are awake. Hopefully the WiFi won't drag the battery down into disconnect state again.

I've been messing with it and it looks like the MPPT charger is trying to charge teh batteries, but then it kicks off almost immediately and I get an "over voltage" error. i've tried lowering the boost voltage in the settings to see if that would help, but so far no dice.

This is disturbing. I am wondering if the batteries were in a BMS protect state when the PV panels were powering the MPPT (this is usually bad). I suspect the "over voltage" error was because there was PV without an operable battery connected.

It sounds like the battery is awake now. I suspect if the MPPT is not damaged, it should charge tomorrow when the sun comes up. I'd make sure the MPPT is powered by the battery BEFORE connecting the PV tomorrow.

 

[kytoon]

This is better than Dallas. Where does it stand.

 

[Generis]

The snow should be over now, yeah. It's been a few days. Don't charge your lithium AmpereTimes if it's below 32, they don't usually have any low temp disconnect.

 

[ADDvanced]

Update: Just came back, and even in overcast conditions it's charging at 190watts, no errors, full power, all systems seem normal. WHEW.

Man that was annoying. I have some questions but I don't want to muddy the waters so I'm going to start a new thread.