Weird acting Ampere Time battery

[drracing07]

This is my first go with a LiFePO4 battery system on a solar site. I have 2 other sites supporting wireless equipment for remote connectivity, so everything is outdoors. The problem I'm running into is when the system gets full sun, or falls out of sun quickly, the batteries drop all voltage when they switch from charge to discharge, but then come right back. This is a problem since these sites are serving internet to customers. My other sites use AGM batteries, so no BMS. The batteries are in an insulated box and were fully charged before deployment. Is this common with LiFePO4 batteries, or just something specific to this BMS?
nominal 12v battery system and 24v solar panel.

System specs:
Victron 75/15 MPPT
2P Ampere Time 100ah with heater built in
2x 220w Newpowa solar panels in series.

 

[sunshine_eggo]

Sounds like:

1. bad connections
2. thin wiring
3. insufficient PV
4. insufficient battery
5. defective battery

 

[drracing07]

Sounds like:

1. bad connections
2. thin wiring
3. insufficient PV
4. insufficient battery
5. defective battery

Thanks. Wiring was tight but i'll reconnect everything and try again. Battery was anywhere between 13.4v to 13.01v and still doing it. When charging in full sun, it's pushing 13.5a, about 200w. wiring from charger to batteries is 12ga, about 6' of it. 4ga between the batteries. I have a case open with Ampere Time, they want me to do a full charge and drain.

I mainly wanted to see if anyone else has ever seen this happen, if it's a common thing for LiFePO4 batteries to do or not.

 

[sunshine_eggo]

You have confirmed #3.

You are not fully charging the battery.

If you're not charging to AT LEAST 13.8V and holding that for a couple hours, your battery is not getting fully charged.

If you have sized the system similar to your other stations, you may not have accounted for the heaters as a load. If they are in a cold environment and diverting incoming PV for heat, that's robbing you of your daily Wh capability for your non-heater loads.

 

[drracing07]

Would not setting a new battery at full charge cause the BMS to reset when switching from charge to discharge?

 

[sunshine_eggo]

Would not setting a new battery at full charge cause the BMS to reset when switching from charge to discharge?

Can you ask this a different way. I really don't follow you.

If your asking if your new battery is at full charge, it isn't. Hazmat rules require that batteries be shipped at 30% or lower. This is regularly violated, but most aren't over 50%.

I'm saying your battery is behaving like one that is never getting fully charged. Until you get your battery to 14.4V and hold there for about 30 minutes, it's not fully charged.

If it has a BMS that reports SoC, that BMS value will not be accurate until you attain the above voltage and duration.

 

[drracing07]

I just pulled the batteries back from the site to isolate and troubleshoot. I made a video to better show whats going on.

12/09/2022 | Synology Photos

photos.pinecone.fun

I'm using a 13.6v power supply with those clamps. Both batteries are doing the same thing.

 

[sunshine_eggo]

Whoa. That's not normal. I thought it was just dipping to 13.0V per your message above. That's nuts.

#5 Defective battery.

 

[eemarty]

What is the temperature of these batteries? Is it possible the heaters are coming on momentarily? I'd do a full charge, discharge and then charge again and see if it still does it but I agree that seems weird. Once it comes back on after the charger is disconnected, are you able to pull current from it or does it seem almost dead? Maybe some of the cells inside are dead.

 

[drracing07]

lol yeah, very weird thing happening here. both batteries are doing it too. I have an email back out to Ampere Time with the video, hopefully they have a recomendation that works. Currently have them on the supply charging up, but I already had them fully charged before i field deployed.

 

[drracing07]

What is the temperature of these batteries? Is it possible the heaters are coming on momentarily? I'd do a full charge, discharge and then charge again and see if it still does it but I agree that seems weird. Once it comes back on after the charger is disconnected, are you able to pull current from it or does it seem almost dead? Maybe some of the cells inside are dead.

That was my thought too, if the heater is kicking on or something weird. I did that test when they were still cold from the outside, trying to minimize environment variables from the field. Charging now, going to do the same test once warm to see what happens.

 

[Supervstech]

I just pulled the batteries back from the site to isolate and troubleshoot. I made a video to better show whats going on.

12/09/2022 | Synology Photos

photos.pinecone.fun

I'm using a 13.6v power supply with those clamps. Both batteries are doing the same thing.

13.6 really is t sufficient to achieve a full battery.
Ful ful is 14.4 it can achieve 100% SOC at 13.8V, but it can take WEEKS!
Will tests these batteries on his channel, and they hit 14.4, so you should too.

 

[eemarty]

There is probably some protection to keep the heaters from completely depleting the battery so it may cut it off if it's very cold and they are nearly dead. It's possible that the charger is just enough to run the heaters but not actually enough to warm them up above 50F so the cells can actually begin charging. So again, what temperature are these batteries?

 

[Bud Martin]

Does the charger show how much current is flowing into the battery during charging?
Can you measure it?

 

[drracing07]

They were just outside and air temp is about 40f, so it could be the heaters doing something weird.

 

[eemarty]

OK I just read the product description for these batteries. The heater comes on when attempting to charge them below 41F and it heats them without charging until they get to 50F and only then does it begin charging the cells! So if the heater can't achieve an internal temp of 50F they would never charge.

But it's possible that this design has a changeover time when the heaters and connected or disconnected from the circuit like you are observing.

 

[drracing07]

Does the charger show how much current is flowing into the battery during charging?
Can you measure it?

It's a noco battery charger, put it on the lithium function. Says it should be 15a, but it doesn't show an output. Sounds like it's choochin good though.

 

[drracing07]

OK I just read the product description for these batteries. The heater comes on when attempting to charge them below 41F and it heats them without charging until they get to 50F and only then does it begin charging the cells! So if the heater can't achieve an internal temp of 50F they would never charge.

But it's possible that this design has a changeover time when the heaters and connected or disconnected from the circuit like you are observing.

That's what I'm wondering. I'll try the test again when they warm up in the house, about 70f right now. The charger should help warm up the cells too.

 

[eemarty]

If there is a 1second changeover time or so, maybe a capacitor would be enough to keep your internet equipment on? But I agree, the first step would be to make sure you have enough solar in the winter to keep them heated above 50F and fully charge even on a cloudy day.

 

[Bud Martin]

It's a noco battery charger, put it on the lithium function. Says it should be 15a, but it doesn't show an output. Sounds like it's choochin good though.

It'll be good to verify using Clamp-on DC Amp meter.