SOK disappointment. Am I expecting too much?

[RonF]

I recently purchased 2x100ah SOK lithiums for my RV. I can get them charged up to 14+ volts but then will drop all the way to 0 within 3 days if my converter is disconnected. Our ambient temperature lately has been -10 degrees.

I would expect these batteries to see a minor voltage drop over time if they’re not being charged - but all the way to 0?
Also my SOK invoice says that they are heated. I would expect them to stop discharging at some point before hitting 0 when it’s this cold outside.

Am I thinking about this correctly? Are they defective?

 

[Steve_S]

If the Temp Sensors read 0C/32F they will cutoff and that will read as 0 Volts at the battery posts. That is typically for charging as LFP can continue to discharge to -20C/-4F. Charging can only happen above 0C and limitedly until 10C/50F before it can go to full 0.5C Charge Rate. Some factory default settings on prebuilts actually are "Terrible" and need to be properly set. Even BMS' shipped from factory that support a few chemistries often have horribly bad default settings, especially when it comes to Temperature settings.

 

[Alkaline]

I recently purchased 2x100ah SOK lithiums for my RV. I can get them charged up to 14+ volts but then will drop all the way to 0 within 3 days if my converter is disconnected. Our ambient temperature lately has been -10 degrees.

I would expect these batteries to see a minor voltage drop over time if they’re not being charged - but all the way to 0?
Also my SOK invoice says that they are heated. I would expect them to stop discharging at some point before hitting 0 when it’s this cold outside.

Am I thinking about this correctly? Are they defective?

perform a capacity test, you can buy a little tester like this form amazon:

https://www.amazon.com/150W-Electronic-Adjustment-Constant-Discharge/dp/B099226TLF

This one has v-sense wires so its quite accurate.

 

[Lt.Dan]

Drop to 0v or 0%? Please be specific, as they are very different.

 

[OzSolar]

I'd guess at two causes:

1- The new 48v SOK server rack batteries that I unpacked and turned on (reset) yesterday went back to sleep a few hours ago no activity. 24hrs? I think they are supposed to do that because the BMS by itself is a parasitic load that will drain the batteries after a few weeks. Could that be your issue?

2-How many hours (days?) can the battery last when it's running it's heater?

 

[Lt.Dan]

I think the heater is only programmed to come on during charging. If its sitting idle, there is no need for the heater.

 

[RonF]

Drop to 0v or 0%? Please be specific, as they are very different.

They both had dropped to 0.3v

 

[400bird]

You should contact the vendor. Did you purchase from Current Connected?

I'll bet it's either the BMS going to sleep or the heater running until something (BMC cell or pack voltage) hits a low voltage disconnect. -10 is pretty good and cold, it's probably burning a lot of energy to maintain temp at -10, if you don't have the batteries inside an enclosure.

 

[time2roll]

Bring it inside for a few days at 50+F and see how the test goes when above freezing.

 

[OzSolar]

I think the heater is only programmed to come on during charging. If its sitting idle, there is no need for the heater.

Quite possibly.

Still it would be very interesting to know the sequence of operations for the heater logic. If that battery was allowed to get to -10 you might possibly lose an entire day of solar charging while the heater tried to get it back up something above zero and be safe to charge and then that cycle would repeat the next day.

 

[kontiki]

Do you mean -10 C or -10 F? Do you have the heated or unheated SOK's? It looks like you said your invoice said heated. I too would call the manufacturer, or seller.

 

[RonF]

-10 F.

I got the following response from SOK:

. SOK battery failed rate is very very low, and 2 batteries failed at the same time, hard to believe.

 

[brum]

-10F/-23C is extremely low for LiFePO4. Even for heated batteries. Put some insulation sheets around them. This will greatly reduce the required energy to keep them warm. I would go with the thickest sheets that I could fit.

For such low temperatures, I suppose the heating would consume the full cell capacity for 3 days.

And LiFePO4 cells are usually not a good idea for sub-zero temperatures. Even the one with heating. Lead acid may be a better choice depending on the circumstances.

 

[johnice]

These should have the bluetooth connectivity yes? Once fully charged monitor them for a couple of days in the cold to determine
a) how much power the internal heater is using
b) what temperature does the internal heater keep them warmed up to

do some Ohms law math to guestimate how long the battery will last in those temps. My guess is either the heater isn't keeping up with the cold; or it's simply taking so much energy that they're dead after a couple days.

In freezing temps you need some sort of heater, and some sort of continual charging setup to power that heater.
-or-
I use an external heater and will disable the batteries when at full charge. They'll freeze but keep their charge; and they could stay that way for weeks. When I'm ready to use them I turn the batteries and heater back on; let them come up to temp; and go back to heating/charging and using as needed.

 

[Alkaline]

Note to future buyers named Ron: SOK no likey u...

 

[Alkaline]

All jokes aside, some people on the sprinter van forums are saying similar things, I think these things don't like the cold.

 

[Will Prowse]

Hi, my name is also Ron. I also got ripped off. SOK is Chinese company selling sub-standard stuff.

For the full story, check out this post:

Warning SOK Batteries and Current Connected

I bought $4,200 worth of SOK Lithium iron phospate batteries. That is four of the 12 volt 200 amp hour batteries. One had a bad cell and they all have defective BMS switchges. By going off at approx 28 volts instead of 29 volts, they cause spikes from the charge controller causing...

diysolarforum.com

 

[Browse]

BMS temp circuit may have been activated?

 

[Aly_Oops]

Battery heating pad will only work when your system is connected to shorepower, with an active charger online, like a multiplus. One could mod it to come on when off grid, but with 9 amps or so, you get reduced usage. SFK has a setup like that.

If sensor are not working or suspect, it is easy enough to open it and stick it into ice water cup.

BMS all defective (not working as expected?), yes, that is obvious. Why do they have a new BMS V3. Why do all the dealers (a few openly admitted there is an issue). Even their competitors know about it. Come on, be honest, fix the guys BMS, send him new ones. Don't be cheap.

I have one concern regarding those who are using 24 or more volts system. There are things that must be done right. Be careful mixing voltages otherwise you will fry. Hopefully this isn't the case here.

 

[42OhmsPA]

Lithium-ion batteries shouldn't discharge to 0 volts within 3 days, especially if they have a heating system.

Edit..
. They didn't discharge to 0v. The BMS more than likely went in to protection. OP stated they read 0.3v in a later post.