How to store LiFePO4 batt system for cold winter

[KanzKran]

My Galleria with 600 Ah LiFePO4 battery system by Lithionics and Xantrex needs to sit outside, covered in snow and shivering in the cold, in upstate NY winter weather. It gets to 0F now and again, and sometimes a bit lower, but that's short term.

The literature for the battery system has confusing requirements for storage, with screen shots of two of the documents below.

For storage is disuse up to 3 months, they recommend fully charging the system, then disconnecting the battery, which is easily done by de-energizing the solenoid that connects it to the house system, and holding the temperature to 14F or greater for up to 3 months, or -4F for up 1 month. For longer than 3 months, they recommend discharging to 50%, and holding the battery temp to 59F or higher (I'm only concerned about low temps) and cycling the battery every 6 months, which also doesn't concern me.

Most of what I've read online suggests lithium batts don't like being held for long periods at full charge. Maybe that applies to other chemistries, like my iPhone which even holds off charging to full based on a learned schedule. And then they recommend dropping SOC to 50%, but keeping it warm.

Keeping it that warm is probably doable, as I have a 1000W heater running under the jack knife sofa right now on a separate cord, on a thermostat. But I don't understand where the different temperatures comes from based on the length of time it will be idle, and why they would recommend it be fully charged for that.

Xantrex hasn't responded to an email, and I'll call them or Lithionics next. Coachmen doesn't respond. The owner's manual from Coachmen is a joke and doesn't address the Li3 system at all. The bundle of owner's manuals that came with the van include some from Xantrex, like the User Guide. I've gotten a lot more from the Xantrex and Lithionics sites. But nothing describing the entire system, including the 300W solar system and where it connects, and how to park it for the season under various conditions.

I just need to know how best to store it during the winter. Fully charged and let it get cold? 50% and keep it warm? Get a warming blanket for the battery? I don't want to remove that 160 lb box under the couch, that's for sure.

And more to the point, why the various temperature and charge state limitations or requirements, and the corresponding time limits? I keep searching the net, but I'm not finding much authoritative information.

Any thoughts?

[silasm]

I would double check with your battery manufacture those storage specs seems off.

I've got 800ah of Victron Lifepo4 the spec sheet has -45°C to +70°C as the storage temp and -20°C to +50°C for discharge. That's the same basic chemistry as yours. Also seems odd my recommended is 80% charge for storage for that chemistry. Mine does stay connected to the grid and has PV neither will charge when the battery terminal is under 5c.

They have a battery storage guide https://lithionicsbattery.com/wp-con...-Procedure.pdf looks like they recomdne 50% SOC for longer storage and have a wider temp range though still warmer that I would expect.

[KanzKran]

Originally Posted by silasm

They have a battery storage guide https://lithionicsbattery.com/wp-con...-Procedure.pdf looks like they recomdne 50% SOC for longer storage and have a wider temp range though still warmer that I would expect.

That's the weird part. 49F minimum recommended temperature at 50% SOC, for long term storage. But 100% charge and much lower minimum temps for shorter term storage, down to -4F for less than one month storage.

Since it's only the winter I'm concerned about, only the low temp limits are my concern. I have a 1000W heater running now, on a separate thermostat, and I ran the battery down to 50% by using the electric resistance elements in the Trumi Combi unit for an afternoon.

I guess if I knew why they recommend what they recommend, I'd feel better about it. That's a $15,000 battery in there (), and while it will probably outlive me, I don't want to shorten its life through poor practices. Just in case.

[KanzKran]

I got an email response from the manufacturer’s engineering department, which I wasn’t really expecting since those “contact us” forms are usually connected directly to the round file. But I digress . . .

He questioned the ‘duty cycle’ of the temperature changes, and specifically how often and for how long it goes below 14F. Since I had asked about maybe wrapping it in a heater blanket, he thought that would be ideal. Discharge to ~50% SOC, which it is, and keep it above 32F.

So I’m getting an 80W 72” long battery heating blanket which should just about cover the perimeter, and I’ll use a line voltage thermostat control with remote temperature probe layed on top, with a blanket over that just so the probe gets a decent reading far from the heat source. If necessary, I can also use a dimmer control to reduce the heat output of the blanket, as I’d rather it stay on nearly continuously (in cold weather, at least) rather than cycle a lot.

[johnfr80504]

One caution for you to keep in mind is that most LiPo batteries have a Battery Management System that draws some power out of the pack even if it is disconnected from the main load. I built an electric powered trike that uses LIPO batteries. I charged them at the start of winter and disconnected the load. Later in the winter I checked on them only to find that the pack was in a state of near total discharge. The BMS had depleted them. My solution was to put a timer on the charger that would charge them for 2 hours once per week. Mine are stored in a semi heated garage so never get below 32 deg. LIPO's don't like be charge when very cold. You might want to add a sensor that checks temperature too and not allow charging if below 32 deg.

[KanzKran]

Originally Posted by johnfr80504

LIPO's don't like be charge when very cold. You might want to add a sensor that checks temperature too and not allow charging if below 32 deg.

The BMS that’s separate but part of the system supposedly does not charge below 32F, nor above 110F (or somewhere around that). The built-in temperature sensor can only be accessed with the system on, but at least I can check it without shore power to monitor the state of charge and the temperature. I’ll have to keep an eye on that.

Thanks for the heads-up. Lithium is new to me, other than cel phones and computers, of course.

[KanzKran]

Added the 72” long heating blanket (Zerostart 2800071), wrapped around the perimeter which is also about 72”, and plugged it into a line voltage thermostat (Inkbird Wi-Fi ITC-308), with remote probe that’s sitting on top of the battery, about in the middle. It has wifi so I can monitor it from my phone. I also used a 300W plug-in lighting dimmer to cut the power down to about 40-50W. The battery is covered with a blanket, on top and all around.

It’s sitting at around 50F with outdoor temps in the 30-35F range. The charge controller says the internal temp is 8 degrees below what the thermostat shows, but that’s not surprising since the heat blanket is around the top half of the battery due to wiring and restraint interferences.

So far, so good.

[Idleup]

Thanks for all the reply's guys - On my system I use a 350 watt Xtreme Heater boat/ RV heater, its fully automatic (on and off) and 100% safe. It heats not only my battery compartment, but in fact the the whole coach.



I have the rear compartment vented to the coaches interior, our nights have been in the 20's and the heater has kept the compartment and coach in the around 38-40 degrees. You can see the heater at the top wall mounted in the image provided. This is a very compact heater and all T6-6061 aluminum so there is nothing flammable in the heater to fail.



Regards - Mike

[KanzKran]

Saw this youtube interview with the CEO of Battleborn, and it's extremely informative. So I copied it here for future use of others looking to understand the what, and more importantly to me, the why of the storage recommendations. Different manufacturer, but same chemistry, so I would think the general recommendations for storage would be valid across manufacturers.

Pilfered from this thread in General Discussion:

http://www.irv2.com/forums/f59/inter...ml#post5099671

https://www.youtube.com/watch?v=ywn-...ature=youtu.be

[KanzKran]

Screen shot of the free iPhone app they offer that's used to monitor and even control the heater.

Set temperature is 65°F, and battery temperature, measured at the top of the battery, in the middle of the 2 square feet of top, under a blanket, is holding at around 60°F after a mid-20's night. No other heat in the coach, and the battery is under the jack-knife couch, visible by just flipping up the skirt in the front or the back.

Since the measured temperature is 5° lower than the set point, the heating blanket is on continuously, which is what I want. When it warms up, it will cycle, but I can reduce the heat output through the dimmer to keep it running, which is keeping it at around 60W right now. Once it drops to the single digits, I'll probably have to increase the current to keep the battery temp up to where I want it, but at least over 32°F, per Lithionics' recommendation.

I played around with it while waiting at the airport last night, using an LTE connection. Pretty cool, though I'm rather easily impressed with stuff like this. If I turn the set point below the actual, the screen turns blue and it goes into cooling mode. There are two 5-15 receptacle outlets on it; one for a heater and the other for an A/C unit, with adjustable delay function for compressor protection. It supposedly will send an alert if/when an adjustable limit has been exceeded, or if the unit goes offline. I have to play with that some more, but so far, I'm rather impressed.

[KanzKran]

A photo of the wifi thermostat and dimmer. Just for completeness.

I’d probably get a better wifi signal if I hung it from something so it has a view through a window to the router, which is at the opposite end of the house and beyond a few walls, but the connection mostly works 98% of the time.

The temperature history on my iphone app, shown as 15 minute intervals, usually only has one or two 15 minute gaps throughout the course of a day, and it does its thing even if wifi goes out, so it’s good enough just to keep an eye on it.