Fitting heat pads to LIFEPO4 battery

OllieGBR

OllieGBR

VCDS user
T6 Guru
Has anyone attempted to fit heat pads to their Lithium battery?
I have a digital relay (thanks @Dellmassive) and three heat pads wired in parallel.
My question is, where best to place the pads? Under the battery or somehow attach them to the sides?
Here the pads are set under the battery - given it's in a plastic casing, not sure this is the most efficient method?
C033FDA3-E863-45E2-8167-5DAF4CC137C2.jpeg
 
OllieGBR said:
Has anyone attempted to fit heat pads to their Lithium battery?
I have a digital relay (thanks @Dellmassive) and three heat pads wired in parallel.
My question is, where best to place the pads? Under the battery or somehow attach them to the sides?
Here the pads are set under the battery - given it's in a plastic casing, not sure this is the most efficient method?
View attachment 99650
Click to expand...
I haven’t done this yet but I’m realising I’m going to have to, I never realised just how limiting it would be not being able to charge below zero. I went on a drive a couple of weeks back and the battery temperature hadn’t reached 5 degrees by the end of the 55 min journey, so received no charge. I’ve been on trips where the ambient temperature wasn’t above zero for 3-4 days but I’ve been able to charge previous AGM during short drives and even decent solar input for a few hours, none of which I’d get any more.

The examples I’ve seen have put the pads on the side, what power have you gone for?
 
B*ll*cks! You've just blown a hole in my dreams! I've longed to go to Scandinavia and tour in sub-zero temperatures (if we're ever allowed out again!) - I've seen photos on here of vans with snow up to the windows - but my twin LiFePos are not going to be a lot of use are they!!?? :oops::(
 
andys said:
I haven’t done this yet but I’m realising I’m going to have to, I never realised just how limiting it would be not being able to charge below zero. I went on a drive a couple of weeks back and the battery temperature hadn’t reached 5 degrees by the end of the 55 min journey, so received no charge. I’ve been on trips where the ambient temperature wasn’t above zero for 3-4 days but I’ve been able to charge previous AGM during short drives and even decent solar input for a few hours, none of which I’d get any more.

The examples I’ve seen have put the pads on the side, what power have you gone for?
Click to expand...

sorry for the daft question but why would it not charge at 5 degrees?

thanks.
 
ThreeBridgeT6 said:
B*ll*cks! You've just blown a hole in my dreams! I've longed to go to Scandinavia and tour in sub-zero temperatures (if we're ever allowed out again!) - I've seen photos on here of vans with snow up to the windows - but my twin LiFePos are not going to be a lot of use are they!!?? :oops::(
Click to expand...
Exactly, I’ve done that 3 times without having to think about it because I had AGMs. It seems to me that heat pads are going to be a necessity for lithium unless you only use your van in summer.
 
BigDean said:
sorry for the daft question but why would it not charge at 5 degrees?

thanks.
Click to expand...
Lithium batteries can be damaged if you try and charge them at sub zero temperature. The +5 degree C is a commonly used limit to allow a safety margin for a possible disparity between the core of the battery and an exterior temperature sensor.
 
andys said:
Lithium batteries can be damaged if you try and charge them at sub zero temperature. The +5 degree C is a commonly used limit to allow a safety margin for a possible disparity between the core of the battery and an exterior temperature sensor.
Click to expand...
Thanks for that.

So if the BMS does have low voltage cut off, or you use a sensor like the Victron connected to the BMV712 and a Battery Protect then it should work right down to zero?

I think the zero to 5 degrees is likely for me, but not below zero.

thanks.
 
BigDean said:
Thanks for that.

So if the BMS does have low voltage cut off, or you use a sensor like the Victron connected to the BMV712 and a Battery Protect then it should work right down to zero?

I think the zero to 5 degrees is likely for me, but not below zero.

thanks.
Click to expand...
It will work right down to whatever temperature you set it to cut off. 5 degrees is often used to allow for the fact that a temperature sensor stuck on the outside of the battery may have warmed uo to that, while the cells inside the battery may still be at or below zero.
 
The Victron Solar MPTT will get information from the BVM-712 temperature sensor and will not charge if the temperature is below 5C.
However, the DC-DC charger is not able to limit charging based on temperature, (an oversight from Victron IMHO).
Therefore, even if you not using you leisure battery in the winter and it's still connected when you go for a drive, it will charge when the alternator has put enough juice back into the starter battery. It's this I'm trying to avoid by adding heat pads to keep the battery above 5C.
I'm back in the garage after a ridiculously busy week at work, so let's see how I get on today:)

I agree, it's hassle I'd not considered - however the pro's of Lithium still outweigh the con's.
 
OllieGBR said:
The Victron Solar MPTT will get information from the BVM-712 temperature sensor and will not charge if the temperature is below 5C.
However, the DC-DC charger is not able to limit charging based on temperature, (an oversight from Victron IMHO).
Therefore, even if you not using you leisure battery in the winter and it's still connected when you go for a drive, it will charge when the alternator has put enough juice back into the starter battery. It's this I'm trying to avoid by adding heat pads to keep the battery above 5C.
I'm back in the garage after a ridiculously busy week at work, so let's see how I get on today:)

I agree, it's hassle I'd not considered - however the pro's of Lithium still outweigh the con's.
Click to expand...

This is making me rethink the whole design of my system (already on version 4). It seems crazy that I buy a battery with an internal BMS that has protection so it does not get charged below 0 degrees, but then the MPPT is going to stop at 5 degrees. That 0-5 degrees in the UK winter is a common temperature.
 
OllieGBR said:
The Victron Solar MPTT will get information from the BVM-712 temperature sensor and will not charge if the temperature is below 5C.
However, the DC-DC charger is not able to limit charging based on temperature, (an oversight from Victron IMHO).
Therefore, even if you not using you leisure battery in the winter and it's still connected when you go for a drive, it will charge when the alternator has put enough juice back into the starter battery. It's this I'm trying to avoid by adding heat pads to keep the battery above 5C.
I'm back in the garage after a ridiculously busy week at work, so let's see how I get on today:)

I agree, it's hassle I'd not considered - however the pro's of Lithium still outweigh the con's.
Click to expand...
I got round this by fitting a 3rd party temperature sensor and relay to control the Victron DC/DC charger so I have no problems with it charging when it shouldn’t, but I want to add heat pads to allow the battery to charge at low ambient temperatures.
 
BigDean said:
This is making me rethink the whole design of my system (already on version 4). It seems crazy that I buy a battery with an internal BMS that has protection so it does not get charged below 0 degrees, but then the MPPT is going to stop at 5 degrees. That 0-5 degrees in the UK winter is a common temperature.
Click to expand...
Many lithium batteries don’t have an internal low temp cutoff, hence needing the Victron setup (or similar) to protect it.
You can set the cutoff temp lower than 5 degrees if you want, but you may have missed my point that your temperature sensor stuck to the outside is likely to warm up before the internal temperature of the battery. Set your external sensor to click charging on at +1° and the cells inside may still be at -2°...
 
OllieGBR said:
Has anyone attempted to fit heat pads to their Lithium battery?
I have a digital relay (thanks @Dellmassive) and three heat pads wired in parallel.
My question is, where best to place the pads? Under the battery or somehow attach them to the sides?
Here the pads are set under the battery - given it's in a plastic casing, not sure this is the most efficient method?
View attachment 99650
Click to expand...
So what heat pads have you used? And what are you using to control their activation/deactivation?
 
andys said:
Just to clarify, the low voltage cutoff will not be affected by this, there is no problem USING the battery below zero, you just can’t charge it.
Click to expand...
...except that the ESR will be much higher at low temps so you shouldnt draw huge loads (coffee machines etc) whilst the battery is so cold.
 
Phil_G said:
...except that the ESR will be much higher at low temps so you shouldnt draw huge loads (coffee machines etc) whilst the battery is so cold.
Click to expand...
Reading it again I think he meant low temperature rather than low voltage anyway.
I've seen on Youtube mention of someone using 2 x 25W heat mats, one on each side, but those seem really tiny in size so might only heat up a very localised area. My battery is on its side so trying to decide whether to put one larger one underneath on the principal of heat rising, or one on top, one on bottom to try for a more even distribution of heat. I think I'll have to rethink my existing wiring though, don't like the idea of manually switching on the heat pads (and remembering to turn off). Might have to get another arduino in to manage all the relays that will be involved. Decisions, decisions. Life was so much easier with AGM and I have to admit I'm not yet totally convinced that the pros of lithium do outweigh the cons.
 
Insulation would help, pads directly attached to the battery with heatsink compound, then the whole caboosh encased in expanded polystyrene
 
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