Heating pad use

[GyroGypsy]

I tried using Facon ST725 tank heating pads, mounted on .020 aluminum panels, tightly sandwiched between batteries. I found they were short-cycling, only remaining on for about a minute every ten minutes or longer, while the insulated battery compartment temperature dropped. I am using two Tesla S modules. I used heated antifreeze for first two years, but some particles appeared in the fluid and blocked the internal passages.

I read the thread here about cutting out the internal thermostat, and using a stand alone controller. I am worried about pad damage while peeling the adhesive backed pads from the aluminum. But that would be my next step.

Anybody else tried using tank heaters, or have other ideas?

 

[DougfromdaUP]

My friend ordered tank heating pads to keep his batteries warm, but they came damaged.

I helped him construct a heater using incandescent lamps this afternoon so he wouldn't lose any more free energy. We attached 4 candelabra bases to a piece of lumber, wired them up in parallel and screwed in 1 1/4 inch diameter 20 watt lamps. He's running them on a variable transformer I had until he gets a thermostat installed.

Over the years I've seen many remote installations that use lamps to keep electronics warm, so thought it would be an easy fix, and it was. If you reduce the voltage they last much, much longer.

 

[GyroGypsy]

Thanks Doug, but there is no room for your suggestion to be used in this application.

 

[Daddy Tanuki]

the particles you noticed in the antifreeze were probably silicates that formed from the heating and cooling cycles. one of the problems of not useing silicate free LLC. any chance you could chemically clean out the passages?

 

[GyroGypsy]

I could not find authoritative source for what chemicals should be used for flushing a Tesla battery so I did not pursue this.

I have good preliminary results using electric heating elements constructed of a standard RV tank heater, .020 aluminum sheet, and thermal conductive foam. A Bluetooth enabled, standalone power monitor provides tracking using a low cost digital thermostat with programmable hysteresis. I will publish those results shortly.

 

[Daddy Tanuki]

I could not find authoritative source for what chemicals should be used for flushing a Tesla battery so I did not pursue this.

I have good preliminary results using electric heating elements constructed of a standard RV tank heater, .020 aluminum sheet, and thermal conductive foam. A Bluetooth enabled, standalone power monitor provides tracking using a low cost digital thermostat with programmable hysteresis. I will publish those results shortly.

sounds similar to what I started with on my lithium bank. problem I had is all the controllers are 12 volt but the power source for everything is 54 volts. tried those little buck converters to drop 54 to 12, but they are all rated at 48 and burn up after a short period of time. so then i started using a bench top power supply to power only the digital thermostat and used a 12/48 volt relay (Coil was12 volt but contacts are rated at 48) same issue after a while the contacts welded shut due to the 54 volt of the bank. i ended up just wiring enough pads in series that the temp stays in the range i want without a controller.

 

[GyroGypsy]

I used a 24V digital thermostat, and wired two 12V heating pads in series. I found a 24V coil, 20 amp contacts, automotive relay and the coil is powered from the 24V Tesla battery through the thermostat.

I already use a 24 to 12V Victron converter which is pretty efficient, but wanted the heating system run from native 24V. This way if the voltage drops too much and triggers the BMS undervoltage limit to shed loads, it will still attempt to keep battery warm until no more battery is available.

 

[borednerds]

@GyroGypsy Have you come up with a satisfying solution? What sort of temps are you trying to combat?

What are the characteristics of your storage box? ,I too, have limited space and cannot go the heat lamp route. I've got 2 modules side by side in a 28x26x6" steel framed box, wrapped in 12g aluminum. The aluminum is "decoupled" from the steel via marine silicone ideally helping with thermal transfer, but mostly for water proofing.

This leaves room for ~1" of insulation above and below, 3/4 front and back, and 1/2 on the sides. My plan was to use 2 12v heaters in parallel like you have (or even run a 12v pad at pack voltage for more oomph), but if the pads can't keep up/ sink heat well in to the modules, maybe I'll have to go another route (was trying to avoid using the coolant lines).

Currently using foil-backed poly-iso foam board, but the idea occurred to me to wrap the cells in a plastic bag and fill the voids with spray foam for a more perfect insulation.