diy solar

diy solar

Heat pad install critique

robstrom

New Member
Joined
Nov 9, 2019
Messages
261
Location
50th parallel, rural canada
The build: 840 watts on roof, 40 amp epever scc, 206 Ah sok, unheated trailer unless I'm in it, winter Canada battery still never gets below about 12.8 volts.
Outside temp = inside unheated, only a question of how long it takes.
Typical winter outside in the -20 c + windchill. Let's just call it -40.
Pics added.
Insulation on floor, heat pad, aluminum heat sink.
The excess layers/ buildup from floor is to cover the heat pad wire loop from room temp.
Finally, the couple questions.
1. The +- 4" on wire end has no 'heat.
Anyone know, where is the 'built in' thermostat?
Does that insulation layer cause it to 'see' heat n shut off?
I'm less concerned about battery too warm, or even above 0 charging.
Should I trim the insulation back on the wire end?
2. I trust the SOK bms to guard my battery.
Does the temp sensor on MT50 control charging, or simply give me info?
Thinking, cut back insulation on the end n get sensor buried against battery.
Snap disc thermo will be added to pad circuit later.
Thoughts?
Offer advice, not more sh#t to buy.

Thanks.
 
Have you tried running the battery pad by itself to ensure it goes on and off at the right temperature and double check heat it puts off to ensure heating level is reasonable?
 
It does heat.
The kick in/out part isn't the question at hand.
I'm trying to determine the insulation of exposed part of pad, related to what that buried thermostat sees.
Sandwiching THAT part in insulation = a quiicker shutoff, defeating the point.
 
I think it would help if you marked up/drew on your image showing where you are placing probe and also explain the insulation between pad and battery, is the battery directly on the pad? Draw on image where pad is (guessing on top of bottom layer of foam)
 
1" insulation on floor, then heat pad, then aluminum plate, then battery.
Probe is on end of battery ( to the left) pretty much centred, then coverer with insulation.
Probe is isolated from ambient.
Built in thermostat, that is hard to determine.
 
That is my SOK.
The temp sensor via mt50 monitor isn't my main concern.
BMS will protect the battery.
Facon brand rv water tank heater has a built in thermostat wired to 12 volt panel, and it does heat.
I'm trying to determine where that thermostat is.
If exposed to room air, it will run all the time in the unheated space, wasting power.
If I cover in insulation, will turn off quickly.
If I bury it under insulation
 
It is a 20c thermal switch right near the wires on my 7-1/4x25 pad. Feel around for it.

My BMS the JBD SP04S034 from AliExpress has a heater port so I am planning to remove the thermostat and let the BMS control the pads or at least keep it exposed to atmosphere so it stays on all of the time.
 

Attachments

  • IMG_1390.JPG
    IMG_1390.JPG
    110.2 KB · Views: 13
From an Hvac perspective, I’d think a sealed insulated box, with air circulation around it with thermostat making certain the air around the battery is always above 5C should be plenty to keep battery from freezing. No need to have the heater in contact with the battery… seems silly to heat the battery, just keep the container from dropping below 5C…
 
Worked great through single digits with little to no insulation. The 25 watt heat pads got too hot for me to feel comfortable with them directly on the cells. Heating the air the whole battery is the same temp and I’m not cooking the bottom of the battery with the pad.
 

Attachments

  • E15C80AD-9C89-4685-8DED-2FF0BD86E518.jpeg
    E15C80AD-9C89-4685-8DED-2FF0BD86E518.jpeg
    122.2 KB · Views: 52
  • 83EBF82F-4E7A-463A-BE20-9F82A556DDA9.jpeg
    83EBF82F-4E7A-463A-BE20-9F82A556DDA9.jpeg
    167.5 KB · Views: 52
It is a 20c thermal switch right near the wires on my 7-1/4x25 pad. Feel around for it.

My BMS the JBD SP04S034 from AliExpress has a heater port so I am planning to remove the thermostat and let the BMS control the pads or at least keep it exposed to atmosphere so it stays on all of the time.
Hello - I have ordered 3 of these pads and wanted to ask if you have any updates on your install.

Thank you,
Danny
 
Hello - I have ordered 3 of these pads and wanted to ask if you have any updates on your install.

Thank you,
Danny
My pack using the 7 1/4x 25 pads is now complete. 2 Pads along the sides of the 8 280ah cells (2p4s). I exposed the thermal switches outside the enclosure. I have tested them and they seem to be working and heat up the cells from around 24 deg F to ~38 in about an hour. I ended up putting an override switch so BMS can only energize the heaters when I turn on the switch. The battery does not need to charge when I am not using the van but I want to be able to enable it to heat up on demand.
 
Back
Top