diy solar

diy solar

Separate system for Battery Heating pad

Yes. Although the main charging system should power the heaters even if the BMS blocks charging.
The problem with that is what if the main charging system is not producing power, because it is covered in snow, or it may heat the batteries at night (which you may or may not want). If you connected it to the same bus as the main SCC. I would not want the heaters to drain the batteries when I can't get to my cabin to clear the snow. For me this could be months.
Is the "load" port on SCC isolated from the battery, if so that would work. I guess you could put a blocking diode into the run from the SCC to the battery so the batteries can't power the heaters. I could just put a switch in to not heat the batteries when I am not there as well.

I am just working through the planning for my off grid cabin for this summer.
 
The problem with that is what if the main charging system is not producing power, because it is covered in snow, or it may heat the batteries at night (which you may or may not want). If you connected it to the same bus as the main SCC. I would not want the heaters to drain the batteries when I can't get to my cabin to clear the snow. For me this could be months.
Is the "load" port on SCC isolated from the battery, if so that would work. I guess you could put a blocking diode into the run from the SCC to the battery so the batteries can't power the heaters. I could just put a switch in to not heat the batteries when I am not there as well.

I am just working through the planning for my off grid cabin for this summer.
How would the 100w panel avoid the snow? I suppose it could be low enough to brush off without getting on the roof. Possibly a small generator or the vehicle battery could jump start the system if it was shut down on arrival.

I assume the heat would be wanted 24-7 and cycle with a thermostat.

Yes the battery could be drained while waiting for the snow to melt off the panels. If the battery gets low the BMS would cut power to the heaters. Snow would eventually melt. Solar would eventually heat the battery. Panels would then recharge the depleted battery.

Yes using the load portion of the CC could stop the heaters for semi low voltage before the BMS cuts power to the controller and everything else. If the CC does not have load control, a voltage sensing relay could shut down the heaters before the BMS cuts power to everything.
 
How would the 100w panel avoid the snow? I suppose it could be low enough to brush off without getting on the roof. Possibly a small generator or the vehicle battery could jump start the system if it was shut down on arrival.

I assume the heat would be wanted 24-7 and cycle with a thermostat.

Yes the battery could be drained while waiting for the snow to melt off the panels. If the battery gets low the BMS would cut power to the heaters. Snow would eventually melt. Solar would eventually heat the battery. Panels would then recharge the depleted battery.

Yes using the load portion of the CC could stop the heaters for semi low voltage before the BMS cuts power to the controller and everything else.
I would assume that both panels are covered, hence no need for heating. I would not want to walk in though the snow to find my batteries it a low state of charge because the panels have been covered for an expanded time period, that is what I was trying to avoid.

If the load port on the MPPT is battery isolated then that should work for me.
 
I was thinking as long as you batteries are low temp protected could you come up with a way to just run the heating pads off a 100 watt panel and a DC regulator? Once the batteries heatup they should start charging.
If this system was used here are my thoughts:
Yes the panel could heat the batteries till they are warm enough to charge but 1. Many of the protected batteries have reduced charging amps so that would be a consideration. 2. It could take many hours to warm up batteries enough to safely charge. During this delay lots of solar power can not be captured. 3. Batteries are dense and chill down slow and heat up slow. Often the watts needed to bring the heat up above 32 could be more then the watts needed to hold that temp as the heat content of the batteries is so high. 4. You could have 4 hours of good charging sun and need three of them to heat the batteries up. Not efficient.

In essence I believe a well insulated box with a low wattage heat pad system is the best ready to use system. Having low temp cut off batteries would be good for battery safety. Also adding a couple panels set up vertical to shed snow, on a separate charge controller would a a bit of gain bust you may want for heating pads.

If off grid and left vacant for long times. Turn off inverter and use battery voltage direct control thermostat for the pads. I made a simple system using snap action stats that use no watts and are very reliable.

Another factor is I monitored the battery box temp one day and found that while the batteries were charging on a nice sunny winter day the box temp rose 5 degrees f
Over 3 hours so the heat of charging added needed maintenance heat too.

Just my two cents:).
 
We close our cabin for the winter in November and open in April/May. I think I will just install a switch to turn off the heaters when I close for the winter, turn the inverter off and make sure the batteries are full. I was looking for a passive system that would not drain my batteries when I am away for 5 months. We are at high elevation and can get 6-10 feet of snow over the winter.
 
If this system was used here are my thoughts:
Yes the panel could heat the batteries till they are warm enough to charge but 1. Many of the protected batteries have reduced charging amps so that would be a consideration. 2. It could take many hours to warm up batteries enough to safely charge. During this delay lots of solar power can not be captured. 3. Batteries are dense and chill down slow and heat up slow. Often the watts needed to bring the heat up above 32 could be more then the watts needed to hold that temp as the heat content of the batteries is so high. 4. You could have 4 hours of good charging sun and need three of them to heat the batteries up. Not efficient.

In essence I believe a well insulated box with a low wattage heat pad system is the best ready to use system. Having low temp cut off batteries would be good for battery safety. Also adding a couple panels set up vertical to shed snow, on a separate charge controller would a a bit of gain bust you may want for heating pads.

If off grid and left vacant for long times. Turn off inverter and use battery voltage direct control thermostat for the pads. I made a simple system using snap action stats that use no watts and are very reliable.

Another factor is I monitored the battery box temp one day and found that while the batteries were charging on a nice sunny winter day the box temp rose 5 degrees f
Over 3 hours so the heat of charging added needed maintenance heat too.

Just my two cents:).
Follow up after reading other posts.
My system is a 300 ah with 280 max available. At 180 watts per day it would run 37 days before depleted. Two 200 watt vertical panels (even vertical will proved decent watts if not covered) that do not snow over would add mane more watts then needed to keep temp up. Less trouble and no snow issues.
Two more cents:)
 
Follow up after reading other posts.
My system is a 300 ah with 280 max available. At 180 watts per day it would run 37 days before depleted. Two 200 watt vertical panels (even vertical will proved decent watts if not covered) that do not snow over would add mane more watts then needed to keep temp up. Less trouble and no snow issues.
Two more cents:)
A bit more follow up.
We get 14-18 feet of snow each year. My friend and neighbor has one 445 watt vertical panel set up on the south face of his shed wired on a small charge controller. We have checked the input watts over a few days of bad weather very bad and that one panel put 400 watts per day into batteries with no snow removal. On sunny day it loaded 1400 watts. More then enough for 7 days of heater.

Shutting down inverter and setting the charge controller at about 80% SOC should keep the batteries active but safe in the storage range and ready fro spring activities.
 
This is a good idea but one must remember that during spring thaw there's the potential for a hole in the ground to fill with water. I have a water pressure tank installed much like you describe next to my well pump. In spring there can be a few inches of water in the pit. A lot depends on the drainage of where you dig.
I considered this idea too, then reconsidered based on the moisture/ground water issue. It ended up being way too expensive difficult for what it was worth. I bought trophy batteries with heaters and a new shed. Currently building a removable insulated shroud..
 
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