Heating multiple batteries in a sub zero environment…

[LithiumCanuck]

I am installing 3 rack mount batteries in the basement of my cabin where temperature gets below zero celcius a couple of months during winter. I am thinking of building an insulated shell to put on a server rack, install a heating element (not found yet) and use a ventilation conduit and a fan to make the air flow from the top rear to the bottom front… I only need to do it when I arrive (I am only there during weekends) so I will probably be using my generator to heat my energy storage…

Question is… What happens if one of the batteries hits working temperature before the others? (It most certainly happen)…. This one will start charging before the others are ready, unbalancing my system…. Should I wait till they are all ready before switching the breaker?

BTW, I am open to any suggestions to make this more efficient…

 

[Rednecktek]

Electric heat is always a pain to make. Have you thought about a diesel heater kit and ducting it in/out of the enclosure/basement? Yes it's another fuel but it gets a space hot right quick and you should be able to turn on all the batteries at the same time by the time you've got the groceries in the door.

Just a thought.

 

[rickst29]

Although your battery SOC will become unbalanced, the Voltage on their shared bus will be equal during charging. BMS of the "still too cold" battery pack (or two) will refuse to accept any charging current. Later, during discharge, the charged pack (at higher SOC and higher discharge voltage), will tend to be dragged down, providing nearly all of the current (at that higher discharge voltage) until discharge voltage of the 3 packs becomes close.

While the 2 "not-yet-charged" packs will be offering Voltage (into the loaded bus) at LOWER voltage than the bus itself, they will not be used. Later, when the bus is dragged down to Voltage value less than each battery, they will begin to provide current. While the bus Voltage is higher than 2 "not-yet-charged" packs, they are under a bit of pressure to become charged - but BMS is still rejecting that tendency.
- - -
The one big consideration is: Can your single "warmer" battery handle all of the load you will want to present (in discharging the battery with household loads at high wattage), or will that wattage create too much current for the first battery pack BMS to handle?

 

[LithiumCanuck]

Electric heat is always a pain to make. Have you thought about a diesel heater kit and ducting it in/out of the enclosure/basement? Yes it's another fuel but it gets a space hot right quick and you should be able to turn on all the batteries at the same time by the time you've got the groceries in the door.

Just a thought.

??? I didn’t even know this incredible piece of technology existed !!!

Placing an 8kw heater in front of the batteries would solve my batteries AND basement heating problem.

Ok. Any other suggestion before I place my order?

 

[LithiumCanuck]

Although your battery SOC will become unbalanced, the Voltage on their shared bus will be equal during charging. BMS of the "still too cold" battery pack (or two) will refuse to accept any charging current. Later, during discharge, the charged pack (at higher SOC and higher discharge voltage), will tend to be dragged down, providing nearly all of the current (at that higher discharge voltage) until discharge voltage of the 3 packs becomes close.

While the 2 "not-yet-charged" packs will be offering Voltage (into the loaded bus) at LOWER voltage than the bus itself, they will not be used. Later, when the bus is dragged down to Voltage value less than each battery, they will begin to provide current. While the bus Voltage is higher than 2 "not-yet-charged" packs, they are under a bit of pressure to become charged - but BMS is still rejecting that tendency.
- - -
The one big consideration is: Can your single "warmer" battery handle all of the load you will want to present (in discharging the battery with household loads at high wattage), or will that wattage create too much current for the first battery pack BMS to handle?

Thanks for your input, I appreciate.

As for the loads for a single battery, this should not be an issue. The fridge is already frozen and I only need power for my water pump, satellite com and a couple of led lights…. I don’t think I will be using my microwave, Vacuum cleaner or water heater before the place is warm.

 

[Rednecktek]

??? I didn’t even know this incredible piece of technology existed !!!

Placing an 8kw heater in front of the batteries would solve my batteries AND basement heating problem.

Ok. Any other suggestion before I place my order?

It's a 5kw, but in reality about 3.5Kw actual heat output (which is still over 200% of a full power electric heater), make sure you get the kit with the white tubing and the square LCD panel. Some of them come with a dial that's a PITA. You'll need a source of 12v so a step-down or small system to power it and diesel. When you go to do the ducting you either need to hunt down 3" dryer hose or get a rubber 3"-4" adapter for insulated 4" ductwork.

I have 2 in my cabin (~400sq ft) in the mountains and they full burn for a couple hours and then ramp down to idle for the rest of the week. Total consumption up there is about 6-8gal of diesel per week total. 10F outside, 68F inside, 1972 grade travel trailer insulation and single pane windows. If you get one, ping me and I'll send you my step-by-step cleaning & service manual as they tend to get gummed up after a week of low load. I like them so much I actually have 3 up there, 2 in service and a spare in a box. If one gets too gummed up, it's just a couple clips and a plug and swap out for the clean one, then you can service at leisure. They're cheap enough that having spares and spare parts (gaskets, glow plugs, CPU board) are totally worth it and I'm planning on adding one into my pump house so I can have water when it's right around freezing out.

 

[grizzzman]

There will be a lot of thermo mass to bring up to proper temp. Most batteries cells are packed together. This will slow bringing them up to temp in a timely and even manor. I would suggest keeping them at an even proper temperature.

 

[time2roll]

Is the cabin unattended? How is the fresh water plumbing protected from freezing? Is everything off in a storage mode?
Or is this while in use and need to heat the basement?

Otherwise yes if bringing the system up from a cold soak I would wait for all three batteries to be heated before enabling the system.

 

[400bird]

Do you reliably go there every weekend? Or do you know ahead of time?

I'd do something like a timer to get an electric battery heater started before you get on site. That way, when you roll through the door, you can check temps and just power the system right up.


Alternatively, why not leave the charge controller active and batteries warm 24/7?
Turn off the inverter when you leave so your only drain would be keeping the batteries at temp.

Do everything you can to insulate the rack and that will lower the heating required.

My battery is different than yours. But, at 30f overnight, it took less than 1 kw to keep the pack at 55f with 1"-2" of purple foam board insulation.

If you build an enclosure with good air sealing and 4" of insulation. I'd expect about the same or at least not drastically more energy use.

 

[LithiumCanuck]

Do you reliably go there every weekend? Or do you know ahead of time?

I'd do something like a timer to get an electric battery heater started before you get on site. That way, when you roll through the door, you can check temps and just power the system right up.


Alternatively, why not leave the charge controller active and batteries warm 24/7?
Turn off the inverter when you leave so your only drain would be keeping the batteries at temp.

Do everything you can to insulate the rack and that will lower the heating required.

My battery is different than yours. But, at 30f overnight, it took less than 1 kw to keep the pack at 55f with 1"-2" of purple foam board insulation.

If you build an enclosure with good air sealing and 4" of insulation. I'd expect about the same or at least not drastically more energy use.

I don’t go every weekend. I was thinking of keeping my satellite com active all the time and remotely start the heater a few hours before getting there….

 

[Bobert]

I am installing 3 rack mount batteries in the basement of my cabin where temperature gets below zero celcius a couple of months during winter. I am thinking of building an insulated shell to put on a server rack, install a heating element (not found yet) and use a ventilation conduit and a fan to make the air flow from the top rear to the bottom front… I only need to do it when I arrive (I am only there during weekends) so I will probably be using my generator to heat my energy storage…

Question is… What happens if one of the batteries hits working temperature before the others? (It most certainly happen)…. This one will start charging before the others are ready, unbalancing my system…. Should I wait till they are all ready before switching the breaker?

BTW, I am open to any suggestions to make this more efficient…

If you can find an upright frig or freezer the right size put your rack inside with a 60w incandescent light bulb rigged to turn on at or just above freezing. People keep paint from freezing at -40 around here using that method.

 

[LithiumCanuck]

If you can find an upright frig or freezer the right size put your rack inside with a 60w incandescent light bulb rigged to turn on at or just above freezing. People keep paint from freezing at -40 around here using that method.

Good idea. I will be looking for that.

 

[robstrom]

Canada winter, man.
Electric heater, batteries/ solar can't keep up.
I learned that LAST winter.
I now have the cheap chinese knockoff diesel heater ?

 

[Rednecktek]

I now have the cheap chinese knockoff diesel heater ?

I love those things! Do you have a teardown and cleaning guide? If not PM me and I'll send you the one I made for my camp.

 

[JaVid]

I would build a shell around the batteries and keep them heated - it won't take much energy to accomplish this and pretty easy to do with DC heating pads like they use for oil pans, etc. Only issue is making sure your solar doesn't have snow on it for long periods which would drain your battery eventually. You could mount some panels vertically and solve this issue...