Renogy Smart Lithium Battery with Self-heating

SolarShed

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Hi,

Looking for experience and knowledge about using self-heating LiFeP batteries in the winter (for my shed).

Could somebody explain to me how well these self-heating batteries work in Canadian winters where temps can go as low as -35oC at night and stay below 0oC for months. My solar system is in my shed where its susceptible to the temperature changes.

I'm considering getting the new Renogy Smart Lithium 12V 100 amp battery with Self-heating.


MY concern is, if the temperatures being below 5oC for months at a time, would that mean the heater will be on for months?

How does this affect the longevity of the battery, and even safety?

Can I leave the charge controller connected throughout the winter months (like I did with my lead acid batter) and let the battery and charge controller figure stuff out?

It says it requires 4 amp of power to run the heaters. Being a 100 amp hr battery, and could be dark for upto 9 hrs a day in the winter months, would this even work?

thanks
 

Short_Shot

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The heater will not run 100% duty cycle if it's well insulated but yes, as long as it's cold it will try to warm itself up. I'm not sure about their units but the battery heaters I've seen switch on at a given temp and off at a given higher temp so they don't just run forever.

You will likely have success with an abundance of insulation around the batteries. However much you think you need and then add more. It's likely that they won't run the heater very often at all.

I'd contact them and see if they know anything about expected watt hour consumption over time but I'd suspect with insulation they won't run constantly.

You could consider Battleborn as well. They have heated models and supposedly great customer service.
 

SolarShed

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The heater will not run 100% duty cycle if it's well insulated but yes, as long as it's cold it will try to warm itself up. I'm not sure about their units but the battery heaters I've seen switch on at a given temp and off at a given higher temp so they don't just run forever.

You will likely have success with an abundance of insulation around the batteries. However much you think you need and then add more. It's likely that they won't run the heater very often at all.

I'd contact them and see if they know anything about expected watt hour consumption over time but I'd suspect with insulation they won't run constantly.

You could consider Battleborn as well. They have heated models and supposedly great customer service.
thanks for your reply! I found some information. Turns out, that it doesn't use the power from the battery to heat itself (or it shouldn't), it uses the power coming in from the terminals. This helps me in understanding that part.

I'm just curious if the self-heating batteries are more risker for fires. BB are great, but unfortunately I have all other Renogy smart products so I want to take advantage of this smart battery with my existing system.
 

Short_Shot

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thanks for your reply! I found some information. Turns out, that it doesn't use the power from the battery to heat itself (or it shouldn't), it uses the power coming in from the terminals. This helps me in understanding that part.

I'm just curious if the self-heating batteries are more risker for fires. BB are great, but unfortunately I have all other Renogy smart products so I want to take advantage of this smart battery with my existing system.
Huh.

Seems like it would be necessary at night to consume power from itself though. It's obvious that it would be "powered" while charging though.

The terminals ought to be connected to the battery too so I don't see how it could somehow not pull from the cells unless the bms they use has a special setup.
 

SolarShed

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I know, its kind of strange but it makes sense only because if you are constantly using battery power to run the heaters, you might get into a loop that it kills your battery sooner than later (short term and long term).

So its kind of like your in a cold night and the battery can't charge but can discharge (below -20, via the BMS) then morning light comes, the charge controller pumps voltage to the terminals but the BMS diverts it to the heaters and then when the internal temperature increases, heaters turn off and then directs power to cell.....
 

Short_Shot

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Well it wouldn't be constant. It should be on a thermostat, and could be disabled when not discharging but that would leave you with a cold battery if you suddenly need it.

That kind of makes sense but it sounds like you'll need it for discharging too sometimes.
 

SolarShed

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Well it wouldn't be constant. It should be on a thermostat, and could be disabled when not discharging but that would leave you with a cold battery if you suddenly need it.

That kind of makes sense but it sounds like you'll need it for discharging too sometimes.
you're right. Your only hope is that the battery doesn't reach -20 oC (or more) before the sun comes up because otherwise, it will shut off the discharging (including to the charge controller) and that is what is going to supply the power to run the heaters (via the solar panels). So, even with BMS and self-heating in cold, harsh environments, it could be a bit tricky.
 

Short_Shot

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I think you'll be OK with sufficient insulation though. Remember they self heat slightly too when charging and discharging so insulation helps even more.
 

Northernchateau

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Except the price is dramatically higher. Insanely higher.

Insulation and some temperature control method will do the job.
There is a trade off. The LTO will handle low temps without a heater. Depending on where you live and average winter temps that might be an advantage.
 

Short_Shot

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There is a trade off. The LTO will handle low temps without a heater. Depending on where you live and average winter temps that might be an advantage.
Well it would definitely have to be priced out.

I don't think lto needs a bms as a 6 cell pack is good for higher voltage than lfp, but it would also most likely be a diy project or it'll cost twice as much per battery.

And I believe op wants to avoid diy.

So for the extra cost you'd be able to build a whole shed, insulate it, and put up extra panels to offset the heater power needs.
 
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Northernchateau

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Well it would definitely have to be priced out.

I don't think lto needs a bms as a 6 cell pack is good for higher voltage than lfp, but it would also most likely be a diy project or it'll cost twice as much per battery.

And I believe op wants to avoid diy.

So for the extra cost you'd be able to build a whole shed, insulate it, and put up extra panels to offset the heater power needs.
Let me ask, how much power do you think you need?
I will say that Renogy is a nice piece but a DIY set-up at that price would yield more amp-hours.
 

Short_Shot

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Let me ask, how much power do you think you need?
I will say that Renogy is a nice piece but a DIY set-up at that price would yield more amp-hours.
I mean.


In my camper I need about 60ah per day of 12v at absolute worst case. Perhaps 40 if I'm conserving but I suspect you intended that for the OP.
 

Northernchateau

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I guess my only thing is, your in a camper and if the battery temp drops below 0c, LIFEPo4 batteres should not be charged.
Yes I see it has heaters but the power from the heater needs to come from somewhere. If tyhere is limited sunlight, what then?
I am thinking if I was not a DIY kind of person and lived in the great white north like you I would be looking at LTO batteries like below.
Yes they cost more but IMO they are better suited for the cold environment your talking about.
 

SolarShed

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thank you very much for your input. I just looked into the LTO battery, and that temperature discharge/charge temperature is pretty impressive! If I really was in a camper or something very remote, this would be a very very good choice. But, I decided to go with the Renogy Smart LiFePO4 with self heating, only because the application is for my shed, which is literally 30 ft from my home. For the winter, it basically runs some low wattage landscape/security lights, which is not detrimental. I paid $950 CAD for the battery.

It needs to pull a constant 4 amp for the heater to work, and only gets it from the terminals, not the cells. So, in my case, say it gets below 5 oC at night, there isn't enough sun to make the heater work. It won't be until the daytime that it will heat up and then charge. I have 2, 100 watt panels 12V connected in parallel with an MPPT. Amps can easily exceed 4 amp when the sun is on the panels in the summer.

Overnight, the low wattage lights can consume about 5 to 7% capacity, so even if it doesn't charge, I can probably get 100/7 = 14.2 or about 2 weeks without need a charge. I'm hoping that in those two weeks, there will be a day or two where the sun will shine to not only heat the battery, but then charge it. I admit, its going to be tricky between all this interplay of sun, temperature, charge state etc.

It would be interesting to see how this works. I can try to post later for an update.
 
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Short_Shot

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Well, its not constant as the heaters should be on a thermostat of some sort.

I wonder if two in parallel will allow one to discharge into the other's heater.
 

SolarShed

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Well, its not constant as the heaters should be on a thermostat of some sort.

I wonder if two in parallel will allow one to discharge into the other's heater.
yes, its thermostated like this:

Turns on when internal temperature drops below 5 oC
Turns off when internal temperature goes above 10 oC

But in order for the heater to work, it has to be constant power.

Just wondering if you can clarify that last comment: the two panels are connected to a fuse block, then the fuse block is connected to the MPPT.
 

SolarShed

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Its been getting cold here and I wanted to provide an update on how this self-heating battery works. Really cool actually!

My battery temperature went down to 3oC and there was a cold temperature warning in my app. When the sun hit my panels, my Renogy Rover was reporting around 5 amp was going to the battery, but the battery BMS only registered 1.1 amps in of charge, so where are these amps going? Over the course of 50 minutes, my battery temperature went from 3oC to 11oC and my Rover was ripping it at 10.5 amps at the battery terminals and the BMS was reporting around 5 charging amps or so. At this point the battery hit its charge limit of 13.8V but yet, the Rover was still reading 10.5 amps draw on the battery, soon as the temperature was over 10oC the low temp warning disappeared and the amps draw decreased to 0 amps, and now I have a fully charged battery at 11oC.

What was really interesting is that because the temperature was not below 0oC, it was still charging the battery slightly by using about 20% of the available amps to charge the cells (when I had 5 amps total), and the rest was going to the heater. Soon as the battery went past 5oC, it gave all the amps available to charge, and rest when to the heater. In my case at the peak sun (when all the sun hit the panels), I had 10.5 amps available from my panels, 4 amps was going to the heater and 6 was going to the battery cells.

I suspect that when the temperature goes below 0oC, it will only heat the battery and not charge the cells until it reaches 0oC and then it will throttle in the amps to the battery until it reach 5oC and then keep the heater on until it reaches 10oC.

Very cool product, Renogy nice! That really is a smart, self-heating battery.

Forgot to mention the ambient temperatures during this time was -3 to +2oC
 
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DRW

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So have you sorted out what happens when it's dark/no solar and your batteries get colder than -20c? In theory the Renogy shuts down. No discharge ! Nothing will work. I have a small RV that needs power to run my blower for the furnace. If the battery get's to -21, I have no heat. Can't start the generator as I need battery to start.
 
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