Lithium battery warming idea

[Van_Dreams]

I store my DIY promaster outside at a storage facility without access to an AC source. The solar is generally able to keep up, even in winter. The only issue has been keeping the van interior at an acceptable temp. We have a propex heater, but it does sometimes fail. However, since I have remote access to most of the systems via internet, and since I live only about 2 mins away, I’m able to detect when this occurs and visit the van to troubleshoot. However, we are planning to go away next week and therefore won’t be available to visit the van is something goes wrong. So here’s what I came up with:

Purchasing the following items from amazon:

Smart plug https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1


Rechargeable handwarmer (2x) https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

The plan is to plug the warmers into the smart plug so that I can control everything remotely via Google Home.

I’m not certain yet how I am going to position the warmers to maximize the benefit while minimizing any potential hazard to the battery.

When I see the battery temp entering dangerous territory using my remote monitoring system, the idea is that I’ll be able to log into google home and activate the warmers.

Any thoughts?

[avanti]

I have been thinking through the same issue for a long time, since the issue you describe is the biggest downside to owning a LI battery system. We have a vacation home at the other side of the country, so the issue you face is a frequent one for us.

A few thoughts:
--Be sure to consider the implications of a major snowfall. If that happens, your solar will go to zero, possibly for a long time. Perhaps a small, vertically-mounted panel dedicated to storage might help.

--I wonder if your proposed system is needlessly elaborate. There are lots of thermostatically-controlled switches that can switch 120VAC. They are old-school and intended to turn on warning light in the window to let your neighbors know that your furnace has failed and your house is cold. One of these could automatically turn on the heaters, without you being in the loop.

--I am not sure that those hand warmers are the best choice as a heat source. They won't store very much power, and so won't last long. It also will be difficult to concentrate the heat where it is needed. Small 12VDC heat pads are readily available, and are likely a better choice all around.

BTW: Where are you getting 120VAC power for the smart plug? Are you running an inverter all the time? That would really cut into your power budget.

[Van_Dreams]

I run my inverter all the time, but I’m 24v and it’s a victron multiplus — I barely notice the inverter overhead.

And I just thought of something obvious — the the warmers will likely not turn themselves on when I remotely power up the smart outlet because I’m guessing the switch on them must be manually activated as is typical with a battery powered device like this. Once I get them from amazon, I’ll have to see whether I can modify the switching mechanism somehow. The reason I chose these over a thermostatically controlled blanket of some sort is that those blankets consume quite a bit of power. These, since they are usb, are limited to 5v, 2amps.

[Van_Dreams]

I did notice this on amazon which would allow me to do what I’m proposing without the inverter: https://www.amazon.com/gp/product/B0...3SRXOFFI&psc=1

However, I don’t have time to research the additional connectors and solder the whole thing together at the moment. Maybe in the future.

[GeorgeRa]

Are you solar panels can keep van worm inside? The Propex route would require much less electrical energy and I thought they very reliable.

[avanti]

Originally Posted by Van_Dreams

The reason I chose these over a thermostatically controlled blanket of some sort is that those blankets consume quite a bit of power. These, since they are usb, are limited to 5v, 2amps.

OK, but note that resistive electric heaters are 100% efficient; I.e., the electricity consumed exactly equals the heat generated. So, there is no free lunch. If the heating pads consume more power than you think you need, you can always wire them in series to reduce the current. Conversely, if your hand heaters are consuming tiny amounts of current, then they are also producing tiny amounts of heat.

IMO, you really should look for a pure 12VDC solution. The inverter overhead has got to be a significant part of your energy budget.

[Van_Dreams]

The solar is not adequate to run an electric heater — I don’t think anyone’s is. You’d need some serious KWh’s!


So here’s a rundown of my propex issues. First of all, we are limited by the capacity of our 5.9 gallon tank. I really don’t know how much continuous burn time that gives us on the propex, because I just installed the heater in September. To conserve gas, I tried setting the thermostat on the coldest setting, demarcated by a snowflake symbol. However, the unit has given us multiple supply faults on that setting. I think it’s only successfully turned itself on once at that setting. It now seems to be doing well at the next setting up (I think it turns on at 51 and off at 54 on that setting) but when we first installed it, we had some faults at that setting as well. I want to replace the regulator to see if that helps, but just haven’t gotten around to it — I do hear that the propex is very pressure-sensitive. Another potential problem with my particular install is that we put everything outside the van under the floor (it’s an HS2211) and we used the black rubber supply tubing rather than the recommended copper pipe. Not sure if that could affect our gas pressure. Oh, and the other serious issue with relying on the propex when we go away is that we don’t have a tank level sensor that is compatible with my remote system, so I can’t tell what the tank level is. Actually, I don’t have a reliable tank level sensor, period. I bought the manual Truma ultrasonic sensor, but it doesn’t seem to work, despite the cost and the good amazon reviews. One thing I have done right is that I’ve got a security camera trained on the thermostat, so I can at least see remotely whether I’ve got a red fault light.

[Van_Dreams]

Originally Posted by avanti

OK, but note that resistive electric heaters are 100% efficient; I.e., the electricity consumed exactly equals the heat generated. So, there is no free lunch. If the heating pads consume more power than you think you need, you can always wire them in series to reduce the current. Conversely, if your hand heaters are consuming tiny amounts of current, then they are also producing tiny amounts of heat.



IMO, you really should look for a pure 12VDC solution. The inverter overhead has got to be a significant part of your energy budget.

Which 12vdc units would you recommend?

[avanti]

Originally Posted by Van_Dreams

Which 12vdc units would you recommend?

I don't have lithium, so no direct experience.

Maybe something like this:

https://www.amazon.com/Signswise-200...117561&sr=8-34

[Van_Dreams]

Originally Posted by avanti

I don't have lithium, so no direct experience.



Maybe something like this:



https://www.amazon.com/Signswise-200...117561&sr=8-34

Thanks!! That looks very promising!

[GeorgeRa]

If solar is inadequate, LPG tank is too small, from where you going to get energy to keep your van above freezing? Seems as winterizing and removal of the batteries is your best option.

[avanti]

Originally Posted by GeorgeRa

If solar is inadequate, LPG tank is too small, from where you going to get energy to keep your van above freezing? Seems as winterizing and removal of the batteries is your best option.

Well, he really doesn't need to keep the van above freezing. He just needs to keep the lithium batteries above their safe storage temperature (which is probably about 0F), so it isn't crazy. Still not easy, though.

An interesting question would be how long the batteries can keep themselves warm enough by powering a heating pad. Time for some math...

[GeorgeRa]

Originally Posted by avanti

Well, he really doesn't need to keep the van above freezing. He just needs to keep the lithium batteries above their safe storage temperature (which is probably about 0F), so it isn't crazy. Still not easy, though.

An interesting question would be how long the batteries can keep themselves warm enough by powering a heating pad. Time for some math...

I agree that a 12V heating between batteries plus some insulation would be the best strategy just like Dave's ARV van.

[Van_Dreams]

Another interesting product. My battery sits on top of a long wooden raised platform inside my van. I couple place something like this heating cable under the wooden platform. https://smile.amazon.com/Easy-Heat-A...ustomerReviews

[avanti]

Originally Posted by Van_Dreams

Another interesting product. My battery sits on top of a long wooden raised platform inside my van. I couple place something like this heating cable under the wooden platform. https://smile.amazon.com/Easy-Heat-A...ustomerReviews

Yes, although wide physical contact with the battery is desirable, which is easier to achieve with the pads.

Also, note that those cables are 120VAC. 12VDC versions are available. I got some once on eBay to use in my 4-season conversion to protect a few peripheral areas.

[markopolo]

If there is a lead acid battery in the mix (chassis bat?) maintained by the same solar panels then it would be easy enough to disconnect / reconnect the lithiums from solar charging when just above 32F. A DC thermostat control plus a no or very low current rated at the appropriate continuous duty rating relay/solenoid/etc. would do it automatically. My thinking is that as long as a lead acid battery stays connected to the solar array it would be ok. Booster or Avanti or others here could comment on this if they think there would be a problem (surge). The 24V system might make that difficult if not impossible to source the parts though (maybe use the chassis battery to power the parts?). The parts are readily available on Amazon for 12V. I looked into this while planning a hybrid LFP/lead acid setup. This would give greater temperature headroom extending down to -4F for an RV in storage. I'm assuming that there's already a way to take the LFP batteries offline from other charging sources if say starting the engine when the LFP's are below 32F.

After that layer of fail safe protection, thermostatically controlled DC heating pads under insulation seems to be the best way to go.

[MsNomer]

Can you store the batteries in your house?

[Van_Dreams]

That would be a major pain to remove them. They are cells that I wired together, not drop ins, and they are situated pretty securely. I’d need to take the entire battery apart.

[Cokkie]

Originally Posted by Van_Dreams

I store my DIY promaster outside at a storage facility without access to an AC source. The solar is generally able to keep up, even in winter. The only issue has been keeping the van interior at an acceptable temp. We have a propex heater, but it does sometimes fail. However, since I have remote access to most of the systems via internet, and since I live only about 2 mins away, I’m able to detect when this occurs and visit the van to troubleshoot. However, we are planning to go away next week and therefore won’t be available to visit the van is something goes wrong. So here’s what I came up with:

Purchasing the following items from amazon:

Smart plug https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1


Rechargeable handwarmer (2x) https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

The plan is to plug the warmers into the smart plug so that I can control everything remotely via Google Home.

I’m not certain yet how I am going to position the warmers to maximize the benefit while minimizing any potential hazard to the battery.

When I see the battery temp entering dangerous territory using my remote monitoring system, the idea is that I’ll be able to log into google home and activate the warmers.

Any thoughts?

Lithium batteries can’t get cold? What happens when they do ? Do they come back? I vacation in Colorado and the Ben will sit for a few weeks in a cold garage is that bad?

[Van_Dreams]

You can’t charge them at 0 C or colder. Starting at -4 C, the cold may start to damage their chemistry permanently.