Redarc BMS 30, not for use in Cold temps

[luthj]

A quick and dirty fix would be to wire a DPDT switch to toggle between the remote temp sensor and a resistor. Size the resistor for approximately 1C. This will allow the unit to run in cold weather.

Lead acid batteries want higher charge voltages when cold, so the unit would be charging at a lower voltage than optimal, but it may not be that big a deal, assuming we aren't talking -20C or anything.

One method to get shore power charging from a DC-DC without that feature, is to take a bench power supply and wire it to the DC-DC input. Use a DPDT relay (120V coil) to switch to the supply when shore power is connected. Laptop power bricks can also work, but depending on the DC-DCs regulation and the size, they may cycle on/off, so investigation is warranted.


Another way to reduce component count is to install a shore power charger. This charger can be used while driving if you install a small inverter to power it from the vehicles 12V electrical system.

 

[aaen]

So just heard back from the engineering department at REDARC.

Apparently they are aware of this issue and have been selling all BMS 30 systems with the sensor 3 since Dec 2019. They will ship this sensor to replace my current sensor for the battery once they have them back in stock apparently which there currently are non in North America at the moment. No idea when they will restock, I've asked for them to just switch my entire unit out for a new one instead of just the sensor. Waiting to hear back, shouldn't be an issue with them, they have been great to deal with and work with as soon as they are made aware of the issue.

This sensor will allow charging of lead acid batteries down to -25degrees C. PDF attached.

 

[aaen]

Yup I hear ya

I had a victron before with 200w of solar, and a trickle charger to charge the battery when parked and the truck not in use. Switched it all out to this as I wanted the ability to see other options and well I like trying new things.

 

[shade]

Size the resistor for approximately 1C. This will allow the unit to run in cold weather.

Looks like that's pretty much what Redarc has done.

I'm still surprised someone didn't catch this problem before a NA roll out, but at least they're setting it right.

 

[aaen]

Australia sees cold temps in the mountains and snow, so no idea why this was even an issue. Regardless they have acknowledged it and a replacement is on the way.

This is common in this industry though, a lot of the high end stuff on the market is not designed to work in cold temps. I could go on about the high quality gear designed to work in arctic temps that fails to work below freezing due to poor soldering, badly sourced parts, or not actually testing the gear. My rig will see +40 degrees celsius to -40 degrees Celsius in a year, rare to see that cold but I have seen it colder. So I can see it being tough, but they should not be rating the gear to those temps when sticking it in a deep freeze to test it out.

 

[drrobinson]

I believe the issue with cold temp charging is highly dependent on battery chemistry. With regard to LifePO4
, charging at to low of a temperature can cause lithium plating and reduce the capacity and usable cycles of the battery. Each chemistry (and specific cell build) is different and I don’t know the specifics for Lead Acid or AGM. It’s chemistry folks, temperature effects reactions.

There really isn’t anything a charger manufacture can do except optimize for the specific battery’s chemistry to do the best possible charging the battery can handle.I don’t know if the Redarc unit is configurable enough to do this.

My understanding is that high quality battery management systems (BMS) inside the battery will monitor temperature and make adjustments to protect the cells if the external charger try’s to charge at parameters that will damage it. The catch is that not all BMS components are high quality.

That’s about the extent of my understanding on this that I gained when researching LIFePO4 batteries for my trailer build. I didn’t dig into the specifics of the other chemistries since I ruled them out for other reasons.



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[aaen]

Sadly Lithium/etc in cold temps are useless, they tend to not take a charge due to the internal BMS in the batteries as you have stated, they shut it down to protect the cells. One of the reasons why I have not upgraded to them here in Canada and I am steering clear of electric vehicles here until they come up with a decent solution to the problem and better range, although I am seeing a lot more charging stations pop up lately and with the release of Rivian and the ugly tesla truck, it could be very interesting in a few years time, but that is another thread.

I believe the issue with cold temp charging is highly dependent on battery chemistry. With regard to LifePO4
, charging at to low of a temperature can cause lithium plating and reduce the capacity and usable cycles of the battery. Each chemistry (and specific cell build) is different and I don’t know the specifics for Lead Acid or AGM. It’s chemistry folks, temperature effects reactions.

There really isn’t anything a charger manufacture can do except optimize for the specific battery’s chemistry to do the best possible charging the battery can handle.I don’t know if the Redarc unit is configurable enough to do this.

My understanding is that high quality battery management systems (BMS) inside the battery will monitor temperature and make adjustments to protect the cells if the external charger try’s to charge at parameters that will damage it. The catch is that not all BMS components are high quality.

That’s about the extent of my understanding on this that I gained when researching LIFePO4 batteries for my trailer build. I didn’t dig into the specifics of the other chemistries since I ruled them out for other reasons.



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[shade]

LFP batteries can discharge fine under 0C. Charging near or below 0C weather requires battery heating & insulation, but it can be done.

Lead based batteries can be charged below 0C. Imo, a charger with canned profiles and temp compensation should be capable of doing so, especially if it costs as much as the Redarc unit. I'm glad they're taking care of it, but it's still a blunder in my eyes.

 

[plh]

The renogy DC DC chargers are inexpensive and may do the trick.

They certainly do not get good reviews on Amazon.

 

[luthj]

They certainly do not get good reviews on Amazon.

Its a brand new product, so there have been some mild quality issues. For the price, its still a good deal I think.

 

[drrobinson]

I believe the EV manufactures are using battery heaters to compensate.

You can go this route for our purposes as well but it is expensive. Rumor is Battle Born is also working on an internal heating solution as well. Of course they are already quite expensive.

Hopefully as battery technology continues to develop we will have new battery chemistry that tolerates charging in cold weather better and still has the beneficial properties of LIFEPO4 ( light weight, rapid charging and ability to discharge to 0 SOC without damage)


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[john61ct]

I believe the EV manufactures are using battery heaters to compensate.

You can go this route for our purposes as well but it is expensive. Rumor is Battle Born is also working on an internal heating solution as well. Of course they are already quite expensive.

Hopefully as battery technology continues to develop we will have new battery chemistry that tolerates charging in cold weather better and still has the beneficial properties of LIFEPO4 ( light weight, rapid charging and ability to discharge to 0 SOC without damage)


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LTO fits all but the higher density, been around a while.

And self-heating LFP batteries are a thing, Renogy maybe?

but IMO better to DIY an insulated box and silicone heating pads, not expensive

 

[drrobinson]

LTO fits all but the higher density, been around a while.

And self-heating LFP batteries are a thing, Renogy maybe?

but IMO better to DIY an insulated box and silicone heating pads, not expensive

I haven’t done any research on sources for heating pads. Do you have a link?

I have seen BB has one for their batteries but they want $200+ for it


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[john61ct]

sellers from China on eBay will do a bunch of custom ones for you for under $100

 

[SquirrelZ]

Amazon has an assortment of heating pads. Here's one example- https://www.amazon.com/Facon-Holdin...rds=12v+battery+heater&qid=1579190520&sr=8-16

Search using "12 volt battery heater" or "12 v silicon heating pad."