LifePo4 vs winter

[wme]

Ya I know, I've already talked to my faire godmother. I love my new batteries. 500w of solar and 2ea 100ah LifePo4 batteries and my generator run time this last summer was 2, 15 min maintenance runs.
And now "Winter is Coming". All I want is a battery with LFP power and charging and LA winter storage capacity, thats not to much to ask is it?
My rv is outside in a no power storage yard, last year the low temp was -41 F. I have removed the LFP batteries and stored them in an attached garage. Thats what triggered this whine. On my rig removing the batteries is a PIA.
Self heating batteries sound OK till you realize there is a parasitic drain from various monitors and sensors, plus that the roof mounted panels were under 18" of snow fro 3 months last winter
Whine over and off soap box

 

[Tomthumb62]

Mount a 100w panel that’s angled to the sun so snow will melt off. It will help cover those small parasitic drains. Get a cheap PWM controller ($10) so you don’t need to wire it into your existing system except to the battery
Also, insulate the heck out of the battery compartment to reduce the need to heat.
Brush off the 18” of snow occasionally to help the roof panels recharge the battery from the heat function.
Build your own heating pads system (Will has a video on it) and set it to not turn the heat on until 20F and off at 35F but make sure your batteries have low temp cutoff protection.

 

[Bobert]

We routinely get -30 I didn’t remove mine just charged them up and disconnected them

 

[Solarcabin Channel]

I am curious as to how much drain the self heating batteries have in a cold climate if anyone knows?

I keep my batteries in the cabin for that reason.

Not much to suggest for fixes except as Tom suggested.

 

[timselectric]

I am curious as to how much drain the self heating batteries have in a cold climate if anyone knows?

I keep my batteries in the cabin for that reason.

Not much to suggest for fixes except as Tom suggested.

The heating is only active, while a charging source is available. They aren't powered by the battery.

 

[Solarcabin Channel]

The heating is only active, while a charging source is available. They aren't powered by the battery.

Ah! That makes sense.

Thanks!

 

[Solarcabin Channel]

The heating is only active, while a charging source is available. They aren't powered by the battery.

OK now clear this up for me please:

If the internal heater requires an outside power source what good would it be if temp drops below freezing at night when solar output is zero?

 

[timselectric]

OK now clear this up for me please:

If the internal heater requires an outside power source what good would it be if temp drops below freezing at night when solar output is zero?

It's not designed to keep the battery warm. Only to warm it up before charging.
Discharging in cold is not a problem. Charging is.

 

[Solarcabin Channel]

It's not designed to keep the battery warm. Only to warm it up before charging.
Discharging in cold is not a problem. Charging is.

That didn't really answer the question?

What power source is it using to warm it up if solar is not producing and you said it uses the outside power source?

"The heating is only active, while a charging source is available. They aren't powered by the battery."

 

[wme]

I have a 25w solar panel mounted inside on a south facing window, its for the engine starter battery (lead acid) and it works great
My batteries have cold charge cutoff.
What I can't find is an empirical statement for storage of LFP batteries at -40 degrees. Battery disconnected from all loads or charging. 100% charged, 70% charged, 50% charged, BMS connected, BMS disconnected, how cold is safe???

 

[Solarcabin Channel]

I have a 25w solar panel mounted inside on a south facing window, its for the engine starter battery (lead acid) and it works great
My batteries have cold charge cutoff.
What I can't find is an empirical statement for storage of LFP batteries at -40 degrees. Battery disconnected from all loads or charging. 100% charged, 70% charged, 50% charged, BMS connected, BMS disconnected, how cold is safe???

This might help:

For LiFePO4 batteries, the temperature range depends on the storage time. Generally speaking, follow the guidelines below:

• Less than 30 days: -20℃ to 60℃
• Between 30 and 90 days: -10℃ to 35℃
• More than 90 days: 15℃ to 35 ℃

Storing LiFePO4 Batteries in Cold Weather (Winter)​

Low temperature is not an issue for lithium batteries since it leads to slower chemical reactions inside the battery, increasing its life. However, while the battery chemistry enhances in cold weather, extremely cold temperatures may cause some battery components to crack (such as its plastic casing). Therefore, it is a good idea to store lithium batteries indoors and avoid extremely cold temperatures.

How to Store LiFePO4 Batteries

People often store batteries without proper care, only to later find the battery short-circuited, fluid leaking, or not working for some reason. While

ecotreelithium.co.uk

 

[ChrisG]

The heating is only active, while a charging source is available. They aren't powered by the battery.

So if overnight, pack gets to 25 degrees for example. When SCC turns on in the morning the BMS will still block charging if not up to 32 but does the BMS pass current to the heating 'pads' to warm them up?

 

[timselectric]

What power source is it using to warm it up if solar is not producing and you said it uses the outside power source?

It's not warming, if no charging is available.

 

[timselectric]

So if overnight, pack gets to 25 degrees for example. When SCC turns on in the morning the BMS will still block charging if not up to 32 but does the BMS pass current to the heating 'pads' to warm them up?

When a charging source is detected.
If the battery is below the set temperature. The power is sent to the heating. Once the battery is up to the safe temperature. The power is switched to charging.

 

[wme]

This might help:

For LiFePO4 batteries, the temperature range depends on the storage time. Generally speaking, follow the guidelines below:

• Less than 30 days: -20℃ to 60℃
• Between 30 and 90 days: -10℃ to 35℃
• More than 90 days: 15℃ to 35 ℃

​

Good info, but the chart doesn't go to -40. Interesting thing -40 is the same in C or F.
So batteries into the garage for the winter

 

[Bobert]

Good info, but the chart doesn't go to -40. Interesting thing -40 is the same in C or F.
So batteries into the garage for the winter

Yes we live near the Canadian border and we have noticed that -40 is a peacemaking temperature the US and Canada agree on what temperature it is, the Ferrell cats, dogs and other wild animals sleep together, nobody hogs the outhouse. and you hear very few arguments outside.

 

[Nobodybusiness]

That didn't really answer the question?

What power source is it using to warm it up if solar is not producing and you said it uses the outside power source?

"The heating is only active, while a charging source is available. They aren't powered by the battery."

You do not need heating unless you are charging.

If you are charging then whatever power source you are using to charge with will power the heater be that PV, Battery, Generator, Grid, Etc.

If you are NOT charging then no power is needed.

I thought it was pretty clear.

 

[Solarcabin Channel]

You do not need heating unless you are charging.

If you are charging then whatever power source you are using to charge with will power the heater be that PV, Battery, Generator, Grid, Etc.

If you are NOT charging then no power is needed.

I thought it was pretty clear.

You need to bring that battery up to above freezing before it can charge.

These are being advertised as "self heating" batteries but in cold climates those batteries could drop to -20 or lower overnight because they are not self heating.

They would have to warm up when the sun comes up enough to trigger the BMS to start warming the batteries from solar which in my neck of the woods might be days.

So no, it wasn't clear at all and that is why I asked for clarification because the advertising on these is misleading and people in cold climates thinking these would solve the problem are probably going to be disappointed or angry as hell.

My best advice is forget the heating and put your LFP inside where they stay above freezing.

You are welcome!

 

[Nobodybusiness]

You need to bring that battery up to above freezing before it can charge.

These are being advertised as "self heating" batteries but in cold climates those batteries could drop to -20 or lower overnight because they are not self heating.

They would have to warm up when the sun comes up enough to trigger the BMS to start warming the batteries from solar which in my neck of the woods might be days.

So no, it wasn't clear at all and that is why I asked for clarification because the advertising on these is misleading and people in cold climates thinking these would solve the problem are probably going to be disappointed or angry as hell.

My best advice is forget the heating and put your LFP inside where they stay above freezing.

You are welcome!

They are self heating.

As soon as a power source is detected if not at the correct temperature then the power is passed to the heater until the correct temperature is attained then the battery is charged.

If you don’t have enough solar to heat an enclosed battery then you don’t have enough to charge a battery.

 

[Solarcabin Channel]

They are self heating.

As soon as a power source is detected if not at the correct temperature then the power is passed to the heater until the correct temperature is attained then the battery is charged.

If you don’t have enough solar to heat an enclosed battery then you don’t have enough to charge a battery.

Self heating means the battery is heating them not an outside source.

What watts are needed to trigger that heater. Do you know?

In cold climates you may go days with very low sunshine and extremely cold nights and how long does it take to warm that battery up from -20 to start charging in those conditions?

It is not as simple as you think and this needs to be tested under actual cold climate conditions because it sounds like a gimmick to me!