LifePo4 vs winter

[timselectric]

It's not a gimmick, it's a feature.
But I agree that you should keep your batteries in a climate controlled environment.
If they never get cold, they never need to be warmed.

 

[Solarcabin Channel]

It's not a gimmick, it's a feature.
But I agree that you should keep your batteries in a climate controlled environment.
If they never get cold, they never need to be warmed.

Maybe useful to people that rarely get below freezing and have adequate sunshine in winter but they are not making that clear and calling them "self heating" is dishonest advertising IMO.

Thanks for the help!

 

[Nobodybusiness]

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!

Semantics.

I didn’t design the battery so no.

If you don’t have enough to run a simple pad heater then you certainly don’t have enough to charge a battery.

I’m sure battleborn and others don’t sell Gimmick’s.
If they didn’t test it before selling that would be beyond ignorant.
They wouldn’t be in business long.

Try calling or writing Battleborn Technical support if you need specifics.

 

[timselectric]

Maybe useful to people that rarely get below freezing and have adequate sunshine in winter but they are not making that clear and calling them "self heating" is dishonest advertising IMO.

Thanks for the help!

Now that you understand how the feature works. You can decide if it fits your needs.
It doesn't look like it will benefit your situation.

 

[AmpD]

What watts are needed to trigger that heater.

My understanding is that it is a voltage trigger. Once your panels hit operating voltage then the heating kicks in.

This would mean in low light conditions if your panels don’t hit the required charging voltage the batteries stay in protective mode until it detects enough power available to charge them.

The heat is still provided by the battery. The heater just requires that an external source of power is present. If it didn’t then you would likely have dead batteries frequently from a heater running 24/7 and power input lower that the self consumption of the batteries.

 

[timselectric]

The heat is still provided by the battery.

The heating pad is not connected to the cells, in any way.
It's only powered by the charging source.
The BMS chooses where the charging power goes. Either to the heating or the cells, never both.

 

[Solarcabin Channel]

My understanding is that it is a voltage trigger. Once your panels hit operating voltage then the heating kicks in.

This would mean in low light conditions if your panels don’t hit the required charging voltage the batteries stay in protective mode until it detects enough power available to charge them.

The heat is still provided by the battery. The heater just requires that an external source of power is present. If it didn’t then you would likely have dead batteries frequently from a heater running 24/7 and power input lower that the self consumption of the batteries.

The power for the heat only comes from an outside source and only when it reached charging voltage does the BMS shunt that to the heater.

That is why I say it is misleading to call these "self heating" batteries and if you live in very cold country like I do your batteries could easily drop to -20 over night and you may have poor sunshine for days.

So these batteries with heaters would really only benefit people in moderate climates that may rarely get to freezing and has adequate sunshine in winter.

They make 12 volt RV water tank heating pads that use 60 watts and turn on at 45 and off at 65 degrees.

Those would keep the battery from dropping to freezing and the load is not going to drain the battery too fast.

Extreme cold has always been an issue with batteries but even more so with LFP because they can't be charged below freezing.

My suggestion is keep the batteries inside and above freezing but if that is not an option I would get those RV tank heaters and build an insulated box to hold in that heat for my batteries.

I used an insulated box and stored my old Trojans on my solarium porch in winter to bring the temp up and it helped a lot.

 

[timselectric]

If you don't have enough sunlight to heat the batteries. Then you wouldn't have enough sunshine to charge the batteries. So, there's no need to warm up the batteries.
External heating powered by the batteries, just drains the batteries. Which gives you less available capacity for loads. And makes the situation worse, instead of better.

 

[Solarcabin Channel]

If you don't have enough sunlight to heat the batteries. Then you wouldn't have enough sunshine to charge the batteries. So, there's no need to warm up the batteries.
External heating powered by the batteries, just drains the batteries. Which gives you less available capacity for loads. And makes the situation worse, instead of better.

You are missing the point that you have to bring the batteries up to above freezing before they can charge and if you are using that internal heater on a very cold battery that could take hours.

The external heater never lets the battery get below freezing.

 

[Quattrohead]

We see plenty of evidence here of people damaging batteries by overcharging, over discharging, overheating, short circuiting and bad connections, but has anyone actually damaged a battery due to it freezing?

 

[Solarcabin Channel]

We see plenty of evidence here of people damaging batteries by overcharging, over discharging, overheating, short circuiting and bad connections, but has anyone actually damaged a battery due to it freezing?

From what I have read the cells are not likely to be damaged even down to -40F but the outer shell and plastics inside the battery can become brittle and damaged in below freezing temps.

Added: Funny thing is a LFP can be discharged below freezing and a small load would keep the cells producing some heat so if the batteries are in an insulated box and you have a small load running it would probably help keep the batteries warm.

 

[timselectric]

You are missing the point that you have to bring the batteries up to above freezing before they can charge and if you are using that internal heater on a very cold battery that could take hours.

The externa heater never lets the battery get below freezing.

But if you have no sunlight. Your not going to charge the batteries. What little charging you might get. Probably wouldn't replace what the external heating used. Battery heating shouldn't be part of a good design. It's just a optional solution for a problem that couldn't be solved any other way.
If you have no option but to locate the batteries in a cold place. LFP is not the best choice.

 

[Solarcabin Channel]

But if you have no sunlight. Your not going to charge the batteries. What little charging you might get. Probably wouldn't replace what the external heating used. Battery heating shouldn't be part of a good design. It's just a optional solution for a problem that couldn't be solved any other way.
If you have no option but to locate the batteries in a cold place. LFP is not the best choice.

That is why I asked if anyone knows the watts on the internal heater because that would tell us how fast it will raise the temp.

You also need to understand thermal mass and the external heater will heat the battery that acts as thermal mass and in an insulated box that heat will be kept inside so it would not radiate out so the heater would not run that often.

The heater is 60 watts but that does not mean it will run 60 watts continuously with the right set up.

That is why us old off gridders would put our flooded cells all close together in an insulated box because just the heat produced from a small load would greatly help to keep all the batteries warm as that thermal mass holds the heat.

 

[Quattrohead]

Added: Funny thing is a LFP can be discharged below freezing and a small load would keep the cells producing some heat so if the batteries are in an insulated box and you have a small load running it would probably help keep the batteries warm.

See this is what I have always assumed, if you know they are likely to get cold you would have built an insulated enclosure for them and it would probably take many days of substantially below freezing and not using the batteries before they would get cold enough for it to be a concern.
I think it's another marketing angle pounced on by our far Eastern friends due to the breathless wait of the YouTube review with the cup of Frosty cold iced salted water.

 

[AmpD]

It's only powered by the charging source.
The BMS chooses where the charging power goes. Either to the heating or the cells, never both.

good info right there. I didn’t know that. If it can’t do both that makes it pretty useless in the PNW imo.

If its trying to heat itself all day it wont be able to charge. Glad i ran into this discussion!

 

[timselectric]

good info right there. I didn’t know that. If it can’t do both that makes it pretty useless in the PNW imo.

If its trying to heat itself all day it wont be able to charge. Glad i ran into this discussion!

You will damage the cells, if charging them when they are too cold.
Once they have warmed and charging begins. Charging will keep them warm.
There should never be a need for both.

 

[Lost_Wanderer]

If you're using a shunt style battery monitor, how can you know the SOC of your self heating batteries?

The shunt will see power in and count that as charge added (technical term). However, the BMS may send that power to the self heater, not for charge. So you may get an inaccurate SOC. Does anyone know a better way to know the SOC of a self-heating battery in cold conditions?

 

[timselectric]

If you're using a shunt style battery monitor, how can you know the SOC of your self heating batteries?

The shunt will see power in and count that as charge added (technical term). However, the BMS may send that power to the self heater, not for charge. So you may get an inaccurate SOC. Does anyone know a better way to know the SOC of a self-heating battery in cold conditions?

You would have to rewire the battery connections. So that the shunt only measured the actual battery charge/discharge current.

 

[mvonw]

The trick to batteries in very cold conditions is to insulate the batteries, have way more solar panels than you need in summer (x5 or more) and use a generator. I built a super insulated closet for my battery bank (heated batteries), but use a 500 watt heater to keep it at constant 60F in winter. The battery heaters are just a fail safe if the heater fails. In cold climates, its hard to not have a generator to supplement the sun.

 

[Solarcabin Channel]

its hard to not have a generator to supplement the sun.

In all my years off grid I have never used my genny to recharge my batteries.

If your system is sized and oriented correctly for winter you shouldn't need a genny for that.

The main problem is most people put their panels on their house roof that doesn't have good orientation for lower winter sun and the panels don't get cleared of snow. I had that issue the first year I put my panels on my porch roof and learned my lesson.

I moved them to a ground mount with angle and tilt to optimize winter sunshine and was able to use a smaller system and have plenty of power even in hard winters and we get lots of snow and overcast days here. I have 3 small ground mount systems and 800Ah of battery are usually full charged by noon on a sunny winter day and will last me 3 days of low sunshine.

I still have a genny but it is only used for running HD power tools outside. One thing I do now is to recharge several small power stations for back up when ever I have a sunny winter day and just keep them handy for low sun days.

Having multiple smaller systems also means redundancy so if a component in one system fails I still have power from the other systems and the genny is only a last resort.