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Old 08-04-2016, 12:55 AM   #1
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Default LiFeP04 Operating Temperatures

Here is a bit of information Advanced RV mentioned to me. To corroborate I asked Elite Power Solutions about it.

My question:

You say the operating temperature for 200ah GBS batteries is -4F to 149F. What is the effect on the batteries if totally disconnected and stored when temperatures drop lower than -4F. In Minnesota I can expect outside temperatures to drop to around -20F in the winter at times. My 800ah battery bank is not removable in any practical manner. I could face a storage situation when not using my RV where I cannot plug into shore power to utilize my heating pads to keep temperatures above freezing as I normally have done.

Elite Power Solutions' Answer:

Temperatures below -4F (-20C) will cause the electrolyte to freeze which will cause permanent damage to the batteries if it does not kill them entirely. If storage temperatures will go below -4F then you will need to heat the batteries to above -4F to prevent damage to the battery. There is no exception to this.

There you have it. You have to keep your lithium ion batteries above -4F (-20C). Also you can draw power from them at temperatures down to -4F and still be 90% efficient. You cannot charge them below freezing of 32F. Optimally you should keep your batteries stored and above 41F.
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Old 08-04-2016, 01:08 AM   #2
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That is an "ouch" for those of us in the frozen north

How are you going to handle that if you wind up without shore power in your winter storage area?
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Old 08-04-2016, 02:01 AM   #3
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Default LiFeP04 Operating Temperatures

Davydd - thanks for posting this information. I was aware that LiFePO4 batteries have some cold temp issues. This is good info from a reliable source, more so than some of the Chinese manufactures questionable information. It also confirms that I made the right choice staying with Lifeline AGM batteries when I did my upgrade. I have been in Minnesota for weeks in February and seen overnight temps at -20F all week. Here is the temperature considerations page from Lifelines manual. A fully charged AGM can handle some very low temps.



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Old 08-04-2016, 02:38 AM   #4
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That is an "ouch" for those of us in the frozen north

How are you going to handle that if you wind up without shore power in your winter storage area?
This winter it will not be a problem I hope as we don't anticipate moving until March to an HOA development. I'll just stay plugged in as always. Looks like I'll be looking for inside storage with power or temperature control or I will just have to head south in the RV for the winter. We plan to be in the Washington DC area for Christmas.

The winter before last it would not have been much of a problem when the temperature rarely got below 0. In years past we had one time when it got down to -43 in our woods. The official temperature was about a -32. Staying plugged in the batteries stay warm from the heating pads designed to keep the temperature above 41 degrees.

I found a couple of LiFeP04 sources that said temperatures could go down to -22F. That may be true or maybe not. Elite Power Solutions say no.
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Old 08-04-2016, 02:40 AM   #5
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Interesting.

OK, so here's a challenge for you "armchair" theoreticians:
If DavyDD started a -20 degree cold spell with his awesome battery completely charged, how long could he run his heating pads at just enough current to keep the batteries above -4 degrees? Don't forget to take into account the battery self-heating under load.
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Old 08-04-2016, 02:43 AM   #6
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Originally Posted by Boxster1971 View Post
Davydd - thanks for posting this information. I was aware that LiFePO4 batteries have some cold temp issues. This is good info from a reliable source, more so than some of the Chinese manufactures questionable information. It also confirms that I made the right choice staying with Lifeline AGM batteries when I did my upgrade. I have been in Minnesota for weeks in February and seen overnight temps at -20F all week. Here is the temperature considerations page from Lifelines manual. A fully charged AGM can handle some very low temps.
On the road a fully charged lithium ion battery is not going to be a problem as the 12v heating pads will keep the battery temperatures above 41 degrees and lithium ion batteries charge fast. It is unoccupied storage not plugged into shore power that is the problem. One only needs a 15 amp plug in since the air conditioning won't be needed.
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Old 08-04-2016, 03:03 AM   #7
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Interesting.

OK, so here's a challenge for you "armchair" theoreticians:
If DavyDD started a -20 degree cold spell with his awesome battery completely charged, how long could he run his heating pads at just enough current to keep the batteries above -4 degrees? Don't forget to take into account the battery self-heating under load.
No armchair. I have already experienced and monitored it. I will draw 10 amps per hour to keep them above 41 degrees. I have to be well above -4. I have to be above freezing to be able to charge. That can be accommodated easily occupied and on the road with an 800ah battery bank just driving less than an hour or fast idling for one hour. Most of the time when temperatures are somewhere above 20 degrees the internal battery temperature will suffice to keep them above freezing and the heating pads won't come on. At Mike Wendland's Winterfest last January when the temperatures stayed in the mid 20s the heating pads never came on. I camped on the road for a week with temperatures always below freezing day and night and down to 0 F. one night. It was never a problem. Given that the battery temperature will most likely run anywhere from 10-20 degrees hotter than ambient and most daytime temperatures rise above -4 I probably could theoretically get by but only if I am there to monitor it.
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Old 08-04-2016, 03:21 AM   #8
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I found a couple of LiFeP04 sources that said temperatures could go down to -22F. That may be true or maybe not. Elite Power Solutions say no.
Is the LiFeP04 electrolyte freezing point affected by the battery state of charge?
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Old 08-04-2016, 03:21 AM   #9
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No armchair. I have already experienced and monitored it. I will draw 10 amps per hour to keep them above 41 degrees. I have to be well above -4. I have to be above freezing to be able to charge.
You miss my point. I agree with you that when the vehicle is in use there is no issue. I was thinking about storage, and how long of a cold spell you cold weather without shore power. It takes a LOT less energy to keep the batteries at -4 than it does to keep them at +41. My intuition is that we might be surprised how long one could go in cold storage with a properly-designed system. But, only theory will tell the tale.
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Old 08-04-2016, 04:32 AM   #10
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When you take a batteries offline they will eventually and probably quickly equalize out with ambient temperature. Only when in operation do they stay warmer. So unattended offline you have to keep them warm by staying plugged in with heat on them or inside above -4. There's no theory about that. I know.
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Old 08-04-2016, 04:40 AM   #11
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The only problem I see is power outage due to weather. If the van is onsite, you can always go out and run it. If it's offsite and you can't get there for several days, then you could be expensively screwed. But you do have autostart, so I imagine it really depends on how much diesel you have on board and if you can monitor your system via iPhone.
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Old 08-04-2016, 04:40 AM   #12
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You miss my point. I agree with you that when the vehicle is in use there is no issue. I was thinking about storage, and how long of a cold spell you cold weather without shore power. It takes a LOT less energy to keep the batteries at -4 than it does to keep them at +41. My intuition is that we might be surprised how long one could go in cold storage with a properly-designed system. But, only theory will tell the tale.
It shouldn't be hard to incorporate a configurable storage mode that instructs the BMS not to fire up the heater(s) until the temp goes below x degrees with a bottom limit of 0F and then providing only enough heat to stay above the battery freeze point.

But this wouldn't be sufficient to deal with an entire winter season unless the coach was outside and could provide solar support. The fact that in Class B construction, the batteries are typically so inaccessible doesn't help. There has been some valid criticism of the idea of committing interior spaces like under a bed for the batteries. I get that, but on the other hand if they were accessible you could just yank them out for the winter.
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Old 08-04-2016, 04:42 AM   #13
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Is the LiFeP04 electrolyte freezing point affected by the battery state of charge?
No. You do have to make sure you do not run your batteries down. Disconnected lithium ion batteries lose about 3% of their charge per month. With my 800ah battery bank that would be about 24 amps per month. I could easily let them sit over a winter as long as the temperature is above -4. Elite Power Solutions recommends you recharge your batteries when and if the voltage drops below 3 volts for the individual 3.2v cells. That would mean you would want to keep them above freezing in order to do so. The easiest solution is to stay plugged into shore power which I had done the past two winters.
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Old 08-04-2016, 04:46 AM   #14
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When you take a batteries offline they will eventually and probably quickly equalize out with ambient temperature. Only when in operation do they stay warmer. So unattended offline you have to keep them warm by staying plugged in with heat on them or inside above -4. There's no theory about that. I know.
You are not listening.
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Old 08-04-2016, 04:58 AM   #15
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But this wouldn't be sufficient to deal with an entire winter season unless the coach was outside and could provide solar support.
It wouldn't have to make it through the winter, just the days when it was below -4. Even in Minnesota, that number is limited. But, yes, solar would be good.

If I were designing this, I would probably design a separate "deep sleep" system that was dedicated to this one function and used an absolute minimum of power. Other than the power to the pads, this could be negligible. It really would be interesting to do the math. We are talking about a pretty large battery, and very few degrees above ambient. Add in the battery self-heating, and it just might be feasible.

---
Hmm. I just checked: The longest streak of consecutive days below zero in Minn/St. Paul was 36 in 1936. Pretty grim. Much worse than I would have guessed.
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Old 08-04-2016, 05:18 AM   #16
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The only problem I see is power outage due to weather. If the van is onsite, you can always go out and run it. If it's offsite and you can't get there for several days, then you could be expensively screwed. But you do have autostart, so I imagine it really depends on how much diesel you have on board and if you can monitor your system via iPhone.
Fuel wouldn't be relevant with RT because their Voltstart only engages for five 30 minute periods without requiring a manual reset. Are other autostart systems similarly configured? BTW, with the seriously diminished CCA available on a battery at -25F will the Mercedes diesel crank and start at this temperature?

If the coach is in enclosed unheated storage, IMO utilizing any autostart feature would not be a good idea.
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Old 08-04-2016, 07:10 AM   #17
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.

The perfect storm...

enclosed unheated storage,
no solar,
no plug-in,
36 consecutive days below zero,
you are screwed.


Go south, young men, go south.

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Old 08-04-2016, 07:37 AM   #18
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That is an "ouch" for those of us in the frozen north

How are you going to handle that if you wind up without shore power in your winter storage area?
There have to be some Volts, Leafs & Teslas parked in frigid Minnesota during one of these -25F periods. How do their batteries survive?
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Old 08-04-2016, 08:20 AM   #19
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There have to be some Volts, Leafs & Teslas parked in frigid Minnesota during one of these -25F periods. How do their batteries survive?
Have you looked at a Tesla battery?
It has its own liquid cooler and heater.

From the manual: Do not expose Model S to ambient temperatures above 140 F (60 C) or below -22 F (-30 C) for more than 24 hours at a time.

The bottomline is, for long term survival, it has to be plugged in.


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Old 08-04-2016, 08:25 AM   #20
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.

Vampire Drain: How Much Power a Tesla Model S Really Loses in Almost a Month
https://transportevolved.com/2014/01...lmost-a-month/


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