profdant139
Southern California
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Some of the preceding discussion is over my head, so let me bring things back to a more basic level. It looks like I will need an insulated battery box and a heater to keep the lithium battery above freezing. But the heater draws current, of course.
So I would have to budget a reserve of power in order to make sure that the battery is warm enough to accept a charge.
This may be a deal killer because we are almost always away from the trailer during daylight hours, hiking or snow-shoeing or skiing. So we would not be in a position to monitor the battery and the solar charger in real time, to make sure that we are not damaging the system and that there is enough juice to run the fridge, etc.
Hmmm. We may not be ideal candidates for lithium, until they work out the temperature issues. That is really too bad. But I am not ready to give up on snow camping.
2012 Fun Finder X-139 "Boondock Style" (axle-flipped and extra insulation)
2013 Toyota Tacoma Off-Road (semi-beefy tires and components)
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Grit dog
Black Diamond, WA
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^ Yeah, so much for real world advice and NOT diving into the weeds....
I think the simple answer is move the batteries inside the camper somewhere. Storage and discharge below freezing aren't so much the issue as trying to charge a cold battery. Presuming you arent letting the camper cold soak down well below freezing and at the same time expect to be charging the batteries, that's a good compromise since you're not really going down into extreme cold temps.
Remember it's the battery "core" temp that matters. I use a LFP on my snowbike. It is certainly in the "cold" all day. Older original battery needed much more "warm up" before it would discharge at a fast enough rate. Couple bumps of the starter to load the battery momentarily and then off to the races.
If you are to the point where insulated boxes with pad heaters are needed, just scratch LFP as being practical. If you can do the above suggestion to keep them warmer without extra effort, then IMO it will work fine.
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S Davis
Western WA
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It really doesn’t take a lot to keep the cells warm, I use a 3”x3” 12 volt 25 watt silicon heat pad on each battery and they have worked perfectly down to 8f in back seat area of my crew cab. I have them set about 50 degrees, with two 280ah batteries I can spare the ah to run them.
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3 tons
NV.
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Joined: 03/13/2009
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profdant139 wrote:Some of the preceding discussion is over my head, so let me bring things back to a more basic level. It looks like I will need an insulated battery box and a heater to keep the lithium battery above freezing. But the heater draws current, of course.
So I would have to budget a reserve of power in order to make sure that the battery is warm enough to accept a charge.
This may be a deal killer because we are almost always away from the trailer during daylight hours, hiking or snow-shoeing or skiing. So we would not be in a position to monitor the battery and the solar charger in real time, to make sure that we are not damaging the system and that there is enough juice to run the fridge, etc.
Hmmm. We may not be ideal candidates for lithium, until they work out the temperature issues. That is really too bad. But I am not ready to give up on snow camping.
Well, situations often differ, so in this regard I can only speak to my own situation…In my case, the OEM exterior battery box extended beneath the dinette seat, so I simply removed the nylon battery box, sealed and insulated the exterior door, and put two 200a/hr LFP’s in-parallel beneath the dinette seats..During unattended winter camping we leave the furnace set on 55d/f anyways (to heat enclosed basement tanks, dump valves and plumbing), so solar charging can be concurrent…
Example: Do to evolving needs over time (lol!) I’ve now expanded to having three separate solar PV systems (a 500w, 260w rooftops, and an occasional ground deployable 360w for longer desert excursions), each system having it’s own independent charge controller…
This may sound a bit haphazard ![[emoticon]](https://forums.goodsamclub.com/sharedcontent/cfb/images/scratchead.gif "scratchead") yet in actual practice, by operating just one of the three separate systems (or some wattage combination thereof), I can reasonable project and plan for the expected amount of per hour harvest return while absent…
When enjoying extreme off-roading, the added charge flexibility here (regardless of season) has proven to truly be a major bonus, since I can reasonably plan for a desired amount of harvest!
FWIW, one of my controllers (the BlueSky) is programmable for voltage parameters and for timed duration at 100% SOC - so were I to opt for a FULL unattended charge (*however unlikely...) the controller would shutdown shortly thereafter…
* (unlike wet-cells, a routine ‘full charge’ is required only occasionally.)
Hope this helps,
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mordecai81
United States
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I like making things more complicated than they need to be as much as the next guy, but it's actually pretty simple, even with the battery living on the tongue. I set up the heater per the manufacturer's instructions. It keeps the batt above 37 degrees-ish. The solar does it's thing. If I'm short amps in the evening I fire up the genny, charge at 45 amps for between 20-60 minutes and call it a day. Easy peasy. It most likely woulb be more complex at -30c but whose crazy enough to camp at that temp![[emoticon]](https://forums.goodsamclub.com/sharedcontent/cfb/images/smile.gif "smile")
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profdant139
Southern California
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Mordecai, what do you use to monitor whether you are short amps? (Different from a short circus, I think.). ![[emoticon]](https://forums.goodsamclub.com/sharedcontent/cfb/images/wink.gif "wink")
No, seriously, which device will give you an accurate picture of the remaining battery capacity? Using a cheap multimeter, I often check the voltage on my lead acid batteries, on the theory that any reading below 12.1 means that I've got a state of charge less than 50%.
But with lithium batteries, the voltage does not drop, I think. The battery goes from "full" to "dead," if I remember correctly.
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S Davis
Western WA
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profdant139 wrote:Mordecai, what do you use to monitor whether you are short amps? (Different from a short circus, I think.).
No, seriously, which device will give you an accurate picture of the remaining battery capacity? Using a cheap multimeter, I often check the voltage on my lead acid batteries, on the theory that any reading below 12.1 means that I've got a state of charge less than 50%.
But with lithium batteries, the voltage does not drop, I think. The battery goes from "full" to "dead," if I remember correctly.
Full charge is about 13.4 volts, at 12 volts you are at about 10% charge with LifeP04. Voltage does drop with state of charge just not as much as lead acid.
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theoldwizard1
SE MI
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Joined: 09/07/2010
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profdant139 wrote:
This may be a deal killer because we are almost always away from the trailer during daylight hours, hiking or snow-shoeing or skiing. So we would not be in a position to monitor the battery and the solar charger in real time, to make sure that we are not damaging the system and that there is enough juice to run the fridge, etc.
Do you take a generator when boondocks ?
Install the batteries inside. When you get back from your outside adventure, start the generator and a couple of electric heaters. If you have a good battery management system it will not allow the batteries to accept a charge until they are at a safe temperature.
Watch the Will Prowse YouTube channel. He reviews solar panels, inverters, chargers and batteries. He always comments if the battery management system has cold weather protection.
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theoldwizard1
SE MI
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profdant139 wrote:No, seriously, which device will give you an accurate picture of the remaining battery capacity? Using a cheap multimeter, ...
Stop right there ! Spend the money and get a QUALITY battery monitor. Victron makes some nice ones. Get their base model. It does what you want.
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3 tons
NV.
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Joined: 03/13/2009
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theoldwizard1 wrote:profdant139 wrote:No, seriously, which device will give you an accurate picture of the remaining battery capacity? Using a cheap multimeter, ...
Stop right there ! Spend the money and get a QUALITY battery monitor. Victron makes some nice ones. Get their base model. It does what you want.
X2, you might consider either their Smart-Shunt or the BMV-12, both are LFP capable, and have built-in bluetooth along with good phone graphics.
3 tons
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