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Old 03-19-2017, 01:53 PM   #11
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The price decrease does not seem to be in affect yet, though, as $999 for 100ah is not exactly cheap.
The price they quoted me (for a single battery) was $899. Still not that cheap.
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Old 03-20-2017, 03:25 PM   #12
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I think -4 is also the low temp damage temp the davydd had been told by ARV? That would also include storage that cold. Charging would still be at 32* cold side limit, I would think.

Note that it said expand their "pack" manufacturing capabilities, so it could, or could not, include making the cells that go in the packs.
-4F (-20C) comes from Elite Power Solutions LiFeP04 batteries as the low limit to prevent permanent damage whether in use or not. Only an outside the battery heat source can prevent that. That was new information that came out just a year ago and I don't think anyone was aware of it. Obviously the more advanced lithium battery boating industry was not about to be plowing the seas in those temperatures. If anyone is making other claims I think I would be a bit leery about the information.

32F (0C) internal battery temperature will cause damage if you attempt to charge at that temperature. More realistic is 35F for cutoff protection and Advanced RV keeps the optimal temperature above 42F (5C) Realistically with external heating, since the battery internal temperature in use is going to be well above ambient you most likely will not be camping in much colder. My experience is it has to get down to 20F or so before our external heat pads come on.

Upper temperature is rated at 145F and for longer battery life it is best to stay below about 110F or less. The only way to do so for us is to simply stay away from those temperatures and our philosophy to travel when and where air conditioning is seldom necessary the mission is accomplished. The Technomad people were the first to highlight this issue, but they encountered probably the most extreme situations possible and lost 25% battery capacity over 3-1/2 years when they reported it. Extremes like keeping batteries in an unconditioned oven like space sitting on asphalt over a 6 month summer period in Arizona. I doubt you could get much more abusive.

Our BMS controls all this. It doesn't control high temperatures. Charging will shut down automatically for cold temperatures. You can still draw off the batteries. So traveling in extreme cold temperatures with 800ah battery pack boondocked is achievable with a 10a draw for heating pads to keep battery temperatures above 42F assuming you travel or idle (second alternator) and recharge with regularity. We boondocked a week straight in a period where day and night temperatures were always below freezing mostly in the teens and down to 0F.
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Old 03-20-2017, 04:56 PM   #13
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I got this reply from Dragonfly:

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The BMS will prevent charging when the internal temp is below 25F. This is to protect the cells from lithium plating. It will discharge, keep in mind at the these lower temps battery capacity is decreased.

At 32F you will have approx. 85% capacity and it will diminish from here.

We do not make cells here in Nevada, we get them from our business partner Dynavolt. We only use UL listed cells from highly automated, clean factories. Our packs are currently marketed as Designed and Assembled in the USA. Currently there are no LiFePO4 producers outside of China that can support our volume.

We will be making cells here late next year.
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Old 03-20-2017, 10:12 PM   #14
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My AGMs are looking better and better.

I guess if you really want to run a huge A/C all night you have no choice but to go with Li. But for our usage pattern, our 440Ah of AGM plus a second engine alternator seems to be a sweet spot. Except for the very rare A/C issue, we never have to think about power. Yes, we do have to turn on our inverter to make coffee or run the microwave, but we somehow soldier on. Even if they were the same price, I am not sure I would switch to Li until the edge issues are sorted.
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Old 03-21-2017, 05:24 AM   #15
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I got this reply from Dragonfly:
As I thought, "sticker-boys". Not shocked. There is no lithium (LiFEPO4) cell production in the US of any scale. Just lab scale operations from what I'm told.
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Old 03-21-2017, 02:30 PM   #16
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As I thought, "sticker-boys". Not shocked. There is no lithium (LiFEPO4) cell production in the US of any scale. Just lab scale operations from what I'm told.
So it sounds like I should be comparing the cell manufacturers specs between StarkPower and Dragonfly (Dynavolt). Who manufactures Starks cells such that they are not classified "sticker-boys"?
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Old 03-21-2017, 03:17 PM   #17
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If you look around Alibaba you can find very similar batteries and the prices have gone way down since I started shopping for them a couple of years ago. Around $350 for a 12v 100AH battery
https://www.alibaba.com/trade/search...4+battery+pack
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Old 03-21-2017, 03:19 PM   #18
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My AGMs are looking better and better.
LOL - I had the same thought!
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Old 03-21-2017, 04:02 PM   #19
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That is assuming they are using prismatic cells. Could be that this is a cylindrical cell setup.
Dragonfly said:
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We only use cylindrical cells, they have better cycle life.
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Old 03-21-2017, 08:46 PM   #20
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I don't recall any post about building or whatever one might call it, creating a battery from the same kind of batteries Tesla and others use, the ubiquitous 18650 kind of battery? Has anyone done this for an RV?

I recently purchased an electric bike and folks do just that.

Thanks.

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