Dragonfly lithium batteries

[rectalogic]

Anyone have any experience with Dragonfly lithium batteries? Their 100Ah 12v battery looks very similar to the StarkPower 100Ah battery but is $899 instead of $1099 and has a 3 year warranty instead of 1 year.

It has a BMS with high/low voltage protection, high/low temperature protection and cell balancing. The StarkPower BMS does not mention temperature protection.

Batteries - Dragonfly Energy

https://starkpower.com/product/stark...12-volt-100ah/

[hbn7hj]

It is intriguing to me! I would like to know what happens when the engine generator gives it 14.7 volts. Does the BMS reduce it?

Does the BMS heat it using it's own energy so it can be charged below 32F? Lots of questions. $900 still above my threshold but getting closer.

I have known several in the motorcycle world that went lithium. Ended up a waste of money when they failed. Maybe they weren't taken care of properly but I'd hate to fail a $900 battery early. Would certainly like to hear of a successful user.

[wincrasher]

I don't see where they claim low temperature protection. I see high temp in their BMS description. Of course this battery, just like all the other drop-in types, doe not have any kind of internal heating system.

Note their wording is very careful. They don't make any cells. Virtually all cells are manufactured in China. Whether they use a high grade, or off spec cells we don't know. They probably assemble these batteries in Reno as they claim.

FWIW, I own about 7 of the Stark 125 AH batteries. They are phenomenal and have been trouble free. They do have a high temp cut-off, along with the other BMS features. They won't allow more than 15v charging. I've never seen more than 14.6 out of my alternator.

In the Industry, they refer to these outfits that use the low-grade cells and an off the shelf BMS board "sticker boys". Basically all these types of batteries are the same inside, and only the external label with their branding differentiates them. Not sure that these folks are not one of those.

Even my $7000 Lithionics battery does not have a low-temp disconnect if that tells you anything. The only ones I've heard of doing that are doing so with a Silverleaf system, which is outside a BMS box.

[rectalogic]

Originally Posted by wincrasher

I don't see where they claim low temperature protection.

On the BMS features page it says "High/Low Temperature Protection".

Supposedly Dragonfly is developing a new manufacturing approach that led one of the big Chinese lithium cell manufacturers to invest in them to gain access to it.

University alumni revolutionize renewable power companies in Nevada

"Dynavolt's chairman, Lewu Chen, said that the investment in Dragonfly Energy, which is their first U.S. investment, gives them access to technology that is expected to lower their manufacturing costs"

That article also implies they manufacture their own cells:

"Dragonfly Energy intends to expand their pack manufacturing capabilities in Nevada in addition to expanding cell manufacturing"

[wincrasher]

Originally Posted by rectalogic

On the BMS features page it says "High/Low Temperature Protection".

Supposedly Dragonfly is developing a new manufacturing approach that led one of the big Chinese lithium cell manufacturers to invest in them to gain access to it.

University alumni revolutionize renewable power companies in Nevada

"Dynavolt's chairman, Lewu Chen, said that the investment in Dragonfly Energy, which is their first U.S. investment, gives them access to technology that is expected to lower their manufacturing costs"

That article also implies they manufacture their own cells:

"Dragonfly Energy intends to expand their pack manufacturing capabilities in Nevada in addition to expanding cell manufacturing"

But is it on operating or charging. Note the temp range -4 to 160. My guess is the upper range limit is on 160. But I'd not run a battery over 100, let alone those kind of temps.

[booster]

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.

[rectalogic]

Originally Posted by booster

Note that it said expand their "pack" manufacturing capabilities, so it could, or could not, include making the cells that go in the packs.

After that it says "in addition to expanding cell manufacturing" which implies they currently do some cell manufacturing and plan to do more. They could also be expanding from zero cell manufacturing.

[wincrasher]

Well, I'd have to talk with them to determine what is BS and what is true. Cell manufacturing, answered honestly would mean actually making the cells from the ground up with all raw materials. But in actuality, it probably does not mean that here. It could mean any level of post production work from already manufactured cell material.

That is assuming they are using prismatic cells. Could be that this is a cylindrical cell setup. .
Reading between the lines, it looks to me like an assembly operation only.

[booster]

We all know that the battery manufacturers will cherry pick information to to make themselves look better and others less good, and Dragonfly is certainly no exception there. Here is how the do a cost analysis against lead acid batteries. I think, at least to some extent, companies can be judged by the accuracy of their claims, especially about other products that they are comparing to.



Lots of claims there that stretch, like 300 cycles at 50% for lead acid, when it is easy to get 1100 cycle rated ones. And of course the urban legend, IMO, 50% rule. Plus the show using 100% of the lithium capacity.

The little bit of reading I did on them indicates a PHD started Dragonfly, and his big push is in a more economical way to make lithium cells, by altering how a few steps are done in manufacturing them. The price decrease does not seem to be in affect yet, though, as $999 for 100ah is not exactly cheap.

[booster]

Here is what they say about the BMS. Doesn't look like any low temperature things.

[rectalogic]

Originally Posted by booster

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.

[Davydd]

Originally Posted by booster

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.

[rectalogic]

I got this reply from Dragonfly:

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.

[avanti]

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.

[wincrasher]

Originally Posted by rectalogic

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.

[rectalogic]

Originally Posted by wincrasher

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"?

[mojoman]

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

[ManWonder]

Originally Posted by avanti

My AGMs are looking better and better.

LOL - I had the same thought!

[rectalogic]

Originally Posted by wincrasher

That is assuming they are using prismatic cells. Could be that this is a cylindrical cell setup.

Dragonfly said:

We only use cylindrical cells, they have better cycle life.

[Bud]

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.

Bud