LiFePo4 as a do-everything battery?

[dyeager535]

Is anyone already running a LiFePo4 in their truck?

Pretty good article here about replacing dual battery/lead acid/AGM batteries with a single LiFePo4 https://www.takethetruck.com/blog/overlanding-battery?format=amp

I feel we are still early enough in the LiFePo4 story to see whether prices will continue to drop, and/or something better comes along before they replace lead acid/AGM. But with the cost of starting batteries being what they are now (Walmart selling 800CCA group 78 starters for $140), and the quite short life they seem to have, a battery with an 11 year warranty and probably a far longer lifespan if used simply as a starting battery, holds appeal.

Still a lot of money, but I think if dual batteries were a consideration, these should end up costing less in time.

The Dakota Lithium 60Ah starters are $600. Unfortunately those still have a ways to go IMO, as they are unheated (no charging under 32*) and limited to 80amp alternators. At 16.5lbs though, you'd probably never break the stock battery tray lol.

I haven't checked to see who else is making starter LiFePo4's, so there may be alternative LiFePo4 batteries already out there that are better suited to "truck use". Again, based on my opinion that 80 Amp max input may be too low for some applications, and an automotive battery needs to charge under all conditions. There is more consideration when it comes to charging as too. Since they will shut off charging, I believe that would spike alternator output.

While I don't do a lot of camping that requires power, you could certainly replace a generator with an inverter and use the "starter" battery for a fair bit of power if you needed it for a 12v fridge, TV, etc.

Definitely appeals to my gadget side lol

 

[JoshHefnerX]

The little bit I've read lately about them as I need batts for my trailer. What I've gathered is they're good for RV's maybe not quite ready yet for autos. They're good at using full capacity (deep cycle) but not real good at dumping a bunch of power quick - starting. Although that's a generality.

They can take a fair bit of amperage charging, but need higher voltage than acid/agm type batts to hit full charge. Alternators are capable of hitting that voltage, but w/ the computer controls, I don't think that's a given so I don't believe you'll ever really get a full charge on one.

If it were me, for overlanding. At this time, I'd prob stick w/ common lead/acid/agm tech for starting and have separate lithium house batts.

 

[Wes Harden]

yes they need a different charging strategy, then current auto batteries. I know the the update power converter for our RV has 4 battery charging modes, 1 of them is LiFePo4.

which I still need to install in our coach

 

[dyeager535]

Yes, it seems even the sellers have differing views on the charge scheme. But it does require higher input voltage. It's crazy to me that some are selling starter batteries for mowers, atv's and such, then acting like those don't try and charge the battery. Perhaps they are just assuming the voltage isn't high enough to charge.


In the linked article they have a device to buy that makes sure your alternator doesn't spike when the battery turns off. Too much work to be practical to run off battery alone for me, but would be interesting to see how long the truck would run.

My alternator output is exactly what the LiFePo4's want, so in my case I wouldn't have an issue there. I did read a thread by a Corvette guy that ran two much smaller ones (like 14Ah total?) which is far more cost effective. I'd have to read it again, I'm pretty sure he was using older tech charging stuff, like a 12SI. He had run it long enough to have proven it worked longer term.

The group 78 size LiFePo4s can be had under $200 now (not the ones suitable as starters), it would be nice to see the starters price cut in half as well. I'd expect as the price gets close to lead acid/AGM more work will be done to retrofit them.

 

[JoshHefnerX]

The onboard bms may help with the charging. However, the problem in general with lithium tech is the current draw.

Have a look at c-ratings, you can only pull so much amperage out of a cell before it overheats. It's a chemical limitation.

At present the only way to overcome it is with more cells. Electric cars use hundreds of not thousands of cells to account for this. 18650 or 21700 usually.

 

[dyeager535]

I think what they are doing is limiting the amount of time a certain amperage can be pulled.

"100A max continuous discharge, 750A max 2 second pulse, 650A max 5 sec pulse." That one's ~2C if I have my numbers correct? (100a constant discharge, 60Ah capacity)

I've tried to find actual starter draw specs, but I haven't seen anything from GM. 300A seems a fairly consistent theme, so given that, the above battery would be well within the GM starter draw range I've seen, which some states as high as 500A. Mini starters I'm pretty sure Ive seen manufacturers state around 125A.

Since voltage doesn't sag on lithiums as I understand it, you'll get 12.8V out of it no matter the draw, so cranking should be even stronger than a lead acid starter.

I'm not so concerned about their claims, they are confident enough in them that they are warrantied for 11 years. Unless of course their business model is sell a bunch in two years then go bankrupt lol. Why I'd like to see them come way down in price before I would spend the money on one. I don't have a lot of faith in companies sticking around.

 

[Blue85]

Since voltage doesn't sag on lithiums as I understand it, you'll get 12.8V out of it no matter the draw, so cranking should be even stronger than a lead acid starter.

Every battery has some internal resistance. I think a standard 18650 cell is about 25mOhm. The pack resistance depends on how many cells you have in series and parallel. Let's say you have 4 layers of 20 cells, that's 5mOhm total, so drawing 100A will drop the voltage .5V

A "12V" battery will be 4 in series, so it should be 13.3V at 80% SoC and down to 12.8V at 20% SoC. Typically that's the range you use them in for good lifetime.

 

[Blue85]

One of these would be great just for power accessories, but I also run my winch from my aux battery. It would be sweet to have enough of these in parallel to support a stalled winch. You could pull quite a while without the engine running. Although, the off-road recovery bill might be cheaper than the batteries.

 

[Polymath]

My experience is a good five years old in this technology, but if it's anything at all like the EarthX and Shorai lifepo4 batteries I used in motorcycles, i'd never put one in a car. The only reason is that they absolutely suck when they get too cold, and I see -40 every year. I might be swayed into using one for a modern EFI vehicle that can fire up within half a second of the starter being engaged. But for anything carb'd or running poorly enough that you need more than 5 seconds of cranking time to get started, forget about it. When the temps drop, you run a serious risk of being stranded.

Besides, the upside for motorcycles is weight savings. Dropping ten pounds of weight from a 250-500lb bike is considerable. Dropping 30lbs from a 5,000lb SUV is nothing.

Best use I think would be as an isolated accessory battery to run things while the car is off. Even then, I personally wouldn't spend that kind of money on one versus a well known Optima.

 

[dyeager535]

Yes, I don't see unheated versions being practical in cars. I guess if you never leave southern California maybe you could get by, but so far the heated ones are somewhat less common (and more expensive) than unheated. If they want to replace more lead acids/AGM's they'll need to make it much more common. It seems like it's getting there, but still going to take time.

I suppose some of the idea behind unheated being relatively less common is that they can be used in occupied spaces . They dont off-gas like lead-acid and they don't catch fire like lithium ions. But again that speaks to pure deep cycle use, and not starting.

That said, even if you screwed up with one of these and left a draw on it until "dead", the BMS won't allow the battery to be damaged. BTDT, cost me $100 or so when I killed my starter leaving the key on.

I feel there is a lot to these things, but so far cost and the limited availability of heated starting batteries will keep most from adopting them.

In the smaller applications (atv's, lawn tractors, etc) the cost is MUCH closer to a lead acid. Maybe double, but that's tolerable at maybe $100. IMO right now they make more sense in those applications. Those batteries really seem to take abuse, my experience has been the lead acids don't seem to hold up real well. Sitting for 4-6 months doesn't help, LiFePo4 would make a difference there. I've got so many batteries on maintainers now I can barely keep track. It wouldnt hurt my feelings to not need to worry about maintainers.

 

[Blue85]

It truly seems like a complicated solution, especially given how well LA can work.

Typically, they can discharge at much colder temps than they can charge, so you may be able to start the engine, but not charge - isn't that essentially running with no battery? I see that they make a big TVS diode to clamp the alternator transient, but some alternators are not good at regulating without a battery or at least a lot of load and any aftermarket equipment in the vehicle may get a reset or have some other odd behavior. Of course in the cold scenario, you would be dumping some power into a heating pad. If you had a monitor or external BMS I suppose you could run the heating pad (or internal grid heater) from the battery to bring it up to charging temp before starting, but that's a lot of extra time and hassle. From an "overlanding with only 1 battery" standpoint it sounds kind of sketchy. You ran the fridge and the blender last night, it's really cold now and you don't have enough power to both warm the battery and start the engine.

 

[Wes Harden]

With the margarita hang over next cold ass morning, just stay in the warm ass sleeping bag and forgetadodit

 

[Blue85]

Get out of your warm sleeping bad and wrap it around the battery. Set the battery near the camp fire? At least they're light. That's it...sleep WITH the battery!

 

[Polymath]

Blender and fridge. Haha! I made the mistake of opening the automatic-lift hatch of my old Yukon too many times while out camping and it killed the battery. Thankfully we were not the only vehicle and I had some jumper cables. That was eye opening though. Who would have guessed that hatch was sucking up 1/20th of the battery capacity with every use?

 

[dyeager535]

From what I understand the heat is automatic. To be fair, I've not seen them say what sort of drain that is. But would seem to be wasteful if the thing just heated itself based solely on temperature vs. actual use. Eventually even just sitting the battery would drain itself in cold weather then. I would *expect* that not to be the case, but I also havent seen it spelled out how that is accomplished.

With the battery essentially being computer controlled, they should be programmed to heat only when it's necessary...below the temperature they are safe to draw from, and when the BMS sees an attempt to charge.

If that is all automated and regulated so I don't have to worry about it, the only remaining issue is playing nice with the alternator. But everything will have to be so automated that there is no difference from the drivers perspective between it and a lead acid.

Like I said way back, if I expected to dual-use my starter battery as a 12V power source (or trolling motor, etc), the LiFePo4 would have no peer. But at 6-7 years now on my ~$100 lead acid that is very infrequently used just as a starting battery, there is no way to justify it.

Then again, at 16lbs, would be fairly easy to pull out of the truck and use with an inverter to power a propane stove or wood fireplace fan during a power outage. I've also got a 36V golf cart that needs a new battery (6 x 6v presently), and that would provide a lot more power, for longer, if used to feed an inverter.