Has anyone switched to a lithium 12V battery?

True. I just quickly turn the stalk from Auto to Off and back to Auto. Done

 

No experience with a 12V lithium aftermarket battery... But for more than 2x of the price of a regular lead-acid battery, do you really get twice the service time? If your OEM lasted ~5 years, that means it has to last more than 10 years to make it worth the cost. Let us know how it works if you buy one. Good luck.

 

Don't do it. It is probably very dangerous. Rechargeable lithium batteries use special charging circuits, and they are typically not interchangeable with other types of rechargeable batteries. They are also a fire hazard even if they are compatible. You don't want a bomb under your hood that could go off in a minor collision.

 

The capacity of this battery is 40 AH, the lead acid one I bought recently is 50 AH.

 

LiFe batteries are not a fire hazard and several available models have built-in BMS to protect the battery during charging. They are, as noted, expensive, so the economics probably don't justify their use as a 12v replacement.

JeffD

 

Keep in mind that lithium batteries protect themselves by not allowing themselves to be charged at temperatures below freezing. So not a good choice as a auxiliary battery in colder climates.


iPhone ?

 

As many have, I took an interest in this once I got a Prius. I have looked long and hard at this issue, and conclude that the thing needed, for complete safety, is a DC to DC charger device, that intercepts the charging and load placed on the Prius standard battery terminal connectors, and sits in between those and the Lithium Iron Phosphate 12V battery.

In my UK money, it’s about £150 from a company in the Netherlands. That’s for a 12V to 12V DC to DC charger/supply device, that’s got 250W capacity.

I am having to guess here - I think the maximum drawdown the Prius can give, on the 12V battery itself, is about 200 Watts. I just add all the lights up and add in some charging on a phone…real guess, but there is always the 400W version if you were in doubt. I don’t think it even gets to 250W is my point.

The theory seems to suggest, that all the concerns about alternators burning out when a LiFePo4 battery’s BMS shuts down once a decent state of charge/unbalanced cells is detected, gives us the green light for direct fitment to a Prius. Because as most of you know, there’s no alternator.

The main takeaways from many fires, and other actual events that scare the pants off people, to do with Lithium:
- these are NOT LiFePo4, they are Lithium-ion, and are more susceptible to these dangerous events.
- it’s important to treat Lithium batteries as if they ‘shrink’ their capacity in heat. Don’t charge them to the max in a cool shaded garage, then fit them to be float-charged in the hot sun inside a vehicle.

So I think this: LiFePo4 batteries should be safe in a Prius, and ought to get charged. In winter, there is no issue except they have the same charging and use issue as any other battery ie they hate sub-zero temps. I wouldn’t expect safety issues in winter. It’s summer that concerns me, it’s the business of keeping these down to 80% or less charging, instead of letting them float-charge/trickle-charge from the Prius in a kind of guesswork way. I don’t think we want any Lithium battery getting charged right to the brim, in case the temperature takes a turn that suddenly makes the battery too small to hold its charge placed in it.

I am thinking, to convert safely to LiFePo4 as a 12V auxiliary Prius battery, or even sensibly to bolster the lead-acid performance, you need to insulate the funny little compartment it is housed in - it’s an ice box. If I can’t be bothered doing anything else, I will pour in a bunch of those foam packing granules, and that would be twice as good as it is now.

I looked at ‘hot plate heaters’, for any battery it seems. You get a digital thermostat, and power it from the 12V battery of any type you are using, and put these little 1 inch square heater devices, into the ‘output’ part of the thermostat. You can set the thermostat to come on at say 2 degrees C (43 F?) and off a couple of degrees higher. So it warms the battery, but only if you’ve insulated it a bit first.

The thermostat probe, you will position by trial and error, until it seems to work when you’d like it too. IE you can feel warmth on the battery in cold times, and then the T’stat soon knocks off again?

So far then, we’ve got insulation of the battery (no foil-covered bubble wrap, it conducts), and warming pads.

Let’s add in solar panel trickle charging. I just rigged up a 4.8W one to my normal 12V Lead Acid battery. £40 UK or so, I sat the solar panel on the back parcel cover just for now, and attached the crocodile clips as directed, to + and -. Don’t believe hype, a lot of solar panels might promise 15W or something, and they are A4 sized. No, can’t work that well, in the climate and season that matters ie winter.

This has to be running only 0.25A or so? But, it might be enough. Can always try two of them.

Now, finally we get to LiFePo4!

If after insulation, a solar panel trickle charger, and the usual basics of scrubbing the earth cable mounting in the rear bodywork, under the trunk/bonnet edging, it’s not as good as you like, we are probably THEN onto Lithium Iron Phosphate as a replacement. I put all the rest above, because all batteries, are poor below zero. They all need the same help.

Ohmmu promise you can just drop it in. It’s not their car. Their liability is limited to the cost of the battery. My view is, you need a definite way of cutting off charging, way before it reaches 100%. And you don’t want a long, guesswork float-charge happening to a Lithium battery of any sort. My little 4.8W solar panel, I could almost discount even in summer. But that’s my guess and my choice.

I just think, if any manufacturer really had this under control, they’e spell out that the critical feature of an 80% charge ceiling, was in their system. This is why I mention the DC to DC device. It’s about 7 inches by 5 inches, and 2 inches deep, from the blurb.

Short version, start with your standard battery:
- insulate that battery compartment to the max
- Solar Panel trickle charger - this too, will provide heating to a small degree, and if insulated, the 12V battery will warm itself somewhat
(- warming pads/hot plate heaters - these seem optional, but under fully adjustable thermostatic control, could be a help)

Now, if you move on to a LiFePo4:
- buy a DC to DC charger/isolator/supply device, like the Orion from the Netherlands
- Buy any reasonable make of 12V LiFePo battery that has a rep - The only one I see is AOLithium, they have an app on the appstore at least

That’s the other point, if you get lithium of any sort, surely you want bluetooth or wifi, so it can be monitored? Following that advice, here are the present costs for me if I were to do this - and I am not at the mo:

- DC to DC 12V 18A charger/isolator/supply Amazon says £136 UK -
Victron Energy Orion-Tr Smart 12/12-Volt 18 amp 220-Watt DC-DC Charger, Isolated (Bluetooth)

- AOLithium battery - or other reputable LiFePo4 battery £169 UK to £450 Uk (!) depending on offers

THE OBVIOUS
On a purely financial basis, this is poop! I’d be paying £300 and THEN needing to wire stuff up. I just bought a Duracell lead acid replacement, for £66UK.

But, not all Prius drivers/owners bought on a purely financial basis.

The AOLithium is not just a ‘drop-in’. You have to screw the standard connectors to their battery terminals, although they are at the correct ends for a Prius. That’s the whole appeal of the Ohmmu. I am sensing, nobody quite trusts it can be that easy, hence the conversation, and every time it is raised on Priuschat, the conversation dies away before we get definitive evidence it worked out fine.

So even if everything worked out, it’s a £500 or $500 or whatever, solution, going LiFePo4 - even the Ohmmu is about $349, assuming it works. I can say, that there’s a lot of LiFePo4 about in boats. Youtube’s bombarding me with sailors’ experiences, but they know a lot about it. I keep feeling we are ‘almost’ there. Take care all, that’s my brain-dump and my research as it stands.