LiFePO4 batteries for petrol/diesel cars

[Simon54]

These are becoming a thing... if a bit expensive. I'm not wanting to debate the merits of them here just the practicalities, has anyone done this?

There are a few manufacturers now, but information seems scarce, most of it geared towards reducing weight for the same performances. I haven't found some site where you can put your reg in and find an equivalent. I need to take the dimensions, and CCA figure and then search for a battery that exceeds that. I'm looking for a higher capacity but taking up the same space in the battery compartment, this is to avoid adding extra batteries elsewhere inside the vehicle for extended periods with the engine off.

I'd appreciate any advice/experiences.

Many thanks,
Simon.

[Baldchap]

I think I'm right in saying this is what my Elise Cup came with.

They need management hardware under normal use (box thing on top of battery that apparently ’manages' it) and if left for over a week need to be on a charger according to the manual addendum that came with it. And a special battery charger.

Not had it out so can't comment on the weight.

[SimonTheSailor]

I've got one in my boat as a leisure battery.
The benefits are that for the same rating - say 100ah - you have twice as much capacity as you can use all of it. You can drain them down to zero and they don't care. With a lead acid you are supposed to recharge them when they get down to 50%, so you've only got half the usage out of the same 100ah battery.
They also recharge quicker, they suck in any power they can like solar power and alternator power. They can be recharged a few thousand times rather than a few hundred.
They are a lot lighter and slightly smaller.
But three times more expensive.
They are the reasons why people are using them for leisure batteries.

Not sure why they are that great for starter batteries.

The best ones do have a battery management system built in so you can change/monitor lots of parameters.

You have to be careful with lithium/Lifepo4 batteries with the alternator as it charges like crazy then the BMS just shuts off the charge. The alternator runs a lot more at a higher output, which you don't really want on a starter battery, you want it slowly charging the lead acid battery as that's how they liked to be charged.

ETA - apologies, just realised you said that you don't want to discuss the merits

Edited by SimonTheSailor on Saturday 1st April 13:35

[Simon54]

SimonTheSailor said:

ETA - apologies, just realised you said that you don't want to discuss the merits

What I meant was I didn't want to have a big argument about the merits, as often on forums you ask a question and the first 4 answers are something along the lines of "you don't want to do that because...". Then you can spend several posts explaining that yes, you do in fact want to do that because you did actually spend an hour or two researching it before you posted, blah blah.... but that's not the case with your post so I appreciate that!

There are a range of batteries call Antigravity which take care of the BM side of things for you, and give you one box that replaces what you had before, also with bluetooth access from your phone so you can access it with an app. I think Ultralife, KSEngergy, are other options, but most of these involve contacting the company involved to find out more details, and that's always worked out costly for me.

I expect something like this turned up on Aliexpress or Banggood by now (if I wanted to wait a coupla months) but to be honest I didn't even look so far because I don't want anything too dodgy in my engine compartment!

[OldGermanHeaps]

I had 2 different brand ones on my wr250 and both suffered self discharge which i never had with a yuasa lead battery. The weight reduction was slightly noticable on an already light offroader though, especially when lifting over an obstruction or small jumps.

[Paul_M3]

Baldchap said:

I think I'm right in saying this is what my Elise Cup came with.

They need management hardware under normal use (box thing on top of battery that apparently ’manages' it) and if left for over a week need to be on a charger according to the manual addendum that came with it. And a special battery charger.

Not had it out so can't comment on the weight.

I've got one on my Exige, and I assume it's the same item.

The box on top of the battery is a protection relay. It's main purpose to to stop under-voltage. Basically if the battery starts to get really low it automatically disconnects it from the car to stop it discharging further. Once 'reset' there is still some life in the battery.

The main (only?) benefits are weight and small dimensions. The one in my Exige is around 250 x 100 x 150mm and weighs about 4kg. If you've picked up a decent sized lead acid battery, you'll know what a big difference that is.

Mine is a 25Ah one and lasts approximately 2 weeks if the car is sat there not being used with the alarm and immobiliser armed.

[Mr Miata]

I’d be interested to see what % of the cars weight you save by replacing the battery.

In road cycling, people were spending £1000s on carbon fibre components, just to save half a Kg. We would joke, you’d have saved more weight by eating healthy.

[Simon54]

Mr Miata said:

I’d be interested to see what % of the cars weight you save by replacing the battery.

It's not to save weight... at least that's not what my post was about. It's to gain extra capacity for the same volume. The battery compartment is usually a specific size on most cars, if you want more, you either change chemistry, or start filling up valuable interior space with extra capacity (with all the safety implications of that).