12V battery substitute: $99 LiFePo4?

I'd be concerned with these two specifications for using it as a replacement to the 12V battery.

Max Charge Current: 9A
Max Discharge Current: 15A

 

optima or toyota oem.

 

Looks like the battery I use for back-up on my house's alarm system. With those terminals, it's not for a car.

 

This is a 9 a-h battery...about 25% the size of the OEM 12v battery. It is not going to work unless you use four of them. Additionally, LiPo batteries use a different charging scheme than lead-acid and may not be compatible with the existing system.

 

If u need a battery let me know. I work for a company that provides backup power for datacenters so we buy dozens if not hundreds of batteries every month from various vendors, so our cost should be better than anything out there. I bought an Optima for my GenII six months ago and it was like $175 (no tax cause of our resellers license) and it was at will call at the closest distribution center the next morning. Anyways, if u are interested, let me know and I can ask my vendors, and give me a heads up on what it is u need...

 

Most of the accessories use 12v. They run off of the battery, which is then recharged thru a dc-dc converter from the HV side. A 9 a-h battery doesn't have enough capacity to run very much if the engine is off, and you will need an external jump to start the car if it runs down.

 

Hello everybody! Would a LiFeYPo4 battery work as a substitute? Dimensions and charging behaviour are similar for Winston 40 Ah 12V, but it weighs less and has more capacity.

 

As a 12v battery in the Prius plays a bigger role than most "normal" cars, I wouldn't try to skimp or save on it too much. I went with an Exide which has the same specs as the Toyota Yuasa unit. The people in the US seem to replace with the Optima, but there have been the odd issue with them recently as I've read here. If the OE unit lasts for 5+ years, that's not a ba one to go for again. I saved money by fitting it myself rather than pay and hour or two labour in the garage

 

Bigger role? My impression was that it's almost like a bios battery in a laptop No need give massive currents to start the ICE, and charging with DC-DC converter is also much more civilized compared to alternator of a normal car. Lithium alternatives aren't cheaper actually, but they have other benefits.

 

This kinda reminds me of the transaxle fluid. Owners Manual says use fluid A. No ifs, ands or buts. Just use that, nothing else. We're warning you... Owner's response:

How about this other stuff?

 

It's up to you at the end of the day. I went with an Exide as they're recognised as a good brand here in Ireland and also in UK. I can get considerable discount on the Exide (cost less than €70), so went with it as it's specs were better/same than the OE one, only alot cheaper for me.

I just gave my opinion, I don't know what the GWL batteries are like as I don't think that they're sold here in Ireland, maybe they're a known brand in Finland
73

 

Well 70 € or below is such a low price that it's easy to understand your position. Battery technology marches on though, and maybe in a few years we could see even some known brand to advertise lithium-based start batteries as a premium alternative. Time will tell. Thank you for input!

 

Any thoughts on the EarthX ETX680C or other such batteries? And by thoughts, I mean data. "Stick to the recommended" is covered. We get it, but new tech is available that wasn't available when my manual was printed. What specs are we looking for? I see people ruling out the specs posted by the OP but not saying what the specs SHOULD be. Can anyone be more specific? I've read that the original (Yuasa?) was around 38AH or so, but I've had no luck determining what the charge current applied to the 12v from the DC converter is. Something less than 100A is all I can dig up.

 

It's "posts" are completely imcompatible with the stock cable clamps. Being described as a "motorcycle battery" I'd guess it doesn't have the proper vent port?

 

Charge and discharge currents are a question mark. Toyota does not specify maximum currents, so we must quess. There is a 200 A fuse for the battery, so that's an absolute upper limit discharge current. In practice you do not have to reach 200A discharge current as LiFePo4 would not fail with overcurrent. Also maximum discharge would happen when the car is not in fully-on-state and you have all accessories running. I find it hard to belive that the power consumption would be over 2kW (maybe with DC-AC converter).

Charge current estimate depends more on battery chemistry. Toyota does constant voltage charging around 14.7 V (sometimes the charge voltage drops, but it is still constant voltage). There is also a current limit at some level (I do not know exactly), but it is likely shared with other 12V sinks. If your LiFePo4 battery is near full, there is no problem with charging current. But if it is near empty, there could be issues

I have now driven a little bit over one month with Winston 40Ah battery - all fine for now..

 

Thanks Mendel. John Frum cargo cult? Fascinating. I'm focusing now on the EarthX etx680c battery, which has automotive applications. Being Lithium, it doesn't vent anything. Unless it blows up. The terminals are different. Not a real barrier.

Thanks, Jarkko. ChapmanF referred me to this post which seems to reliably peg the charge current at 60A. Maybe 70? 60A and 15V are the upper limits for the EarthX battery. Its rated at 36AH "Pb equivalent" (12.4AH actual). That, too, seems within spec, and since it's 1/2 the size of the spec battery, it looks to me like a legit drop-in (with terminal mods) replacement. Am I wrong?

You make a good point about HOW a Prius USES the 12v, Jarkko. You obviously know a lot more about electric sorcery than I do, but I was mulling similar thoughts over and sent an email to EarthX asking for advice.

 

Thanks Mendel. John Frum cargo cult? Fascinating. I'm focusing now on the EarthX etx680c battery, which has automotive applications. Being Lithium, it doesn't vent anything. Unless it blows up. The terminals are different. Not a real barrier.

Thanks, Jarkko. ChapmanF referred me to this post which seems to reliably peg the charge current at 60A. Maybe 70? 60A and 15V are the upper limits for the EarthX battery. Its rated at 36AH "Pb equivalent" (12.4AH actual). That, too, seems within spec. Since it's 1/2 the size of the spec battery, it looks to me like a legit drop-in (with terminal mods) replacement. Am I wrong?

You make a good point about HOW a Prius uses the 12v, Jarkko. You obviously know a lot more about electric sorcery than I do, but I was mulling similar thoughts over and sent an email to EarthX asking for advice. Stay tuned.

 

A thought on the Lead-Acid (LA) equivalent concept, and how it applies to Prii: For those wondering, LA equivalent refers to the fact that regular ICE cars depend on high-draw starters. At ~ 70% charge a LA battery doesn't have the voltage to power a starter. Lithium functions down to about 5% charge, and is thus equivalent to a bigger LA battery for high draw use.

Since a Prius 12v battery only sees light loads (computer, stereo, etc) which I'd GUESS stays below 5 or 10A, the equivalency factor might be less important in relation to the real AH rating. Disclaimer: I'm not an expert, I'm just piecing this info together. If my logic is logical, something like the ETX900 (16AH) or ETX1200 (24AH) should be a better fit. $725 for the latter, FWIW.