Winston 12V 40Ah LFP battery, good or bad idea??? - Fuel Economy, Hypermiling, EcoModding News and Forum

Isaac Zachary · 10-02-2023, 01:36 PM

I need a 12V battery for the 2006 Prius. My thoughts are either go with a battery from Toyota, or I'd like to try lithium ferrous phosphate (LFP, AKA: LiFePO4).

I found a 40Ah one from a brand named Winston that looks to be very similar in size to the Prius battery. However, one of my concerns is cold weather. With Lead Acid (LA) you don't want to let the battery drain or it can freeze and even rupture. But since a car ususally will keep the battery topped off, this may not be a problem. LFP's, though, usually are damaged from cold weather, mainly when charged (discharging might not affect them in freezing weather). But Winston advertises they can work in -40 °F (-40 °C) weather without damage by means of a special chemistry. And we sometimes see weather down to -40 °F (-40 °C) around here on occasion, although not as often as in the past. I am contemplating getting a battery warmer too, just because. Also, being more inside the cabin, as opposed to being under a hood, seems like a better place to keep it above freezing during a sunny day, right? Or am I wrong?

Am I right about dimmensions too?
OEM:
220mm x 235mm x 127mm

Winston:
225mm x 208mm x 125mm

The Winston is also about $239, before tax and shipping. I'm sure there are cheaper options out there, but this is the only LFP advertised to work in the cold. Any thoughts on if I'd just be better off with an LA?

One reason I like the idea of LFP is I'm also into amateur radio. If I get a radio into this car, having more usable Ah's would be important. This is also my second car, and depending on how it goes, I might get an LFP for the Avalon hybrid, which does have a 100W HF/VHF/UHF transceiver installed. LFP also keeps the voltage closer to 13.8V, the perfect voltage for a typical transceiver, and it can do that without the aid of potentially noisy voltage converters. This is why LTO wouldn't seem like a good alternative.

redpoint5 · 10-02-2023, 02:12 PM

I have no knowledge of a chemistry that allows sub-freezing operation. I'd double-check that -40F includes both charge and discharge.

I put a 20Ah LFP battery in the Prius 7 years ago and it has no BMS and no provision for dealing with sub-freezing conditions, and it's still working. That said, it doesn't usually get much colder than freezing, and freezing conditions don't usually last long. The stock battery bracket was capable of securing the smaller battery dimensions.

If you go with that expensive battery, I'd make sure the warranty terms are generous.

My solution would probably be a battery warmer that kicks on automatically when temps drop below freezing, and place the battery in an insulated box. I'd carry a cheap portable jump pack just in case an issue with the battery develops (I do that in all my vehicles anyhow).

This battery looks interesting to me;
https://www.amazon.com/dp/B09H7J9CW7...NrPXRydWU&th=1

I've started taking a practice quiz for getting a radio license. I might be able to pass the test without studying because my electronics experience helps with many of the questions, and I'm a very good multiple choice test taker.

Isaac Zachary · 10-02-2023, 04:05 PM

Quote:

Originally Posted by redpoint5

If you go with that expensive battery, I'd make sure the warranty terms are generous.

The Toyota Dealer battery that I got for the Avalon was about $100 more than that. The reason I went with the Toyota dealer was I tried every single parts store and none had a battery that would fit in the Avalon.

On the other hand, I'd imagine there are more Prius battery options by this point. So on second thought, maybe I'll just go down to the local parts store and try to get the cheapest battery available. After all, I'm not so sure how long I will keep the Prius. I think I'm automotively bi-polar.

serialk11r · 10-02-2023, 04:53 PM

I thought sodium ion, lithium titanate, NiMH, and lead-acid are the only ones that can be charged below freezing, but this Winston does advertise -45C charging...

For a Prius battery I think you might be okay since it's not under much stress.

Isaac Zachary · 10-02-2023, 05:45 PM

Well, I feel a bit stupid. I went down to the local autoparts store and asked if they had this battery. They had one in stock, but I didn't ask the price. When it was all said and done, it was about $205 before tax. I think it only has a year warranty.

Oh well. At least I have a battery now. Now just to fix the wheel bearing, the missing wheel wells, the windshield, the dash that doesn't light up at all, and I'll be set for at least for around town. Then later I can look into the HV battery, if it doesn't throw red triangles first, and the catalytic converter.

redpoint5 · 10-02-2023, 06:00 PM

My aim is to keep the lithium batteries and reuse them in whatever vehicle I drive. I'll put lead acid ones back in the car when I go to sell... except the Prius I already sold to a friend. Told her to call me if the battery ever acts up, and not to take it to a shop.

Isaac Zachary · 10-26-2023, 05:40 PM

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