Ohmmu LFP battery in a Gen 5 Prius ?

Update with the LiTime battery:

We hit some serious cold here, down to the negative thirties for a couple weeks straight. What I learned is if I shut off the car for about 8 hours, running it just before getting into bed and then just as I got out (and yes, running out there at -35 °F in my pajamas) and turned on the car, the battery would hold enough heat to not shut down completely even at those very cold temps.

At around -10 °F to -15 °F it seems kind of hard to get it down cold enough to get it to shut off with driving the car home at around 4 or 5pm the previous day and getting in and starting up at around 6 to 9am the next. Only if you leave it off all day and all night does it become a problem at those temps.

If it's just going to dip down to -4 °F or -5 °F or so in the morning, it's seemingly impossible for the battery itself to get that cold and shut off.

• So all in all, if it's getting down to -10 °F to -20 °F, then I make sure I'm driving the car at some point the afternoon before.
• If it gets down from -20 °F to -35 °F, then it's important to do something like run the car before bed and after getting up, because when you don't then you're going to have to jump start the car with another battery, which also seems to work too, it just resets all your car's computer stuff.

 

Have you tried a trickle charger to see if that will kick on the batteries heater while the Avalon is sleeping?
Do the specs say what kinda charge the heater needs before it switches on?
It's a balmy 17 F today and I keep the Prime plugged in a LOT to keep those traction heaters on alert.

 

So, an LFP 12-V battery doesn’t really work in cold? Great.

 

Outside.

If you live where it gets down to negative 20 °F and below, you park outside all night and you're not willing to do something about it, no.

 

You asked if I park outside. I don't have a garage, so yes, I park outside, all night long. So yes, I was able to get the car through the night outside with it as cold as -35 °F and the car still started the next morning. All I needed to do was run the car half an hour before bedtime and then go out and start the car early. An appropriate battery charger would also keep this self-heating battery warm all night.

@Gokhan indicated that LFP batteries won't work in the cold. But as I've demonstrated, they work just fine down to around -15 °F. So if you don't get down past that, you'll probably never have any problems.

 

This one: LiTime 12V 100Ah Self Heating LiFePO4 Lithium Battery – LiTime-US, but no, it does not fit in the stock battery holder. Mine is wired to be in the trunk. I'm not sure of the dimentions of the stock battery, but LiTime does have a newer self-heated battery that is smaller, group 24 sized battery that might fit, although I have my doubts.

 

The real risk to most Li-ion batteries in the cold is with charging. Do so when the battery is below freezing, and damaging it is possible.

 

This is quite true, and why I got a self-heating battery that shuts off charging when it's below some 40 °F but still discharges through a diode unless the battery itself gets down to -4 °F, at which point it shuts off completely.

So usually it starts the car fine, then the charging current of the car just warms the battery warmers until it gets warm enough to start accepting the charge for the battery itself.

 

These cars are at most 2 years old. Why would you be spending $$ to replace a fine battery? Is your stock battery dying frequently?
An expensive LFP is not going to fix that.

I swear, sometimes it's like young boys gluing on chromium geegaas from another model just because they like to modify/personalize their toys.

 

If it isn't broke don't fix it.

In my case I use mine for amateur radio and having about 4 times or more the battery capacity comes in handy for me.

 

Have you been monitoring its voltage with a BM2? An LFP battery might be running at a very low SOC because I doubt the car’s BMS/DC–DC converter is compatible with it.

Ohmmu LFP battery in a Gen 5 Prius ? | PriusChat

 

Your chart seems about right for modest charging but maybe a bit off for resting voltages. I get 13.1V resting voltage at 100% charge.

Then again, it's pretty cold here, so the voltage may be lower than normal. It's snowing again as I type this.

 

I am also considering the Y1230P-4G-BH LiFePO4 from OHMMU. It is supposed to be a replacement for the current Prius AGM. I have read most of the following replies to this thread. It is possible that the battery management system (BMS) which is set for an AGM might limit the current preventing this battery from reaching full capacity. However, the existing system will not bring the AGM back to full capacity either, since it lacks an absorption phase (constant battery voltage of about 13.5 maintained by adjusting the current until the battery will no longer accept current above 1 amp or so). Capacity is being lost each time the battery cycles down below 12.2 volts and remains there for any length of time due to sulfation. The BMS does not seem to be designed to replenishing capacity and guarantees short battery life. The only solution to preserve this batttery would be to connect it to a "smart" charger after each use.

The advantage of the LIFePO4 battery is that it does not sulfate and can handle those deep discharges that are going to occur with the Prius hybrid when it is parked for any length of time. My original 8-month old AGM would drop down to 11.7 volts overnight. My 2-month old AGM dealer replacement drops down below 12.2 volts every evening, so it is in a death spiral as well. The LiFePO4 will handle deep discharges far better then the AGM. My only concern is that their maximum charging voltage is 14.6, about 0.1 volts lower than the AGM. However, I have never observed more than 14.5 volts in my AGM. Also, the LiFePO4 battery has its own BMS that should prevent the voltage from exceeding 14.6 even if the Prius BMS tries to drive the voltage higher. Moreover, I have read that the Prius BMS for the AGM is the same one used for their flooded battery. If so, it is not optimized for the higher AGM charging anyway. As I mentined above, others have suggested that the Prius BMS may not allow a sufficient rate of current to fully charge the LiFePO4 to capacity. But as this battery can survive at lower capacity without sulfating and would still proivide 12.8 volts when down to 20% capacity. I think it is a much better choice for the Prius hybrid than the AGM. I think Toyota will have to eventually switch to this battery and hopefuly provide a BMS optimized for its charging.

I just joined "PriusChat" today. jamesgates