Ohmmu LFP battery in a Gen 5 Prius ?

I'm curious, why are so many people swapping out their 12v so soon?

I run a 700W RMS amplifier (4x50W @ 4ohm, 1x500W @ 2ohm) and the stock 12v keeps up without a sweat.

 

Nah, but I do have my cig port USB adapter that shows voltage. Have had it since my last car and on my last car it measured just 0.12v lower than what I measured at the battery with a multimeter. Didn't bother to test it vs this vehicle because there's likely not enough distance in wire run vs my old car to make resistance a notable factor.

Never seen voltage dip below 12.4v, when it stops charging it'll sit around about 12.7v for what I assume is load testing, 14.x for charging, and the very rare 13.x.

And while I'm definitely not maxing out how loud my amp can play so I'm not hitting those wattage ceilings, I'm still using far more juice than the stock head unit.

Car has also sat for 2 weeks not started at all, battery was fine when I got back.

IMO changing the 12v early is burning money. But I'm sure I'll move to a lifepo battery once this 12v gives up.

 

Not a Prius nor so new, but on my 2013 Avalon Hybrid I installed a 100Ah Li Time battery even though I had a new (and very expensive) OEM battery put in there not that long ago.

But my excuse is I'm an amateur radio operator, and I want more run time without idling the car.

 

• It barely fits where the OEM battery goes (in the trunk).
• It seems to charge just fine. Although the good thing about the trunk is the cable seems so long it helps lower the charge current. I can have up to a volt difference when the battery is really low, 14.4V at front of car and 13.4V at battery.
  
• So far the BMS hasn't shut down the battery in any way.
  
• The BMS has freeze protection and a heating circuit that will kick on during charging. I have yet to see how it performs in the winter though. And I get very cold winters. Some claim this is the coldest town in all of Colorado. I've seen it get down to -40°F/-40°F several nights in a row with -20°F almost guaranteed to happen at some point during every winter. We have had freezing weather and a couple of overnight snow storms already and so far it hasn't caused any problems. It starts up just fine in the morning.

 

The 12-V battery has nothing to do with whether the 12-V system can keep up with the wattage of an aftermarket audio—unless you are listening to the audio in the ACC mode, which you shouldn’t. As explained in the Gen 5 new-car features manual, when the load on the 12-V system is too high, the DC–DC converter will switch to 14.30 V to prevent a system instability. I also see that when I bring the electric power steering to a stop or turn on the No. 921 16 W + 16 W = 32 W miniature incandescent backup light bulbs by putting the gear shift in reverse, both of which increase the load on the 12-V system and cause the DC–DC converter to produce 14.1–14.3 V.

As far as whether a 12-V LFP battery would work with the Toyota 12-V-battery-management system with a battery sensor in 2016-plus-model-year Toyotas, I don’t know, and you would have to try it.

In any case, using a battery monitor and, more importantly, occasionally using a battery maintainer and definitely using a battery maintainer when the car is not driven for more than a few days will prevent any 12-V battery problems with either a flooded-cell battery or an AGM battery, the latter being an upgrade over the OEM flooded-cell battery.

 

Correct. I have no idea how much space is in a Gen 5 Prius for the 12V battery, so one will have to do their own research. I do believe that Li Time has come out with a smaller 100AH battery with all the features mine has IIRC. I still have no idea if it would fit in a Gen 5 Prius or if there's a way to make it fit.

For the record, the 12V Li Time battery that I put in my Avalon did not fit very well. I had to get a longer bolt for the battery clamping brace that goes over the battery, and I had to bend it so the rear nut would go on the threads. I also had to bend the tray it sits on as it's longer than the tray would normally allow. It also sits in there a little angled. But after all that it does fit in there with the battery compartment door closed.

Yes, I imagine it's a lot of current. But the battery has current protection and so far it hasn't been enough to trip the current protection. I suspect that the length and gauge of the battery cables (that go from engine compartment to the trunk of car) help keep that current from getting so high it messes with the current protection on the battery itself. I mentioned this since someone with a Gen 5 Prius may have a different situation that might over current on a battery like this one.

Yes, the Li Time battery has a heater that kicks on only when charging, IIRC. It also has two cold weather protection circuits. One turns off charging when below a certain temperature (battery will still start car, just no charge until heated to acceptable temps). The other shuts down the battery completely when it gets too cold. At worst, I'll need to come up with a 120V battery charger that works with this battery that I can plug in overnight so the heater will turn on and keep the battery above 40 °F. Either that or a separate heater, again, only if the battery ever gets cold enough that I'm having trouble from it shutting off and not starting the car.

 

No, although Li Time does sell ones that do have a Bluetooth connection

For an example: 12V 100Ah Bluetooth Lithium Deep Cycle Battery with Self Heating – LiTime-US

 

Interesting info. Nice that they have ones specific for cars. I got the Li Time based off of Will Prowse's recommendations. I don't see any reviews from him on the OHHMU batteries. The Li Time batteries are not rated as car starting batteries, but of course we're not running starters with these batteries in our hybrids.

 

Gen 3 did not have a 12-V-battery-management system with a battery sensor. It worked like old cars, charging the battery at all times. Gen 4 and Gen 5 do have a 12-V-battery-management system with a battery sensor and employ a complicated miserly algorithm to charge the battery. An LFP battery has its own battery-management system, which normally expects a constant 14.3 V as the input. You would be running it under the battery-management system of the car instead, which reduces the voltage to as low as 12.85 V at most times. As a result, I don’t know if an LFP battery would work in Gen 4 or Gen 5. It is not to mention that it has different dimensions and terminals, which could result in mounting issues. If you try it, let us know.

The Gen 4/Gen 5 battery-management system likes to keep the 12-V battery at around 12.70 V for an AGM battery and around 12.50 V for a flooded-cell battery. This is under 20% SOC for a 12-V LFP battery. So, I doubt an LFP battery would work unless somehow the system is also capable of detecting and managing an LFP battery with a built-in battery-management system.



In any case, it is far more practical to employ a battery maintainer occasionally and when the car is left undriven. My OEM Gen 4 battery actually lasted fine for four years, and it would still be in good shape if I hadn’t left the car undriven for six weeks last summer. It was even still charged when I left it undriven for four weeks last year. In fact, it still works, but I have replaced it out of caution because of the 100% discharge it endured last summer.

 

It got down to -1 °F last night, and my car started just fine. The LiFePO4 BMS protection circuit didn't shut off the battery completely from the battery getting to cold. It seems to have self-warmed up and then charged back up just fine.

 

Sounds like I'm never going to get a newer Toyota hybrid. I don't want to be stuck with LA batteries. And in my case, part of the reason for putting in an LFP on the car's charging system is to avoid having to need another means of charging it.

 

Update. My self-heating LFP Li-Time battery seems to be doing just fine in the bitter cold. It's been getting down to below 0 °F, usually around -5 °F in the mornings, and not getting above freezing all day long for the past week or so. And the car starts up just fine. I guess we won't know if this is causing any long term damage, but seeing how the battery should be shutting off charging and even discharging if the temperature gets cold enough I don't think there's any problem.