50Ah lifepo4 starter in 2011 Prius

[tz1280]

My first post. I’m been wondering if it would be advisable to replace my current 5 year old AGM 45Ah with a Renogy 50Ah Lifepo4. I’d also have a PWM (Victron or Renogy) solar controller hooked up to a 100w mono flexible panel to charge when parked as I‘m only doing one or two short trips a week with the Covid lockdowns we’re having in Australia.

My understanding is that the Prius’ DC to DC 70 amp peak converter alone wouldn’t fully charge the lifepo4. As you‘d know, the Prius‘ gas motor is started by the 200v+ traction battery rather than the 12v.

Would I be better off replacing my old AGM with a new 49Ah Panasonic made in Japan AGM or even a cheap Chinese AGM for half the price of the Japanese one rather than the lifepo4. The Japanese AGM and the lifepo4 are the same price.

Thank you for any advice.

 

[Geokilroy]

Be sure to consider the heat in your decision. The starter battery is packed into the engine compartment where all the engine heat is. There is little room for air circulation in there. I have a Highlander hybrid. I know how tight packed the engine compartment is.

 

[MisterSandals]

Renogy 50Ah Lifepo4.

How many amps does your starter require? My money is that the Renogy internal BMS is no where near able to handle those kinds of amps for an engine starter.

 

[mrzed001]

I know it is not the same since this hybrids charge 12V battery with inverter.
But designed for lead-AGM. So I would not put LFP in the car. Here are cold sometimes, lower than 0 Celsius. LFP can not be charged.

Little Toyota/Lexus info:
It is most important to clean the filter for the big battery vent. Under the rear seats.
I just went with my Lexus for a complete cleaning: rear seats out, ventilators out, cells out.
My was OK but showed me pics from dirty and destroyed cells. The main reason for hybrid battery death is bad ventilation.
Also the Prius battery copper busbars have burns sometimes.

 

[tz1280]

Be sure to consider the heat in your decision. The starter battery is packed into the engine compartment where all the engine heat is. There is little room for air circulation in there. I have a Highlander hybrid. I know how tight packed the engine compartment is.

The 12v battery is in the rear of the cabin. i‘m in a temperate climate but it can get hot in summer, especially as it’s always parked in the sun. It does have however a fan powered by a 60 watt panel on the roof that exhausts hot air from the cabin.

How many amps does your starter require? My money is that the Renogy internal BMS is no where near able to handle those kinds of amps for an engine starter.

The 12v battery is only required to boot the car‘s computer when starting. The gas engine starter motor is powered by the 200v+ traction battery. It is said that the Prius can be started with 4 x D cells comprising 12v. With the battery removed, I have started it with a Noco GBX45 1250 amp lithium jump starter.

Thanks so much for the replies. I suspect the Renogy BMS potentially shutting down would be an extreme inconvenience.

it just seems like a wasted opportunity to install a lead acid battery when a lifepo4 is the same price.

 

[MisterSandals]

it just seems like a wasted opportunity to install a lead acid battery when a lifepo4 is the same price.

I'd check on a Prius forum. Its a pretty specific task for general battery questions here.

 

[tz1280]

I'd check on a Prius forum. Its a pretty specific task for general battery questions here.

I’ve been looking around. The consensus on Priuschat is conservative- why risk it with anything but a AGM. There’s a fair bit of technical talk which I don’t have ability or patience to wade through. There is one person who installed a Renogy 50Ah Lifepo4 in his Rav4 hybrid. His conclusion:

Is It Feasible to Use an LFP Auxiliary Battery in a Hybrid Car for Improved Deep-Cycle Performance?

Summary: The use of a LiFePO4 (LFP) 12v battery is only worth considering by a few hybrid car owners: those who drive in mild climates, use power-consuming accessories such as dashcams while parked, and are willing to ensure that battery state of charge remains high enough for safe recharge currents. The capability might be improved by interposing an LFP-optimised charger and return power diode in the 12v circuit, but this would be expensive, and a job for a professional automotive electrician. For most current hybrid car owners, feasibility requires some help from the manufacturer, in the absence of which it is best to stay with the OEM (lead-acid) auxiliary battery. Those who drive at ambient temperatures beyond the 0-40℃ range, and/or do not want deep-cycle ability from a 12v battery, should certainly stay with lead acid.

Reference & Link: Birch RG (2021) Is It Feasible to Use an LFP Auxiliary Battery in a Hybrid Car for Improved Deep-Cycle Performance? https://scithings.id.au/LFP.pdf

https://www.rav4world.com/threads/lifepo4-12v-battery-in-rav4-hybrid.311812/

The Victron video Mrzedd001 posted above was interesting in that it showed just how much more current a Lifepo4 would accept. The Renogy 50Ah has a maximum charge rate of 50 amps which I guess is continuous rather than peak. I’d be hooking up a 100 watt solar panel (only because it’s what I already own otherwise I’d use a 30 watt one.) hooked up to Renogy or Victron PWM controller with a Lifepo4 profile to charge while while it’s parked in the sun so the battery presumably would present to Prius charger as full on start up.

As the RAV4 owner says in his PDF link, if the BMS shuts down you’d risk damaging the Prius electronics. I will probably hook my current dying AGM to the solar panel and keep it at long as I can. It doesnt seem worth the risk to experiment.

 

[lcon123]

** I wish there was another gadget to attach to lifepo4's in a car/12v system to give them the 14.4v volts they need to charge **

Will Prowse, can you do a youtube on this please??

This is an older thread I know, I've just waded into this issue with my prius. I tried an 8ah 12v lifepo4 as a replacement for the 12v agm which was on its last legs. It worked for a few weeks, with one or 2 test drives around the neighborhood. It did finally die after a few weeks even with weekly running of the car at ready/park for 20min. I don't think the lifepo4 was accepting charge from the prius 12v (13.8v I think) charging system. I was able to revive the car briefly with a Li jump starter but the system would abruptly cut off when the jump starter cut off, it wasn't charging the lifepo4 enough for it to maintain the system. Also, a side rant, it's really hard to get to the prius battery in the trunk when the 12v dies, even when you leave the car unlocked the latch only works with power, very poor design decision by Toyota. I wish their latch was more like my Honda's.

 

[cs1234]

I'm using a 50ah Chins lifepo4 in my Prius. No problems so far, at least a year into it. There is a 130amp fuse installed by Toyota right before the battery. I've routinely seen greater than 50amps flowing through the 12v circuit on the Victron shunt I have installed along with the battery.

I don't think an 8ah lifepo4 is a big enough battery for the Prius 12v system considering the amount of amps flowing through it, that 8ah battery BMS is probably constantly turning on and off, assuming it even has a BMS.

Also, just opening the drivers door to the Prius causes it to engage the fuel pump, which spikes the 12v system up to around 30-50amps all by itself if I recall correctly. It takes this entirely from the 12v battery, as it doesn't engage the traction battery to 12v battery dc to dc charger until it's turned on.

 

[wme]

WAG, there are adjustable buck/boost DC converters for under $20. example 150w, 10-32v input and 12-35v output. Will it work????

 

[cs1234]

WAG, there are adjustable buck/boost DC converters for under $20. example 150w, 10-32v input and 12-35v output. Will it work????

I'm having no problems keeping the battery charged with no DC to DC converter. Just using the AGM charge cycle the Prius has by default on it's 12v system. The Prius doesn't use an alternator, but a dc to dc converter/charger built on to it's traction battery 200vdc system. It expects an AGM, but seems to charge a reasonably sized 50ah lifepo4 battery without problems for me.

 

[lcon123]

I'm using a 50ah Chins lifepo4 in my Prius. No problems so far, at least a year into it. There is a 130amp fuse installed by Toyota right before the battery. I've routinely seen greater than 50amps flowing through the 12v circuit on the Victron shunt I have installed along with the battery.

I don't think an 8ah lifepo4 is a big enough battery for the Prius 12v system considering the amount of amps flowing through it, that 8ah battery BMS is probably constantly turning on and off, assuming it even has a BMS.

Also, just opening the drivers door to the Prius causes it to engage the fuel pump, which spikes the 12v system up to around 30-50amps all by itself if I recall correctly. It takes this entirely from the 12v battery, as it doesn't engage the traction battery to 12v battery dc to dc charger until it's turned on.

Great info! So, if there is greater than 50A presented to the Chins 50A lifepo4 won't the bms shut down? And in the process the whole 12v system?

 

[cs1234]

Great info! So, if there is greater than 50A presented to the Chins 50A lifepo4 won't the bms shut down? And in the process the whole 12v system?

The Chins says it can do up to 150amps peak discharge for up to 5 seconds. I haven't seen it disconnect yet. It doesn't have bluetooth though, so I would only be able to tell from weird spikes in voltage/amperage on the Victron shunt logs. I haven't seen anything that looks like disconnects on either the charging or discharging so far.

I charged the battery up on a 12v charger initially before hooking it up, and it's worked flawlessly since then inside the Prius.

I've also used the Prius as a small output generator with a Victron Phoenix 12/1200 for a few days during an outage and it worked without issues. It would turn the engine on and recharge the 12v battery back up as needed, and it never tripped or blew any fuses while running my fridge and freezer.

I haven't measured whether the newer 100ah mini li-time / redodo battery would fit, but if it would, that's the route I would go this time. I only went with a 50ah chins because it was the largest I could find that would fit at the time.

 

[Deveak]

The Chins says it can do up to 150amps peak discharge for up to 5 seconds. I haven't seen it disconnect yet. It doesn't have bluetooth though, so I would only be able to tell from weird spikes in voltage/amperage on the Victron shunt logs. I haven't seen anything that looks like disconnects on either the charging or discharging so far.

I charged the battery up on a 12v charger initially before hooking it up, and it's worked flawlessly since then inside the Prius.

I've also used the Prius as a small output generator with a Victron Phoenix 12/1200 for a few days during an outage and it worked without issues. It would turn the engine on and recharge the 12v battery back up as needed, and it never tripped or blew any fuses while running my fridge and freezer.

I haven't measured whether the newer 100ah mini li-time / redodo battery would fit, but if it would, that's the route I would go this time. I only went with a 50ah chins because it was the largest I could find that would fit at the time.

Interesting, I just bought a gen 2 08 Prius with a bad 12 volt battery. I might give it a shot. Might try a “compact” 100 AH battery.
Did the chins fit tight or did it have more room?

 

[cs1234]

Interesting, I just bought a gen 2 08 Prius with a bad 12 volt battery. I might give it a shot. Might try a “compact” 100 AH battery.
Did the chins fit tight or did it have more room?

It had a bunch of room, but I don't remember in exactly what dimensions. You can't use the built in retention bar and brackets though.

 

[tz1280]

As I mentioned in the OP, I considered a 50ah LiFePo4, but ended up putting in a 55ah Full River AGM (it only just fit) instead. I’ve been camping in it for the last three months and if I don’t start it for a few days, I can flatten the 12v battery. Luckily I have a Noco GBX45 jump starter.

I have 2 generic slimline 135ah LiFePo4 linked in parallel in the space for the spare tire, running a 32 litre Engel fridge and my Macbook and Ipad using USB C PD, and charged by a Renogy 40 amp DC to DC charger.

I‘ve been thinking of ditching the 17 kilo Full River 12v and either getting 4 X 3.2v 50ah LiFePo4 cells, along with a 100 amp or so BMS from Liitokala AliExpress or just connecting the 270ah LiFePo4 batteries to the 12v.