So I wonder if it's possible to build a hybrid battery, maybe 20x 12v 10ah batteries in series? Based on Dr.Prius, an app that shows battery voltage, and charge/discharge information, I found the battery in my 2009 Prius normally ranged from 230v to 270v depending on its discharge/charging state and amperage, and the max discharge amp I have seen is 50amp. The max charging amp is 70 amp. Is it possible to mix and match 12v lifepo4s or cells to make a Prius battery? Or even convert it into a PHEV and charge off solar.
DIY 12v LifePo4 to replace Prius hybrid battery?
- Thread starter Riley
- Start date
Don B. Cilly
Energetic energy padawan
To make 240V nominal - 280 charged - you would need 80 LFP cells.
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Vigo
Solar Addict
The approach that would require the least amount of re-engineering of the car itself is to simply interface with the existing battery through a dc-dc converter rather than replacing it entirely. In that way the pack voltages don't need to match and whatever the car needs to sense/measure from the original pack is still in place. If the dc-dc conversion is bidirectional it would also be 'self-sufficient' in the sense of not NEEDING to plug it in to charge the added battery, and it would just act as a hybrid with a larger battery pack, with the caveat that the limit of the dc-dc conversion would likely be much lower than the power limit of the original battery to inverter. As in, if the original battery could give 20kw to the inverter and your dc-dc is only capable of 3kw or something like that, it would average out that the car acted as if it had a larger battery, but if you you floored it for a long time or did regen down the side of a whole mountain it would act like a stock car with a slightly larger battery because you'd be outpacing the power transfer capability between the two packs. So it would be a compromise approach for sure unless your dc-dc conversion capability was huge.
There is a company thats been doing something like this for a long time, if you want to look into it. https://www.enginer.us/products/
I had an 09 Prius, and ive had 4 other hybrids. I think the main limitation of trying to make a gen2 prius into a phev is that you're still limited to the 'ev performance envelope' it has, regardless of range. Which is that on electric power alone it can accelerate gently up to 39mph max, and that's all there is. So putting a huge amount of battery in it is dubious unless you are actually going to do a lot of driving under 39mph. The rest of the time it's just making it a 'better' hybrid and pushing up its mpg some because it can use more battery power for assist and regen, and it doesn't take PHEV levels of battery capacity to accomplish that!
There is a company thats been doing something like this for a long time, if you want to look into it. https://www.enginer.us/products/
I had an 09 Prius, and ive had 4 other hybrids. I think the main limitation of trying to make a gen2 prius into a phev is that you're still limited to the 'ev performance envelope' it has, regardless of range. Which is that on electric power alone it can accelerate gently up to 39mph max, and that's all there is. So putting a huge amount of battery in it is dubious unless you are actually going to do a lot of driving under 39mph. The rest of the time it's just making it a 'better' hybrid and pushing up its mpg some because it can use more battery power for assist and regen, and it doesn't take PHEV levels of battery capacity to accomplish that!
MacLeod
New Member
I have 560 3.2v 26650LFP cells running my 2008 Prius. I obtained several 64V 20s4p banks and have 7 of them installed 3 parallel. The module leads on the harness are connected to every 5th row (16V vs 14.4). I modified the harness to reach the locations of each “module”. Modest gains in mpg ~38 to 43mpg. I drive with a very heavy foot. Car has 251k miles on it.
Vigo
Solar Addict
Very cool!!
I briefly owned a Highlander Hybrid awd which i sold to my cousin.. And ever since i've gotten more comfortable 'altering' high voltage systems i've been secretly hoping he'll decide to upgrade so i can get it back and increase its battery capacity. It was never particularly fuel efficient but it is a type of vehicle which could perform ~95% of all the tasks i do with my vehicles (i do tow heavy occasionally) and since it runs ~low 15s in the 1/4, it is actually fairly entertaining to goof off in. I can't recall what its top 'ev speed' is, but my commute to work is all <45 as far as the posted limits go.
I had a GS450h which i DID tow cars with (23mpg highway towing a car!) and which was very nearly as fast as the 1999 porsche 911 i had at the same time, but strangely even though it was an excellent vehicle that i didn't let go of by choice, i haven't had much interest in having another one, and it might be down to the fact that i wouldn't tinker with it as much (as the highlander) if i had it!
I briefly owned a Highlander Hybrid awd which i sold to my cousin.. And ever since i've gotten more comfortable 'altering' high voltage systems i've been secretly hoping he'll decide to upgrade so i can get it back and increase its battery capacity. It was never particularly fuel efficient but it is a type of vehicle which could perform ~95% of all the tasks i do with my vehicles (i do tow heavy occasionally) and since it runs ~low 15s in the 1/4, it is actually fairly entertaining to goof off in. I can't recall what its top 'ev speed' is, but my commute to work is all <45 as far as the posted limits go.
I had a GS450h which i DID tow cars with (23mpg highway towing a car!) and which was very nearly as fast as the 1999 porsche 911 i had at the same time, but strangely even though it was an excellent vehicle that i didn't let go of by choice, i haven't had much interest in having another one, and it might be down to the fact that i wouldn't tinker with it as much (as the highlander) if i had it!
Any issues in the cold? Any fooling circuitry or other modifications? What did you need to modify the harness for?
I have an aging 08 Prius with a good but ticking time bomb NIMH battery, I’ve seen some kits they sell for lifepo4 replacements but they want 2100 for it and it’s often sold out. LTO seems like a great alternative if it could fit and work.
Vigo
Solar Addict
Color me curious too. I have my old 2007 Prius back for repair (just replaced the inverter with a $200 used, due to a failed current sensor) and at 410k miles and no known battery replacement it is only 'technically' functional on this ancient battery.. gets the mind wandering over such topics as this lol.
sunshine_eggo
Happy Breffast!
202V nominal. Need 14X 5S submodules; 70 cells.
This is similar to an existing solution, 5S modules replacing the NiMH 12S blocks. Have you had any issues with cell failures? Do you have actual BMS controls, or are you balancing?
The mpg improvements are likely due to a greater utilization of the battery capacity due to the flatness of LFP vs. NiMH.
The existing commercial solution has continuously evolved to address more and more issues as it becomes readily apparent that the implementation is marginal at best. For DIY, fine. For charging more than a new Toyota pack in some cases? Criminal.
PROPER lithium conversions use an intercepting computer that feeds the car's NiMH BCM with the NiMH data needed to treat the Lithium properly. The commercial solution you have located didn't do this.
I have personally touched the commercial solution, and the battery failed inside of 6 months in a Prius C.