Hi all, I am considering building a Li-ion battery pack that would be fitted in the trunk of a 2007 hybrid Lexus GS 450H to get a real electric range. This pack would come in addition to the original NimH 288V batteries located behind the rear seats. My budget limits me to around 2000 18650 batteries. I would appreciate any comment on that project. I am still wondering what P and S configuration would be better. Also I am not sure about the additional range this would provide, and what kind of BMS would be required, or even if one is really needed, as we can find so many contradictory information on that subject. Of course I would like to drive electrically at any speed without the car to switch automatically to gas so I guess a mod is required. Thanks for your help !
Lexus GS 450H plug-in
- Thread starter herg
- Start date
Hillhater
100 TW
Hi Herg,..welcome to the forums.
Do you know what the "condition " is of your current standard battery pack is ?
Those Lexus packs seem to have a mixed reliability and unpredictable life. If you're is the original one fitted to the car it could be near the end of its life and will not be wise to try to connect a new pack up in parallel to a potentially problematic one. It could kill both !
But back to your question.. The maths of arranging 2000 18650 Li cells ( typically Panasonic as used in Tesla) ..is not complex. You have to match the existing system voltage ..288v.. So that would be 76 Series and hence 26 Parallel.
That would give you approx a 25kWhr pack, ( if you used 3.4 Ahr cells), which should be enough for a 50+ mile range depending on driving and road conditions.
BUT... That is the easy part, making the "extender" pack connections and effective working with the existing system may not be easy. As you say you may have to modify some control functions and programming....unknown area !
Have you searched the hybrid forums, there may be some prior experience there.
PS.. What cells did you plan on using and what cost did you budget for them ?
PPS... You will have to SERIOUSLY. Rethink the charging systems .
EDIT.. Thinking about this, matching the working voltage range of these 2 packs may be tricky,
..and with the limited capacity of the NmHi pack, and it's weight/size, it may be better to simply remove it completely ( especially if it is 7-8 years old.) it can only give 1-2 miles max extra range !
....you may even sell it for a few hundred dollars ! ...and buy even more 18650s :wink:
Use the space for the new pack and simplify the install.
Do you know what the "condition " is of your current standard battery pack is ?
Those Lexus packs seem to have a mixed reliability and unpredictable life. If you're is the original one fitted to the car it could be near the end of its life and will not be wise to try to connect a new pack up in parallel to a potentially problematic one. It could kill both !
But back to your question.. The maths of arranging 2000 18650 Li cells ( typically Panasonic as used in Tesla) ..is not complex. You have to match the existing system voltage ..288v.. So that would be 76 Series and hence 26 Parallel.
That would give you approx a 25kWhr pack, ( if you used 3.4 Ahr cells), which should be enough for a 50+ mile range depending on driving and road conditions.
BUT... That is the easy part, making the "extender" pack connections and effective working with the existing system may not be easy. As you say you may have to modify some control functions and programming....unknown area !
Have you searched the hybrid forums, there may be some prior experience there.
PS.. What cells did you plan on using and what cost did you budget for them ?
PPS... You will have to SERIOUSLY. Rethink the charging systems .
EDIT.. Thinking about this, matching the working voltage range of these 2 packs may be tricky,
..and with the limited capacity of the NmHi pack, and it's weight/size, it may be better to simply remove it completely ( especially if it is 7-8 years old.) it can only give 1-2 miles max extra range !
....you may even sell it for a few hundred dollars ! ...and buy even more 18650s :wink:
Use the space for the new pack and simplify the install.
And don't forget that normally, NiMH drops in voltage once it reaches full charge, and dissipates that excess charge as heat (this is how it "self balances"). So if your new pack is paralleled directly with it, and it charges to a higher voltage than the "balanced and fully charged" NiMH pack voltage, then it will also dump *it's* energy above that voltage into the NiMH pack, causing even *more* heat, and potentially causing a fire.
So you might well be better off replacing the NiMH pack entirely, than paralleling to it.
If the present NiMH pack isn't balanced by doing that type of full charge, and is never brought up to the point at which it then drops in voltage, then this may not be an issue, but it is a primary reason why it's not recommended to parallel NiXX-chemistry packs together.
So you might well be better off replacing the NiMH pack entirely, than paralleling to it.
If the present NiMH pack isn't balanced by doing that type of full charge, and is never brought up to the point at which it then drops in voltage, then this may not be an issue, but it is a primary reason why it's not recommended to parallel NiXX-chemistry packs together.
Paralleling even indentical NiMh packs can be dangerous for charging. I don't think you could parallel a LiCo and NiMh and safely charge them together.
It's an interesting car (not looked at them before). What sort of continuous power do you hope to get from the motor in EV driving mode?
It's an interesting car (not looked at them before). What sort of continuous power do you hope to get from the motor in EV driving mode?
Hi, did you manage to build your pack? I want to do the same for my lexus but replacing the old batteries with lithium ones.
I am not sure what software or hardware needs to be tinkered with to get the system to accept the lith batteries without throwing errors. I would also want the engine kick-in speed to be increased to maybe 70 mph??? if anyone has done it please drop a note
I am not sure what software or hardware needs to be tinkered with to get the system to accept the lith batteries without throwing errors. I would also want the engine kick-in speed to be increased to maybe 70 mph??? if anyone has done it please drop a note
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