I tore down the battery from my 2005 Prius and tested all the cells all of them were 7.8 except three. One was 7.7, 7.6, and 6.5. I was planning on replacing them all with ones that measured 7.8 but am having a difficult time finding ones that are 7.8. Is there another option for those 2 cells and I know I need to replace the 6.5 cell but what if I can not find cells that are 7.8? I would like them to all be balanced correct? I know I can discharge and recharge the 7.6 and 7.7 but am concerned they will not hold at 7.8 or will be unbalanced. Advice or recommendations. Thank you. ?
I'm assuming you don't have a grid charger to charge/balance the entire pack. The voltage is just a state of charge. It's really hard to tell the actual health of a module. If you could find a way to load test the ones that are .1 off and they held I would just use them. Also I've found it helps to put the weaker ones towards the outside of the pack to keep them cooler. Also cycling the entire pack is really the proper way to do it but I understand that takes certain equipment not everyone has.
Have you load tested the modules? Resting voltage is not a good indicator of module health. You can build you own load tester or we offer an inexpensive one here: Prolong™ Battery Module Load Tester - Hybrid Automotive It would be wise to recondition the pack before testing and after replacing any failed modules. This allows you to perform a proper diagnosis and ensure replacement modules are in sync with the rest of the battery pack.
No, I do not have a grid charger to balance the entire pack. I assume that is pretty expensive? I am just a nurse who watched some you-tube videos and decided to try to save some money by doing it myself. Thank you for your advice I will look into it. The other option I had was buy a used battery pack from a scrap yard from a newer lower mileage Prius but it was still quite expensive.
Less than $400 for everything needed to recondition the battery without having to remove it from the car. Then you get to keep the hardware and properly maintain the hybrid battery for the rest of the life of the vehicle : Prolong™ Battery Reconditioning Package - Hybrid Automotive
Read this tread in its entirety & take notes. All questions will be answered. Gen II Prius Individual Battery Module Replacement | PriusChat Module replacement is a band-aid fix. Other modules will fail, just a matter of when. Murphy's Law will have it fail at an inopportune time (road trip 100s of miles away from home). Hope you live work close to home or have a 2nd car to use when rebuilding.
Battery reconditioning in not a one time event! If you follow the advice in that thread, remove the battery pack, tear it down, cycle each module, then reassemble and reinstall the battery, never to maintain it gain, then yes a one time battery reconditioning is a temporary fix that will not last. It will also takes you weeks to complete the process. If you use our products which allow for in car battery reconditioning, the reconditioning process will take a weekend (if no modules need to be replaced), or two weekends if you do have to replace modules. The key difference, however, is that you continue to treat the battery by re-balancing the cells every three months and reconditioning the pack every six months. This is all done without ever having to remove the battery from the car. By regularly maintaining the battery and not ignoring it, you can easily extend it's life for the remaining service life of the vehicle. We have thousands of customers around the world who are already doing this. Here is a recent comment from one of our Gen2 Prius customers: "Thought I would let you know, I reconditioned the battery . . . it worked great, I have more power on take off and the battery indicator now only goes down to the half way mark, and charges back to full, very quickly. It now shows a full charge at times, where it would commonly be half to almost discharged (most of the time) during driving, it doesn't go below half now. My mileage went from 40 to 45 mpg to 49 to 54 mpg (and in cold weather I usually seen 37 to 39 mpg). It averages around 52 mpg and it is cold here in Tennessee, I NEVER seen that kind of mileage in cold weather, EVER. your product is great! And a great investment. This is an 8 yr old battery with no indications of being bad. Thanks again -John R"
