Replacing Modules

Hi and welcome to PriusChat.

In principle, that is sort of what you what you want to do, but as well it is more complicated than that. The trick, however, is to find a replacement module (which is comprised of 6 cells) that closely matches the charge, discharge and capacity characteristics of the remaining 27 modules. If you get that pretty right you might get 3-6 months out of it before you have to do it all over again.

You will get better results by balancing the battery after you have put it all back together, but before putting it back in service.

You balance the battery by doing an initial charge and then a series of discharge/charge cycles. You can do this using a grid charger/discharger to do all modules together as one (i. e. the whole battery) or you can do each module individually using one or more hobby chargers. Obviously the grid charging is easier and quicker. If you take the time to balance the battery, if will most likely last the longest between repairs. However, it is not an exact science, so YMMV.

The best repair is to replace all modules with new ones, the next best repair is to replace all modules with ones from a late model low milage wreck, if you can get one. You can use modules from a Gen 3 and transplant them into your Gen 2 case.

Hope that helps.

 

Since you are DIY the best solution in my opinion would be the $1600 kit of new cells from @2k1Toaster here. The price includes shipping.
You could then sell your old modules to reclaim part of the cost.

 

I have 25 at 7.8, 2 at 7.4 and 1 at 6.5(code thrown).
Are the 7.8 and 7.4 close enough?
Thanks in advance.

 

They should be fine, for now.

Some additional questions (or ready what @dolj did):

• Were you just going to swap out the failed module?
• Were you planning on charging and balancing the whole pack?
• Were you going to do individual module balancing on the whole pack?
• How many miles and the condition of your Prius?

If you plan on going to Prolong equipment route, that would help the rebuilt pack last longer.

If not, you’ll be removing and replacing the pack many times from your Prius .

Keep us posted .

 

Got about 160,000 miles.
It's in decent shape.
After reading a lot on here, I'm going to try and get a hold of a grid charger/discharger to balance.
Should I replace the 7.4's (actually 7.49) also, since I have it apart? Or is that a close enough voltage to the 7.8's?

 

It is up to you, but I probably would if you don't fancy taking the pack apart again, otherwise, I'd do the charge and balance, then 3x discharge/charges with the final charge being another balancing charge. Let the pack settle then reevaluate the 5 modules (if you didn't preemptively replace) and make the decision then.

 

There’s a member in Maryland that reconditioned his Prius v last year: @GotRidofSignUpMessage.

You could check with him and see if he’s willing to share .

Or just buy it yourself.

Keep us posted .

 

Not 5...
1at 6.5.(obviously bad) 2 at 7.49.
The rest are showing 7.8.

 

Are the 2 that are showing low in block 1 and block 14 (or module #1 and #28)?

If so, I’d let them be and work on the one that is truly bad.

 

Is there as simple way to balance these while the pack is not in the car without buying expensive equipment?

 

It’s all about time and money.

If you have more time, you can charge and balance each individual cell. Would take about a month.

The Prolong equipment makes this a 3 day process .

But it can be done without expensive equipment .

 

The 7.49's are #1 and #28.
The 6.4 was #12.(through the code)

 

Sorry... 6.4 (bank 12) "Threw" the code.

 

Yes

 

Sounds like you’re working through it.

Good luck and keep us posted .

 

Yes, 7.49's are 1 and 28.
Is this normal? A concern?

 

I wouldn’t be.

I’d focus on the failed module and see where it takes you. @SFO and I are working on a failed pack currently and it exhibits similar behavior but module #9 in block #5 was bad.

Typically the packs get warmer in the center so they see more degradation and hence the failed module. If you try to “juggle the modules” to be in different places in the pack, know that the end modules may have deformed slightly, leading to alignment issues.

We’re just replacing the failed one in this pack and see where it takes us.

Good luck and keep us posted .

 

Voltage is really not the only indicator of battery health. I'm guessing you may have already read that but thought it was worth mentioning.

You would have to spend more money and/or time in order to do it properly. Is it worth it?

If you just swap in 1 module perhaps it will work. Ok. For a while. Then another module will fail, or the pack will become unbalanced.

You can deal with that when it happens. It may be a few days, a few week, or a few months. You don't really know. But at least the job will go faster the second (and third, and fourth..) time.

There isn't a real shortcut to doing it properly, but there are people who find diminishing returns and don't want to spend the time and money up front. So they end up with a randomly reliable car and paying as they go.

Feel free to call me to talk through the options or other questions you may have.