Gen II Prius Individual Battery Module Replacement

That is on my site:
http://www.hybrids.co.nz/nimh-batteries/third-party-battery-test-results/

 

Agree with you on "cold" conditions.
Wish though to discuss one major point - the use of the word "recovery" in many discussions.
I think it was incepted in people's minds by Dr "Q" two years ago with the intention to promote their "reconditioning" business, leading people into thinking that they could "grow" battery capacity.
The word "recovery" has double meaning (suggest look up Oxford Dictionary) and one could assume that multiple cycling could "grow" or "increase" capacity of the worn out NiMH battery. That assumption is incorrect.
Suggest using the word "recharge" to the battery's Full Charge Capacity.
Example: If you initially found out that the capacity of the module was, say 3Ah (that is Remaining Capcity) and after cycling you measured it to be 5Ah - then it simply could mean that FCC is 5 Ah.

Official Quality Testing Standards I am familiar with suggest leaving the battery for a month before you conduct capacity test (Self - discharge is factored in of course).

FCC is a term used by Texas Instruments in relation to batteries and different Battery Gauges they manufacture.
I have their testing tool and it is actually displaying FCC, RSOC, ASOC, and Remaining Capacity very accurately.
Suggest FCC and Remaining Capacity are very good terminology to be used with NiMH Prius Batteries.

 

Kiwi, I'm sure you have alot of knowledge to contribute, but again the way in which this information comes across takes away alot of the credibility that might otherwise be given.......something to keep in mind anyway.

 

Thank you, thank you, always happy to share and to make people's life easier and their business more efficient and productive.

 

Here is a simpler way to equalize in parallel. I just rearrange the pack in parallel and run a solid copper wire across each side and hold in place with the original bolts. I usually let them equalize for 24-36 hours.

 

Pretty simple, I like it........should work well on both the Prius and Camry (Highlander would be easier to just make a harness).

 

Kiwi,

Nomenclature just obfuscates a simple concept that determines effective AH capacity in our modules. Module capacity is determined by the weakest NiMh cell of the 6 cells in series (in a Prius, the Highlander modules have 8 in series). Balancing brings up the State-Of-Charge (SOC) of the weaker cells while the stronger cells dissipate excess charge as heat. When done carefully, this will maximize module capacity (to what is effectively the FCC of the weakest module) and together with the equalization process described above (gets all of the modules to the same voltage which is what the battery ECU monitors in module pairs as a surrogate for SOC) can result in a viable reconditioned HV battery. The capacity of your HV battery is then determined by the AH capacity of the weakest module in the pack.

As we have discussed over many HV battery threads, you also need to match module pair series resistances (do module load testing as described by MTL_hyhi earlier in his rebuilding efforts) as well as replacing any modules that exhibits an excessive self discharge rate (a charged module should still have a reasonable SOC after 2 or 3 months) if you want to put off the time when you will have to repeat the process.

JeffD

 

Thanks I got it to switch however it goes back to man all by itself. What should the amp settings be and how low should the voltage be on discharge? How can I read the results of each cycle?
Thanks.

 

So it's simpler to dismantle and rearrange and assemble a pack with the modules lined up. Then parallel balance it. Then dismantle again and rearrange the modules back the proper way?

 

I have to dismantle the pack to add the new module(s) anyway. It only takes about 5 minutes to dismantle once all the bottom bolts are out. I don't put them in until final reassembly.

 

Glad you paid attention to my post. I've got you reply as being in support of using FCC and not in favour of using the word "recovery" of capacity.
Small detail though - "stronger cell" will only dissipate excess charge as heat when and only it is overcharged and not with "parallel balancing".
Hence two ways of acheiving the same balancing result - either overcharge of do parallel balance.
In either case no extra capacity can be "grown" in the battery. That was the main point of my post to clarify "simple concept" to people who are not Electronic Engineers as you and I am and take Dr "Q" word as the only source of truth.

 

Thinking about streamlining the process and making it even faster (guys in Australia were asking an advice as they are doing 5 - 10 packs a week).
I was about to suggest the same consept of connections but to use flat bas bars instead. Thick round shape wires as on your pictures even in a wave form could possibly be pushed out from under the edge of the nuts , hence - little more prssure and the wire could be pushed out of position. Or perhaps you can flatten the round shape wire - but with the wave form - would it be slower to put on/off without completely uncsewing the nuts?
Why not using the copper bas bar connectors from old battery packs? They are flat and would be held in better.
How about making a tailored harness in a shape of a rake to put on/off quickly from the top without unscrewing the nuts completely?

 

How about it?

 

If you are doing a large volume of packs weekly and already have the modules removed from the case....just line up modules by polarity and overlap the copper bus bar plates from one post to the next to equalize. This only works if you have extra copper plates (which is typically the case with rebuilders).
Jessica

 

My bad someone already mentioned this process.

 

I think I have to buy a Prius that needs a HV battery, just to gets some hands on experience on this rebuilding stuff.......

 

I'm sorry, but you do not seem to understand what balancing a module does. You need to equalize the charge on each of the 6 cells within a module to maximize the usable AH capacity of a module. Putting modules in parallel only equalizes the voltage on the modules and does not help a weak module to regain any usable AH capacity.

JeffD

 

Hey Professor Jeff,

Do you think the device that's being sold to balance the entire pack at one time for $399 will do the trick in re-balancing a failed pack? I think another Jeff is selling it.

 

Yes it will help. I sell (and install them).

 

Can this re-balancing be done while it's connected to the car? Like hooking up jumper cables?