Gen II Prius Individual Battery Module Replacement

As long as your methods are consistent then you're doing fine. Dp numbers are something I haven't nailed down yet to be honest. Sometimes they trigger, most times they don't. The faster I charge the more often they hit. Default seems to be the best. If your numbers are all in that range then you're doing great and I wouldn't change anything. Remember, if you suddenly change your method your reported discharge capacity will change (perhaps drastically) but it doesn't mean the module suddenly went bad. You're doing great and I wouldn't change anything at this point.

 

Thanks, I really appreciate the help.

 

If you are charging to greater than 100% design capacity (7500 mAh for example) on an older, higher mileage Prius pack, and you are getting 5500-5600 mAh on discharge, then you might want to consider only charging to 6500 mAh (100%). This will prevent heat buildup when you are overcharging (above 100% design capacity) and it might make it less stressful on the battery to yield your desired capacity. However, sometimes this requires 5 to 6 cycles with long cooling breaks after every 3 cycles, so if you are rushed for time, the trade-off may not be a benefit to you.

I also get the slight drop from the second cycle to the third cycle when either the module is degraded and therefore mismatched if the capacity doesn't come close to the capacity of other modules, or when the pack as a whole is just getting way too hot during the cycling process. Experiment with it and help the heat dissipate over a larger area and you will find an efficient restoration process.

 

Don't forget that charging nimh isn't 100% efficient, so you have to overshoot the 6500mah limit. I don't know the exact amount though, I've seen some wide ranging numbers from different sources.
Edit: I understand what you're saying though..

 

The current pack I have was from an 06 with 114k miles, or so I was told, and when I had the limit at 7500 I noticed a slight drop from second to the third cycle but when I lowered it to 7350 I had an increase. I have monitored the heat rise and have seen very little, 2 to 4 degrees using an infrared thermometer.

 

I got a second Thunder T6 to speed up the process. I have a second battery pack, this one is from a 07 with 86K miles and no known problems. I did the first 8 modules with the charge limit at 7250 mah and 3 cycles. I tried the second 8 modules with 4 cycles and I still had an increase of 10 to 60 mah on the discharge. I lowered the charge to 7050 may on the next 8 modules and had similar results. On the last 4 modules I lowered the charge to 6950 may and it fell off slightly so my conclusion is that the optimum is 7250 mah on the charge. On the 4 lowest discharge mah (approximately 5200-5400) I cycled two more times and got an increase of 40-90 on 3 and same on 1.

Question:
Does it hurt to cycle 4 to 6 times if the discharge mah keeps increasing?
What should the maximum voltage differential be before I hook the modules in parallel?

Thanks for any assistance.

 

There are diminishing benefits after 3 charging cycles so It is not worth further cycling. Batteries have some wear out mechanisms which can limit the number of full cycle cycles each cell can take without significant capacity loss.

JeffD

 

I bought a 12V, 55W halogen light bulb from Sylvania for a load test of the battery pack, however, I don't know which terminal was positive or negative in the bottom of the light bulb. The bulb did not mark anything to distinguish one metal terminal form the other. How do I know which one is positive (or negative)?

Thanks.

 

It doesn't matter, it's dc, just pick one as the positive and run with it.

 

Thanks, LucasElectric. The other article that I read said that if I mix the polarity, I might damage the lamp (That's why I asked). But I believe you and will not worry about the polarity then. Thanks a lot.

 

As mentioned above it doesn't matter which side you use as the positive or negative (negative side is common circuit on the headlight), but you really should be using both a high and low beam together (ie 55w + 65w = 120w) to give you a more definitive result as to which modules might be bad.

 

MTL_hihy,

Thanks for your added information. However, I did not get the part "high and low beam together (ie 55w + 65W = 120W)" you said. I bought a 55W halogen lamp so that I could use it when I need to discharge the new battery module to match with remaining battery modules. Can a single halogen bulb be lighted in two different mode (I mean, high and low)? I am just a newbie in car electric and might ask a dumb question.

Thanks.

 

Any dual beam (High-Low) headlamp has two filaments and three terminals. You connect one battery lead to the common terminal and the other (usually the positive lead) two both of the other terminals. This maximizes the current flow that the headlamp pulls from the battery module. You can determine the common terminal using a multimeter in the resistance setting. The highest reading will be across the two terminals connected to each of the filaments and the common terminal is then the other one.

JeffD

 

JeffD,

Thank you very much for your information. I learn a new thing every day. The 55w light bulb I bought has only two terminals so I guess it has only one mode (probably low beam, I guess). Now I fully understand why certain light bulbs I saw have three terminals.

 

Dear all,
I am now the proud owner of a bad HV battery pack... The problem announced itself with some error codes,

P0A80 - replace HV battery pack
P3015 - Module 5 weak

Following the excellent advice above, I have partially disassembled the pack & have the following module voltages, (from the ECU end)

1 8.20
2 8.13
3 8.11
4 8.10
5 8.10
6 8.08
7 8.08
8 8.07
9 8.08
10 8.07
11 8.08
12 8.07
13 8.07
14 8.06
15 8.06
16 8.06
17 8.06
18 8.07
19 8.07
20 6.86
21 8.08
22 8.07
23 8.08
24 8.09
25 8.09
26 8.10
27 8.12
28 8.19

This is from a 262,600 mile Prius, which has sadly been (mostly) stood for 8 months during a very slow engine repair project. When it was run on test,t he battery was allowed to charge up to hopefully preserve it. Alas it looks like module 20 didn't make it.

I have a replacement module on order, a question for the Brits on here,

Any recommended battery charger to balance the pack? The Dynam Supermate DC 6 does not appear to be available in the UK, and the Hitec H4 best price appears to be around £180. Any recommendations for anything which is available within the UK?

Thanks all.

Matt

 

Hello everyone, I need your opinions and expertise here. I have been running the cycles on my HV and below is the discharge capacity of each module after the third cycle (order is not indicative of original position of these modules). How do you think I should rearrange these modules in the pack for optimal longevity? Would moving the best cells to middle of the pack be the best strategy ? Or is combining #1 and #28, #2 and #27, #3 and #26 etc. and shoot for the average (around 5400s mAh) be better as some say this is due to the fact that the battery computer reads by block (pair), if this is the case where would you rearrange these cells after grouping them by pair/block? Would the block composed of #1 and #18 goes to the middle of the pack, etc.?
Also unrelated issue I have been wondering is how important is connecting all modules in parallel in order to level the voltage? Would it be just as effective to discharge or charge them to a specific voltage, say 7.6v? Thanks a bunch for your time.
1 5941
2 5876
3 5852
4 5850
5 5818
6 5625
7 5591
8 5580
9 5512
10 5502
11 5468
12 5459
13 5458
14 5447
15 5440
16 5423
17 5422
18 5419
19 5398
20 5393
21 5373
22 5319
23 5298
24 5285
25 5282
26 5257
27 5210
28 5155

 

As for how to arrange them, I would say go the 1/28, 2/27, 3/26 etc but, I am not an expert. Logically that makes the most sense to me. I think if I were in your shoes, I would go that route.

As for balancing, there is no substitute for hooking them up in parallel. Doing this perfectly balances the voltage whereas discharging to a certain voltage only gets it close.

 

If this is the case, just curious how would you place these blocks in the pack? 1/28 to the middle? or 13/14 to the middle? Do I make sense?

 

I would do 1/28 in the middle but, I do add the disclaimer that I'm n0 expert. Ericbecky or Bobwilson are probably better people to ask.

 

Would you have any concern that 28 will be subjected to more heat even thought it is the weakest of all?