Reconditioning the HV battery using iMax B6

You should be able to use that to recondition one module at a time. But it might take you 3 months or more to get through them all.

One member here has 7 4-channel RC chargers so he can cycle all 28 at once. even with this setup, it would still take about 4-6 days to do a full recondition cycle (3x charge/discharge plus final full charge).

 

I don't use them, so no. But others here do. Any charger you have read about here on PC and you can get will probably be ok.

A good question. Look at it this way. If after 3 months it is holding a charge, it is good. If it is significantly low, you probably want to bin it or maybe do some work on it.

 

I recently purchased this charger, and have had no issues using it with Prizmatic modules.

If you're doing a single module at a time, it will need to be compressed so that the sides don't push-out during charge. If the module expands, it's no good to return to the pack. I ruined my first one this way.

 

Older modules need to be "exercised" to keep the factory original 6.5ah rating. Inexpensive chargers that can only discharge at 1 amp take too long, plus do not place much load on the modules at all. An automobile 12v headlight bulb with both filaments engaged will get the job done much faster. Fully charge the modules, then time how long it takes to reach 5.5v You will quickly and easily see which modules are weak, and need more cycles to bring the capacity up to the factory original.

 

You can't really return a low module to the factory 6.5 Ah by using up charge cycles. That would be having your cake and eating, too. You can recover some capacity by this process, but it is a game of diminishing returns – especially as the modules get older and older.

Yes, it takes longer, but you say this as if its a bad thing. Trying to recondition modules (or even a battery of modules) is not something for the impatient. High current loads (in or out) outside of the 40% to 80% SoC range should be avoided. For the full battery of 28 modules, I drop the current from 2 A to 1 A at 202 V (7.2 V/module) and then continue to reduce the current load until, at 168 V (6 V/module), I am at a 200 mA load from there right down to termination.

You don't really need to do it that way, it is quicker to check the voltage after a 120-sec interval with the load applied (not the bounce-back voltage after removing the load) on a fully charged module. This will tell you as much as the above method, but only take two minutes to do each one.

As above. You can't make a silk purse out of a sow's ear.

You can continue to spend your time this way as long as it is still interesting and/or fun for you. After that just replace them all with new modules.

 

dolj, Thank you for all the useful information. My thoughts on cycling come from my own experience, PLUS this info posted from another member. (pic)

What voltage do you terminate at with the 200ma load?


Thanks....

 

I used 4 iMax B6ac's to recondition my pack because of the red triangle. I took the bus bars off but kept the battery bolted during the process. I charged the modules spaced apart so the heat and expansion would not be locally focused. I clamped down one replacement module I bought with 2x6 and a few bolts. My parameters were to discharge at max amps to 6 volts, and then charge at 2 amps to 7200 mAH. Did it for 3 cycles plus one last charge. Kept notes on the discharge capacities as well as the voltage drops. To measure the voltage drops, when I started a new discharge/charge cycle, I noted the initial voltage and the voltage after 1 minute. After all the cycles were done, I measured the voltages to get the lowest one, and discharged all to a value a little lower than that. I then took apart the battery and connected all the modules in parallel overnight. I paired the best capacity batteries with the lowest capacities as well as the highest voltage drops with the lowest voltage drops. I used a spreadsheet to help with this pairing and it helped me get a set of 14 pairs that had average capacities and voltage drops that were quite similar. I also noted the initial positions of the modules and moved ones that used to be in the middle to the fringes of the pack. I also reconditioned the aux battery with a genius charger that I already had. It's been about a month. The car's battery is much improved now. Before, the battery indicator will drop overnight, but now stays at the same level as the previous day. It took me 2-3 weeks of day and night charging with 4 chargers. Good luck.

 

It depends on which cycle I'm running. In general, I'm following the updated Hybrid Automotive guidelines.

1st discharge: 134 V (4.8 V/module)
2nd discharge: 101 V (3.6 V/module)
3rd discharge: 84 V (3.0 V/module)

If I feel the HV (hybrid vehicle) battery is in good condition, I might do:

1st discharge: 134 V (4.8 V/module)
2nd discharge: 84 V (3.0 V/module)
3rd discharge: 67 V (2.4 V/module)

You need to balance multiple cycles with the knowledge that each module has a finite number of cycles before it is junk. With this in mind, I tend to lean towards "less is more". It is nevertheless a very intricate balancing act between increased capacity and reduced longevity. The older the module the harder it gets.

 

I have 3 imax 6bAC as well but experiencing strange behavior - reaching high voltage.
I'll appreciate if you can share from your experience:
here is the thread: Charging cell using rc charger, voltage jumps, is it normal? | PriusChat

 

ANYONE considering trying to "rejuvinate, recover or restore" worn out battery cells needs to read the above post.......and let it sink in.
IF they are really worn out, you can NOT "restore" them. Just not possible.

 

Dolj and sam spade 2 are completely correct. You can NOT " recover or restore" worn out battery cells.

The million dollar question is: What criteria does one use to determine that a pack is "worn out"? Is it age, miles, or perhaps climate that the pack spent its life?

(1) Let's look at age first. Modules from October 2003 are VERY old. TMR-JWAP posted on this pack. Here is the link:
Dorman HV Battery with a new lease on life..... | PriusChat


Modules went from crap, to "like new". Yes it was a LOT of work, all those cycles.


(2) Miles: I'm not sure on this one. Packs like to be used regularly. Sitting for an old pack is usually the death sentence. My 2005 with 60k miles, original pack, can deliver 150 amps accelerating from a dead stop. I've spent a lot of time on this pack. Half of the modules have been re-hydrated. Module #20 sags under load. Cycling and re-hydrating have been ineffective on this module.


(3) Climate: This I can answer with certainty. Heat kills. End of story....

 

Hi sjguy,
Thanks for sharing as I am in the process to re-condition my 05 Prius using the same iMax you have. What is the average module capacity that you got after the re-conditioning? What exactly is the "one last charge"? "Re-Peak" for one time after the 3rd cycle recharge? Thanks again for helping....

 

Hi judot, the average capacity at the end was ~4500. At the beginning, the average was ~2800. Also at the end, the lowest individual pack was ~3300 and the highest was ~6000. I must have done charge/discharge cycles instead of the other way around, so at the end, I needed the last charge. It's been awhile and I have forgotten the exact details. Good luck.

 

Hello,
Can you please tell me if it is possible to charge/discharge all 28 modules is the same time, if I hook them in parallel, using only one Imax B6 80W? The time is not an issue. It will be more comfortable for me doing that instead of charging each of them at a time. Please tell me the pros and the cons for this procedure.
Thank you

 

No, you couldn't wire the modules in parallel and use one charger.

Most often these charges have a limit on the number of cells (and therefore modules) you can charge at one time. You need to look in the user manual for this information. So, if, for example, it said that 15 was the maximum cells then you could charge up to 2 modules (@ 6 cells per module) at a time. You would wire these two modules in series, not parallel.

 

Thank you dolj for your quick response.
I have encountered a problem when I tried to discharge/charge a single module using my imax: I set the cutoff capacity to 7200, discharge and charge current to 1A and lowest volatge to 6v, nimh sensitivity to default. After 1 single cycle the process ended and showed CAPA blinking and 7200mAh capacity reached, even I set it up to 3 cycles. Don't know why