Top-balancing an '09 battery pack

My '09 parts-prius had been sitting for a couple months since I robbed it of its transaxle so figured I should at least do
a top balance on the battery before too much time goes by.

After about 6 hours the battery is showing 238.5 volts for the last hour or so, so I guess it could still have several hours to go; I'm using a constant current of about 350mA and some of the battery modules are now getting up to around 30 C or so, and I'm wondering if I can keep them all cool enough by aiming fans at it or do I really need to grab the venting pieces and cooling fan out of the parts car and connect em all together to give it more proper cooling (it's all sitting on top of the washing machine at the moment). So far I have a tower fan laying on its side aimed at the bottom vent-path. I've got a couple more fans I could point at it, if needed.

I would appreciate any guidance or observations from anyone who works with the batterys regularly and might care to contribute.

 

Will do, thanks.

Yeah, kinda glad I thought to do it before it gets hot around here...

Thanks Ray, will do.

 

Finally finished with the top-balancing. It took about 20 hours to get up to 241 volts, at which point the voltage slowly started dropping off.

The first day I only charged for 2.75 hrs., starting voltage 212, ending 236.9
the next day charged 7am to midnite, starting voltage 228.9 , " 240.7

Today charging 7am to 10am it got up to 241, then started slowly dropping: since my understanding is that the balancing is now being done at this point, I let it run for 6 more hours. I doubt anything's ever been done to this pack except to use it for about 186k miles and nine years or so. The voltage then slowly got down to about 238.2 and had made its way back up to 239.7 by the time I turned it off.

Much thanks to all the PriusChat folks' support and helpful postings, both current and in the archives; just another reason to love these cars...

 

I was just gonna add a picture to my last, but saw your post so I'll attach it here. This idea of good practices in battery maintenance is not new to me, but actually being able to do it and benefit from the result is.

I envision Prius farms in the future, where the good Prii with bad brake accumulators go to live out their remaining days in repose with their new solar panel neighbors.

LATER EDIT: forgot to mention, no harness installed, but I'm thinking of running a patch cord from the non-energized side of the Pwr relays, so I can put a charge on it or hook it to an inverter in the future.

 

I should have known,,,anyway, the pack from '06 is behaving a little differently than the '09 one did, so just thought I'd mention it; it spent a long time yesterday meandering around 238 volts, varying by a tenth of a volt at a time on a 5 tenths spread, never made it to 239 before I shuit it down for the night. Then today it took a couple hours to make it back up to 238 and started the same variation, from about 238.5 to 237.8 again 5 hours into it - guess it may take longer to top balance this one, and possibly more frequent monitoring of the voltage.

 

Top balancing an '06 Battery pack:

I went ahead and let the charger run on for about 40 hrs. total from that point, The peak V for this pack was 238.5, which it seemed to reach 3 or 4 times through the day, after which the volts would drop slowly for a while, etc., etc.

Now that I have the newer pack in the daily driver, I'm thinking of dismantling the '06 pack for an electric bike project or something...

 

Just adding on any observations on either battery from now on, I guess...
anyway, seems like IR has gone down, now (June 1st) reads 20 milliohms for all 14 blocks, using TIS with a vcx-nano.
This pack has 186k miles (approx), born '09.

 

Damn, got a P0A80 on the '09 pack this morning. Batt bars were at 7 green and suddenly changed to 2 purple as I was coming up a hill to a traffic signal, there was an odd smell so I stopped to have a look in engine compartment. Surprisingly, the top of the inverter felt very cool, the air cleaner was warm, air temp was about 65. Drove the rest of the way home (mile or so) and checked for codes. Battery came back up to 5 blue bars by the time I got home (mostly uphill all the way).

Did a 'health-check' in TIS, got P0A80 dtc; checked data, all IR for every block was 24-25 mohms for the freeze-frame data from the code, also showed about .3 V difference between min. and max. V . Cleared all codes (the P0A80 was all that was showing), exited and went back into TIS, all is well, IR on all blocks is 19 mohms, .13 V diff. min to max.

 

top balance '06 pack, then discharged to 134.4.

1st top balance got up to 236.7, then meandered around 235.something, down to 234 and back up over the last few
hours of a 24 hr charge period; started discharge at 235.0 V, took about 8 hrs. using hi-pwr resistors and discharge currents of .5 or .6 A.

removed 'puter in battery and found turquoise corrosion just showing on the tips of six of the pins, tried cleaning with ISO/q-tip, no dice. applied dielectric grease in orange plug to hopefully improve connection. No erosion of pins or ckt. bd. apparent (yet).

Top balancing again - ran back up to 233.8 or 9 after about 16 hours and stayed there for about 4 more hours so called it done, will swap back into car tomorrow and see how it does.

 

'06 battery working fine.. '09 Batt also had turq. corrosion, but 7 in a row rather than 2 rows of 3 ea; Cleaned connectors w/ISO and stiff bristle brush, nothing worse going on in the 'puter box. Coated connectors w/DG and unplugged/replugged about a dozen times, most of corrosion came off..

Discharged '09 to 134.3, then top balanced to 239.2.

 

Thanks, figured it may be helpful to others feeling their way through some maintenance tasks

I like my Prii - I even bought one of 'em a new 12 volt the other day 8^)

 

Been over a year since posting about the batteries; over the winter my parts car developed probs after serving as a generator for a couple days during a power outage, it developed so many unfamiliar (to me) codes that I just don't know where to start on that, so I didn't (aside from getting a new radiator and deleting the CHRS BS).

Then, while looking into things again the other day, the '09 pack suddenly started to show a fast loss of charge on the 'energy screen', going quickly from 5 blue bars to 2 purple in about 10 seconds (I shut it off there), I decided it was time to try balancing the battery again and have a look to see if any of the turquoise corrosion had returned. It had. I also found while disassembling things that I'd neglected to tighten the grounding terminal that the ECU grounds to last time I was in there (big oops for me - It would be so great if that was the only actual problem).

So, now my hope is that cleaning the corrosion up and applying some dielectric grease will, along with a 'top balance - discharge to 134.4 - top balance' regimen will put things back into a useful state.

This time I thought to check the voltage on every cell to begin with - turned out that the first and the last cell (both end cells) read significantly lower, one reads 7.32, the other reads 7.42, all the rest are 7.5 and a few tenths - never checked this before, wish I had. I also tried to check for any mV dropage between cells while charging, didn't see any...Anyway, after charging over night all cells are within a few mVs of each other. The turq. fuzz was back, but only on 2 pins this time so will have to see (and hope) if cleaning that and some dielectric grease will take care of the problem.

 

Finished the charge-discharge-charge cycle and all modules are now within a few mVs of each other. The final charge ran about 16 hours, climbing to 239.7 max.; when next checked it was 237.5 so shut off at that point.

Next, I've got to take out the inverter, replace the inverter pump with new, and make sure my deletion of the CHRS crap and refill of the ICE coolant loop is all up to snuff before I can try out the battery pack.

 

Top balancing new-to-me 2008 battery, (bought for 200 in hopes of getting a working battery computer) hooked up and did usual routine for 24 hrs., then turned cooling fan off, but forgot to disconnect the charger (a 350mA constant current driver )...duh...left it hooked up for another 2 days. Happened to notice the warmth coming off it as I stood near it, then went and got the temp gun. Every module was between 120 - 125 degrees.

The next morning it read 237Vdc and all cells were still within .2 volts of each other so I installed it in place of my '06 battery, that was about a month ago and it has been doing fine, so I now have an '06, an '08 and an '09 original assembly battery, gonna have to figure alternatve uses or something.