My First Battery Reconditioning Attempt

Greetings Earthlings:

First Prius (Bought for my 17 year old) - 2008 Gen 2, 211k Miles, Battery was replaced from a reputable company in Scottsburg Indiana ($775 refurb replacement) about 2 years ago from a previous owner. Warranty has expired on battery and I am getting 32mpg and red triangles, P0A80 and P3000 codes, car still runs but have to reset light often.

Had the pleasure of spending a week reading hundreds of pages on battery reconditioning from this site and other YouTube videos online. I am making an attempt to recondition my battery on the cheap since I just put about 500$ in the car (O2 sensors, cats, etc.) and well... its for a teenager, probably won't last forever with him behind the wheel.

I bought a 4 port RC charger from a local hobby store. I have started to recondition my batteries and I would like to document the process for others as well as obtain some guidance and feedback along the way since this is such a lengthy process. If anyone has suggestions along the way it give the gift of time and an opportunity to learn how to do this properly as well as giving back to anyone else down the road.

I am going to completely skip all of the information that led up to the battery being on my bench and my charger hookup up to it and really focus on the battery modules as I work through them one by one doing the discharge and charge cycles. I realize there are multiple parts to the equalization to get these batteries reconditioned and restacked in the back which I hope to eventually explore during this thread.

I have currently ran 16 cycles so far on 7 different batteries and the results to me are interesting because I like to geek out on stuff like this. By the way, I am not looking for perfection, I am looking for a car that runs decent without warning lights for at least 6-8 months.

So initially I started with these charger settings:

Charger: Dynamite Prophet Sports Quad Charger 4x100w $229 from local hobby store

Discharge Rate 5.0a down to 6.3v (Quickly changed to 6.0v on future runs)
Charge Rate 2.0a up to 7200 mAH cutoff (Should I go higher?)
Rest Period 5 minutes
Delta Peak 8mV sensitivity
Cycle: Discharge First - Charge Second - Repeat

I noticed at these settings, I was getting very little mAH improvement, like less than 200 so I changed quickly to bring them down to 6.0v and I started seeing much more improvements in the increased capacity on most modules.

Here is my chart so far:


So far most of my batteries are in the low 4, high 3 range to begin with, age worn batteries I assume. From what I am reading, 4000 mAH should be the minimum to consider putting back in the car but I realize I also need to account for load testing and resistance values once I have them to make that decision.

Questions

1. Why do some batteries not charge all the way up to 7200 and one did? Is it because of their memory/capacity? I see where the ones that don't reach 7200 do increase with each charge. Can someone explain that to me?

2. My Delta Peak is currently set at 8mV, is that good or should I raise it?

3. Should I cycle all modules until I get to at least 4500 or more before (or they start to go backwards/down in capacity) ?

4. Any suggestions on changing any of these settings as I continue down the pack?

Please be gentle on me and I thank you in advance for taking the time to respond.

Chris in Kentucky

 

I had not seen that post but thanks for sharing, very awesome information to read!

 

More updates



Battery 9 might be a challenge

Decided to start doing cycles down to 5.8v after a few successful 6.0v cycles.

 

I decided to track the battery history by serial number. So my 2008 has mostly 2005 batteries, 1 2007 and one Gen 3 2013 battery mixed in. Probably not a good idea to mix that Gen 3.

 

R-P:

I am using 10 gauge wires and alligator clips all soldering for my connections - I feel like they are sufficient. I started with ring terminals and using nuts to hold them on but its a pain removing and moving them back and forth. I am making sure all charging occurs with the unit is fully loaded and clamped to prevent swelling. I am going to play with the different Delta V settings to see if it makes any difference but most of the module are making their way up to 7200 or close after a few cycles so it may not matter in the long run other than my time. My plan is to do discharge down to 5.7 going forward after the first full cycle using 6.0 as my discharge.

SFO:

Check out my latest results. I ran another cycle on battery 5 highlighted in yellow and this time I took it to 5.8 discharge and I lost capacity, even all the way back to first discharge. Do you think this is an anomaly or am I damaging this module? I guess at 3870 it isn't worth of going back in the car so I should continue to cycle it? Maybe I should try to cycle it with a slower charge value like 1.0 instead of 2.0?

I ordered another quad charger off Amazon that should arrive today... This is taking waaaay too long.

 

Update:

Check out the Gen 3 battery 21

 

The modules were reading slight above 8 volts after charging but if I let them sit for a few days, they will settle back down to about 7.8~ . I ended up buying a battery tester from Harbor Freight (100 amp) and tested each module for 30 seconds and recorded the voltage drops. You can see that in the chart below. I ended up pairing the modules so that they were balanced (Best with worst) as far as resistance goes. So Battery 28 got paired with Battery 29 (See the chart)



I ended up with two 8 port chargers to make this go faster. I bought the second one off Amazon, used it for two weeks, sent it back



I discharged each battery down to 7.3 volts using the RC chargers

I pulled all the modules out, stripped stereo speaker wire down to the wire only and wired them with all the positives, then all of the negatives and let it sit for 24 hours.



I went from 28 - 32 mpg to 45-47. However, I should note that it took two full tanks of gas before the MPG's were restored. It was like the car had to gather enough data to figure out how to deliver the gas to the car.