Post-Prolong Charger Bad MPG

i don't know if they make gen 2 size. if not, there are some continentals rated highly here, and michelin premiers are pretty good as well.

 

I gained about 1, 1 1/2 mpg after the longer charge. I already had a new 12v that was installed shortly before I purchased the Prolong system for the HV.

One of our more respected members (sorry I'm having a senior moment on his name) suggests only the first two cycles. Not knowing how imbalanced or weak each cell is in relation to the others right now his concern is accidentally draining the weakest cell and killing it.You might consider doing the first two this time and then do all three the next time around after some better balance and strength is restored.

No babysitting is necessary. I just chose to do it to watch the numbers. The Deluxe Prolong system really is a "set it and forget it" system.

There are better MPG tires than what you have but given your conditions I can't make an educated suggestion. Others here can. I'm using the Pirelli Cinturato P7 A/S and been very happy with them (30k miles so far and in great shape) but my car barely sees rain, let alone snow or ice.

Note that I'm no expert or even very mechanical. I'm just relating my experiences and actions based on the good people here at Priuschat who have been generous enough to give me guidance.

 

OK, Welcome to PriusChat, and here's the log from my latest full recondition of the TractionBattery in my 2009 Gen II Prius (130,000miles on the clock) hope this helps - the advice you will find on PriusChat is worth its weight in gold (for the most part) Just remember, search is your friend, and as they always say YMMV!

Log:
Date 20171226: Prius Hybrid Traction Battery long recondition 128,500 miles
Chrg1: 31 hours 248V 356mA
Dschrg to 134 V - 6:45 hours
Chrg2: 32 hours 247V 356mA
Dschrg to 84 V - 6:45 hours ("dead-cat-bounce" had taken the V back up to 190V when I checked!)
Chrg3: 33½ hours 249V 356mA
Dschrg to 17V ~ 7 hours (I started checking around 6:45, and the meter was at 60V, and dropped at 10V every 6 mins or so, and I was able to hit the 17V on the nail)
Chrg4: 40½ hours 250V 354mA (…yippee!) now leave for 2 hrs to recover!
Total elapsed time - 159½ hours (6½ days)

 

I was going with the Prolong 24 hours when I first conditioned last June. I just made an arbitrary decision to go at least 40 hours in December since the website put the long limit at 48 hours and I figured it wouldn't hurt to "go long". I'll probably go at least 40 again on the last charge this June but I may limit the first couple of charges to 30 or 36.

36 hours for your last charge may or may not be enough.Every battery pack is at a different level than the next. As you can see, WilDavis' numbers show that 36 was a little short on his final charge. Even if it's not quite long enough it should be reasonably close. Maybe when you are able to budget additional time for it you can go 40-48 hours in three months when all you're doing is the intermediate charge balance without discharge.

As for overthinking it, I think we all did and some people like me still do. Being comfortable with it comes with familiarity and this is still relatively new to many of us.

 

40 hours is good advice! I'll be doing a "shortie" at the end of next month, so I'll try and arrange it over a long weekend.

I looked through my previous logs, and noticed that several of the previous soakers might have been improved as 40 hourers (…isn't it amazing how 20/20 hindsight always seems to work better! ) Having logged the most recent complete recondition, I now have a much better idea of the timing, and would highly recommend any newbie to the art/science of Prolong Grid-Charging to try to take notes and log V/mA/T so that you might do the same!

 

I have my 3-month intermediate charge in a couple of weeks and it will be a 40-45 hour one.

I have noticed that while climbing the Cajon Pass I was going into the purple at 2 1/2 months after the first conditioning that had the charges in the 19-31 hour range. This time, 2 1/2 months after the 26-40 hour charges the car still stays in the blue up the same pass. It could be due to cooler weather, though, so I may not be comparing apples to apples..

I'll go 36 up to 45 hours on the charges in June and see what happens. We're driving cross country again this year following the conditioning in June. I'll be able to make a more accurate assessment since we're taking the same route from here to Salt Lake to Denver as well as the same route home from North Carolina. We'll even be hitting the same gas stations so different fuel won't be a factor (thank you, Pilot/ Flying J trip planner!). Only the middle of the trip will change.

I look forward to reporting the results.

 

Just to follow up on the gas mileage, Trab, I reviewed my month over month records. I wouldn't say it has improved mileage all that much even with the longer charges improving battery performance. February looks impressive but the car was on the freeway more.

Dec. 2016 42.60 mpg Dec. 2017 42.22
Jan. 2017 40.82 Jan. 2018 41.00
Feb. 2017 38.94 Feb. 2018 41.81
Mar. 2017 42.37 Mar. 2018 ???

This month will be a a good test. Possibly the endurance factor resulting from the longer charges does account for some of February's improvement but I won't be convinced unless the numbers improve again. I think a lot more of the value of the Prolong system is preventing a battery from continuing to deteriorate at whatever rate it is. It is very much a maintenance tool but not an mpg solver.

 

The reason you saw 244 then later saw 240 is because the battery has hit full charge then began overcharging, with insufficient cooling this could be damaging to the battery, particularly weaker modules. Under a constant charge NIHM batteries peak in voltage, when the pack voltage begins coming down as the charge continues the battery heats up and continues to do so until you turn off the charger.

NIHM is very sensitive to overcharging and running the charger for 40 hours will do more harm than good. Total capacity of the Prius module is 6500mah, charger output is 0.35mah, full charge is achieved in less than 20 hours from empty. An additional 20 hours will degrade the battery pack by a measurable amount, reducing total capacity by 10 to 15%.

Without monitoring each individual module voltage I would also suggest not taking the discharge below 168 volts per pack (1v per cell), a previous functioning but weak cell can be ruined by over discharging.

 

So, are you saying the Prolong Discharger is not recommended and might even damage your battery? First Discharge value for my Prius is 134V.

 

@jeff652 can chime in but I am sure the Prolong Intelligent Discharger adjusts accordingly
The older Prolong light bulb discharger depends on you for the intelligence.

 

With insufficient cooling it would be a problem but the Prolong system runs the cooling fan at full speed. That bleeds off the excess heat from the cells that are already full while the lesser charged, imbalanced "weaker" cells catch up by continuing to charge. The number fluctuations are part of the balancing process.

The warning about over discharging is warranted. It is covered on Page 8 of Duracell's Ni-MH Technical Bulletin

Wayback Machine

5.6 Polarity Reversal During Overdischarge
When cells are connected in series, the cell with the lowest capacity will reach a lower point of discharge than the others. The more cells that are connected in series, the greater the possibility of a cell being fully discharged and driven into overdischarge and polarity reversal.

Page 10 of that same bulletin documents the value (need?) of performing charge/discharge cycles on Ni-MH batteries when used in packs.

I'd like to see the documentation regarding the claim of a 10-15% capacity decrease if using the Prolong system for a 40 hour charge and balancing cycle. I'd be amazed if such documentation exists. I can see damaging cells without cooling or leaving a full pack on a charger but as long as some cells are still accepting a charge and the other cells are cooled it shouldn't be a problem.

 

Polarity reversal concerns are why is is recommended to charge first, before the discharging when first balancing a battery pack.

 

In addition, as the battery becomes more in balance with regular reconditioning, I'd imagine that the duration of the top balance can decrease. The important thing is to monitor the voltage and take note of when the voltage starts to drop.

 

Just to follow up, I have the number for March. After filling up this morning the monthly mpg works out to 41.95. I'll stick with my original thought. The Prolong system is a good maintenance tool but not a solution for poor mpg.

 

There is no one solution for poor mpg.
That is a symptom that may be caused by many different things or a combination of things. A failing HV battery is only one thin that can cause poor mpg.