Augh!! P3000, P0A80, P3021, C1259 on an '07

What reconditioning process are you using biannually; HV pack charge to 100% (including topping off or soaking for hours), then down to a lower voltage, then repeat two more times ?

Is your need for biannual reconditioning based on a measured voltage difference (and or internal resistance) ?

Question(s) for all Prolong users:

Does anyone do initial reconditioning (or subsequent) based on a measured internal battery state (voltage/resistance) ?

If yes, what are those threshhold values?

 

I'm going by Prolong's recommendations and methods.

 

…me too! …me too!

 

Me too I started out like that but ended up following JC's advice and did not go anywhere as low as Prolong recommends because it would have taken another 10 hours at the rate it discharged with 25 watt bulbs. I got down to 75 volts and then had to quit and start a charge. But a week later battery still looks really good I have not seen a purple bar or less than 3 blue bars since. Which is just awesome.

But it's truly a 3+ day deal.

 

If you attempt to go down to 17v, you gotta make sure all your modules and it's cells are at 100% SOC when you start to discharge. The danger I see in going that low is if you have a few cells that are not at 100% SOC when you start your discharge, you'll discharge to a level where you can easily reverse charge and that will do more harm than any improvement you get from conditioning.

Discharging can be a huge benefit when done right and at the same time can be harmful if done wrong.

 

The Deluxe charger discharges to 134, 84 and 17v. It worked well for me in June going all the way down to 17 but you have me thinking about future processes. Going forward would you recommend all three discharges be at 134v with that unit or would I see any benefit in going to 134, 84, 84v?

 

Sorry took so long to answer. No you don't need to go below 134v. You are just conditioning your pack, not really trying to recover capacity on an aged old pack. Going down to 134v is all the conditioning it'll need.

 

Hmmmm! I'm not doubting what you're saying , but I'm curious as to what @jeff652 might have to say about it! (…heads to kitchen to make popcorn! )

 

There's still capacity you can recover from 17v - 134v. But there just isn't much.

Basically if you have a crappy module, no amount of discharges will make it better

 

I think what JC91006 is pointing out is confirmed by the Ni-MH technical bulletin put out on Duracell batteries.

Wayback Machine

"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."

Once the battery pack is properly conditioned all the way down to 17 the first time (as mine was), capacity is pretty much restored and the cells are as good as they're going to get. Conditioning every 6 months or so at 134v should keep all of the cells up pretty well without the risk of losing a cell due to the process. A weak cell that isn't completely on it's last legs probably won't deteriorate drastically in that short a period of time so why take the risk?

 

Voltage depression breakdown (aka capacity recovery) doesn't even begin until discharging a cell to at least 0.8V/cell. Any discharge that does not go at least that deep will not recover any lost capacity. I think that is basically what JC is saying here.

It's correct assuming the OP doesn't want to recover any lost capacity. Not sure if/why that would be his objective though.

Yes, I agree with this. You can limp the cell along for a while (a while can be as much as a couple years sometimes), but your not going to make it perform like a newer undegraded cell, that will not happen.

Polarity reversal should not be feared when done correctly. Correctly is LOW CURRENT and LOW DURATION. When Prolong products deep discharge, the load on the entire pack is only 200mA. There are white papers from Panasonic (I think is was) that clearly state that short duration low load cell reversal events do not damage the cells. I can experientially back this up by the hundreds of thousands of NiMh battery cells that have been cycled by our products and not only remained undamaged, but benefited in performance as a result of the reconditioning process. There have been some weak cells that did not survive the process, but those would likely have not lasted much longer in the car anyways.