Hello everyone! How do you "revive" 4200's that have been "sleeping" since last October? I put in a 15 minute charge back then and then left them to rest. Providing that they haven't gone to 0 volts since then; what is the the best way to discharge and then cycle them to "wake" them up for racing? Or am I stuck with 5 practice packs and have to buy new packs?............

The truth is that your stuck with 5 practice packs and have to buy new packs!!

You can try to put charge into any cell that reads below 1 volt, then do the normal charge/discharge cycle to see if you can bring them back...chance are if you haven't maintained them since last October, they have self-discharged and are hurt...
I have heard of people that have taken packs such as you described, once they are hurt, and charging them, discharging them to zero volts per cell, then deadshorting them with good results. If you think the packs are junk, what have you got to lose by trying the deadshorting?
Hope this helps-

i had a pack that had one cell that was actualy dead, so I tried to charge it as one cell at 1volt, actualy holding the leads to that one dead cell to "shock" it and never worked, but try charge,discharge, charge etc to get some juice flowing. or try the dead shorting.

I had a few packs which were dead for about a month. Couldn't even charge them because they just kept false peaking. I figured I would try to bring them back to life, so I charged them at 0.4A. After they peaked, I discharged them at 1A. Then I cycled them as normal.
I have included an image of the discharge graph for one of the packs. The cycle performed on 7/27/2007(i.e. 2007-07-27) was the one after the deep cycle. They are all 30A discharge rates. Notice that the 2007-07-27 cycle gained a pretty consistent 0.2-0.3A. Also notice the runtime was no worse than before.

Chuck

Does this work with 3800s? Or just the 4200WC cells?

Does this work with 3800s? Or just the 4200WC cells?
I only did 4200's, but my guess is that it should work on any NiMH type battery.

Chuck

So would there be a decent way to store some batteries if you are not going to race for awhile

So would there be a decent way to store some batteries if you are not going to race for awhile
That's a good question. I think most of the matchers will put almost a full charge into the batts before sending them out the door to a hobby shop. If you are going to store them for longer than a month, I don't know what you would do. I wonder if putting them in the freezer would help :)

Chuck

doesnt tekin make something for this?? the battery nurse i think its called... idk i havent heard much about it though

doesnt tekin make something for this?? the battery nurse i think its called... idk i havent heard much about it though
I've thought about the battery nurse.

The problem is that different cells in a pack self discharge at different rates. The battery nurse only monitors and works on whole packs. It seems it would be possible for one cell to get low enough that the battery nurse would try applying current to keep the pack at the target voltage and end up over-charging the cells that don't self-discharge fast. But I don't really know.

So would there be a decent way to store some batteries if you are not going to race for awhile


Short them.

tekin makes something for storing cells its called the battery nurse i think

wow that was weird for some reason my post didnt show up then when i reposted it was there :confused: sry bout that...

I've thought about the battery nurse.

The problem is that different cells in a pack self discharge at different rates. The battery nurse only monitors and works on whole packs. It seems it would be possible for one cell to get low enough that the battery nurse would try applying current to keep the pack at the target voltage and end up over-charging the cells that don't self-discharge fast. But I don't really know.

That's not exactly how the Nurse works. You need to search for the thread and read up on it. Basically it applies a voltage to the pack so it won't discharge, it really doesn't charge the pack.

That's not exactly how the Nurse works. You need to search for the thread and read up on it. Basically it applies a voltage to the pack so it won't discharge, it really doesn't charge the pack.
And if the pack's voltage falls because one or more of the cells is self-discharging rapidly, then what? Does it let the pack voltage fall or try to maintain the voltage setting? As far as I understood it tries to maintain the voltage. To do that with some cells self-discharging, it has to feed current into the pack to raise the voltage of all the cells.

I think feeding current into the pack is what we call charging, even if the the battery nurse is not marketed as a charger. If it didn't provide current when needed to maintain the whole pack voltage setting, there would be no use for it. You would just charge the pack as much as you thought was needed to hold it until the next race and leave it. And hope you were right.

I dodged a big "bullet"; brought my car over to Turn 4 last Monday for a little testing and did my regular procedure for discharging and charging my packs as usual;and they seemed to charge and peak at right about the same voltage as they did before. I did measure the indivual cell voltage and they seemed to over 1 volt per cell. I guess those JBR Cells were a bit "tougher" that I thought they would be. Whew! lol :thumbsup:

I agree with todd putnam and pat simkkins SHORT them on a novak tray or something

And if the pack's voltage falls because one or more of the cells is self-discharging rapidly, then what? Does it let the pack voltage fall or try to maintain the voltage setting? As far as I understood it tries to maintain the voltage. To do that with some cells self-discharging, it has to feed current into the pack to raise the voltage of all the cells.

I think feeding current into the pack is what we call charging, even if the the battery nurse is not marketed as a charger. If it didn't provide current when needed to maintain the whole pack voltage setting, there would be no use for it. You would just charge the pack as much as you thought was needed to hold it until the next race and leave it. And hope you were right.

Like I said check out the Tekin thread. That the guy who designed it explained how it works.

By definition it is a charger, but it does not apply enough current to actually charge the batteries. It applies a voltage intelligently as needed to maintain activity and charge. Self discharge is the killer of todays cells. That is no secret.

You are correct that applying a load or charge to a pack can cause imbalance. In fact a 30amp discharge to 5.4 is questionable and in actual use we really abuse them more than we know if you use more than 80% of the capacity.

The trick is the natural balance of the cells. A good cell needs very little tickle if any to hold the resting voltage. The laws of a voltage loop make the discharging cell or cells get the attention.

The reports we are getting from real racers is that their packs do not need to be cycled after being inactive. Some are also telling us the performance of their B packs has improved.... and she is really cute!

Tekin Prez

teamtekin,

I have a question about the battery nurse. I have three packs that will drop to 8.16 volts and the battery nurse led will stay on longer than the rest. Will the pack eventually come up with the help of the Battery Nurse or will I need to add a small charge to it with my charger?

I have been monitoring all of my mod packs with the BN and I have been adding a small charge to the packs that have dropped about every 2 days between races. I didn't know If the BN would do this automatically or what. It isn't clear in the abreviated manual. I would hope that the BN would do this on it's own without an external charger.

The battery nurse has a 7.8v and a 8.0v setting. At 8.16v the nurse should just be checking the pack and tickling it. If it drops to 8.0 or below the led will stay on until the pack is holding 8.0 without help. Many packs will cycle down into hold mode for a few hours and then rest above the hold for a few hours….. moderate excersize.

If a cell really wants to discharge quickly and is already dying, the BN may not keep up. If the cells are even marginal the BN will be able to maintain the setpoint without any additional charge being applied.

My personal testing (in my office with 30 packs and 5 nurses) shows that some gain a few hundred mah and some loose a few hundred after weeks or months of storage. All of them perform better than the non-nurse test subjects and the gap is getting bigger over time.

Tekin Prez