robteam70

Ok i have done quite a bit of searching on the net and can't seem to find much info on this matter. Is it even necessary? I plan on typically charging my batts at 1C when they get here but was wondering if I should take the time to slow charge at C/10 for the first charge or if it doesen't really matter. Thanks in advance.

JoeAirPort

My Feedback: (41)

It's very important to do this right. Slow charge the pack at C/10 for 14-16 hours. Discharge it and do it again (this is the forming charge). It should be all set after that. I tell everyone that they should slow charge as much as possible. It makes for a very even charge, making all the cells full (vs having one cell low). It also doesn't cook the battery like a fast charge, decreasing the life span of the pack.

Geistware

My Feedback: (16)

You can charge your packs at 1C AFTER the initial charge.
The initial charge needs to be at C/10 or less.

robteam70

Ok thanks a lot guys. Now I have a couple more questions. When I discharge the battery from the initial charge can I just run it in my car or boat to discharge it or should it be discharged at a particular rate? The charger I ordered is a Duratrax piranaha digital peak charger and it doesen't say anything about being able to discharge a battery, so I might not be able to set my discharge parameters.

One more thing, if the charger is set to C/10 once the batteries are broken in, it should only take about 10 hours to get a full charge right? The 14-16 hours will just give it a decent trickle to bring each cell up to full capacity for the first charge if I'm understanding this right? And should I set my peak threshhold to the max to try and avoid a peak before 14 hours?

This will be my first experience with peak chargers as I've only used timer chargers in the past. I never realized how much we abused our battery packs back in the day (taking them straight from our frogs after a race and onto a 15 min charger). Now that I've somewhat educated myself on batteries and charging techniques I'm going to try and take better care of these new batteries.

DHG

My Feedback: (7)

Rob,

Speaking as a "high-end user", not a professional battery expert, I don't think you need to worry too much about controlling the discharge of a nicad pack as long as you don't dump it real hard. Normal flying or whatever should be fine. It's probably good to take it all the way down to 1.1 volts per cell if you can, but I wouldn't go below that -- not on the first cycle, not ever.

The C/10 charge rate is a 16-hour charge rate. The math doesn't work because the last part of the charge is partly dissipated in the form of heat. C/10 won't overheat the cells to the point of damaging them, but it will ensure that they get completely full.

I'm not sure what you mean by "peak threshold", and I don't want to give you any bad advice, so I'll bow out here. But FWIW, my slow charger is basically a glorified clock. It delivers C/10 for 16 hours then drops down to trickle at C/100. After a couple of cycles on that, I use an Ace Smart Charger (peak detecting fast field charger).

Duane Gall
RCPRO

guver

My Feedback: (325)

Your piranha digital may not be able to give a constant slow charge. It is a peak (fast) charger.

It may be able to be fooled and use the trickle option, but it happens after a normal peak charge.

JoeAirPort

My Feedback: (41)

I'm not sure the discharge rate really matters, but the slow charging it the first two times is what's important.

The slow charge time should always be more than 10 hours since the charging cycle is not 100% efficient. The battery takes more than 10 hours to get fully charged.

If this is for a car I guess I'd just slow charge it twice and then fast charge it after that. Every 5 fast charges give it a slow charge. That will keep the run times longer. For a receiver battery/servo on a plane I prefer to slow charge all the time for best reliability (while it's in the air).

robteam70

I really appreciate all the info guys.

Duane - I'm actually going to be using these batts (7 cell piranha 1900 maH btw) in my T3 and the turbo vee boat that'll be here tomorrow. I suppose I'll just take it easy with the boat for the first couple of charges, it will probably help break in the boat motor anyway (I've read how to properly break in motors but don't have the resources to do it how the experts recommend). By peak threshold I guess I meant peak sensitivity, which can be set as high as 20 mv. I figured with that set at 20 mv the charger probably would not detect a peak at that slow of a charge rate (.2 ma), and at that point I could just stop the charge myself after 16 hours. Anyone know if this might work?

Oh and that makes sense why it would take longer than 10 hours, I didn't even think about the heat thing.

DHG

My Feedback: (7)

Rob,

I'm guessing that would work. 20 mV is a big peak; those batteries probably won't show that much of a drop. Anyway, what's the downside risk? It cuts off before 16 hours, and supposedly the battery will be full at that point, unless it was giving you a false peak -- which I've never seen from a nicad pack. The charge rate will still be the very conservative C/10, so it won't damage the cells. The only thing you would lose would be some of the benefit of that "formation charge". Unless you want to beg, borrow, or steal a non-peak-detecting charger, your approach sounds entirely reasonable.

As for breaking in the motor and battery simultaneously on that boat ... I'll give that one a thumbs-up, too. Keep it to half-power or less, just get the feel of it for a while. As one of the graybeards told me when I was breaking in my very first Rossi .15 racing engine: "Resist the urge to hear it scream. Then when the time comes, it will."

D.

robteam70

Well I finally got everything today and am charging one of the new batts as I type. 0.2 amps for 14 hours is my plan (since .2 is just slightly higher than C/10 for these batts I figured I'd just do 14). Thanks for all of the advice Duane. I like that quote btw, reminds me of when I had to break in my new 4 wheeler for 2 hours and keep it under half throttle. Now THAT was tough!