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Model Forum / Radio Controlled / Air Models / February 2004still confused over batteries...can you experts help me
Ok guys...and gals aswell ill go through this one more time and make it simple: Ive been to other R/C user groups besides this one and this forum is my last hope. Got so many different answers on the subject at different R/C groups. Been to "Reds" Battery Clinic web site for answers.Soooo...here goes: A. My battery charger: MRC Super Brain 959 Deta Peak Charger, will charge 3 to 8 cell NIcd and NImh batteries. I can adjust the charge current rate from 0.5 to 4.5 amp and adjust the delta peak voltage threshold from 5mV to 70mV ( what does. It has Plug 'n Play and will detect and set the peak charge before charging. B. I have a 6 cell Nimh 7.2 volt 750mAh pack that I made...its new...and want to charge it C. IF I am correct Nimh can false peak. D. What would... YOU... battery experts out there select as a charge rate in the amp setting and mV setting and time aswell to charge the above menttioned pack. E. Some of the answers I got on other R/C groups: 1. charge at 1.5 amps.....70mV 16 hours 2. charge at 0.5amps to 1amp at 5mV/cell....wich sounds like to me ( either 0.5 to 1 amp at 30mV ( 6 cell at 5mV = 30 mV) 3. charge at 0.5 and let the charger detect the peak...charge it then let the charger trikle untill it shuts off. F. I here alot af flack about making your own pack ( I do) so what is the real deal about it. I know it can be dangerous, it can ruin the cells. But it can be done and alot of us do it. Ive done it (destroyed my first pack) but made a second one.....came out fine....I learned from my mistakes on the first. Please help.....all answers and opinions, negative or positive are welcomed thanks for helping Mike P.S. Dr1Driver will probally tell me to switch to nitro.....lol :) ( by the way Driver, I do have a nitro seaplane......hehehehe ) To be on the safe side, always charge at 1/10th of the battery capacity in mAh for 10 hours and that's with an empty pack and as long as the voltage is a bit above the pack. So for your 6 cells pack, that'll be: 3/4 amp charge rate at 9 to 12 volts. voltage is not that important as long as it is a bit above the rated pack. Voltage pushes the amps in the battery. What burned your pack is the charging rate in mAh that was too high, not the voltage. > Ok guys...and gals aswell ill go through this one more time and make > it simple: [quoted text clipped - 38 lines] > > ( by the way Driver, I do have a nitro seaplane......hehehehe ) > Ok guys...and gals aswell ill go through this one more time and make > it simple: [quoted text clipped - 9 lines] > B. I have a 6 cell Nimh 7.2 volt 750mAh pack that I made...its > new...and want to charge it I'm not too sure about specific delta voltages, but if you want to get the pack going without having to worry about specific cutoff voltages, just trickle charge the pack at C/10 to start with - that is, charge at 75mA for 15 hours (it is almost impossible to "overcharge" a pack at this rate). For a new pack, particularly NiMH, I find you need to cycle the pack a few times to get it to deliver full capacity, so you might want to discharge it to 1 volt per cell (6V) then give it another trickle charge. This is a slow way to charge it, but it will get you going, and you can be confident you've fully charged the battery. When you discharge, many chargers will tell you the total mAH delivered by the battery - you can use this figure to check whether other charging methods are putting enough into the battery before cutting out. As for fast charging, I think 2C tends to be the max rate for NiMH, so that means a max charge current of 1.5 Amps. If you want to experiment, discharge the battery to 6V, then try a 1.5A charge on auto. It should cut out after 30-40 minutes. Any longer and you know it's missing the peak. Much shorter and either you know you didn't discharge the battery enough, or the charger is false-peaking and cutting out early, so you'll have to experiment with manual delta peak values. You should do a discharge and compare the mAH delivered to what you got with a trickle charge. With a bit of careful, structured experimentation, you should be able to work out the ideal charge rate and delta voltage. Russ. | C. IF I am correct Nimh can false peak. Of course it can. | D. What would... YOU... battery experts out there select as a charge | rate in the amp setting and mV setting and time aswell to charge the | above menttioned pack. 750 mAh pack? For NiMH packs I've never had much luck going over 1 C, so I'd suggest a charge rate no higher than 750 mA. (The Sub C NiMH cells used by the car guys might be able to go higher, but I don't usually use those.) I don't know about the deltaV that you're looking for -- your charger documentation should tell you, or it should just figure it out on it's own once you tell it NiCd or NiMH. Once the charge is complete, you can trickle at C/10 or so for a little while to make sure the pack is fully charged, but don't leave it like that for a long time -- it'll wear out your battery. | F. I here alot af flack about making your own pack ( I do) so what | is the real deal about it. Make all the packs you want. If you ruin some cells, I'm sure the store has a few more they'll sell you :) It's not a bad idea to cycle any new packs you make to make sure the capacity is what you expect. If it isn't, you may have damaged the cells. But once you figure out how to do it, you're not going to ruin many cells, and you can save lots of money making your own packs.  SignatureDoug McLaren, dougmc@frenzy.com `The lesser of two evils ... is still evil.' Whu not do a search on charging batteries. Amazing what you can find with a little effort. When someones gives you an answer to a question as DR1 Driver did for you a few days ago and you smart off at him, it makes some people less enthused about going to a lot of trouble to help you. Ken Day >Ok guys...and gals aswell ill go through this one more time and make >it simple: [quoted text clipped - 38 lines] > > ( by the way Driver, I do have a nitro seaplane......hehehehe ) > Whu not do a search on charging batteries. Amazing what you can find > with a little effort. [quoted text clipped - 47 lines] > > > > ( by the way Driver, I do have a nitro seaplane......hehehehe ) Was not smarting off just having alittle fun...take it for whats it worth....Driver likes what he models and I like what I model....I like Park Flyers, he doesent.....freedom of choice on this little planet we live on...I hope he is having fun as you are aswell at what you like to do.....whats important everbody should be happy at what they are modelling: cars, planes,boats, ect... Sorry to have offended.. Mike I believe you are asking about motor/flight packs. My experience with NiMhs has been with receiver packs, so you may or may not find this helpful. When I began converting to NiMh receiver packs, I had to experiment quite a bit to get reliable performance. I found that if you throw the NiMhs on a fast charger (like a NiCd) and charge over 1C, you get false peaks and incomplete charges. Here is what gave me the best results: 1) Use a C/10 (trickle charge) rate for the first few charges. I didn't find it necessary to completely drain the batteries. Discharge them by using them in the intended application, and recharge at the trickle charge rate. 2) After a couple or three of these 'use and trickle charge' cycles, I moved to my fast charger. I found that the most reliable, complete charge came between 3/4 - 1 C (eg. ~900 mAh for a 1200Ah battery). I also increased the peak detect to 4 mV from the charger's default of 3 for NiMh. I experimented with 5 mV, but got the same results as 4. The false peaks seem to be tied more to the charge rate rather than peak detection value. Using this method I can reliably get a complete charge/discharge at the pack's rated capacity (using a Dymond Super Turbo Charger). When I try to speed up the process (going over 1 C), I might or might not get a full capacity charge. Good luck. > Ok guys...and gals aswell ill go through this one more time and make > it simple: [quoted text clipped - 38 lines] > > ( by the way Driver, I do have a nitro seaplane......hehehehe ) > I believe you are asking about motor/flight packs. My experience with > NiMhs has been with receiver packs, so you may or may not find this [quoted text clipped - 66 lines] > > > > ( by the way Driver, I do have a nitro seaplane......hehehehe ) Thanks for help. MRC finally got back to me and I have to say you guys are right on target.....u "vets" know ur batteries Thanks again Mike |
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