Jbo6543 0 Posted June 16, 2008 Hey Guys.... I run my Lunchbox off a 4200 Ni-MH pack. Two alternating packs, actually ("A" and "B"), but I'm having issues with one of the packs. The pack with the issue only produces maybe 40% of the truck speed from when it was working properly, and it doesn't react to full-throttle. Moreover, I have to go from half-throttle to Full, slowly, for the truck to move at all. Lastly, the truck will "buck", like the ESC is thermal'ed, after about 5 minutes. My other working pack has no issues, and produces great run times. I bought the two packs together, with a cheapie "Smart Charger". No difference in the break-in, as there was no break in. I just charged 'em , and off I went. Which leads me to my next question.... Do NI-MH packs need to be broken in, or discharged properly? I thought not, but maybe I'm wrong. I do not have discharge capabilities on my charger, I've seen small appliance lightbulbs hooked up to a tamiya connector for discharging, but is that neccesary for a NI-MH pack? These questions are probably all over the message board, sorry for the redundant questions, and thanks in advance for your help.... Jim Share this post Link to post Share on other sites
taliesin 260 Posted June 16, 2008 i wonder if one of your packs is false peaking and not taking a full charge. the bucking is what the esc will do if the charge in the battery is too low, and is completely normal behavior for a teu-101 on a near empty battery. you probably need a good charger anyway, so now might be the time to buy one. make sure the one you buy has variable charge rates and then set the rate very low so it doesn't false peak and it takes a full charge. fast chargers do this nonsense all too often. i've got one that does the same thing and its frustrating. it will probably just keep doing it until you get a better charger. ps: if you want to make sure your battery is well discharged, just hold the car and keep the throttle part way on until the battery is just too low to spin the wheels. that is plenty discharged. nimh shouldn't need it, but you will know for sure the pack is discharged. then you might ask a friend to charge that pack for you on a good charger and i bet you see an immediate difference. if not, the battery should be very hot and then you will know you have a duff cell and need to get a new pack. Share this post Link to post Share on other sites
TA-Mark 195 Posted June 16, 2008 Sounds like that pack has a problem. Bad plug. Bad connector bar. Broken wire. Bad cell. Heat = expansion which will open a crack in a solder joint. It's very hard to prove a failed pack when it only plays up when hot. I bought 5x 3000mAh packs and 1 of them was faulty with a bad cell. After a few charges it would only charge to 1/2 capacity (Charger shows how many mAh it pushes into the battery). Eventually it would only show a error when connected. The other 4 packs still charge to between 3100 and 3300mAh after 300 orso cycles. Ni-MH don't need to be broken in, nor do they need discharge before recharge. It is a good idea to give the pack several discharge->charge cycles every 20 or so charge only cycles to even the cells in the pack out again. My charger will flash a battery error if there is a failed cell in the pack and won't start the cycle. When it has a partial break in a wire or a joint it will partially charge and carry on when attempting to discharge in a car. Cheers, Mark Share this post Link to post Share on other sites
Backlash 481 Posted June 16, 2008 nor do they need discharge before recharge. Sorry, I beg to differ.. A common problem or fault with the new generation of 4200 + mAh cells is that they self discharge, (this is why we MUST leave them partially charged, otherwise they will discharge themselves down to 0.0V, and possible suffer cell polarity reversal....) This Self Discharge is mostly due to the very low internal resistance of these modern cells.. The problem is that not all of the cells will self discharge at the same rate (some will discharge a lot, some only a little).. This is why we should always discharge then equalize before recharging, to get the all of the cells in the pack back to a state of equal capacity.. If we dont discharge before recharging, what could and probably will happen is that the cell that has retained the most charge will be slightly overcharged before the "peak detection" turns the charger off.. If this overcharging is to great, then a venting or exploding cell is usually the result. Unfortunately it is not easy to equalize stick packs unless you use something like this http://www.modelelectronicscorp.com/browse...duct.php?pid=30 where you can take the cells out of the stick and equalize on a tray after each run.. Share this post Link to post Share on other sites
TA-Mark 195 Posted June 16, 2008 Discharge before recharge implies that you just ran the pack and let it cool but didn't flatten it to 0.0v. Not how you put it, pull a battery from storage and charge. A stored Ni-MH that you left at 40% charge and didn't use for some time will, as you said, need to run a few cycles on the charger before it starts performing to it's peak again. Cycle is the best option if you don't want to disassemble your wrapped stick packs. Sorry I wasn't clearer. Mark Share this post Link to post Share on other sites
DCLXVI 3 Posted June 16, 2008 I'd get a charger with a built in discharger and a display that shows you how much you have charged the pack... Something like this: http://www3.towerhobbies.com/cgi-bin/wti00...=LXMAH9&P=7 Share this post Link to post Share on other sites
Backlash 481 Posted June 16, 2008 Discharge before recharge implies that you just ran the pack and let it cool but didn't flatten it to 0.0v.Not how you put it, pull a battery from storage and charge. A stored Ni-MH that you left at 40% charge and didn't use for some time will, as you said, need to run a few cycles on the charger before it starts performing to it's peak again. Cycle is the best option if you don't want to disassemble your wrapped stick packs. Sorry I wasn't clearer. Mark Look, I dont bash, I race.. Each time I want to charge a pack, be it one that I have had stored partially charged in between meetings, or a pack that I plan to use twice on a race day, I always discharge the pack to 1.0V/cell on my charger, then equalize each cell individually to 0.9V on a tray, then recharge (after the pack has cooled).. In the last 12 months at my club we have had 2 packs explode on 2 racers doing similar things to what you "appear" to be suggesting.. The first fellow decided he would save himself some time on race day by charging all his packs the night before, and then re-peak them on the day.. When he was re-peaking his pack, 1 cell started to vent, and then exploded minutes later.. We found the cell casing some 30+Metres away, and it grazed another racers leg that was standing near it when it went off.. The second was to an experienced racer that had done only 1 or 2 laps in a race and then broke his car.. He figured he would just re-peak that pack and use it for the next heat.. 1 cell exploded whilst it was on charge causing some minor damage to the car in the process.. Luckily no-one was seriously hurt in either incident.. Share this post Link to post Share on other sites
TA-Mark 195 Posted June 16, 2008 Meh... Where did I mention re-peaking Ni-MH cells? Every charger instruction manual should tell you not to do that. I said run it in the car (ie: car is barely moving if at all... almost flat... must've been unclear again) and straight to recharge cycle after cooling. Where did I say drive 2 laps then charge the battery? Where did common sense go? Better question is, were these morons banned from your club? My charger would turn on for about 30sec @ 0.1A if I plugged a charged pack to it. I've not done it, I know that because I read the very lengthy instruction manual. Not everyone's charger has bells and whistles. If it's a timed charger and not a peak detect then definately discharge it first (all the literature that came with my charger recommended 0.8v minimum voltage on discharge). Cheap chargers have poor peak detecting so monitor cell temperature (all six not just one of the cells). Quick grab of the pack will soon tell if one cell is cooking hot and five are cold. One cell warmer than the rest means it needs a cycle. I race. I bash too, it's all fun. I have my own track. There are 4 other tracks in my local area, all privately owned. One of our rules is pre-assembled stick packs only. Keeps the racing fair. Not all of us make enough $ to spend on fancy setups. I do, but many of the others don't. Long way from here to any sanctioned event so they can stick their stupid rules. We run by what is fair for all who want to drive whether they are a 15yr old on study allowance or a businessman making $200k/yr. If one guy decides to run built packs he disassembles each charge to balance out perfect then all need to do it to keep competitive hence that poor 15yr old who can't afford it gets to leave his car at home or just drive at the tail end for the heck of it. Our "everyone" class is a stock buggy with bearings, Tamiya 101 ESC and a 3000mAh Venom pack, no mods allowed. It's a cheap and attainable level for anyone. Even my 11yr old son saved his own pocket money and bought himself a DF03. More mug anyone that turns up with a stock belt drive buggy. Last person who attempted that didn't complete the first lap before his belt started slipping (Durga - dust build up in the pulley teeth, packs in like concrete). Our open class is a different story. Anything goes nearly. As long as it's the right scale and electric. There are only a few at the club that run this class due to the expenses and speeds involved. I run 3s2p Li-Po saddle packs and MambaMax 5700Kv for this car, obviously not legal at your club... or is it that it's too fast and you don't want to make everyone "keep up with the Jones's"? You don't want to be stuffing around with individual cells for a bash. Quick easy run is what most aim for. Less time preparing and more time driving. Pull out those packs you left 40% charged last weekend, run a few discharge->charge cycles over them, head out for the drive, throw in that pack that has lost it's peak by now and off you go... it's only for fun, who needs perfect launch with max battery in this situation? Let car and battery cool, throw in next pack that was charged at home and throw the spent one on the charger for a charge only cycle. Repeat driving/cooling/charging until bored. When you get home charge the flat packs back to 40% and store for the next outing. 6 packs and 2 cars and you drive non stop. If you discharge each cell individually why don't you also charge them individually? Will peak each cell perfect. Mine will charge a single cell. The battery tube looks to be a good idea. Would make running single cells much easier for those with poor soldering ability. Still not something I would want to bash with, nor race with. Li-Po is lighter and more power for racing. The only dead pack/cell I've ever had in my 25ish years of playing is a Venom 3000 that was a dud from the packet. Shop very nicely replaced it for me the next day. Mark Share this post Link to post Share on other sites
grizy 12 Posted June 17, 2008 TA-Mark, Backlash, Cmon guys play nicely But seriously, people like myself look to guys like you with years of experience to learn from and get more out of the sport. I bash, have done intermittantly for 20-odd years, but over that time chassis, radios, batteries, ESCs chargers have changed greatly. I have thought about racing but after being told about the 100 weight of equipment required to be competitive I was somewhat put off it. Not that I won't dip my toe in that scene in the future. Mark, The basic setup class you have at your local club sounds great. Those 15yr olds with limited budget will someday become working adults with a much bigger budget. A great way to get addicted to the sport. Backlash, There's nothing wrong with bashing , its great fun. Im sure you didn't mean that (there was anything wrong with bashing) when you said you don't bash. Any way, back to the point, NiCads, NiMhs, LiPos, what ever batteries you use - incorrectly charging, over-charging or depleting them too much can render them useless or they can explode/set on fire? Is there a source of comprehensive info (or can you guys put one together) on charging the different types of batteries? Cheers Grizy Share this post Link to post Share on other sites
Backlash 481 Posted June 17, 2008 TA Mark, grizy, Jbo6543 and fellow Tamiyaclub members, sorry if I have caused offence, it was not my intention.. IMO, I feel that we have a responsibility to be as clear as possible when posting on the forums, so as to not be misinterpreted by our members (and guests) that have English as a second language.. My initial comment was made in regard to Mark's statement ", nor do they need discharge before recharge." (as quoted in my first post).. OK, I read what Mark has written, how it was written, and disagree with it.... I say NiMh do need to be discharged before recharge.... Yep, its called an opinion, and everyone has one... You get that.. grizy, I'm not sure if you were trying to make a point here or not, but no, there is nothing wrong with bashing and from what i can see, i didnt say that there was, (but I didnt said their wasnt either, aye Sometimes it is not what you say, its what you DON'T say that's improtant).. I dont bash as such, but I do play with my crawlers in my garden, and also my tanks and 1/14 trucks / rigs in the house.. Do I consider this bashing, no.. Bashing to me is like unorganised racing (or orgainised chaos ).. Cheers Share this post Link to post Share on other sites
Taman 3 Posted June 17, 2008 Hi All, Interestign post, I have a few questions about recharging an Ni-mh. Sometimes I charge my 3000Mi-Nh battery the night before then top it up the next morning before I take my car for a quick spin, is this ok? I've got an Ansmann charger with Peak detection so I was under the impression the charger would limit the amount of charge to what the battery requires? How do you know if your battery is venting? Cheers Share this post Link to post Share on other sites
TA-Mark 195 Posted June 17, 2008 That is re-peaking an already charged battery. Both Backlash and I suggested this was a bad idea. Backlash showed an example of it going bang while doing this. Run the battery in the car as it sits from the previous night's charge. Then recharge. Or cycle it if the charger supports it. Bashing and thrashing, one is driving around other than racing, the other is attempting to destroy a car whether racing or not. Thrash is what I do to my Savage. The rest I bash (drive) or race. Share this post Link to post Share on other sites
