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TL;DR What's the best way to care for NiMH when it comes to charging, use, and storage? This is for 1:14 trucking, so I don't need high-current demands, I just want a set of packs that will take as many cycles as possible before going the way of the recycling centre. I don't need to fast charge - I'm happy to slow charge before events, two packs per truck will last a whole day. Long Version It's been a while since I seriously used NiMH batteries in anything - since moving to LiPo I haven't looked back. But I've got a big truck event this weekend, and due to an administrative error some new LiPos didn't arrive on time, so I bought two new Ripmax 3000mAh NiMH packs from the LHS. They cost me a fair bit - as much as the non-delivered LiPos, which have almost a 40% higher capacity and are, well, LiPos. Back in the good old days, my charging technique for NiMHs was "run it until it slows down, then crank up the clockwork dial to 15 mins and let it run." Remember those clockwork chargers? Terrible, weren't they? When I was racing (and even bashing) on NiMHs, the general attitude was "do a race, then stick it on the fast charger, it'll shut off when it's done." I ran for a few years like that, but mostly I had around 10 packs to choose from and at any one time, a couple of those would be suspect - i.e. not holding a charge or dumping very quickly when used. While some NiMH packs would give me several years of use before heading for the bin (or light duties powering LED displays on the shelf), others would become troublesome within a few months, especially if they were being raced hard and charged hard. The label on the battery says to charge for 14-16 hours at 0.3A (10%). Yesterday I charged both brand new and unused packs at 0.3A and one had a false peak after 70 mins, the other charged for over 7 hours before peaking. This morning I topped off the early-peaked pack at 1A and it took another 60 mins or so of charge. Slightly worrying that these are both brand new packs yet exhibit different characteristics on the same dual charger. So, what's the best way to keep them living long? Should I trickle-charge them at 10% and let the better cells thermal off any excess? I've heard NiMH cells can be damaged even on a trickle charge. Would I be better charging at 0.1A if I'm going to trickle them? That's a very long charge time Should I charge them at 1 - 2A and let the delta peak stop the charge? Or even fast-charge at 3A? What's the best delta to use to protect the battery (vs getting max voltage when the start buzzer sounds?) Should I discharge them before recharging? Should I build a discharging board to discharge each cell individually, or hook the battery up to a low-current application (like running the truck's lights on the workbench for a few hours) to zero all the cells before charging? Is there any mileage in charging each cell individually with a probe, or is that only worth doing if the pack starts to exhibit poor charging / capacity characteristics later down the line? I know there are people here who religiously use NiMH all the time and don't complain about the kind of problems I used to have 10 years ago, so there must be a way to treat them well, especially if I'm not fast-charging them four times a week between races and topping them off until they're boiling to get the very best performance off the starting box.
I've read that in order to determine how long to charge a 7.2v NiMH one should divide the total number of battery mAh by the DC output of the charger, also mA, and factor in a 20% fudge factor. In my case that would be for my 7.2v 5300mAh battery over 35 hours!! Can that be right? 5300mAh for battery/ dc output of charger of 150mA + 20% fudge factor = > 35 hours Should I purchase a battery with a lower mAh? I had read that the higher the mAh of a battery the longer and better performance you could expect. Can someone suggest a charger that has a higher DC output of 150mA? I only have a simple cheap charger that plugs into the wall like a cell phone charger. Any other suggestions? ek
HI guys, I have eagle racing (broadtec) life batteries. I have some charging questions. I went to charge it this morning I followed the chargers directions (think I did anyway) And it only took about 3-4 mins. to charge. It was a brand new battery right out of the box. I`m thinking it came charged for storage and only needed a top up? don`t know. Still new to all this. The only other thing is the amp rate. This had to be set manually, could I have made a mistake and this caused it to not charge. The charger beeped, stopped and said full. I havn`t connected it yet planning to do the electrics today. charger is a hitec x1 ac plus battery Eagle racing (broadtech) li-fe EA2200 35c+ a2p The instructions for this battery came with only Japanese, so I have no hope there. Can anyone shed any light, maybe explain the battery numbers and if you can understand the amp settings from those numbers that would be super. Cheers.
I have been reading a lot on this web site about people being unsure about swtiching to lipo batteries. It is all very safe as long as you use the 'C' rating formula. the formula is this battery capacity x 'C' rating = esc amp draw (using mine as an example) 4.000 x 25 = 100 you need to put a decimal point after the first number of you batteries capacity. 4.0 x 25 = 100 if your esc current drain is greater than what your lipo battery can give you are risking a big 'BANG' as long as you follow this simple formula then all will be ok, for those of you out there that are going to say well mine is fine! well its on your head then think of a lipo battery as a bag (cos it is) when it charges it swells, when it discharges it contracts. ESC's with lipo cut off as you know detects the batteries low voltage point. If the battery is taken past its low voltage point it can be damaged, charge it back up again and after a couple of cycles 'BANG' by using an esc that has a higher current drain than your lipo can give this then in effect is taking too much out of the lipo during its 'burst' (the point when you ask for full power) anyway I hope this all helps and settles a few minds. thanks guys, enjoy.