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Excal's NiMH battery charge time

rickf68

New member
Hi Guys and Gals, Recently bought a used Excal 800 with a NiMH battery pack. What's the regular charge time after a days hunting? I usually hunt about 6 hours at a time. Could I expect to get 2 days of hunting at that rate? If I had a spare battery I guess I wouldn't have to ask you guys. Would be a bummer run out half way through a hunt. Thanks, Rick
 
If its the 1400 Nimh you should get 3 x 6 hours no problems when fully charged the stock nicad battery will do 12 when good at 700, if in doubt give it a few hours on the charger, nimh don't suffer memorry as the nicads do
 
get your self a charger from onlybatterypacks.com it does the job in 2 hours and it has a light that tells you when it's done
 
i charge mine after each hunt..
i use standard charger that comes with it and i have also a fast charger that'll charge pack in about ten minutes or so,then itll condition the pack too if needed
you can get this at your local hobby shop..:clapping::detecting::minelab:
good luck
hh
john
 
Be careful doing fast charges (2 hours or less for a dead pack). It will shorten the life of the battery, more so if the battery is getting hot during charging. Put your hand on it when the charge is near complete. Slightly warmer than room temperture is OK. Hotter than that will really cut down on the pack's life. Quick charging is OK once in a while when you need the pack fast, but it's much healthier for the pack to charge at a slow rate which will normaly take ten hours or so. Some chargers have a thermal probe to monitor pack temperture and will terminate the charge if the pack rises above a certain temperture for this very reason. Some guys will put a fan on the pack while fast charging to keep the temperture down, but it's still not easy on the pack.
 
humm OK ill agree to disagree with you on this about fast charging.....
Ive been fast charging nicads, nimh,and lithos for a long time,Ive never lost a pack from doing this,yes i agree temp has to be right but if you dont fast charge at a high input rate you wont suck a pack...been doing this for many many years in the r/c industry...same type of packs...on the minlab packs they have a thermistor in the pack to keep you from over heating the pack so there's a bit of protection there too..jmo on this...now after fast charging for awhile you should cycle your packs a few times,this will keep them fresh and live allot longer..i fly r/c helis and airplanes been doing this as a 2ND generation modeler since 1969....
hope this helps a bit
good luck to all
hh
john..
 
Before I went to lipos I ran nimh and nicad packs in my planes. At the time I only had some of the cheaper fast chargers on the market to field charge them between flights. A typical pack would take about an hour to charge. I was/am fairly picky about keeping records on my batteries, recording capacity and other data to monitor pack life. Dropping capacity is a good sign that the pack is not long for this world. I was shocked to find out that several of these packs were dropping as much as 25% in capacity after only about 20 to 30 charges. Cycling the packs at low rates to try to recover some of the lost capacity didn't work. The damage was permanent and directly related to quick charging rates. After I stepped up to better chargers that I could control amp rates on and started treating my new packs with a more gentle charge rate I found they were holding their capacity well past the number of cycles the others had on them.

Fast charging alot will shorten the life of the pack. You might not notice the lost capacity until it degrades even further but it can slowly destroy a pack. More so if you allow it to get hot during the charging process. There's nothing wrong with doing it once in a while, but I wouldn't make it routine. I'll do it when I have to have the pack ready in a few hours.

There are times when fast charging is healthy for a pack. If you find the cells have built up internal resistance caused by crystals they can be destroyed and life restored to the pack by charging at a high amp rate. Some people call this shock charging. They charge at a rate that takes say less than an hour to charge a fully dead pack, or they might even charge at a much higher rate, but only for a few minutes to try to break down the crystal formations. I've heard of this method being used on very old nicad packs that have sat dead for years and won't take any kind of charge. Shocking them back into life so to speak.

Another thing to consider about fast versus slow charging is actual run time. I've read articles about this. A slow charged nimh or nicad pack will often have a longer run time (capacity) from it's charge compared to fast charging it the very next flight. The cells are more fully and evenly charged. In the world of RC where an extra minute or two of power can be critical, it can make all the difference between landing and not making it to the runway.

Most lipo packs have a molex balance plug on them wired in parallel so the charger can monitor each cell's charge seperately. Most nicad/nimh don't and the only way to charge them is in series as they are wired. Over time the cells can get badly out of balance, causing some to be over charged and others to be under charged. More than likely if a cell goes bad you can blame it on this. Fast charging is more prone to causing this problem. That's one of the reasons why it's important to drain a nimh/nicad pack dead once in a while.

The reason why it's critical to balance charge lipo packs is because each cell won't tolerate being charged more than 4.2 volts, or drained below 3V. If they get even slightly out of balance it can destroy the pack or even cause a fire. Nimhs/nicads can put up with some abuse for a while and don't pose as much risk, but it's still bad on them.

There are new generations of nimhs that are sold with fast chargers at places like Walmart. These cells are supposed to be able to take the extra heat and punishment, but if you look up the expected number of cycles they are expected to have over a lifetime it's always lower than a normal battery using a normal charge rate.
 
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