Hey Guys, I've had a new Ni-mh battery for my trainer and I've used it quite a bit an all the sudden it's not holding a charge longer then one flight. I did some checking and found out I was charging this battery with my home charger which is for Ni-cd only! I thought the new battery was a Ni-cd and didn't realize it was a Ni-mh....can I still use this battery and charge it the right way or is it toast?

I was lucky I got the plane down when I did the volt meter was on red!

NiCad and NiMh are very similar batteries and , in general, can use the same charger unless you are using a fast charger that cuts off when the charge peaks. In general, a NiCad peak is more pronounced than a NiMh so, if using a NiCad fast charger on a NiMh you may not detect the peak and overcharge the NiMh. Check out www.rcbatteryclinic.com for some good advice on the care of all types of batteries.

you may also want to verify the your battery capacity divided by 10 is equal to the charge rate of your wall charger. if the battery is larger then you are not getting a complete charge on your battery.

What kind of charger is your "home charger?" is it a wall charger like the one that came with your radio system? or is it a more sophisticated unit such as a Triton or other which has the ability to charge many different types of batteries of different voltages, and capacities?

Also, what is the capacity of your NiMH, and what is the charger's voltage and current?

If you're using the wall charger that came with your radio, most likely it's charging your battery at the overnight rate. This rate is really too low to do any damage, and you can use it to charge a NiMH or NiCd safely (arguably the best way to charge your batteries).

Did this happen more than once, or was it a one time occurence that's now freaking you out a little?

Usually, when a battery goes bad, it does it gradually. First, you'll find that you can make one less flight than usual, then a few weeks later 2 less flights, etc. If you've been flying for months taking numerous flights on one charge, then all of a sudden the battery goes dead after one flight, it's more likely something else is going on.

Other likely causes:
1. Battery didn't get fully charged due to a wall switch being turned off.
2. Battery didn't get fully charged due to a bad charge jack/switch.
3. Battery didn't get fully charged due to a bad charger connector.
4. Your voltmeter has bad connectors (I've had this happen)

If your battery really is going bad, the only way to check its capacity is by cycling it. There are plenty of cyclers for RC use. This is probably a good idea to have a cycler in your arsenal if you plan on staying in RC for a while.

As Rodney said, check out rcbatteryclinic. Lots of good info and advice.

pattern, from what your saying it sounds like my battery might still be good then. The charger I've been using is that cheap wall plug in type that came with my Alpha 40. This has only happened once and the battery is a 1500 mh(?), it did have a 600 nicad but I wanted longer charged times for more flying. I do have a quick charger that will charge the 1500 ni-mh, I plan on charging it up with that and see what happens. The flying times never dropped slowly but this once and it was quick. I'm guessing it never got charged to full capacity.

I bought another 700 ni-cad and charged it up and the volt meter reads in the green like it's suppose too. I'll check out rcbatteryclinic...sounds like a cool site.

I have a 1500mAh NiMh pack in one of my planes, and the stock, 700mAh JR Sport packs in 5 others. I use the same wall charger that comes with the JR Sport systems for all of my batteries and have noticed no ill effects on the NiMh pack. It charges and holds a charge just like the NiCd packs, it just gives me more flights.

Good luck.

Hi Pyw,

From what you've said, it sounds to me like your nimh is probably still ok. Like I said, the only way to be sure is to cycle it. Find a friend who can do this for you on their cycler. If you plan to stay in the hobby a while, it might be a good idea to get one for yourself.

So the low capacity happened only once, and now you're a little spooked. That's a good thing, 'cause it's an indication that something went wrong and you'd like to correct it. Hopefully, nothing was damaged. I think there's a good chance that after charging again (even with the wall charger), you'll find that the battery is fine. But now, you've just revealed a problem that needs fixing.

It's worth revisiting the way you charge your batteries. Do you put it on charge the night before flying? Always? How long is it on charge before you disconnect it? Do you charge a few days before, then disconnect it? - this would be bad because NiMH and NiCds self discharge.

Before you take your first flight of the day, do you check it with a voltmeter? It's also important to use a loaded voltmeter, otherwise your reading will be irrelevant. Also, when you plug your voltmeter into the battery, does it give a stable reading or does it fluctuate. If it fluctuates, then the connection isn't good, and that could mean that either you're not getting a good reading on the voltmeter, and/or you're not getting a full charge when you plug the charger into the battery.

Also know that the wall charger you're using is meant to charge the lower capacity battery that came with your Alpha40. I'm guessing the charger puts out 4.8Volts at 60-70 ma. This is the overnight C/10 rate for a 700 maH battery. For a proper overnight charge for your NiMH, C/10 would be 150ma.

Check out the wall charger specs (this info should be on the charger). If so, then charging your 1500 maH NiMH could take twice as long (32 hrs instead of 16). Still, it's no guarantee that your NiMH will be fully charged. 150ma would be better. Do a few experiments with a cycler. Using the wall charger on a depleted battery, charge for 16 hrs, cycle it, then note the capacity, then discharge it and repeat after charging it for 32 hrs.

There are many acceptable ways to charge your batteries. I've read that some people quick charge on the way to the field. Others swear by the overnight charging scheme. Personally, I think that quick charging is a little hard on the batteries and when you do it regularly, you could prematurely age the batteries. On the other hand, you're pretty much guaranteed a freshly charged pack when you get to the field.

After you determine that your battery is healthy, if you still experience the low capacity, then there is another more serious problem on board your plane. It could be a short, or even a jammed servo. A jammed servo would be draining your battery pretty quickly. Listen for buzzing servos while all your sticks are at idle.

Good luck.