Popriv

I have an old Nicad wall wart charger, 50 Mah...
Can I use this for my Nimh RX battery?

This charger is probably 20 years old?

50 Mah is 50 Mah, whats the difference if its going into a nicad or an Nimh battery.

I would use this for initial slow charges on new batteries...

I've been using a Hobbico quick field charger set at its lowest charge setting of .2 for my regular chargingand it has been working ok.

Just wondering if I could use this nicad charger??

Gee, just thinking? is .2 on my hobbico less voltage than the 50 Mah on the wall wart????

Thanks

Steve

TFF

VOltage and amperage are two different things. 50 mah would be set as .05 on your field charger if it could go that low; voltage should be the same if set right. Wall chargers are designed to charge at one tenth of the total pack so you wall charger is designed for batteries at 500-600 mah. How big is the battery?

Jetdesign

My Feedback: (8)

The difference in charging Nicad and Nimh batteries has to do with peak detection. Wall warts are not 'peak' chargers so you can use your charger with either kind of battery. I use wall warts to charge my high capacity nimh and nicad Rx and Tx packs, and use an appropriate peak charger on the proper setting for peak charging.

50ma would charge a 500mah battery in a little over 10 hours, and would charge a 2000mah battery in over 40 hours.

Rodney

Pretty much as gaRCfield said. To get the exact time it will take to charge your battery, just divide the capacity by the charge current and multiply by 1.4 to account for the inefficiencies of the charge function. Note that the stated capacity of most wall warts are a nominal value, seldom if ever exact and the current will vary slightly between when the battery is nearly discharged and when it approaches full charge. This is because they are not a true "constant current" charger, just an economical circuit that approaches a constant current charger. To be sure, you need to insert an ammeter in series with the charge leads and measure the current. The nice thing about using the wall warts, they are much easier on your battery than a fast charger is plus, if you forget and leave them on for long periods of time, the battery will not be damaged.

Popriv

My current RX battery is a Nimh 1700 mah.
so is my 50 mah charger to low for this battery or it will just take longer. (a 170 mah charger would take 10 hours on this battery? so I'm looking at 30ish hours with the 50 mah charger?)

I've been watching my field charger while charging with a meter connected and I can see that when the charger gets to about 6.02 it will drop back down to 6.0 and this is when the charger alerts and shuts down. So I can see that it rises slowly in voltage and when it detects the slight drop it stops.
I usually charge at .2 which is the lowest marking on the charger although the dial goes lower. It may be going as low as .15 ??
It usually takes about 1 hour to top it off.


I know a slow low charge is better for the battery so would I be better off using the 50 wall wart at home between flying sessions and save the field charger for at the field when I need a faster charge? or is the .2 charge low enough? also I heard its better for the first couple of charges on a new battery to go low & slow until the battery is "conditioned" (probably the wrong term)

If I were to use the wall wart should I put it on a timer to shut it down or is it safe to keep pumping in the 50mahs?


Thanks

Steve

jetmech05

mah is mili amp hour..in other words a 1700 mah battery will deliver 1700 miliamps for 1 hour or 1 miliamp for 1700 hours (in a perfect circuit) it is a means to show the capacity of a battery....now charge current is measured in miliamps as your wall wart puts out 50 miliamps..miliamps is a measure of current....
just some info for ya...Good flyin to all

jrcaster

The difference in Nicad and NiMh, is that the Nicad is a more robust cell. It will tolerate overcharging more than the NiMh will, but the NiMh will discharge at a higer rate.

That being said, use the field charger on the 1700mah pack, and set it as close to 170ma or .170A as you can. This is your slow charge rate for the pack. This should take 10 to 14 hours to charge a fully discharged cell. This charge rate is known as C/10 or 1/10th of the battery packs capacity. After the charger detects the peak, it will cut back to a 50mah or .05Ah trickle charge. Here is where the difference in robustness of the cells differ. The NiCd can stay on the trickle charge for a couple of days without damaging the pack where the NiMh pack should be removed within a few hours. After the peak detect, any charge current going to the pack is being dissipated as heat.

At the field to fast charge the pack, it should be able to withstand 1Ah charge rate without damage. I am assuming that the batteries in the pack are physically the size of AA batteries. Keep a part of the pack to were you can lay a finger or two on it and check to see if it is warming up. Usually a NiCad or NiMh pack won't start heating up till it gets close to peak.

For more information on rechargeable batteries go here.
http://www.rcbatteryclinic.com/welcome.htm

carrellh

Steve

The 0.2 rate is only slightly over 1/10 of the rated capacity so it is not likely to damage the pack. It would take 8.5 to 11.9 hours to charge the pack if it was fully discharged.

The 50 mah wall wart will take 34 to 47 hours to charge the pack if it is fully discharged.

From http://www.hangtimes.com/rcbattery_faq.html

Q: What's up with 'Formation Charging'? Can't I just charge and fly a new pack?

A: The term 'Formation Charging' describes the initial charge/discharge 'forming' process that fully activates the 'chemical engine' and balances the cells in a new pack. NiMH packs have a particular need for repetitive c/10 charge/cycle conditioning, a 'break-in' procedure needed to get them to full rated capacity. Both NiMH and Nicad packs benefit from the process and the intent is to make sure that any new pack has been verified to be fully operational and that a 'start-up' capacity number is established for the pack before it's put into service. To 'Form' a new NiMH pack do three 10% 16-24 hour charges followed by a 300 to 500 ma discharge routine between each charge. In other words: Do a slow charge at the slow charge rate (or as close to it as you can reasonably get with your equipment) as shown on the pack label. Charge till the pack is warm, followed by a controlled discharge with a cycler. Do it 3 times. The recommended Formation Charge/ Slow Charge rate for our packs is printed right on the label of the pack as well as on the data card the pack was shipped with. New Nicad packs should get at least one slow charge followed by a 300 to 500ma discharge. Record the capacity numbers reported by your equipment for comparison cycling as the pack ages. Never check your brain at the door! As one respected modeler put it, "There's nothing more suspect than a new battery pack." Before you fly anybody's pack be certain it's fully operational and safe to fly.

jetmech05

a charger can not put out mah (miliamp hour) a charger can only put out ma (mili amps)
mah is a way of describing a battery's capacity to deliver ma..
Good flying to all

TFF

The wall wart probably does not have enough push to overcome the internal resistance of the batteries and really charge them. It is only charging at 1/34C and 1/10C is considered slow. What the battery is absorbing may be as small as 5mah if any. Your field charger set at .2 is pretty close to the ideal .17 so you are pretty good. It also proves you are only using up 200-300 mah of the battery capacity if it is taking an hour to charge.