Go Back  RCU Forums > RC Airplanes > Beginners
Reload this Page >

Battery charging calculation formula / advice needed.

Beginners Beginners in RC start here for help.

Battery charging calculation formula / advice needed.

Old 12-02-2018, 06:53 PM
Thread Starter
Join Date: Jun 2003
Location: WI
Posts: 2
Likes: 0
Received 0 Likes on 0 Posts
Lightbulb Battery charging calculation formula / advice needed.

Greetings to all here. Wow, I joined this forum back in 2003 and never did fly much. Not very "super", is it?
Ok, so quick story here . . . . I built my Tower Hobbies .40 trainer over many a winter's night. Some of those nights turned into mornings, I was in deep and loved ever minute of the building process.

Joined the local club here and and had some great instructors. My plane did not pass it's first inspection. It wasn't going to fly that day. Man, that was tough to hear but it was the right thing to do. Seeing that plane lift off the ground and then hear the instructor say how nice it was flying was just incredible. I crashed it a few weeks later after my 2nd or 3rd solo flight. My fault for not plugging in the aileron servo. I still have it, half-fixed but then quickly lost interest.

So recently at the local dump, I happen upon a grungy old trainer that looked fairly good. The guy that runs it always sets aside the "good" stuff. I asked him if he was going to keep it. His reply was "Na, go ahead, you can have it". Very cool indeed. It's a kit built Midwest Aero-Star .40! Gutted but still good. So today, I saw my old instructor. Wow, I immediately felt that the Force is getting strong here. I just mentioned to him about joining the club again. I found his reaction very encouraging.

Anyway, all my equipment is 15 years old. I suppose that's fine for engines and such. What about radio Tx batteries?
I just dug out my Hitec Focus 4 FM transmitter. I have a real nice pack for it (or at least it was).
Japanese Sanyo 2100mAh cells. NiMH, 9.6 volts. I have the Hitec wall charger on them now ( 10.8 v @ 55mA ). Am I wasting time on these old cells. How long of a charge cycle is needed? Should I just buy a new pack? I suppose I could upgrade to a newer transmitter but my old Tx is in really good condition and I must have kept it for a reason, including that old trainer I spent so many hours on.

Thanks for reading,

Last edited by superfly; 12-02-2018 at 06:58 PM. Reason: grammar
Old 12-02-2018, 09:36 PM
Join Date: Jul 2004
Location: White Bear lake, MN
Posts: 334
Likes: 0
Received 11 Likes on 11 Posts

Well, you really, really should replace the pack. Very likely they self discharged long ago, and are now dead. I personally would never trust a pack that old, even if it seems to test well. But if you are determined....plug in the charger, and give them a minimum of 12 hrs. Unplug, and turn on your TX (extend the antenna, keeping it collapsed can harm the electronics). See how long you can go. If you get more than 4 hrs, they at least aren't ruined - although are not trustworthy, as I noted, due to age. If the TX has a voltmeter, keep an eye on it, checking periodically. Running them down too low, even once, can wreck them....
Ditto for your airplane batteries.
And definately do a range check before flying. At 15 yrs, the TX is "young" enough that it shouldn't have developed much in the way of age problems, but there is a possibility, since it is an introductory, "starter" model.
Old 12-02-2018, 09:47 PM
Hydro Junkie
Join Date: Nov 2004
Location: Marysville, WA
Posts: 8,500
Likes: 0
Received 24 Likes on 24 Posts

My thoughts on this are:
1) cycle the pack a couple of times and see how it fairs. A good cycling charger will give you a rough idea of your pack's condition.
2) send in ALL of your radio gear to someplace like Radio South and have it all checked out. If your gear has been inside and not in an unheated garage or a storage shed, it should be in good shape and not really need any work. If it's been exposed to temperature swings and humidity, it might need some work.
3) IF you want to spend the cash or don't trust your equipment, replace everything.
I personally would start with option 2. If your gear is in good shape, this would be the least expensive option. If it has issues, you will find out for just a service fee.
Old 12-03-2018, 01:30 AM
My Feedback: (3)
Join Date: May 2005
Location: Vero Beach, FL
Posts: 600
Likes: 0
Received 0 Likes on 0 Posts

Just a note. If you cycle your pack to check its condition, the important value is how many milliamps come out on the discharge cycle, not how many it puts in on the charge cycle. You want to see at least 75%-80% of the battery's rated capacity.
Old 12-03-2018, 06:11 AM
My Feedback: (2)
j.duncker's Avatar
Join Date: Jun 2004
Location: Sailing in the Eastern Caribbean
Posts: 4,047
Likes: 0
Received 0 Likes on 0 Posts

Unless you already own a cycler I would not bother buying one as the chances are that your tx and rx batteries are unserviceable.

New tx and rx batteries will cost 20 to 30 $ for both.

The peace of mind gained will be priceless.
Old 12-03-2018, 07:18 AM
A. J. Clark
A. J. Clark's Avatar
Join Date: Mar 2004
Location: Craigville, IN
Posts: 466
Likes: 0
Received 1 Like on 1 Post

Myself I wouldn't trust a 15 year old battery. Another note your charger really doesn't have the capacity to charge a 2100mah battery . At 55ma it would take a couple of days to charge and then probably wouldn't reach fully charged.

Last edited by A. J. Clark; 12-03-2018 at 07:21 AM.
Old 12-03-2018, 06:21 PM
Join Date: Dec 2006
Location: Fort Worth, TX
Posts: 7,030
Likes: 0
Received 8 Likes on 8 Posts

The rule of thumb on NiCds is 3 years for a service life. Of course, yours haven't been in service. But the materials inside still break down with time. There is no chance your batteries are still good. Recycle them (not in the trash) and get new ones.
Old 12-03-2018, 07:54 PM
Thread Starter
Join Date: Jun 2003
Location: WI
Posts: 2
Likes: 0
Received 0 Likes on 0 Posts

Thanks for the replies. You cats had it right. Those cells are done. Whatever chemistry was going on is surely not happening now.

That charge indicator needle dropped fast. Like the fuel gauge on my old Suburban.

Picking up new packs for the plane and the Tx.
Now I guess it's AMA membership time once again. Been such a long time.
Old 03-27-2019, 02:58 PM
pmcafee's Avatar
Join Date: May 2018
Location: Riverhead, NY, out on Long Island
Posts: 12
Likes: 0
Received 0 Likes on 0 Posts

What Jester said. Plus, charge the batteries fully as soon as you get them, particularly the NIMH variety. They need an initial formation charge asap or they will go bad and then periodic charging to maintain them. You could use a wall charger connected to a timer and give them a 30 minute charge once a day, as a possibility.

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.