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NiMh Condition Testing

Old 04-03-2021, 05:46 AM
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golf4two
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Default NiMh Condition Testing

Slowly converting all of my old NiMh packs (eneloop 1900 ma packs mostly) to Life packs. But with 14 airplanes and a few "spare" packs, that can get a bit expensive if done all at once.((and at my age may do nothing more than make my estate sale more attractive!)).
Anyway, my question is:
What is a "reasonable" discharge rate to set when cycling these old packs to test their overall condition?
Yeah, I know the old advice to "charge, fly a few flights, recharge and that will tell you how many flights you can get."
That's NOT what I'm after. I want to know before hand their condition as some of these packs have been laying around a while.
I've been charging at 200 ma and discharging at 300 ma. Results sometimes (on the same pack) don't seem realistic (low or high). If it makes any difference, it's an Hitec X4 80charger which has been pretty reliable over the years.
Again, I wish to determine the condition of the packs, not how many flights I can get.
Also, what would a realistic cutoff voltage be for a 4 cell and a 5 cell pack?

Last edited by golf4two; 04-03-2021 at 08:25 AM. Reason: corrected charger ident
Old 04-03-2021, 08:41 AM
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A. J. Clark
 
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I've also been converting nimh packs to LiFe. For the nimhs I have been charging at .1C and discharging at .2C. Sence the life batteries use a balance lead I have mounted the batteries so they can be removed easily to charge. Being that they are easily removable I have 3 LiFe batteries that I share between different planes.
Old 04-03-2021, 04:46 PM
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golf4two
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Default Great Idea!

Originally Posted by A. J. Clark View Post
I've also been converting nimh packs to LiFe. For the nimhs I have been charging at .1C and discharging at .2C. Sence the life batteries use a balance lead I have mounted the batteries so they can be removed easily to charge. Being that they are easily removable I have 3 LiFe batteries that I share between different planes.
Good idea to keep just a few flight batteries and charge/install as desired. Most of my airframes are old school balsa nitro and gasser kits...didn't give too much thought to removing batteries so that can sometimes be a chore. IF I build any more I'll certainly keep that in mind.
Would still like to sort out these older batteries though.
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Old 04-03-2021, 07:55 PM
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049flyer
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I charge at C/10 or 1/10th of the capacity for 12 hours or so, and discharge at C/2 or 1/2 the capacity. I discard the battery if I canít obtain at least 80% of itís rated capacity. Sometimes it takes a few cycles to get the required capacity but if I canít get to the 80% minimum after 3 charge/discharge cycles I toss it.

Some NIMH batteries tolerate fast charging at a 1C or 1/2C rate, but not all batteries will.

Here is some great info on batteries:

Red's Battery Clinic


Last edited by 049flyer; 04-03-2021 at 08:00 PM.
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Old 04-07-2021, 12:23 PM
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Zeeb
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Originally Posted by golf4two View Post
Good idea to keep just a few flight batteries and charge/install as desired. Most of my airframes are old school balsa nitro and gasser kits...didn't give too much thought to removing batteries so that can sometimes be a chore. IF I build any more I'll certainly keep that in mind.
Would still like to sort out these older batteries though.
LiFe/A123's can be charged in the model. Since they are just rx packs, I use FMA chargers which can do a node (balance lead) only charging without disconnecting them from the model. AFAIK, FMA/Revolectrix is the only company building a node only charger in the CellPro 4S Multi. You can buy extensions for the various types of connectors found on batteries, typically a JH JST type connector.
Old 04-07-2021, 12:24 PM
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Double post.
Old 04-07-2021, 01:08 PM
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Discharge rate for testing Nixx batteries can vary all over the place depending on how the individual cells are rated. Most cells sold these days don't even have a data sheet available from the no name mfgr. Discharge at a too high rate and even new cells will test poorly. Smaller cells need to be tested at a lower % of rated capacity than larger capacity cells. For small cells like 500 MAh, to maybe 1000 MAh, you're probably safe testing at something like a C/3 rate for new cells and maybe C/4 for older cells. For larger capacity cells over 1000 MAh or so, a C/3 rate should be safe. These values are not set in stone, just rough guesstimates but I'd never test any Nixx battery over the C/3 rate. No consumer grade Nixx battery was ever rated at the C/1 rate. By comparison, many Lixx batteries can be capacity tested at the C/1 rate as they are much better at delivering high current discharge rates compared to Nixx batteries.

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