Nicads idividually test out OK, but don't take a full charge.
02-23-2006, 04:22 PM
#1
Nicads idividually test out OK, but don't take a full charge.
These are old batteries. I made a single 4.8 volt 4AA receiver pack compiled from 4 batteries out of 8 loose batteries, after tossing 2 bad batterries. I proceeeded tp put together 4 of the 6 loose batteries that I had left over, to make one 4.8 volt RX battery 4 pack.
I individually tested each of the 4 AA sanyo cells in the battery pack to show "green" or "OK" on my Radio Shack battery tester. I then tested the whole battery pack to find it to give a reading of 4.9 Volts on the Hobbico voltmeter. As you know, a good reading and safe to fly fully charged pack usually reads about 5.2 or 5.3 volts on a Hobbico voltmeter. 4.9 volts is low and rated as "marginal" or "risky" (but not dead).
However,when I tried to put this 4AA pack on my standard ACCUCYCLER to cycle it, it refused to discharge, and it automatically started charging. Evidently, it had so small an MAH content in it, that there wasn't enough juice to discharge. After 16 hours of charging I then attempted to cycle it once more by discharging it again. Again, it would not discharge, and would only start with another 16 hour charging process
What's strange is that I checked the pack and each cell individually again, and could find no stand out battery that was a problem.Each cell was still in the green on my Radio shack battery checker, but the pack still stubbornly reading 4.9 volts.
I individually tested each of the 4 AA sanyo cells in the battery pack to show "green" or "OK" on my Radio Shack battery tester. I then tested the whole battery pack to find it to give a reading of 4.9 Volts on the Hobbico voltmeter. As you know, a good reading and safe to fly fully charged pack usually reads about 5.2 or 5.3 volts on a Hobbico voltmeter. 4.9 volts is low and rated as "marginal" or "risky" (but not dead).
However,when I tried to put this 4AA pack on my standard ACCUCYCLER to cycle it, it refused to discharge, and it automatically started charging. Evidently, it had so small an MAH content in it, that there wasn't enough juice to discharge. After 16 hours of charging I then attempted to cycle it once more by discharging it again. Again, it would not discharge, and would only start with another 16 hour charging process
What's strange is that I checked the pack and each cell individually again, and could find no stand out battery that was a problem.Each cell was still in the green on my Radio shack battery checker, but the pack still stubbornly reading 4.9 volts.
02-23-2006, 04:31 PM
#2
RE: Nicads idividually test out OK, but don't take a full charge.
Have you got a digital voltmeter to verify the readings. Especially that the AcuCycler is putting out a C/10 charge and a loaded reading on the individual batteries. A #46 bulb will load the 4.8 volt pack about 220 mA. Many times in the past I've found what I thought to be a problem was because of innaccurate meter readings.
John
John
02-24-2006, 12:28 AM
#3
RE: Nicads idividually test out OK, but don't take a full charge.
Yes, I am using a Hobbico digital voltmeter with leads that have a Futaba jack on it to plug into my battery packs. This is how I determined the "4.9 volt" readings I keep getting.
Hmmmm.....I suppose I could make single negative and positive probe style leads for this Hobbico digital voltmeter so I can test individual cells with it......and see how the readings stack up against the radio shack voltmeter. It's funny how the Hobbico voltmeter was designed for "packs" and shows a chart to measure and rate the strength of the battery pack readings. Silly me.....I got use to using the Radio shack tester, and never thought of making up seperate test leads for the Hobbico volt meter to test individual cells.
Hmmmm.....I suppose I could make single negative and positive probe style leads for this Hobbico digital voltmeter so I can test individual cells with it......and see how the readings stack up against the radio shack voltmeter. It's funny how the Hobbico voltmeter was designed for "packs" and shows a chart to measure and rate the strength of the battery pack readings. Silly me.....I got use to using the Radio shack tester, and never thought of making up seperate test leads for the Hobbico volt meter to test individual cells.
02-24-2006, 10:26 AM
#4
RE: Nicads idividually test out OK, but don't take a full charge.
OK, I used the Hobbico digital Voltmeter meter to test the individual cells. 3 of the cells registered between 1.41 and 1.42 volts, and the 4th cell tested at 1.38 volts. I replaced the 1.38 cell, charged the pack over night, and now the pack is charging at a full 5.6.
THE BOTTOM LINE:
1)YOU NEED A DIGITAL VOLT METER TO WEED OUT AND FIND THE SMALL DIFFERENCES BETWEEN CELLS IN A PACK. (IF A CELL IS WEAK, BUT NOT DEAD).
2)UNLESS YOU ENJOY TINKERING AROUND FOREVER LIKE I DID, JUST THROW OUT YOUR OLD CELLS WHEN THEY ARE A FEW YEARS OLD!!!!!!!
THE BOTTOM LINE:
1)YOU NEED A DIGITAL VOLT METER TO WEED OUT AND FIND THE SMALL DIFFERENCES BETWEEN CELLS IN A PACK. (IF A CELL IS WEAK, BUT NOT DEAD).
2)UNLESS YOU ENJOY TINKERING AROUND FOREVER LIKE I DID, JUST THROW OUT YOUR OLD CELLS WHEN THEY ARE A FEW YEARS OLD!!!!!!!
02-24-2006, 12:04 PM
#6
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RE: Nicads idividually test out OK, but don't take a full charge.
Yup, I too have found that when one cell in a pack goes down the others are very close to following it. I use these 'good' cells around the house to power other non critical things - TV remote controllers etc!
It's better in my view to replace packs when they show a deteriation in capacity (down to 80%) than judge them by age. Manufactured objects, batteries included, are most likely to fail at the beginning of their life or much later as they age. I went through a spate of having to trash NiCds at about only 3 months old (unlabelled poor quality cells from a reputable(?) supplier) (SANYO, though have always been top drawer in my experience) whereas I have packs of 8-10 year old NiCds that still have full capacity and have performed flawlessly, over that time.
I do find I only get a couple of years out of NiMh packs but this shows up in a drop of capacity whilst cycling every 3 months or so, to check the state they are in.
It's better in my view to replace packs when they show a deteriation in capacity (down to 80%) than judge them by age. Manufactured objects, batteries included, are most likely to fail at the beginning of their life or much later as they age. I went through a spate of having to trash NiCds at about only 3 months old (unlabelled poor quality cells from a reputable(?) supplier) (SANYO, though have always been top drawer in my experience) whereas I have packs of 8-10 year old NiCds that still have full capacity and have performed flawlessly, over that time.
I do find I only get a couple of years out of NiMh packs but this shows up in a drop of capacity whilst cycling every 3 months or so, to check the state they are in.
