Measuring batt.capacity charging or discharging  
View related threads: (in this forum | in all forums)

Tower Hobbies
Enter up to 4 keywords or Tower stock numbers
Logged in as Guest



Users viewing this topic: none
  Printable Version
       


Tilt-A-Whirl Helicopter Workstand
Seller:  Prontow
Details:   $175.00   |  10/9/2008   |  Classified Ad
We will rotate YOUR AD in this spot if you select "Forum Featured" when placing or editing your ad!

All Forums >> Radios, Batteries, Clubhouse and more >> Batteries & Chargers >> Measuring batt.capacity charging or discharging
Page: [1]

Login
Message << Older Topic   Newer Topic >>
Measuring batt.capacity charging or discharging - 5/24/2002 3:36:16 PM   
blueskies-RCU


 

Posts: 52
Joined: 4/8/2002
From: Md.
Status: offline 		It's my understanding that chargers and dischargers can both measure batt. capacity. It seems that more accuracy could be had by measuring the amount of energy in a cell while discharging - as it dumps what it has. Does it matter one way or the other.
       Post #: 1

Measuring batt.capacity charging or discharging - 5/24/2002 3:46:51 PM   
Jazzy



Posts: 1106
Joined: 1/8/2002
From: Erie, PA, USA
Status: offline 		Since the charging process is not 100% efficient there is some loss during charge. It is not uncommon for a battery to require 5-20% more mA input than it will discharge. (At least that is what my Supernova is telling me .)

_____________________________

Aww $#!^.... I left the )@#& transmitter at home!

(in reply to blueskies-RCU)
       Post #: 2

Measuring batt.capacity charging or discharging - 5/24/2002 4:49:22 PM   
blueskies-RCU


 

Posts: 52
Joined: 4/8/2002
From: Md.
Status: offline 		So why would a charger manufacture even bother to enable a charging measurement that's not accurate. There seems to be many issues with chargers in general.

(in reply to blueskies-RCU)
       Post #: 3

Measuring batt.capacity charging or discharging - 5/24/2002 6:10:14 PM   
Jazzy



Posts: 1106
Joined: 1/8/2002
From: Erie, PA, USA
Status: offline 		OK. Take a Zip-lock baggie and poke a couple pinholes in it. Slowly pour in water-very slowly-from a container that has measuring graduation marks on it. When you manage to get it full, wait a few minutes, then carefully dump it back into the container.
Didn't get out of it quite what you put in it huh.?
(It is a poor example but you get the idea.)

The mA input the charger is displaying can be used for comparison purposes for future cycles relating to the battery's charging efficiency. Over time, if the battery requires more and more mA input to reach full charge and/or it's discharge capacity is decreasing, the pack probably has one or more 'leaky' cells.

_____________________________

Aww $#!^.... I left the )@#& transmitter at home!

(in reply to blueskies-RCU)
       Post #: 4

Measuring batt.capacity charging or discharging - 5/25/2002 3:05:52 PM   
Steve Lewin


 

Posts: 904
Joined: 3/18/2002
From: Reading, UNITED KINGDOM
Status: offline 		Think about it for a second. The disadvantage of measuring only on discharge is that it only tells you what used to be in the battery. It's stone empty now. No use to anyone.

Most people are more interested in what they've got in the battery now, hence the charger gives you an idea of this. Seems reasonable to me.

Steve

(in reply to blueskies-RCU)
       Post #: 5

Measuring batt.capacity charging or discharging - 5/26/2002 8:08:34 AM   
blueskies-RCU


 

Posts: 52
Joined: 4/8/2002
From: Md.
Status: offline 		The charging operation is not 100% efficient (I wish I knew what that percentage was) and combined with various amount of peak over charging and under charging you end up with a number. I guess if those operations are consistent and repeatable you can know battery pack condition. With that in mind you'd have to stick with the same charger. I think dumping energy from a battery can be accurately measured but was interested in knowing the difference between that measurement and the charging measurement for batt. capacity.

Mike

(in reply to blueskies-RCU)
       Post #: 6

Measuring batt.capacity charging or discharging - 5/26/2002 2:12:01 PM   
Steve Lewin


 

Posts: 904
Joined: 3/18/2002
From: Reading, UNITED KINGDOM
Status: offline 		Indeed Mike, it depends what the purpose of the measurement is. To check overall battery condition you need a series of measurements over time in order to tell if the battery is going off. Measurement on discharge is best for this. You can overcharge until you are certain no more will go in and then measure how much comes out.

However that's not the purpose of the metering on chargers, that is mainly to give you confidence that a reasonable amount has gone in e.g. it's not had a false peak and given up early. Many good chargers don't have capacity displays and they're not necessarily the worse for that. Many of the ones that do have displays also discharge so they needed the display for that. While it's there you might as well put some numbers on it.

As for the percentage overcharge, good luck working that out. Don't forget you usually don't accurately know the initial amount of charge left in the battery and then the required overcharge varies at least with the charging current and the ambient temperature.

This battery stuff is almost as much Art as it is Science.

Steve

(in reply to blueskies-RCU)
       Post #: 7

Measuring batt.capacity charging or discharging - 5/26/2002 4:39:21 PM   
Jazzy



Posts: 1106
Joined: 1/8/2002
From: Erie, PA, USA
Status: offline 		Mike, given what we can safely assume, (I hate that word), a previously 'prime-charged' pack will require between 105 and 125% more than rated capacity to become fully charged from a completely discharged state, (0.9V/cell).
Using my analogy in a previous post above, one can conclude that the faster you pour in water the faster the battery will become charged. I.E. not quite as much loss during the charging process. (The difference is not much at all.) However, when using the C/10 or lower charge rates, the battery will be much less susceptible to damage, (overflowing-overcharging), and may be left on charge for much longer periods of time.

After several cycles a battery will start to take on it's own characteristics. It's discharge capacity as well as the input required to reach a fully charged state from a discharged state should be consistent.

I'm currently testing about 30 Dewalt 12V cordless drill packs. The newer packs are requiring around 1850 mA input and discharging around1700 mAH with a fully charged voltage of around 14V. Some of the older and heavily used packs are requiring up to 2100 mA input but only discharging similar to the newer packs and having a fully charged voltage of around 12.5V.
From this information I can conclude the older packs are either reaching the end of their service life or have a cell or two that are leaking faster than the others. After sitting a day or two the suspect packs will be discharged again to see how fast the degradation in capacity is occurring. From there I will make a determination based on my findings whether to recycle the whole pack or disassemble and salvage the good cells.

The 'input' information can be used for keeping detailed cycling data or for comparison purposes. It is up to the user whether the info is used or not.

As Steve mentioned above, when you see that a discharged 1600 mAH pack only required 875 mA input to reach peak, there was a false peak that the charger could not ignore and it must be charged further. Such a pack may require further cycling/priming to equalize the cells or disassembly to find the errant cells.

Good Luck,
Jeff

_____________________________

Aww $#!^.... I left the )@#& transmitter at home!

(in reply to blueskies-RCU)
       Post #: 8

Measuring batt.capacity charging or discharging - 5/26/2002 5:44:42 PM   
blueskies-RCU


 

Posts: 52
Joined: 4/8/2002
From: Md.
Status: offline 		Thanks Steve and Jeff......very good stuff. I'm on my way to a Super Turbo I think, but am only just beginning to understand the big picture. Have 3 TX's and 3 flight packs and only use wall warts and will soon try NiMH. Don't quite know what I'm supposed to be aware of for shopping for chargers. Keep hearing "Super Turbo" or "Super Nova" but will have 5 to 6 batt. packs. Are you to use these sophisticated chargers every month or so to evaluate your packs ( I do understand NiMH require peak chargers though) and use wall warts in the mean time? Could I just use a "Super Test" and wall warts (no NiMH)?

Concerning false peaks.......Is that from a bad cell........and if so why would you continue charging? If a track record has been established for a pack that has one false peak, can cycling bring it back to normal.

Thanks,
Mike

(in reply to blueskies-RCU)
       Post #: 9

Measuring batt.capacity charging or discharging - 5/27/2002 6:43:53 PM   
Jazzy



Posts: 1106
Joined: 1/8/2002
From: Erie, PA, USA
Status: offline 		Mike, glad to be of some help.
Cycling is up to the user. Some do it once a year while others do it more often. I do it every three months and keep records.

After flying, boating, or driving I peak the packs used and use the timer/wall wart method described in Red's Battery Clinic to maintain a fully charged state.
The cells that exhibited false peaks were cheap NiMHs that I bought at "a store." They are AAA 550mAH and only are used in my two-way radios. Cycling has brought them around-somewhat.
Because of their use I don't worry about them.
When looking for a charger/cycler look for versatility. The ability to cover all your current needs while allowing for future needs are qualities I looked for.
The SuperTest and wall warts would be fine until you get what you want.
I would recommend either the SuperNova or the SuperTurbo. Opinions vary.

_____________________________

Aww $#!^.... I left the )@#& transmitter at home!

(in reply to blueskies-RCU)
       Post #: 10

Page:   [1]
All Forums >> Radios, Batteries, Clubhouse and more >> Batteries & Chargers >> Measuring batt.capacity charging or discharging
Page: [1]





Jump to:


Google 



Search | Marketplace | Event Calendar | Local Clubs | Magazine | Product Ratings | New Products | Discussion Forums

Photo Gallery | Member Video Posts | RCU Video Gallery | Instructor Search | Field|Track|Marina Search

Advertisers | Hobby Vendor Resources | Rate Manufacturers | Sign In/Sign Up