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Old Dec 03, 2001, 02:15 PM
Mitch G's Avatar
Naperville, IL USA
Joined Nov 2000
1,886 Posts
Is OK to continue pumping in C/10 charge rate after peak?

Here are some of my understandings with regards to slow charging and the like.

1) C/10 is a safe rate in that you can "overcharge" a pack for a while and not cause damage since the cells don't overheat at this rate.

2) Inconsistencies between cells in a pack can result, over time, in packs not taking full charges because some cells reach a discharged state sooner than others and some cells reach a peaked state sooner than others.

3) It's good to occasionally (monthly?) slow charge your packs to help address item #2 above.

Well, in practice when I use my charger (Dymond Super Smart Charger), to slow charge say a 10xcp2400 pack I use, say, a rate of 300 (since I can't set it for 250). Well, the charger will detect the peak and stop charging after say 8 hours. For example last night a discharged pack completed charging at 2390mAH.

But, I would like to pump up the pack a bit more and get some better balance between cells as per my understandings listed above.
So, I'm thinking I should be able to just start another slow charge on the pack. It'll either repeak after pumping in a few hundred mA, or I'll stop it at some point.

Does this seem like it would be OK?
What are the limits to which I can take this approach?

A corollary to this approach would be to fast charge the pack, let it cool down completely and them pump in a few hundred more mA at a C/10 type of rate.

Any input is welcome.

Thanks,


Mitch
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Old Dec 03, 2001, 02:33 PM
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CA and NH
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Mitch at C/10 rate, it is still not safe to leave it on for a long period of time.

As for the peak charging, it is best if you charge it at Capacity. Charging at capacity allow the battery charger to detect peak more easily.
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Old Dec 03, 2001, 03:56 PM
RIP Ric
Andy W's Avatar
Marietta, GA
Joined Jun 1999
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I have done this, but I don't make a habit of it. Peak charge @ C, then C/10 for another 4 hours or so.
..a
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Old Dec 03, 2001, 08:57 PM
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Gene Bond's Avatar
Indianapolis, IN
Joined Sep 2001
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Typically, the constant trickle rate is c/20. The c/10 is the 14/16 hour rate.
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Old Dec 03, 2001, 09:04 PM
Mitch G's Avatar
Naperville, IL USA
Joined Nov 2000
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I probably oversimplified a bit, but part of my premise is that if C/10 can be used for about 50% longer than necessary, then I should be able to do a C/10 charge for about 4 hours after the peak is reached - ala Andy's response.

But, Andy's response makes me wonder about things a bit. Why not make a habit of it? What's the downside?



Mitch
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Old Dec 03, 2001, 10:24 PM
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ETKing's Avatar
Southern California, USA
Joined Sep 2001
388 Posts
I listened to this:

http://www.srbatteries.com/techsupt/techsupt.htm

Larry makes a point for slow charging. In my own words (since I don't remember exactly what he said):

1. Slow charging is not as hard on packs as fast charging.
2. Slow charging balances the cells.
3. After the last flight of the day, you are not in a hurry.
4. Always leave your packs discharged after the last flight (on that pack), and slow charge it when you get home.
5. Peak charge at the field, and before flying a slow charged pack.


The audio program is interesting. Give it a try.
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Old Dec 03, 2001, 10:35 PM
RIP Ric
Andy W's Avatar
Marietta, GA
Joined Jun 1999
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Slow charging also seems to 'condition' the cells, as well as balance them. Sort of like breathing a little bit of life into them. I've had zero cell problems (except for one case of black wire disease) since adopting Larry's advice..
..a
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Old Dec 04, 2001, 07:51 AM
Tell that to George Zipp!
mikeb33's Avatar
United States, IL, Inverness
Joined Oct 2000
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Last week I set my Hirec 335 to charge a Cp1300SCR pack through my wattmeter at 1.3A. I forgot about it for a few days and when I looked at it, the wattmeter said almost 3000ma had passed through it. Was that bad?

MIKE
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Old Dec 04, 2001, 08:13 AM
RIP Ric
Andy W's Avatar
Marietta, GA
Joined Jun 1999
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At 1.3A, the 335 should have kicked off (temrinated the charge) at a little above capacity. The 3000mA may be a result of the little trickle 'spikes' it keeps putting out when charge is completed.. It may be OK..
..a
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Old Dec 04, 2001, 10:20 AM
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Radek Z's Avatar
Pampigny, Switzerland
Joined Oct 2001
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Checking the link provided above I have found the list of the "Techiques Publications" SR Batteries offers. Looks very interesting - the question is: How good is it? Is it worh the $3 per volume?
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Old Dec 04, 2001, 05:45 PM
Tell that to George Zipp!
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I did another one and after it "kicked off", there continued to a 1 or 2 watt charge. A mere trickle and I assume it's ok. It must happen all the time, but I don't usually have the Wattmeter on it.

Thanks

MIKE
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Old Dec 04, 2001, 06:18 PM
RRD
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United States, NC, Asheville
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Mitch,

I think your Dymond Super Smart Charger trickles after a manual fast charge. 1/20th of the set charge rate I believe. So if you just leave your packs on the charger for a while after they peak at the normal charge rate (say somewhere between C and 2C), the charger should accomplish this for you automatically. Same slow charge style as Andy.

Bob
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Old Dec 04, 2001, 07:53 PM
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Chicagoland
Joined Feb 2000
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Two things kill batteries: overcharge and heat. You can avoid both. I would suggest overcharging by no more than 10% for NiCd. NiMH appear to be much more succeptible to damage from overcharge.

I have a hard time believing cells can get too far out of balance. After leaving cells in my digital camera for months on end, each cell peak charged within .001% capacity input of each other. I've done this and noted it more than a few times.

Greg
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