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Dec 03, 2001, 01:15 PM
Mitch G's Avatar

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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Dec 03, 2001, 01:33 PM
Registered User
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.
Dec 03, 2001, 02:56 PM
Registered User
Andy W's Avatar
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
Dec 03, 2001, 07:57 PM
Crash Master
Gene Bond's Avatar
Typically, the constant trickle rate is c/20. The c/10 is the 14/16 hour rate.
Dec 03, 2001, 08:04 PM
Mitch G's Avatar
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
Dec 03, 2001, 09:24 PM
Senior Member ??
ETKing's Avatar
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.
Dec 03, 2001, 09:35 PM
Registered User
Andy W's Avatar
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
Dec 04, 2001, 06:51 AM
Tell that to George Zipp!
mikeb33's Avatar
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
Dec 04, 2001, 07:13 AM
Registered User
Andy W's Avatar
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
Dec 04, 2001, 09:20 AM
Registered User
Radek Z's Avatar
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?
Dec 04, 2001, 04:45 PM
Tell that to George Zipp!
mikeb33's Avatar
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
Dec 04, 2001, 05:18 PM
RRD
RRD
Registered User
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
Dec 04, 2001, 06:53 PM
Dieselized User
gkamysz's Avatar
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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