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Old Nov 14, 2003, 08:34 PM
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Ben74's Avatar
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i see. thanks for the update, glen.
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Old Nov 15, 2003, 06:12 AM
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"... there would be no more adding new cells to old packs and what this would mean to me is that I could not send in a 4S4P for 'factory refurbishment' to restore it to the same functionality IF a cell was ruined..."

If you parallel charge, you don't need to discard a "pack" if one cell gets ruined. Just put a new cell in. Pack "balancing" is only an issue if you charge cells in series.

- RD
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Old Nov 15, 2003, 10:57 AM
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HI RD,

Perhaps things wil evolve that way, but can one do that with current "installed base", especially if the manufacturer will not repair them?

The original comments I heard, "these things are pretty durable, but if you do damage them in a crash you can send one in to Charlie for repair" has changed into a situation where one has to find a home for the orphans after paying a minor charge for the refurbishing. So for me, the concept of these cells being an investment that could be maintained in service for a long time is in question. With increased popularity, the market for "lesser packs" from the popular configurations would quickly flood and salvage prices drop. Your idea of parallel charging seems to be a good way to get long term service and return on the investment.

...and things won't stop evolving.....

Cheers!

Glen
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Old Nov 15, 2003, 02:30 PM
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Hi, Glen,

Re the "installed base": I'm afraid we'll have to take our packs apart and rewire them. That's what's happening, in effect, to Charlie now.

I'm still using my Kokam 3270 Lipos I bought about a year ago, when they first came out.

Ever since the beginning, I have followed the strategy of buying and individually or parallel charging large enough LiPos that I didn't need to connect any in parallel for flying. They have been connected in series only for flying.

These original cells are still serving me well. I check the residual voltages from time to time, after flying. These voltages now vary by over .5 volts in some cases, which indicates the cells are now mismatched and some would be ruined (at least) if they were charged in series.

When Kokam's new 20C, 3.4 amp cells come online, larger emodels can easily adopt this strategy.

- RD
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Old Nov 15, 2003, 04:55 PM
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Quote:
Originally posted by RD Blakeslee
If you parallel charge, you don't need to discard a "pack" if one cell gets ruined. Just put a new cell in.
The cells deteriorate with use and the new cell will effectively be a higher capacity cell as well. Its generally risky to make packs up of unequal cells regardless of the charging method.

I think Thunder Power's approach of reducing the total cell count is the best, though sending a damaged pack through the mail gives me the frights.

Rick.
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Old Nov 15, 2003, 05:24 PM
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"The cells deteriorate with use and the new cell will effectively be a higher capacity cell as well. Its generally risky to make packs up of unequal cells regardless of the charging method."

Why risky?

If the cells are individually charged to 4.2 V or so, the worst that can happen (and does, with my cells) is that the lower capacity cells will discharge to a lower voltage than the higher ones. Where's the harm in that? I haven't had any problems with it, and I've done it over and over, for a long time.

- RD
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