[NSRCA-discussion] Big LiPo pack charging

[Robert Mairs]

Everyone will prob disagree, but I like the approach Kokam is trying to 
develope.  Larger cells that can be run in a 1P configuration, where each 
cell can be monitored, not a group of parallel cells, for voltage during 
charge as well as voltage during discharge.  Hopefully the weight and 
performance of the cells will be within our limits.  With such a simple pack 
configuration, I could envision even being able to replace a faulty cell, 
instead of having to forfeit the entire pack.  I hope they succeed.



----- Original Message ----- 
From: "Dean Pappas" <d.pappas at kodeos.com>
To: <chad at f3acanada.org>; "NSRCA Mailing List" 
<nsrca-discussion at lists.nsrca.org>
Sent: Tuesday, March 07, 2006 10:59 AM
Subject: Re: [NSRCA-discussion] Big LiPo pack charging


> Hi All,
> I hear discussions about this charger versus that, and while I am not 
> going to try and sell my preference, I think I
> should tell you what a proper charger, for our purposes, should do.
>
> I really think the important thing to remember, here, is that a real 
> balancing charger will always be better than a charger plus an add-on 
> balancer.
> Why? The add on balancer and charger combo will do its job, perfectly 
> well: until there is a problem with a battery pack.
> Unfortunately, this is where the safety hazard happens (not to mention the 
> premature aging of expensive battery cells).
>
> When there is a problem, and the imbalance between cells is not slight, or 
> some cells have appreciably different capacities than others due to age,
> the controlled bypass current around the higher voltage cells may not be 
> high enough to keep things balanced.
> That's how balancers work, they put a current "leak" across the higher 
> voltage cells;
> during charging this leak shunts some of the charging current around the 
> higher voltage cells, until the lower voltage cells catch-up.
>
> For things to really work properly, the balancer part of the works needs 
> to be able to throttle-back the charger current,
> to something equal to or less than the maximum leak current, at any stage 
> of the charge, if the imbalance isn't getting better.
> That really requires a one-piece balancing charger, or some sort of fancy 
> communication between the charger and balancer.
>
> Right now, very few companies make a real balancing charger, but this 
> can't stay the same for long.
> It has also been suggested that with a true balancing charger, that never 
> charges too fast to maintain balance,
> that 2C and 3C charges are possible, with the high C discharge packs we 
> find necessary, in Pattern.
>
> later, friends,
>
>
> Dean Pappas
> Sr. Design Engineer
> Kodeos Communications
> 111 Corporate Blvd.
> South Plainfield, N.J. 07080
> (908) 222-7817 phone
> (908) 222-2392 fax
> d.pappas at kodeos.com
>
>
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