[NSRCA-discussion] Big LiPo pack charging

[Stuart Chale]

Dean, do you have an available product in mind?  One that is priced close to
the available charger/balancer combinations?

Stu

-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Dean Pappas
Sent: Tuesday, March 07, 2006 10:59 AM
To: chad at f3acanada.org; NSRCA Mailing List
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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