Hi David, I typed "pfc restart" into gmail and amazingly it came up with
the post I was thinking of, from 2005. I hope Bill doesn't mind me
reposting it. There was a very long discussion leading on from this too.
[..]
Rich will likely disagree, but there is a subtle, but very serious design
flaw in the PFC-20 charger.
>> The problem <<<
The finish charge timer resets if the pack voltage drops.
>>> Why this is bad <<<
If your batteries go into thermal runaway at the end of the charge
cycle, during the timed constant voltage stage, the timer resets and the
charger keeps humping in amps forever. After a few hours of this, your
battery pack will be ruined. Since this is the part of the charge cycle
where the most heat is generated, this is the part of the cycle that the
batteries are most likely to go into thermal runaway and when the voltage
will most likely drop.
Rich doesn't see this as a problem, but it just happened to my
$10,000 NiCad battery pack. I see it as a problem that should be corrected,
needless to say. My pack may not not totally ruined, but has lost about 25%
capacity. I will see how it behaves in the next few days. Maybe they will
perk up a bit, but that is unlikely. Perhaps it will die completely. We
shall see.
>>>>> The Fix <<<<<<
The "work around" patch for this inherent design flaw is to install
a timer in series with the input power cord. You set the timer for the
maximum hours that you think it will take to charge the pack. If the
charger doesn't shut down, the timer will limit the damage to your pack. I
just installed one of these. A bit late, but it may prevent further damage
to my expensive battery pack.
>>> What other chargers do <<<
The Zivan line of chargers does not have this design flaw. When the
pack voltage reaches the trigger point, (and stays at or above the trigger
voltage for 30 seconds or so) the finish charge timer locks in. No matter
what the voltage does after that point, the charger will shut off at the
end of the finish period you have programmed in. This is the correct way
for the finish timer to work.
There is also a timer for the total charge time. This timer is set
so that the charger cannot stay on longer than it would take to supply just
over 100% of the capacity of the pack. A ten amp charger connected to a 100
a-hr pack would have this timer set for 11 hrs, for example. This is what
my new in-line timer does.
>>> What I plan to do <<<
In the next week or so, (if my pack doesn't die completely,) I plan
to build a micro-processor control for my PFC-20. It will read the E-meter
and control the operation of the PFC-20 via the Reg-Bus port (or perhaps I
may go inside.) This will be a pain in the butt to do, but I don't see much
alternative.
Bill Dube'
[..]
On Thu, Apr 3, 2014 at 11:57 AM, EVDL Administrator <evp...@drmm.net> wrote:
> On 2 Apr 2014 at 15:10, Evan Tuer wrote:
>
> > I have heard of one Saft pack being cooked. IIRC it was a Manzanita PFC
> > charger, something to do with it restarting as the voltage dropped, then
> > thermal runwaway at bulk charge current.
>
> The one case I know of involved an unregulated bad boy charger left on the
> pack unattended and forgotten.
>
> It's always a good idea to have some kind of upper bounds sanity check
> built
> into your charger controller. For example, if your battery is 250 amp
> hours
> and the charger has delivered 500 amp hours, stop charging and set an error
> condition, even if no other charging algorithm rules have been fulfilled.
>
> David Roden - Akron, Ohio, USA
> EVDL Administrator
>
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