Re: Building my own equilizer

[Lee Hart <leeahart@earthlink.net>]

Victor Tikhonov wrote:
> 
> I have powerchecks in ACRX. They do work, no one debates that.
> Debate is how well and whether worth the price.
> 
> After I installed them for the first time (4 month after I got my
> well balanced hand picked 28 Optimas), they started blinking away
> quite vigorously, but this activity ended in about a week. On the
> rested pack they are like all off - no blinks meaning there is
> <60 mV between adjacent batteries.
> 
> The only time ALL of them blink, is when the pack voltage reach
> about 405V (14.46V per battery).
> 
> What I like about powerchecks compare to Rudman regs (at least
> current ones) - the powercheqs work on partially discharged pack.
> If you drive for half hour and don't want to recharge today, the
> voltages are near 12.3V per battery. Powerchecks will keep balancing
> regardless, as long as delta is 60mV, regs won't until some voltage
> level is reached; i.e. they are useless for partially discharged
> and sitting there pack.
> 
> What I dislike about powercheqs - each next battery can be 58mV
> lower than the previous one (means if the first one is 11.9V,
> the last is 13.52 and the powerchecks think everithing is OK.
> They don't compate first to last or best to worst batteries,
> only adjacent ones. To be fair, 1.62V first to last battery
> voltage difference for the string of 28, may not be such a big deal.
> 
> I talked to the designer of the cheq for about half hour.
> They could easily make delta 30mV or 5mV if they wanted to.
> This would mean too much DC-DC-ing without real benefit,
> so they *chose* 60 mV for their reasons, right or wrong.
> 
> Regarding max current and alg - they DON'T reduce the
> current from rated 2A to 0A linearly when delta goes
> from 120mV to 60mV, they have some patented alg which is
> time dependent, some sort of dV/dt thing. He didn't tell me
> details on that (I hate that), but it boils down to the
> fact that the current they transfer depends on how fast batteries
> get equalized, not only absolute delta. If delta is 80 mV,
> initially it may be 0.9A. In 20 min it will be 1.3A, they are
> trying harder. If in 1 hour delta is still 80 mV, they give up
> and the red light comes on, they don't sit forever doing 1.3A.
> (I came up with the numbers to illustrate what I've been told).
> 
> BTW, they have 5A version commertially available, just 2A is
> by far the most popular for their intended market - stand-by
> backup batteries balancing. Those batts do nothing 99% of
> the time and don't need more than 2A.

Ah, then they are playing with their algorithms. That's good. They are
learning that it isn't as simple as just holding the batteries at the
same voltages.

The first version they offered appeared to be just a DC/DC converter
controlled by a comparator; no micro. As time passed, it got smarter at
each show, as they learned and tinkered. There were smarter on/off
limits, then timers, and other fault detection. I suspect the sudden
price increase came when they decided to put a micro in each one.

Victor, how hard would it be to put your Emeter on one of your
Powercheqs and watch what it actually does?
--
Lee A. Hart                Ring the bells that still can ring
814 8th Ave. N.            Forget your perfect offering
Sartell, MN 56377 USA      There is a crack in everything
leeahart_at_earthlink.net  That's how the light gets in - Leonard Cohen