Re: ICS-200 output current limit

[Lee Hart <leeahart@earthlink.net>]

William Korthof wrote:
> ICS-200 charge station... set to 32 amps for virtually all sites
> current over 32 amps) must continue for 1 minute...
> Does the Zivan exceed 32 amps line current? If so, is there a way to
> limit the line current draw?

Do you happen to know if the 32 amp rating is rms, average, or peak
current? Rms would be the best choice, but is the most expensive to
implement.

Bruce Parmenter wrote:
> I know that when I plug in both of my K2s, my charging current into
> my pack is 31 amps maximum... on a 132V pack.

When your bulk charging stage (0-80% state of charge) is at constant
current, peak power occurs just before the charger switches to the
constant voltage stage (at ~80% SOC). That will happen around 2.4v per
cell; 14.4v for a 12v battery, and 158v for a 132v pack.

Notice that the AC line current *rises* as the charge cycle progresses.
31 amps at 132v (0% SOC) is 4092 watts; 31a at 158v (80% SOC) is 4898w.
You can't set the AC line current at the beginning of charge and assume
it will be OK throughout charging with a regulated charger.

Zivan chargers are not power factor corrected. The data sheet says
efficiency is about 85%, but is carefully mute on peak or rms AC input
current for a given output. Lacking specs and actual measurements, we
have to guess. At 85% efficiency, 4092w out / 0.85 = 5762w input. At 0.7
power factor (a best-case number), 5762w / 0.7 = 8232va. At 240vac,
input current would therefore be 8232va / 240v = 34.3 amps rms.

Also note that on a regulated charger, AC line current goes UP if AC
line voltage goes down. That's because the charger is regulating the
output power, so you need more current at lower voltage to maintain
regulation. If the line voltage was 10% low = 216vac, line current goes
up 10% to 34.3a / 0.9 = 38.1 amps.

You can't set the AC input current directly with the Zivans, but you can
set the output current. So, you can indirectly limit AC input current by
setting the output current. Since there are lots of parameters you don't
know (like actual efficiency, actual power factor, and actual AC line
voltage), your best bet is to put a true-rms ammeter in the AC input,
and set it to 32 amps or less by turning down the charging current when
the battery pack is at 158v.
-- 
Lee A. Hart                     Ring the bells that you can ring
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leeahart@earthlink.net                  Leonard Cohen