Hi Allan,
I seem to remember that if you hook the breakers up backward they will
trip more easily.
Be curious to try hooking them up the other way and see if that matters.
jay
peltz power
On Dec 17, 2008, at 11:55 AM, Allan Sindelar wrote:
Wrenches,
I am doing a series of corrective equalizations and load tests on a
set of Surrette S460 batteries. I'm using an old Trace DR1524 mod-
square inverter as a charging source from in-shop grid AC power. I
am also using the inverter to power mostly-resistive AC loads: an
electric space heater on low with fan, an incandescent bulb and a CF
bulb - the combination being used to achieve a C/20 discharge rate
for load testing. DC metering is handled by a Tri-Metric meter with
100A (low) shunt; AC by a Kill-a-Watt AC monitor. The inverter is
rated to charge DC at 35A maximum, and consistently charges at
around 32A measured. 35A is a C/20 rate (5A per 100A of rated
capacity for corrective equalization) for these 350 ahr batteries in
two parallel strings.
When I set up this station I used a CBI (Outback-Midnite) DC panel-
mount 50A breaker on the battery cables. The cables are 2/0 or 4/0,
being what was around the shop. The problem is that the breaker
tripped while charging. Thinking it might be a defective breaker, I
replaced it with a 60A; same. It's not a surge load, as it doesn't
trip on startup, but 10-30 minutes later. I understand that these
are magnetic-hydraulic breakers, not thermal, so I don't understand
why they are tripping. My hunch is there's a DC ripple that's
messing with the breaker's response curve. Since inverters are
generally installed with heavy cables and matching big breakers or
fuses, this never shows up in normal operation. But in this
application there's no surge capacity to accommodate, so I just
sized the breaker to the load plus reserve: 35A max/50 or 60A
breaker. And the OBDC/CBI breakers are rated for 100% duty cycle.
Any ideas?
Thanks,
Allan
Allan Sindelar
allan_(at)_positiveenergysolar.com
NABCEP certified solar PV installer
Positive Energy, Inc.
3225A Richards Lane
Santa Fe NM 87507
505 424-1112
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