E-meters [RE-wrenches]

[Steve Bell]

Hi Everybody,

Here are a thought about E-meters loosing amp-hours especially with
grid-tied systems. Typically, when a system is grid-tied, the batteries are
held at float voltage for extended periods of time, without any significant
(greater than 10% DOD) cycling. This can cause the amp-hour reading to drift
(loss AHs). The E-meter only "re-zeros" the AH counter after a discharge of
more than 10% DOD.  Also, remember the batteries are self-discharging and
continually being recharged while grid-tied. The e-meter shunt measures the
AHs going into the batteries but can not measure the AHs lost due to
self-discharge. So, the AH reading drifts.

For my home system with is both grid-tied and has a large AH battery bank, I
find that I need to disconnect from the grid and turn off some or all of my
PV array to cycle my batteries more than 10%. When I do the E-meter AH's
comes back on track.

Although I have no personal experience with the other brands of AH meters, I
would assume that they would act similarly. What do you think?

Sincerely,

Steve Bell
SunWize Technologies
Stelle Office
sebpv at stelle.net




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