Tri-Metric program question [RE-wrenches]

[Todd Cory, Mt. Shasta Energy Services]

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When a battery based grid tie system has the grid operating, the meter 
is not necessary. When the grid goes down is when the customer needs the 
meter and it is then that it is important for the meter to read 
accurately, starting with a 100% charged reading.

Grid tie inverters with batteries constantly send small charge and 
discharge currents into the batteries. Because batteries are not 100% 
efficient, amp hour meters treat charge currents and discharge currents 
differently. It takes more charge current to compensate for a given 
amount of discharge current. This is why amp hour meters on battery 
based systems tend to accrue a discharged SOC inaccuracy.

The only way I have found to resolve this issue, so when the grid goes 
down the meter starts at 100% is by setting the float/sell voltage 
slightly higher so the batteries constantly get way more charge then 
discharge currents. Another thing which helps is to cycle the batteries 
a few times so the amp hour (link-10) meter recalculates the battery 
efficiency higher from the default of 90%.

I still hope for the holy grail for any battery based system (on or off 
grid) namely a charge controller with built in amp hour meter, or at 
least one that will "talk" to a meter so both devices stay in sync with 
each other. Wireless would be great too!

Todd
P.S. Ray, why do you call the MATE "accursed"?

Ray Walters wrote:

>
> Hi Allan;
>
> We've had the same problems. The Trimetric doesn't even read anything 
> most of the time due to the shunt location. Solar just passes straight 
> thru to the inverter in grid tie operation. A Pentametric can be set 
> up with additional shunts on the inverter and solar input, but you're 
> back to the same trouble with the charged parameters. What we need is 
> meter that has different charged parameters based on the status of the 
> system: grid tie  or off grid.
> Also, while we're dreaming, a meter that could handle both AC and DC 
> inputs, and......drum roll please.... wireless.....!   I talked to 
> Ralph about this too, but like all of us currently, he's already 
> tapped out keeping his current line up running flawlessly (Great Job 
> Ralph) While I'm at it, I have to give a shameless plug for his  easy 
> to program Windows interface for the Pentametric too. If only the big 
> boys at Outback had such a thing instead of the accursed MATE.
>
> Ray 


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