FWIW...my EG4 bank is in open loop with a Morningstar Genstar MPPT100
and an Outback VFX3524.
The Genstar is connected to my battery shunt via the Shunt block and
that gives me SOC capability.
The Genstar has the capability to go closed loop with the EG4 but to be
honest, it's working so well that
at this time, if it ain't broke don't fix it is my thinking. I may try
closed loop at some point though, just to compare.
Anyway, I'm amazed how well the EG4 tracks SOC and within around 1 to
2%, the Genstar agrees with it.
So far so good for a year now.
And FYI, I don't trust ANY DC monitoring system. They all need tweaking
to keep them from lying to us.
Roy Butler
Four Winds Renewable Energy, LLC
8902 Route 46, Arkport, NY 14807
607-324-9747
Education is when you read the fine print; experience is what you get when you
don’t.
“The less people know, the more stubbornly they know it.”
He who asks a question is a fool for a minute. He who does not ask is a fool
for life.
“Progress isn’t made by early risers. It’s made by lazy men trying to find
easier ways
to do something.” -Robert Heinlein
Although no trees were killed in the sending of this message,
a large number of electrons were terribly inconvenienced.
On 8/26/2026 6:16 PM, Jason Szumlanski wrote:
Interesting. I'm pretty sure Sol-Ark does current monitoring to
calculate SOC in open loop based on the aH capacity you enter on the
battery screen. I have quadrupled the capacity and watched the SOC
decline at about 1/4 the expected rate based on the load.
I imagine the Sol-Max AIO does the same. It has an aH field in the
settings that is only used for open loop (lead acid mode).
Even Solar Assistant takes a stab at SoC using programmed aH capacity
and load and charge reported by the inverter.
Jason Szumlanski
Principal Solar Designer | Florida Solar Design Group
NABCEP Certified Solar Professional (PVIP)
Florida State Certified Solar Contractor CVC56956
Florida Certified Electrical Contractor EC13013208
On Wed, Aug 26, 2026, 6:11 PM Zeke Yewdall <[email protected]>
wrote:
Per Jason's comment on Sol-Ark in open loop.
From what I know, none of the AIO's ( at least Sol-ark, EG4 and
Sol-max) do AH counting in-out to determine SOC when operated in
open loop. Even though, as (usually) the only thing in the system
you'd think they could. Instead they use some form of voltage
based algorithm, which in my experience, often leaves much to be
desired. In my SolArk/Fortress system, I had to turn SOC
completely off and only do stuff based on voltage, unfortunately.
It's pretty wild to watch
the discrepancy between a large EG4 rack-mounted bank versus
what a Sol-Ark
15K reports in open loop. I have watched this pretty closely
at a few
sites, and the Sol-Ark seems to be all over the map.
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