Quote:
Originally Posted by superfan86
I have the same setup. I also have a 12v inverter and Alltrax controller wired to my power switch. EZGO TXT cart.
My meter reflects a 3-5 watt draw all the time, which I assume is the power required to power the unit itself (it is always on).
I reference the resting voltage against the displayed calculated SOC % each day and have found that it seems to be consistently accurate, certainly well under the 5% weekly variance loss posted above.
Unless you have the sealed charger from BigBattery, you have no way of knowing when the charge ends as the 15 amp charger fan runs constantly. Just be aware that is a "feature"...
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Not implying that whatever battery / BMS you are using has appreciable loss as I mentioned when powered "on", but voltage is an exceedingly difficult way to reflect SOC with these batteries since the discharge / voltage curve is so flat, which is why the shunt-based coulomb counting meters are much more precise.
I don't have a "Big Battery" battery, nor their charger, but it's clear to see on the Renogy meter biterope has when any charger shuts off (if you can't tell otherwise) as the charge amp-rate reaches zero.