Custom SOC/SOH Battery Test?

Jan 11, 2014
11,323
Sabre 362 113 Fair Haven, NY
This article just appeared in the Dogwatch, the online newsletter associated with Good Old Boat magazine.

https://audioseastories.com/fs-may19/

I am curious about the approach and limitations. There is no mention of the temperature, how the voltmeter was connected, or what voltmeter was used. Additionally, the accompanying chart is from Trojan, yet the batteries are Ray-O-Vacs, which may or may not reflect the Ray-O-Vacs actual voltage profile.

The traditional advice has always been to develop an energy budget and use that to estimate daily amphour needs. Then use a standardized 20 hour test to determine the batteries capacity. The math is then simple, compare the needs to the capacity.

I can see where conducting a "real life" test on a boat may be easier than hauling the batteries home to run the standardized test.

Wouldn't it be easier to just install a Balmar SG or the new Smart Gauge?
 
May 17, 2004
5,032
Beneteau Oceanis 37 Havre de Grace
I don't know, I'd like to know more about their loads before passing judgement. The fact that they have a 20W solar charge could be confusing their math in a few ways. For one thing they say "with a trickle of charging power coming during daylight hours from our 20W solar panel, the house bank voltage measured 12.31 volts, approximately 66 percent of full charge". So does that mean 12.31 is the voltage while being charged? If so that's not an open circuit voltage, so their use of the chart to say they're at 66% SOC wouldn't be right. Also, if their loads are very low (say close to the 1 amp the charger puts in) they could run almost perpetually at the same voltage levels, so their assumption that the SOC 24 hours later isn't necessarily valid.

I guess at the end of the day it tells them wat they want to know - Can we run for as long as we need to without killing the batteries - but for myself I'll just keep lugging my batteries home for a full 20 hour test every couple years, to know what's really going on.
 
Feb 6, 1998
11,667
Canadian Sailcraft 36T Casco Bay, ME
Wow.... Articles like that are one of the reasons I've stopped getting GOB.
 
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