Meters / gages for solar

[sbrenton]

Hello Group-
I have been reading about using solar panels and batteries in a RV and I routinely see the warning  "...don't let your batteries fall below ___%".

What meters or gages do I need?

I doubt there is a percent meter so what's the relationship between % and ____ parameter? (Whatever parameter I need to watch.)

The kit I bought from Renogy has no display at all.

Thanks in advance
Stephen

 

[John61CT]

Yes, % meter, AKA SoC battery monitor.

Balmar/Merlin SmartGauge most user-friendly and accurate overall.

Bogart Trimetric and Victron BMV-702 good examples of the more common shunt-based AH-counting type.

Search here http://www.pbase.com/mainecruising/boat_projects

for "battery monitor"

 

[John61CT]

BTW not specifically solar, these account for all charge sources, alt, shore charging, genny etc

 

[jonyjoe303]

I use these on my lithiums, but they can be set to 12 volt lead acid. They are lighted LCD and cost is less than 5 dollars,  they sell on ebay. Also you can just read the voltage, if the battery reads 12.1 volts, your at 50 percent.


[font='Helvetica neue', Helvetica, Verdana, sans-serif]DC 12v lead acid battery indicator batteries Capacity Tester Digital LCD meter[/font]


on my battery pack

 

[John61CT]

Voltage gives a **very** approximate indication of SoC, not even close to accurate enough IMO for even lead chemistries when actively cycling, especially with high currents involved.

And LFP has such a flat volts/SoC curve above is triply true.

But for many "good enough" is in the eye of the beholder, and we all eventually (think we) develop a good instinct for our own system and unique usage patterns.

 

[deadwood]

I use the Trimetric and have been very happy with it. Not only does it give me my SOC at a glance I can also easily see how many AH's are coming in or going out. I just installed a couple of lights in my ceiling and I can see when I turn them on that my AH's used jumps up by almost 1 AH. So it's helpful in that respect as well.

 

[Spaceman Spiff]

 . . . What meters or gages do I need?

I doubt there is a percent meter so what's the relationship between % and ____ parameter? (Whatever parameter I need to watch.)

Yes there are battery monitors that tell you in % how full your battery is.
I have a Trimetric 2030.  It will tell me my battery capacity in percent.  It needs to be periodically calibrated (because batteries change as they age) and I do that by measuring specific gravity.

Among the many pieces of information it gives me, the 2 that I monitor are net amps (in minus out) and percent full.  By monitoring amps I learned how many amps different devices use in a day, good for planning when going with poor sun for a few days.  By monitoring amps in I learned how much charging I can expect from a sunny, cloudy, or dark and gloomy day.  % full tells me how much battery I have left.

IMO if you are new to solar battery charging or just want to understand your system get an good battery monitor that counts amps in and out.  The intelligent voltage meters like Balmer Smart Gauge are accurate, easy to install and self calibrate but all they tell you is the voltage of your battery bank.  The shunt based meters (like Trimetric) require more than just connecting, but by watching one can actually learn how your system responds.  Some will even send the info to your cell phone.

 -- Spiff