Thoughts on this battery meter

Folks that full time or have a more specific need requiring more information from their system is a valid point. Those of us that are weekend warriors, but do take proper care of our 12 volt systems, I don't believe need the higher end monitors. I use a hydrometer & smart charger for my batts & keep them in storage during the off season on a trickle charger. The Volt Minder that I use is accurate enough for my needs. I checked it with my Fluke upon purchase & it was within .02 reading. and it sure beats the hell out of the coach monitor. :B

The only way to measure battery SOC is with a battery monitor which as a previous poster said uses a shunt to measure current going into and coming out of your battery(s), or using a hydrometer, messy and impossible to do with an AGM.
The two choices are basically the Trimetric from Bogart or Victron (I have the Victron because of size).
Measuring voltage can be relatively accurate only after a couple of hours with out input or current drain.

Roy, that's the chart I use today, I have it taped inside the pantry!

So I messaged the Flea Bay seller and it turns out that the number displayed is voltage, NOT state of charge. It threw me off that the listing indicates that this is for "12v lead acid batteries only" but that they are showing 50.5v in the illustration. Oh well, Chinese marketing....so it's basically a voltmeter with a cool looking SOC bar graphic added. Basically took my paper chart and baked it into the voltmeter with that gauge.

I may spring the $10 on it, if for nothing else so that DW has a more visual reference on how the batteries are doing before she turns on another light....

IMO the voltmeter you have now already does that. No need to change it out for another.

You obviously know to take the voltage for the SOC estimate when things are not running so much, which I call the "morning voltage."

IE before solar can get the voltage jacked up (which means being up early in the summer), and when the furnace is not running to make the voltage lower than it really is.

Keep your money in your pocket! :)

If it just measures voltage it's a volt meter. A battery meter must involve a shunt to measure the amps in and out of the battery. It must also be programmable to tell it how large your battery bank is.
That might be a fine volt meter that would give you some sort of idea how your battery is doing but without a shunt it's no battery meter.

From what I can tell, it is a voltmeter with a graphic representation of volts at the top. The other number might be state of charge, but 50% would not correspond with green so who knows. It is probably accurate at reading the volts. State of charge, it's probably the same logic as we have on the OEM control centers in our RVs. You know, the 3 or 4 LEDs for battery, holding tanks, etc.

If you are up for installing a shunt at the battery negative terminal, and running a 4-wire phone or thermostat cable to that meter location, for $40 you can have an ebay combo meter which tells you volts, amps, aggregate amp-hours, battery state of charge, and more.

I have not seen that specific meter, but I have seen several low-cost digital volt meters reviewed by experts and they are suprisingly good.

Do compare the reading a few times to a known good digtal multi-meter like the crafstman at my side just now or a Fluke, but most of 'em are good.

And generally for 12 volt systems (There are exceptions) you can tie power and sense wires together and make it a 2-wire hookup.

It appears to be measuring the capacity of the battery & not the voltage.I think I'd rather know the voltage @ any given time.

Probably worth a try @ that price, but be willing to wait any where from 4-6 weeks for delivery.

I use a "voltminder" myself, basic information, but good enough for me.

I also use a DC VOLTMETER to read my two switched battery banks when in use. Reading the displayed DC VOLTAGE can only be used to get you in the ball park of % of charge. The only real way to determine % of charge is doing the hydrometer test.

However for me just getting close is good enough as I know when the bank drops down to 12.0VDC it is approximately 50% charge state and this is where I will stop using my batteries until I re-charge them...

This is the conversion chart most of us go by to determine state of charge. If your shown color bars corresponds to this chart then it could be used to tell you the approximate state of charge of your battery. I see 50.5 shown on the meter reading so I am guessing this is a PERCENT READING instead of DC VOLTAGE reading. I would rather see actual DC VOLTS being displayed but either reading would work for you I reckoon.


My homemade BATTERY MONITOR PANEL looks like this using two each 0-19VDC VOLTMETERs and a +/- 0-75AMPS DC current meter.


When we are camping off of the batteries this meter is our most important meter group to keep a close eye on during our one day/night run off the batteries. All is planned out to drop the displayed DC VOLTS down to 12.0VDC by 8AM each morning when we are allowed to run our 2KW Generator with the 30AMP Trailer Shore power Cable plugged into the generator 120VAC receptacle using an RV30A-15A adapter. This will recharge our battery bank back to its 90% charge state in a quick three hour generator run time.

We can do a good 12-14 cycles of the 50% to 90% charge state using our on-board smart mode converter/charger without doing damage to our battery bank. After the multiple charge state cycles we have to do a full 100% smart mode battery charge routine which takes over twelve hours of generator run time to bring the battery bank back to its full performance charge state. Since this amount of time is usually not allowed at the camp grounds this is when we will head back for the house and do the full 100% charge cycle then.

This is how we use our homemade BATTERY MONITOR when camping off our battery banks.

Roy Ken