Battery Monitors, what works and doesn't


Looking into some options and I like the Victron 712, but I've read some poor reviews of the support of lack thereof. I see Renogy has a panel, but so-so construction quality, but it's half the price. There's a device called Battery Checker 100 I think it was but in Australia only, so that's not very helpful here. Any other devices that I've missed, just planning to monitor my primary and auxiliary battery. Victron unit has some nice features and app, I'm curious who's used it and what their experiences have been like. Thanks.


Well-known member
love my BMV-712, not a single complaint.. the nicest and most accurate battery monitor Ive ever used personally... poor reviews for lack of support sounds an awful lot like PEBCAK, and you cant expect victron to fix that.

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I have the older Victron BMV-700 with a separate blue tooth dongle. It has worked beautifully over the past 5 years or so.

I have not had to contact Victron support, but their community website is very useful and they are very forthcoming with documentation and protocols.

The Renogy offering appears to be a re-branded version of one of the many low cost units from China, I am not sure Renogy does any engineering, but are a procurement/branding company.


Good info guys thanks, that's what I was hoping to hear. I'll be sure and go through a dealer as mentioned too for piece of mind and support.


For SoC% of a lead bank, no coulomb-counting, little calibration / adjustments needed

nothing is more accurate than old-school Merlin SmartGauge.

Sold by Balmar in the US, not to be confused with their new (beta) SG-200.

May be cheaper finding a UK source.


tk15 coulombmeter works good for me, I got 5 of them on all my batteries. The 50 amp model cost about 25 dollars, the 350 amp model cost about 50 dollars. They work with any battery lithium/lead acid. Counts amps in/out of battery. If you used 25 amps today, you know tomorrow you have to put at least 25 amps back in. I been using them for the past 3 years 24/7 never had one go bad. I like that on the screen it shows you everything without having to press a button to cycle between voltage/percent/amps. The backlight LCD screen blinks on off when charging, its lighted when discharging, the backlight is off when its neutral not charging/discharging. Its easy to program, you program your battery amp hours, the battery full voltage and also the battery empty voltage.
drok coulomb meter.jpg


We also use the BMV712

Just be sure to calibrate it properly, and again every so often for (more) accurate readings.


Any cheap Ah-counting "wattmeter" that does not ask for CEF and Peukert coefficient is only going to give a ballpark SoC, maybe 10-20% off.


Well-known member
Unless you have a Lithium bank, if you pull 25Ah out of your bank.. it takes more than 25Ah to restore your bank to the same SOC it was before.. there's significant losses involved with lead chemistry..


True for LI as well

That is the CEF variable, Charge Efficiency Factor

can get from some makers' tech support, or measure for your specific bank.

It does increase a bit with age.


Well-known member
ayup, its just significantly smaller.. 94% is the CEF for a Trojan T105 recommended by manufacturer, and 99% for a Battleborn recommended by manufacturer..

When you put 25Ah back into your Trojan, you really raised its SoC to 23.5Ah, your Battleborn is at 24.75Ah.. so if thats your charge cycle daily, your drifting down by 1.5AH a day on lead and 0.25AH a day on LFP.. so 10AH loss a week v 1.75Ah loss a week, the former could really screw the pooch if your not compensating for that.. the latter is little more than a rounding error if your SOC monitor is not compensating for CEF.

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We use a BMV-712 and find it excellent. I haven’t had any contact with Victron support except through research on their forums, so I can’t speak to responsiveness.

I went all Victron for my trailer solar system and have been very happy with their monitor, solar controller, and mains charger. I don’t have an inverter.

I like having all the parameters and info in one app also.

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