What's a good battery level monitor?

Since you don't mention any inherent issues with the existing method I recommend getting a panel mount LCD voltmeter.

https://www.amazon.com/Display-Voltmeter-Digital-Voltage-Backlight/dp/B07Q21N5ZW



Otherwise I recommend the Victron.

obiwancanoli wrote:


Go to www.amazon.com, type "Victron 712" in the search box at the top of the page....

That's a good way to find the Victron 712, but @HomelessByChoice was asking about the picture that @MrWizard posted, which is not a Victron.

I'd like to know too.

I found what I think is a product link for it based an image search, the DROK Automotive Multimeter, but that link leads to an error page, so apparently it's been discontinued. But Drok sells many other inexpensive meters, so I'd still like to know if @MrWizard has been happy with their products.

The OP did ask for a 'good' meter not necessarily a 'cheap' battery monitor. For a good meter, you can't go wrong with the Victron 712 (with a display) or the Victron SmartShunt if you are happy to look at the data on your phone/tablet/laptop. If you would prefer 'cheap' then any of the many no-name panel voltmeters or current shunts will work.

I recently posted this:
https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/30168196.cfm

Aili battery monitor is what I am using and I love it. And it's only ~$45 on Amazon. Gives you all the info you probably want/need. Doesn't connect to your phone, but it's way less expensive.

The issue with many (most?) of the cheaper battery monitors is that they don't resynchronize with a fully charged battery, and they don't account for charging efficiency. As a result they can drift well away from the true SOC over time, which can provide confusing information.

Better monitors will detect when your battery is fully charged (based on the charger switching over to float) and will reset the SOC back to 100% and will also account for the fact (with lead acid) that you need to put 21A back in to replace the 20A you took out.

Charging inefficiency is a problem that never goes away with any lead acid battery, and only gets worse as the battery ages,
That's why an auto reset monitor, is not as important to me , as knowing my batteries and system,I know by looking at the charge amps near the end of cycle, the monitor already says 100%,

What's important to me, is the discharge count and the SOC from my use, so I know how many Amp hrs were used, Capacity (50% ,70%, 90% ?) right now
I know whether I must charge right away or have sufficient unused capacity to hold me until later in the day,
I do not know how many Amp hrs recharge it takes to replace 100 Amp hrs used, 5 more, 10 more, 15 more ??
And it's been many years since I even attempted to find out, when I tried I had (2) amp counting power meters wired in series with the house batteries in a different MH, identical meters,they only counted one direction, so I installed them in reverse to each other, one only counted discharge , the other only counted charging , I reset them each day at the end of that days recharge, I don't remember the numbers, but the recharge to full, goto float, was more than I expected, no MW no coffee maker , a 300w inverter for the laptop, tv, and phones, it was about 2005 I think, maybe before then
This monitor I have now, is the best one I have used, the most useful,the most info
I will try to find the brand/model info, it's been almost 3 years, and I think the seller was in kentucky, I'm thinking this was on eBay,
BTW the display/control module (in the picture) is powered 5v usb, and is wireless,
The brain module and the Hall Effect Sensor are located at the 198 ampHR Deka 4D AGM that is one half of my 400 AmpHR battery bank, there is No Wiring connecting the 2 modules, I can move the display any where in the RV, without changing any wiring

This is the seller elite.element on EBay, I bought from, and the power monitor, he is in Walton Ky,,
DC battery power monitor

It's all over ebay for less $$$ , but shipping from China sellers,
I think he was the first one to bring it to the USA


Click For Full-Size Image.

this is the one I recomend. accurate, simple and deicent shunt.

https://www.amazon.com/AiLi-Battery-Monitor-Voltmeter-Motorhome/dp/B07CTKYFTG/ref=pd_sbs_328_3/130-7969589-8312703?_encoding=UTF8&pd_rd_i=B07CTKYFTG&pd_rd_r=b5ea6997-1a5c-48fc-8d2e-94634fd1dc4e&pd_rd_w=3HvIh&pd_rd_wg=PB9As&pf_rd_p=ed1e2146-ecfe-435e-b3b5-d79fa072fd58&pf_rd_r=XBNJSY5Z5WY7NH7GGP4M&psc=1&refRID=XBNJSY5Z5WY7NH7GGP4M


Steve

dieseltruckdriver wrote:

phemens wrote:
I like the Victron 702, with Bluetooth so you can monitor from your phone.

I really like my Victron 702 also, but the 712 is the one with bluetooth, unless you add a dongle.

You're right, I have the dongle, thanks for the clarification!

Regarding the drifts and possible inaccuracies due to a variety of behavioristics of charging and/or the batteries themselves....

I can see how IN THEORY you could have an issue if every time you charged your batteries you immediately STOPPED charging once your monitor said you are at 100%. If you were in fact not 100% full (...let's say the true SOC is only 95% even though your monitor incorrectly says 100%) and then you used your battery down to 50% as stated on your monitor, you would in actuality only be at 45% SOC. Then if you charged back up to what you thought was 100% and immediately stopped charging once your battery monitor says you are at 100% but in fact if it once again fell short you might only be at 90% true SOC. If you repeated this many times in a row, then I can see you'd have a problem. (drift)

Perhaps a good rule of thumb would be to make it a habit to continue to charge your batteries for a little while beyond the time when your monitor says you just reached 100%. Or, if your monitor shows amps going into your battery while charging, you can get a sense that way as to how much "charging" is still happening once your monitor reaches 100%.

This "drift" problem gets fixed/reset anytime you do have a situation where your charger stays on/active for a long enough time after your battery monitor says you are at 100%. For example, if you do find yourself plugged in at a campsite and your monitor reaches 100% (even if your true SOC is less then 100% because it has been drifting) while you are sleeping and then continues getting you to true 100% until you unplug. Or, if you are driving from one destination to another and your alternator is charging the battery...if your monitor gets to 100% (when your batteries are actually at less than 100%) the batteries will continue to get closer to 100% as long as you are driving. This "erases" any of the drift delta that might have built up.

Also: Most battery monitors tell you the Voltage it sees on the batteries. From most 12v SOC charts you can see that 12.06v resting voltage corresponds to 50% SOC. So if you ever see your battery resting voltage at 12.06v REGARDLESS OF WHAT YOUR BATTERY MONITOR SAYS percentage-wise, you should charge your batteries. Likewise, when your batteries are truly fully charged to 100% they will likely read ~12.7v at rest. If your monitor says it is 100% full but your batteries are only at 12.4v or 12.5v then you should continue charging until you get all the way up to 12.6-12.7v at rest. If your batteries never get there, then there is likely a problem with your monitor voltage reading (you can test by putting a voltmeter directly on the batteries) or a problem with your batteries.

-Chris