QUICKLYNKS BM2 Bluetooth Battery Monitor 12V Car Battery Tester for Lead Acid, Auto Battery Load Tester with Cranking Charging Test, LowVolt Alarm for Car/RV/Motorcycle/Truck/Boat/Solar Power System

I got this to use on a secondary car that is left parked for potentially long periods of time. I have a solar powered battery maintainer hooked up to it but I also wanted to easily check on its state of charge just in case. The BM2 fills that purpose perfectly. Installation is simple. You just clip its wires to the respective battery terminals and secure the unit somewhere safe (I just zip tied it to the top mounting bracket of the battery). After installing the app, it detected the monitoring unit and started reporting the voltage automatically. You can set alerts and also offers start and charge tests. It does use Bluetooth, so range is limited (especially considering it has a metal hood covering it normally). YMMV. Worst case, you may have to walk close to the car to get a reading. But at least you don't have to pop the hood or mess with the battery. It does keep a history which it updates to your app next time it connects, so you won't lose data points. All in all, it does exactly what I need.

Bought this here instead of Aliexpress bc its a similar price. Very simple to install and works immediately. Download the Battery Monitor BM2 app from the app store. You have to be in bluetooth range to get a reading. You can get a current reading, or charts that track voltage over time, and you can set notifications to let you know when the voltage drops to certain levels.

This is a great little device, it helps me keep up with my batteries. And that's very important in a off grid system. Does what it's serpose to do. Good app that goes with.

Got this for a hybrid so the cranking feature isn't used. But the car is used infrequently and there are some occasional electric loads as the car does diagnostics and other stuff in the background, so monitoring it is helpful to see when it needs a booster charge. It works exactly as advertised, and I'm surprised that I can be anywhere in the house and still pair with the car for a reading.

Very useful

I have a charge controller and large battery bank for my solar. My charge controller lacks bluetooth features. It does display the current voltage, but I have to go to the unit to see it. Likewise, it doesn't have a way to transmit or store historical data. I bought the BM2 thinking it might be a quick fix for this, and I was pleasantly underestimating the device. I connected it to the leads of the battery, opened the app, and connected the device. There was no pairing issue, no hunting around for some long forgotten Chinese app. Everything was easy. The device was detected and linked instantly almost. It let me select my battery type, name the device, and it went to work. I saw the voltage readout on my phone, and it started charting the voltage. This was in the middle of a sunny charge cycle, and the voltage was consistently rising, updating every second on the app. As for accuracy, it matched the readout shown on my inverter precisely. I was so blown away by the speed, usability, and simplicity of the device and its app that I considered buying another for the car. If you have a battery for utility, camper, truck, solar, boat...you need this. It beats pulling out the multimeter, it is accurate, and the ability to chart the data is priceless. Given the insights the data will provide, I don't doubt this device will pay for itself within a year.

PHEV use case - Excellent product; easy to install; great value; limitations discussed I decided to get a battery monitor after my 2019 Kia Niro PHEV gave me a mysterious battery alert, but neither the built-in diagnostics nor anything I could read through a scanner (TopScan https://www.amazon.com/dp/B0C3QQYQ1B ) revealed anything. The active tests supported by the car itself through the TopScan wouldn't allow me to do any useful tests with the battery. So, battery monitor time. At least with a battery monitor I'd be able to get some degree of long-term diagnostic data, so I hunted around, and this one came up top after all my research, even though I would have been happy to pay way more had I found a better-seeming option. A few notes on the pics: In my case (Kia Niro PHEV), the low-voltage battery is stored behind the right rear wheel, and is accessed through a hatch in the trunk. The positive terminal for the battery is covered by a plastic cover, which can be removed by popping it off its hinge pin. It's necessary to cut a small chunk out of this cover to be able to mount the positive terminal of the monitor and still be able to close the cover to protect the battery's positive terminal. Once I got it out, I found that the cover was actually considerably more solid than I expected. I ended up using an oscillating tool to trim out a slot, and I cleaned it up with a rat-tail file. Lots of other tools would work, e.g. a coping saw. There wasn't really a good place to mount the monitor next to the battery, so I resorted to a couple of zip ties. Another option would have been double-sided tape, i suppose. Given these encomia, I should point out that the utility of a monitor like this is likely to be limited specifically with a PHEV. In particular (at least with my car), there's no good way to do a cold crank test that completely isolates the low-voltage (auxiliary) battery from the high voltage battery. This is not the fault of this product, of course, it's just a fact of life with PHEVs unless the manufacturer provides active test features to support such isolation. You'd think that it'd be an obvious feature for the manufacturer to provide, but even the official manual doesn't provide any real method to do a crank test, short of pulling the battery and putting it on a load cell of some sort. The average car owner isn't going to be able to do this, of course, so as far as I can tell all you can really do is try to monitor the gradual degradation of the charge state of the auxiliary battery, and just get a new one when things look bad enough. The cost of swapping the battery is bound to be less than the cost of getting any professional to try and perform any diagnosis on it - at least where I live. Bottom line - great product, and great value.

It is important to know this battery monitor will only communicate with a Bluetooth device -- like an iPhone -- over a very short distance. Maybe a dozen feet. And said iPhone needs to have its Bluetooth turned on, which is a small but continuous power drain. My Quicklynks unit is problematic. It tends to underestimate the charge on the battery, complaining that it is almost out of charge when it still has plenty of cranking power. Also, it sometimes says the battery is still being charged after I've turned off the engine. I'm learning to take its reporting with a big grain of salt. I still think it has some value, but I'd be happier if it was more accurate, and had more transmission range. Before I bought this unit I had purchased another, similar device that was supposed to link up with my WiFi network, and do much the same in terms of monitoring the battery. Unfortunately that device also suffered from poor range. It could not link up to my WiFi system while sitting in my driveway, just outside my house. That, plus a difficult setup procedure, led me to return that unit for a refund. If I can find a better battery monitor -- one I can trust, has WiFi capability and decent range -- I'll probably replace the Quicklynks unit. For now, I'll leave it installed. Update March 27, 2019 -- Unit is no longer working at all. It has been reading "0% Charge" on the battery, when there is still plenty of power to crank and start the vehicle. I can no longer return it through Amazon -- I'm past the 30 day limit -- so I am trying to get the vendor to replace or refund it under warranty. But their phone number listed on the Amazon product page has been disconnected. I haven't given up yet, but I'm probably going to have to go through Amazon to get the vendor -- Quicklynks -- to respond. Short version -- don't buy.