ANCEL BM300 12V Battery Monitor, Bluetooth 4.0 Automotive Voltmeter with Charging, Cranking System Test & Alarm - Compatible for Solar Power Systems, RVs, Motorcycles, Boats, Cars, and Trucks

I wasn't looking for this monitor when I happened upon it on Amazon. I work in the motorsports industry and had not seen anything like this in the dealerships and shops I visit on a regular basis. And since I'm an electronics geek who's also in the motorsports field I had to try this.Before I ordered however I checked out the Ancel Battery Monitor App in the iOS store. There were only 4 ratings at the time with three 5-star ratings and one 1-star rating, the app looked promising so I ignored the one negative rating and ordered up.Once in hand I found the ANCEL BM300 Battery Tester/Monitor unit to be smaller than expected, measuring 3 ¾" Wide x 2" Long and 7/8" Thick. (Tapered design, see the pic below with measurements). The two lead wires are roughly 7" long with open clips on the end.To install I just had to hook up the leads to the positive and negative ends of the battery on my motorcycle. I then went into the app and expected to have to fool around with Bluetooth connections but the monitor had already paired to my phone and was showing the current battery voltage. Sweet! (see pic)From that point I started the motorcycle and the ANCEL BM300 showed the current charging rate and battery voltage with the battery voltage showing on a line graph. (see pic) I then ran the Charging Test and the charging voltage at idle and high RPM was shown. (see pic)The ANCEL BM300 will also perform a Cranking Test which shows the cranking voltage as a numeral and also on a line graph. Note: I like that the app shows good readings in Green and low or bad readings in Red. The Ancel also has a Trip setting which gives you a history showing times and duration for the vehicle (car, motorcycle, etc.) has been running.The app also has some more features in the System Set-Up allowing set two separate Power alarms at a % of your choice. These alarms will remind you once the battery is below the chosen percentages, I have mine set up at 70% and 50%. You can also choose to have a Daily Power Notification or Abnormal Cranking Notification.So far I am very impressed with the functionality and ease of use of the ANCEL BM300. The Bluetooth range is strong enough that I can check the battery status on my motorcycle from my living room with it being 30 feet away inside a garage with concrete block walls.The only negative I can think of is that as far as I can tell the Ancel Battery Monitor App can only work with one monitor at a time. If it worked with more than one vehicle I would buy one for my truck and my camper as well. I would also have an extra monitor to use for diagnosing battery/charging issues on the motorcycles and off-road vehicles I encounter for work.

This monitor works well to alert you to battery SOC and Voltage levels. This only works with Bluetooth but it would be better if you could monitor through a Wi-Fi connection as well. Cable length for the positive and negative connections are adequate. Unit is small enough to be unobtrusive on top of the battery and under the hood. Easy to install, provides accurate information to warn me when to put a charger on the battery and seems to be solidly built.

New EVs seem to have intermittent issues with their 12V batteries, such as not being charged properly or failing and causing the car to respond erratically, sometimes even while driving. After replacing the stock 12V battery in my new EV because it was not able to hold a decent charge unless it was constantly being charged, I wanted to ensure that my new battery was working, and that the car's charging system was working to charge the 12V battery. The BM300 allowed me to do this. It is a small device that can be attached to the battery hold-down clamp and transmits using low-energy bluetooth signals to your phone running their app. The app displays the voltage and state of charge. It also logs the voltage history over time, which is very useful for seeing how your battery is discharging and then recharging. The product does a good job at this and seems to work well with the app. Sometimes it takes a bit longer than others to connect to the app, but it usually does connect properly.About the only issue I have experienced with the app is how it interprets the voltage. The device does appear to accurately detect the battery voltage since it matches my multimeter when I test it myself. However, the app attempts to interpret the state of charge and display it as a percentage, also indicating if the battery is "ok" or "low" depending on this interpretation. You can also set alerts based on the state of charge if desired. The issue I experienced on two of these devices was that it would show a voltage of something like 12.5V and indicate that the battery was 90% charged. Another device on the other car's battery would show a similar voltage like 12.45V, but the percentage would be displayed as something like 65%. I have deleted the device and reinstalled it in the app and made sure the batteries were both set to AGM type (because they are), but the app seems to intermittently interpret the same voltage with wildly different percentages. Ultimately, this doesn't really matter as the state of charge percentage is really just for easily understanding your battery's state. The voltage appears to be consistently accurate and that's all that matters, especially if you know what your battery's voltage range should be.I was also able to confirm my car was recharging the battery properly while being charged as I could watch the battery voltage rise to the proper level during charging. This was reassuring as I was able to test more than just the battery using this device.So ultimately, it does work and the feature of logging the historical charge voltages over time is very helpful. If the state of charge interpretation was more consistent (it is correct some times), then it would get a full 5 stars. Customer service from the seller has been responsive and truly appears to be interested in resolving any issues. I just haven't been able to get that one feature to work consistently. However, I would still recommend this as it seems well made and does a good accurate job at recording the battery voltage, which is ultimately what counts.

Works great and provides very useful information. I am using this on an older flooded lead acid and let's me see how it's holding it's charge and discharge. This is the starter battery in my boat.

This battery monitor is an outstanding instrument for monitoring, assessing, and diagnosing 12V battery condition. I have installed them on all my backup batteries and on my car batteries. It's easy to set up and use. The app is very useful. It survives the dampness, cold, and heat of a car engine compartment.

The Ancel 12 volt car/truck lead acid battery works exactly as I expected. I was having problems with the 12 volt batteries in both of my vehicles discharging unexpectedly. This device keeps track of the charge level of the 12 volt batteries so I can charge them before they are too low to start my vehicles. I can check the charge level using Bluetooth on my smartphone. I stand close to my car and open the Ancel app. It quickly performs several checks of the battery's condition. It attaches across the positive and negative posts of the battery. It comes with everything needed to set it up except for the app which can be downloaded for free. This product has ended my anxiety about discovering my vehicle's battery is dead when I need to go somewhere.