Some modern battery chargers, like the Victron Blue series which I fitted to charge the caravan battery from the mains, have a bluetooth monitor included. This makes it easy to check the battery voltage but only when plugged in – and you don’t really need to know this do you?

Of more use would be a monitor that is always connected to the battery or batteries to give you information. There are many simple meters that do this to a limited extent, most just provide the voltage reading and (usually just a very approximate) battery capacity. They can be wired in and put somewhere in the van or motorhome. I fitted one but found the information provided, just the battery voltage wasn’t sufficient to really understand what was happening as far as solar charging and the real battery capacity remaining.

So, of course being a bit of a senior geek I found just the thing or as my wife calls it ‘What? Another gadget?’ By the way, If you are looking for a guide to RV / caravan electrics – check out my eBook I wrote to assist others with this sometimes confusing topic. I have been pleasantly surprised with the number of people who have downloaded the guide and I have recently updated it with more recent information on Lithium batteries. Get the guide here.

I wanted a battery monitor that I could use with a smartphone app and more importantly, warn me if the battery state of charge was getting too low.

I did some searching and there are some great models out there but most are expensive – anything much over $60 I considered too expensive and in one case, the remote battery monitor I looked at didn’t provide much more than the voltage level and cost almost $80. There are others that don’t have a remote facility but do provide a lot of information but I considered around $190 too much to pay.

This is the one I settled on – the BM2 BLE Bluetooth battery monitor. You will find that these are sold under different names (and prices), including PowerTech, QuickLynks, IDrive and others but they all do the same thing and use the same smartphone app. I bought mine from Jaycar (they sell them under the PowerTech brand) but I paid more than I should have, they can be bought from Chinese eBay sellers but no cheaper then Australian ones.

Using the monitor is very simple, just install across the battery terminals, download the app – there are links to it below) and then stand within 10m of the battery and run the app. If bluetooth is turned off on the phone it prompts you to turn it on with a single tap and the connection was very quick and easy on my phone.

What I love about this monitor – The unit provides the battery voltage and a percentage charge indication. It also keeps a record of battery charge and it saves up to 35 days-worth of measurements in the device itself so if you are away from it for a day or two, no problem. When you are near the device it uploads the info to the phone.

If you want to get one for your vehicle battery as well, it has a couple of test modes so you can check it’s performance when under load (like starting the vehicle) and also the test the vehicle charging system so it isn’t just for caravans or motorhomes. It also has settable warning levels, so you get a warning on the phone when the battery charge is getting low or critically low. It has over voltage and short circuit protection too. For the price and the features I think it’s excellent value and when I compared the accuracy it was within 0.1 volts of my accurate test meter. More than one battery can be monitored on the same app too, just give them different names in the app.

This has to be one of the best, cheapest gadgets I have ever bought. NOTE: the maximum battery voltage is 20V, so don’t use this on a motorhome 24V starting battery. It will be fine to monitor motorhome house batteries though as these are usually 12V.

eBay listing : Search for BM2 BLE Bluetooth Battery Monitor

App download link (Android) : Google Play Store BM2 link

App Store link (Apple) : Apple Store BM2 link