DIY Projecta BM320 Smart Battery Gauge installation


We tackle a DIY Projecta BM320 Smart Battery Gauge installation to stop a repeat of the unthinkable: warm beer

On a trip to the Gulf, I discovered an electrical problem that drained the batteries completely. With no way to check the amps or the state of battery charge quickly, this led me to search out an affordable aftermarket product that could be easily retrofitted into an older model van, or in my case our 2001 Ultimate camper.

Ant Kilner


We’d been in camp for two days. It was super-hot and extremely humid at Karumba. There wasn’t much sun, and no 240v power available. We had the solar panel out, however, while there was some charge it obviously wasn’t much and with no amp gauge I couldn’t check it anyway.

We’d been fishing for the day and came back to find the fridge struggling and not cold, the fans were whirring madly, and when I checked the battery’s voltage, it was close to a disaster.

We found three problems at this point: The ambient heat was unbearable, the solar panel was struggling to work in the conditions, and the fridge fans were fighting each other trying to vent the fridge, hence using more power and not allowing the fridge to work correctly. These problems have been fixed since however not the way to read amps and battery condition easily.


After some research, my simple fix for this was to install a Projecta BM320 Smart Battery Gauge. This unit retails for $285 including GST and in most cases can be fitted by a competent mechanically/electrically minded person.

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There’s not much spare space in the Ultimate to fit the 2.4 inch LCD monitor. A spot on the bench wall under the sink worked because I could access the back panel easily and run the wiring through to the batteries discreetly. The meter has a click-in bracket that allows it to be removed if needs be, which is handy.

The next issue was the wiring. I was over a metre short in reaching from the gauge through the cabin and into the battery storage locker.

I took the loom to an electrician who modified it for me; however, once laid out and connected, it wouldn’t work. After lots of calls to Projecta we realised one wire was joined to another in error. Once corrected and tested, the loom worked perfectly. The point to note is that the wiring is precise, and while the 1.5-metre loom can be lengthened, it must be done correctly from the start.

The entire camper wiring now runs through the 500-amp shunt which means the gauge can monitor everything coming in and out of the charge systems very accurately. This was a little tricky to fit by myself, however, as you can see from the pic a ‘little bush mechanics’ and I got the job done.

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Apart from the loom and phone calls, it took a few hours of actual work to mount the gauge and conceal the wiring neatly through the camper. I found the gauge very easy to navigate through each screen and set. Its super simple to operate yet offers lots of info about the electricals.

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The BM320 features, as mentioned a full-colour LCD screen and a 1.5m loom with a simple click system to make things easy to fit. This system caters for various batteries including wet cell, calcium, gel and AGM and can handle up to 320 amps.

The installation manual explains just how easy it is to configure the low battery capacity and battery health alarm settings, date and time. It also offers a great visual on time to empty, time till full, battery voltage and amps charging and discharging.

This unit is excellent in that it’s easy to read, set, and that suits Jane and me as we travel around. The scary part is now we can see all this info we’ve become paranoid about keeping tabs on the charge – no more fridge drains here!

Apart from the stuff up with the wiring, this unit was easy to mount and set. I can see what power is being drained in amps, what charge is going into the batteries and the battery health.

For my needs, this unit has been an excellent fit-for-purpose job. For under $300, it’s offered peace of mind that at a glance we can see if there are any problems with the electricals.

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