Redarc Smart Battery Monitor
install

our set up

At the heart of our camper trailers 12volt system are two 120 amp-hour AGM deep cycle batteries wired in parallel with a Redarc BCDC1225 DC to DC charger I installed in 2012.

I added a power source to the BCDC1225 blue wire that goes back through an unused trailer plug pin & to the positive on the vehicle side Anderson connector. When the Anderson & trailer plug are connected the BCDC1225 is run as a DC to DC charger. When the trailer plug & Anderson are disconnected ie no power to the blue wire the BCDC1225 runs as a MPPT solar controller. The wiring diagram below shows how this is done and there is more explanation under the 'my input solution' heading in the install article https://www.campertrailers.org/bcdc1225_install.htm The later Redarc BCDC1225D model has different wiring with solar as a priority. If the engine is started & the battery needs more charge then the charger will bring the alternator in.  

voltmeter

I originally installed a voltmeter, however it is not the best way to monitor battery capacity as it will only show the true state of charge when the battery is at rest, that is with no charge or discharge for at least two hours or more. Makes it hard when a 12volt compressor fridge is cycling or turning on & off to maintain the preset temperature. When an AGM battery is being charged a voltmeter will show a charging voltage of up to 14.4volts & 13.2volts when fully charged in float with the charger still connected. On the otherhand discharging will pull the voltage below true capacity. At rest an AGM battery will show 12.8 volts.

12volt system with Enerdive Elite battery monitor	AGM battery voltage at rest

next step

I got serious about a battery monitor when Carol needed a CPAP at night so I installed an Enerdrive Elite battery monitor in 2014 to better understand the battery capacity, charging & discharge. I have never been really happy with the performance of the Enerdive Elite. It is not a set & forget monitor & requires frequent synchronizing, but this may be down to the way we use the batteries.

The Redarc BCDC1225 has the two 120 amp-hour AGM batteries fully charged from the vehicles alternator on the drive home after a trip & we are usually away once a month, except for around Christmas over the summer period when it is too hot inland & the campsites along the coast are crowded. At home I place the solar panel out every couple of weeks to fully charge the batteries. I think this may be the downfall of the Enerdrive Elite, perhaps the monitor may need the batteries sitting on a 240volt multistage charger in float mode. We had nine years of service from two 120 amp-hour Ritar AGM batteries by charging with solar every few weeks between trips.

This Enerdrive Elite monitor consumes 0.1 amps in standby, that is 0.1 amps an hour, (0.1 amp-hours), so over a twenty-four hour period it will consume 2.4 amp-hours, over a week 16.8 amp-hours & over a month 72 amp-hours, so you can see why you need to throw the solar panel out every few weeks with no 240volt multistage charger sitting in constant float.

In comparison the Redarc Smart Battery Monitor draws 2.4 mA to 3 mA, that is 0.0024 to 0.003 amps in standby.

our power requirements

We are not heavy 12volt power users by any means. The Engel fridge consumes on average around 20 amp-hours in 24 hours depending on the season https://www.campertrailers.org/fridge_draw.htm  

& the CPAP around 11 amp-hours overnight https://www.campertrailers.org/cpap_12volt_battery_supply.htm 

So you could say an average of 30 amp-hours per day depending on the season plus at times charging the camera, phone, ipad & laptop batteries, all done by 12volt & no 12volt to 240volt inverter. Our 150 watt solar panel easily has the batteries full by late morning to lunch via the Redarc BCDC1225 inbuilt MPPT solar regulator.

If we camp for four days we could consume 120 amp-hours with no solar input reducing the battery capacity to 120 amp-hours or 50%. Relying on solar to fully charge the batteries each day is not reliable as we seem to attract rainy weather or plenty of shade in the forest locations we prefer to camp & need to chase the sun with the solar panel.

Redarc Smart Battery Monitor

I recently installed a Redarc Smart Battery Monitor which is the latest product from Redarc & by all accounts is a notch above the rest, stated to be up to five times more accurate than leading competitors. The heart of the monitor is a shunt with electronics attached & connected via Bluetooth 5.1 to the RedVision app. A battery sense lead gives power to the shunt as well as monitoring the temperature of the positive battery terminal. 

All info can be found at https://www.redarcelectronics.com/au/smart-monitor  

installing

The Redarc Smart Battery Monitor shunt is a little larger than a shunt normally used as it has electronics attached which presented a problem where to locate it within the limited space of our battery box. A control button on the shunt also requires access during the bluetooth pairing process with a phone during setup. I could not place it in the same location where the Enerdrive Elite shunt was & there was no room on the plywood face next to the battery. The only option was behind the plywood face & I thought if I ever have to pair another phone, then it would be only a matter of four screws.

A booklet comes in the box with easy to understand instructions if you want to install the monitor yourself. All negative input leads are connected to the far side of the shunt & only one negative lead on the other end of the shunt is connected to the negative battery post as you would normally do when installing a shunt. The shunt cable connections are marked accordingly. There is also a battery sense lead that is connected to the positive battery post.

 configuring

I downloaded the RedVision Configurator App & checked my phone to make sure I had bluetooth turned on. When power is first connected to the shunt a blue light will flash on the shunt indicating pairing mode, but will automatically time out after 90 seconds. Bluetooth pairing mode can be entered at any time by holding the control button down on the shunt for 0.5 to 3 seconds. Once paired the light will turn solid blue.

I am no computer expert, but I have found when pairing bluetooth or wifi connections it is best to set the bluetooth or wifi pairing process going on the accessory first, open the phone settings, go to bluetooth or wifi & make sure bluetooth or wifi is turned on. Then find the accessory on the list & hit connect. After the phone has paired with the accessory you can then open the app knowing you have a connection between the two.  

Using the RedVision Configurator App, the battery type, battery size in amp-hours, maximum charge current in amps, low state of charge alarm as a percentage & the low voltage alarm in volts are entered & saved. Next step is to hit the program tab, the specifications are saved & written to the shunt.

I then downloaded the RedVision app. The app allows you to view the battery state of charge as a visual battery shaped graph & also as a numeral percentage, the number of amps flowing in as a green arrow with time to fully charge, the number of amps flowing out as a red arrow with time remaining at that discharge rate, along with the positive terminal temperature.

 redarc help line

I opened the RedVision app showing the battery voltage at rest. I then connected the solar panel to the Redarc BCDC1225 & watched the app as the voltage & amps started to climb with a green arrow, but there was no battery percentage on the graph or in figures. I thought ok the battery would need to be fully charged to register the percentage first. By mid afternoon the Redarc BCDC1225 was in float mode & the RedVision app showed that was correct with 13.3 volts & 0.8 amps trickling into the battery. But still no percentage figures.

I rang the Redarc help line & told the tech my problem. He said the Redarc Smart Battery Monitor needs to learn where full is by cycling the battery a few times. Well that made sense. I hooked the solar up again the next day, the BCDC1225 went into boost mode & after several minutes went into float. The app then showed the battery was 100%. I ran the fridge for the entire day to drop the battery voltage & then placed the solar out again the following day. In the end the app showed 100%, 0 amps, 13.2 volts, the battery was no doubt full to the brim. I big shout to the Redarc tech team for the full support in understanding how the smart battery monitor works, all within reach by a phone call. 

understanding the app readout

The readout on the app is easy to understand at a glance.

battery capacity The percentage shown on the graph & in numerals show the battery capacity from 100% to 0%.

green in arrow The green arrow signifies the battery is charging, displays the amps along with time to 100% capacity.

red out arrow The red arrow signifies the battery is discharging, displays the amps along with the time to 0%.

If there are amps coming in & out at the same time, the app will show the result ie 6 amps in & 2 amps out, the result will show 4 amps with a green arrow.

low state-of-charge voltage alarm I have set the low state-of-charge alarm to 40%

low voltage alarm I have set the low voltage alarm to 12.1 volts.

discharging	charging	fully charged

feedback

We have been away camping for a few days & I am very impressed with how the Redarc Smart Battery Monitor preformed. One of the best features is the ability to check the camper trailer batteries state of charge as we drive via the app while they are being charged by the Redarc BCDC1225 from the vehicles alternator. When 13.3 volts is reached I know the charger is in float mode & the app shows minimal amps slowly filling the battery to full capacity & ultimately 13.2 volts & 0.0 amps. 

I had a distance of around fourteen metres using an iPhone6 until I lost contact with the shunt.

further reading

Watts Up meter http://www.campertrailers.org/watts_up_meter.htm
CPAP 12volt battery draw https://www.campertrailers.org/cpap_12volt_battery_supply.htm
35 litre Engel fridge draw http://www.campertrailers.org/fridge_power_consumption.htm
40 litre Engel fridge draw https://www.campertrailers.org/fridge_draw.htm
12volt compressor fridge battery supply https://www.campertrailers.org/12volt_compressor_fridge_draw.htm 
laptop 12volt power supply  https://www.campertrailers.org/laptop_power_supply.htm 
Rob & Carol's Track Trailer Eagle https://www.campertrailers.org/robcazeagle_canvasupdate.htm

article by Rob
 

April 2024