Introduction

The Doc recently bought the KICKASS Battery Guard. A device you attach to a 12-volt car battery to monitor voltage, ensuring the battery’s overall health. It connects via Bluetooth to your phone or Tablet.

Commercial grade versions exist for 4X4s, caravans and RVs and can cost thousands of dollars, even cheaper units can cost several hundred dollars. They are made by REDARC, BMPRO, Enerdrive, Victron, etc.

Because of the Wuhan flu lockdown, The Doc did a comparison with similar products like the CTEK Battery Sense and the BLE Battery Monitor, all costing under AUD$80. The Doc calls it the poor man’s battery monitor!

The BLE Battery Monitor won hands down, it was the cheapest, had the most features, was reliable and the app had fewer bugs than the other two. The Doc bought the BLE Battery Monitor on eBay here. EDIT: or for $30 including postage here.

Warning: this article does not apply to 12-volt Lithium batteries, because of their different chemistry and flat voltage curve. 12-volt Lithium batteries used in a car, caravan or RV should have a battery management system to maximise battery life. Many of the Chinese made batteries do not, despite costing nearly $2,000. It is one reason why so many fail, a rather costly failure!

Read on if you want to know about the details.

The contenders

The contenders are the:

• KICKASS Battery Guard
• CTEK Battery Sense
• BLE Battery Monitor

KICKASS Battery Guard

The KICKASS Battery Guard is a relabeled version of the intAct Battery Guard originating from Germany, which has been around for a few years. At $79 it is overpriced for what it is, both the CTEK Battery Sense and the BLE offer more for the price. The Doc did see the intAct Battery Guard (the identical OEM unit) being sold for $120 in Australia. There are some real rip off prices in the 4X4 marketplace.

The KICKASS Battery Guard is the smallest unit but only gives voltage readings while the unit is connected. It stores no data to download later – the CTEK and BLE both store data up to 30 days.

The Doc ordered two units. one had ring style connectors and the other had fork connectors. The fork connectors were easy to fit and appear to be the updated model. The ring style connectors were too small to fit on the battery post (M8 size bolt). The Doc tried to drill the connector bigger but the connector just bent and twisted. He cut off both twisted terminals and fitted larger fork connectors with dual wall shrink tubing. Then both terminals fitted with no issues.

The Battery Guard app both iOS and Android was not a smooth experience. The Doc got the iPhone app to work after rebooting the phone. Warning: with Android you must give location permissions or the app will not work. The app was developed in Germany and the app does not properly display English – so you get part English and part German displaying in the app. This happened on the iPhone and the Android Tablet. The app can be slow and a little confusing due to the German and English. The app seems rough around the edges.

There are variations between individual units. The Doc had two units installed on one battery, Unit 1 gave a reading of 12.93 volts, Unit 2 showed 12.96 volts. The readings are close enough for the intended purpose, monitoring battery voltage.

The app has three main messages InReach>Connecting>Receiving. The voltage data is updated only when Receiving is visible. Receiving only worked reliably within 2 metres of the unit. InReach and Connecting can work over a greater distance, but Receiving does not work reliably. In summary:

The Doc believes the other two units offered more than the KICKASS.

CTEK Battery Sense

The CTEK is the largest of the three units, but its build quality is also the best. The CTEK at $78 is only one dollar cheaper than the KICKASS, but a lot more than the BLE at a mere $33.

CTEK is a well-known and respected charger brand based in Sweden.

The CTEK is the only unit with an inline fuse and the only unit to monitor battery temperature.

The unit stores data for up to thirty days, but The Doc found that both the iOS and Android app did not reliably download the data from the unit to the app. It can be annoying when the data does not update for a few days. The summary screen updates, it is the graphed data which does not update properly.

The iOS app has more functionality than the Android version. The iOS app monitors and graphs voltage, state of charge and battery temperature. The Android only displays voltage. The iOS app has a bug, when looking at battery temperature the graph is showing voltage. When you select the voltage tab it displays battery temperature.

There are many online reviews of this unit. In summary:

BLE Battery Monitor

The BLE Battery Monitor ($33 on eBay) is also marketed as the Mean Mother Bluetooth 4.0 Battery Monitor (for $60), the Century BM12V Battery Monitor (for $70) and the Baintech Bluetooth Battery Monitor (and probably others). The Doc has the BLE Battery Monitor and considers it to be the pick of the three battery monitors, based on price and features.

The BLE had the best features of the three, plus the app was the best. You can effectively use the BLE and app as a full-time battery monitor. Battery monitors can cost hundreds and sometimes thousands of dollars to buy, the BLE is the poor man’s battery monitor!

Warning: The unit can only connect to one Bluetooth device at a time. If the unit is connected to Phone A it cannot connect to Tablet B. You must disconnect A to connect to B.

Because the unit holds data for up to 30 days and can sync with the app, you have data 24 hours a day – not just when the app connects to the unit like the KICKASS.

The app graphs voltage over time, cranking tests and an alternator charging test. Plus, the app is easy to use. The Doc is not sure how to do a cranking test. It seems you must select cranking test in the app and on the first occasion it performs the test. Later cranking tests seem to occur every two weeks, not on command. Alternator charging tests can be done on command.

When you open the apps for the CTEK or the KICKASS you choose which unit to connect too (if you have more than one installed), the BLE just connects to any nearby unit and you must go into Settings>Bluetooth Device and select the one you wish to monitor. The Doc is use to it now, but it was a little inconvenient learning how to do it.

It appears. the Mean Mother is an expensive rebadge of the BLE. The Doc suggests you save money and buy the OEM version.

Conclusion

Both the BLE and the CTEK give you functionality to properly monitor and maintain your battery’s health, without the expense of a commercial grade system costing several hundred or even thousands of dollars. The BLE will even send you an alert if trigger points are reached (your phone’s Bluetooth must be enabled).

The Doc uses the BLE to monitor the Patrol’s main battery, its auxiliary battery and the battery box. One BLE unit for each battery, the monitoring system cost less than $100. Plus The Doc can monitor alternator charging and the cranking performance of the main battery.

Best Unit Overall: the best unit based on price and features is the BLE, by quite a margin. It has great functionality for a bargain basement price of $33.

Best Unit based on quality: the CTEK Battery Sense is the best made unit, edging out the BLE on quality more than functionality – although the inline fuse can be handy. Costing $45 more than the BLE you are paying for the privilege.

Smallest Unit: If you want small and unobtrusive with minimal features, the KICKASS does the job – at a price. The KICKASS lacks many features of the competitors making it a hard sell, but it might work well on stored batteries where some of the other features are not important. The Doc replaced his KICKASS units with the BLE.

Limitations

Battery types

These battery monitors work on a single battery commonly used in 4X4s, caravans and RVs like SLA, GEL, AGM and Lead Crystal. The Doc has three monitors attached to three batteries (one SLA and two AGM).

The article does not apply to Lithium batteries because of their different chemistry and flat voltage curve. 12-volt Lithium batteries used in a 4X4, caravan or RV should have a battery management system to maximise battery life, not a simple battery monitor. Lithium batteries offer many options exceeding 200 mAh in capacity (the maximum capacity of the units).

200mAh max capacity

Most of the units reviewed max out at 200mAh battery capacity: it is likely batteries in parallel will exceed that figure. Even if the units can be attached to battery banks over 200mAh, there may be concerns around the accuracy of the readings.

The state of charge is estimate only

The state of charge figure from these battery monitors is an estimate only, based on voltage. These simple battery monitors do not monitor the energy going in or out of the battery like the commercial grade systems. They will not tell you how long the battery will last before a recharge is needed based on the current discharge rate. The intermediate commercial grade monitors (costing around $300) can handle a capacity 600mAh or even 800mAh.

These battery monitors can report the battery is at 100% capacity when the battery is still accepting a charge. With auxiliary batteries if you know the charge profile of your DC to DC charger you can use the voltage to work out whether the battery is really 100% charged. Many DC to DC chargers use a higher voltage for charging than maintenance. The BMPRO MiniBoostPro charges an AGM battery at 14.4 volts but maintains at 13.6 volts (a REDARC 1225D/1240D/1250D charges up to 14.6 volts and maintains at 13.3). So, if the unit reports the voltage over 14 volts the battery is still accepting a charge, even if the unit reports it is at 100% of capacity. These charge rates can vary between charger brands and battery chemistries, check your charger’s manual.

Cannot monitor usage

These battery monitors do not monitor movement of energy in and out of your battery. They cannot tell you how long the battery will last at current usage rates. That is one reason commercial systems cost you big dollars, they can accurately estimate the time.

Monitors cannot make concurrent connections

All tested units will only connect to one Bluetooth device at a time. If the unit is connected to Phone A it cannot simultaneously connect to Tablet B. You must disconnect A before connecting to B.

Money well spent

Despite these limitations, cheap battery monitors report a wealth of information about battery health which helps you be proactive on battery maintenance, extending the life of your expensive batteries. A $30 unit that allows you to get an extra year out of a $300 to $400 battery is a great investment. For the weekend warrior over draining your AGM battery is probably the No. 1 cause of premature battery death, these cheap units can help you stop this costly mistake.

EDIT: Cresta Battery Sense

The Kogan Cresta Battery Sense costs $80. The Doc thinks the hardware is the same as the BLE, but in a different plastic case. The app seems different but the functionality of the unit and the app is almost identical to that of the BLE. It cannot be a coincidence (crank test, alternator test, trip reporting, etc.). Only the power consumption is a bit higher on the Cresta compared to the BLE.

The Doc has been testing cheap battery monitors (full review now posted here). They attach to a 12-volt car battery and connect, via Bluetooth, to your phone or tablet. The better units store data and update your app when connected, so you have data over the whole day, not just when you are connected.

Commercial versions exist for 4X4s, caravans and RVs and can cost thousands of dollars, even cheaper units can cost several hundred dollars. They are made by REDARC, BMPRO, Enerdrive, Victron, etc.

For $33 you can get good functionality from the BLE Battery Monitor and your phone or tablet. OK the expensive systems are better quality and can offer more features, but if all you need is voltage monitoring (up to 30 days), graphing, warning alerts, battery charge testing and cracking tests the BLE Battery Monitor does the job for a fraction of the cost.

The Doc tested the BLE Battery Monitor, the CTEK Battery Sense and the Kickass Battery Guard. The BLE Battery Monitor won hands down, it was the cheapest, had the most features, was reliable and the app had less bugs than the other two. The Doc bought the BLE Battery Monitor on eBay here.