Sterling Power TM24V DC Voltage Probe and Diagnostics Tool - 24V
At first glance this low cost DC voltmeter looks like any other one available, however on closer inspection you will see it is not. Standard voltage probes only go to 14V and are unable to inform you if the advanced charging cycle is in progress or a system has failed and is overcharging your system. The extra 2 LED's are preset to give mire useful information than the very limited standard ones. This is a sterling product and is unavailable to buy elsewhere. Available in both 12V and 24V versions. | 
