The first battery was accidentally discovered through a twitching frog leg and the lead-acid battery in your car can still trace its roots back to that 18th century invention by Italian physicist Alessandro Volta in the sense that its still based on the same principle and is still very much 'alive' - Feed and look after it and it'll serve you for many years, neglect it and it'll die a slow and painful death and might even leave you stranded by the roadside.
This blog entry is going to be a quick and dirty and meant to compliment the Bosch C3 Battery Charger review. We'll be using the cheap and cheerful UNI-T UT33C multimeter for this basic how-to but basically just about any multimeter can measure voltage.
The idea behind a cheap multimeter is that you'd just keep the UT33C in your car or toolbox and only use it for the basic stuff that does not require a whole lot of precision measurements. Obviously it goes without saying that the UT33C isn't as accurate as the more expensive multimeters in the market but for a fraction of the price, it's competent enough to cover 90% of all your needs - especially when working with a car - it even comes with a temperature sensor probe - we'll get into that in another blog.
Also, if you're working around batteries on or planning on topping up non-sealed lead-acid batteries, it's advisable to put on some eye and hand protection - a pair of 3M SF201AF SecureFit Protective Eyewear and a pair of 3M Comfort Grip gloves or nitrile gloves should offer adequate protection.
To measure the voltage on your car, all you need is to touch the probes to the battery. Black being negative and red being positive.
The UNI-T UT33C has what's called a manual ranging because there's a manual select dial. Just rotate it from "OFF" (at the 12 o'clock position) to "20" (at the 3 o'clock position). "20" for max of 20V. For one less decimal point, rotate it to to the "200" mark.
Don't worry if you touch the black (negative probe) to the red (positive) battery terminal and vice-versa. Nothing will blow up, you'll only register a negative readout versus a positive readout (just ignore the "-" negative symbol infront of the numbers or swap the probes if it bothers you).
Note: Plug the probes into the UT33C's fused ports; red (positive) in the centre and black on the right side (with the meter facing you). You might also want to use a black permanent marker to mark-out the right side port.
So what are we looking for?
Typically most healthy lead-acid batteries including maintenance-free batteries will register a voltage above 12.6V when new without load. That is with the battery disconnected and engine not running. Sometimes it might read a little bit higher than 12.8V, that's called a surface charge and would dissipate if you let the battery sit overnight.
As the battery wear during normal use, you would start to have sulfur build-up on the plates aka sulphation. Eventually, the voltage would drop to around 12.4V to 12.5V. At this voltage, you would also notice a hesitation during cold starting and/or your headlights would have a warmer colour temperature. It's still possible to have your battery reconditioned (stay tuned for our Bosch C7 review) to restore its performance or alternatively, you might consider getting a new battery.
CT Hardware Toptip: If you're working in lowlight, hit the light blue upper right button (with a bulb icon) and the UT33C's display is backlit! (you don't find may multimeters with this party trick at this price point). Be sure to select "OFF" when done using the multimeter to avoid draining the multimeter's battery.
#cthardware #cthardwaretoptip #twitchingfrogleg #uni-t #ut33c
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