Hi.

I got one of those USB charger plugged into the power outlet/cigarette lighter thingy in my car with voltmeter function. Now before starting the car, the voltmeter shows 12.2V and drops to 11.9V every morning. The car can start just fine, although at times I need to try twice before the engine starts to crank. With the engine on idling, it reads 14V.

My question is, how accurate is the reading? I bought a good quality one ZMI branded.

My car battery is almost 5 years old btw. Probably about time to got it replaced, but I figured that maybe I can delay it for a bit longer.

This post has been edited by Steponlego: Feb 11 2022, 01:05 PM

Im not pro but i dont think its accurate. Want accurate should check direct at the battery terminal.

USB voltmeter are never accurate, you need to use a proper battery tester to get an accurate reading

You are too humble bro., yeap it is not accurate simply because there are resistance in the circuit. Hence it is crucial that readings are measured directly from the source.

BTW what car is that , battery can last up to 5 years? Roman Catholic would love to know.
FYI, I have a voltmeter, similar to your USB charger, except without charger.
It will definitely show lower , at "ACC" (Accessories) key position and even lower on "ON" Position.
If your volt meter shows 12.2V , estimated you should plus 0.2-0.3V = 12.5V.
However you should get a proper multimeter (a cheap one at MR DIY cost only RM 12) to check it out.

not calibrated. possible errata 10% and much more

It's a Century Hyrbid DIN55. Says on the sticker installed on July 2017. Probably only last this long because the car is not a daily drive.

to be accurate it must be direct from battery, tapping via fuse box will have some variable.

but its enough to know if alternator charging or otherwise

i have one unit in each of my car

Got 2 units of different brand on my cars. The unit on my car under-reads voltage by 1.0v all the time. I thought it was defective or something. So plugged it into my weekend car, and hey it is only off by 0.1v, as referenced by my DMM. I guess the 1.0v voltage drop was due to poor dashboard, or was it the ciggy port grounding. Lazy to open lower dashboard to check, so living with it. Can't expect much from a 23yrs old car.

On my wifey car, 2nd unit is off by 1.0v when engine is not started. Once engine is started, it is accurate..... LOL So this case, I dunno if it is due to BCU relay or other things that gave weird reading anomalies.

😊😊😊

Initially I was keen to find out every vehicle that was scoring 5 years in battery life span, then I learnt that is actually dependant on the owners themselves if they really want to learn how to safe on batteries and practice what is taught or just continue with their driving method while hoping for the best.

Here the update on my client's Exora Turbo whose previous battery use to last 8 months. After they stop leaving their car in idle and with the aircon on for their dog, the battery capacity has improved tremendously however there are a few things that I am still unsatisfied about and I have to figure out what is wrong. The only downside to their Exora is that the previous battery resellers had cut off both original terminal and replaced that with after market ones, which I seriously do not like.