Two identical voltage testers, 0.1-0.12V difference

I have one of these, bought last year from Ebay:

It works fine, difference between DMM and its readings is around 0.0x volts.

Ordered another one few weeks ago and while it looks the same, its readings are 0.1-0.12 lower on Ni-Mh than first tester.

Any means of fixing this? I guess there isnt one.

Ive taken them both apart - no way to calibrate unlike those cheap LED volt meters for lithium batteries.

This seems to be the only affordable NiMh tester with LCD that allows for quick alkaline and rechargeable battery testing, analog ones are made for alkalines and not for rechargeable NiMh batteries.

Any alternatives?

Post pics of the insides? There might be a way.

I have one of those. It’s supposed to have a resistor load in it to more accurately display voltage. The voltage it shows should be different than a DMM unless yours is adding a load also. Mine does not.

I’m not sure how accurate ANY of these cheapies are. Mine seems to be a lot better than my DMM for simple NiXX testing. Since the resistor seems to be a constant load the readings on button cell are quite low, even when new, but they are quite a bit higher than used so I can use it as a ‘relative scale’.

I suspect your one reading lower is more accurate for testing purposes than the one agreeing with the DMM.

Using a volt meter to test the capacity of a NiMh is not accurate
For instance three cells tested on a high quality DMM and a ZTS tester
Eneloop 1.38volts
Hähnel 1.27 volts
GP 1.27 volts

Tested on a ZTS analyzer/tester:
Eneloop 80% green
Hähnel below 40% yellow
GP 10% red

The GP is the oldest , the Hähnel about 4 years old, eneloop new

exactly, it’s supposed for a quick check. My readings are also very dependent on how much I press on the battery contacts. It’s good thing for recognizing empty Zinc cells as they tent do to show relatively high voltage (1.4-1.5V) on classic DMM even when drained.

Wow, didnt expect that much response for this lil cheapie :D!

Im using these cheapo testers/DMM's exactly as Bergtjie /Milan said - for quick check, I think I have pretty reliable batteries(few Eneloops and bunch of Turnigys and then some GP ReCyko, not sure they are legit tho) to be quite sure about their approximate usability for the task once I test them :).

Bergtjie that load-tester seems like a nice thing, for that accurate measuring of battery power state, pitty its so expensive, Id get one :D!

Flydiver - Im not sure Im reading you correctly - do you imply that cheapo battery tester that shows whole 0.1V lower readings than known good multimeter is the one being more accurate?

Chloe, here are pics of dissembled ones, "good" one thats on par with DMM is on the left where both shown:

Accurate one, top of board

Other side of the board

The one that shows >0.1V lower


Other side of the board

So, what you, electronics wizards can say, can this be re-calibrated?

Looks like there are no pots to turn here :D!

The DMM is likely giving you unloaded voltage > accurate VOLTAGE, but mostly useless for actually measuring anything meaningful on a NiXX battery.
Therefore I……think……the one with the lower reading ‘may’ be the more useful if it is applying a load that is meaningful.

Having said that I completely agree with the folks that say these are simple checkers. They are mostly useful for simply checking yes-no-maybe on batteries and should not be considered accurate.

I haven’t got the electronics chops to comment on the boards. Hope someone does.
I serious doubt you can adjust them, maybe replace components IF you know what you are doing. But, they’ll still have the same limitation.

I got about three of them from FT last year. They seem iffier as the voltage gets higher. I noticed on a 14500 cell that my best DMM shows at 4.17V, it returns a reading of 4.43V.