Voltage Adder for Lithium Battery Monitor

Support
1

I have a iTechworld shunt style monitor in a truck with lithium batteries, but it reads 0.2VDC too low and cannot be adjusted. Supplier believes this is within their tolerance but it makes the “state of charge percentage” inaccurate.

I’m looking for a way that I can boost the voltage input from the batteries to the monitor so that it is more accurate.

2

Hi Des
Welcome
What is your battery voltage? A truck could be 12V or 24V.
If 12V this error is 1.7% and at 24V it is 0.83%. What accuracy are you after. That is not bad and is probably as stated within the device tolerance.

You have not state if the error is just 0.2V across the board or is it a % error which the actual measurement changes depending on what the battery voltage is. This makes a difference to the type of correction needed (if any).

What are you measuring with. Some of this could be measurement error.
Cheers Bob

Add on:
just looking at the book on this device. The claimed accuracy is 1%. Your error is just outside this if 12V.

3

Thanks Robert,

I have a 0.2 v error regardless of the battery voltage of this 12 volt truck. Because the battery monitor includes a state of charge percentage, even a 0.2 volt error is significant. I am measuring with an accurate multimeter as well as a second monitor and also with the vendors multimeter. All show the same error.

Thanks for your help.

Kind regards,

Des Carruthers
0409 667 042

4

Hi Des
Check if the shunt is the correct way around. If it is reversed the shunt is in circuit and instead of measuring directly across the battery any small voltage drop across the shunt would be subtracted from the battery voltage as measured.

I questioned the meter used as there are DMMs and DMMs. They are not the Holy Grail of measurement devices. That is why in the serious world the calibration is checked every 12 months.
But you have 3 devices all showing the same so you would think the measurement is very close to being correct.
Cheers Bob

5

Thanks Robert,

the vendor inspected the installation and agreed everything was the right way around. They even supplied a replacement shunt and meter and (of course!), it read exactly the same.

Kind regards,

Des Carruthers
0409 667 042

6

Hi Des
Well, that’s one thing it’s not. Was just a thought.
Cheers Bob
A bit difficult to see just what is happening remotely. Might take a bit of sleuthing around with your multimeter. Measure across various locations. What you are looking for is 0.2V. There has to be some current to develop this voltage so see if there is any current that should not be there. a DC clamp meter would be useful here.