Voltage discrepancy

[Conradconrad]

Does anyone know why the “battery pack voltage” in the alltrax computer app vs battery pack voltage measured at the battery pack would be different? For example in the program it showed 43.5V and using a Fluke 115 the battery pack measured 44.18v ?

Anyone reading this I have 7 batteries 6v each

[DaveTM]

Not unusual. Your reading on the 'puter is coming across the computer "hook up" wiring and into the computer. The voltage is losing some steam in the measurement because of the wiring method used to measure it.

Your Multimeter has short fatter wires to obtain the measurement.

I have a digital display AND a ZEVA monitor that show voltage. The digital display is always .5V less than the monitor.

[cgtech]

Originally Posted by DaveTM

Not unusual. Your reading on the 'puter is coming across the computer "hook up" wiring and into the computer. The voltage is losing some steam in the measurement because of the wiring method used to measure it.

Your Multimeter has short fatter wires to obtain the measurement.

I have a digital display AND a ZEVA monitor that show voltage. The digital display is always .5V less than the monitor.

No mention of power having to go through the pre-charge resistor? Just voodoo about the USB cable being unable to carry a proper serial connection, with pixies getting mixed up on the way?

[DaveTM]

Originally Posted by cgtech

No mention of power having to go through the pre-charge resistor? Just voodoo about the USB cable being unable to carry a proper serial connection, with pixies getting mixed up on the way?

Now you know I'm not an engineer. It appears he has the same "issue" that I have with my digital in dash meter always showing less V than my ZEVA monitor.

If it's more than just that.....then 'splaining it to the OP may be in order.

And it may be Voodoo.....but darn it!!...It's my vooDoo!!!

[JohnnieB]

Originally Posted by Conradconrad

Does anyone know why the “battery pack voltage” in the alltrax computer app vs battery pack voltage measured at the battery pack would be different? For example in the program it showed 43.5V and using a Fluke 115 the battery pack measured 44.18v ?

Anyone reading this I have 7 batteries 6v each

If the solenoid contacts are open, the voltage at the controller's B+ terminal will be a few volts less than the voltage at the battery pack's main positive terminal due to the voltage drop of the pre-charge resistor.

When the solenoid contacts are closed, the voltage at the controller's B+ terminal (which is actually the charge on the filter capacitors) will be equal to the voltage on the battery pack's main positive terminal, less any voltage drops due to the resistance in the two high current cable between the battery pack and controller, their connections and the solenoid contacts.

Also, the voltage measuring network in the controller may read slightly different than the voltage measuring network in your handheld DVM. (This difference can be seen by measuring between the B+ and B- terminals on the controller with your handheld DVM while viewing the monitor screen in Toolkit.

My dash mounted battery meter is connected directly to my battery pack terminals and reads about 0.3V lower than what my handheld DVMs measure at the same points, so I just add 0.3V to whatever it reads.

When analyzing data logs, I use the highest battery voltage recorded on the first few lines after the "Relay Status" (solenoid) becomes a "1" as the starting voltage for the battery pack.

[DaveTM]

I double checked my reading differences when I just jumped on the cart to dump some pumpkins over-da-hill. I get .1 to .2 difference in readings.