Read out individual battery voltages with a microcontroller

[pvancorenland]

Has anyone built/thought of a system to read the individual battery voltages with a micro so you can display them while driving?

I have a very cheap microcontroller board with 8 ADCs, so it should be fairly cheap to read out the voltages, but I would like to convert them in the 0-5V range in an elegant way.

I read some other posts, but I couldn't find an off-the-shelf solution.

Things I am concerned about are:

-) Is it true that when you're charging the batteries, the negative terminal is connected to the neutral wire af the Charger power supply (110V)?

-) What are the largest battery voltages you can expect across the whole pack, such that if I scale them, I can make sure you don't exceed 5V

-) Is anyone aware of an existing solution I can look at?

-) Does it make sense to look at individual voltages when you're driving or does it only make sense to do so when you charged the pack and let the voltage settle?

[scottyb]

Since it is individual batteries which ultimately fail in the pack, this would be interesting diagnostic info.... maybe a bit overkill for everyday users?

[pvancorenland]

Nothing is overkill if you can display some nice data about your cart :-)

Would monitoring the individual voltages and their differences be an acceptable substitute for monitoring the water levels?
I could build in an alarm or something that tells me if the voltage in one or more packs is too low or too much different from the others.

[Hotcat]

Originally Posted by pvancorenland

Nothing is overkill if you can display some nice data about your cart :-)

Would monitoring the individual voltages and their differences be an acceptable substitute for monitoring the water levels?
I could build in an alarm or something that tells me if the voltage in one or more packs is too low or too much different from the others.

I'm by all means no expert, but water levels should always be checked on a regular basis, no matter what.

[pvancorenland]

I agree, but I'm more thinking of the same thing you have with Tires on your car.

You should always check their pressure regularly, but if something really goes out of whack, your Tire Pressure Monitoring System will alert you that a tire is very low, hopefully before something worse happens.

[dougmcp]

Originally Posted by pvancorenland

-) Does it make sense to look at individual voltages when you're driving or does it only make sense to do so when you charged the pack and let the voltage settle?

Not to me, because it is a series system, the pack voltage should be your only concern when your driving.
You can wire a single voltmeter to a rotary or push button switch and measure each battery.
As far as electrolyte level in relationship to voltage, the level has nothing to do with voltage, it is possible to have a fully charged battery and the level below the plates. The only way to monitor the level would be to install a corrosion resistant probe in each cell and find some way to monitor 24 inputs. IMO looking in the holes every month seems more cost effective.

[roady89]

Doesn't sound very practical to me. It'll be a wiring mess because you'll have even more connections on each battery. Every connection is another point of failure. Much easier to get out the DVOM.