Any way to read Li-ion charge level while charging?

I have a project that requires me to be able to read the Li-ion charge level while the PiP is charging. I've got a OBD-II ScanTool arriving this week; but I'm not sure if I can get any information off the OBD-II interface while the car is charging?

Is there any information readable from the OBD-II while the PiP is off?

If not; is there another safe sensor point I could read this data from?

 

Sorry; I should have been more clear. I need an automated way to read the charge level.

Ugh...that's what I was afraid of. And no way to leave the car on while charging obviously.

I guess if the button press John mentioned allows me to get a quick ODB-II read...I could have a robot in the car push the button every 5 minutes or something. Wearing out my power button sounds like an expensive issue though ;-)

Maybe I'll have to find someplace I can wire in a sensor.

If it helps; the project is to build a computer into my open source charging station to allow me to set the max charge level to say 95% before it cuts off. This will save me a LOT of gas each month, as I live on the top of a hill. Currently I'm burning about 1 gallon of gas every 150 miles on the warm up the engine does when it is fully charged and going down the hill (no place to put the energy).

Living on top of a hill | PriusChat

 

Wow, that is a GREAT idea! Thank you!

 

I've been doing this some -- and it does seem to work. There are two problems though:

1) It uses up more brakes down the big hill -- which is the big opportunity for regen braking -- so will probably be more expensive than using the gas in brake repairs.
2) Having difficulty with the WAF (Wife Acceptance Factor). She wants it to be easier than switching into N and back and forth to D on the hill in traffic (it's stops every block for 6 blocks on the hill).

 

Doesn't really work when the car begins it's charge at a random state of charge. I really have no idea how long each charge will take. I guess I could try to guess based on the SOC reading...I may experiment with this to see how accurate I could be. The trick is that I really want no less or no more than the optimal amount (95% .... Possibly more after testing of hill charge).

 

Maybe a low cost solution would just be some sort of alarm that goes off when the amps drop...and I could run down and unplug. Hmm...

 

This was exactly what I was thinking. I haven't started buying parts for my own openevse yet, but was planning on doing so soon. This feature (partial charge) would be an important one to build into my system. Building it into an openevse is probably the most cost effective approach as well.

I'm going to dig for that "difficulties of accurately reading SoC" discussion. It's too bad the J1772 standard didn't include some pins to send back the SoC whenever the cars periodically check. It seems like all cars must do this; and it would be useful information to have at the charge point for a variety of purposes.

I'm also considering replacing the LCD board with a Raspberry Pi so that I could have an internet enabled openevse; but I'm not sure if this is going to be overly ambitious. The $25 Raspberry Pi model A supports i2c and costs about the same as the LCD parts; I believe. I don't need a screen on my openevse box, but would like to be able to monitor from an iPhone or computer.