New consulting relationship with GreenTecAuto begins
What actually goes wrong with the batteries????
A look at todays Hybrid and EV battery packs
Battery packs exposed
2006 and up civic packs
Lead acid battery failure examined
Testing the sticks at the cell level
MaxIMA stick full discharge
Bumblebee battery replacements for the stock subpacks
Inside the cells
Seprating the cells for reuse
How it is wired
PTC strips exposed
The PTC thermistors
Battery current sensor
Inside the 100A semiconductor battery pack fuse
Did it again for the last time
A bad Prius subpack explored and fixed????
Rebalancing the Insight battery?
Insight battery
Insight Battery switching/current monitoring
The battery controller
Prius battery pack
State Of Charge (SOC) determination with NIMH batteries
Battery pack monitoring
What happens to a Prius subpack when you overcharge it?
Keeping Warm In New England
Plugging into the SUN
Making a small solar concentrator
Building MIMA and the plug in adapters
Converting a telephone truck to electric
DIY dual pulse Capacitor Discharge Spotwelder
Chevy Bolt EV joins the family
Getting in shape while making electricity
Replacing gasoline with solar electric lawn equipment
What is Genesis One?
How to stop the aging process DIY
MIMA Install Day 2005 a Big Success!
Building a hybrid car grid charger
Tapping into the Wind
Expanding MIMA with the Distribution board ( users projects )

Battery pack monitoring

Battery pack monitoring
Battery pack monitoring system
Back in 2001 when I first started being active in the Insight on line community, I was concerned about the life of the battery pack, especially the issue of recalibrations. Our understanding of the reasons for the "recals" have not advanced much since then.
I designed a battery monitoring system that used relays for isolation to read each of the 14.4v monitoring points in the pack. The connection to the pack was accomplished with a special spring loaded back probe that just clipped onto the battery. A Labview based data acquisition card and software scanned the taps and recorded the voltage graphically.
I fully expected that my pack would eventually start having the recal issue and wanted to be ready. I am now nearly at 100K on my car, and still have not experienced a single recal. Honda says that gradually accumulating errors in the coulomb counting SOC software is the reason that recal's happen, but I ask what causes the errors? My intuition says that one cell in a subpack is of lower capacity, and since the pack is one long 120 cell series string, that one cell will cause the whole pack to have less capacity than the system expects. When the BCM senses the weak cell dropping voltage as it becomes depleted, the system stops assisting and starts charging to prevent the cell from becoming reverse charged which is instant death. A smart system would have the ability to balance the pack by charging that cell more than the others. Unfortunately since the cell is in a 6 cell subpack, that is not possible with either the Honda or Toyota systems.