After measuring the capacitance charge of the Hybrid Battery I have noticed that after long distance driving the battery is at about 92% capacity. When leaving the Hybrid parked and only driving short distances 20 miles max (which took a lot for me to do). The battery was at 61% capacity. No question this is going to have an effect on how long you can stay in EV and Hybrid modes. Better battery capacity, better MPG. GM needs to display this feature on the DIC or Nav display.

 

How did you manage to mesure the capacity of the battery ?

 

I took it to my shop and used the Christie Battery Anaylizer we use on corporate jets, such as the Gulfstream.

 

Good info Ken!
Since you're a detail person, lets make sure everyone understands you are referring to battery charge, not capacity.
Capacity changes slowly over time and is the amount of charge the battery can hold. State-of-charge is the amount of energy stored in the battery at any given time. Both of these have the same units. The units are Amp-Hours. The power in the battery is Watt-Hours, which is Amp-Hours times the battery voltage.
So, a 300V battery, that is holding 100Amp-Hours (Ahr) of charge has 30,000Watt-Hours (Whr) of energy in it. If it is a 30kWhr battery, then it is at 100% charge. If it is a 40kWhr battery, then it is at 75% charge. Another way of saying it is "it is at 75% of rated capacity".
Of course, over time, just like your cellphone and laptop batteries, the capacity will degrade.

I'm not usually a detail-freak, but there are a lot of people learning on this forum.

 

Hi, I guess the point I wanted to make here is that the longer distance drives seem to charge the battery for a longer period of time resulting in increased capacity. The shorter the distance of drives the shorter the period of charge resulting in a shorter period of charge resulting in a decrease in capacity. The christy unit is not only able to calculate the capacity of the battery by putting a sustaned load on it, it is also able to see which cells are bad, average, and good. We use it on all battery types including but not limited to Ni-Cad's. It also has charging capacity and continually records battery history. In aviation we are not only required to certifiy battery voltage, but also capacity and state of charge all are very important to battery life. The christy unit is a 200K unit. I have two in my battery shop.

 

I guess the other thing I would like to experiment with when I have time and understand the system better, is what would happen if when the vehical was at rest nighttime etc and we were able to use household power to keep the battery at high capacity, steady state using some form of tricle charger? maybe the battery would require increased capacity?

 

Thanks chung ANC kklien for both explanation. Very informative.

 

Excuse the auto spell fjung sorry about that

 

If we were able to start the day with the battery at maxmium capacity everyday it would be interesting to see what the MPG would be. When a battery is in no state, either being charged or discharged it is always discharging sitting. The Chev Volt will have plug in capability to recharge the battery when not being operated to keep its battery fully charged and at the highest capacity avialable.

 

Thanks Ken. Super info and, more importantly, info from someone who knows what he's talking about and isn't just regurgitating stuff off the internet This is a good explanation for why I can't seem to get the truck to stay in EV mode for very long during my daily (in town) driving. As I've stated elsewhere, I'll probably get 15-17 mpg if I didn't do any freeway driving (which is not quite as advertised by Chevy).

Now this really makes me want to look into a way to plug my Tahoe in at home to "fully" charge it for the next day's driving. Even better, see if someone can design a PV based system to charge our trucks while sitting during the day (no .... not a vehicle mounted one, that's silly )