Battery sizing and assumptions based on ICE performance

[Jacobsmess]

So, I've been using a few assumptions to base my battery capacity needs on and I'd appreciate some input.

If I drive fast (80-83mph) in my mercedes 310D van, I average around 19m/g (UK gallon) or 4.18 m/L. Obviously if I drop the speed to something more leisurely I can get a much better economy.

So, I've used this basis to work out what sort of energy economy I might expect and then size a battery to meet my minimum range of 100 miles.

I'm looking at putting in around 82kWh of usable battery capacity with two packs running in parallel. This is 295 MJ of energy and the equivalent of around 32L of diesel using an efficiency of 24% of the ICE.

Assuming no inefficiency that gives me 135 miles or 115 miles at 85% efficient.

The big assumption is a 24% efficiency on the ICE (it's an old indirect injection om602 engine). As I understand, around 35% efficiency is a usable figure, but then accounting for other losses in fan, alternator, power steering, water pumps etc. a lower figure would be suitable.

Anyway, any input is appreciated although I suspect the main takeaway will be. No one knows until you try it. Although I'd appreciate any anecdotal data on fuel/energy economy pre and post conversion if anyone has any.

[MattsAwesomeStuff]

Just a sanity check, working at it backwards...

82kwh / 115 miles = 713wh/mile.

That's about double what a car gets. Which, for a van that normally only gets 19mpg (versus a slipperier car that gets 40mpg)... yep.

This is probably within 10%.

[Jacobsmess]

Thanks Matt, best learn to drive more economically!