how does a hydraulic battery work?

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leon.park@gmail.com - 11 Apr 2006 09:41 GMT

I guess the F-150 2008 will have one, power tools have them. I I can't
seem to be able to find a diagram or something that shows how they
work. It just doesn't seem feasible to me.
http://www.treehugger.com/files/2006/02/60_mpg_ford_f15.php

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C. E. White - 11 Apr 2006 12:37 GMT

> I guess the F-150 2008 will have one, power tools have them. I I can't
> seem to be able to find a diagram or something that shows how they
> work. It just doesn't seem feasible to me.
> http://www.treehugger.com/files/2006/02/60_mpg_ford_f15.php

You have an accumulator - more or less a pressurized tank. When braking a
hydraulic pump adds fluid under pressure to the tank. You recover the energy
by running the high pressure fluid through a hydraulic motor (which could be
the pump running in reverse).

Ed

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leon.park@gmail.com - 11 Apr 2006 13:22 GMT

I just don't understand how you would store energy in something that
doesn't compress. It would make sense if it were a pneumatic battery,
but I can't understand how a hydraulic battery would work

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Happy Traveler - 11 Apr 2006 13:58 GMT

'Hydraulic' accumulators compress gas (typically nitrogen), not hydraulic
fluid.

> I just don't understand how you would store energy in something that
> doesn't compress. It would make sense if it were a pneumatic battery,
> but I can't understand how a hydraulic battery would work

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C. E. White - 11 Apr 2006 16:19 GMT

OK, I was too simple. They have an accumulator like in an automatic
transmission (sort of). You have a piston, or membrane separating the fluid
from the gas. The gas side is pre-pressurized. As you pump in fluid into the
liquid side, the liquid side expands and the gas on the other side of the
divide (membrane or piston) is compressed further. The pressure from the gas
side pressurizes the liquid (hydraulic fluid). You can release the
pressurized fluid to drive a pump. Instead of pressurized gas, you can also
use a mechanical spring, but this give you less storage capacity.

Have you ever seen one of the "water rockets" kids can buy (see
http://www.cas.unt.edu/~klittler/demo_room/mech_demos/1N22_20.html )? They
use pressurized gas over a liquid to propel the rocket. Just imagine the
same set-up except that the rocket exhaust is used to drive a pump or
turbine. In an automotive application you need a membrane or piston to
seperate the fluid from the gas, but the principal is the same.

Ed

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leon.park@gmail.com - 12 Apr 2006 03:23 GMT

ah, that sounds just like those water tanks that store filtered water;
I got one in a reverse osmosis undercounter unit for the kitchen.

I see now. The name was driving me nuts.

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