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Discussion Starter #1
The law of reality states 3 properties:

1. You can have it inexpensively (cheap).
2. You can have it quickly.
3. You can have high-quality.

The reality is that you ever get to have only 2 of these at any given time:

1. You can have it fast and cheap, but the quality's going to suck.
2. You can have it cheap and high-quality, provided you are prepared to wait
forever.
3. Finally, you can have it both high-quality and quickly, only if you spend
a LOT.

-Phil
----- Original Message -----
From: "Lee Hart" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Sunday, October 14, 2007 2:41 AM
Subject: Re: [EVDL] adding range to existing pack


> From: Michael Mohlere
>> If I wanted to add some range to my EV... what is the
>> best/easiest/cheapest way to do same?
>
> Best, easiest, and cheapest are probably three different solutions. Pick
> one! :)
>
> Before looking at the battery pack itself, I'd start by finding out if
> there are any simple little things that are limiting your range. Things
> like soft or high rolling resistance tires, dragging brakes, bad wheel
> alignment, hot connections or wiring, etc. Fixing these could easily add
> 10-20% to your range.
>
> Next, consider your driving style. Do you accelerate quickly and drive
> fast (drag race to the next stop light)? Are you shifting to run the motor
> at too low an RPM, so the motor and controller are getting hot? Do you
> drive until you are almost up to a stop sign, and then brake heavily?
> These are all bad for range. Changing your driving habits can easily add
> another 10-20% to your range.
>
> Is your present battery pack in good shape? Are they well balanced (all at
> about the same voltage after a long drive)? Are there any weak ones that
> are limiting your range? If a battery is weak enough, removing it from the
> string will actually *increase* your range.
>
> Are the batteries cold? Sometimes, all it takes to increase range is to
> add a heater to keep them around 80 deg.F.
>
> Once you've gotten through all these "cheap / easy" improvements, then
> it's time to consider more expensive and elaborate ways to increase range.
>
>> I have read a lot about "buddy pairs", but I was thinking more
>> on the lines of creating another 120 volt pack with some smaller
>> batteries...
>
> The best solution is probably to have a single pack that meets your range
> and performance needs. Buddy packs and twin strings are "work-around"
> measures to avoid special case problems, such as the batteries you need
> weren't available or affordable, or didn't fit.
>
> If you want to try a hybrid battery pack with two different strings of
> batteries, I think in general you should include some kind of charge
> controller to control/limit how much current comes from each pack. This
> charge controller will also need to manage charging, so each pack is
> charged correctly.
>
> Just like motor controllers, this charge controller could be as simple as
> a set of contactors, or as complex as a full-blown motor controller.
> Luckily, it doesn't have to handle nearly as much power as the motor
> controller, and so can be smaller. It is only being asked to move power
> across a fairly small and limited voltage range, and can be sized for the
> average power rather than the peak power.
>
> As a simple example, suppose your present system has ten 12v batteries; a
> 120v pack, controller, and motor. You could add an 11th 12v battery,
> 12v-to-120vac inverter, and simple battery charger. Let's say this new 12v
> battery is rated at 30 amphours at the 1-hour rate. Then you need a 360
> watt inverter. Setup your charger to draw 12v at 30a, to produce 120v at
> about 2.5a (due to inverter and efficiency). You've added not quite 11/10
> = 10% to your range.
>
> The principle can be expanded to larger 2nd packs.
>
> --
> "Excellence does not require perfection." -- Henry James
> --
> Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart-at-earthlink.net
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
 

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Registered
Joined
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70 Posts
Discussion Starter #2
Or more concisely:

Cost, Quality and Schedule...Pick two :)

> -----Original Message-----
> From: [email protected] [mailto:[email protected]]On
> Behalf Of =A4Phil=A4
> Sent: Saturday, October 13, 2007 1:59 PM
> To: Electric Vehicle Discussion List
> Subject: [EVDL] The Law of Reality (was: adding range to existing pack)
>
>
> The law of reality states 3 properties:
>
> 1. You can have it inexpensively (cheap).
> 2. You can have it quickly.
> 3. You can have high-quality.
>
> The reality is that you ever get to have only 2 of these at any given tim=
e:
>
> 1. You can have it fast and cheap, but the quality's going to suck.
> 2. You can have it cheap and high-quality, provided you are prepared to w=
ait
> forever.
> 3. Finally, you can have it both high-quality and quickly, only if you sp=
end
> a LOT.
>
> -Phil
> ----- Original Message -----
> From: "Lee Hart" <[email protected]>
> To: "Electric Vehicle Discussion List" <[email protected]>
> Sent: Sunday, October 14, 2007 2:41 AM
> Subject: Re: [EVDL] adding range to existing pack
>
>
> > From: Michael Mohlere
> >> If I wanted to add some range to my EV... what is the
> >> best/easiest/cheapest way to do same?
> >
> > Best, easiest, and cheapest are probably three different solutions. Pick
> > one! :)
> >
> > Before looking at the battery pack itself, I'd start by finding out if
> > there are any simple little things that are limiting your range. Things
> > like soft or high rolling resistance tires, dragging brakes, bad wheel
> > alignment, hot connections or wiring, etc. Fixing these could easily add
> > 10-20% to your range.
> >
> > Next, consider your driving style. Do you accelerate quickly and drive
> > fast (drag race to the next stop light)? Are you shifting to run the mo=
tor
> > at too low an RPM, so the motor and controller are getting hot? Do you
> > drive until you are almost up to a stop sign, and then brake heavily?
> > These are all bad for range. Changing your driving habits can easily add
> > another 10-20% to your range.
> >
> > Is your present battery pack in good shape? Are they well balanced (all=
at
> > about the same voltage after a long drive)? Are there any weak ones that
> > are limiting your range? If a battery is weak enough, removing it from =
the
> > string will actually *increase* your range.
> >
> > Are the batteries cold? Sometimes, all it takes to increase range is to
> > add a heater to keep them around 80 deg.F.
> >
> > Once you've gotten through all these "cheap / easy" improvements, then
> > it's time to consider more expensive and elaborate ways to increase ran=
ge.
> >
> >> I have read a lot about "buddy pairs", but I was thinking more
> >> on the lines of creating another 120 volt pack with some smaller
> >> batteries...
> >
> > The best solution is probably to have a single pack that meets your ran=
ge
> > and performance needs. Buddy packs and twin strings are "work-around"
> > measures to avoid special case problems, such as the batteries you need
> > weren't available or affordable, or didn't fit.
> >
> > If you want to try a hybrid battery pack with two different strings of
> > batteries, I think in general you should include some kind of charge
> > controller to control/limit how much current comes from each pack. This
> > charge controller will also need to manage charging, so each pack is
> > charged correctly.
> >
> > Just like motor controllers, this charge controller could be as simple =
as
> > a set of contactors, or as complex as a full-blown motor controller.
> > Luckily, it doesn't have to handle nearly as much power as the motor
> > controller, and so can be smaller. It is only being asked to move power
> > across a fairly small and limited voltage range, and can be sized for t=
he
> > average power rather than the peak power.
> >
> > As a simple example, suppose your present system has ten 12v batteries;=
a
> > 120v pack, controller, and motor. You could add an 11th 12v battery,
> > 12v-to-120vac inverter, and simple battery charger. Let's say this new =
12v
> > battery is rated at 30 amphours at the 1-hour rate. Then you need a 360
> > watt inverter. Setup your charger to draw 12v at 30a, to produce 120v at
> > about 2.5a (due to inverter and efficiency). You've added not quite 11/=
10
> > =3D 10% to your range.
> >
> > The principle can be expanded to larger 2nd packs.
> >
> > --
> > "Excellence does not require perfection." -- Henry James
> > --
> > Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart-at-earthlink.net
> >
> > _______________________________________________
> > For subscription options, see
> > http://lists.sjsu.edu/mailman/listinfo/ev
> >
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>

_______________________________________________
For subscription options, see
http://lists.sjsu.edu/mailman/listinfo/ev
 
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