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Discussion Starter #1
Hi folks,

Has anyone worked out the math involved with battery
trailers? Basically, some idea of how much additional power is going
to be required due to the added load?

Thanks,

Mike Chancey,
'88 Civic EV
Kansas City, Missouri
EV Photo Album at: http://evalbum.com
My Electric Car at: http://www.geocities.com/electric_honda
Mid-America EAA chapter at: http://maeaa.org
Join the EV List at: http://www.madkatz.com/ev/evlist.html

In medio stat virtus - Virtue is in the moderate, not the extreme
position. (Horace)

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Discussion Starter #2
Hello Mike,

I have calculated what the range of my EV would be with 2 strings of 30
T-145's for two 180 volt battery packs that would be either all onboard or
in a trailer.

If you use a trailer, then you must add the weight of the trailer and
connections devices. This becomes about 2200 lbs for the batteries and
about 500 lbs for a trailer which is addition 2700 lbs which makes the total
battery pack of 4900 lbs.

I use Uve's Electric Vehicle Calculator which gave me a total weight of 5700
lbs for one string and 8400 lbs for two strings plus additional 500 lb
trailer for a S10 type pickup. The range for a one string of batteries is
about 39 miles at 60 mph at 50% DOD and for the addition battery and trailer
it becomes 65 miles at 60 mph at 50% DOD.

It takes 7 to 10 additional hp and will loss about 10 mph in top speed.

If you leave the standard transmission and differential stock gears in
place, it becomes more worst then this. I am running a modified
transmission and differential that's gives me a starting 19.5:1 gear ratio
and reduces to 5.57:1 in final drive. This is more then double then the
standard gearing.

Roland






----- Original Message -----
From: "Mike Chancey" <[email protected]>
To: <[email protected]>
Sent: Sunday, October 07, 2007 6:25 AM
Subject: [EVDL] Battery Trailer


> Hi folks,
>
> Has anyone worked out the math involved with battery
> trailers? Basically, some idea of how much additional power is going
> to be required due to the added load?
>
> Thanks,
>
> Mike Chancey,
> '88 Civic EV
> Kansas City, Missouri
> EV Photo Album at: http://evalbum.com
> My Electric Car at: http://www.geocities.com/electric_honda
> Mid-America EAA chapter at: http://maeaa.org
> Join the EV List at: http://www.madkatz.com/ev/evlist.html
>
> In medio stat virtus - Virtue is in the moderate, not the extreme
> position. (Horace)
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>

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Discussion Starter #3
Roland's calculations look good, except that I don't see any air drag
calculations.

For a big vehicle like a van or pickup, the trailer should be pulled
along inside the turbulence that's normally created on the vehicle, so
it probably wouldn't add that much to air drag. For a small,
aerodynamic vehicle, it would probably have a much larger effect.

That said, I don't think there's any numbers available that will let
you see what an arbitrary trailer will do to the aerodynamics of an
arbitrary vehicle. The best way to find out would be to hook up the
trailer and do a roll-down test.

-Morgan LaMoore

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Discussion Starter #4
> It takes 7 to 10 additional hp and will loss about 10 mph in top speed.
>
> Roland

Yes, but in the real world your mileage *will* vary. With 2 of my small
rigs, I found a slight increase in range.

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Discussion Starter #5
> That said, I don't think there's any numbers available that will let
> you see what an arbitrary trailer will do to the aerodynamics of an
> arbitrary vehicle. The best way to find out would be to hook up the
> trailer and do a roll-down test.
>
> -Morgan LaMoore

True... and then test it against the same rig w/ that same extra weight
thrown in.

In my case, I used a trailer because the vehicle was not adaptable to all
that extra weight. (It was a no-choice "option", the only choice being
whether to carry extra batts or not.)


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Discussion Starter #7
That's one I hadn't heard before... but makes sense.

No, mine was because I pulled the power off the rig and put it onto a
trailer. The one was a bike.

I never figured out why it happened. I only put the batts in the trailer
because it was more convenient than having the bike fall over all the time.
<g> It *could* have been that I used bigger wiring, or maybe I had a bad
connection when they were on the bike... or maybe because the trailer was in
the air some times? <g> (It had a suspension and would bounce around pretty
good on the bike trails.)
----- Original Message -----
From: "David Nelson" <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Monday, October 08, 2007 7:13 PM
Subject: Re: [EVDL] Battery Trailer


> I know of someone who had a motor home. When they decided to tow a
> small car with them their mileage increased about 2mpg. It had to do
> with breaking up the turbulence behind the motor home and thus
> decreasing drag. Maybe that is what happened with your two rigs.

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Discussion Starter #8
I built a tapered tonnoeu cover for my Ranger a while back it it gave me a +2 mpg increase onto the 20mpg mileage. I wonder if
you built a trailer that picked up the lines on the back of the truck and continued to slope down to complete the wedge what taht
would do to mileage. You'll take a hit with the extra rolling resistance but I suppose you would more than make up for it at
higher speeds.

Mike W.

> -----Original Message-----
> From: [email protected] [mailto:[email protected]]On
> Behalf Of David Nelson
> Sent: Monday, October 08, 2007 6:14 PM
> To: Electric Vehicle Discussion List
> Subject: Re: [EVDL] Battery Trailer
>
>
> I know of someone who had a motor home. When they decided to tow a
> small car with them their mileage increased about 2mpg. It had to do
> with breaking up the turbulence behind the motor home and thus
> decreasing drag. Maybe that is what happened with your two rigs.



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Discussion Starter #9
MIKE WILLMON wrote:
> I wonder if you built a trailer that picked up the lines on the back of
> the truck and continued to slope down to complete the wedge what taht
> would do to mileage.

Food for thought:

DIY aero-modder extraordinaire Phil Knox made an aero trailer to pull behind
his CRX (ICE), and claimed the car's fuel consumption was unaffected when
towing it at highway speeds, despite the added weight & rolling resistance.

He boat-tailed the trailer carefully enough to improve the overall Cd of the
CRX+trailer package vs. the CRX on its own. I guess the aero improvement
more or less equalled the weight+RR penalties.

photo: http://metrompg.com/offsite/crx-trailer.jpg

Darin
--
View this message in context: http://www.nabble.com/Battery-Trailer-tf4583027s25542.html#a13176996
Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.

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