[ausev] Air Conditioning in an EV.
Dan Petit
djp at onr.com
Wed Jul 4 17:59:58 GMT 2007
Thanks to Mark and Sean for getting my computer running again.
Air conditioning in an EV utilizing 134a will be tricky when designing a
system from scratch. Sizing the btu's improperly and mismatching
displacements and heat transfer areas and capacities in both condensing
and evaporating can cut an EV's range in half or even pop a breaker.
In my 05 Honda Element, the A/C required service of only 4 ounces of
134a at 18,000 miles. Total capacity is 20.9 ounces. Service procedures
on small capacity systems are extremely exacting. The reason why it
needed servicing is that it is a very high performance system which uses
a relatively small charge.
134a superheats (and goes to overpressure) a lot easier than did R-12
of a decade ago. This occurred on day on my Honda when I wanted to
change lanes from a stop, I turned the steering wheel, (the AC was not
cooling as it normally did), pressed the accelerator, and went
nowhere. Meanwhile, an 18 wheeler was barreling toward me, so I quickly
let off the accelerator, turned the steering back to the lane I was
still in, and let the 18 wheeler truck pass.
The dealer DID NOT have an AC recycle/recovery/recharge machine which
qualtifies (to within a quarter of an ounce charge) the recovered amount
of 134a (as I do), but since it was under warranty, I went back and had
them service it. They just put in more 134a without knowing how much
leaked out.
A friend of mine also has a Honda Element, and, at 18,000 miles on
hers, the same thing happened. The dealer she wanted to take it to did
not want to do anything because they said "it's still blowing cold
[enough]".
I went ahead and recovered the 134a in her system and found that only
4 ounces had leaked out.
Since my system was also under-cooling again at 38,000 miles, I
decided to recover and quantify what had leaked out of my system again.
It was only 4 ounces of 134a. Both Honda's were charged up at 20.75
ounces each and the acceleration performance returned to normal again
(as did the cooling performance).
The lesson here is that the four cylinder engine low-end power curve
tells us that if one is going to install AC in an EV, that regular
service is going to be necessary to prevent superheating of the
refrigerant as it seeps out. The 134a molecule is a fifth of the size
of an R-12, and, experience regarding leakage rates in all makes
suggests clearly that the minimum timing for low-capacity systems for
service is at least every other Summer. For medium capacity systems (32
ounces), it is the third Summer and every other one thereafter.
Manufacturers are being required to design very low capacity systems
(even down to only 10 ounces!). Therefore, not only will it be the law
for anyone getting paid to perform AC work to have an AC
Recovery/Recycle/Recharge machine which conforms to the new Society of
Automotive Engineers standard for weight-scale accuracy to be within a
half-ounce accuracy, but, it also means that a 12 ounce can of r134a
installed into such a system will likely cause a hydrostatic lock up of
such a small system.
Therefore, one can not just expect any system "to last forever",
excepting if it does not let you drive the EV far in the first place.
Dan.
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> Today's Topics:
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> 1. Die-hard Platinum Batteries (tomsmail)
> 2. Re: Die-hard Platinum Batteries (Mark Farver)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 03 Jul 2007 14:39:51 -0600
> From: "tomsmail" <tomsmail at wtez.net>
> Subject: [ausev] Die-hard Platinum Batteries
> To: ausev at austinev.org
> Message-ID: <468ab417.75ed.362681006 at wtez.net>
>
> Hi all you battery experts,
>
> I heard a radio advertisement this morning claiming
> (paraphrase) "Die-Hard Platinum as 40% more capacity than
> spiral wound AGM". And since Sears sells the Optima YTs,
> this could be the comparison they refer to.
>
> What's the scoop on the Die-Hard Platinum batteries? Are
> they solid or liquid electrolyte? Are they better?
>
> Tom
>
>
> ------------------------------
>
> Message: 2
> Date: Tue, 03 Jul 2007 21:14:09 -0500
> From: Mark Farver <mfarver at mindbent.org>
> Subject: Re: [ausev] Die-hard Platinum Batteries
> To: AustinEV News Announcements and General Discussion
> <ausev at austinev.org>
> Message-ID: <468B0271.4000909 at mindbent.org>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> tomsmail wrote:
>
>> I heard a radio advertisement this morning claiming
>> (paraphrase) "Die-Hard Platinum as 40% more capacity than
>> spiral wound AGM". And since Sears sells the Optima YTs,
>> this could be the comparison they refer to.
>>
>> What's the scoop on the Die-Hard Platinum batteries? Are
>> they solid or liquid electrolyte? Are they better?
>>
>>
> Here the thing... almost any new or existing battery on the market is
> going to be useless in an EV.
>
> 1. Its being marketed, which means inflated claims, and questionable
> testing. 2. It has no history. A $60 automotive battery that last 2
> years instead of 3 is unlikely to upset most people. When you are
> dropping $1000-2000 on a new pack of batteries, that extra year is a big
> deal. 3. There are a lot of markets looking for a good battery, if a
> new technology is so great there are plenty of OEMs that would buy it
> and pay more than the automotive market.
>
> EV duty is extremely harsh, drawing large currents, deep discharges and
> needing long cycle life. Many batteries that are acceptable for other
> uses are rapidly destroyed. Yes, you can buy Walmart golf cart
> batteries for half the price of Trojans, and they have a several year
> free replacement warrenty... but they underperform and fail in a matter
> of weeks, and obtaining and installing a new battery every week is not a
> fun thing. (Plus, in most cases the manager will stop giving you
> batteries after a few replacements... there is a lot of fine print in
> the warrenty)
>
> In the case of the Diehard Platinum, a quick Google search shows they
> are being built by EnerSys. Enersys has a good rep in the EV world,
> they currently own the Hawker line of batteries that have done well in
> limited EV use. Hawkers tended to be too small and too expensive for EV
> duty, but they had great power density and were popular with drag racers
> and in high voltage strings. BUT batteries even from the same
> manufacturer vary widely in their suitability... if the DieHards are
> price competitive (I doubt it, since they are probably only available at
> retail price) they _may_ be ok in an EV, only years of real world
> testing can prove that.
>
> Mark
>
>
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> End of AusEV Digest, Vol 18, Issue 1
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