## Range question

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• Today I made a 27-mile trip in my Force using 35 amp-hours (13.5 miles each way). Arriving home I noticed that even though I d started with a full charge, the
Message 1 of 5 , Feb 4, 2001
Today I made a 27-mile trip in my Force using 35 amp-hours (13.5 miles
each way). Arriving home I noticed that even though I'd started with a
full charge, the car had lost much of its power and was unable to
maintain speed on the last two hills. I was frankly surprised -- my
batteries are brand new Interstate SRM-27's, which I believe hold 80
amp-hours; why am I losing power after only 35? The effective range of
the car appears to be less than 30 miles, despite the new batteries.

I live in Massachusetts, and the temperature was about 30 degrees
today. I had to leave the car outside at my destination for about 8
hours; could that have had something to do with it?

This was not highway driving, incidentally; I did the whole trip on
city streets, never exceeding 40 mph the whole way.

Another factor to consider is that my charger is behaving strangely;
if left running it will charge the car to about +2 amp hours and then
stop. If unplugged and allowed to sit for an hour or so, then plugged
in again, it will charge the car to about -2. The manual says I should
charge to -4, but I can't easily get the charger to do that. It's a
Solectria BC-1000, by the way, and the car is a 1992 Force (that is to
say, it was built from a 1992 Geo Metro and the manual supplied with
it is for a 1992 Force).

Any ideas?

Rob Landry
umarc@...
• ... You have part of the answer already -- cold temperature. Batteries like it at about 80 deg F, and lose capacity with each degree below that point. (I
Message 2 of 5 , Feb 4, 2001
On 5 Feb 2001, at 5:52, umarc@... wrote:

> I was frankly surprised -- my
> batteries are brand new Interstate SRM-27's, which I believe hold 80
> amp-hours; why am I losing power after only 35? The effective range of the
> car appears to be less than 30 miles, despite the new batteries.

You have part of the answer already -- cold temperature. Batteries like
it at about 80 deg F, and lose capacity with each degree below that
point. (I used to have the formula, but I've forgotten it.)

The second part is a reality of batteries. That amp-hour rating you
quote is the 20-hour rate -- meaning that your 80 amp hour batteries will
deliver 80 amp hours only when those amp hours are withdrawn over a
period of 20 hours (that is, at 4 amps). This is much less than the
current you use when driving. The higher the current, the fewer the amp-
hours you can use before the battery is effectively discharged. (And
that amp-hour capacity is most likely rated at 80 deg F, too.)

To get a better idea of how much capacity you ~really~ have, look at the
battery's 75 amp reserve capacity. It will usually be rated in minutes.
You may have to contact Interstate to get it, though, because published
specs for marine batteries are usually at the 25-amp rate, a bit low for
realistic ratings in EV use.

A typical good-quality marine battery, the Trojan 27TMH, is rated 51
minutes at 75 amps (60/51*75 = 64 amp hours). The East Penn 8G27, which
Solectria recommends (or at least did last time I spoke with them) has
even lower reserve capacity, 40 minutes at 75 amps (50 amp hours).

Finally, remember that your range is set by the weakest battery in the
pack. When it goes dead, its high internal resistance drags down the
voltage (and it can be damaged by cell reversal). So if you have even
one battery that isn't 100% up to par, even though it's new, that will

To fix your range problem, I would start by trying to keep the batteries
warm. Fit the battery boxes with as much styrofoam insulation as you can
squeeze in around them. This will help retain heat of driving and
charging. If that's not enough, you might want to buy Solectria's
battery thermal management system (or make your own).

You should be able to get 40-50 miles of range in moderately warm
weather, but I'm not surprised that you're getting only 30 or so at 30
deg F. At that temperature, that's actually not bad.

> Another factor to consider is that my charger is behaving strangely;
> if left running it will charge the car to about +2 amp hours and then
> stop. If unplugged and allowed to sit for an hour or so, then plugged
> in again, it will charge the car to about -2.

Your Interstate batteries are flooded type, no? Your charger may be set
up for gel batteries. They are normally charged to a lower finish
voltage than flooded types. You may need to send the charger to
Solectria to be reprogrammed.

David Roden - Akron, Ohio, USA
1991 Solectria Force 144vac
1991 Ford Escort Green/EV 128vdc
1979 General Engines ElectroPed 24vdc
1974 Honda Civic EV 96vdc
1970 GE Elec-trak E15 36vdc
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• Original message fragment: I live in Massachusetts, and the temperature was about 30 degrees today. I had to leave the car outside at my destination for about
Message 3 of 5 , Feb 5, 2001
Original message fragment:
I live in Massachusetts, and the temperature was about 30 degrees today. I
had to leave the car outside at my destination for about 8 hours; could that
have had something to do with it?

----------
My response:
Couple thoughts about temperature. The batteries generate heat as they
discharge, and as they charge. As they get older, they generate more than
when they were new. Outside certain temperatures (high or low) you need to
treat them carefully, including leaving them alone until they get back
inside specifications. I replaced the charger in my '92 Force with a Zivan
NG3, which has an optional temperature probe. It modifies the voltage as
temperature changes, and shuts off charging if the temperature exceeds 120
degrees Fahrenheit.

I bought a couple indoor/outdoor digital thermometers, and placed the
"outdoor" probes on the flooded cell batteries - one for the front 4, and
one for the back 8 - and put the displays on the carpet in front of the
emergency brake. I made a pocket with tape and stuck it on one of the
interior batteries in each pack - I put the charger's temperature probe in
the back pocket. As my batteries have matured, they don't have much trouble
staying between 80 and 100 degrees, even when it's cold. When they were
younger, I used the 1/2" insulation that is designed to go under sleeping
bags. It is cheap, and easy to cut to size.

My point, temperature measurement is cheap, batteries are expensive, measure
the temperature and treat your batteries accordingly, especially if your
charger does not automatically compensate for temperature.

Matt Tracy
• Sounds like your battery pack cooled off in those 8 hours and lost a normal amount of capacity for that temperature. ...
Message 4 of 5 , Feb 5, 2001
Sounds like your battery pack cooled off in those 8 hours and lost a
normal amount of capacity for that temperature.

On Mon, 05 Feb 2001 05:52:20 -0000 umarc@... writes:
> Today I made a 27-mile trip in my Force using 35 amp-hours (13.5
> miles
> each way). Arriving home I noticed that even though I'd started with
> a
> full charge, the car had lost much of its power and was unable to
> maintain speed on the last two hills. I was frankly surprised -- my
> batteries are brand new Interstate SRM-27's, which I believe hold 80
> amp-hours; why am I losing power after only 35? The effective range
> of
> the car appears to be less than 30 miles, despite the new batteries.
>
> I live in Massachusetts, and the temperature was about 30 degrees
> today. I had to leave the car outside at my destination for about 8
> hours; could that have had something to do with it?
>
> This was not highway driving, incidentally; I did the whole trip on
> city streets, never exceeding 40 mph the whole way.
>
> Another factor to consider is that my charger is behaving strangely;
> if left running it will charge the car to about +2 amp hours and
> then
> stop. If unplugged and allowed to sit for an hour or so, then
> plugged
> in again, it will charge the car to about -2. The manual says I
> should
> charge to -4, but I can't easily get the charger to do that. It's a
> Solectria BC-1000, by the way, and the car is a 1992 Force (that is
> to
> say, it was built from a 1992 Geo Metro and the manual supplied with
> it is for a 1992 Force).
>
> Any ideas?
>
> Rob Landry
> umarc@...
>
>
>
>
> To unsubscribe from this group, send an email to:
> force_ev-unsubscribe@egroups.com
>
>
>

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• Sounds like your battery pack cooled off in those 8 hours and lost a normal amount of capacity for that temperature. ...
Message 5 of 5 , Feb 5, 2001
Sounds like your battery pack cooled off in those 8 hours and lost a
normal amount of capacity for that temperature.

On Mon, 05 Feb 2001 05:52:20 -0000 umarc@... writes:
> Today I made a 27-mile trip in my Force using 35 amp-hours (13.5
> miles
> each way). Arriving home I noticed that even though I'd started with
> a
> full charge, the car had lost much of its power and was unable to
> maintain speed on the last two hills. I was frankly surprised -- my
> batteries are brand new Interstate SRM-27's, which I believe hold 80
> amp-hours; why am I losing power after only 35? The effective range
> of
> the car appears to be less than 30 miles, despite the new batteries.
>
> I live in Massachusetts, and the temperature was about 30 degrees
> today. I had to leave the car outside at my destination for about 8
> hours; could that have had something to do with it?
>
> This was not highway driving, incidentally; I did the whole trip on
> city streets, never exceeding 40 mph the whole way.
>
> Another factor to consider is that my charger is behaving strangely;
> if left running it will charge the car to about +2 amp hours and
> then
> stop. If unplugged and allowed to sit for an hour or so, then
> plugged
> in again, it will charge the car to about -2. The manual says I
> should
> charge to -4, but I can't easily get the charger to do that. It's a
> Solectria BC-1000, by the way, and the car is a 1992 Force (that is
> to
> say, it was built from a 1992 Geo Metro and the manual supplied with
> it is for a 1992 Force).
>
> Any ideas?
>
> Rob Landry
> umarc@...
>
>
>