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Discussion Starter · #1 ·
Re: [EVDL] charging a 48V pack with a 36V charger?

>
> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On
> Behalf Of Darin at- forkenswift.com
> Sent: Friday, October 12, 2007 12:53 PM
> To: [email protected]
> Subject: [EVDL] charging a 48V pack with a 36V charger?
>
>
> Project ForkenSwift currently has 2 chargers available for its 48V pack:
>
>
> - a 36V 20A taper charger with a manually set timer and an ammeter;
> - a 24V 5A taper charger with an automatic voltage-sensing shutoff timer
> (which sometimes doesn't shut off because the old batteries don't quite
> reach the programmed voltage threshold).
>
> I'd like to use the 20A 36V unit, mainly because it's faster. But the
> problem is that according to my extensive calculations, 48 can't be
> evenly
> divided by 36.
>
> I was thinking of splitting the car's pack into 24V strings, then adding
> as
> "placeholders" two old floodies (left over floor sweeper batts the
> forklift
> co. gave us) to make up temporary 36v strings that can be individually
> charged. These two same "placeholder" batteries will be repeatedly
> cooked
> whenever each half of the car's pack is charged. Will this approach
> negatively affect the "good" batteries?
>
> One potential effect I see is the charging current may taper down sooner
> because those placeholder batts will have more resistance than the four
> good
> batts. Is that a serious problem?
>
> Darin


Based on this, and your recent other question(s); I would seriously consider a 72v system.


--
Stay Charged!
Hump
I-5, Blossvale NY

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Discussion Starter · #2 ·
Re: [EVDL] charging a 48V pack with a 36V charger?

Darin,

One suggestion would be to use the 36 volt charger on three batteries,
and the 12 volt dumb charger listed in your EV Album page with a timer
on a fourth 12 volt battery. Other list members can chime in on the
safety issue. I think your chargers need to be of the isolated type, or
you need to disconnect the "two" packs (36 volt and 12 volt) from each
other while charging.

Like Tim replied, if you move to 72 volts, you can parallel 2 strings of
36 volts to charge the batteries, and then run 72 volts in series for
the traction pack.

If you had a long range plan of going to 72 volts, you could use your 24
volt charger now by splitting the pack into 2 X 24 volts. When you move
to 72 volts, you add 12 volts to each string, pop in your 36 volt
charger, 72 volt controller, and presto. In the long run you would want
something quick like heavy switches or contactors to isolate and break
the pack in half and connect to the charger. You may be able to work on
that now, and just insert two more batteries in the proper place later
when upping the voltage.

Alan

-----Original Message-----
From: [email protected] [mailto:[email protected]] On
Behalf Of Darin at- forkenswift.com
Sent: Friday, October 12, 2007 9:53 AM
To: [email protected]
Subject: [EVDL] charging a 48V pack with a 36V charger?


Project ForkenSwift currently has 2 chargers available for its 48V pack:


- a 36V 20A taper charger with a manually set timer and an ammeter;
- a 24V 5A taper charger with an automatic voltage-sensing shutoff timer
(which sometimes doesn't shut off because the old batteries don't quite
reach the programmed voltage threshold).

I'd like to use the 20A 36V unit, mainly because it's faster. But the
problem is that according to my extensive calculations, 48 can't be
evenly
divided by 36.

I was thinking of splitting the car's pack into 24V strings, then adding
as
"placeholders" two old floodies (left over floor sweeper batts the
forklift
co. gave us) to make up temporary 36v strings that can be individually
charged. These two same "placeholder" batteries will be repeatedly
cooked
whenever each half of the car's pack is charged. Will this approach
negatively affect the "good" batteries?

One potential effect I see is the charging current may taper down sooner
because those placeholder batts will have more resistance than the four
good
batts. Is that a serious problem?

Darin
--
View this message in context:
http://www.nabble.com/charging-a-48V-pack-with-a-36V-charger--tf4614190s
25542.html#a13177044
Sent from the Electric Vehicle Discussion List mailing list archive at
Nabble.com.

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Discussion Starter · #3 ·
Re: [EVDL] charging a 48V pack with a 36V charger?

Alan Brinkman wrote:

> Like Tim replied, if you move to 72 volts, you can parallel 2 strings of
> 36 volts to charge the batteries, and then run 72 volts in series for
> the traction pack.

I have actually been watching for a used 72v controller (they come up
once in a while, but a lot less often than the 48v variety). After all,
we've already got the batteries, and as you and Tim pointed out, 72v
would simplify the charging situation.

> If you had a long range plan of going to 72 volts, you could use your 24
> volt charger now by splitting the pack into 2 X 24 volts.

I have been doing this, however @ 5A it takes about 24 hours to
recharge. I was just looking for a workaround that would let me use the
36v charger.

> You may be able to work on
> that now, and just insert two more batteries in the proper place later
> when upping the voltage.

Good advice.

It would mean an addition of 4 batts, though, since we've got 6v
floodies. Currently the car is estimated at 250 lbs over OEM curb
weight, and it's evenly distributed, sitting level (and not excessively
low) on the stock suspension. Four more batteries in the rear (no more
room up front) would also require a spring upgrade (certainly not out of
the question).

Until a beer budget controller comes up, though, just playing around at
48v. Learning a lot & having fun.

Thanks for the advice -
Darin

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Discussion Starter · #4 ·
Re: [EVDL] charging a 48V pack with a 36V charger?

>
> One potential effect I see is the charging current may taper down sooner
> because those placeholder batts will have more resistance than the four good
> batts. Is that a serious problem?
>

no comment on your approach.... but I bought a 48v 10amp charger
from a company called Kipoint in taiwan and including shipping and
customs I paid less than U$200. Its worked perfectly for a couple of
months while I load test the batteries (as you I am trying to recicle
donated batts) and while slow, its on-board-able.

Maybe you can try one. They appear on ebay spain and sometimes in ebay US.


--
Eduardo K. | Darwin pone las reglas.
http://www.carfun.cl | Murphy, la oportunidad.
http://ev.nn.cl |
| Yo.

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Discussion Starter · #5 ·
Re: [EVDL] charging a 48V pack with a 36V charger?

I'm charging a 78vdc pack with a 72volt Schumacher
Charger from NorthernTools. It is selectable from 12,
24, 36, 48, - 72 vdc. I purchased it on sale for $179
from:

http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_340592_340592

Now, as I mentioned before, I'm using the 72vdc
setting to actually charge a 78vdc pack of 6vdc GC
batteries, so far it's working great for me.

M.Barkley
www.texomaev.com
www.nteaa.org



--- Eduardo Kaftanski <[email protected]> wrote:

> >
> > One potential effect I see is the charging current
> may taper down sooner
> > because those placeholder batts will have more
> resistance than the four good
> > batts. Is that a serious problem?
> >
>
> no comment on your approach.... but I bought a 48v
> 10amp charger
> from a company called Kipoint in taiwan and
> including shipping and
> customs I paid less than U$200. Its worked perfectly
> for a couple of
> months while I load test the batteries (as you I am
> trying to recicle
> donated batts) and while slow, its on-board-able.
>
> Maybe you can try one. They appear on ebay spain and
> sometimes in ebay US.
>
>
> --
> Eduardo K. | Darwin pone las reglas.
> http://www.carfun.cl | Murphy, la oportunidad.
> http://ev.nn.cl |
> | Yo.
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>


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