ev batt. chargers

[Josh and Jenifer]

Can 2 72VDC Chargers be hooked in series to Charge a 144VDC pak?  I ran this topic through the archives,  but i did not come up with what i was looking for.

[Zeke Yewdall]

You wouldn't really run them in series.  You'd just hook each one to a
separate 72 volt subpack of the 144 volt pack, similar to how some
people use separate 12 volt charges for each battery of a 120 or 144
volt string.  You'd need isolated chargers to do this, because the
positive of one pack would be the negative of the other pack.

Z

On Jan 3, 2008 9:47 PM, Josh and Jenifer <[hidden email]> wrote:

>
> Can 2 72VDC Chargers be hooked in series to Charge a 144VDC pak?  I ran this
> topic through the archives,  but i did not come up with what i was looking
> for.
> --
> View this message in context: http://www.nabble.com/ev-batt.-chargers-tp14610840s25542p14610840.html
> Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.
>
> _______________________________________________
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> http://lists.sjsu.edu/mailman/listinfo/ev
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[Morgan LaMoore]

Essentially, yes. If you have isolated chargers, you hook the two
chargers in series, but you ALSO have to connect the place where the
two chargers are connected to the center of your battery pack. From
the charger's perspectives, each is charging its own 72V pack, but
from your perspective, you have two 72V chargers in series charging a
144V pack.

If the two chargers aren't isolated, it's still possible, just
trickier. In order to charge then, you have to disconnect the packs to
form 2 separate 72V packs. You can then connect the top pack to the
charger. While charging, the two packs share a common ground, and
while running, the two packs are in series. The easiest way to do this
is with a Anderson connector for the top 72V pack: you have one
connector that has the B+ and B- of the top half of the pack and two
separate receptacles: one for running that has the controller B+ and
the bottom back B+, and one that has the charger B+ and B- (sharing a
ground with the bottom pack B-).

If your chargers aren't isolated and you aren't clear on my
explanation, just let me know.

-Morgan LaMoore

On Jan 3, 2008 10:47 PM, Josh and Jenifer <[hidden email]> wrote:

>
> Can 2 72VDC Chargers be hooked in series to Charge a 144VDC pak?  I ran this
> topic through the archives,  but i did not come up with what i was looking
> for.
> --
> View this message in context: http://www.nabble.com/ev-batt.-chargers-tp14610840s25542p14610840.html
> Sent from the Electric Vehicle Discussion List mailing list archive at Nabble.com.
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>

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[Jack Knopf]

I disagree. You can hook the chargers in series and only have two output
leads.
I have done this with many types of chargers and it works.
The only type of charger I have found so far that this will not work is the
new smart chargers.
They turn off before they start their next cycle and will not restart when
in series.
But old Telco chargers, marine chargers, any chargers that remain on during
their profile seem to work in series.
Even different marine chargers, one with a manual/automatic switch, I put
the switch in automatic to charge, then manual for a 2 amp equalize at a
higher voltage.
Perfect for Agm's.
Let opinions on this list spark something in your mind and then go out in
the garage and see if it will work.
Never assume that what is said is a confirmed fact.
Jack.

"Knowledge is Certainty in the Real World, Not Data."


----- Original Message -----
From: "Zeke Yewdall" <[hidden email]>
To: "Electric Vehicle Discussion List" <[hidden email]>
Sent: Thursday, January 03, 2008 11:53 PM
Subject: Re: [EVDL] ev batt. chargers

> You wouldn't really run them in series.  You'd just hook each one to a
> separate 72 volt subpack of the 144 volt pack, similar to how some
> people use separate 12 volt charges for each battery of a 120 or 144
> volt string.  You'd need isolated chargers to do this, because the
> positive of one pack would be the negative of the other pack.
>
> Z
>
> On Jan 3, 2008 9:47 PM, Josh and Jenifer <[hidden email]>
> wrote:
>>
>> Can 2 72VDC Chargers be hooked in series to Charge a 144VDC pak?  I ran
>> this
>> topic through the archives,  but i did not come up with what i was
>> looking
>> for.
>> --
>> View this message in context:
>> http://www.nabble.com/ev-batt.-chargers-tp14610840s25542p14610840.html
>> Sent from the Electric Vehicle Discussion List mailing list archive at
>> Nabble.com.
>>
>> _______________________________________________
>> 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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[David Roden-3]

Battery chargers will work in series (without that mid-pack connection) if
they are fully isolated from the mains (transformer type) and dumb, dumb,
dumb.  The smarter they are - that is, the more sophisticated the charge
control is - the less the chance this will work properly.  I would be
surprised if any but 100% manual chargers could be used this way.

Nor do I see much reason to try.  Perhaps I'm missing something, but I can't
see what you'd gain by connecting two chargers in series across the entire
pack vs. splitting the pack, other than perhaps slightly simpler wiring
between battery and charger.

Note that if the chargers are not isolated from the mains, you may make some
sparks or loud noises, and/or let the smoke out of the chargers.  Better to
wear safety glasses, even if you're sure they're isolated.

David Roden - Akron, Ohio, USA
EVDL Administrator

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[Tim Humphrey]

You have a main disconnect contactor right? Put it in the midpoint of your pack and wire the two chargers to each half-set. The discontacted contactor will isolate the chargers from each other. Have it disconnect the chargers when it reconnects the pack and they are still isolated.

I'd also put another 'main' contactor at the contoller end. They're pretty cheap, see Rod Howers earlier post.

--
Stay Charged!
Hump
"If you don't "believe" you'll make a difference, than you probably never will!" -- Jim Husted


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[storm connors]

I am using 2 150v chargers in series to charge my 144v pack. (In the
winter it requires over 180v  at finish.) The chargers are 60 pound
military surplus multitap transformer/ bridge diode boxes. One
advantage is that each charger can be plugged into a different side of
the circuit- essentially charging off 240v.

If I split the pack, I have increased the likelihood of unbalanced
charging of the 2 packs. My understanding is that this is the biggest
problem faced by users of multiple 12v chargers. What happens if one
of the chargers isn't working correctly? What advantage would charging
2 72v packs have over charging one 144v pack?

On Jan 4, 2008 1:49 AM, EVDL Administrator <[hidden email]> wrote:

> Battery chargers will work in series (without that mid-pack connection) if
> they are fully isolated from the mains (transformer type) and dumb, dumb,
> dumb.  The smarter they are - that is, the more sophisticated the charge
> control is - the less the chance this will work properly.  I would be
> surprised if any but 100% manual chargers could be used this way.
>
> Nor do I see much reason to try.  Perhaps I'm missing something, but I can't
> see what you'd gain by connecting two chargers in series across the entire
> pack vs. splitting the pack, other than perhaps slightly simpler wiring
> between battery and charger.
>
> Note that if the chargers are not isolated from the mains, you may make some
> sparks or loud noises, and/or let the smoke out of the chargers.  Better to
> wear safety glasses, even if you're sure they're isolated.
>
> David Roden - Akron, Ohio, USA
> EVDL Administrator
>
> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
> EVDL Information: http://www.evdl.org/help/
> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
> Note: mail sent to "evpost" or "etpost" addresses will not
> reach me.  To send a private message, please obtain my
> email address from the webpage http://www.evdl.org/help/ .
> = = = = = = = = = = = = = = = = = = = = = = = = = = = = =
>
>
>
> _______________________________________________
> For subscription options, see
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>

--
http://www.austinev.org/evalbum/1059
http://stormselectric.blogspot.com/
Storm

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[storm connors]

Morgan said:
 If you have isolated chargers, you hook the two
> chargers in series, but you ALSO have to connect the place where the
> two chargers are connected to the center of your battery pack. From
> the charger's perspectives, each is charging its own 72V pack, but
> from your perspective, you have two 72V chargers in series charging a
> 144V pack.

This is not true. 2 dumb transformer based chargers in series will add
their voltages (or subtract them :-) if you miswire them.)

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[Morgan LaMoore]

I would recommend connecting the chargers to the center of the pack.
Yes, some chargers will work fine without that connection, but others
won't. For example, if each is operating in constant current mode at a
different current (even just calibrated differently), you have a
problem.

Imagine that charger 1 is set to some current and charger 2 is set 5%
higher. Imagine that the actual current is in between the two
setpoints. Now, charger 1 sees too much current, so it tries to
decrease the voltage to make up for it. Charger 2 sees too little
current and tries to increase its voltage to increase the current.
Then, charger 2 will increase in voltage until it reaches the constant
voltage part of the charge profile.

If your pack is discharged to 10.5V/battery and the constant voltage
phase is at 14.4V/battery, charger 1 will see
(10.5*2-14.4)=6.6V/battery. If the charger has some protection where
it refuses to charge if the voltage is too low, charger 1's protection
will trip, and the batteries won't charge.

Using a center connection doesn't take much more effort and will
either avoid a problem like this or do nothing.

-Morgan LaMoore

On 1/4/08, Jack Knopf <[hidden email]> wrote:

> I disagree. You can hook the chargers in series and only have two output
> leads.
> I have done this with many types of chargers and it works.
> The only type of charger I have found so far that this will not work is the
> new smart chargers.
> They turn off before they start their next cycle and will not restart when
> in series.
> But old Telco chargers, marine chargers, any chargers that remain on during
> their profile seem to work in series.
> Even different marine chargers, one with a manual/automatic switch, I put
> the switch in automatic to charge, then manual for a 2 amp equalize at a
> higher voltage.
> Perfect for Agm's.
> Let opinions on this list spark something in your mind and then go out in
> the garage and see if it will work.
> Never assume that what is said is a confirmed fact.
> Jack.
>
> "Knowledge is Certainty in the Real World, Not Data."
>
>
> ----- Original Message -----
> From: "Zeke Yewdall" <[hidden email]>
> To: "Electric Vehicle Discussion List" <[hidden email]>
> Sent: Thursday, January 03, 2008 11:53 PM
> Subject: Re: [EVDL] ev batt. chargers
>
>
> > You wouldn't really run them in series.  You'd just hook each one to a
> > separate 72 volt subpack of the 144 volt pack, similar to how some
> > people use separate 12 volt charges for each battery of a 120 or 144
> > volt string.  You'd need isolated chargers to do this, because the
> > positive of one pack would be the negative of the other pack.
> >
> > Z
> >
> > On Jan 3, 2008 9:47 PM, Josh and Jenifer <[hidden email]>
> > wrote:
> >>
> >> Can 2 72VDC Chargers be hooked in series to Charge a 144VDC pak?  I ran
> >> this
> >> topic through the archives,  but i did not come up with what i was
> >> looking
> >> for.
> >> --
> >> View this message in context:
> >> http://www.nabble.com/ev-batt.-chargers-tp14610840s25542p14610840.html
> >> Sent from the Electric Vehicle Discussion List mailing list archive at
> >> Nabble.com.
> >>
> >> _______________________________________________
> >> 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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> http://lists.sjsu.edu/mailman/listinfo/ev
>

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[storm connors]

Please explain how a dumb charger can be put into "constant current"
mode. It would eliminate a lot of my handholding.

Notice that in the scenario you describe, hooking up as you suggest
guarantees an unbalanced pack.

On Jan 4, 2008 11:27 AM, Morgan LaMoore <[hidden email]> wrote:

> I would recommend connecting the chargers to the center of the pack.
> Yes, some chargers will work fine without that connection, but others
> won't. For example, if each is operating in constant current mode at a
> different current (even just calibrated differently), you have a
> problem.
>
> Imagine that charger 1 is set to some current and charger 2 is set 5%
> higher. Imagine that the actual current is in between the two
> setpoints. Now, charger 1 sees too much current, so it tries to
> decrease the voltage to make up for it. Charger 2 sees too little
> current and tries to increase its voltage to increase the current.
> Then, charger 2 will increase in voltage until it reaches the constant
> voltage part of the charge profile.
>
> If your pack is discharged to 10.5V/battery and the constant voltage
> phase is at 14.4V/battery, charger 1 will see
> (10.5*2-14.4)=6.6V/battery. If the charger has some protection where
> it refuses to charge if the voltage is too low, charger 1's protection
> will trip, and the batteries won't charge.
>
> Using a center connection doesn't take much more effort and will
> either avoid a problem like this or do nothing.
>
> -Morgan LaMoore
>
>

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[Morgan LaMoore]

On Jan 4, 2008 10:24 PM, storm connors <[hidden email]> wrote:
> Please explain how a dumb charger can be put into "constant current"
> mode. It would eliminate a lot of my handholding.
>
> Notice that in the scenario you describe, hooking up as you suggest
> guarantees an unbalanced pack.

No. The scenario I described was for 2 smart (but non-isolated)
chargers. Each smart charger will properly charge its half of the
pack.

Sorry I didn't notice that you were talking about dumb chargers when I
replied to you.

You're perfectly right; for dumb chargers, a plain old series
connection will work just fine.

Some smart chargers, however, will need the extra connection that I described.

-Morgan LaMoore

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