# Battery switch question...



## jwdsail (Dec 7, 2008)

Another, I hope not dumb, question.

Reading some of the posts regarding choosing between tire-melting performance and range, I thought of something I'm sure others may have tried so far...

Has anyone tried using a switch to change between series and parallel wiring of multiple battery packs?

Image in my head is a rotary switch (similar to those found in marine applications but able to take higher current.) that would be used to switch between the battery packs being connected in series and parallel depending on the task at hand... 

Just curious if anyone's done something like this and how the configuration has worked for them.

thanks


jwd


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## bblocher (Jul 30, 2008)

I believe the Zilla controllers, or an add on option, can do this for you already. It really only seems to be used in drag racing scenarios that I've seen myself.


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## jwdsail (Dec 7, 2008)

bblocher said:


> I believe the Zilla controllers, or an add on option, can do this for you already. It really only seems to be used in drag racing scenarios that I've seen myself.


That's good news, and means that I'm not completely nuts... 

I'm definatly leaning towards long range for a daily driver, but would be nice to have some extra omph if/when needed... still in the dreaming, research, drooling phase of all this.

Probably won't be drag racing the car allot, in my mind, it would only be needed once or twice a year to quiet any hecklers from the corvette club my father belongs to ;-)

And before anyone asks, no, he won't let me convert his 2006 C6. 



Thanks bblocher.


jwd


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## Voltswagen (Nov 13, 2008)

Jwdsail
Show this video to your Father and his Corvette cronies.
That'll shut 'em up!
http://www.youtube.com/watch?v=1Fmy4tWvr8c


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## TX_Dj (Jul 25, 2008)

No, the Zillas have the ability to trigger contactors which are used for a series/parallel shift between motors... not batteries.

Let's say you have 12 12v batteries, 100 Ah each.

12 * 12 = 144v (series) @ 100 Ah overall.

Now lets cut it into two parallel packs

12 * 12 / 2 = 72v (series/parallel) @ 200 Ah overall.

Now lets compute the Watt-hours...

144v * 100 Ah / 1000 = 14.4 kWh

72v * 200 Ah / 1000 = 14.4 kWh.

1 = 1.

Similarly, let's put a 500 A draw on those configurations.

500A / 1 String = 500A * 144v = 72kW peak

500A / 2 String = 250A * 72v = 18kW peak per string * 2 strings = 36kW peak

Similarly:

36 kW / 144v = 250A per battery.

But to get 72 kW out of a 72v system, you'd have to draw 1000 A.

But if you drew 1000A at 144v, you'd have a peak of 144kW.


Higher voltages mean lower amperages are required for the same watts output. Lower amperages mean smaller, lighter wires can be used, and also increases efficiency.

Switching your battery pack does nothing for you, assuming you use a controller... and you want a controller, especially in a race application, otherwise when you connect your two strings of 72v into the motor, the motor will attempt to draw an infinite amount of amps, blowing the motor or cables or batteries or...

Use a controller, and if you have two motors, use a set of contactors to switch the motors from series/parallel for max HP/max torque.


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## jwdsail (Dec 7, 2008)

TX_Dj said:


> No, the Zillas have the ability to trigger contactors which are used for a series/parallel shift between motors... not batteries.
> 
> Let's say you have 12 12v batteries, 100 Ah each.
> 
> ...


Wow, and thanks.

When you say two motors, would that be in a "Siamese" configuration? I haven't found a great description of that so far...

thanks again.


jwd


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## Bowser330 (Jun 15, 2008)

yes thats the way I have seen it...in siamese fashion...

the tango ev also uses the zilla 2K but im not sure it uses the electric shift... because its got one motor for each rear wheel....

too bad they dont make zillas anymore...


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## TX_Dj (Jul 25, 2008)

Bowser330 said:


> too bad they dont make zillas anymore...


I'm still hopeful that someone will come along and meet Ot's requirements for the IP license to continue manufacture... Of course given what he's asking for the price to play, and the requirements he's making for quality of construction and such, it's not likely it will happen unless demand increases substantially.

*sigh*

To my knowledge, Tango doesn't use the S/P shift... but if it did/could, then yeah... wow.


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