# charging and a precharge resistor



## Guest (Sep 3, 2009)

I have separate leads to my battery for charging. No charging current goes through any component. Just directly to the battery and it is fused. One on the first battery in the pack and one on the last battery in the pack. Both the first and last are next to each other and close to the motor where I have my charge circuit plug. Works perfect. I have my circuit separate because I do not like having current running back through any component. My setup works and you can't beat it.

Pete


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## voltmatic automaton (Nov 2, 2008)

So lets say i have my batteries in series (which i do) the negative lead is going to the load (controller + motor combo) the positive is cgoing to the contactor.

when active the contactor closes the circuit yes? (or is the circuit still open until the accelerator input is recived by the controller?)

if the circuit has a precharge resistor closing the space on the contactor then how does the pack charge if its a big loop.

my understanding is that to charge a series pack you have the most positive at one end and the most negative at the other end and you wire your charger accordingly.

this may be all simple to others but i would like to understand what and how this works and what effects there are on charging.


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## Coley (Jul 26, 2007)

The pre-charge resister has no effect on the charging. 

Just like it has no effect on the pack holding a charge, when you let it set for a month or more.


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## voltmatic automaton (Nov 2, 2008)

so then with my pre-charger resistor connecting both posts of the main contactor, i can charge happily.

would this mean then that essemtially it doesnt matter where i put my charger leads as long as they are on the pack somewhere?
eg. i could put the leads from the charger on a battery in the middle of the pack?

thanks for your patience


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## tj4fa (May 25, 2008)

voltmatic automaton said:


> so then with my pre-charger resistor connecting both posts of the main contactor, i can charge happily.
> 
> would this mean then that essemtially it doesnt matter where i put my charger leads as long as they are on the pack somewhere?
> eg. i could put the leads from the charger on a battery in the middle of the pack?
> ...


If your battery pack is in series, you should put the positive charger lead on your most positive terminal of the pack and the negative charger lead on the most negative lead in the pack.

You want to send the charging current through the entire pack not connected to one individual battery's terminals in the center of the pack.


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## Guest (Sep 5, 2009)

> One on the first battery in the pack and one on the last battery in the pack. Both the first and last are next to each other and close to the motor where I have my charge circuit plug.


I answered this for you awhile back. Go back and re-read the posts on this topic. 

Pete


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## voltmatic automaton (Nov 2, 2008)

I know i seem to be asking the same question Pete, but its only coz i want to understand what goes on when these components are all hooked together.

I am quite happy to go off and hook things up 'just like i been told to' but i really would like to know the whys behind the way things work.

So while you told me how you hooked your batteries up my real question (i guess) was why should it matter where the leads are if the resistor makes a closed circuit?

I f it seems like im repeating myself it simply coz no one has answered the question to satifaction... but i truely appreciate the answers thus far and the fact that anyone is trying to help.


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## Guest (Sep 6, 2009)

Ok, here you go. The pre-charge resistor is between the first and last battery. It is only for keeping the capacitors in the controller charged up so when full power is put through the controller you don't stress the capacitors. It keeps the capacitors alive. The controller only puts through full power when you request power with the throttle pot. The power from a charger needs to be placed at the beginning and end of the string of batteries. The pre-charge resistor is only for charging the capacitors and not meant to transfer the load from charging a pack. So with that in mind you can see that you need your charge connections at the beginning and end of the pack. I actually turn off all my connections so NO power can go through any other component while charging. When I shut down I also turn off my connection to the pre-charge resistor. I turn that on and let it set for a few minutes then I can put power to the controller. 

Does that help?

Pete 

Need a diagram?


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## voltmatic automaton (Nov 2, 2008)

No need for a diagram... 

I understand your outline. It does raise the question about not having a relay controlling the pre-charge.
am i right in thinking some people leave it permanently attached wired on all the time? how does that affect things?

Thanks again


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## Guest (Sep 6, 2009)

voltmatic automaton said:


> No need for a diagram...
> am i right in thinking some people leave it permanently attached wired on all the time? how does that affect things?
> 
> Thanks again


Yes, many just leave it on and no it does not affect anything. When the capacitors are charged up there is no further power draw from the pack. When it does need power it is so low it would take years to drain a pack to the point it would need charging again. 

I just like having all my power off when when I shut things down for the day. 

Pete


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## tj4fa (May 25, 2008)

For more info on Precharging, you can refer to this thread in the Wiki:

http://www.diyelectriccar.com/forums/showthread.php?t=25419


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