[EVDL] wiring and fusing battery box?

--- Tehben Dean <[email protected]> wrote:

> If I have 3 battery boxes, #1 48v(4 cells), #2 120v
> (10 cells) and #3
> 144v (12 cells)

I think you mean "batteries" where you use "cells".

> Should I wire them so each box is a big battery and
> string them up
> with a return cable? Or should I have each box split
> with the to and
> from, so that there isn't a long return cable?

I'm not clear what you mean. But I would advise to
figure out cable runs to minimize total cable length
and maximize safety.

> If I fuse each box can I use all fuses rated for
> 312v (should I use
> 400v fuse?) or do the fuses have to be different
> sizes depending on
> where they are in the string?

I recommend a fuse in each battery compartment. That
way each is protected in case of an incident. And
each fuse must be rated for the total battery system
voltage and current.

> would it be a good idea to have breakers instead so
> I can break up the
> pack while performing maintenance?

Up to you. Breakers can be hard to come by or
expensive. I think Roland mentioned an Anderson
connector. Using a few of these in the right places
might be a good way to isolate battery boxes for
service.

> With less than 300amp current draw what size cable
> should I use?

Figure your average current and size it a for little
higher than that. Less than 300? Would that be 299?
Could be looking at 2/0 AWG. And remember, especially
if you have long cable runs, the larger gauge will
have less voltage drop. If you can afford it and it
fits in, bigger is better.

> Is
> gauge 4 the same as AWG 4?

Yeah, I think so. AWG stands for American Wire Gauge.
Most times you see "4 gauge" or "4 AWG". Which means
the same thing to me.

Hope this helps.

Don't see a lot of action on the old EVDL. EVerybody
must be at the races.

Jeff M

>
> Thanks,
> --
> Tehben
> '90 Toyota 4x4 Pickup
> 'hElix EV'
> Website: www.helixev.com
> evalbum: http://www.austinev.org/evalbum/1225
>




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--- Tehben Dean <[email protected]> wrote:

> > > If I have 3 battery boxes, #1 48v(4 cells), #2
> 120v
> > > (10 cells) and #3
> > > 144v (12 cells)
> > > Should I wire them so each box is a big battery
> and
> > > string them up
> > > with a return cable? Or should I have each box
> split
> > > with the to and
> > > from, so that there isn't a long return cable?
> >
> > I'm not clear what you mean. But I would advise
> to
> > figure out cable runs to minimize total cable
> length
> > and maximize safety.
>
> Ok, ummm let me try to phrase that better.
> If I have 3 boxes and treat them like 3 batteries
> and string them up
> in series I will have the negative cable left over
> at the back of the
> truck. WHich means a long run back to the
> controller.
> But If I spit the two front boxes into 2 groups of
> batteries and
> string one group in each box on the way to the rear
> box and then
> string the other group on the way back to the
> controller I won't have
> the long run.

O.K. Better explained, no clear answer, from me at
least. More than one school of thought on the
subject. And it depends how the batteries are
arranged inside the boxes. But like I said, it is
good to minimize total length of cable. But safely.
It may not make a difference in total cable length by
having a longer negative run.

Now, some might say it is best to have both cables,
pos & neg, side by side. This can minimize stray
inductance on the source side of the controller. And
reduce electrical interference. Some would say to
twist the two cables. I feel that is difficult and
unnecessary. However, for some commercial vehicles I
do, I run both cables together inside a liquid tight
conduit (safety and RFI). Boils down to your
decision.

> >
> > > If I fuse each box can I use all fuses rated for
> > > 312v (should I use
> > > 400v fuse?) or do the fuses have to be different
> > > sizes depending on
> > > where they are in the string?
> >
> > I recommend a fuse in each battery compartment.
> That
> > way each is protected in case of an incident. And
> > each fuse must be rated for the total battery
> system
> > voltage and current.
>
> So if I have a 48v battery and a 120v battery
> connected in series I
> would use the same fuse for each box?

When you end up with all the batteries connected in
series and any one fuse blows in the circuit, it sees
312 volts. So the safe answer is "all fuses rated for
312 volts."

Now, if it makes sense, you can get fancy and use a
main fuse rated at 312V say at 300 amps, and then
battery pack fuses rated at pack voltage (120, 48,
144V) with a higher current, say 400 amps. That way
an operational overcurrent condition takes out the
main 312V,300A fuse. But accidental shorts take out
the lower voltage, higher current fuses in the battery
boxes. I think this is risky and advise against it.

Now, my volts and amps are just examples. You should
consult your controller manual or supplier for
requirements. And there are many types of fuses, fast
blow, slow blow. You need to protect the equipment
like the controller and also the people in the car.
This is done by using the fuses for protection against
so high a current that it melts wire insulation or
batteries when an unforeseen incident occurs, such as
a dead short.

> > > would it be a good idea to have breakers instead
> so
> > > I can break up the
> > > pack while performing maintenance?
> >
> > Up to you. Breakers can be hard to come by or
> > expensive. I think Roland mentioned an Anderson
> > connector. Using a few of these in the right
> places
> > might be a good way to isolate battery boxes for
> > service.
>
> Do you have to worry about arcing when you plug and
> unplug Anderson connectors?

No...you should never unplug when current in flowing.
But Anderson connectors are very robust and will break
current if necessary. If you have some capacitive
load, you may see an arc when connection is made.
This can be eliminated with a precharge. Some
occasional small arcing will probably not damage the
functionality of the Anderson contact.

> > > With less than 300amp current draw what size
> cable
> > > should I use?
> >
> > Figure your average current and size it a for
> little
> > higher than that. Less than 300? Would that be
> 299?
> > Could be looking at 2/0 AWG. And remember,
> especially
> > if you have long cable runs, the larger gauge will
> > have less voltage drop. If you can afford it and
> it
> > fits in, bigger is better.
>
> Well my controller says it has 282 max amp in. But
> with a heater and stuff...

Should be in the controller manual. If not, ask the
guy who sold it to you.

But your heater should not be on the controller fuse.
It needs to be fused at the proper ampacity for the
wires you use for it.

Fuses in the battery line would have to have an
ampacity for the combined value of the branch
circuits.

Hope that helps.

Jeff M

> --
> Tehben
> '90 Toyota 4x4 Pickup
> 'hElix EV'
> Website: www.helixev.com
> evalbum: http://www.austinev.org/evalbum/1225
>


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