# [EVDL] High voltage battery pack safety



## EVDL List (Jul 27, 2007)

I was wondering if someone could talk about safety concerns when
working with EV battery packs, or point me to a good reference?

Like if you touch a hot circuit in a building you will get seriously
shocked because it is grounded. But in an EV the pack is not grounded
so there is only concern if you touch both the + and - sides of the
circuit.. right?

Anyway, before I actually start wiring up my batt's I would like to
read up on safety.

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

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## EVDL List (Jul 27, 2007)

When working on a battery pack, the charger should be disconnected from the 
battery pack. The controller circuit is also disconnected from the battery 
pack, because in many controllers, the negative may go through the control 
and right to the motor, which may have a conductance path to the chassis by 
brush dust if you are using DC motors.

Make sure that the most positive end of the battery terminal is the furthest 
from the most negative end.

When you run many short rolls of batteries, it is best not to nave more than 
72 volts between each roll.

If the batteries are super clean, you can actually touch any battery 
terminal, but make sure your other hand is behind you or in you pocket.

Lay a rubber insulation blanket over the batteries and only exposing the one 
you are working on.

Lay a rubber type of fender protection mats over any expose metal parts of 
the vehicle.

Have one set of battery tools that have a insulated handle by heat shrinking 
one end of a box, open end, ratchet type or adjustable type wrenches.

A torque wrench that is normally in the one inch pound range, I first adjust 
it for the specifications it calls for and than slip over the handles a foam 
pipe insulation, the heavy duty type with glue edge that is use for air 
condition work.

Then lastly you could have the vinyl square tiles that are use for garages, 
for the EV to set on while you work on it for maximum safety.

Install a on board chassis mount GFI circuit breaker that is in the circuit 
between your input plug and a on board charger. This way, no matter what 
receptacle you plug into it will be GFI protective.

Do not wear any watches, rings and any metal while working on batteries. 
Wear clothes that are 100 percent cotton.

Do not work on the batteries just after they been charge, wait about 24 
hours.

The charger should not be in the same compartment as the batteries or any 
thing that may produce a arc.

Before the charger can start up, a totally enclosed exhaust fan exhaust a 
totally enclose battery box or area, which at the same time bring in fresh 
air. For maximum safety this will trip a pressure switch and a DC contactor 
to connect the charger to the battery or you could use a AC contactor to 
provide power to the charger.

If the battery exhaust fans shut down for some reason, than the charger will 
shut down.

A means of disconnecting the ignition circuit to start up the controller 
while the AC power connector is plug in. A micro switch operated a small 
contactor and/or use a extra power pole on the incoming AC contactor that is 
normally close while the contactor is close when the AC power connector is 
plug in.

This ignition circuit interlock will prevent you from driving off with AC 
plug connected.

If charging in a enclose garage or room, crack open the garage door a bit, 
or install a exhaust hose from the fan out pipe. Mine is a 2-inch pvc that 
comes out the bottom of the EV like a exhaust pipe and when its gets down to 
below zero, I run a exhaust hose through a port in the door like service 
stations do.

Also it is best to install a lover grill whole house fan in the ceiling if 
you do a lot of charging in a in closed space.

No open flames units in the same space that the EV is being charge.

Laatly, read and study the National Electric Code NEC Article 625 - 
Electric Vehicle Charging Systems which tells you want type, size and length 
of AC components to use for a EV.

Roland

















----- Original Message ----- 
From: "Tehben Dean" <[email protected]>
To: "EV mail list" <[email protected]>
Sent: Sunday, September 09, 2007 4:31 PM
Subject: [EVDL] High voltage battery pack safety


> I was wondering if someone could talk about safety concerns when
> working with EV battery packs, or point me to a good reference?
>
> Like if you touch a hot circuit in a building you will get seriously
> shocked because it is grounded. But in an EV the pack is not grounded
> so there is only concern if you touch both the + and - sides of the
> circuit.. right?
>
> Anyway, before I actually start wiring up my batt's I would like to
> read up on safety.
>
> Thanks,
> -- 
> Tehben
> '90 Toyota 4x4 Pickup
> 'hElix EV'
> Website: www.helixev.com
> evalbum: http://www.austinev.org/evalbum/1225
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
> 

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## EVDL List (Jul 27, 2007)

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## EVDL List (Jul 27, 2007)

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## EVDL List (Jul 27, 2007)

Another safety item I remember from high school. About
1928 a study was made of all electrocutions in the U.S.

90% had burns on their left hand or arm. Most people
are right handed, so it was attributed to the heart

being closer to the left arm. That gave rise to the
rule to hold your left hand behind your back.

I always warned lefties.

(Hope my memory from the 40s is correct!)

John in Sylmar, CA
Pro-choice, Pro-life, Pro PV, Pro EV.

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## EVDL List (Jul 27, 2007)

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## EVDL List (Jul 27, 2007)

Hi Tehben,

Getting shocked by DC is much better than AC. But it
can still hurt. You're pretty safe below 48 volts,
DC. Still, best advise is to avoid it in all cases. 
So stay away from completing the positive to negative
circuit with your body parts. And you can always have
an unsuspecting ground. So avoid touching a live part
and the chassis at the same time.

Avoid the possibility of shorting any part of the
circuit, like dropping a wrench. This causes flash
and molten metal projectiles. Like welding. These
hurt if they get on your skin or can damage an eye or
start a fire. So wear eye protection. I like to
cover all nearby exposed terminals with dry rags just
in case a tool slips. Just expose one at a time.

I also leave an intermediate connection on the pack
for the last connection made. Try to make that one a
convenient location about mid voltage. The higher the
voltage, the bigger the arc. Best to work in, say, 48
volt sections. If you're unsure of a connection, try
a volt meter across it first. You don't want to put a
large cable across two terminals showing voltage. 
Maybe touch the two terminals with a piece of 24 gauge
wire first. If there is a problem, the small wire
will vaporize without near the damage as caused by a
big cable. If the small wire across the terminals
doesn't vaporize or get hot, then connect the big
cable.

Use your volt meter a lot. Work it around the pack
often. Easier to find the problem like this and it
avoids melted terminals and fireworks. Use common
sense. Be safe.

Jeff M.





> --- Tehben Dean <[email protected]> wrote:
> 
> > I was wondering if someone could talk about safety
> > concerns when
> ...


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## EVDL List (Jul 27, 2007)

Understand your voltmeter. Many electronic meters are very high
input impedance, and can mis-lead you.

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## EVDL List (Jul 27, 2007)

I may seem silly, but it makes a big difference if you wear those 
thin blue "mechanics" gloves while you are working on (or near) the 
live parts of the car. You would not ever want to rely on them 
primarily to prevent a shock, but they offer "just one more" barrier 
to current flow if you make a mistake or touch something you didn't intend to.

If I neglect to put on the gloves, I get shocked once in a while. 
Conversely, when I have worn these silly blue gloves, I have never 
had a shock. Not even once.

Bill Dube'

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## EVDL List (Jul 27, 2007)

This is pretty timely.
I notice that if I've disconnected the pack, and
reconnect it 20 mins. later, there's a huge arc. Not
fun to be holding cable when it happens!
Lately, I wear the yellow latex dishwashing gloves. A
bit more awkward, but insulators, nonetheless.
I use insulated wrenches. Mine are done with
electrical tape, but there's also this plastic goo
that you can dump 'em in. Less chance of a short
between terminals (below). 
peace, 




> --- Jeff Major <[email protected]> wrote:
> 
> >
> > Hi Tehben,
> ...


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## EVDL List (Jul 27, 2007)

> Bob Bath wrote:
> > This is pretty timely.
> > I notice that if I've disconnected the pack, and
> > reconnect it 20 mins. later, there's a huge arc.
> ...


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## EVDL List (Jul 27, 2007)

[No message]


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## EVDL List (Jul 27, 2007)

> Tehben Dean wrote:
> 
> > I like the idea of working in 48v sections but am having a hard time
> > finding any switches rated at a high enough voltage and/or amperage.
> ...


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## EVDL List (Jul 27, 2007)

All,
Having had one bad shock through the chest when I got into EV's, I'm all about safety now, but why would you introduce more resistive connections and add more cost? I have one Anderson SB350 between the pack and the control board on both the truck and car, which I pull if I need to work on something past the pack. I hate to wear gloves, so if I need to replace a pack I wear them to discount enough interconnects to break the pack into <or= 48 volt segments, or if I'm installing a pack I make those connections last (with gloves on). Yes, it takes longer to undo an interconnect than to flip a switch or undo an Anderson, etc., but I wouldn't want to add anymore resistance to my 50+ feet of 2/0 and 24 battery interconnects that are already in the truck! Hope this helps...
Suck Amps,
BB


>Date: Wed, 12 Sep 2007 15:40:55 -0700
>From: "Roger Stockton"
>Subject: Re: [EVDL] High voltage battery pack safety
>


> >Tehben Dean wrote:
> >
> >> I like the idea of working in 48v sections but am having a hard time
> >> finding any switches rated at a high enough voltage and/or amperage.
> ...


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## EVDL List (Jul 27, 2007)

We had a quick exhange battery system using 16
Anderson SB-350 pairs. 32 contacts in series. No
problem.

Jeff M




> --- [email protected] wrote:
> 
> > I looked up the Anderson SB350 contact resistance:
> > its 50micro-ohms.
> ...


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## EVDL List (Jul 27, 2007)

All,
I just picked my knuckles up off the floor, got up out of my chair, and walked out to the shop to check my notes on the contact resistances in the eelectric truck. I keep a log of the voltages of each interconnect (in millivolts from battery post to battery post), while the Zivan is humping 13 amps into the pack. This was from a suggestion that Lee Hart mentioned years ago to determine the resistances of battery interconnects, and it's a great way to re-check connections (without putting your fingers on terminals, or using one of those new-fangled infrared temp sensors, which I don't have yet!). For the 33 inch run from the breaker on the control board through one-half of the SB-350 to battery number 24, it's seven millivolts. This was from my last log book entry two years ago. Re-measuring it just now it's up to eleven millivolts, but we will stay with seven. Looking at other interconnects of about the same length in my log, but don't go through a SB-350, I see about four m!
illivolts. So seven minus four equals three millivolts, or R=E/I or 0.003/13=0.000231 ohms (a little higher than the 0.000050 ohms mentioned below). Now with a grand total of 92 millivolts for my 66 feet of 2/0 from the control board through all 24 batteries, that's only 0.007 ohms. And at 200 amps to move my lead brick down the highway, that's only 280 watts or one percent of wasted energy from the pack. With an additional 24 SB-350 connections adding 0.006 ohms total, that's only 520 watts of wasted energy , so no big deal. And with SB-350's selling for only $23.50 (double poll on EVParts.com) times 12, or $282, that's only three percent of my $8500 conversion cost. Anyway, if my mathematics are correct, and you can live with making those additional crimps, etc., in order to avoid wearing gloves while pulling some interconnects on your pack, then go for it!
Suck Amps,
BB

>Date: Fri, 14 Sep 2007 18:27:27 +0300
>From: [email protected]
>
>I looked up the Anderson SB350 contact resistance: its 50micro-ohms.
>20 in series would give u 1 milli-ohm which is fine i would think for most
>everybody. 
>
>"Dave (Battery Boy) Hawkins" <[email protected] wrote
>>All,
>>Having had one bad shock through the chest when I got into EV's, I'm all about
>>safety now, but why would you introduce more resistive connections and add
>>more >cost? I have one Anderson SB350 between the pack and the control board
>>on both >the truck and car, which I pull if I need to work on something past
>>the pack. I >hate to wear gloves, so if I need to replace a pack I wear them
>>to discount >enough interconnects to break the pack into <or= 48 volt
>>segments, or if I'm >installing a pack I make those connections last (with
>>gloves on). Yes, it takes >longer to undo an interconnect than to flip a
>>switch or undo an Anderson, >etc., >but I wouldn't want to add anymore
>>resistance to my 50+ feet of 2/0 and 24 >battery interconnects that are
>>already in the truck! Hope this helps...
>>Suck Amps,
>>BB
>


> >>Tehben Dean wrote:
> >>
> >>> I like the idea of working in 48v sections but am having a hard time
> >>> finding any switches rated at a high enough voltage and/or amperage.
> ...


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