Battery Safety Advice/Questions

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mikejuv
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Joined: 12/12/2007
Points: 53

Does anyone have some basic safety "rules" or advice particular to working on or operating an electric vehicle?

I know to always turn off the breaker before working on wiring in my house. I know I need to disconnect a battery cable when working on certain things in my car. What do I need to know to safely work on my electric scooter?

To be more specific, here are a few questions I jotted down while wiring my Z for bank charging:
- Is there a correct procedure to disconnecting the batteries so you can work on the bike safely?
- If I get a shock from my five 12-volt batteries in series (60V), will it be lethal?
- Does anything on the bike retain a charge and remain dangerous after the battery series has been broken?
- Does it matter if I disconnect/reconnect the positive or the negative of a battery first?
- What is the safest procedure for connecting batteries in series? (Bat 1 Neg -> Bat 2 Pos -> Bat 2 Neg -> Bat 3 Pos -> etc ?)
- Are there special safety plugs that can or should be inserted into a battery terminal after a cable has been removed to prevent accidental contact?
- Do I need to remove an entire battery cable (both pos, neg ends) from the bike to be safe (prevent short) or is disconnecting one terminal good enough?
- If I only disconnect one positive or negative from the series, leaving the other end still connected, and that end touches something metal (or I touch it) will it spark?
- Do I need special, extra thick "boots" on the battery cables to hold back a spark if something metal comes near that terminal while the series is connected? Or are standard battery cable boots good enough for the 60 volts?
- If a battery cable end is exposed (no boot) while the series is connected, and something metal (or a person) touches it, will it spark?
- Is DC current more dangerous than AC?
- Who's brain can I pick locally? Is the average mechanic qualified to give advice on an EV, or do I need to find someone who works on semis, fire trucks and other large vehicles, or even an electrician?
- Would parking the bike in the sun, on a really hot summer day cause the batteries to become dangerous? Is there a temperature safety range for batteries?

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LinkOfHyrule
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Joined: 10/17/2007
Points: 730
Re: Battery Safety Advice/Questions

- Is there a correct procedure to disconnecting the batteries so you can work on the bike safely?

Not really. Just make sure that you don't touch the terminals of the string. Individual batteries are only 12V, and pretty much harmless if touched.

- If I get a shock from my five 12-volt batteries in series (60V), will it be lethal?

Possibly. 60V isn't anything to play with. You probably won't die, but you might be hurting. It's most dangerous if the current has to pass through your heart (like you touch the neg with your left hand and the pos with your right). Touching it with other parts of your body generally just causes pain. However, I've also heard of a guy who broke his arm (!) when he touched the terminals of a similar voltage pack and his muscle spasmed. Just be careful and you'll be alright.

- Does anything on the bike retain a charge and remain dangerous after the battery series has been broken?

The controller has several large capacitors in it. A few controllers have a bleeder resistor across them, so this charge is dissipated in time. You can test if yours does by leaving your controller disconnected for a minute or two and checking the voltage on the controller terminals. Be careful in any case.

- Does it matter if I disconnect/reconnect the positive or the negative of a battery first?

You might get conflicting info on this one. I'm not really sure. Judging from my last screw up, the positive side takes all the damage from an arc. Not sure what to make of it, though. However, most battery strings' positive and negative terminals share the same plug, so you're pretty much forced to disconnect them at the same time.

- What is the safest procedure for connecting batteries in series? (Bat 1 Neg -> Bat 2 Pos -> Bat 2 Neg -> Bat 3 Pos -> etc ?)

Probably connecting them up from each end. Don't think it really matters as long are you're careful, though.

- Are there special safety plugs that can or should be inserted into a battery terminal after a cable has been removed to prevent accidental contact?

Not that I know of. Generally, the hot wires are terminated with female plugs, so that they're hard to touch accidentally.

- Do I need to remove an entire battery cable (both pos, neg ends) from the bike to be safe (prevent short) or is disconnecting one terminal good enough?

You'll probably be fine with one, but two would be that much better. Like I said, though: Most plugs have both ends of the string in them, so you really have no choice but to disconnect both.

- Do I need special, extra thick "boots" on the battery cables to hold back a spark if something metal comes near that terminal while the series is connected? Or are standard battery cable boots good enough for the 60 volts?

No. 60V isn't close to high enough to cause anything of reasonable thickness and dielectric strength to go into breakdown. Just make sure you cover them with something.

- If a battery cable end is exposed (no boot) while the series is connected, and something metal (or a person) touches it, will it spark?

Hoooooooo boy will it ever. My last screw up, actually, was something like this. I accidentally cut through the live power leads of a battery pack. It was a tiny 48V 4.5Ah pack, yet it managed to blow a 3/6" hole in my wire strippers. It gave me a bit of a shock before that, too.

- Is DC current more dangerous than AC?

To my knowledge, it's the other way around.

- Who's brain can I pick locally? Is the average mechanic qualified to give advice on an EV, or do I need to find someone who works on semis, fire trucks and other large vehicles, or even an electrician?

How about ours ;).

I'm not sure about any of the auto guys. I don't think they really deal with the kind of stuff we do. An electrician might have a pretty good idea, though.

- Would parking the bike in the sun, on a really hot summer day cause the batteries to become dangerous? Is there a temperature safety range for batteries?

No temperature that a human could survive. I think they're pretty much okay unless you live in South Africa in a desert where it gets 140 degrees in the middle of the day.

You mostly want to keep them out of the sun because it's not good for them. You damage them a little, and they won't last quite as long. It can get pretty drastic if you do it often.

However, a lot of chemistries (SLA in particular), perform better when warm. Not hot. Warm.

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reikiman
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Joined: 11/19/2006
Points: 8456
Re: Battery Safety Advice/Questions

- If I get a shock from my five 12-volt batteries in series (60V), will it be lethal?

I think it depends on what you do with the batteries. If you stick the cables in your mouth that clearly could hurt a lot worse than when you lick a 9v battery to test its charge.

- Does anything on the bike retain a charge and remain dangerous after the battery series has been broken?

Depends on the design of the bike.

- Do I need to remove an entire battery cable (both pos, neg ends) from the bike to be safe (prevent short) or is disconnecting one terminal good enough?

That could help. Battery cables tend to flop around and have a mind of their own, and do things you don't want them to do like land on the opposite terminal and weld themselves in place. But of course it's more tedious to completely remove cables and it's tempting to just skip that step.

- Do I need special, extra thick "boots" on the battery cables to hold back a spark if something metal comes near that terminal while the series is connected? Or are standard battery cable boots good enough for the 60 volts?

I just installed some boots over the cable ends on my Lectra. They seem like a good idea but there's a difficulty getting the boot to properly fit over the terminal and all the wiring. Boots to me look like they'll help to prevent accidental contact and protect a little from the weather, but because they don't fit snugly it's an imperfect protection.

- If a battery cable end is exposed (no boot) while the series is connected, and something metal (or a person) touches it, will it spark?

Yeah, and I have a collection of melted tools to attest to this. It's amazing how quickly a tool can vaporize.

- Is DC current more dangerous than AC?

Ask Nikolai Tesla about this

- Who's brain can I pick locally? Is the average mechanic qualified to give advice on an EV, or do I need to find someone who works on semis, fire trucks and other large vehicles, or even an electrician?

Hmm, maybe the V needs a section where we can connect geographically. However one thing to look for is a local chapter of the EAA -- that's Electric Automobile Association, not Experimental Aircraft Association. Another resource to look for are forklift or golf cart or NEV mechanics.

- Would parking the bike in the sun, on a really hot summer day cause the batteries to become dangerous? Is there a temperature safety range for batteries?

Do you mean like does the sun give a battery a nasty attitude and it starts whistling at the women walking through the parking lot (or worse)? No, you're probably thinking about does the temperature affect battery life or perhaps make it possible for the battery to explode?

First -- for the latter -- it depends on the battery chemistry. But, yeah, I've read in other places that temperature does affect battery life.

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gushar
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Joined: 07/02/2008
Points: 360
Re: Battery Safety Advice/Questions

I was interested in those questions too...so that means I'm not an "expert" here. But I wanted just to add this...

I had a friend that was working on his auto engine and somehow accidentally shorted across the batt terminals with his wristwatch (or maybe his watch touched the pos terminal and was also in contact with a metal screwdriver...and the screwdirver touched a ground???). Anyway, it burned a gaping hole in his wrist and he had to have surgery on it to fix the tendons, etc. that were badly burned.

So, I do know this. Be very careful not shorting anything across ANY battery terminals/or pos to another ground...even just one 12 volt battery!

Gushar

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MarshallMiller
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Joined: 01/03/2008
Points: 14
Re: Battery Safety Advice/Questions

While working on the Meyers NMG (Corbin Sparrow) I realized the positive most terminal and the negatige most terminal are only four inches apart. Thats up to 170V of Optimas waiting to equalize. I imagine a wrench would explode if it became welded to the terminals. The high voltage areas are important to remember. Things like contactors, controllers, and chargers carry max volts and are easy to forget. Rule number one is to disengage the pack before even looking at the batteries. Having a kill switch is handy if you need to access your electric system often.

chas_stevenson
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Joined: 12/06/2006
Points: 1309
Re: Battery Safety Advice/Questions

If you placed the relay (contactor) somewhere in the battery string, between 2 batteries, when the relay is unenergized the 2 close positive and negative connections would do nothing if you dropped a wrench across them because you would not have a complete circuit.

Just a thought,
Chas S.

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