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Sun Mar 29, 2020 7:20 pm

Never had to jumpstart the van until now. Where do you ground when you’re battery’s not in the engine compartment?

Sun Mar 29, 2020 7:28 pm

I have enough of the battery ground bolt/stud showing through up behind my psng tire to clip to if needed, not that I've needed it yet.

Sun Mar 29, 2020 8:17 pm

Anything bare metal and beefy. If you're jumping the van, it should be battery to battery, so I guess I'm not understanding what the problem is? Just put the black wire on the negative side of your battery, positive on the positive. You should not be near your engine compartment if you're jumping a Vanagon...

Sun Mar 29, 2020 9:47 pm

What I meant was that in most cars the battery is in the engine compartment, so there’s plenty to ground to. Vanagon, not so much. I’m trying to do a “proper” jumpstart and not clamp the van negative to the terminal itself but to the body/ground. The seatbelt bolt/stud has been replaced with one of those rings to anchor the aux fridge in with. It’s yellow dichromate plated, so maybe not the best ground?

I finally remembered that if you swivel the seat around you get more access to the battery compartment (doh!) and there’s a bolt inside the compartment that probably makes a good ground. It turns out I didn’t have to try, as the problem was the neutral safety switch in the shifter, not the battery. I would have figured that out sooner if I had remembered how to properly put the wires in the multimeter.

Mon Mar 30, 2020 12:02 am

Dont ground to the negative. That will cause a spark right next to a hydrogen gas producing item. BANG!

You ground to any solid, preferably bare. metal and beefy item. The body, the seat belt bolt, pretty much anything around there.

Mon Mar 30, 2020 2:48 am

You can probably successfully ground to the negative terminal of the battery 99.9999% of the time without blowing up your Vanagon.You have this big open sliding door which has let all this nice fresh air in to dilute any residual hydrogen gas vapor which chances are was not there anyway since your battery was flat.
You will see hydryogen gas vapors when charging a battery and it has been on charge a good while nearing full charge of the battery and the individual cells have water on the around the caps. Only it is not water -it is SULFURIC ACID and not something to touch. You can wipe it away with a rag/paper towel and right into to garbage. They do not sell rubber gloves or safety glasses for no reason and battery charging is one of those reasons.
Or when your alternator is over charging a battery and you open the battery box which should be vented to not have this problem.

Your biggest hazard is not paying attention to the positive terminal clamp touching the body when it is connected to the positive terminal.
A child, dog or you moving too fast can catch the battery cable and tug it out of position to where it contacts the negative charged body of the car. You will get a good spark then or really extreme weld the bare metal of the connector to the body and start a fire.

Hydrogen gas is a definite hazard, but now that you know about it you should not be afraid of it and your Vanagon should not turn into the Hindenberg.

Mon Mar 30, 2020 4:18 am

Hook up the Vanagon first, then on the jumper vehicle hook + to the post and - to a good ground.

You just want to avoid the sparks generated at the last connection made being at the battery. It doesn't matter what vehicle is hooked up last or first.

Negative ( - ) is the last jumper clamp connected and good practice states that it is not connected to the battery.

Dave

Mon Mar 30, 2020 6:56 am

If the weak battery is more likely to produce hydrogen gas I would connect to the weak vanagon battery first and the second negative to the jumper battery or engine ground last.
Connection has not been an issue the few times I've had to do this in my lifetime ( + to + and - to - ), but obviously, someone found there was an issue, so something to keep in mind.

Mon Mar 30, 2020 7:32 am

djkeev wrote: Hook up the Vanagon first, then on the jumper vehicle hook + to the post and - to a good ground.

This. There will be no sparks unless the current if flowing.

Mon Mar 30, 2020 7:43 am

Butcher wrote: djkeev wrote: Hook up the Vanagon first, then on the jumper vehicle hook + to the post and - to a good ground.

This. There will be no sparks unless the current if flowing.

But there is the possibility the lights were left on, the wipers are on, heater blower is on or some other draw.... hence the dead battery.

Always prepare expecting that there WILL be a spark.

Dave

Mon Mar 30, 2020 8:15 am

I have always used the bolt head on the inboard passenger seat safety belt mount.

I never connect directly to the ground post on the battery. Possibly an unnecessary precaution but how I was taught.

Mon Mar 30, 2020 10:04 am

One other thing I thought about was jumpstarting the starter battery with the Aux battery.

I didn't know about the simple way to do this, by jumping the isolator solenoid:
https://www.gowesty.com/tech-article-details.php?id=154

So I tried connecting the aux battery straight to the starter battery. I had unplugged everything from the aux battery, and put a cable just from the positive of the aux to the positive of the starter battery and got a big spark.

I couldn't quite make out why this happened if the aux battery wasn't grounded. There was charge in the starter battery, but wouldn't it still need a ground?

Mon Mar 30, 2020 10:19 am

Did you hook + to + and - to - ?

Mixing them up can be exciting!

Dave

Mon Mar 30, 2020 11:41 am

djkeev wrote: Did you hook + to + and - to - ?

Mixing them up can be exciting!

Dave

No, just + to +
No - was attached. I do notice there’s another small wire coming off the positive terminal. I assume from the previous owner for Aux battery system. Maybe that’s what’s grounding?

Mon Mar 30, 2020 11:47 am

You can attach to the charged battery NEG terminal safely, last.

If the battery is in a near full state of charge, there will be no hydrogen of consequence present.

A chassis ground is safer but arguably in a de minimis manner.

Mon Mar 30, 2020 12:49 pm

[quote="Vantropy"]One other thing I thought about was jumpstarting the starter battery with the Aux battery. /quote]

Where is your Aux. Battery?
A battery is a battery whether it is in another car or under you bench seat.
Jumper cables Positive to Positive and since they are sharing a common ground that should be all you need. You should not need to connect the Neg. cable.
I just did it yesterday. :oops:

You said you disconnected everything from the Aux. Battery. Did you disconnect the ground?

Connecting the jumper cables correctly and you may get a small spark, but not a big one at least not like a blast from Thor.
Try disconnecting the extra red wire from your start battery Pos. terminal and see what happens.
At the very least trace it down and find out what it is powering.

Mon Mar 30, 2020 1:37 pm

I made a jumper cable specifically to use the aux battery to jump to the starter battery. I used 8 gauge - not massive but I think enough to get the job done in an emergency.

But now I also carry one of these:

https://www.amazon.com/gp/product/B07FML2HHD/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1

Mon Mar 30, 2020 3:29 pm

When two batteries are connected in parallel and one has a lower state of charge than the other, the lower voltage one will present a load to the other one the instant the circuit is completed. Current will flow at any difference in voltage, and the bigger the difference, the bigger the current and the bigger the gap it will jump as the circuit is physically connected. So if there is a difference in voltage there is a spark upon completing the circuit, if the V difference is small it may not be obvious but it's there, and if the V difference is large it will jump the gap at a larger distance and simultaneously a larger current will flow so the spark will be bigger and more obvious. But there will be a spark, however small, unless the two batteries are at equal V. And generally car batteries get jumped when one is at a notably lower V, so expect a spark whenever paralleling two batteries.

So when the OP connects the camping battery to the starting battery, both batts being grounded to the same chassis, he's completing a circuit between two batteries of unequal voltage, so of course there is a spark, and given the fact that the starting battery is at a low enough V to need a jump, the spark may be a pretty big one.

The chance if igniting the H2 emitted by such small batteries in free air is so miniscule as to be a non-concern.

Mon Mar 30, 2020 4:32 pm

tencentlife wrote: When two batteries are connected in parallel and one has a lower state of charge than the other, the lower voltage one will present a load to the other one the instant the circuit is completed. Current will flow at any difference in voltage, and the bigger the difference, the bigger the current and the bigger the gap it will jump as the circuit is physically connected. So if there is a difference in voltage there is a spark upon completing the circuit, if the V difference is small it may not be obvious but it's there, and if the V difference is large it will jump the gap at a larger distance and simultaneously a larger current will flow so the spark will be bigger and more obvious. But there will be a spark, however small, unless the two batteries are at equal V. And generally car batteries get jumped when one is at a notably lower V, so expect a spark whenever paralleling two batteries.

So when the OP connects the camping battery to the starting battery, both batts being grounded to the same chassis, he's completing a circuit between two batteries of unequal voltage, so of course there is a spark, and given the fact that the starting battery is at a low enough V to need a jump, the spark may be a pretty big one.
.

Great Explanation!

Mon Mar 30, 2020 4:35 pm

Never down play the danger of flooded lead acid batteries!

Sure, it happens infrequently but when it does happen?
You do NOT want to be on the receiving end of it.

I've never experienced one exploding ..... happily.
But I've seen the aftermath of a battery explosion. It ain't pretty. Acid burns on clothing and body and damage to everything in the engine compartment.

If I recall it was a 280SEL back in the 1970's.

This link is to an older article but it addresses the problem.

https://www.latimes.com/archives/la-xpm-1999-aug-26-hw-3902-story.html

Newer GEL batteries don't generate the gases the flooded cells do.

Once you get careless for it "rarely happens", is when you open the door wide open inviting tragedy in.

Dave