Battery-Grounding Strap-Ground Block question

[Flying Scotsman]

This might belong in the electrical forum...if so, my apologies and a moderator can move it, I guess.

Basically, looks like 3 options for the combination of battery/grounding strap/wire to ground block on the firewal:

1) Battery negative to ground block on the firewall and thence to engine via grounding strap
2) Battery to engine via grounding strap thence to firewall via something
3) Battery to engine via grounding strap, and Battery to ground block on firewell via big honkin' wire

I just installed option #3 (temporarily while I am doing electrical layouts, ordering wires, etc.). Is there any disadvantage to this? Is one option or another preferred, and if so, why?

TIA!

Steve

[gasman]

#1 is good because it has only one ground wire connection at the battery for convenience. But I added another (second) ground strap from the firewall to the motor case.

If the ground strap fails, the power for the starter will ground through your throttle and mixture cables.

You don't want that to happen!!

[Walt]

How about Option 4: (what I did)

Battery to Engine
Battery to Firewall Grd blk
Firewall Grd Blk to Engine

[alpinelakespilot2000]

Off the top of my head, Van's optional wiring instructions call for only:
1. ground engine case to firewall (where the breather tube is attached with the adel clamp).
2. ground battery to firewall ground stud (wherever you chose to put it).

[gasman]

Originally Posted by Walt

How about Option 4: (what I did)

Battery to Engine
Battery to Firewall Grd blk
Firewall Grd Blk to Engine

The reason I don't care for this option is you are dealing with installing two ground cables on the battery terminal. Extra work. You already have the ground cable from the battery to the firewall ground block. And from the firewall ground block to the engine case. Second strap can be a braided strap mounted out of the way.

[Flying Scotsman]

Originally Posted by Walt

How about Option 4: (what I did)

Battery to Engine
Battery to Firewall Grd blk
Firewall Grd Blk to Engine

OK, let's add that as a fourth option, and I can see why (as a fail-safe in the event one of the ground straps to the engine fails, there is a backup).

That means there's a fifth

Battery to Firewall
Battery to Engine
Engine (different location than first strap) to Firewall/Motor Mount (different location than Grd blk)

I'm looking for pros/cons on these options, not just "Nuckolls said do it this way" or "Van's plans show this". Specifically, things like:

Number of fasteners on a single joint (e.g., battery terminal)
Possibility of EMI-type noise introduced into the system
Structural failure due to vibration
Etc.

[gasman]

Originally Posted by Flying Scotsman

That means there's a fifth

Battery to Firewall
Battery to Engine
Engine (different location than first strap) to Firewall/Motor Mount (different location than Grd blk)

I'm looking for pros/cons on these options, not just "Nuckolls said do it this way" or "Van's plans show this". Specifically, things like:

Number of fasteners on a single joint (e.g., battery terminal)
Possibility of EMI-type noise introduced into the system
Structural failure due to vibration
Etc.

Battery to firewall should be..... battery to firewall ground stud pass through. This one step grounds the airframe and creates a grounding stud on the back side of the firewall for panel grounding needs. The same grounding stud on the engine side can now have a ground strap that will ground the motor case. Existing hole at base of dip stick tube. This allows one ground cable connection at the battery. Now you only have one ground disruption during battery maintenance. Bad grounds cause most of your electrical and gauge problems. Each of these grounds should be installed coated with DE-OX. http://www.ilsco.com/ProductsDetail....H6bdLf9Gjks%3d

All you need now is another ground strap located out of the way. Failure of the motor ground, or not remembering to re connect it will melt your throttle and mixture cables when you hit the starter.

Try to keep all of your maintenance items as simple as possible. And less clutter helps during maintenance.

[Flying Scotsman]

Originally Posted by gasman

Battery to firewall should be..... battery to firewall ground stud pass through.

Sorry if I wasn't clear...that *is* what I meant, of course.

[LettersFromFlyoverCountry]

I ran a #2 from the right side of the engine to the firewall in a way that would allow it to be clamped properly and connected it via a bolt/nutplate on the firewall, having drilled out a rivet on one of the angle supports. Kept it away from a bunch of other stuff.

I connected the battery to the firewall "forest of tabs," which sits just above it.

I considered myself done at that point, as I recall. I believe this was what the Van's plans recommended

[DanH]

Originally Posted by Flying Scotsman

1) Battery negative to ground block on the firewall and thence to engine via grounding strap

As above, battery to ground block brass bolt with a #2 or #4 cable, well crimped ends or soldered ends. Braided ground strap from brass bolt to engine.

Good stuff:

http://www.bandc.biz/groundblock24-tab.aspx

http://www.bandc.biz/braidedbondingstrap.aspx

Originally Posted by Bob Collins

I ran a #2 from the right side of the engine to the firewall in a way that would allow it to be clamped properly and connected it via a bolt/nutplate on the firewall, having drilled out a rivet on one of the angle supports. Kept it away from a bunch of other stuff. I connected the battery to the firewall "forest of tabs," which sits just above it.

Bob, the ground cable from the engine is clamped to the firewall, not directly to the forest of tabs?