Alternator Power Tapping Location

bsqr

Member
Does your VS30 have the starter battery disconnect by the gas pedal?

If it does then connecting directly to the starter battery negative terminal MAY bypass the disconnect and lead to possibly dangerous situations (eg a tech thinks he's isolated the battery to work on air bags) or weird situations if the coach battery back feeds into the chassis system after the disconnect is pulled.

Keith.
Hmmmmm... I do have the negative disconnect by the gas pedal. My intention is that the connection to the starter battery negative post will be my only "chassis" connection so theoretically the chassis will still be isolated from the starter battery with the gas pedal disconnect removed. Sound right??? Reasonable??
 

Cheyenne

UK 2004 T1N 313CDi
Hmmmmm... I do have the negative disconnect by the gas pedal. My intention is that the connection to the starter battery negative post will be my only "chassis" connection so theoretically the chassis will still be isolated from the starter battery with the gas pedal disconnect removed. Sound right??? Reasonable??
Looks like the same situation is currently being discussed in this LTV based thread...

https://sprinter-source.com/forum/showthread.php?p=845157#post845157

Keith.
 

Skipperhbl3

New member
I thought I would follow up on this post. I read the VS30 Under Seat Wiring thread in the VS30 Database forum and learned that the F150-4 fuse box under the driver's seat may be an option as well. I also did some poking around under the driver's seat, in the battery compartment and under the van yesterday and found the following.

The F150-1 fuse box in the battery compartment is super tight. I'm wanting to connect a 2/0 cable and suppose it's doable, but looks tough. The F150-4 fuse box under the seat (post 2 or 6) looks OK, but I'm not sure how to access the weather boot to exit out the bottom. I'm sure temporarily removing and then reinstalling the components directly above the boot can be done. I'm just not super keen messing around with stuff like that in such tight quarters. I wouldn't rule out either of these options out as I know others have tapped alternator power here, but am somewhat intimidated by the tight quarters and large cable.

I don't have an OEM auxiliary battery so I don't have the F150-5 fuse box so that's not an option. I read in another post that the entire fuse box has no power when the auxiliary battery is disconnected so that wouldn't have been a good option for what I want to accomplish in any event.

So... When crawling around under the van I find a stud near the battery compartment with two lugged ring connector/conductors attached (photo attached). One conductor takes a direct uninterrupted path to the alternator and the other goes through the weather boot up into the space under the driver's seat into the F150-4 fuse box. I've read a lot posts about tapping for alternator power, but never heard any mention of this connection point. Wondering if there's any reason I couldn't tap onto that stud? It avoids the tight quarters in the battery compartment and under the driver's seat and is a direct connection to the alternator.

On a separate note, I'm using a Sterling Battery to Battery BB1260 Charger and it's recommended that a negative cable be run in lieu of using a chassis ground. I'm struggling to find an appropriate place to connect this conductor. The alternator is virtually inaccessible. I can't find the braided engine negative connection. Any suggestions?
Did you ever figure out what that empty terminal underneath is? I found the same thing and am very curious if it could be used.
 

bsqr

Member
Did you ever figure out what that empty terminal underneath is? I found the same thing and am very curious if it could be used.
I did trace the (18"-24") conductor uninterrupted to the F150-4 bus so I decided to go ahead and tie into that stud since others have successfully used the F150-4 bus. I've got everything roughed in and my "electrical gear board" completed, but need to get some other things done before I install the board and make the final connection so I can't determine if there are any issues with this point of connection yet.
 

judah8750

Member
I did trace the (18"-24") conductor uninterrupted to the F150-4 bus so I decided to go ahead and tie into that stud since others have successfully used the F150-4 bus. I've got everything roughed in and my "electrical gear board" completed, but need to get some other things done before I install the board and make the final connection so I can't determine if there are any issues with this point of connection yet.

Where did you end up running your grounds from the Sterling 1260 and the auxiliary battery? At one point you were going to the starter battery clamp.
 
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bsqr

Member
Were did you end up running your grounds from the Sterling 1260 and the auxiliary battery? At one point you were going to the starter battery clamp.
There was further discussion in another thread about the potential for disabling the OEM ground disconnect at the gas pedal if you were to connect your system ground to the starter battery negative. If your system ground is connected to the chassis in any way and you're connected to the starter battery negative there would be second path for the starter battery ground and the OEM gas pedal disconnect would not work.

Although I didn't intend on connecting to "chassis ground" at any other location, the potential for disabling the OEM negative/ground disconnect convinced me to find another location for connecting to the van negative/ground. My main goal with connecting into the van ground is to complete the alternator connection for charging my house batteries. Because of this a braided ground strap connected to the engine seemed like a good path. Right near the stud under the van where I connected my alternator positive conductor there are several (M8 or M10?) holes in the engine block that I assume are for accessories I don't have. I bolted a braided ground strap to one of these locations and bolted the other end of the ground strap to my alternator negative 1ga conductor lug.
 

judah8750

Member
I did trace the (18"-24") conductor uninterrupted to the F150-4 bus so I decided to go ahead and tie into that stud since others have successfully used the F150-4 bus. I've got everything roughed in and my "electrical gear board" completed, but need to get some other things done before I install the board and make the final connection so I can't determine if there are any issues with this point of connection yet.

Were did you end up running your grounds from the Sterling 1260 and the auxiliary battery?
There was further discussion in another thread about the potential for disabling the OEM ground disconnect at the gas pedal if you were to connect your system ground to the starter battery negative. If your system ground is connected to the chassis in any way and you're connected to the starter battery negative there would be second path for the starter battery ground and the OEM gas pedal disconnect would not work.

Although I didn't intend on connecting to "chassis ground" at any other location, the potential for disabling the OEM negative/ground disconnect convinced me to find another location for connecting to the van negative/ground. My main goal with connecting into the van ground is to complete the alternator connection for charging my house batteries. Because of this a braided ground strap connected to the engine seemed like a good path. Right near the stud under the van where I connected my alternator positive conductor there are several (M8 or M10?) holes in the engine block that I assume are for accessories I don't have. I bolted a braided ground strap to one of these locations and bolted the other end of the ground strap to my alternator negative 1ga conductor lug.

Hmmm, I don't have that quick disconnect on my van so I was planning on going straight to the battery as Sterling suggests and thinking I'll be ok. I did read through that other thread as well.

For positive, am I right in understanding you decided to still tap into this spot shown in the earlier photo as you traced up into the F150-4? Did you cut a small piece of the plastic to be able to get a lug on there? I have a circuit breaker I'll be adding to that line.

20200118_122012.jpg
 

bsqr

Member
For positive, am I right in understanding you decided to still tap into this spot shown in the earlier photo as you traced up into the F150-4? Did you cut a small piece of the plastic to be able to get a lug on there? I have a circuit breaker I'll be adding to that line.

View attachment 141598
Yes, that is the location I used for my alternator positive conductor connection. I also have a circuit breaker in line between that stud and my BB1260. I did cut a small piece out of the plastic hinged cover so it will properly latch closed with a second conductor present.
 

430 hp 70

'19 144 Gas Passenger - Carlsbad
There was further discussion in another thread about the potential for disabling the OEM ground disconnect at the gas pedal if you were to connect your system ground to the starter battery negative. If your system ground is connected to the chassis in any way and you're connected to the starter battery negative there would be second path for the starter battery ground and the OEM gas pedal disconnect would not work.
I'm adding an additional battery inside a cabinet by the rear tire and am trying to figure out my ground. I was planning on a body ground, but decided instead to run back to the starter battery. Now, I'm a little apprehensive about that. There is a ground post in the engine bay for the factory aux battery. I don't have the factory aux battery, so would this be the best spot?
 

bsqr

Member
I'm adding an additional battery inside a cabinet by the rear tire and am trying to figure out my ground. I was planning on a body ground, but decided instead to run back to the starter battery. Now, I'm a little apprehensive about that. There is a ground post in the engine bay for the factory aux battery. I don't have the factory aux battery, so would this be the best spot?
I'm probably not the best guy to be asking about this. I'm just trying to read and learn a lot myself. All I can say is based on what Sterling told me I would be cautious about using chassis ground for alternator charging when any significant amps are involved. They even recommended against using a OEM ground post in the rear of the van. If MB has a ground post in the engine bay that they use for their battery negative I imagine it can't be all that bad though...
 

Airtime

Active member
I have my driver seat off of my 2019 VS30 to figure out alternator tap point, so I thought I'd add on to this thread for the record. My plan from prior reading was to use F150/4 no. 6, but I wanted to verify the actual fuse ratings. So I did open heart surgery under the seat to get the attached picture. The front of the van is at the top, rear at bottom.
F150_4.JPG
Both 2 and 6 have fuses installed but unused. No. 2 has a 125A fuse, and no. 6 has an 80A fuse. Both of these match my fuse supplement. The 80A on no. 6 is perfect for my DC-DC converter tap point, I'm going with it. And better yet I don't need to install a breaker under the seat as I has planned, since it is already fused. I'll put a 60A breaker/disconnect in a more accessible place.
 

KyleS

New member
I have my driver seat off of my 2019 VS30 to figure out alternator tap point, so I thought I'd add on to this thread for the record. My plan from prior reading was to use F150/4 no. 6, but I wanted to verify the actual fuse ratings. So I did open heart surgery under the seat to get the attached picture. The front of the van is at the top, rear at bottom.
View attachment 143195
Both 2 and 6 have fuses installed but unused. No. 2 has a 125A fuse, and no. 6 has an 80A fuse. Both of these match my fuse supplement. The 80A on no. 6 is perfect for my DC-DC converter tap point, I'm going with it. And better yet I don't need to install a breaker under the seat as I has planned, since it is already fused. I'll put a 60A breaker/disconnect in a more accessible place.
I'm considering doing the same...how did this work out? Where are you tying back your negative/ground?
 

Airtime

Active member
I'm considering doing the same...how did this work out? Where are you tying back your negative/ground?
I haven't put it in yet, my cells came in so I've been busy with that. The positive will be easy, fuse already in place and terminal post ready and waiting. The negative will go on one of the Mercedes-designated M6 grounding bolts. There are two, they are down underneath the wiring on the right hand side of the driver seat pedestal (the side toward the passenger). There are already some ground connections there, but you can have up to four connections so there is room to add a ground cable. I looked underneath and it looks like they go through into a frame member so it should be good connection to the alternator ground, as expected since Mercedes specified them for grounding. I'll only tie my house electrical ground to the vehicle chassis at this one point.

I'll be in the shop today, I'll see if I can get some pictures of the grounding lugs.
 

I3uller

Member
InkedIMG_5602_LI.jpg

For what it's worth this is the setup I did. Connected directly to positive post and ran to driver's seat well where it is on a 100A breaker, then runs down the boot under the van to the back. I had the same issue with the unbridged bolts in the power distribution box. Figured I could keep things simpler and be able to reset/isolate the circuit with a breaker. I will be grounding to factory chassis ground in the back so that the stock disconnect by gas pedal still works properly, I'll update with what kind of efficiency I will get.
 

430 hp 70

'19 144 Gas Passenger - Carlsbad
[QUOTE="I3uller, post: 888737, member: 106332"

For what it's worth this is the setup I did. Connected directly to positive post and ran to driver's seat well where it is on a 100A breaker, then runs down the boot under the van to the back. I had the same issue with the unbridged bolts in the power distribution box. Figured I could keep things simpler and be able to reset/isolate the circuit with a breaker. I will be grounding to factory chassis ground in the back so that the stock disconnect by gas pedal still works properly, I'll update with what kind of efficiency I will get.
[/QUOTE]

Don't you need your breaker or fuse on the battery side? It seems you have a couple feet of wire without overload protection. Asking because I'm not positive of the answer.
 

I3uller

Member
[QUOTE="I3uller, post: 888737, member: 106332"

For what it's worth this is the setup I did. Connected directly to positive post and ran to driver's seat well where it is on a 100A breaker, then runs down the boot under the van to the back. I had the same issue with the unbridged bolts in the power distribution box. Figured I could keep things simpler and be able to reset/isolate the circuit with a breaker. I will be grounding to factory chassis ground in the back so that the stock disconnect by gas pedal still works properly, I'll update with what kind of efficiency I will get.
Don't you need your breaker or fuse on the battery side? It seems you have a couple feet of wire without overload protection. Asking because I'm not positive of the answer.
[/QUOTE]

You are correct that if there is a short before the breaker that wire would not be protected. ABYC dictates that the fuse or breaker should be no more than 7 inches away from the power source. My run from that positive post to the breaker is probably about 10 inches or so (indeed over what ABYC recommends) but its also very well managed and protected from chaffing etc. With how well it's protected from any damage I'm not super concerned with the possibility of a short in that 10 inch run. It's also extremely over sized. I'm using AWG 2 Ancor wire rated to 210 amps. The only way that cable would have any issues is with a short circuit from damage/chaffing but again it's not against any sharp edges and it's protected by the factory wire chase as well. I'm comfortable with my mitigation of short circuit risk but it's up to you what you want to do. Probably best to stay within ABYC standards and protect your cables as best you can.
 

Airtime

Active member
You are correct that if there is a short before the breaker that wire would not be protected. ABYC dictates that the fuse or breaker should be no more than 7 inches away from the power source. My run from that positive post to the breaker is probably about 10 inches or so (indeed over what ABYC recommends) but its also very well managed and protected from chaffing etc. With how well it's protected from any damage I'm not super concerned with the possibility of a short in that 10 inch run. It's also extremely over sized. I'm using AWG 2 Ancor wire rated to 210 amps. The only way that cable would have any issues is with a short circuit from damage/chaffing but again it's not against any sharp edges and it's protected by the factory wire chase as well. I'm comfortable with my mitigation of short circuit risk but it's up to you what you want to do. Probably best to stay within ABYC standards and protect your cables as best you can.
ABYC standards allow up to 40 inches if in conduit or enclosure.
 

KyleS

New member
I haven't put it in yet, my cells came in so I've been busy with that. The positive will be easy, fuse already in place and terminal post ready and waiting. The negative will go on one of the Mercedes-designated M6 grounding bolts. There are two, they are down underneath the wiring on the right hand side of the driver seat pedestal (the side toward the passenger). There are already some ground connections there, but you can have up to four connections so there is room to add a ground cable. I looked underneath and it looks like they go through into a frame member so it should be good connection to the alternator ground, as expected since Mercedes specified them for grounding. I'll only tie my house electrical ground to the vehicle chassis at this one point.

I'll be in the shop today, I'll see if I can get some pictures of the grounding lugs.
Any luck with positions 2 or 6?
 

Wavestucson

New member
I have my driver seat off of my 2019 VS30 to figure out alternator tap point, so I thought I'd add on to this thread for the record. My plan from prior reading was to use F150/4 no. 6, but I wanted to verify the actual fuse ratings. So I did open heart surgery under the seat to get the attached picture. The front of the van is at the top, rear at bottom.
View attachment 143195
Both 2 and 6 have fuses installed but unused. No. 2 has a 125A fuse, and no. 6 has an 80A fuse. Both of these match my fuse supplement. The 80A on no. 6 is perfect for my DC-DC converter tap point, I'm going with it. And better yet I don't need to install a breaker under the seat as I has planned, since it is already fused. I'll put a 60A breaker/disconnect in a more accessible place.
Hi thanks for the picture. I’m also about to connect a Renogy 50A dc to dc charger. That 80a connect on no.6 looks perfect for that. I see though you decided against using it in a later post. Any issues I should consider (like the smart alternator voltage output for example)? Thanks!
 

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