Renogy DCC50S - alternator wiring

mr.vanley

New member
Hi everyone! First post, but I need some help!

I'm in the process of converting a 2010 Freightliner Sprinter, and have got almost all of the electrical done. I'm running into issues with wiring the Renogy DCC50S alternator wiring to the van's starter battery. The negative post on the starter battery does not have an easy way for me to attach the negative wire for the common ground to the DCC50S. Since the battery is grounded to the chassis as well, do I need to run the negative wire directly to the starter battery? The manual says I can connect directly to the chassis, but I also have a shunt in place for my battery monitor.

I guess my question is in two parts:
  1. Will skipping the negative wire to the starter battery cause any problems?
  2. If no problems will arise, will my battery monitor still be accurate, since not all circuits are grounded through it?

Thanks in advance for the help!
 

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borabora

Well-known member
You don't absolutely need to run a neutral wire between the starter battery and the charger but it is highly recommended. Why is it so difficult to wire to your negative battery terminal? It shouldn't be.
 

mr.vanley

New member
You don't absolutely need to run a neutral wire between the starter battery and the charger but it is highly recommended. Why is it so difficult to wire to your negative battery terminal? It shouldn't be.
There's just no room on the negative post, and nothing to attach to on the negative wire of the starter battery. Is there something you recommend that I can slip in there in addition to the negative connection?
 

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borabora

Well-known member
It's hard to see but the same type of clamp that on the + terminal should do the job. It looks like - cable is long enough that you could cut it and attach a lug.
But what I would do is just attach a 1/4" lug to the tightening screw on the - terminal. A bit Mickey Mouse but it would work.
If you decide to use chassis ground just make sure it's a fairly beefy and clean connection. As long as your shunt is the only path to ground the monitor will work just fine
 

autostaretx

Erratic Member
You need *some* (honking thick) connection from your house system's common negative to the Sprinter's negative.
It can just use the frame, or a big wire to somewhere else. But any current you're expecting from the alternator has to return to the alternator via that connection. That's why it's called a "circuit".

If you have a shunt on the negative side of your house battery, the charging current wants to go through it, too.
So your attached drawing above has the "tie to frame" misplaced. It wants to be on the other side of the shunt (where everything else is). If the alternator current does not pass through the shunt, your battery monitor won't know about it.


By using the frame, your master disconnect (if you have an NCV3 or VS30) will still work to remove the starter battery from its Sprinter loads (and from your house system). If you were to wire directly to the Starter Battery negative, you would be compromising/bypassing that master disconnect (the thing by the driver's foot).

--dick
 

mr.vanley

New member
The DCC50S manual recommends 4awg for runs >15', mine is right at 15', so I got 4awg.

If you have a shunt on the negative side of your house battery, the charging current wants to go through it, too.
So your attached drawing above has the "tie to frame" misplaced. It wants to be on the other side of the shunt (where everything else is). If the alternator current does not pass through the shunt, your battery monitor won't know about it.
I'm assuming you mean - if I plan on just connecting to the chassis and skipping the negative wire run, the "tie to frame" would need to be before the shunt to be accurate/effective? Or do you mean that I need to switch that up regardless?

By using the frame, your master disconnect (if you have an NCV3 or VS30) will still work to remove the starter battery from its Sprinter loads (and from your house system). If you were to wire directly to the Starter Battery negative, you would be compromising/bypassing that master disconnect (the thing by the driver's foot).
I do have an NCV3, I'm trusting it does not have the smart alternator based on some other posts on sprinter-source (hopefully that's right, I'll be checking the voltage before installing everything just to be safe). I wasn't aware of the master disconnect by the driver's foot - do you have a picture of that, google isn't showing me anything that seems relevant.

It feels like I'm damned if I do, damned if I don't on this one - but that may just be my newbiness to the electrical system.
 

borabora

Well-known member
Your NCV3 does have a smart alternator but it's not a factor unless you're worried about drawing too much current when charging your house batteries. You are a bit above the recommended limit but many people do this and are fine.

All current flowing in and out of the negative terminal of the house battery must flow through the shunt. Get a bus bar (250 amp) and make the following connection:
house battery (-) --> shunt --> negative bus bar
Now use the bus bar only to make (-) device connections to the house battery

Do not connect the (-) bus bar to the chassis but connect the negative wire of the Renogy charger output, the fuse box and inverter etc to the bus bar.

(1) If you decide to use the chassis connection for the Renogy charger then connect the Renogy (-) input (connection to the chassis battery) to the chassis.

(2) If you figure out a wire solution then connect the Renogy (-) input (connection to the chassis battery) to the chassis battery (-) with 4 gauge wire.

Either of the above will allow your master disconnect to work properly.

In this configuration your house battery isn't explicitly tied to the chassis (it is anyway via the Renogy) and every house device should have a negative wire back to the house battery instead of a negative wire to the chassis.
 

Ulter

Member
Your NCV3 does have a smart alternator but it's not a factor unless you're worried about drawing too much current when charging your house batteries. You are a bit above the recommended limit but many people do this and are fine.
No his Sprinter does NOT have a smart alternator.
 

borabora

Well-known member
No his Sprinter does NOT have a smart alternator.
If it's a NCV3 then it should have a LIN bus controlled "smart alternator." I don't know if Freightliner marketed models change that. It shouldn't matter for this discussion as long as the alternator can handle the extra load.
 

Ulter

Member
If it's a NCV3 then it should have a LIN bus controlled "smart alternator." I don't know if Freightliner marketed models change that. It shouldn't matter for this discussion as long as the alternator can handle the extra load.
You are misusing the term “smart alternator”. Smart alternators are variable voltage where the voltage runs lower and then spikes while driving. The only NCV3 Sprinter that has a smart alternator is the 4cyl. The 6cyl does not have a smart alternator.
 

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