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Old 10-17-2016, 06:28 PM   #141
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Default Re: Another Electrical Thread: Don't let me catch it on Fire!

Let's not underestimate correct grounding procedures. I've seen good designers lose their job due to grounding/noise issues that appear later.

Sterling B2B is new to the RV world. This device is operating at around 100kHz. It has a noise signature, not seen before. Can this noise interact with engine electronics? You can minimize that possibility by using a separate house-battery-chassis-ground connection. In other words, no other engine ground connections at this location. The other option is running a direct ground cable to the chassis battery.

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I fully support invention or innovation to fix something not working, broken, or not available but for crying out loud not to fix something working well for many.

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Old 10-17-2016, 06:28 PM   #142
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Default Re: Another Electrical Thread: Don't let me catch it on Fire!

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Graphite Dave's Wonder Show of an electrical system - sleeping under your electric blanket one night


So if I understand your thinking I should never have built a DIY conversion. I should have bought a standard off the shelf motorhome to be sure I did not do anything different. Does make some sense. Everything just like it has always been done without any original thinking. I could even limit myself to parking in RV parks so I could stare at the next units sewer pipe like everyone else.

ps: It is an heating pad not a blanket.
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Old 10-18-2016, 01:15 AM   #143
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Default Re: Another Electrical Thread: Don't let me catch it on Fire!

Just for grins, I thought I'd offer up some pics of my little project....











Cabinets, electrical, et all next on the list...
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Old 10-26-2016, 08:30 PM   #144
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Default Re: Another Electrical Thread: Don't let me catch it on Fire!

Ok quick question...

Trying to determine total circuit length for my schematic. Looking at my diagram, do I measure the actual circuit or do I measure from the starter battery, through the entire circuit, including the ground wire that runs all the way to the driver's seat for a chassis ground?
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Old 10-27-2016, 02:11 AM   #145
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Default Re: Another Electrical Thread: Don't let me catch it on Fire!

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Ok quick question...
Wanna bet?
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Trying to determine total circuit length for my schematic. Looking at my diagram, do I measure the actual circuit or do I measure from the starter battery, through the entire circuit, including the ground wire that runs all the way to the driver's seat for a chassis ground?
(perhaps it would help if we had the new/final schematic?)(maybe drawn on a Sprinter floor plan?)
((dozens of Sprinter questions and solar/whatever circuits have drifted past the eyeballs in the last week))

"total circuit length" is both ambiguous and perhaps unnecessary. (added: see p.s.)

If you're trying to estimate (say) voltage drop over a run, you would look at the path that *that* device's currents will be following.

If your "circuit" is from the starter to the house battery (via an isolator, for example) and then bringing the negative back through the same gauge wire, then: YES, total length is the full round-trip.

If, however, you're using the chassis metal as the "negative" return, then i'd just look at the positive length, since we haven't got a good clue as to what "wire gauge" the metal frame might be equivalent to (but it'll be pretty thick, even though it's steel, not copper).

If you have things attached along the way, then you'd need to add in the other currents that might be taking only a partial trip through the main starter-battery-to-house circuit.
((i'm an opportunist... if there was a tap available on the isolator relay for some nearby house-powered device to casually hook on to, i'd use it... and then the current feeding that device is either coming from the house or (probably) the alternator depending upon the relay's state. Bad practice? Probably... but if it's convenient i'm willing to brush with the Dark Side))

But for a simple (let's say) 4 gauge from starter batt positive to house batt positive and 4 gauge from house negative back to sgtarter batt negative, it would just be the total length of copper involved.

---dick
p.s. (upon re-reading the question) what's "the actual circuit"?
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Old 10-27-2016, 03:50 AM   #146
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Default Re: Another Electrical Thread: Don't let me catch it on Fire!

Dick,

Thanks for the response. Here's my final schematic with the proposed distances of the wire runs. The solar is only pushing out 20A, the battery to battery charger is pushing out 60A. If my calculations are right, 2AWG wire should be sufficient to do the trick.

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Old 10-27-2016, 03:59 AM   #147
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Default Re: Another Electrical Thread: Don't let me catch it on Fire!

Good looking schematic but it would help to increase the font size, not readable on my 32" monitor. Photobucket requires signing in to see a magnified image. Have you look some online calculators to define the wire size?

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Old 10-27-2016, 05:36 PM   #148
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Default Re: Another Electrical Thread: Don't let me catch it on Fire!

Yes, I've utilized some chats and calculators. Based on the info from this sources I'm about one gauge larger than required. But the 10' ground wire starts to stretch the length portion of the calculation if I measure "there and back". But if the ground wire is out of the loop so to speak, do I have to include it in the calculation?

No access to a computer for a few days...just phone. I'll update with PDF Sat.
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Old 10-27-2016, 06:40 PM   #149
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Default Re: Another Electrical Thread: Don't let me catch it on Fire!

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Yes, I've utilized some chats and calculators. Based on the info from this sources I'm about one gauge larger than required. But the 10' ground wire starts to stretch the length portion of the calculation if I measure "there and back". But if the ground wire is out of the loop so to speak, do I have to include it in the calculation?
As drawn, the 10 foot ground wire is very much in the loop. You have to include it. (plus the extra 2 feet to the house battery).

If, instead, you tied to the chassis at your negative bus' location, you wouldn't need the 10 foot negative cable, since you'd be using the vehicle frame to carry the current.

There has been a lot of do/don't chatter (all valid) about that approach... something i'd love to see would be someone who's done it (i.e. uses the frame instead of a "return cable") and then accurately *measured* the voltage drop on the "ground-to-ground" (house-to-starter batt negative posts) connection.
Such an accurate measurement might not be "easy", but it would certainly be informative.
For the folks who think a "home built" frame connection at the Sprinter's rear is difficult to do well, my suggestion would be to use two or three (thus increasing the surface area of the effective "steel conductor"). Remember that (at least on the T1N) MB uses the frame as the ground return for the starter ... between the ground strap's anchor and the battery's negative cable tie-point.

--dick
p.s. for overly-anal quibbles, you haven't included the infamous Y-cable betwixt starter batt and alternator... your charging current is going to be traversing that distance, too.
p.p.s. and the alternator is using the frame as *its* negative return... you're already half-pregnant!
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Last edited by autostaretx; 10-27-2016 at 06:51 PM.
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Old 10-27-2016, 07:35 PM   #150
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Default Re: Another Electrical Thread: Don't let me catch it on Fire!

Can you specify the requirements you used to calculate your cable sizing?

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Yes, I've utilized some chats and calculators. Based on the info from this sources I'm about one gauge larger than required.
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