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Sprinter RV's & Conversions Talk Common features found in Sprinter RV's and Conversions.


 
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Old 07-01-2019, 05:17 PM   #11
autostaretx
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Default Re: A couple electrical questions

I haven't read the thread for its voltage/current discussion ... but i thought i'd toss in a comment about the "case ground"

That "case ground" is a safety connection for the odd chance that something inside the inverter (or DC-DC) box itself breaks and makes contact with the case. In something like a house, that "case ground" would be tied to "earth" ... a 6 foot copper rod driven into the ground.
("old school" is to clamp it on cold water pipes).
So it should be viewed somewhat as the 3rd pin (grounding) on a shore power connection: the case ground should go to the Sprinter's frame metal, so you don't end up with the case being *different* than the nearby Sprinter metal (lest your body create the "connection" between the two pieces of metal (case and frame)).

Since your proposed wiring does "common" the Sprinter's frame (alternator and starter battery negative pathway) with the negative bus, you're probably safe enough doing the case ground connection there.

But: what year Sprinter is this?
If you're an NCV3, your pencil drawing doesn't show where the Sprinter's "main negative disconnect" (near the pedal) fits into the circuit.

--dick
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Old 07-01-2019, 05:30 PM   #12
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Default Re: A couple electrical questions

I would go with 100 or 120 amp main battery fuse be for 220 amp. You can always size up. I do see how you would every have more than 100 amp draw with your 3000 watt Multi Plus even if you start your Air Con with the inverter. I don't think you intend to jump start your cab from your liFePo bank. Install a Trik L start to solar charge your cab AGM. I too have a Multi Plus 3000/24 and run a 120 amp fuse on my 24 volt 2 module tesla system.
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Old 07-01-2019, 05:35 PM   #13
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Default Re: A couple electrical questions

Also you may want to hold off in spending $400 on the sterling BtoB charger because your solar may charge well enough when driving as long as you have sun of course.
Install it later if you find you need it. You can pre wire for it.
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Old 07-01-2019, 05:36 PM   #14
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Default Re: A couple electrical questions

A 10kbtu AC unit may pull 100A @12VDC continuous, possibly more
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Old 07-01-2019, 07:15 PM   #15
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Default Re: A couple electrical questions

Quote:
Originally Posted by Midwestdrifter View Post
Those BBs will charge up to the mid 90s SOC at ~13.9V, even with some voltage drop. I see lots of folks installing DC-DCs "because lithium". Really they are not necessary with a 400AH bank, as you won't hit the charge limit with the factory alternator. Lithium also charges fine at lower voltages, with no sulfation risk from partial charge.

It depends on your risk tolerance, but adding a 100A (or 200A) fuse for each battery (or 2 battery sub-group) would provide some additional fault tolerance.

The BBs use a solid-state relay for the BMS disconnect. They re sensitive to current surges from starting inductive loads. I would avoid surges over 100A per battery on a regular basis.
Thank you midwestdrifter,
I have been reading and trying to comprehend all I can on the subject.

I had originally bought a VSR and a battery protect from Battle born, but then got scared off with some opinions that charging a big battery bank would put too much load on the alternator.

I guess the idea of limiting the current to 60 amps appealed to me and Battle born was kind enough to let me trade the VSR and battery protect for the B to B charger.

Because of my ignorance, the value of this large investment and having seen a number of pieces of equipment burned down, my risk tolerance is pretty low and I like the idea of the individual fuses at the battery.

Royce
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Old 07-01-2019, 07:25 PM   #16
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Default Re: A couple electrical questions

Quote:
Originally Posted by autostaretx View Post
I haven't read the thread for its voltage/current discussion ... but i thought i'd toss in a comment about the "case ground"

That "case ground" is a safety connection for the odd chance that something inside the inverter (or DC-DC) box itself breaks and makes contact with the case. In something like a house, that "case ground" would be tied to "earth" ... a 6 foot copper rod driven into the ground.
("old school" is to clamp it on cold water pipes).
So it should be viewed somewhat as the 3rd pin (grounding) on a shore power connection: the case ground should go to the Sprinter's frame metal, so you don't end up with the case being *different* than the nearby Sprinter metal (lest your body create the "connection" between the two pieces of metal (case and frame)).

Since your proposed wiring does "common" the Sprinter's frame (alternator and starter battery negative pathway) with the negative bus, you're probably safe enough doing the case ground connection there.

But: what year Sprinter is this?
If you're an NCV3, your pencil drawing doesn't show where the Sprinter's "main negative disconnect" (near the pedal) fits into the circuit.

--dick
Thank you Dick,
That is good to know.
The year is 2018 and the negative feed is connected directly to the sprinter battery.
So, when the sprinters main ground disconnect is open, there is still continuity between the sprinter battery and the neutral bus.
I hope that is not an issue.

Royce
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Old 07-01-2019, 07:26 PM   #17
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Default Re: A couple electrical questions

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Originally Posted by royce View Post
Thank you Mark,
Battle born rates their 100 amp hour battery for a 30 second surge at 200 amps, so would it need to be 200 amp fuses?

Royce


So is that 200 amps per battery? My 3000 watt/6000 surge inverter recommends using 400 amp fuse.


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Old 07-01-2019, 07:29 PM   #18
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Default Re: A couple electrical questions

Quote:
Originally Posted by Geriakt View Post
Also you may want to hold off in spending $400 on the sterling BtoB charger because your solar may charge well enough when driving as long as you have sun of course.
Install it later if you find you need it. You can pre wire for it.
Thank you Geriakt,
I committed to the B to B, for the lack of sun at this latitude.

Royce
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Old 07-01-2019, 07:33 PM   #19
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Default Re: A couple electrical questions

Quote:
Originally Posted by gltrimble View Post
So is that 200 amps per battery? My 3000 watt/6000 surge inverter recommends using 400 amp fuse.


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Gltrimble,
Yes, as I understand it, it is per battery.

Royce
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Old 07-01-2019, 08:50 PM   #20
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Default Re: A couple electrical questions

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Originally Posted by sparkplug View Post
Yes - sorry, from what I've heard (and as I've said, I'm a very long way from being an expert) a VSR will only charge leisure batteries to 80% from solar alone in the configuration I described.
And as I've said, that is nonsensical, 100% false, cannot even imagine any basis for anyone saying that, unless their system had something seriously wrong with it.

When voltage is high, it connects, when low it isolates, that is all.

Now of course there are many reasons why solar may not refill a bank, but nothing to do with a VSR in between.
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