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Old Yesterday, 02:39 PM   #51
isdehart
 
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Default Re: Aux Battery Electrical Setup Help

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Originally Posted by autostaretx View Post
Most likely the other way around:
(a) they're only willing to detour 150 amps from the normal operations toward charging the Aux battery (want more current? Buy a second alternator).
(b) given 150 A, then use #3 wire. (they're German: 50 sq mm)

Thicker wire always lowers the resistive losses (usually measured as voltage drop).
If you're talking about the Sprinter's own alternator, some current must be allocated/reserved for engine operation.

--dick
p.s oh, good grief! There's a formula for AWG to sq mm:
Area (mm2) = (π/4)×dn2 = 0.012668 mm2 × 92^((36-AWG)/19.5)

(the caret (^) signifies "raised to the", so that's "92 raised to the ratio of (36 minus the gauge) divided by 19.5") ... how they handle the "naught" gauge numbers isn't clear...)
((the "dn2" in the intermediate formula means the diameter of the gauge in mm (the n is a subscript))

... i just cheated and used a web app.
Cool so I'll fuse the aux battery for 150 from the stinger?
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Old Yesterday, 07:00 PM   #52
autostaretx
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Default Re: Aux Battery Electrical Setup Help

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Originally Posted by isdehart View Post
Cool so I'll fuse the aux battery for 150 from the stinger?
What's the **Stinger's** current rating? That could be the limit.

(although rumor has it that MB's isolation relay is only a 100 amp device, faced with their 150 amp fuse. The "150" may just be to cover the (possible) relatively short-duration battery-to-battery surge if/when a dead (i.e. "severely depleted") house battery is coupled to the Sprinter's system.)

Note: i'm using "Stinger" as a generic term for "coil-driven high-current continuous-duty isolation relay". Other perfectly good (or perhaps better, or available with more appropriate current ratings) brands include Cole Hersee.

--dick
p.s. "generic" = "far easier to type" and "fairly recognizable as to meaning"
(cf: xerox and kleenex)
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2005 T1N 118" Freightliner 2500 Passenger Wagon (2.7L, 15" tires, standard (short) roof)
http://diysprinter.co.uk/reference <-- lots of service documentation, Thanks to Jens Moller and Arnie_Oli
((as always: this post may go through a couple of post-posting edits... so maybe give it ten minutes before commenting))
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Old Yesterday, 10:54 PM   #53
isdehart
 
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Default Re: Aux Battery Electrical Setup Help

Quote:
Originally Posted by autostaretx View Post
What's the **Stinger's** current rating? That could be the limit.

(although rumor has it that MB's isolation relay is only a 100 amp device, faced with their 150 amp fuse. The "150" may just be to cover the (possible) relatively short-duration battery-to-battery surge if/when a dead (i.e. "severely depleted") house battery is coupled to the Sprinter's system.)

Note: i'm using "Stinger" as a generic term for "coil-driven high-current continuous-duty isolation relay". Other perfectly good (or perhaps better, or available with more appropriate current ratings) brands include Cole Hersee.

--dick
p.s. "generic" = "far easier to type" and "fairly recognizable as to meaning"
(cf: xerox and kleenex)
cool. its a 200a constant and 500a peak. how much would you fuse between relay and aux battery?

would you still fuse for 150 at the alternator ? (I have 200a alternator)
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Old Yesterday, 11:53 PM   #54
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Default Re: Aux Battery Electrical Setup Help

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Originally Posted by isdehart View Post
cool. its a 200a constant and 500a peak. how much would you fuse between relay and aux battery?

would you still fuse for 150 at the alternator ? (I have 200a alternator)
Me myself would choose 150 amps (bowing to MB's choice).

As with all things, it's a compromise between:
(a) the alternator itself won't put out more than 200 amps, but when the Stinger closes, it has the starter battery available to cram current over the bridge, too.
(b) if the house battery is, for example, dead-shorted (somehow), we'd rather have the fuse pop instead of do damage on the Sprinter side (or stall the engine by dragging the Sprinter operating voltage too low for the ECU to handle).
(c) too small a value (say, 100 amps) might pop too (or needlessly) frequently.
(d) the higher rating the fuse you choose, the thicker the wires have to be for safety.
(e) if you only have a single 100Ah battery, there's a limit as to how much current it can accept when charging.
(f) (e) is somewhat fuzzed if you're feeding the inverter from the alternator

I'm planning on a 120 amp circuit breaker (it'll be a switch, too) between my 115 amp alternator (and battery) to my house battery.

--dick
p.s. Ok... admittedly, that's a rather limited sub-set of "all things"
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2005 T1N 118" Freightliner 2500 Passenger Wagon (2.7L, 15" tires, standard (short) roof)
http://diysprinter.co.uk/reference <-- lots of service documentation, Thanks to Jens Moller and Arnie_Oli
((as always: this post may go through a couple of post-posting edits... so maybe give it ten minutes before commenting))
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