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Old 01-10-2014, 03:55 AM   #21
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Default Re: Tapping into MB factory installed aux battery

By removing this copper piece and replacing it with a fuse, what size fuse is recommended. 100amps? Also does there need to be another fuse between the positive lead and then..say inverter?
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Old 01-10-2014, 03:11 PM   #22
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Default Re: Tapping into MB factory installed aux battery

Quote:
Originally Posted by Legwound View Post
I got my several small inverter advice from the link in the conversion forum

http://sprinter-source.com/forum/showthread.php?t=14341

Post number 3, top link to handybobsolar. His lengthy article suggests smaller inverters over a single large inverter. According to Bob, all the inverters have a draw, even when not feeding a device, and larger inverters have higher idle draw.

I'm thinking of 2-3 for my purposes, starting with a small one and adding as needed. I'd only turn on what I need to avoid drain. I'm not an expert and am only repeating what I've read elsewhere so it could be a flawed strategy. More research.

I am very open to inverter advice as to sizing and brand/models
The solution I use for inverter use is to turn it on when I need 120 volt power and then turn it off when I do not need power. No drain in between. I worked on the van with power tools a few weeks ago and forgot to turn off the 1000 watt Magnum. Next morning when I checked SOC it was at 94% when it is normally at 99%. Quickly saw that inverter was on. No 120 v items running, just the inverter without a load. I have a 255 amp-hr battery.
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Old 03-21-2014, 09:23 PM   #23
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Default Re: Tapping into MB factory installed aux battery

So I have a couple questions about this. Our electrical system is not ready for prime time, and we are heading out next week. We'd like to run a frig, and perhaps a couple LED lights and 12 volt cigarette lighter sockets. Can I just hook into that post next to the copper "not fuse"? Will this run only from the auxilliary battery, and not run down the chassis battery? And will this get power from the engine while running?

Also, when it is time to hook up the main system, Im using a Sterling alternator to battery charger. Do I hook that up to the same place, assuming that when the engine is running I'm getting alternator output at this point? If not, is there another point in/near driver's seat where I do get direct alternator output?

Thanks
john
'14 2500 170 with 4 cylinder engine
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Old 03-21-2014, 10:03 PM   #24
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Default Re: Tapping into MB factory installed aux battery

That "non fuse" bar is direct + to aux.
There is also a 12v aux only outlet under the hand brake.
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Old 03-25-2014, 12:24 AM   #25
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Default Re: Tapping into MB factory installed aux battery

And what gauge wire do I need from the aux battery takeoff to a DC distribution box? For starters, to temporize for our upcoming Death Valley exploration, we'll only have a fridge, a few lights, and a few cigarette lighter plugs.

Thanks
John
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Old 08-25-2016, 09:08 PM   #26
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Default Re: Tapping into MB factory installed aux battery

I have a 2015 2500 Sprinter with Aux Battery(110)amp/hr Underhood..Installing 2 lifeline(6v) agm 220 amp hr batteries at Factory site..Can I Jump in Under Drivers seat and power 2000 watt inverter in site in Aux. upfitter PDf. posted by MRDI..Wondering if Factory wiring will handle..Appreciate..
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Old 08-25-2016, 09:14 PM   #27
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Thumbs up Re: Tapping into MB factory installed aux battery

Quote:
Originally Posted by Mrdi View Post
Factory up-fitter manual
Please read my post DrDeYates..Questions on Inverter connection to Factory Aux. Battery..Thanks for All
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Old 08-25-2016, 11:16 PM   #28
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Default Re: Tapping into MB factory installed aux battery

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Originally Posted by jsilver View Post
And what gauge wire do I need from the aux battery takeoff to a DC distribution box? For starters, to temporize for our upcoming Death Valley exploration, we'll only have a fridge, a few lights, and a few cigarette lighter plugs.
Step one: add up all of the currents that will be in use at once.
(a "cigarette lighter plug" doesn't consume power, but whatever you're planning to plug into those stations does. That's what you're supposed to be counting.)
((example: some laptops can draw 100 watts ... so that's 100w/12v= 8.5 amps. Each.))

Step two: measure the distance between the take-off point and your distribution box.
(step two-A: how are you handling the negative lead? Depending upon the Sprinter metal frame, or running its own (equally beefy) cable?
If "its own cable", then multiply the wire distance by two.)

Step three: look at a wire sizing chart and pick the size that will handle that (plus 20% extra)
((if i can re-find one i'm happy with, i'll post it))
The Blue Sea cable calculator does a decent job... at the first page you have to click the "i agree" statement to actually reach the tool.

--dick
p.s. link stolen from DieselFume's "powering large inverters" page
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Last edited by autostaretx; 08-26-2016 at 05:32 AM.
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Old 08-26-2016, 03:31 AM   #29
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Default Re: Tapping into MB factory installed aux battery

Quote:
Originally Posted by DrDeYates View Post
I have a 2015 2500 Sprinter with Aux Battery(110)amp/hr Underhood..Installing 2 lifeline(6v) agm 220 amp hr batteries at Factory site..Can I Jump in Under Drivers seat and power 2000 watt inverter in site in Aux. upfitter PDf. posted by MRDI..Wondering if Factory wiring will handle..Appreciate..
What do you mean by "at factory site" - do you mean you installed the two 6v batteries instead of the 100Ah battery under the hood? If so, you can connect devices under the driver's seat. MRDI's upfitter manual doesn't apply to your 2015. They moved the connection points. Look here for the 2015 version of the body and equipment guidelines (upfitter's manual). Or for pictures, see this post on my blog.

BUT also read about powering large inverters from small batteries. You may be disappointed with the performance of a 2000W inverter from a 220Ah battery. The length and diameter of the factory cables between your Lifeline batteries and the inverter may also create a voltage drop that makes your inverter upset.
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Last edited by DieselFumes; 08-26-2016 at 02:49 PM.
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Old 08-26-2016, 07:24 AM   #30
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Default Re: Tapping into MB factory installed aux battery

Various items below have been covered here and in other posts but to summarize.
* The cable charts are based on "safe" cable size that will be large enough to prevent excess heating of the wire and usually have 2-3% voltage drop for the wire alone. At 12V that is .24V. If you have a large load and a small battery that may have you at the low voltage trip point (inverter low voltage turn off) even at 100% charge. I usually use .1V drop. It is also good to expect about .02V at each connection. If you use your large loads with the engine running, you can tolerate more voltage drop since the alternator will deliver about 14V rather than the battery 12V that will drop even lower with a large load.
* The MB ground and supply lines are 2AWG. That is .16V for 10', .32V if you include 10' of ground wire. I think 2AWG is too small for large loads and doubled up the ground wire on the alternator and the wire to the under hood aux battery.
* In my factory install the wire from the transfer relay to the connection bus bar was about 3' long of 2AWG. Seemed strange for a connection 5" away. I removed this cable and moved all the aux battery source and load connections directly to the transfer relay terminal (with a longer bolt). The changes above removed over .5V of voltage drop with a 120A load.
* At high currents it is important to make sure each connection surface is flat and clean. I've had to flatten and file many lugs to get a flush connection to the bolt or the next lug in the stack up. Cleaning with alcohol or acetone also helps.
* If you make these changes add a 300A fuse at the positive terminal of the aux battery.
* I've used 120A (mostly supplied by the alternator) for over 2 hours with no issues.
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