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Discussion Starter · #1 ·
Hi all:

I have the factory auxiliary battery with the EK1 connector. I have read here that DIY upfitters (like me) have added a fuse block near the auxiliary battery (with 2/0 Gauge 00 AWG battery cable) under the driver's seat to access the aux batt power. OK, I get it, I can do that easily enough.

But I can't believe Daimler sells an auxiliary battery with a relay and NO FREAKIN' ACCESS POINT!

Does anyone understand this? There must be some fused access to the aux. battery, no? Thanks
 

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Just to be clear, I did NOT have a factory installed auxiliary battery- I added a Trojan AMG battery as an auxiliary power source.

But when I was researching the Metris and its aux battery I too was confused by their lack of a circuit panel for that battery.
 

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Discussion Starter · #4 ·
Just to be clear, I did NOT have a factory installed auxiliary battery- I added a Trojan AMG battery as an auxiliary power source.

But when I was researching the Metris and its aux battery I too was confused by their lack of a circuit panel for that battery.
Me too!
 

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I guess I am missing something. Your concern is that you had to add your own fuse block for tapping off of an auxiliary battery intended for use by professional upfitters?

Maybe I am completely missing the issue because I am so used to just taking whatever is present and making it work.
 

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Discussion Starter · #6 ·
I guess I am missing something. Your concern is that you had to add your own fuse block for tapping off of an auxiliary battery intended for use by professional upfitters?

Maybe I am completely missing the issue because I am so used to just taking whatever is present and making it work.
Yes. It makes even less sense not to have a block for an auxiliary battery intended for professional upfitters.
 

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Discussion Starter · #8 ·
I mean seriously. The big three even offer factory switches to control upfitter equipment.
Couldn't agree more. If I could get it in my garage I might look at a trade for a 2020 Transit with the 2.0l diesel.
 
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I think we might be talking about 2 different levels / concepts of electrical up fit.

I might be wrong, but this is my perception of how the electrical systems in the Metris operate:

The Metris and 4 cylinder sprinter vans have heavily managed alternators. This aggressive alternator management, along with other features allows the Metris to have a very good combination of driving performance and fuel economy. You might even refer to its operation as "very mild hybrid" in nature.

The battery under the passenger seat's primary function is to support this "very mild hybrid like" operation. This results in fairly large swings in voltage and current, making it largely useless as a place to tap in for any power at all - at least that is my interpretation of the body builder guide.

The "auxiliary battery" that MB puts under the drivers seat is not really the first place that you can use to tap in for 40 amps / 450 is watts, and that is really mostly when you are driving. 400 - 450 watts is equivalent to:
- a couple of 12 volt and USB outlets
- Some light duty laptop chargers
- Perhaps a light duty 1/4 inch drill.
- Definitely not enough power to run a decent size 12 volt compressor refrigerator for a 3 day camping trip.

Let's for fun call this battery under the driver's seat "aux battery 1".

_________
 

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________________

In the auxiliary power systems that conversion van / upfitters install, the customer expectations are a bit higher.

A very minimalistic / survival level auxiliary power system has:
- a dedicated 150 - 200 amp-hr capacity
- 1 kW inverter
- Able to easily run a 12 volt refrigerator for 2 days - or indefinitely with some solar and vehicle power input.
- Able to run a coffee pot OR most power tools OR any laptop / common entertainment
- CPAP overnight
- Operate the lights and exhaust fan(s)

A mid range system has:
- At least 400 amp-hr of very good batteries
- 2 kW inverter
- Able to easily make breakfast of coffee, toast, fried eggs and sausage
- Blow dry hair after a shower
- Operate the light(s) and exhaust fan(s)

In electrical up fits like this, the "aux 1 battery" and "solar" are viewed as sources to tap into in order to charge up the "real" auxiliary battery pack.

We don't actually "use" the MB aux 1 battery as an auxiliary battery. It is used as the official approved location to obtain 25 - 50% of the charging power for the "real" auxiliary batteries.
 

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In vans like a transit or promaster, the electrical system is not really operated in this "very mild hybrid like" mode. Slightly, but nothing nearly as aggressive. The typical transit or promaster have 6 cylinder engines and as options you can have fairly powerful alternators. In some cases 2 alternators.

The ability to pull power from these various brands of vehicles varies by brand and detailed option configuration. For people like us doing electrical up fits, we spend a lot of time figuring out what is officially allowed, as well as what people have done that works / doesn't work.

Adding features to your own vehicle can be done as you see fit. Doing up fits on someone else's vehicle requires a bit more caution for obvious reasons.

Each vehicle / van design approach brings strengths and trade offs. The Metris brings a great combination of vehicle size / capacity features but not a particularly strong electrical system. These trade offs that exist in all vehicles are why there are a large number of up fitters around the world.
 

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Sorry, in post #9 where I wrote:


"The "auxiliary battery" that MB puts under the drivers seat is not really the first place that you can use to tap in for 40 amps / 450 is watts, and that is really mostly when you are driving. 400 - 450 watts is equivalent"

_________
Should actually say:

"The "auxiliary battery" that MB puts under the drivers seat IS really the first place that you can use to tap in for 40 amps / 450 is watts, and that is really mostly when you are driving. 400 - 450 watts is equivalent"

In the mid size auxiliary power units, I also use mine for running a circular saw and a cross cut saw.

Sorry for adding this - could not figure out how to edit my original posts.
 

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Discussion Starter · #13 ·
Should actually say:

"The "auxiliary battery" that MB puts under the drivers seat IS really the first place that you can use to tap in for 40 amps / 450 is watts, and that is really mostly when you are driving. 400 - 450 watts is equivalent"

In the mid size auxiliary power units, I also use mine for running a circular saw and a cross cut saw.

Sorry for adding this - could not figure out how to edit my original posts.
BEST WRITE UP YET -- thanks much Harry!

So should I add a third battery? or dare I try and add a Lithium battery. 1/2 of 95 amp hours ain't going to cut it. Must have 12v fridge or it's not an RV!
 

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BEST WRITE UP YET -- thanks much Harry!

So should I add a third battery? or dare I try and add a Lithium battery. 1/2 of 95 amp hours ain't going to cut it. Must have 12v fridge or it's not an RV!
That is exactly how I have done it. I connected a Sterling battery charger to the aux battery, and then connected the Sterling to a 100ah Battleborn brand lithium battery. The Sterling has settings for lithium, so it works just fine. Seems to keep the fridge running for 3 days from the lithium battery. The aux battery runs the rest of the stuff like lights, phone charging, carbon monixide alarm, etc.
I also have an 80watt solar panel to charge the aux when sunny. The Sterling is connected directly to the aux, since it has its own fuse. I added a fuse box between aux and “the rest of the stuff”.
 

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Discussion Starter · #15 ·
That is exactly how I have done it. I connected a Sterling battery charger to the aux battery, and then connected the Sterling to a 100ah Battleborn brand lithium battery. The Sterling has settings for lithium, so it works just fine. Seems to keep the fridge running for 3 days from the lithium battery. The aux battery runs the rest of the stuff like lights, phone charging, carbon monixide alarm, etc.
I also have an 80watt solar panel to charge the aux when sunny. The Sterling is connected directly to the aux, since it has its own fuse. I added a fuse box between aux and “the rest of the stuff”.
Thanks Imants -- just what I needed. Now all I have to do is sell one of my kids to get the $1k for the Li-ion battery. No, seriously, it is comforting to find some with the same setup. One more Q: Do you have the EK1 Body Builder connector and do you use it? I'm having a hard time on what to use it for, except my Rydeen side view cameras (once those get installed)
 

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BEST WRITE UP YET -- thanks much Harry!

So should I add a third battery? or dare I try and add a Lithium battery. 1/2 of 95 amp hours ain't going to cut it. Must have 12v fridge or it's not an RV!
I am happy that it was helpful, and good luck with the project.

12 volt compressor refrigerators and 12 volt powered diesel / gasoline heaters represent a more complex challenge than first appears. In some cases, the low voltage cut off is only slightly less than 12.5 volts "at the refrigerator terminals". It actually doesn't take a very low state of charge for a 12 volt battery to drop below 12.5 volts under some mild loads. If it is cold outside the battery voltage drops a bit more. Combine the two concepts together and trying to get an espar heater to run in the mountains can be exciting.

As if this were not enough of a challenge, add in an inverter load of any size and AGM battery voltage will sag temporarily - even using the best AGMs out there. The result is a very annoying thing - the 12 volt refrigerator will trip off under this low voltage condition - and turn off. Very annoying and I know people who have lost all of their food.

What we do in our smallest system is to wire 2 each x 80 amp-hr Lifeline AGMs together to make a 24 volt system. (same as you would use in a boat or semi truck).

A 24 volt inverter is slightly more efficient than a 12 volt version, so that part is easy.

We feed the "12 volt" bus bar with a 24 - 13 volt DC - DC converter. This maintains the output at 13 volts no matter what loads are being pull (within the design limits of course)

I know it sounds a little bit complicated, but it is super stable under a wide variety of conditions.

If you are handy you can build one yourself.

I am not very good at posting photos, but my wife made an instagram account / wirlnet if you like looking at pictures.
 

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That is exactly how I have done it. I connected a Sterling battery charger to the aux battery, and then connected the Sterling to a 100ah Battleborn brand lithium battery. The Sterling has settings for lithium, so it works just fine. Seems to keep the fridge running for 3 days from the lithium battery. The aux battery runs the rest of the stuff like lights, phone charging, carbon monixide alarm, etc.
I also have an 80watt solar panel to charge the aux when sunny. The Sterling is connected directly to the aux, since it has its own fuse. I added a fuse box between aux and “the rest of the stuff”.
Sounds good. Similarly my son and I put 2 each x 150 watt (nameplate) solar panels on an old dodge minivan - which is remarkably similar in shape to a Metris.

I was initially concerned that it would look odd, but most people think that they are just ski rack equipment, which is very common around here.

Once you hit about 300 ish watts, solar will do most of the work and you might find that the connection to the alternator is only needed in the winter.
 

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Exactly right, HarryN!
My Dometic Cf11 fridge used to cut off on low voltage. And if I set the cutoff voltage lower it would not work properly, it stayed warm...
Now, with the lithium battery, the voltage stays at 12.5 volts until the battery is almost completely discharged, so the fridge stays on a lot longer.
 

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I had thought about getting a ready-built battery system, but ended up buying 8 of the prismatic LiFePO4 batteries from ebay, mainly because the size of these eight fit perfectly under the driver seat (picture 2 below). These eight on paper should deliver about 2kw (90ah for 24v). I then bought a cheap BMS from China and solder the BMS on the battery, connected with a 60A breaker. I secured the whole package with some 8020 along the existing holes on the wall of the compartment. There is a ground point in the compartment, which comes really handy.

I realize there's consider risk buying batteries from unknown sellers in ebay so I am NOT really advocating this route. I took my chance since the cost is reasonable and the size really fits! The 8 batteries came charged with identical 3.4v, so that's a good sign. I have not tested them extensively, other than using it to cook some rice with my 24v rice-cooker, and boil a couple of pots of waters with a 1000w inverter and an induction cook top. LiFePo4 are robust with relatively wide margin of error so I am reasonably comfortable.

For the charging, I installed a Victron 100/15 for solar and a really inexpensive step-up mppt charge controller (MPT7210) for charging from car battery. MPT7210 is a disappointment because I didn't realize it only allows 10a max input. Although the charger works, it charges just 5a to my 24v battery while driving. Both chargers are housed in the back compartment under the passenger seat. I added a couple of switches (for the charger), charging sockets, a XT60 connector, and a 40a breaker on the face panel (picture 3 and 4).

I installed a 24v/1000w inverter in the back compartment under the driver seat. I don't expect needing AC power as I plan all my appliances to be 24v. One of the main advantages going 24v power source is able to drive higher watt appliances without thick cables. I plan to add other AC components (outlets, surge protections, etc) in that compartment later.
 

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