Keep Aux battery in system...or not?

Mendobob

2014 144" WB 4cyl
You *can*, and lots of people *do* but it's not clear from Mercedes whether you *should*.


To run thick enough cables between the driver and passenger seat base, it's likely that you'll need to remove both seats and bases so that you can unclip the top on the plastic cable race cover that runs between them. Or run the cables out from the boot under the driver seat, under the van, past the exhaust pipe, and up in to the passenger seat base. You'll then have to route your cables, create a battery tie-down location, and find a way to vent the battery to the outside world (through the floor). It's not clear that you'll actually gain anything by doing that.

If you're going to that hassle, why not do something like a Sterling battery-to-battery charger and install a proper deep cycle battery of a size that's more appropriate?


As soon as you go to a larger "house" battery, solar starts to make more sense. The more charging you do from solar, the less the alternator has to make up. I'm sure people will shout at me that the alternator is basically free power, but if making it work harder than its design parameters means it burns out faster, then that's not really free. Also, solar works whenever the sun's out, rather than relying on you driving the vehicle.

You have brought us some excellent things for me to think about. Doesn't sound like placing the battery under the passenger seat is easy/and or energy efficient. Plus Espar D2 might go there.

Is the Sterling battery to battery charger similar to what Terrapin mentions he is doing in his post? That plan makes a lot of sense.

Another Idea: Would it be a descent plan to isolate two systems. Use the Aux for LED phone charging and maybe Espar. Then when I install the Fridge and solar - install a new AGM house battery dedicated primarily to the fridge.:hmmm:
 

DieselFumes

2015 4x4 2500 170 Crew
Is the Sterling battery to battery charger similar to what Terrapin mentions he is doing in his post? That plan makes a lot of sense.

Another Idea: Would it be a descent plan to isolate two systems. Use the Aux for LED phone charging and maybe Espar. Then when I install the Fridge and solar - install a new AGM house battery dedicated primarily to the fridge.:hmmm:
You can read more about the DC-to-DC charger and your other battery charging options here. Basically, the Sterling takes power from your engine battery (or batteries) and makes sure it gives it out to your house battery at the correct voltage and current to charge the house battery properly. The Sterling can be set for different battery chemistries from wet cell through AGM and lithium based.

Your idea of keeping the house system isolated from the vehicle system is exactly what we did. We have the aux battery (wouldn't have ordered it given the choice) and we use that for charging small stuff. We have a completely separate house system. The house system runs our lights, Espar, fridge, and then via an inverter it also heats our water and powers our microwave and induction cooktop. We could (theoretically) pull the whole house system out of the van and it would still work. We aren't even charging from the van.
 

Mendobob

2014 144" WB 4cyl
Y We aren't even charging from the van.
Is there a reason NOT to use a DC- DC (sterling power system) along with a few panels of solar? Seems like a win win way to go.

And if I was to have this kind of set up, is there any reason why I could not draw off the Aux battery (light load) in addition to the house?
 

DieselFumes

2015 4x4 2500 170 Crew
Is there a reason NOT to use a DC- DC (sterling power system) along with a few panels of solar? Seems like a win win way to go.
Price? I think lots of folks decide that adding an extra battery with some 2/0 cable is cheaper than using the Sterling. If you've got the money for the Sterling, I'd do that in preference to a direct connection.

And if I was to have this kind of set up, is there any reason why I could not draw off the Aux battery (light load) in addition to the house?
Nope.
 

Mendobob

2014 144" WB 4cyl
Hi Mendobob,
I have the factory Aux battery. I use it to charge the house battery bank (375 amp) through a dc to dc charger. The owners manual says you should not pull more than a 40 amp load from the factory aux battery, so I got the 40 amp model. It doesn't make for a really high speed recharge while going down the road, but it does give the house batteries a true 3 stage charge. We typically use about 30~40 amps each day and the system has worked flawlessly for 3 years now.
Basically, the Sterling takes power from your engine battery (or batteries) and makes sure it gives it out to your house battery at the correct voltage and current to charge the house battery properly.
I am trying to wrap my head around this electrical stuff and feel like I am getting shocked. Total head spin. However, it is beginning to sink in some and make some sense - but I have a long way to go to fully understanding how things work.

Can anyone give me a hand in how the wiring would go with the Aux and the House batteries in separate loops. I think I would like to use alternator to charge the House battery (in addition to the Factory Aux and Starter batteries). Solar will top off the house when available and when the van is not being run. I have attached a rudimentary diagram.
 

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dknightd

New member
I'd use your aux battery for now. And perhaps use it in the future as well. For now I'd put in a subpanel to feed your lights, phone charger, and espar wired to existing aux battery. When you decide you need more capacity, I'd add a dedicated house battery bank. And maybe move the espar to it, and put any additional lighting, and secondary charge points on it. You can put solar on your existing aux for now, and move it it to house batteries in the future. When I put in proper house batteries I would wire them into existing starting and aux batteries with a big switch and 1/0 cable. That switch would usually be off. It would be used only when I needed to start van from house batteries in an emergency. It might also be used when I was at home and connected to a charger so all batteries could be charged. This gives you lots of redundancy, and options. You have the starting battery to start the van - you'd have a small aux battery for small loads - one day you might have a big house battery for bigger loads. Instead of (or in addition to) switches you might consider heavy duty jumper cables. This would let you jump start your van from another vehicle.
 

Jackies Dog Grooming

2016 NCV3 144" 4 banger
I am trying to wrap my head around this electrical stuff and feel like I am getting shocked. Total head spin. However, it is beginning to sink in some and make some sense - but I have a long way to go to fully understanding how things work.

Can anyone give me a hand in how the wiring would go with the Aux and the House batteries in separate loops. I think I would like to use alternator to charge the House battery (in addition to the Factory Aux and Starter batteries). Solar will top off the house when available and when the van is not being run. I have attached a rudimentary diagram.
Your diagram looks about how I'm planning on mine. Except instead of a DC to DC converter, I'm thinking of doing an inverter to AC/DC charger to house battery bank. I beleive I've read it charges faster and more efficiently. But we'll wait for the gurus.

Also, I "think" there should be some sort of isolator relay needed between the house battery and the DC/DC converter to allow the house batteries to charge from either the solar OR the converter independently. Again, I'm not 100% sure about that. But it seems to me that a converter is one direction power flow.
 
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GeorgeRa

2013 Sprinter DIY 144WB, Portland OR
If I would be doing another conversion I would take a serious look at CTEK option for solar and an alternator charging. Inertiaman and Hein and others are using them, search this forum, it seems as it becomes a trend. I believe that Hein purchased a kit which includes some additional stuff.
http://www.ctek.com/hu/en/chargers/D250S DUAL
http://www.ctek.com/hu/en/chargers/SMARTPASS
http://www.etrailer.com/Battery-Cha...tml?feed=npn&gclid=COCgxMCRl9ACFYdcfgodp1QE2A

For shore power charging you can use either just a charger or an inverter/charger combo.

George.

http://smartercharger.com/products/batterychargers/100a-off-road-charging-system-package/ - additional monitor
https://sprinter-source.com/forums/showpost.php?p=497397&postcount=18
https://sprinter-source.com/forums/showpost.php?p=497401&postcount=19
 
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GSWatson

2013 144
I have the CTEK system and am pretty happy with it; about the only thing that would be an improvement is if the MPPT could handle panels higher than 22 volts. Other than that, it's been good so far.


Sent from my iPad using Tapatalk
 

Mendobob

2014 144" WB 4cyl
If I would be doing another conversion I would take a serious look at CTEK option for solar and an alternator charging. Inertiaman and Hein and others are using them, search this forum, it seems as it becomes a trend. I believe that Hein purchased a kit which includes some additional stuff.
http://www.ctek.com/hu/en/chargers/D250S DUAL
http://www.ctek.com/hu/en/chargers/SMARTPASS
http://www.etrailer.com/Battery-Cha...tml?feed=npn&gclid=COCgxMCRl9ACFYdcfgodp1QE2A
Thanks so much George! The Ctek route helps alleave my headache! This gives me some great ideas and better options.
 

Mendobob

2014 144" WB 4cyl
If I would be doing another conversion I would take a serious look at CTEK option for solar and an alternator charging. Inertiaman and Hein and others are using them, search this forum, it seems as it becomes a trend. I believe that Hein purchased a kit which includes some additional stuff.
http://www.ctek.com/hu/en/chargers/D250S DUAL
http://www.ctek.com/hu/en/chargers/SMARTPASS

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I have modified a diagram from CTEK to approximate my situation with the Auxillary battery, is this close to coming right?:thinking:
 

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GeorgeRa

2013 Sprinter DIY 144WB, Portland OR
I have modified a diagram from CTEK to approximate my situation with the Auxillary battery, is this close to coming right?:thinking:
I am not expert with CTEK but I think that the service battery is your auxiliary battery. See attached diagram. Shunt is for a battery monitor such as Victron (preferred by many) or Xantrex.

George.
 

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kcshoots

VanTripping.com
Hi MendoBob, a lot of good suggestions and info in the posts here. I'm planning to use my factory Aux battery to power a couple of minor loads by connecting those into the factory 12V outlet circuits, and power the vast majority of my loads off of my house battery system, while using the Aux battery relay to automatically connect the house battery to the alternator for alternator charging. That connection and the redundancy of the Aux battery to the starter battery are the main purposes of my factory Aux battery. Being a data center guy, I like starter battery redundancy. In my current van I use an ACR to manually connect the house and starter battery for this functionality.
 

DieselFumes

2015 4x4 2500 170 Crew
I have modified a diagram from CTEK to approximate my situation with the Auxillary battery, is this close to coming right?:thinking:
Yes and no. You probably only want to have the house/service battery charge from the engine when the ignition is on. That means connecting it to the starter battery side of the aux relay rather than to the aux battery. Otherwise, the house battery will try to charge even when the ignition is off. It will run your aux battery down really quickly.

That might be what you meant when you added the aux battery to that diagram, but right now it looks like you're running the SmartPass from the aux. Not good!

When you move that connection point, your non-critical consumers also move. They go back directly to the Aux battery rather than to the non-critical connection point on the SmartPass.

I'm really not sure what that does for solar charging of your aux battery. The solar will charge the house battery, and it will charge the starter battery. I don't know whether it would also trigger the stock Mercedes aux battery relay to close and charge the aux battery or not.
 

Mendobob

2014 144" WB 4cyl
I'm planning to use my factory Aux battery to power a couple of minor loads by connecting those into the factory 12V outlet circuits, and power the vast majority of my loads off of my house battery system, while using the Aux battery relay to automatically connect the house battery to the alternator for alternator charging.
Hi KC - So how do you plan to connect the Aux battery to the House battery? And where does this occur? Off the AUX relay under the Drivers seat (photo taken by Dieselfumes http://sprintervanusa.com/)?
 

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Mendobob

2014 144" WB 4cyl
Ok - I've changed the diagram to reflect your suggestions.


I'm really not sure what that does for solar charging of your aux battery. The solar will charge the house battery, and it will charge the starter battery. I don't know whether it would also trigger the stock Mercedes aux battery relay to close and charge the aux battery or not.
Yep - my concern too - it is hard to know what the heck can happen with so many electronic/computer components.:crazy:

thanks for your help
 

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Mendobob

2014 144" WB 4cyl
Ar you planning to have 3 battery banks:
1- Starting
2. Auxiliary
3. House?

George.
Yes Thats the dilemma. 3 batteries.

Leave Starter alone.

The stock MB Aux battery is under hood already in place. I want to use the Aux just for LED and fan (currently hooked up for that now - so leave that the way it is) and other light loads like USB.

And the Addition - put in a House battery for heavier drains like refrigerator and Espar D2. I would like to be able to charge the the new House battery with solar power for when we are dry camped (and not moving) and the Alternator when the we are driving.
 

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