Battery and power setup... A couple questions...

gatorlee1

Member
In my ncv3 I have an agm starter battery and an agm aux battery. At first i wasn't sure if they were connected, i assumed they were separated by an isolator.

I got two series 27 wet cells and installed them over the back passenger tire.

Using 2/0 awg (approx. 24 feet) welding cable connected from the aux battery to the wet cells in the back and all in parallel to a cobra 2500 watt inverter.

I measured all batteries with a multimeter and they're all connected, the starter battery is not isolated.

I have everything connected to a bayite voltmeter and everything looks pretty good.

I am thinking i should probably isolate the starter battery, but then i noticed how fast the alternator actually changes up those batteries, so i began to question this need?

If the need is there, i was looking at the blue sea 7611 ACR but it's a bit pricy for a solenoid and was wondering if there's a cheaper yet effective option?

Any critiques are welcomed.

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autostaretx

Erratic Member
It would be fascinating to learn what datacard options you have (enter your VIN at https://www.datamb.com/ )

In theory, any MB-supplied Aux battery will have an isolator relay under the driver's seat.

This is what it should look like under there, with item (1) being the isolator, and item (2) being the "authorized spot to attach wires"



It's possible the isolator has welded its contacts and is providing continuous connection.

Another quick test would be to disconnect the negative quick-disconnect near your pedals (the one for long term storage).
That should remove the starter battery from the game .. and the dashboard 12v outlet should go dead.
If the dash 12v outlet does NOT go dead, then "yes" the isolator is not isolating.

--dick
 

gatorlee1

Member
Awesome information here!

It does look like there is an auxiliary battery isolator relay under E36 of the VIN specifications.


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sprint2freedom

2008 NCV3 170ext
I am thinking i should probably isolate the starter battery, but then i noticed how fast the alternator actually changes up those batteries, so i began to question this need?
The purpose of an isolator would be to provide you a reserve (the starter battery) allowing you to avoid running down your batteries too low and being unable to start the engine.

You shouldn't see a significant change in charge rate with/without the isolator relay connected. The only difference will be that you don't discharge your starter battery when the engine is off.
 

gatorlee1

Member
Is it possible to access that control panel without removing the driver's seat?

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alexk243

KulAdventure
I would highly suggest an isolator. A lot of them come with a "forced connection" switch which would allow you to connect all the batteries to assist in a start, if needed. The cheapest way is a 12v contentious heavy duty solenoid (https://amzn.to/2Gda99Y) connected to a switch or a D+ line. As others have pointed out this is important to keep the starter battery from wearing down when using accessories with the van off.

A more expensive but hand off and no D+ or switch needed is something like this: https://amzn.to/2GrFllh or the high amp model I use: https://amzn.to/2GbpGXU which are nice because they detect charge and discharge states on both batteries. Nice if you leave the van on a maintainer/charger when parked and want it to charge all batteries.

Here are some pics of my battery combiner setup.
 
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