I know this subject has been covered to death but I don't know what you do regarding the OEM relay. So my van had the 2nd battery and I am planning the electrics going forward, I am going to put a lithium under the driver's seat hopefully and use the OEM wiring. So what do you do with the original relay? Leave it in place and just attach your dc-dc after that or do you need to remove it? Also where is the OEM ign wire I need? I'm sorry if this seems a stupid question or completely obvious to most people but I don't get it yet!
Swapping from OEM 2nd battery to dc-dc. What to do with the VSR / relay
- Thread starter Toffermora
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I'm considering the sane by replacing the OEM second battery for lithium so watching this one.
I guess there’s nearly as many ways to do it as there’s tinkerers around
, the needs for the setup vary quite a bit.I removed the relay and took power feed away from it’s socket and attached it to bus bar, from there onwards to dc-dc via smaller fuse. So: main battery -> 100A fuse in ebox -> 80A fuse under seat -> bus bar -> 30A fuse -> dc-dc.
The ign feed is the one that drives the relay. I just left it to it’s place and took it from relay socket to dc-dc charger by a spade connector - see photo.
And this is T6 with OEM second battery.
Yeah, exactly, just remove the relay, and the DC-DC is almost an exact replacement with the addition of a ground feed. The input (i.e. from starter) goes to the input of the DC-DC, the output (i.e. to leisure battery) goes to the output of the DC-DC and the signal wire goes into the 'ign' or signal feed of your DC-DC - all with appropriate fusing...
Ok thanks that makes sense I think! I will have a look at what I have and see if I can figure it out. Another question, how can I check I am receiving a current from the starter battery, I checked the 80a fuse and it is fine and then I checked across the positive and negative of the battery connections but my multimeter didn't register anything. Would it only show if the auxiliary battery was actually connected or does it only start charging after a certain time/ when certain criteria have been met?
OEM relay connects the batteries when engine is running. So the relay feed is not really ignition live, more like engine run signal.
Also, T6 smart alternator is not charging your main battery all the time, only when needed, so if it's not charging you will not see charge voltage in aux battery either.
To test, do the following:
* Start the car
* Turn on main beams and fan on full to force lot of consumption, this should force smart alternator on
* At this point, you should measure 14.6 - 15.0V on the main battery (full charging) or around 13.4 - 13.8V (float). The point is if it's >13V charger is doing it's thing.
* Since the relay just connects the batteries together you should also get the same voltage on second battery. If you do, all is good.
Also, T6 smart alternator is not charging your main battery all the time, only when needed, so if it's not charging you will not see charge voltage in aux battery either.
To test, do the following:
* Start the car
* Turn on main beams and fan on full to force lot of consumption, this should force smart alternator on
* At this point, you should measure 14.6 - 15.0V on the main battery (full charging) or around 13.4 - 13.8V (float). The point is if it's >13V charger is doing it's thing.
* Since the relay just connects the batteries together you should also get the same voltage on second battery. If you do, all is good.
Brilliant thanks will test that tomorrow! Thanks for all the help!
In my previous T5 with OEM 2nd battery, I put the B2B charger inline with the factory relay. So the relay fed the input of the B2B, the B2B fed the battery. Worked perfectly. When I sold the van, I removed the B2B & put the relay output back onto the battery.
i used the existing main feed and relay signal and swapped those out for a DC-DC. ( same as above)
i had this:
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www.t6forum.com
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i swapped the relay out for MIDI fuses:
and used the relay Engine run feed to switch the DC-DC:
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www.t6forum.com
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i then fitted a MIDI fusebox for power distribution:
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lifepo4 battery wise, you can then fit any you want:
as long as your DC-DC charger has the Lifpo4 charge profile.
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once that's sorted - get your monitoring on.
www.t6forum.com
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i had this:
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Stop/start...regen...smart Alternator... Dc-dc Charger For Leisure Battery Or Not?
So With all the talk regarding the Bluemotion thing and regen breaking and leisure batteries our T6 has finally arrived. The first thing we done was to checkout the factory fitted setup,...... Stop/start=check, Regen Braking=check, AGM starter battery=check leisure battery under passenger...
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i swapped the relay out for MIDI fuses:
and used the relay Engine run feed to switch the DC-DC:
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[Guide] DC-DC Charger (for leisure battery) -- How I Done It --
DC-DC Charger (for Leisure battery) -- How I Done It -- ************************************************** Dellmassive`s -- "how I Done It" -- Thread ************************************************** Kit List And Stuff -- How I Done It & What I Use --...
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i then fitted a MIDI fusebox for power distribution:
++++++++++
lifepo4 battery wise, you can then fit any you want:
as long as your DC-DC charger has the Lifpo4 charge profile.
LIFPEO4:- Lithium Lifepo4 12v Batteries -- Time For An Upgrade ? --
- Valence U27-12XP Lifepo4 Lithium Battery -- How We Done It --
- SUBZERO - low temperature lithium battery -- How We Done It --
- Roamer LiFePO4 Gen2 230Ah Seatbase battery -- How I Done It --
- 12v Lithium Leisure Battery Box 138Ah 1766Wh -- How I Done It --
- Awesome-3-in-1-battery-bank -how-i-done-it.
- SOLAR GENERATORS - LifePo4 Battery Boxes -- How I done It --
- 200Ah, 2000W, LifePo4 Leisure Battery Box -- How I Done It --
- Renogy - 12V 100AH Lifepo4 BATTERY W/ BLUETOOTH RBT100LFP12-BT-UK
- Renogy 12V 100Ah SMART LiFePO4 Battery RBT100LFP12S
- RENOGY 12V 100AH SMART Lifepo4 BATTERY W/ SELF-HEATING FUNCTION
- Poweroad 100Ah Lifepo4 LowTemp Battery
- Xmas Lifepo4 Battery SoC Drift
- Cold weather, Lithium batteries, Victron Shunt and a false SOC reading.. . . . Cold weather GOTCHA to be aware of.
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once that's sorted - get your monitoring on.
Battery Monitoring -- How I Done It --
Battery Monitoring -- How I Done It -- Part #1 Battery monitoring is a very important part of your 12v system . . . . whether its just the vans starter battery or your leisure setup keeping an eye on the power in your battery bank will keep you from breaking down and make sure your weekends...
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Thanks for the info @Dellmassive with the engine run feed are you saying you need to change the setting in VCDS to get it to work?
So just checked this and it seems I have an issue somewhere. Lights on, fan on, I get 13.6v on starter battery but aux battery is showing 12.3v. Relay fuse I tested the other day by sticking my multimeter into continuity and putting the probes on the terminals and it works. So will it then be the fuse under the starter battery?
No it will work, no VCDS reqd if you have it from factory.
It switches +12v we engine running.(and drops to 0v when engine off)
You can use it as the IGN feed for your dc-dc.
Take the relay out of it's socket and measure the socket pins. One of them should be 13.6V - if so, your ebox fuse (under starter battery) and the cabling is good. If not, then it's time to go under the main battery - it's not really very difficult but inconvenient and takes time. You'll want to check other stuff first.
If you see 13.6V on relay socket then the problem is either the relay, the 80A fuse or the wiring to the second battery.
Edit: and oh, measure the engine run signal as well (blue wire in my photo above), the relay will not work unless it goes to >12V when engine running
The large pins are input from starter battery and output to second battery, I don't remember which one is which but one of them should have >13V when charging. And the pin blue wire connects to is the run signal from BCM, which should be >12V always when engine running.
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So I get 12.4v from the relay. And 14.12v from the run signal. So fuse must be ok, but why is it a low voltage? Or is that because it was just with the engine running and the alternator hadn't kicked in. Maybe I need to try again tomorrow with lights etc working.
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Hmm, what about the other large pin? 12.4 sounds like aux battery voltage, and that’s what you should be getting from aux battery pin of the socket. 14.2 from run signal is good, we now know BCM and coding are ok
The OEM connections are: main battery positive -> ebox 100A fuse -> relay -> 80A fuse -> aux battery positive. So… if you have 0 in one of the larger pins of the relay that would point to either a blown 100A fuse in ebox or a cut wire between ebox and seat base (or both).
But… one more thing to check before taking main battery out: where did you get the ground when measuring? It’s possible the connection between aux battery negative and vehicle chassis is bad and if you used aux battery neg as a multimeter negative it would throw measurements off. Check the resistance (better than just continuity check) from aux battery neg to chassis is close to 0 ohm. It’s probably best to do this by running a temporary wire from main battery negative close to the seat base and re-measure everything using that ground as a reference. Nothing fancy, just as thick as wire you have at hand routed externally, eg a jump start cable would be great but any wire will do.
WARNING: I would disconnect both battery negatives when checking resistance: measure wires, not battery poles - if the connection is indeed bad it could put quite a burst of current through the meter.
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If you end up having to open the ebox, it will look something like in below photo. The aux battery fuse is either third or eighth(?) from left, the latter from memory. There’s few different vehicle configurations.
To get there:
To get there:
- Remove main battery terminals
- Remove the plastic dividers between battery space and engine
- Remove main battery
- Remove main battery base plate
- Open the small fuse box in left side of the battery space and release the fuse carrier (lift and slide to side afair)
- Remove the large plastic ebox cover that was under battery all the way to headlight and the small fusebox
So checked the efuses and yep 3rd one has blown. I probably did it when I first got the van and wasn't really thinking about what I was doing and disconnected the aux battery and touched the positive terminal against the seat or floor! Are they just standard midi fuses? If so will get one ordered and replace that and hopefully that will sort it!
Cheers for all the help, fitted a new fuse today and all working again now! Can start looking at fitting my dc-dc charger now!
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