How to fit a DC-DC / battery-to-battery charger kit

[Loz]

This guide takes you step by step through fitting DC-DC charging kit for leisure batteries on factory California.

Why fit this kit:
VW are still installing their standard split charge relay on vehicles fitted with leisure batteries, however, the latest Bluemotion technology has a few undesirable side effects with leisure battery systems.
In order to leave headroom in the starter battery for the surge in regenerative braking the alternator will stop charging when the starter battery reaches about 80% also to improve economy the alternator will at times just idle and not perform any charging.
This can cause current to flow back from the leisure batteries to the starter battery as seen here on the california control panel.


Step 1, Disconnect rear second battery:
These instructions refer to the twin leisure batteries in the California you may not have the second battery.
First open the panel at the bottom the rear wardrobe to reveal the second battery if fitted.

Unbolt the retaining clamp (13mm socket).

Use a large flat screwdriver or trim tool to lever up the battery to get it over the edge of the opening

Now slide out onto the boot floor.

Disconnect the negative terminal (10mm Socket)


Continue to Step 2.

 

[Loz]

Step 2, Remove passenger seat:
Slide the passenger seat forwards and backwards to reveal the 4 bolts holding the seat to the base.

Unbolt the 4 bolts and tilt the seat up to reveal the plugs under the seat.

Slide the black safety catch to allow you to push the yellow catch and release the airbag plug and squeeze the side tabs to release the black heated seat plug (if fitted)


Now remove the passenger seat.

Continue to step 3.

 

[Loz]

Step 3, Disconnect Starter and leisure battery
Remove the negative clamp from the starter battery.

Remove the Leisure battery rubber cover.

Remove the negative and then positive clamps of the leisure battery

Remove the trim at the back of the passenger seat base
Remove the clamp for the leisure battery.

Disconnect the vent pipe from the negative end of the battery and lift out the leisure battery.

 

[Loz]

Step 4, Remove factory split charge relay.
Remove the 2 screws holding the relay to the mounting plate and the 2 screws holding the mounting plate to the seat base.

Discard the bracket and lift up the relay so you can unplug the control plug by pulling out the red slide and then pinching the sides of the plug to remove it.






Take note or mark the supply cables at the bottom of the relay.


Now disconnect the relay.

 

[Loz]

Step 5, Improve the earth to the seat base

Note; If you do not have a battery monitoring system you can skip this step.

Remove the nut holding the seat base to the chassis and remove the paint around the bolt. Fit a locking washer and refit the nut and tighten.


Continue to step 6.

 

[Loz]

Step 6, mount the DC DC charger and parts.

Mark holes for the charger, drill and mount the charger on the side of the seat base towards the rear.
Connect the 2 leisure battery supply cables to the large power post with the Output wire from the Charger, feed all 3 cables up the sleeve of the protection cap, but leave the nut loose for the time being. This is the large brown cable on the Redarc unit.


Connect the main battery supply feed to the midi fuse carrier at the end of the supply cable to the charger. This is the red cable on the Redarc unit.

Now mark, drill and mount the power post and midi fuse carrier so that it looks like this , ensuring the main supply cable is well away from the seat base.


Now tighten up the nut on the power post and slide over the rubber cap. tighten up the nuts on the midi fuse carrier. I also added some insulation tape to the battery supply cable as there was too much bare cable for my liking.

Next I fitted a bolt to the seat base to act as the earth for the charger and connected the earth cable from the charger. As the california has a battery monitor the negative must go directly to the chassis and the reason I improved the earth to the seat base earlier. (If you do not have a battery monitor this cable can be put under the nut of the negative battery clamp)


Next connect the trigger wire for the charger to the relay plug we removed from the relay earlier.


Tidy up and cable tie your installation.


Continue to Step 7.

 

[Loz]

Step 7, refit batteries.

Replace the leisure battery into the seat base and clamp back down.
Connect the Positive clamp to the leisure battery.
Connect the vent pipe
Connect the negative to the battery.
Refit the Rubber battery cover.


Replace the 80A fuse for the supplied 50A fuse;


Now reconnect the negative to the second leisure battery (if fitted) and replace the rear battery reversing the instructions in step 1.

Now connect the negative to the starter battery.
You can test you have a supply to the charger if you want to.


!! Do not be tempted to test the system at this stage as your airbags are disconnected and you will generate a fault you will need cleared.

Continue to step 8.

 

[Loz]

Step 8. Testing;

Rest the passenger seat back on its base.
Tip it to one side and reconnect the yellow airbag plug and the seat heater plug (if fitted)
If you have a california you will need to reset the clock on the camper display unit and then change the display to battery status.

You can now start the engine and check it is charging.

As you can see above the charger is showing profile A and boost mode charging. The camper display unit is showing greater than 20A flowing in.

After running for 20 minutes you can see the charge rate drop.


continue to step 9.

 

[Loz]

Step 9. Finishing up

Bolt the passenger seat back down.
Refit the cover trim to the rear of the passenger seat

Re-learn the auto windows that were lost whilst the battery was disconnected.

Remove sticky sweet from carpet next to passenger seat (you may not have to do this )

Audit your tools and any bits you have left over.

Total time taken 2 hours.

I think this is complete, any questions add below..

 

[Caulkhead]

If the battery is not charging, would it not be better to get your alternator upgraded ?....... maybe this is a silly question, I’m not an electrician

 

[Loz]

If the battery is not charging, would it not be better to get your alternator upgraded ?....... maybe this is a silly question, I’m not an electrician

Its the design of the van not a fault.

 

[Caulkhead]

Its the design of the van not a fault.

But if you did have your alternator upgraded would that still allow it to charge as it would have more power

 

[Loz]

Its already 180A but it is controlled by the BCU and deliberately works like this.

 

[Caulkhead]

Its already 180A but it is controlled by the BCU and deliberately works like this.

Thankyou

 

[Nigel W]

Loz, fantastic post and may I just ask for your thoughts on a similar scenario for an after market conversion?
Mine had a Sargent system installed which, on hindsight, was really not suitable. To get over the problem we installed a Sterling BtoB charger which we fitted under the drivers seat and connected between the vehicle battery and the leisure battery.
The split charge relay is built into the Sargent so we couldn’t remove and for the past months we have been running both side by side. However after reading the very helpful posts on this forum I learned that if I removed the ‘run’ wire connection to the Sargent box then the split relay will not engage. This also enabled the 12volt side of the Sargent box to work when the vehicle was running.
As the system stands at the moment when driving the BtoB charges the leisure battery from the vehicle battery
However when we are parked up and hooked onto mains if I turn on the Sargent charger I can either direct it to just the leisure battery or if I direct it to charge the vehicle battery then that in turn engages the Sterling which then charges the leisure battery as well.
It all seems a bit mad to me so just looking for reassurance.

Thinking about it won’t you have the same issue on a California- putting a charge into the vehicle battery by a mains charger will also trigger the BtoB and charge your leisure as well?

 

[Pauly]

What happened to step 7 ?

 

[Loz]

What happened to step 7 ?

I took it out and forgot to shuffle the number up, but i’ve Done that now..

 

[travelvolts]

Loz, fantastic post and may I just ask for your thoughts on a similar scenario for an after market conversion?
Mine had a Sargent system installed which, on hindsight, was really not suitable. To get over the problem we installed a Sterling BtoB charger which we fitted under the drivers seat and connected between the vehicle battery and the leisure battery.
The split charge relay is built into the Sargent so we couldn’t remove and for the past months we have been running both side by side. However after reading the very helpful posts on this forum I learned that if I removed the ‘run’ wire connection to the Sargent box then the split relay will not engage. This also enabled the 12volt side of the Sargent box to work when the vehicle was running.
As the system stands at the moment when driving the BtoB charges the leisure battery from the vehicle battery
However when we are parked up and hooked onto mains if I turn on the Sargent charger I can either direct it to just the leisure battery or if I direct it to charge the vehicle battery then that in turn engages the Sterling which then charges the leisure battery as well.
It all seems a bit mad to me so just looking for reassurance.

Thinking about it won’t you have the same issue on a California- putting a charge into the vehicle battery by a mains charger will also trigger the BtoB and charge your leisure as well?

Best not to charge the van battery to be honest. It shouldn't need it.

 

[Nigel W]

Best not to charge the van battery to be honest. It shouldn't need it.

I know but I’m one of those oldies who has it parked up for months on end so the batteries get discharged. I aim to charge them up every fortnight or so but am not sure if I’m doing it the right way.
It breaks my heart to see it parked up on the drive but when you get to my age......still it’s summer soon so we will be able to get out and about more.

 

[travelvolts]

Best way round that is to fit a low wattage solar panel on the dash. It will maintain the battery without reaching the switching threshold of the DC-DC charger.