Solar System 2-Battery System - trickle engine battery?

[Scylla]

I have a mppt pro which will charge a leisure battery and the engine battery.. does anyone know if I can connect the engine battery to the second battery connections on my 16 plate T6 highline

 

[Dellmassive]

got some pics of what we are looking at?

 

[Scylla]

I want to connect the engine battery to my solar controller. I k iw how to do it but want to know if it will cause any issues with engine management...

 

[Dellmassive]

this one . . ? 15A Dual Battery Solar MPPT Pro Charge Controller

New MPPT Pro delivers superior charging rates for solar-powered caravans, motorhomes and boats

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The PV Logic MPPT Pro is a compact, 15A solar charge controller with unique single or dual battery charging capabilities. The device can increase the charging capability of any 12V or 24V solar panel (up to 220W) by as much as 20% per day through its ability to map the voltage from the solar panel to suit the condition of the battery. With built in Bluetooth technology, the MPPT comes with free Apple and Android apps to provide remote access to charging data via your mobile phone. The simple-to-read dashboard clearly displays the live solar panel charging status and the charging current/voltage in the connected batteries.

TECHNICAL SPECIFICATIONS

Nominal System Voltage 12/24VDC (automatic system voltage recognition)
Battery Voltage Range 11-36V
Rated Battery Current 15A
Self-consumption ≤24mA
Over Voltage Disconnect Voltage 16V/32V
Charging Limit Voltage 15.5V/31V
Equalize Charging Voltage 14.8V/29.6V
Float Charging Voltage 13.8/27.2V
Operating temperature -35oC to +55oC
Overall dimensions 150 x 85 x 40mm
Mounting hole size (in case) 3.8mm
Terminals 6mm2
Net weight 220g

https://www.kuranda.co.uk/index.php?route=product/download/download&did=139

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Nice looking controller that . . . . . . . and twin battery banks too..

@andys have you seen these before? - i wounder why Victron hasn't got a dual battery option yet?


It should be fine on the T6, just note the normal safety rules for cables size and fusing.

connect the starter battery #2 output to the starter battery positive via a 20A fuse next to the battery.

connect the Aux battery to #1 output to the leisure battery positive (has priority over #2 until 70% soc) via a 20A fuse next to the battery.

Use body ground as the 0v earth for both #1 & #2 ( that way you wont bridge out the power monitor on the negative terminal of the starter battery. the install guide shows the 0v going direct to the battery - but there is no need for this)

.



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[Scylla]

Thanks for your reply Andy... yes it us a nice controller not cheap but wirth it.. it's also a good app to will help if I have any issues in the future... I 1st saw this two weeks ago at the nec motorhome show a company was doing a demo of the controller and solar panel.... the who system with this controller was £440 the panel is marine quality with cables exiting under neath and is black to match my poptop....

Here is the solar panel



Bought the system from these guys Solar Technology International Ltd

Very helpful ..ordered on a friday delivered on the following Tue I had to ring them as the package I wanted wasn't on there web site . But a very helpful lady called Helen sorted me out... 1st class service

 

[True Romance]

Why do you want to charge the engine battery?

 

[Dellmassive]

Why do you want to charge the engine battery?

dont forget on extended offgrid camping stays . . . . the doors,lights,alarm etc etc are fed from the starter battery. . . .

so if you are opening the doors a lot during a long weekend/week you can get a low starter battery - especially if you have the front lights come on/off as well, also every time you unlock the door all the modules power up.

some people run the van for a while to top up the starter, (alternator)

some people use EHU to charge the starter,

some people use mobile solar to charge the starter, (me @Dellmassive )

some people use a B2B trickle charger to charge the starter, (@andys )


so short weekend stays are fine if you have a good starter battery, but a long weekend plus if not driving the van may cause you some issues.

 

[Scylla]

Why do you want to charge the engine battery?

Why not the solar controller has the facility... and if there is spare free solar energy why not......

dont forget on extended offgrid camping stays . . . . the doors,lights,alarm etc etc are fed from the starter battery. . . .

so if you are opening the doors a lot during a long weekend/week you can get a low starter battery - especially if you have the front lights come on/off as well, also every time you unlock the door all the modules power up.

some people run the van for a while to top up the starter, (alternator)

some people use EHU to charge the starter,

some people use mobile solar to charge the starter, (me @Dellmassive )

some people use a B2B trickle charger to charge the starter, (@andys )


so short weekend stays are fine if you have a good starter battery, but a long weekend plus if not driving the van may cause you some issues.

Thanks for your reply it's just what I was thinking... free spare solar power might as well be captured....

 

[True Romance]

Just a question that was all. Never had any issues with the main battery running low even on long weekends. Guess no harm if you have free solar.

 

[Phil_G]

The dual-battery controllers I've seen have had a common neg, one terminal of which will already be grounded for the leisure battery, so you may only need run the 2nd battery pos. Running a neg directly to the starter battery as per the diagram above would bypass the current sensor, easier to just ground it at the controller if negs are not common-grounded in your controller.

 

[Scylla]

The dual-battery controllers I've seen have had a common neg, one terminal of which will already be grounded for the leisure battery, so you may only need run the 2nd battery pos. Running a neg directly to the starter battery as per the diagram above would bypass the current sensor, easier to just ground it at the controller if negs are not common-grounded in your controller.

Thanks for that

 

[andys]

Yes I use a Votronic trickle charger (just a current limiter) off the load output of my Victron solar controller. Piece of mind thing really as I sometimes camp many miles from anywhere, but also useful to keep both batteries in a a good state of charge as my van is not my daily transport and can go unused for weeks at a time. I have a 250W panel so I have plenty to spare

 

[Scylla]

Yes I use a Votronic trickle charger (just a current limiter) off the load output of my Victron solar controller. Piece of mind thing really as I sometimes camp many miles from anywhere, but also useful to keep both batteries in a a good state of charge as my van is not my daily transport and can go unused for weeks at a time. I have a 250W panel so I have plenty to spare

Andy ....Did you run a positive and a negative cable to the engine battery

 

[andys]

Andy ....Did you run a positive and a negative cable to the engine battery

No. The grounds are all commoned to the chassis anyway. It’s one of these Votronic 2A 12V DC to DC battery to battery trickle charger / standby charger fo 5060297344077 | eBay

just sits between the solar load output and + feed to/from the starter battery. The Victron is programmable to only output once a set voltage is reached. Don’t know why they’re so expensive now, there’s nothing much in there, pretty sure I paid £22

Edit: No I paid £27.99

 

[andys]

As usual I haven’t read the thread properly before answering, your setup will be different. Follow what @Dellmassive said, he is the resident solar expert!

 

[Dellmassive]

Lol...
That's a joke. £45!!!!!

I'm sure there cheaper elsewhere.?

Votronic 2A 12V DC to DC battery to battery trickle charger / standby charger fo | eBay

If you crack open the case you will find one diode and one resistor.........that's it!!!!

You can make the same for £2

It's just a diode to stop verse current flow and a current limiting resistor, ..... when the aux voltage is higher than starter current will start to bleed over upto the max rate of the limiting resistor and will rise the starter battery voltage up to the same as the aux feed minus the 0.6v drop across the diode. So it's kinda working like an unregulated low mA trickle charger.

These are certainly not chargers in the modern sense ..... but can work in some circumstances..,


Just be warned, be educated, know what ur buying,
dont get ripped off!!!!!

 

[Scylla]

Lol...
That's a joke. £45!!!!!

I'm sure there cheaper elsewhere.?

Votronic 2A 12V DC to DC battery to battery trickle charger / standby charger fo | eBay

If you crack open the case you will find one diode and one resistor.........that's it!!!!

You can make the same for £2

It's just a diode to stop verse current flow and a current limiting resistor, ..... when the aux voltage is higher than starter current will start to bleed over upto the max rate of the limiting resistor and will rise the starter battery voltage up to the same as the aux feed minus the 0.6v drop across the diode. So it's kinda working like an unregulated low mA trickle charger.

These are certainly not chargers in the modern sense ..... but can work in some circumstances..,


Just be warned, be educated, know what ur buying,
dont get ripped off!!!!!

Thanks for the info... any idea where I can get my wire through the bulkhead from cab to engine... realy struggling to find a grommet

 

[Dellmassive]

Yeh . . . . . you can pickup a main starter battery feed from the rear of the center console fuse box, but most people prefer to go direct to the starter battery(prob best option).

But basically, under the cab floor mat to the center cable tunnel, up behind the glove-box, via grommet that comes out in Plenum chamber behind starter battery. (remember always fuse at any battery)

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There is also a VW resource here > Tpi 2046279, T6 Repair Instructions For Voltage Supply Of 2nd Battery


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From @Loz Installation Guide for Redarc DC-DC Charging Kit

Second battery wiring diagram

VW T6 Fusebox - Fusebox/Fuse Chart SA - Primary Battery Fusebox


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RECOMMENDED INVERTER CABLE AND BREAKER OR FUSE SIZES

Installing 12v Socket /s - How Its Done -

Ignition Live Under Passenger Seat - How Its Done -


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@travelvolts has some great guides over here > https://www.travelvolts.net/shop

like this one > https://8f5d4f75-0e78-4b9a-99dd-bb2...d/d959f6_4e84b63f4383484ea1097894b235b0fe.pdf

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Dellmassive`s -- "how I Done It" -- Thread

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[andys]

Lol...
That's a joke. £45!!!!!

I'm sure there cheaper elsewhere.?

Votronic 2A 12V DC to DC battery to battery trickle charger / standby charger fo | eBay

If you crack open the case you will find one diode and one resistor.........that's it!!!!

You can make the same for £2

It's just a diode to stop verse current flow and a current limiting resistor, ..... when the aux voltage is higher than starter current will start to bleed over upto the max rate of the limiting resistor and will rise the starter battery voltage up to the same as the aux feed minus the 0.6v drop across the diode. So it's kinda working like an unregulated low mA trickle charger.

These are certainly not chargers in the modern sense ..... but can work in some circumstances..,


Just be warned, be educated, know what ur buying,
dont get ripped off!!!!!

Agreed, I didn’t realise til afterwards, I’d definitely make my own next time

 

[Dilbert]

If you crack open the case you will find one diode and one resistor.........that's it!!!!

The manufacturers quote it has a current range of 0-2A. That implies a current limiting circuit.

Or are they just saying that they have a 7.5 ohm resistor so a a 15.6V leisure battery (worse case) to a 0V completely flat start battery (worse case) would result in 2A flow.

That would however result in 30W of heat that would need dissipating and a large 30W resistor. Something doesn't stack up between the hardware and the spec. You can make other assumptions about max and min voltages of course but there must be something more to limit current to 2A in that case.

Like to see the inside of one of these........