Thread: Rewire D2 TD5 Aux Battery

Thought I’d research solar and try to calculate my usage.

I have a Waeco CF60, according to the stats it uses 0.83 amp/hr @ 32 degrees Celsius. Also I have a few fixed LED camping lights (4 in total, maybe 10w each, a 7.5 amp fuse runs all at once with no issues). According to the REDARC Solar calculator website I’m using a max of 87ah/day. (Using all the lights for 4 hrs - more than needed).

So my existing Kings 160W 8 amp folding panel should be more than enough. It’s a folding panel so I could permanently mount it to roof rack with aluminium. Would 1/2 of the panel be enough? That’d be 80W 4 amp.

Otherwise Kings have a 110W 6 amp panel on sale now for $140 delivered

Unless you are isolating the aux battery when driving so only the solar panel is charging the battery, I'm not sure it is worth fixing the panel to the roof. I guess if you were to have the panel charging while the car is parked, alternator when driving, then have a plug in portable panel when camping it would work well.

Originally Posted by Jazzman

Unless you are isolating the aux battery when driving so only the solar panel is charging the battery, I'm not sure it is worth fixing the panel to the roof. I guess if you were to have the panel charging while the car is parked, alternator when driving, then have a plug in portable panel when camping it would work well.

Not sure if you could isolate the aux when driving as I need to charge it with the alternator via the Piranah. Panel charging while parked is the idea

Just thinking, if I wired it like the circuit diagram, wouldn’t the VictronConnect sense that the alternator is charging >13.5v and cut the panel charging? Then when the car is off the VictronConnect would sense a drop in voltage and recommence charging?

I'd suggest there's a much simpler way to do it, but it involves removing the Pirahna and installing a Redarc SBI12 VSR instead.

If the cost of the 150A relay/solenoid switch plus additional wiring etc is going to cost you anywhere close to about $130, then the Redarc option will cost the same doing with the same features.

Obviously the solar panel and reg for it would add more cost, but for about $130 odd you can simplify your wiring diagram by an order of magnitude!

When you say the solar is wanted more so for the charging whilst parked up, is that more about the long term element or just to maintain a trickle whilst camped?

Assuming the solar reg can detect the voltage then not output to the battery and isolate itself. Then it will work. However 150A is not enough to start your car, you should check the current rating of a start solinoid, I'm not sure what they're rated at. Keep in mind start solinoids will fail if held on for too long. Constant duty solinoids are designed to be held on indefinitely, or at least to a specific duty cycle.

Originally Posted by Jazzman

.... However 150A is not enough to start your car, you should check the current rating of a start solinoid, I'm not sure what they're rated at. Keep in mind start solinoids will fail if held on for too long. Constant duty solinoids are designed to be held on indefinitely, or at least to a specific duty cycle.

The way I'm 'reading it' with the jump start assist switch:

The idea isn't to start the car primarily off the aux, the aux battery simply assists the start battery if the start battery is marginal.

That is, if the solenoid is 150A, then a maximum of 150A will be drawn from the aux battery(probably less), but because the starter system is wired via the start battery then all the primary power required for the starter will come from it. The power via the relay/switch is just additional.

This feature is not an ideal way to jump start, if compared to proper 500A jump cables and whatnot, but in some situations(ie. freezing cold morning) glow plugs required, car might need just that little more oomf to spark up immediately .. the feature woks fine.

But if the main battery is dead(as I had a few months back) then as you say .. that 150A limit will come into play.
To start my Tdi in that situation(start battery dropped cell) I had to pop bonnet, disconnect start battery earth lead, use jump cable from Aux to start battery(just the +ve lead) and she got going.

Hi John, reading through your posts I reckon you could be over complicating the issue here.

Firstly lets look at what you've got. You've got a D2 with a dual battery setup with a Piranha dual battery management system and you're happy with its operation. You want to add an emergency start system, by this I assume you mean the ability to connect the aux. battery across the main/start battery to start the vehicle should the main/start battery be flat ? You also wish to be able to connect your existing 160 watt fold-able solar panel, or other panel to charge the aux. battery. You have a Waeco CF-60 fridge, some LED lighting and have a camper trailer with a Victron solar reg with Bluetooth control access. Sound about right ?


OK ................ There's a couple of things to clear up first which should make it easier to come up with a suitable and simple solution.

Firstly your fridge. Waeco give power usage in the electrically meaningless term of amp hrs/hr, even more confusing when incorrectly quoted as amps/hour, in this case 0.83 amps/hr. This refers to a theoretical average battery capacity discharge of 0.83 amp hrs every hour whilst the fridge is connected with the thermostat set at +5 degrees C and with an ambient temp of 32 degrees C. It is unclear if the moon should be 'in the 7th house and Jupiter aligned with Mars' to meet this criteria.

In the real world your CF60 has a 45 watt BD35 compressor so draws around 3.5 amps when running. Its actual power usage will depend on a number of factors but a good 'rule of thumb' is to work on a 50% duty cycle so an average current draw of about 1.8 Amps. As I said this can vary widely but for dimensioning purposes a pretty good starting point.

Also in the real world your 4 LED lights, unless they're flood lights are unlikely to use 10 watts each. LED light manufacturers often quote a power level that has nothing to do with the actual power consumption of their LED light but the equivalent power consumption of an incandescent globe producing the same amount of light. Crazy but true, there's no hard and fast 'rule of thumb' here to determine the actual power consumption, apart from actual measurement. I use 50% for light bars and anything from 10% to 25% for smaller LED lights when 'dimensioning' a system.

It should also be noted that your solar panel output of 160 watts is a capability not a given. With a folding panel lying on a car bonnet or the ground, perhaps partially shaded at times and in the hot sun an average capability of producing half of this power would be a more realistic figure. This gives a 'best case' figure of around 6 amps @ 13.5 volts. The TD5 alternator is rated at 120 amps so is a much better source of power whilst the engine is running than your solar panel.

With a roof mounted panel problems can arise when connecting to a vehicle battery also being alternator charged at the same time. With a fully charged vehicle battery(s) the solar reg absorption/bulk voltage can fool the alternator voltage reg into sensing over voltage and shutting down the alternator output as a consequence. With small roof mounted panel(s) there's really no need to connect them into the charging system whilst the engine is running.

Considering the above I'd offer the following KISS solution.

Keep your existing dual battery DBE150S managed system as it is. Connect a high current manual battery isolate switch between the two battery positives to give you your 'emergency start' option.

Option 1.
If using your foldable panels and assuming you have an Anderson connector on the rear of your vehicle to connect the main/start battery to the camper trailer mount an additional Anderson connector connected to the aux battery in the rear of the vehicle.
With the solar panels mount the solar reg at the vehicle end of the solar panel power cable with another Anderson connector on the reg output.
This setup will allow you to a/. connect the portable solar panel reg output to either the vehicle battery via the Anderson connector on the rear of the vehicle or b/. the aux. battery via the Anderson connector in the rear of the vehicle or c/. into the camper trailer via the Anderson connector lead into it.

A simple solar reg with a built in voltmeter like this, whilst not MPPT, will do the job. I wouldn't bother with the Victron bluetooth setup as IMO a simple voltmeter is really all you need here.

PROJECTA - SC010 - 10A 12V Solar Charge Controller 2 Stage Automatic 9315219010100 | eBay

or one of these

Solar Charge Controller 20A MPPT PWM Solar Regulator 12V IP68 Waterproof Model | eBay

with one of these stuck to it

Mini Blue LED Digital Display Volt Monitor Voltmeter DC 12V Voltage Gauge MA1005 | eBay

Option 2.
If you go with a roof mounted panel mount the solar reg under the bonnet and connect one side of the solar regs solar panel input via the normally closed contacts of a change over relay activated from the ignition. This automatically disconnects the solar panel from the solar reg when the engine is running and re connects it when the engine isn't running. Don't switch the solar regs battery connection as it needs to be connected so that the reg can operate, the last thing you want is for the panels to be connected to the reg with no battery connected as this can damage the reg.

I'd go with Option 1 as its simpler and more versatile than option 2.

Deano

Thanks for the replies Guys. DeanoH, ur post was too long to quote my reply in! So...

Emergency start: Currently only get 1 attempt at starting my TD5. I don’t know why, it just is. So if I muck up my start I pull out my jumper leads and connect them and start the car. It does work fine I was just looking at a more drivers seat option so I thought of a solenoid with a push switch. But the more I read the answers the more I think that I might just keep my current setup.

Solar: I have 3 Anderson plugs on the rear. 1 from the alternator that powers the camper trailer fridge (jayco swan outback with a 3 way fridge) while driving. There’s a motion switch on the fridge to cut it out if parked for longer than a few minutes. The other 2 are both wired to the aux battery via 3b&s cable. 1 is a 50amp and the other is a 120amp. The 120amp powers the camper battery, the 50amp was wired in so that I could connect the folding panel. The main idea for the roof mounted was to ‘simplify’ things a bit. The 160w folding does take up a lot of space and I thought that a roof mounted might be easier. Again, the more I read the replies the more I think that maybe the best option is to buy a more compact panel and plug it into the rear 50amp Anderson. I’m not concerned about the batteries while driving, just while parked for longer than overnight as the aux is only 55 or 60amp optima style of battery.

So, if I keep on this line of thinking and just go with a more compact panel, what wattage/brand/style should I go for?

I can always add the 160w to the camper roof giving me a total of 420w up there.