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k3vin

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Jan 6, 2014
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Location
Canterbury, NSW
Hi Guys,

I just wanted some feedback and recommendations.
I was looking at purchasing this to power my deep cycle:

http://www.australiandirect.com.au/...battery-automotive-wiring-kit-plu/KADBWK8MMPP

What I was wondering tho was, do you guys think it will be okay to have a double anderson adaptor at the end of this were ones connection goes to my deep cycle and the other would be used for my compressor?

I can see the cable used above is rated at 59.2A. With my compressor its maximum is 40A.

Or would I best run a another set of cables to be able to run my compressor from the back?

Cheers,
Kevin
 
The big caveat is how the cables are rated.

6sq mm cable is rated as "60A" but even carrying 7A the voltage drop over just 6m of cable is enough to cause a voltage-sensing circuit in a fridge to call a fully charged battery "flat". In this case, 60A would refer to "the most current it could carry before the insulation started to melt".

21sq mm cable (6mm across) is rated at a couple hundred amps but in reality can only handle 56A without getting warm (at all).

So the starting question is, just how large is the actual conductor in that cable?

The next consideration is this: no matter how big the cable diameter, it's going to have a lower voltage on one end than on the other. It's inescapable. If the only thing between your cranker (charged by the alternator) and the aux battery in the back is that cable, then the battery in the back is going to have LESS charge than the cranker up front. Since the cranker is usually only charged to 75-80%, you should not count on more than this available on the aux battery. The terrible result is that if your aux battery should only be drained to 50% of its capacity, you're left with 30% of its rated capacity as usable (best case scenario) - so a 100Ah aux battery can really only supply 30Ah, which will run an Engel fridge for around a day and a half (if that's the only thing connected).

If you have a DCDC charger (CTek D250S, Redarc 1240D) you will overcome this problem. Both units have automatic isolators. Both take solar inputs in addition to the vehicle feed. Both will (rapidly) bring the aux battery to 100% charge.

As for the compressor, it depends on what kind of battery you have as an aux battery. Some deep cycle batteries don't like having large quantities of current drawn from them - the starter battery doesn't mind, as long as it's topped back up soon after. As for the cable to the compressor - same caveat. If it's too thin (regardless of whether or not the supplier rates the cable as 40A or higher) it will get warm during extended use and may melt the insulation between the conductors.

Personally (and I don't make exceptions because I don't like being stranded) I'll use either of my batteries - because my aux battery is an Optima D31A that can deliver 900CCA (my starter is a 910CCA Century) but I only ever use the cable supplied with the compressor and I never, ever extend it.
 
As always Tony, thank you very much for your advice mate, really appreciate it.

I will be going DC to DC for the aux battery once all done. I was just trying to think of a way to not need to pop my bonnet every time to pump up the tyres and mount my air compressor in the tub.
 
With the right battery in the back you can do just that.

Now that I'm thinking about future choices ... I'm wondering what some of the newer (non-lead-acid) choices are going to be able to deliver. Can you run a compressor from LiFePO4 for the half hour it takes to reinflate your car's tyres after a visit to the dunes? There are other new techs on the way, like a battery that is recharged by filling it with more water.

The next few years are going to be very interesting.
 
Bloody hell that's a good price for an AGM batttery. Their website does have at least one inaccuracy in it - AGMs can be stored at any angle, but not because they're VRLA - it's because the electrolyte is held in the glass matting between the plates, there is no free-flowing acid in it anywhere. Gel batteries can be treated the same, because the acid hsa had a gelling agent (silicate usually) added to it to form a jelly that stays between the plates. Unfortunately for gels, that's also their achilles heel - if a bubble forms in the jelly it's all over!

Good choice of battery. If I was in need of a replacement right now, that'd be the one I'd buy too.
 
Hi Tony,

Sorry to bring up an old thread, but just wanted your thoughts on something.
My solar panels already have a regulator attached, but I've recently purchase a Projected DC/Solar Charger.

Would there be any issue with me connecting it to the solar input on the Projecta unit? Ie. essentially going through 2 solar regulators?

The reason I don't want to cut and re-crimp a new anderson on the solar panels to bypass regulator is in case I need to one day connect directly to my starting battery.
 
Don't worry about bringing up an old thread, it's quite relevant to this question so it's a good spot for it.

Generally you don't use two regulators. A solar regulator expects its input to be coming from a solar panel (for a 12V panel, this is around 17-22V depending on cell count, photon strike angle, crystalline matrix (poly/mono) and panel age. The same regulator expects a battery to be connected to its output.

If you introduce a second one, its input will be around 14V (typical charge voltage is around 14.4-14.7V for a flooded/AGM battery). The first regulator won't see a battery (batteries have "surface voltage" and internal resistance) and the first regulator might not even deliver power at all. If it does, the Projecta unit should try to make the most of what it has, but that's going to be reduced from what the system is capable of.

Is the first regulator mounted on the panel itself? If so, why not introduce a heavy duty switch in the side of the regulator to provide direct/regulated output?
 
Hi Tony,

Thank you for the feedback. I've attached a picture of the current solar panels.

I see what you are saying about a switch, good idea, I think I might just do this. Now to find a switch slim enough to fit inside the panels when folded.

Cheers,
Kevin
 

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You can buy those plugs that go from the panels to the regulator fairly cheap, so you could always get a couple of them (mc4 I think) and make up a new lead that goes to the projecta. That way you can bypass that regulator easily and just hook it back up when required...
 
The switch will be easier still if you grab a project box that will fit between the two panels and pass ALL of the wiring in there (both solar feeds and the output of the regulator). Will need to be a DPDT switch. These have 6 pins, 3 on each side. Pick a side and number the pins 1, 2, 3 from top to bottom and on the other (in the same direction call them 4, 5, 6.

Straight away pins 2 and 5 (the centre row) are your outputs that you can connect the existing wire+Anderson plug to.

Pins 1 and 4 (top row) get connected to the two solar panels directly AND to the regulator (so there'll be 3 wires on each of these).

Pins 3 and 6 (bottom row) get connected to the regulator's output.

So, when the switch is in pressed towards the bottom row (activating the connection between the top row and centre: power flows from solar panels to the Anderson plug directly. It also flows to the regulator but nothing is done with that.

Flick the switch and power flows into the regulator (because it's connected directly to the panels) and the regulator is connected to the Anderson plug.

Any 20A DPDT switch will do.

You could simplify it and use a SPDT switch, knowing that you must have an actual circuit for power to flow, but this nicely isolates everything.
 

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