Solar charging

[Cuppa]

Another possibility which can make a panel appear to be putting out less amps than it is rated for is cable sizing. If too thin you get voltage drop (from the wire's resistance) & consequently less amps. A common trap for the unwary is that automotive cables sizes include the insulation so that, if for example someone needs 6mm2 cable for a certain length & buys 6mm autocable, the size of the copper core in the autocable will only be about 4.5mm2, & could easily account for the loss of a couple of amps output (lost to the cable as heat).I have used 6 B&S (13.2mm2) for a 10metre length to my 300w of portable panels.

[lorrieandjas]

On top of that poor connections, regulators in the wrong position, etc cause losses - and in some cases significant losses. When you're talking 6 amp input and loss of say 1.5 amps then you're already 25% behind the game. Whilst there is science behind it all I think there is also quite an art in having a good setup that suits your needs. On the other hand - sometimes the effort to gain a little isn't always worth it! Depends on circumstances again!

Jas

[mudski]

My next question was. What about voltage drop through cabling? But its been mentioned. Cuppa, thats another thing i know I have to change on my panels. Do you have and recommendations of where and what to buy? Plus is using aligator clips still o.k to use?

[Bloodyaussie]

You lot hurt my head... Mark give me the lowdown when you have figured it all out!!!!!

[mudski]

Yeah it does my head in too. I'm trying my hardest to understand it all.

[Cuppa]

My next question was. What about voltage drop through cabling? But its been mentioned. Cuppa, thats another thing i know I have to change on my panels. Do you have and recommendations of where and what to buy? Plus is using aligator clips still o.k to use?

This link should assist Mudski. http://hobohome.com/news/?p=581 The link has been around for a few years but the needed info still holds true.

You will see that the cable sizing depends upon length & the wattage of the panels. For your 190w & say 10 metres of cable you will need at least 9.5mm2 of copper. This equates to to 6 B&S (or 6 AWG) as the next size up that is readily available. 8 B&S (thinner than 6 B&S) would be ok if you keep your cable run to 8 metres. (Probably what I'd do in your situation)

http://www.engineeringtoolbox.com/aw...uge-d_731.html

You will be surprised how heavy the cable is, but remember it's sizing is about reducing voltage drop, not about it's current carrying capacity. Aim for no more than a 0.3v difference between the output measured at the panel & at the end of the cable.

For the sake of a just a few dollars fitting a 50amp Anderson plug to the end of your cable & to your vehicle (going to battery & regulator) you will get a much better & more secure connection than using alligator clips. Whilst you're at it fit the same at the other end of the cable & to the back of your panel.

Mount the regulator as close to the battery as possible & if you can afford it, get one that has temperature compensation, preferably via a probe that goes to the battery. Even more important if the battery is somewhere subject to extremes, like under the bonnet, & the regulator elsewhere.
Not sure I'd want to put a regulator under the bonnet, so would need to include the distance of cable between battery & regulator in the total distnce of cabling from the panels when working out cabling size. If you just went with 6 B&S it may be a bit of overkill, but you'd be sure you had things covered.


Because of where I live I buy most of my stuff online. Ebay is my friend. eg. http://www.ebay.com.au/itm/10-METRES...ht_1223wt_1342

Haven't used them but Jay-Dee in Bayswater have all you need & a downloadable catalogue. http://jaydeeautocables.com.au

I bought genuine Anderson plugs after hearing stories of premature corrosion on the connectors of copies (Genuine have a silver coating). Corrosion will give head scratching problems if it becomes a problem.
http://www.ebay.com.au/itm/ws/eBayIS...ht_4649wt_1108 2 pieces per connection.

Cuppa

[mudski]

Cuppa your a champ. Your going to regret answering my questions as you know more will come. Actually, this was the reg I saw on Ebay to get : http://www.ebay.com.au/itm/370555699...84.m1423.l2649 I was just going to remove the crappy one off the back of the panels and put this one in its place. So I should really mount the reg actually in the car? What if I wanted to use the panels on a totally independent battery? Had plans on putting a third battery in a box in the trailer so the fridge or light could run off that too if needed.

[Cuppa]

You've heard the old saying 'Oils an't oils'.
Well MPPT aint MPPT. The effectiveness of MPPT depends very much on the charging algorithms used & different manufacturers have different ideas about this. There is a reason why Blue Sky regulators cos 10 times what that Wellsee one costs, & even the Blue Sky ones aren't perfect.

My view is that buying a cheap MPPT regulator is that it's not a great idea, & that you would be better off buying one without MPPT, just with PWM instead (Pulse Width Modulation). Now we are gettin to terms that start to challenge my understanding so I wont try to explain these terms.

Suffice it to say I've heard others who know more than me advising to avoid the Wellsee units, & have read of folks that have been disappointed with them.

For the kind of money you are talking about spending the following two regulators are ones that I know of. One that I've used, & one that a number of people I know have used, both succesfully over a number of years.

http://www.ebay.com.au/itm/Solar-Con...ht_5736wt_1342

http://www.ebay.com.au/itm/SOLAR-REG...ht_3425wt_1342

Both have readouts which are useful in giving you an idea of whats going on.

Yes mount the regulator as close to the battery as possible. A mate of mine (with the 2nd of those two regulators) used his panels to alternately charge batteries in his bus & in his trailer. His solution was to have the regulator attached to the end of the cable to the panels, inside a box with a perspex window, which lay on the ground, with a short cable going from it to anderson plugs on either the bus or the trailer (& then directly to the battery). The alternative is to use 2 regulators , one for each location. I have the Steca version of the first regulator. It has always falsely under read battery voltage by 0.3v but has been reliable & consistent & has temperature compensation, albeit not directly at the battery. The first one has a battery temperature probe & talks of protection against battery overheating but doesn't say it has temperature compensated charging.

Cuppa

[mudski]

How much of a difference, really, is it going to be having the reg mount on the panels rather than closest to the battery? Never mind that question. Probably a lot considering we are only talking about 190W so every little bit would count hey.

[Cuppa]

Egg zactly.