Intro and solar Q's

Hi and a hello to all forum members. I had been searching for help with my car/solar panel related problem and came across this site, it was only after I had registered I realised it was primarily focused (no pun intended) on torches (I am from the UK) or 'flashlights'. I decided to continue as it sems you have some solar savvy members so perhaps I will get the answer I seek?


I wil give as much info as possible so the forum massive can make an educated reply.

So, I have a 4x4 Land Cruiser that I use for camping it has twin batteries, one is used to start the vehicle the other is used to power camp lighting and run a fridge, at this point assume I have the correct marine grade batteries and all the changeover and charging automation sorted.


Normally when camping there is a roof rack with a rigid solar panel fitted, this panel is quite old but continues to give it's rated output. The specification of the panel is:


Power 110W
Current
Short circuit: 7.5A
Current rated: 6.6A
Voltage
Open circuit: 20.7
Rated: 16.7

**Open Max System voltage 600V?** More about this spec later.



This is put through a 10 amp controller which keeps both batteries when camping topped up and my fridge working OK. Recently I have been going out without the rack and 'getting by' and keeping the trips local. Going out without a fridge is not an option so I have decided to purchase a flexible panel (or perhaps two depending on space) and glue it/them permanently to the roof of the car. The versions I have seen have the following spec:


Peak power: 100W
Maximum power voltage: 17.8V
Maximum power current: 5.62A
Open circuit voltage: 20.8V
Short circuit current: 6.02A
Power allowance range: +/- 5%


When the roof rack is fitted and plugged in I intend to use the pair in parallel, I will of course only get a limited supply from the stick on panel as it will be covered by the roof rack but something is better than nothing.


The first question I have is, I am thinking I need to add diodes between the panels to stop them feeding each other when one is in the shade, and the next question is that I am unsure of the above spec on my old panel **600v**? I am assuming this is when they are in series?


I am 12v savvy but do not want to screw up an old panel that I have had for years.


Many thanks in advance


regards


Dave

75 views and no replies? Did I choose the wrong sub forum?

Now have an answer which I will share with you. It seems the panels probably have diodes anyway and, if the guy at Maplins had more knowledge he would have shown me an alternative type of diode capable of handling 16amps. So make sure the person serving you knows their stuff.

regards

Dave

Your panels shouldn't need diodes, Also diodes can make them less efficient.

I would make sure you have the most efficient solar controller you can get. Keeping the panels clean, and using high quality connectors and wire. All to maximize the efficiency of the whole rig. Make sure your controller is a MPPT style.

Depending on what flexible panel you have, if they are covered by the roof rack, you may not get reduced output, you may get significantly reduced output. Many flexible panels, even though they may be thin-film based, are stacks of large thin film cells. If you shadow 50% of one cell, then the total output is 50% less. A roof rack could certainly do that .... and more.

You don't really need diodes to parallel. The panels will settle at some balanced level where their I/V curves match with the battery.

If you could find an inexpensive MPPT charger, that gives you another 25-30% on the single panel which may be enough.

Semiman