solar panel - semi-flexible with bypass diodes

Submitted: Tuesday, Apr 22, 2014 at 21:07

ThreadID: 107413 Views:4350 Replies:5 FollowUps:3

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Cybermike

Hi all, I'm in the market for a solar panel though I'm not finding one with both these features. It will be propped up on a lead out from a ute-camper - so I like the light weight of the semi-flexible type. However I seek out shade to set up the camper in the intense heat, so having some shade on the panel may be unavoidable (given the limitations of cable length) - hence the need for as many bypass diodes as possible to keep it working in partial shade. Is such a beast made? Cheers.

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Reply By: olcoolone - Wednesday, Apr 23, 2014 at 09:03

Reply By: HKB Electronics - Wednesday, Apr 23, 2014 at 15:46

Reply By: Member - Boobook - Wednesday, Apr 23, 2014 at 16:27

Reply By: Cybermike - Friday, Apr 25, 2014 at 22:56

Friday, Apr 25, 2014 at 22:56

I don't have any cable yet to connect the panels to the controller that will be mounted in the ute, though I like the idea of wiring 2 panels in series to get about 36 volts and an MPPT auto switch controller to provide about 14 volts to the battery. There's many volts available to lose between those 2 figures, so there will be practically no limitation on cable length & I can really chase the sun for the panels while the ute is camped in the shadiest spot available.

Also, there is there any issue with feeding the regulator into a busbar (powering cigarette sockets) in the ute canopy, where there will be approx. 0.2 volt drop to the spiral wound AGM battery under the bonnet?

Regards, Mike.

AnswerID: 531228

Follow Up By: HKB Electronics - Saturday, Apr 26, 2014 at 13:39

Saturday, Apr 26, 2014 at 13:39

Always better if regulator is mounted as close to the battery as possible, in your case as long as the cabling can handle the charge current a .2V drop is workable.

Cheers,
leigh

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Follow Up By: Member - John and Val - Saturday, Apr 26, 2014 at 15:29

Saturday, Apr 26, 2014 at 15:29

Mike,

A few misconceptions here. An MPPT controller takes the available voltage, draws sufficient current to load the panels down to their optimum power voltage, then converts that voltage down to what the battery requires. An MPPT controller doesn't discard the excess voltage - it effectively uses the energy it represents to generate extra amps. "There's many volts available to lose between those 2 figures" - No! In fact voltage losses between the panel and controller not only waste energy, they upset the operation of the controller. Losses are less critical on the panel side of the regulator, but best minimised anyway.

There are a few (very few) MPPT controllers around that will accept higher panel voltages, but most for 12V battery charging are intended to interface with panels that have an unloaded voltage of about 23-24 and a maximum power point at about 17-18 volts.

There are advantages in series connection, but also a there's a downside. The power output of series connected panels is governed by the panel with lowest output. So a bit of shading on one panel affects the power supplied by all panels. With a parallel connection that shading only affects the one panel.

Cheers

John