Solar Regulators, Installation etc.

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iandvl
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Solar Regulators, Installation etc.

Post by iandvl » 07 Apr 2017 09:18

Knowledgeable peoples - I need a little advice...

Just a short question regarding installation of solar regulator and similar.

I have a BL portable power pack. It's generally installed in the vehicle only when I'm on my way somewhere and I need to power my fridge. It's currently installed, as I'm waiting for the go ahead for my Malawi trip.

When travelling, it charges off a thick (and properly fused) cable running to the boot of the car. This works fine in most touring situations (ie: River trip, Lesotho, similar), as the vehicle runs for long periods of time during the day and the battery has a chance to charge satisfactorily. It also works well at powered campsites, as I can plug the fridge into 220V, and put the battery on charge.

The potential issue comes with non-powered camp-sites, and since I'm planning one for next year, I'd like to get my rig sorted.

I obtained a 140W solar panel from "Johannes van die See" sometime quite a while ago.

Solar panel has a nominal amperage of 8.6A. However, in cold conditions, or limited gain, this will increase quite a bit. The maths is W/V, so that is 140W / 12V. In other words, max amperage in sub-optimal conditions would be 11.6666-odd A. I decided to over-engineer a little, and opted for a Victron Blue Solar MPPT 75/15 (http://www.bushpower.co.za/products.asp?pid=690). Their MPPT calculation spreadsheet (available for download from https://www.victronenergy.com/support-a ... s/software) also indicates that my choice is satisfactory, as max / min power and performance conditions fall well within thresholds.

I will be mounting my regulator onto the lid of my existing portable power pack, and will be running the outputs from the solar regulator directly to + and - of the battery inside.

The solar panel will connect to the input for the regulator via Brad Harrison plug. The one question I have deals with fusing. The regulator has a fuse, but I worry about shorts on the line from the solar panel (for example, let's say someone slams the door on a cable whilst it is connected).

Is it necessary to fuse the cable coming in from the panel ?

Edit: Forgot to mention: both panel and regulator also include a "Short Circuit" max current rating. Does this mean that it is self correcting ? ie: Should a short circuit occur, the regulator and panel will detect this once the max short circuit current is exceeded and shut down until it is rectified ?

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Re: Solar Regulators, Installation etc.

Post by TijmenvdS » 07 Apr 2017 12:16

I have not built a solar system yet but have built a dual battery system, as a general rule one would like to have a fuse as close to a power source as possible be it alternator, solar panel or battery to limit the amount of damaged in case of a short. But if the panel has short circuit protection there is probably no need to worry. :mytwocents:

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Re: Solar Regulators, Installation etc.

Post by iandvl » 07 Apr 2017 12:38

TijmenvdS wrote:I have not built a solar system yet but have built a dual battery system, as a general rule one would like to have a fuse as close to a power source as possible be it alternator, solar panel or battery to limit the amount of damaged in case of a short. But if the panel has short circuit protection there is probably no need to worry. :mytwocents:
Thanks for the feedback. I always ensure my stuff is fused at the power source - I'm relatively OCD about that. :rolling: :rolling:

I've read a ton of documentation regarding this. Hopefully I have it right now. Details here related to the regulator I have acquired - I'm not sure how other brands / models work.

On the regulator output side:

1: Short circuit protection current is on the output side.
2: This will detect incorrect polarity of the batter, as well as short circuits.
3: This will protect the regulator, but obviously will not prevent a fire should the + and - cable between the regulator and the battery terminals short.
4: So I am going to fuse on the lugs where the regulator output connects to the battery terminals in order to prevent a short in this section from creating any risks.
5: The short circuit fuse on the regulator output appears to be 20A. So I will install install a second 20A fuse where the output lug connects to the +terminal.

On the regulator input side:

1: There is no current on the input side unless the panel is connected. Fuse is unnecessary here.

On the panel side:

1: The panels can apparently be operated in a closed loop (ie: a short state) but it isn't overly good for the panel, and I'm also worried that this creates some form of risk.
2: In short, I'm going to fuse at the pigtail where it exits the panel.
3: Since the maximum calculated output will be 11.6666A, I'll use a 15A fuse.

It's probably overkill, but rather safe than sorry.

I'd still appreciate some input from anybody with a little more experience in this. :biggrin: :biggrin:

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Re: Solar Regulators, Installation etc.

Post by iandvl » 07 Apr 2017 13:00

Just had a long phone call from Tinus (dankie mater - ek waardeer die input).

In a nutshell:

Fuse between PV panel and regulator is not required.
Fuse is required at battery terminals (he mentioned 50A).
Regulators do not like the higher voltage provided from the alternator, so unplug the regulator when second battery is charging from alternator.

Will post further explanations, wiring diagrams and photos when I'm done one day.

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Re: Solar Regulators, Installation etc.

Post by iandvl » 10 Apr 2017 09:14

Well, connected all the stuff (temporarily) over the weekend. Wanted to finish the build, but our local shop had no stock of Brad Harrison connectors, and so I just thought I'd do a test run.

Very impressed, actually... My first (serious) experiment with solar, and it works a treat. Amazing concept - generating electricity from nothing...

To test, I connected solar panel to controller "PV". Controller "Battery" directly to battery. I did not connect anything on the controller "Load" yet, as I need moar Brad Harrison plugs....

Not measured amp and voltage output, but with the 140W panel in full sunlight, I was getting a very healthy voltage 14.2V onto the battery.
solar1.jpg
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Even with the panel in full shade, there was enough ambient for it to push a voltage of 13.7 to the battery. As mentioned, I didn't test output Amps, but this voltage is theoretically more than the minimum require 13.6V required to charge a 12V battery. In short, it probably will not be able to carry any load, but it would theoretically allow one to recharge a battery (although that may take very long - depending on A).
solar4.jpg
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Still work in progress, will post more once I get Brad Harrisons and have some time to finish building this stuff.

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