Solar Panel Blowing Fuses?

[newhaul]

A 30 amp/ 400 watt controller would be even better then a 30 amp fuse at the battery end of the run best. IMO. YMMV

[svlamorocha]

Originally Posted by newhaul

A 30 amp/ 400 watt controller would be even better then a 30 amp fuse at the battery end of the run best. IMO. YMMV

I agree that the controller is not up to the task but the fuse close to the battery to protect the fat wire from shorts is ALWAYS necessary. This is fire safety, not just protecting the controller.

[svlamorocha]

Originally Posted by MapleSugarMan

Hi Everyone,

Thanks so much for taking the time to write your responses.

A few other details that folks have asked for:
The controller is a Solar Pro Plug 'n Play rated for 21 amps max.
The panels are 140 watt Nature Power brand by RDK.
Wire from the panels to the controller is 20 feet @ #8 (Recommended by the manufacturer of the controller.)
Wire from the controller to the master switch is 2 feet @ # 10 or 12 (permanently installed by the manufacturer.)
Wire from the switch to the batteries is (I think) # 4 or 6 battery cable. :

Wires are fine, only subject to checking voltage drop in the #4/6 that we do not know the length of.

Do you have the controller described in the attachment? That seems to be a basic cheap 1-stage "cut-out" controller. This even more basic that a PWM controller. Forget my suggestion of connecting in series; that will not help with this controller.

If/when you want to get a better controller, consider spending US$107 in a Victron MPPT 75/15 that is much better for what you have. It will let you run both panels in series; it will extract more Ah per day from those panels; and it will keep batteries at absorption voltage for a reasonable time.

Do not assume that the controller needs a 20 amp fuse to protect itself. Many controllers specify a fuse with a rating that is bigger than the published rating of the controller (at which the fuse should not blow). For example, the Victron 75/15 MPPT controller is rated to handle 15 amps of current to the battery but the internal fuse is a 20A fuse.

If you replace fuseholder and install 25A or 30A fuse close to the switch end of the #12 wire that will protect that wire (ampacity 31.2A asumming 105°C insulation outside engine space, per table VI-B of ABYC E-11) from current coming fro the battery, which is the big issue. The question is whether that is fine with the controller, but that is not very likely to be an issue.

If I guess correctly from the manual that this is a "cut out" controller that cuts out (instead of keeping voltage constant) when the battery reaches absorption voltage, then your batteries will not charge in full. I suggest that you check voltage at the battery terminals over time before and 30 miniutes after the moment when the LED turns green. If voltage stays at 14.4V then you have a 2-stage controller. If it drops to below 13V then it is a basic cutout controller that is not good for the batteries.

Ignore the fuse at battery end (sized for the fat wires it protects or smaller) at your own peril. MRBF fuse blocks are cheap.

[Maine Sail]

Originally Posted by MapleSugarMan

A few other details that folks have asked for:
The controller is a Solar Pro Plug 'n Play rated for 21 amps max.

Scott,

Do yourself a favor, especially with 280W, and get yourself a good quality solar controller. What you have is a bottom of the barrel el-cheapo On/Off controller or what is commonly called a shunting controller.

A good quality controller will NOT turn off at 14.2V or 14.4V and will give a proper "absorption cycle" by holding the voltage to 14.4V and then, after a healthy absorption cycle, it drops to a float voltage..

An On/Off controller brings the batteries to the target voltage, lets assume 14.4V, then shuts off and waits for battery voltage to decay back to the low 13V range where it again turns on and brings the bank back to 14.4V where it then immediately shuts off again and decays back to the low 13's.. This robs you of precious daylight time and wastes energy that would actually serve to get your batteries full in a healthy time frame. On/Off regulation should only be used for wind sources. It is amazingly antiquated technology for solar.. That controller likely cost less to make than the corrugated packaging it shipped in did......

At the very least find a good quality PWM controller (Morningstar is a good start) or preferably a good quality MPPT controller. Be aware that many of the el-cheapo Chinese controllers DO NOT do what they say they do. I have seen Chinese eBay level controllers labeled as PWM that were nothing more than ON/Off and MPPT controllers that were nothing more than PWM... While there are some that are better, it is like going to Vegas trying to figure out which one that may be.. IIRC a guy here found a somewhat decent Chinese MPPT controller and I am sure someone will remember a hopefully post a link to it. IIRC it was about the cost of a quality PWM controller..

Reputable brands include (but not limited to) Morningstar, Blue Sky, Genasun, Victron, MidNite, Outback, Western etc...

Start with a good controller with properly sized wire and fuses then let us know how it works...

[n8kraft]

Always go to the documentation that came with your components. They describe the right way to install your system.
From the manual, available at: http://ec1.images-amazon.com/media/i...L000007394.pdf

• DO NOT use more than a total of 315 Watts (21Amps) of solar power
with the SolarPRO 21 Amp charge controller.
So you're good using 280 Watts

• For 12 Volt systems, ALL connections should be in PARALLEL:
Negative (-) to Negative (-), Positive (+) to Positive (+).
Double check your panels are wired PARALLEL and not one panel's Positive to the other panel's negative, then to the charge controller.

Replace the fuse and fuse holder withing 7 inches of the battery. I like waterproof rubber AGC fuse holders and would recommend a 30 amp fuse because for the two feet from the charge controller to batteries you have 38+ amps of capacity in the wire.

Good luck and read the fine manual!

[seacottage]

I've also the experience of a blown fuse and a melted fuse holder on my solar panels. In my case the cause was a bad connection. Bad connections create heat and melts the fuse holder or plastic cable sleeve and can start an electrical fire.