[cthombor]

I wouldn't expect an Anderson plug to survive very long, if you're connecting or disconnecting your solar panels while they're producing power. And there's a safety issue -- what will you do if the Anderson plug won't disconnect because its contacts have been arc-welded together? What if the plug gets really really hot and starts to melt?

Arcing is a serious problem with currents above 10 amps, no matter what the voltage.

Here are the design options I can think of (for a 600W/24V system):

1. Install a 32A PV 150VDC breaker on at least one of the feedlines from the solar panel, and break the circuit *before* you connect or disconnect it (at the Anderson plugs). See https://diysolarforum.com/threads/solar ... tch.13472/.

2. Wait until dark to connect or disconnect.

3. Cover up your solar panels with an opaque blanket before you connect or disconnect.

4. If you have foldable solar panels, unfold them after (and never before!) you have connected them.

For safety, you might want to include two of these options in your system. Options 2, 3, or 4 might be your first line of defense, with option 1 being your fallback if your Anderson plug ever arc-welds or melts?

BTW earlier this week I received a "300W" foldable solar panel which I had ordered a few weeks ago via AliExpress. The panels and carry-bag had excellent build quality, weigh only 8 kg, cost NZD 800 (including delivery and GST). The kit has some semi-useful cabling and a cheap-as-chips PWM charge controller (with *no* instructions, no branding, no model number, no quality-assurance label!). Well ... the nearly-useless PWM controller did allow me to confirm that the panels are in good working order. I put "300W" in scare-quotes because the kit is set up for 12V operation with a PWM controller; at 15A that's only 180W. I don't have my MPPT controller yet, but I'd expect to get a bit more than 300W per panel whenever -- and it's not uncommon here in godzone, at least in the NI -- the mid-day irradiance is above 1100 W/m2. Foldable PV panels seem like the right design option for my work-in-progress e-NV200 conversion, as I really don't like parking in full sun if I can avoid it... when my design is complete and built and tested, I'll post details...

[Neddy]

Anderson plugs are made for "low voltage, high current" DC applications. They feature solid copper spring loaded silver plated contacts with a self cleaning contact design to resist arcing. Even their "standard" models are rated at 50 Amps.

The OP wants to connect a single portable solar panel to a controller. By way of example, a 200W 12v panel (or a 400W 24v panel) would have a peak current of around 10 Amps - way below the rated capacity of standard Anderson plugs. No supplementary switch is required. This is the arrangement Redarc recommend, for example. Note the use of Anderson plugs and the absence of any supplementary switches.

https://www.redarc.com.au/wiring-diagra ... ator-setup

[cthombor]

Hi Neddy, thanks for the correction! I looked up the specs on the Anderson SB-50, which I'm guessing to be the one supplied by RedArc in their 250W kit. The SB-50 is UL-rated for 250 connect-disconnect cycles under 50A load (https://www.andersonpower.com/content/d ... T-PPMP.pdf), which is pretty darn impressive!

As you say, a single 250W panel (or even the two 300W panels I'll be using) can't produce anywhere close to 50A -- so the sacrificial contacts in an SB-50 should survive at least 1000 connect-disconnect cycles in this application. That's a long time!

[cthombor]

But... if you're using an off-brand plug that resembles an Anderson SB-50, all bets are off... I'm now looking at the plug supplied on my 300W portable-PV kit, it's an SG 50A plug from Sheng En Di. A warning in English says "For disconnect use only". A warning in French says "Ne pas employer pour la rupture du courant." If you understand French you'll be amused! (If not, I'll save you the trouble of looking up the translation: this plug should not be used to disconnect a circuit that's carrying load. 10A is enough load to cause some high-temperature arcing on a DC circuit, even if there's only 250W of power available for the arc!)

So... I'd advise any user of the RedArc kit to inspect the plug. If it isn't actually an Anderson SB-50, then I (being quite safety-conscious) will be careful to connect and disconnect the PV panels only when they're folded up -- that will ensure there's no current flowing when I'm connecting them to the PWM. If you like to take your chances, then you can hot-plug anything that resembles an Anderson SB-50 and you'll probably be fine... at least for a while... especially with only a single 250W panel (which, even under the mid-day NI sun, won't ever be producing more than 300W).

And... even if you're using an Anderson SB-50, you do have to inspect your plugs at least once in a while -- to ensure that they haven't become fouled, pitted, etc. -- especially if they have been exposed to wet conditions. The MP4 connectors (bog-standard in fixed-PV installations) have rubber seals to keep their contacts dry, but not the SB-50.

Below: the "Preventative Maintenance" section from the Anderson manual. (Amusingly... in point 2C, they warn against relying on their sacrificial-contact in everyday use, it's arguably only a safety-feature and not something you should risk "wearing out" ... especially in an off-brand replica, where the tin or silver plating on the terminals may not be anywhere near as thick or uniform as on the significantly more-expensive Anderson-branded SB-50s

Preventative Maintenance

Damaged connectors, contacts and cables may present hazards, resulting in inefficient battery and charger
operation. To avoid these problems, conduct the following maintenance checks at least once annually. If you
see any of the following problems, take corrective action immediately.

1. Dirty Connectors

When engaged and disengaged, the contact surfaces of Anderson™ flat wiping connectors “over wipe,” thus providing
self cleaning action. To ensure the continued benefit of this feature, clean the contact surfaces and lubricate the
connectors. Use a “white” lithium grease, which may be obtained from hardware stores and automotive parts suppliers.

2. Melting Connectors

Connector housings overheat and melt for many reasons. To prevent this:

A. Examine the crimp between cable and contact. Ensure the crimp tooling recommended by Anderson™ has been
used. Improper crimping, corrosion, and broken wires result in unnecessary resistance causing the contact to heat up.

B. Check contact surfaces for signs of “pitting” caused by dirt or disengaging connectors under load. One
badly pitted contact, particularly in a connector attached to a battery charger, can lead to pitting on surfaces
of other contacts. If not corrected, this can result in an epidemic of bad connectors throughout a fleet of
electric vehicles and in chargers and batteries.

C. Check to see if batteries are being disconnected while the charger is still on. This causes the contacts to
arc at the tips, resulting in progressive pitting and silver removal from tip to crown. If this practice is occurring,
it should be discontinued to avoid major repairs in the future.

3. Other Conditions

If any of the following conditions exist, the connector housing, contact and / or cable should be replaced immediately.

A. Housing - Cracks, missing pieces, evidence of excessive heat, discoloration. You may consider replacing the
existing housing with a Chemical Resistant equivalent for improved durability against UV rays and common
solvents and hydrocarbons.

B. Contacts - Pitting, burns, corrosion, excessive wear and cracked crimp barrels, as shown in image “B”.

C. Cable - Exposed copper near housing, cracked cable, peeling or frayed insulation.

D. Handles - Loose attachment and signs of damage as missing or loose hardware and cracked or broken plastic
(Handles should be used for connectors that are hard to reach or move).

E. Cable Clamps - Loose attachments, signs of abraded cable jacket, missing or loose hardware. (Cable clamps
should be used to relieve strain on unmounted cable).

[mattn]

There is a huge difference between theory vs. practice. In theory, the difference between theory and practice is small. In practice, the difference between theory and practice is large.