Arco 43 watt panel charge controller recommendation?

DanmcDanmc Registered Users Posts: 4
edited July 2020 in Construction #1
Hi,   new here, and hope I am not offending the intentions of the group. 

I have an Arco M65 panel on a sailboat , that runs ( or did) to a Sun Selector M8 charge controller.   The panel wires ran thru a water proof 2 pin connector which corroded or failed.  I cut the wires from the panel so I could remove it, and yes, I marked them so I could id pos and neg.  Unfortunately, don't laugh, I could not resist taking the  Boing ( ? ) connector apart to see why it failed  ( one the pin sheared off) , and then realized I had removed any way,  for me,  to identify which wire was pos/neg.  The installer had used 2 white wires from the connector. 

Anyway, I think I sizzled the controller when I went to hook up the panel, so I think I need a new controller. 

I get juice from the wires going to the battery, but the lights on the controller showing  analyzing, charging, etc, are not lighting.   I want to replace the controller, but simply connect the new one to the wires leading to and from the existing controller.  

The existing controller has 2 orange and one brown coming out.  I think each orange goes to one battery in my 2 battery bank, wired in parallel.  There is another 2 batter bank, but that is, I believe, the starting bank.  I also have a selector switch with Off, 1, both, and 2 on it .  The Company making the old controller is out of business.  

If you have stopped chuckling, and can recommend a charge controller please let me know.  The arco panel says 43 watts, max 3.68 amps, max volts 20,  5 amp fuse.

Many thanks for any suggestions.  Dan McElwreath


  • BB.BB. Super Moderators, Administrators Posts: 32,316 admin
    Welcome to the forum Dan,

    I edited your post (put in paragraphs). That should help you get more replies (vs a "wall of text").

    Most controllers are not very happy when solar panels or battery connections are reversed... So using a volt meter to confirm and mark (red tape/etc.) to keep polarity straight.

    Most solar charge controllers need to be connected to the battery bank first, and disconnected last. They use the bttery bank voltage to boot their computer, decide if bank is 12 or 24 volts, etc. If you connect the solar panels first (or disconnect the battery bank before disconnecting the solar panels), the charge controller can get confused or even damaged.

    Assuming the Vmp (voltage maximum power) of the solar panel is in the ~17.5 volt range, then any PWM (inexpensive) solar charge controller can be used (from "12 volt" solar panel to 12 volt battery bank). Having a fuse/breaker on the positive wire from the battery + bus to reduce the risk of fire (fuses/breakers are there to protect the wiring).

    Solar panels, even older ones, as long as they are glass and standard silicon cells, can last 20+ years very nicely. Panels that have plastic (or are flexible) style, generally do not last much more than 5-8 years or so.

    If you somehow connected the solar panel to your battery bank backwards--The current from the battery will generally fry the solar panel(s) that are reversed wired.

    You can connect your panel directly to the battery (check polarity-- positive to positive, negative to negative) and use a current meter (current clamp DMMs are very nice to have these days--and are very safe to use when measuring current) to make sure your solar panel is still OK--Alternatively, you can measure Voc (voltage open circuit) for ~20 volts, and in full noon time sun, connect to your standard DMM set for 10 amp scale, and measure Isc (short circuit current) and get around 2-4 amps max in full sun.

    Here are a couple examples of DC+AC Current Clamp DMMs (digital multi-meters). Note there are AC only clamp meters too--And they are fine instruments. However, for our needs, DC Current Clamp DMM is needed. (inexpensive) (mid priced meter)

    Solar panels on sail boats are not a great fit... Between swinging around at anchor, and the sails/rigging casting shadows, solar panels do not do a great job of harvesting energy (any shading can kill the panel/array output). As well as the risk of getting tools/items dropped on panel and shattering the cover glass...

    Morning Star makes a lot of smaller controllers--Most are conformal coated for marine use (I think--Always confirm with specs for specific controllers).

    Midnite makes a nice/water resistant PWM Controller:

    Both of the above our from our host NAWS... But you are welcome to buy anywhere. There are lots of less expensive units out there.

    I assume that the panel is for float charging your battery bank (mostly)... Too reliably "charge" a larger battery bank and other loads on your boat--A 43 Watt panel is not going to do much.

    Also, check your battery bank voltage/state of charge while your solar charger is off line... Lead Acid batteries do not like to sit in a discharged state for very long before they sulfate and die... Typically, you should keep flooded cell and AGM type lead acid batteries >~75% state of charge.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • DanmcDanmc Registered Users Posts: 4
    Hi,  thanks for edit and suggestions.  I had a few recommendations from people at companies  I contacted including one about a ZAMPO (?) controller but I will check out the Midnight and the Morningstar.  I had seen them in my browsing.  The panel is ok, watts is ok, volts ok, but it looked like the amperage was less than what is shown on the panel.  If the panel is rated at 4 amps max,  do I need to get a 10 amp controller??  Many thanks.  I am assuming that the controller will either come with a fuse or fuses , but if not, I will add them close to the battery.  Again, thanks for the help
  • BB.BB. Super Moderators, Administrators Posts: 32,316 admin
    No--You really only need the Isc (current short circuit) as max rating. In theory, the NEC requires 1.25x Imp as a safety factor.

    Generally, you have to buy fuse or circuit breaker separately--They do not come with the controllers.

    Fuses and breakers (and wiring) should be at least 1.25x the maximum continuous current you expect to see. Fuses and breakers are their to protect the wiring, not to protect the device.

    As always check the manual.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490mike95490 Solar Expert Posts: 9,511 ✭✭✭✭✭
    The midnight controllers, in my opinion are WAY  overkill for a 43w panel.  In fact, I wonder if you actually get any real use out of just 43 watts.  That is just a trickle charge, and maybe that's all you need.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

    gen: ,

  • DanmcDanmc Registered Users Posts: 4
    es, these are house batteries,  very rarely used during dayy, but helps to keep the cold plate in refrig cold without unning engine
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