Two SunPower 50w + Two Sunguard Controllers

[rgleason]

I have some questions about wiring these to our House FLA Bank.
(2) SunPower 50w 20v (similar)
(2) Sungard PWW Controllers SG-4

1. Each panel will be wired separately to respective controllers, then through a 6 position fuse panel which is connected to the house bank.
2. Don't connect the solar panels until the controllers are wired?
3. Can I connect both of the controllers to a 6amp fuse position to protect everything?
4. Or must I have two separate 3-4 amp fuses for each controller as it connects to the panel?
5. The panel contains circuits for two pumps, and other circuits that have to be directly connected to the house bank. (BTW the black goes through a battery gauge shunt.)

Do I need any other switches/fuses etc for safe operation?

Panel plus +++> Controller +++> 6-circuit panel fuse +++> Batt Pos

Panel neg ---> Controller ---> 6 circuit panel ----> Shunt ---> Batt Neg

I want to connect both panels to a single 6amp fuse in the panel.

Thanks

[dougweibel]

First, read the directions for the controller. The answer to your question on connection order should be there. Most controllers will want the battery side of the controller powered before the panel side.

The fuse question: You are fusing to protect the wiring in case of a short in the wiring itself or the controller. If the wiring is heavy enough to sustain 6 amps then a single fuse should be OK. If not, then separate smaller fuses are in order.

In my installation I put a breaker between the panels and the controller. This allows the panels to be electrically disconnected without having to physical take connections apart.

Assuming you have a master battery switch in your system you may want to think about to which side of that switch you want the solar connected. If you connect it on the switched side then you must disconnect the panels (assuming this is what your controller wants) before turning off the battery switch, and the battery will be truly isolated. If you connect the solar on the battery side of the switch then you can turn off the battery switch and the solar will remain connected to the battery. This may be desirable for example if you'd like to turn of the battery switch when leaving the boat but still have the solar keeping the battery topped up.

[sailorboy1]

Sounds a lot of extra trouble.

I have 2 320W panels. They are wired in parallel to a terminal strip. Then combined to a MPPT controller. And then directly to the battery banks via a 50A fuse

[rgleason]

Originally Posted by dougweibel

In my installation I put a breaker between the panels and the controller. This allows the panels to be electrically disconnected without having to physical take connections apart.

Thanks for the suggestions. At present I do not have a main battery disconnect switch. Would some small 6 amp throw switches be ok?

@Sailorboy1, maybe so, but I am trying to limit the result of mainsail shading the panels and preserve output.
I picked cheaper PWW controllers that were potted and waterproof because my good MPPT Genasun failed due to water and was not under warrantee.


We'll see how they do, but eventually I think MPPT would be better.

[noelex 77]

The controller is not the ideal choice. It only does single stage charging with a voltage set point that is a compromise between the normal absorption and float voltages. The set point is not user adjustable. Battery life will suffer.

There is also little reason to fit two of these units. With MPPT controllers fitting one controller per panel is helpful in extracting the maximum solar yield, but this does not apply to PWM controllers. There is no tracking or voltage conversion to optimise.

[JimsCAL]

I have 50w of solar (in two small panels) and one of those Sunguard SG-4 controllers. System has worked fine for about 5 years now. Yes the controller is a basic PWM unit, but its bulletproof and works perfectly for what I use it for - keeping my batteries topped up while my boat is on its mooring. A fancy MPPT controller would not work any better for me in this use.

[rgleason]

Originally Posted by noelex 77

The controller is not the ideal choice. It only does single stage charging with a voltage set point that is a compromise between the normal absorption and float voltages. The set point is not user adjustable. Battery life will suffer.

There is also little reason to fit two of these units. With MPPT controllers fitting one controller per panel is helpful in extracting the maximum solar yield, but this does not apply to PWM controllers. There is no tracking or voltage conversion to optimise.

Thanks Noelex, I understand your points. 14.1 would work with Gelcell and is not adequate for FLA topping up and avoiding degradation. Perhaps when we change to LiFePo I will change to two MPPT and it will be worthwhile, but Victron and Gensun GV-5-Pb-12V, 5 A MPPT $75 are almost as expensive as the panels.

[noelex 77]

Originally Posted by JimsCAL

A fancy MPPT controller would not work any better for me in this use.

My concern in this case is not that the SG-4 is a PWM controller, but that it only performs single stage charging. The controller will not perform the normal bulk, absorption, float stages needed to correctly charge a lead acid battery.

It will charge the batteries to 14.1v and leave them at this voltage. 14.1v is too low for a correct bulk or absorption charge so the batteries will take a very long time to reach 100% SOC. They are left longer than necessary at a PSOC (partial state of charge). When they do eventually reach a fully charged state 14.1v is too high for a correct float voltage so the batteries will be overcharged.

A slightly more sophisticated charger that incorporates the correct bulk, absorption and float voltages, preferably with adjustable voltage set points will pay for itself in longer battery life. Most even inexpensive PWM controllers at least incorporate the multi stage charging that the SG-4 lacks.

MPPT controllers are better again providing they are well made (don’t buy a very cheap MPPT controller). Generally these are the default choice. But with a very small and low voltage array PWM controllers are still acceptable, but make sure they can set up to charge the batteries properly.

On the plus side, the SG-4 is made by a well respected brand. It incorporates the most basic technology with simple circuitry and it is completely sealed so it should be very reliable. However, unless you have a very small battery bank that is easy and inexpensive to replace a controller incorporating bulk, absorption and float charging would be much better.

[rgleason]

It will charge the batteries to 14.1v and leave them at this voltage. 14.1v is too low for a correct bulk or absorption charge so the batteries will take a very long time to reach 100% SOC. They are left longer than necessary at a PSOC (partial state of charge). When they do eventually reach a fully charged state 14.1v is too high for a correct float voltage so the batteries will be overcharged.

I totally agree with you about this, I should have researched this device from Morningstar more than I did. Do you know of any low amp controllers that have those characteristics?

[noelex 77]

Originally Posted by rgleason

I totally agree with you about this, I should have researched this device from Morningstar more than I did. Do you know of any low amp controllers that have those characteristics?

The best PWM regulators are produced by Plasmatronics. In the days before MPPT controllers were even invented I used a Plasmatronics PL40. This is a very versatile regulator with user adjustable set points and a multistage charging algorithm with features that are still not available on most modern regulators such as independently programmed bulk and absorption voltages.

The PL40 is still available, as is the slightly smaller, but otherwise identical PL20 controller.

However, these days I would not recommend this regulator. It is as expensive as good MPPT regulators.

This is the problem with PWM regulators once you include features such as user adjustable set points (just about essential in my view) and good build quality from a reputable company. There is not much saving over MPPT controllers (such as the excellent Victron series).

If you forgo the user adjustable set points and accept a small number of fixed battery set points (such as flooded, AGM, gel etc) the choice becomes greater. Products such as the Morningstar Sunsaver Duo are reliable and will do the correct multistage charging, but with fixed battery set points. Generally you are better spending a little more money on a good MPPT controller, but this depends on your budget and local pricing.

The alternative is inexpensive “no name” (eBay etc) controllers. I would not recommend purchasing a “no name” MPPT controller. These generally have terrible tracking (some are not even really MPPT controllers despite the sticker) and poor reliability.

PWM controllers are much less expensive to design and build. There is less to go wrong and here the “no name” brands can function well and have reasonable reliability despite the low cost, questionable quality control and overall build quality. Many of these will do multistage charging (just look at the spec sheet) . They can be a sensible buy if you are trying to keep costs as low as possible and understand the limitations.

Finally, make sure you understand that PWM controllers are only suitable for low voltage solar panels (so nominally 12v panels if you have a 12v house bank). If you upgrade later to higher voltage panels the controller will need to be replaced with an MPPT controller. Also any controller without user adjustable set points is not likely to be suitable for new battery technology including lithium. Sometimes spending a little more initially can be cheaper in the long run.

So with 100w solar I would buy one of the smaller Victron MPPT controllers, such as the 75/10. The Smartsolar series has Bluetooth which makes adjusting the set points easier and the app provides useful information.

[rgleason]

So with 100w solar I would buy one of the smaller Victron MPPT controllers, such as the 75/10. The Smartsolar series has Bluetooth which makes adjusting the set points easier and the app provides useful information.

@Noelex77 That's valuable information. Thank you. I tend to like the Victron MPPT controllers and the 75/10 Smartsolar ($88) would be good, but shouldn't I have two of them for the two 50w panels on port and starboard side of the dodger, due to shading? Note that these SunPower panels are rated at 20vdc.

When I add two 100w bimini or stern panels, perhaps I can put the 50w and 100w port side solar panels on one controller and the corresponding starboard panels on the other controller? (wired in series or parallel?) --but I think they have to be the same type of panel to do that.

Note that the Victron 75/10 controllers would have to be mounted on the bulkhead inside my port cockpit locker which is not totally protected from water intrusion, and these devices want to be somewhere that is always dry I believe. Its a small boat really.

Also what kind of switch would be appropriate for the red wire leading to each panel?

[rgleason]

Now (2)

Power 50w
Vmp 17.5v voltage
Imp 2.8a current
Voc 21.5v open circuit
Imc 2.95a short circuit current
Maximum series fuse 15a


Future (2)
Power 100w
Vmp 17.5v voltage
Imp 5.8a current
Voc 21.5v open circuit
Imc 6.2a short circuit current
Maximum series fuse 15a

[noelex 77]

Originally Posted by rgleason

@Noelex77 That's valuable information. Thank you. I tend to like the Victron MPPT controllers and the 75/10 Smartsolar ($88) would be good, but shouldn't I have two of them for the two 50w panels on port and starboard side of the dodger, due to shading? Note that these SunPower panels are rated at 20vdc.

Two MPPT controllers will give you a higher yield, especially for two panels that are going to experience very disparate conditions, but one controller will work fine and still give you a higher yield than an PWM controller (or two PWMs, as unlike MPPT there is no improvment in shade tolerance fitting multiple PWM regulators). So one MPPT is good budget solution.

Originally Posted by rgleason

When I add two 100w bimini or stern panels, perhaps I can put the 50w and 100w port side solar panels on one controller and the corresponding starboard panels on the other controller? (wired in series or parallel?) --but I think they have to be the same type of panel to do that.

It is good to see you planning for future upgrades. Two panels can be wired in parallel to one MPPT controller providing they have a similar Vmp. Hooking up different wattages is OK providing the voltages match or are very similar. You should be able to find some 100w panels that match the characteristics of your 50w panels. A good long term solution would be to wire the port panels (50 and 100w) to one controller and the same for the starboard panels. However, with 150w per controller you really need the slightly larger Victron 75/15. With this future upgrade in mind you may consider purchasing the 75/15 now instead of the 75/10, as the price difference is not great.

Originally Posted by rgleason

Note that the Victron 75/10 controllers would have to be mounted on the bulkhead inside my port cockpit locker which is not totally protected from water intrusion, and these devices want to be somewhere that is always dry I believe.

This is a problem. The Victron controllers really need to be kept completely dry. You could mount them in waterproof enclosure or an enclosure that is watertight at the top but open at the bottom, but even in the latter case the ventilation would be inadequate or at least marginal. These regulators rely on passive cooling and run quite hot even with good ventilation. A small computer fan would solve the problem, but this adds complexity, costs power and would be blowing in salt laden air.

Ideally solar regulators are better mounted close to the batteries so if it is feasible to move them to a dry location close to the batteries this would accompish two goals. If not, you need to rethink the choice of controller.

Some of the “waterproof” solar regulators don’t look too waterproof to my eyes, but they may be OK for your application.

This is a PWM example that looks better than most on paper ( I have never used this regulator), it will do the correct multistage charging and is not too expensive, but the versatility is lost as you can only pick from a limited number of voltage set points and of course it does not have MPPT capability so the yield will be slightly less.

https://uk.renogy.com/new-edition-vo...ge-controller/

Perhaps other members can recommend something that may be a better choice.

[rgleason]

Noelex77 That is a great help to a pretty small electrical problem. It is clear I must mount the first Victron 75/15 in waterproof location on the cabin side of the bulkhead, and possibly even at the future LiFePo location.

Which of course brings up a thorny decision I've been trying to avoid making... Which interior cabinet will be used for a new LiFePo Battery location. It is something I now must consider and think through more completely. The LiFePo are likely to end up in the aft Port Cabinet behind the settee Cushions, right forward of our Ice box. This is about 3' forward of the bulkhead, and there are ways to run wires there from the solar panels. Heavy new alternator wires (+/-) would run from the engine, forward under the cabin sole and up under the settee into the cabinet. Also there would be some new wiring to the existing 50a breaker panel as well.

I need to measure that cabinet carefully to see if I can fit 260-300ah of LiFePo batteries in it, plus a BMS, a buss and some switches and the two Victron Solar 75/15 Controllers. It could get full fast.

It looks like a SunPower 50w and a 100w both have Vmp 17.5 voltage so they can be wired in parallel to one Victron 75/15, duplicated port and starboard. Thank you.

Nothing is simple on boats, but when it is finished it should look simple!

[noelex 77]

Originally Posted by rgleason

Noelex77 That is a great help to a pretty small electrical problem. It is clear I must mount the first Victron 75/15 in waterproof location on the cabin side of the bulkhead, and possibly even at the future LiFePo location.

That sounds like a sensible solution.

If you are planning a future upgrade to lithium it is particularly important that the solar controller has infinitely adjustable set points. While some solar controllers include a pre-defined “lithium option” this is generally not ideal, so user control is needed and few inexpensive controllers offer this feature.

The Victron range of MPPT has one of most user adjustable interfaces, especially at the relatively low price point. In addition, they have a communication system that can talk to some BMS systems. While it is unlikely with a relatively small lithium system that you would adopt this level of sophistication, it is nice that the option is available.

So personally I would take the time and effort to relocate the solar controllers to a dry location and purchase the Victron 75/15, with a view to adding a second identical controller as your solar system expands.

Be aware there are two models of the Victron 75/15. The non-Bluetooth BlueSolar model and the otherwise identical SmartSolar model that has Bluetooth installed. The Bluetooth model is worth the extra cost.