One controller or two?

[Tillsbury]

Originally Posted by john61ct

"our" meaning Victron, correct?

I think this is just copypasted from their docs right?

Certainly appears so, but it's useful information nevertheless. Confirms that ve.direct to USB is the way for up to five devices which should be OK for me. I will come back after installation and confirm, as real life is often different from website blurb and there's no substitute for actual experience.

[Pelagic]

Is "Ambient Temperature" a factor when deciding the number of controllers to use?

I am in the process of adding a 5th Solar panel above the davits.
For my existing 4 x Sunpower 327w Panels I am using the Outback 80a

It seems to work well and I get a max of 42a @ 24v charge.
Outback is rated to 80a

Issue is that when the Temperature gets Hot here in the Philippines (above 32C) the Outback Fan kicks in fairly often, even though I mounted it with good circulation.

Sounds like a hair drier which I can live with as we would not be in the Pilot house in that heat, but is that just an ambient Temp thing?

When I add this new 365W Q Solar, am I adding to a heat problem for the Outback?

[john61ct]

Likely yes, more incoming current will mean fan duty cycle increases.

But noisy fans can often be replaced with more quiet ones.

[swampbush]

Originally Posted by Pelagic

Is "Ambient Temperature" a factor when deciding the number of controllers to use?

I am in the process of adding a 5th Solar panel above the davits.
For my existing 4 x Sunpower 327w Panels I am using the Outback 80a

It seems to work well and I get a max of 42a @ 24v charge.
Outback is rated to 80a

Issue is that when the Temperature gets Hot here in the Philippines (above 32C) the Outback Fan kicks in fairly often, even though I mounted it with good circulation.

Sounds like a hair drier which I can live with as we would not be in the Pilot house in that heat, but is that just an ambient Temp thing?

When I add this new 365W Q Solar, am I adding to a heat problem for the Outback?

Are you considering running the new panel to the existing Outback 80? Looks like the voltage is completely different on the new panel, should have its own mppt.

[Pelagic]

Originally Posted by swampbush

Are you considering running the new panel to the existing Outback 80? Looks like the voltage is completely different on the new panel, should have its own mppt.

Hi Swampbush, yes I was hoping I could run the new panel to same outback

i had asked before if the voltage match was critical as I could not get just one Sunpower panel locally.
Most said, not critical but try and get them close

Sunpower Vmpp 54.7V
Q power. Vmpp 38.94V

Don't know if electrically speaking that is close enough?

[noelex 77]

Originally Posted by Pelagic

Sunpower Vmpp 54.7V
Q power. Vmpp 38.94V

Don't know if electrically speaking that is close enough?

No, the voltages are not close enough and you will need a second controller.

MPPT controllers can only have one input voltage. If the controller selects around 54v, the Sunpower panels will produce full power, but the Q power panel will produce almost no power (the power produced by a solar panel drops off very rapidly if the voltage is even slightly over the Vmp).

If the controller selects an input voltage of around 38v the Q power panel will produce full power, but the power from the Sunpower panels will be around 38/54 or about 70%. This is lot to lose.

An intermediate voltage will not help much. As noted above, the Q power panels will produce very little power once the voltage is above 38v.

(The above is a little simplified, the real life Vmp of both panels will be a little lower due to temperature effects).

Originally Posted by Pelagic

Issue is that when the Temperature gets Hot here in the Philippines (above 32C) the Outback Fan kicks in fairly often, even though I mounted it with good circulation.

I am surprised that the fan kicks in often, although the ambient temperature is obviously high. Perhaps measure the heat sink temperature and contact Outback to see if the fan controller is cutting in early. If it is not defective, try a larger external computer fan running on a low speed and blowing over the heatsink. A cheap temperature controller can be used to switch on this larger fan just before the temperature of the heatsink reaches the point that the internal fan is triggered. The parts for the above should not be much more than about $20 and the wiring is easy. A temporary installation would show if the solution is effective.

[Pelagic]

Originally Posted by noelex 77

No, the voltages are not close enough and you will need a second controller.

MPPT controllers can only have one input voltage. If the controller selects around 54v, the Sunpower panels will produce full power, but the Q power panel will produce almost no power (the power produced by a solar panel drops off very rapidly if the voltage is even slightly over the Vmp).

If the controller selects an input voltage of around 38v the Q power panel will produce full power, but the power from the Sunpower panels will be around 38/54 or about 70%. This is lot to lose.

An intermediate voltage will not help much. As noted above, the Q power panels will produce very little power once the voltage is above 38v.

(The above is a little simplified, the real life Vmp of both panels will be a little lower due to temperature effects).



I am surprised that the fan kicks in often, although the ambient temperature is obviously high. Perhaps measure the heat sink temperature and contact Outback to see if the fan controller is cutting in early. If it is not defective, try a larger external computer fan running on a low speed and blowing over the heatsink. A cheap temperature controller can be used to switch on this larger fan just before the temperature of the heatsink reaches the point that the internal fan is triggered. The parts for the above should not be much more than about $20 and the wiring is easy. A temporary installation would show if the solution is effective.

Thanks again Nolex for the clarification.
I will get a 2nd controller for the single Q-365w panel.

Does anyone have a recommendation on what to buy for that size?

[noelex 77]

Originally Posted by Pelagic

Thanks again Nolex for the clarification.
I will get a 2nd controller for the single Q-365w panel.

Does anyone have a recommendation on what to buy for that size?

The Victron series of charge controllers have a few quirks, but are reasonably well made and very good value, so are difficult to beat.

A 365w panel on a 24v house system will have a maximium charge current of around 14A.

The Victron 75/15 would be sensible choice. The newer model has bluetooth built in, which is easier than the older model that required a seperate dongle. A maximium input voltage of 75v is fine for the Q panel (but not for the Sunpower panels).

There are a couple of other options:
1. A larger Victron controller.
MPPT controllers, even very good quality models such as the Outback 80 you have, are not enormously reliable. If your Outback fails you will be limited to your 365w panel. A larger Victron controller, for example the 100/30 or 150/45 model, would be fine for the 365w panel, but would allow temporary connection of the Sunpower panels, restoring most of the solar output if the Outback fails. I doubt this added redundancy is worth the extra cost, but it is worth considering. The Victron units run reasonably hot and I suspect the larger heat sink achieved with oversizing the controller will also will help the long term reliability especially in your warm conditions.
2. Sell the Outback and install one Victron per panel.
This would require five 100/15 controllers. The small Victron units are inexpensive and I suspect the second hand value of the Outback 80 would just about pay for all the new controllers. This option solves the noise problem you are experiencing (there is no fan) has better redundancy and controlling the power point of each panel separately will deliver a little more power from the panels. However, the Victron units are not as versatile as the Outback and there are some annoying problems running multiple Victron units.

[Pelagic]

Hi Nolex.
The individual controller for each panel does seem like the best solution, but it would be a wiring nightmare as it would mean 8 steel deck penetrations for the Sunpower + 2 for the Q panel and then 10 long runs to the house bank.

1981 steel boats were just not designed for spacious wiring runs and electrical lockers.

Presently I am able to combine the 8 leads to two before the long run via a breaker to the Outback.

My Sunpower solar panels are removed right now as we are fitting the watertight Fiberglass Bimini between the two racks


I think my first step will be to test the Outback with an external fan for these hot days of 34C (feels like 42) .

Still getting used to living with Solar so my redundancy in case of an Outback failure is my Gen and Large case alternator until the green side balances out with experience.

[john61ct]

75/15 model will not be big enough to handle 365W

The 100/20 would still be some overpaneling, waste a bit of peak power output.

100/30 would be good, for up to around 450-500W.

[noelex 77]

Originally Posted by Pelagic

Hi Nolex.
The individual controller for each panel does seem like the best solution, but it would be a wiring nightmare

I can understand that. If it is difficult, I would certainly ditch the idea of individual controllers. If you have other good forms of power generation, redundancy is less of a consideration, so the simple and cheap Victron 75/15 is by far the best option.

In future, if you ever do a refit, a swan neck is a great way of feeding multiple deck wires. On a metal boat it is simply a matter of welding a bent pipe for a foolproof watertight connection. A swan neck at the mast and stern is a great addition so you can easily feed future wires through the deck. More wires are often needed when equipment changes.

With individual controllers the wires from each panel will be thinner so the total wire bundle size feeding individual controllers is not enormously larger, or more expensive than wiring the panels in parallel with a single controller. However, if not wired like this from the start, the cost and trouble of changing makes the modification not worthwhile.

I would be surprised if a larger computer fan does not solve your noise problem. Consider running the fan at lower voltage (for example a 24v fan supplied with 12v). This greatly reduces the fan speed and therefore the noise. The internal fan in the Outback is tiny. A larger external fan running at low speed should provide plenty of cooling with much less noise, but it will need some experimentation with the fan speed and thermostat cut in temperature to find the best combination. Electronic modules that will convert 24v to an lower and adjustable voltage are readily available.

[noelex 77]

Originally Posted by john61ct

75/15 model will not be big enough to handle 365W

The 100/20 would still be some overpaneling, waste a bit of peak power output.

100/30 would be good, for up to around 450-500W.

Pelagic has a 24v not a 12v house bank.

Victron claim the 75/15 controller is suitable for a 440w solar installation at 24v (220w at 12v). Personally, I would be a little more conservative than this recommendation, but 365W at 24v is fine for a 15A controller.

[john61ct]

Aha yes that's different, doubles the watts capacity, even 500+W would then be OK.

Roseanne Roseannadanna voice "never mind" 8-)

[john61ct]

Originally Posted by noelex 77

Personally, I would be a little more conservative than this recommendation

That is important with the Voltage limit wrt Victron specs, here 75Voc.

But they allow for a very high overpaneling margin on the power side, that 220/440 W is just the unit's **output** limit.

[noelex 77]

Originally Posted by john61ct

Aha yes that's different, doubles the watts capacity, even 500+W would then be OK.

Victron’s recommendation of a maximum solar panel size of 440w (for a 24v battery) is based on the premise that a 440w solar panel will only rarely be putting out more than 15A. The loss of total power compared to using a larger controller (for example a 20A model) will only be slight and for most users given the low cost of solar panels does not justify the extra cost of a larger controller.

This argument is reasonable, but boat owners have slightly different priorities. They often have no room for installing a larger solar array and so optimising the output from a limited area is important. In addition, the cost of a marine solar array per watt is high because of installation costs (such as a solar arch) and the use of more expensive panels such as flexible and/or high efficiency models. Saving a few dollars on a controller that will limit power, even occasionally, is rarely a sensible on a yacht.

I also think there is some reliability advantage of not fitting the very smallest controller that may just be acceptable, especially where the unit will be relying on an internal self protection mechanism to limit the current from the solar panels to prevent damage. Marine installations often fit controllers in lockers with high ambient temperatures and limited ventilation. Victron, for example, want a minimum clearance of 10cm (4 inches) both above and below the unit, something that is sometimes not achieved in practice.

Hence my suggestion of being slightly more conservative than the maximium solar size recomended by Victron. I would stay well under the 440w. Posts on Cruisers Forum frequently advise the opposite. A Victron 75/15 is not OK with 500w+ of solar (@24v) in my view. The self protection mechanism will mean the unit will not immediately destroy itself’ but this would not be a sensible choice.