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Old 19-03-2015, 06:52   #1
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Solar Controller

Apologies if this has been answered before. I bought a boat with an old Solar Panel on it, that is connected to an even older Solar controller. The Panel is showing 20v but nothing is coming our of the controller....... My buddy says I don't need a controller and to wire the panel straight to the batteries...... is this OK......

I have bought two more solar panels..... should I connect them in Series or parallel?

Can I connect the two new panels and the old one all together??

If I do wire them all together, should I use a controller, if so, what is a good one to use??

Thanks for any advice.....
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Old 19-03-2015, 07:37   #2
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Re: Solar Controller

Quote:
Originally Posted by Gi-Lo View Post
My buddy says I don't need a controller and to wire the panel straight to the batteries...... is this OK
NO! IT IS NOT OK!
1) Charging your batteries at 20V will ruin the substrate and kill them.
2) Once the batteries are fully charged, if they continue to receive a charge current, it starts water electrolysis producing H2O2, which is explosive and likes to be in gas form.

Quote:
Originally Posted by Gi-Lo View Post
I have bought two more solar panels..... should I connect them in Series or parallel?
Connect them in parallel. In series, the voltages are added together (e.g. two 5A 14v panels in series is 5A at 28v). In parallel, the current is added (10A at 14v).

Quote:
Originally Posted by Gi-Lo View Post
Can I connect the two new panels and the old one all together??
In parallel, yes: In series, if one of the panels is shadowed, it becomes a resistor and completely turns off the circuit regardless of what the others are generating. In parallel, you shadow one panel and the others can still charge.

Quote:
Originally Posted by Gi-Lo View Post
If I do wire them all together, should I use a controller, if so, what is a good one to use??
Yes. Use what is called an MPPT, or Maximum Power Point Tracking controller. These types take the current coming from the panels, say at 17v, and convert the voltage to the optimal required for your battery type (e.g. 14.2). This works in either high or low light conditions. If the voltage is coming in low, the MPPT can convert it to a higher voltage needed to continue to charge.

The MPPT can squeeze several tens of percent more solar into your battery for a given condition. Further, for some MPPT's, when the batteries are fully charged, they can route incoming solar power to an alternative circuit (e.g. a water heater) so you're always taking advantage of the available power.

Post-script:
Determine if your panels are monocrystalline or thin-film. Monocrystalline are more efficient at a given light intensity, but have the drawback that if even a small part is shadowed, the whole panel responds as if it too is shadowed.

Thin film, on the other hand, while less efficient at a given light level, will continue to generate current even when partially in shadow.

This is important because even small parts of boats like antennas or shrouds cast enough shadow to have an affect. So use this information to determine optimal placement.

Good luck.
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Old 19-03-2015, 07:39   #3
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Re: Solar Controller

You need a controller. Period. The only setup where you wouldn't is when using a tiny panel for trickle-charging as far as I know.

When connecting panels in series, a smudge/shadow/seagull **** on one cell will greatly affect the performance of the entire rig. When in parallel this will not be the case. Wether it is desireable to connect them in parallel or series fully depends on the requirements for the rig and the output of the panels. We'll need more input on that to answer the question.

You can ofc connect them together with the old one, but I'm unsure how that would affect the total output of the rig. Surely somebody a lot smarter than me will be able to answer that.

There are different types of controllers, read up on them. Google is your friend, as is this guy's blog: https://handybobsolar.wordpress.com/

After doing the research, I found that the "ecoworthy mppt" controller was best for my needs. It won't support the biggest rig, but it's great bang for buck.
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Old 19-03-2015, 07:51   #4
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Re: Solar Controller

Follow the advice above, its sound.. One thing I will add, you can have multiple MPPT controllers (1 for each panel). This completely eliminates shading issues and provides redundancy. If you are using panels under 230W its not too expensive as 20A controllers can be bought for $99 now!

Your buddy is technically right, IF YOU ARE IN A BIND. For a short period you could connect the panels directly to the battiers as 20V is the unloaded voltage of those panels. They really put out about 15-16V when connected to a battery. Short period means a day or two with constant monitoring to ensure you don't boil the batts.
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Old 19-03-2015, 08:48   #5
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Re: Solar Controller

Yes it is possible to connect a solar panel directly to your battery bank and use it successfully. I did it for four years with no problem. But you need to be aware of what you are doing. In my case I had a 130w panel charging a 450ah bank while running a fridge that used 40 to 50ah per day. Not likely the batteries could get overcharged.

But when I decided to add a second 130w panel I installed a PWM controller, knowing that it would be possible to overcharge the bank.

In your case I would get a controller.
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Old 22-03-2015, 21:24   #6
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Re: Solar Controller

Thanks guys for all of your input.....

Any suggestions? I have been recommended this one....

SunSaver Duo » Morningstar Corporation
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Old 22-03-2015, 21:37   #7
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Re: Solar Controller

I bought a couple of these "controllers" for around $12.00 each last year.

20A CMTP02 Series Solar Charge Controller Battery Regulator 12V 24V Auto Switch | eBay

Despite the horror stories, they will hold the charging voltage to around 14.4 volts. I monitored it several times.

I have a 100 Watt Solar Panel hooked to one of them and am about to add two more 20 watt panels to another.

They are charging two 12 Volt batteries hooked in parallel that power small electronics including depth, GPS (2), autopilot, 1500 watt inverter, etc.
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Old 22-03-2015, 21:39   #8
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Re: Solar Controller

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Originally Posted by Gi-Lo View Post
Thanks guys for all of your input.....

Any suggestions? I have been recommended this one....

SunSaver Duo » Morningstar Corporation
That is the controller that I elected to install a couple of years ago, great unit with zero problems and charges both battery banks independantly.
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Old 23-03-2015, 07:55   #9
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Re: Solar Controller

Same here. My sunsaver has been working nonstop for two years without a single problem. Its about 9 feet from the panel and 5 feet from the battery bank.
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Old 03-04-2015, 02:35   #10
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Re: Solar Controller

So Im confused, the Sunsaver duo is not an MPPT..... which was reccomended. I asked my local dealer and got this response.......


You only *need* an MPPT when charging a 12V battery bank from a 24V panel, or vise-versa, the 150W panels would have an open circuit voltage of about 22V with a short circuit current of about 8.5A, and would be rated at 12V. So a PWM controller with the panels in parallel would be fine as the PWM controller will drop the Voltage to a max of 15V and double the current to about 17A so that along with the 80W panel which will probably output around 4A, you'll get a good 20-24A charge to the batteries from solar alone.

And on the Subject of Wiring panels together....

There are a few ways to do this, though connecting all 3 panels together is not one of them.
It's not recommended to mix panel sizes or you restrict the larger ones to the specifications of the smallest one.

FYI and I encourage any comments on this advice......
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Old 03-04-2015, 04:57   #11
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Re: Solar Controller

It would help to know the specifications of your panels. It will be written on the back.

Your controller should be fine. MPPT does produce a very modest gain, but you need to spend a reasonable amount of money to get a good one. At the sort of cost of controller you are looking at, a good quality PWM is better than a cheap MPPT model.

My only criticism of the controller is the voltage set points are not adjustable and the 14.4v absorption voltage is on the low side. It not clear if the controller applies temperature compensation measured at the controller. If this is the case I would order the the optional battery sensing temperature probe (it will not be expensive). Applying temperature compensation measured at the controller will reduce the absorption voltage further.

I assume you have two 150w nominally 12v panels together with an older 80w nominal 12v panel. If this is case connect them all together in parallel and you will have a reasonable system.
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Old 03-04-2015, 15:34   #12
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Re: Solar Controller

Your assumptions on the panels are correct, and I love your idea of wiring all three in parallel, but this guy has specifically said that mixing panels will restrict the larger ones to the spec of the smaller one, would this be the case?..

If I could wire them all I parallel, I would propose to use this controller.....

BlueSolar PWM - Victron Energy

The Duo version...
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Old 04-04-2015, 00:44   #13
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Re: Solar Controller

You you can wire panels of different wattage together in parallel. If you are using a MPPT controller the Vmp needs to be close for maximium effeciency. With a PWM controller all that is needed is that they are all (nominally) 12v panels.

You will then have 380w we and the Victorion controller is only 20A which is a bit small. It also still has the conservative 14.4 v absorption voltage.
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Old 04-04-2015, 01:46   #14
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Re: Solar Controller

Thanks Noelex, I will endeavor to get the exact Panel specs when in a couple of days.....

Here is the full transcript of what the local dealer sent to me.....


There are a few ways to do this, though connecting all 3 panels together is not one of them.
It's not recommended to mix panel sizes or you restrict the larger ones to the specifications of the smallest one.

Assuming that the 2 batteries are a starter battery and house battery and it's on a boat my recommendation would be;

Connect the 80W panel to a Morningstar Sunguard 4A to the starter battery
Connect the 2 x 150W panels in parallel to a Morningstar Sunsaver 12V 20A to the house battery
Connect a Victron Cyrix-CT battery combiner between the starter and house battery so when the alternator of the boat motor charges the starter battery, the excess will flow into the house battery, additionally, when the starter battery is full, the charge from the Sunguard will also flow over into the house battery.

Given that the starter battery should always be full, you'll always be getting a charge to the house battery from all panels when in the sun, you'll also be getting a charge from the alternator while driving.

The Cyrix is an intelligent combiner so you won't overcharge the battery.

You only *need* an MPPT when charging a 12V battery bank from a 24V panel, or vise-versa, the 150W panels would have an open circuit voltage of about 22V with a short circuit current of about 8.5A, and would be rated at 12V. So a PWM controller with the panels in parallel would be fine as the PWM controller will drop the Voltage to a max of 15V and double the current to about 17A so that along with the 80W panel which will probably output around 4A, you'll get a good 20-24A charge to the batteries from solar alone.

MPPT's are said to be 30% more efficient, and the main difference is that where a PWM controller will drop the Voltage to 15V, the MPPT will convert the excess voltage to amps for a boost charge. The smallest and cheapest MPPT has a rated charge current of only 15A though, so there would be no benefit for your setup, they are only most effective for large systems over 1kw when applying 150V to a 70A charge rate from a 20A panel array in a 12/24/48V system.

The SunSaver can also take up to a 20A load, so you would connect your loads directly to it, it also has low voltage disconnect which will prevent the battery from discharging past 11.5V.

All of these components are rated for marine use. The only downside is you won't have a digital LCD display of the battery voltage. As you know the Sunguard doesn't have any indicators and the Sunsaver has 3 LED lights, Green for 100%, Orange for 50%, Red for < 10%.

I would suggest the Victron BMV-702 Battery monitor for a display. Though not necessary, this will give you an accurate voltage read for both batteries.

You could apply the above solution without the Victron Cyrix, though you'll only charge the batteries independently and the house battery wont charge from the alternator.

Alternative option...

2 x 150W panels in parallel to either a SunSaver Duo or BlueSolar Duo to each battery. This will only charge 1 battery at a time and will not charge the house battery from the alternator.

I wouldn't recommend connecting the 80W panel to either battery via a Sunguard or similar as the smaller regulators are not smart and could risk over charging when the Duo goes into a cycle.

I would like you thoughts on this. He seems to have quite a comprehensive store
here;

My understanding is that If I switch my isolator Switch to 1+2 the Alternator Charges both battery banks??

This guy does seem to have quite a comprehensive store though..... here:

http://stores.ebay.com.au/ontopenerg...p2047675.l2563
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Old 04-04-2015, 02:56   #15
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Re: Solar Controller

The dealer has got many things right, but also a few things wrong. There is certainly no problem connecting solar panels of different sizes as I indicated in my previous post. I would also would disagree with the advice to " connect your loads directly to it" (meaning the load side of the controller). I would also dispute the 30% gain for MPPT. The actual gain is lower than this, but if you have run out of space to put panels MPPT does provide a slight gain even for small boat systems.

I notice the controllers you have been looking at are all "dual battery" controllers. Many people assume this essential on the boat because of the separate start and house banks. Generally a single battery controller feeding just the house bank is fine. As most controllers are only single output models this gives you a much wider selection.

The start battery is only very slightly depleted by the normal engine start. This is replaced by the alternator. So normally solar input into this battery is not really needed. It is helpful to once in while (say every couple of weeks) to charge the start battery up to 100% with the solar panels but this can be be done by flipping the battery switch on to 1+2 when the house bank is fully charged. (Some boats will do this automatically with VSR). Solar will charge both batteries. If you are worried accidentally leaving your batteries combined ( this is not a big deal anyway the engine will still start) just set a kitchen timer. The only situation where dual charging via a controller, or VSR, is very helpful is if leave the boat for long periods (many months) where the self discharge of the start battery becomes an issue. In most cases you can leave the batteries in the 1+2 position, but as they are not isolated a fault such as a constantly running bilge pump could deplete both banks. There are some simple fixes for this problems with a single output controller and no VSR, but they require some electrical knowledge.

If you are not leaving your boat for long periods the Kiss approach of single output controller feeding just the house bank is actually better for the start battery and means there is much wider selection of controllers to choose from.
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