Choosing the right MPPT for my Boat

[ETAP22SolarE]

Hi there I am new to Solar world and I am currently renewing the whole electrics of my little 22ft boat

I am currently wondering what kind of MPPT I should choose for my boat. my boat has currently 4 semi-flexible panels (10Years old) each about 70x80 cm which I also plan to renew soon or with the replacement of the current PWM module ...

so with a given limitation of 4 small panels in the direction of the maximal size of 60 x80cm (estimate) what kind/size of MPPT Module should I choose for 24V system?

thanks in advance!!!

 

[gnubie]

The controller you can use will be dictated by the wattage, Vmp and Voc of your panels. If you can post the panel specs (often on a label on the back, even for panels 10 years old) or link to a web page for the particular panels people can use that info to give you some advice.

You have 12V system, ie battery is 12v etc?

 

[ETAP22SolarE]

Hey, wow fast reply, sorry yes I forgot to mention the main system is 24V with (2x 12V 100Ah AGM) at the moment and I am planning to keep this due to a 24V electric propulsion motor with the plan to go LiFePO4 or any good value battery storage also soon

 

[ETAP22SolarE]

Maybe plan from my research is for example 4x https://www.solarpowersupply.nl/sunbeamsystem-nordic-54w-mc4

Merk	SUNBEAMsystem
Afmetingen	54,5 x 53,5 cm
Gewicht	1 kg
Materiaal	Buigbaar kunststof
Vermogen	54 W
Pmax - Maximaal haalbare vermogen	54 W
Voc - Voltage open circuit	25,7 V
Lsc - Ampere short circuit	3,1 A
Vmp - Voltage maximum power	19,6 V
Imp - Ampere maximum power	2,8 A
Ptol - Vermogenstolerantie	+/- 5%

what would be a good size MPPT for this...

thanks,

 

[ETAP22SolarE]

i am also open for suggestions for solar panels

 

[David Pocock]

Hi there I am new to Solar world and I am currently renewing the whole electrics of my little 22ft boat

I am currently wondering what kind of MPPT I should choose for my boat. my boat has currently 4 semi-flexible panels (10Years old) each about 70x80 cm which I also plan to renew soon or with the replacement of the current PWM module ...

so with a given limitation of 4 small panels in the direction of the maximal size of 60 x80cm (estimate) what kind/size of MPPT Module should I choose for 24V system?

thanks in advance!!!

Victron SmartSolar is a good option for LFP as there is a good range of user-defined settings. There are several sizes to match voltage and wattage.

 

[gnubie]

Since you have a 24V battery I'm guessing you have your panels 2 in series and then those in parallel. You can leave them wired like that for use with a MPPT controller. The voltages involved means you have a lot of choice.

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I'd use the Victron for reliability. If you are thinking about changing your panels the choice of controllers would be different.

 

[ETAP22SolarE]

thanks so 20A would be a good choice like https://www.bluepowershop.nl/solar/...tron-smart-solar-mppt-100-20-12v-24v-20a.html

whats the nominal difference between the MPPT 75/20 and a 100/20 that's what I wonder?

 

[gnubie]

Victron's names contain the ratings. 75/20 = max PV input (Voc) 75V, max amps (applies separately to PV input / battery output / load output ) 20 A. Both those models has a 20 A limit.

Effectively neither can put more than about 500 watts into a 24V battery (20A x 25V), but how they get that power in on the PV side can vary. The 75V version would let you put 2 of your existing panels in series, then 100V version would let you do 3 but then you'd have the 4th orphaned in the cupboard.

If you are looking at replacing your panels you should work out what wattage you are aiming for, pick panels to suit and then spec the MPPT controller to work with them. Buying a small controller now will work with the existing panels but may not be suitable for your new panel configuration.

 

[ETAP22SolarE]

Thanks so much for the Explanation!

100V version would let you do 3 in series

but I could also go for the bigger and then do a 2x parallel / 2x series with the 100V one ? or would this be not so smart?

 

[gnubie]

You sure could, in fact if you move to 24V battery it is a requirement that you put your existing panels in 2 in series x 2 parallel set to get the voltage to be able to charge the 24v battery. The power would be the same from your existing panels, but it would let you use different voltage panels if you ever replace your existing ones.

When the time comes to replace your panels you could use 12v class panels again or move up to 24v class panels. Neither are 12 or 24v, its really just a range of voltages referring back to PWM controller use.

Say you selected 4 x 100 12v class panels and the Vmp is 19.6, same as the existing ones. The increased wattage would mean more amps, about 5.1 per panel. As 2s x 2p, 39.2V (19.6 x 2) so OK for battery voltage and 10.2A (2 x 5.1A) so OK for the Victron 20 amp limit, and if they ever actually produced 400 watts, that's below the about 500 watt limit for the controller too.

Say you selected 4 x 100 24V class panels. Now the Vmp might be 36V, Voc 44V. You start to sail a bit close to the wind with the higher voltage panels if you put them in series / parallel like before. The Voc is close to 90V, too close to the 100V limit of the controller if you have very cold weather. You could put them all in parallel though, since their individual voltage is high enough to charge a 24V battery and the total amps is about 11, again falls within the 20 amp limit on the controller so all good still.

Keep in mind that both the 75/20 and 100/20 can only provide about 500 watts max to a 24v battery because of the 20 amp limit on the battery output terminals.