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Solar replacing regulator with MPPT controller


ian81

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Our 12 year old solar panel was cracked and down on output so I am in the process of replacing it with new panels.

 

Contemplating upgrading the solar regulator with a new MPPT controller.

 

However separating the earths so they all run through the controller is difficult.

 

Can I just use the MPPT controller to regulate power to the whole system rather than having separate battery and distribution unit connections?

 

Compounded by the fact that our MH using CBE electrics.

 

Thanks

 

(My understanding - maybe wrong is that MPPT controllers vary power to the load and or battery via the negative rail wheras all the positive terminals are tied together)

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ian81 - 2021-03-22 11:43 AM

 

 

(My understanding - maybe wrong is that MPPT controllers vary power to the load and or battery via the negative rail wheras all the positive terminals are tied together)

You need the manual of the controller you have in mind to know how it is configured.

However, your "understanding" is certainly at odds with my two Morningstar PWM controllers which has a "Common" ground [negative] for its battery, its Load limiting, and its solar array, and I see little likelihood of them configuring their MPPT unit any differently.

I have never used the "load" feature, I keep my eyes on that aspect not wanting to tolerate as deep a drain as I suspect it has in mind.

 

If going MPPT it is "beneficial" to use panels with a higher maximum power point voltage, [circa 36 Volts] than those typically used with 12 volt system PWM controllers [ e.g. around 18 Volts]. Wiring two near identical 18 volt panels in series, achieves the same from the array. The benefit is predominately in the better gain in lower light conditions, which in our solar application is always where we have the bigger challenges, rather than on good days where we rarely do.

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ian81 - 2021-03-22 11:43 AM

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(My understanding - maybe wrong is that MPPT controllers vary power to the load and or battery via the negative rail wheras all the positive terminals are tied together)

That may be true for your controller, but not in general. I do not have solar on my PVC, only reserved roof space, but my CTEK D250S B2B includes an MPPT. The recommended size of the only negative connection (for voltage reference) is only 1.0 sq mm. It follows that the regulation for both the B2B and solar MPPT functions, operates on the positive side. To aid this I increased the size of the positive output lead, so as to make the voltage at the output closer to the battery voltage.

 

The CTEK D250S is installed in conjunction with my CBE electrics, but I did install extra relays in order to avoid feedback loops. The CBE unit remains in its original state, and could be replaced with a standard unit if it were to fail.

 

Alan

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Quote,

 

'Can I just use the MPPT controller to regulate power to the whole system rather than having separate battery and distribution unit connections?'

 

No, regard the MPPT controller as a battery charger, it connects between the panels and battery. It takes in maximum power from the panel and converts to a suitable voltage for the battery. It fully controls the charging process. I recommend the Victron Smart range of MPPT controllers, these are easy to set up via the phone app that also indicates solar performance and battery state.

 

Whilst some MPPT controllers have 'load outputs these are not normally used in a motor home installation, ( they are used for applications like solar powered street lights)

 

The MPPT controller will have two pairs of connections, one set that's connected to the leisure battery and another set for the panel. There should be a suitable fuse in the positive feed from the battery to controller installed near the battery. Ideally the cable run from the controller to the battery should be as short as practical.

 

You do not need to make any significant modification to the CBE system.

 

I dont quite understand the comment about earths, the installation is quite simple, a negative and fused positive wire from the battery to controller battery connections and a positive and negative pair of wires from the solar panel the the controller.

 

Assuming you have the DC300 unit ts possible your existing setup solar is wired via pin 1 connector 14 ( the white 9 pin connector) and the 20 amp fuse F7, to the battery for the positive wire from the controller. You can use this connection path to the battery for the new installation if you wish.

 

If you can provide more information about the panel or panels you are intending to fit I can offer more advice regarding installation and choice of MPPT controller.

 

Mike

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I have a Votronic MPPT regulator with an output to the AES Fridge. This is only a 1 or 2 amp 12 volt power source and I do not use it. I intend fitting a 12 volt relay to supply a double USB socket for charging portable devices (phone, iPad, mifi etc.). It will only be energised when the batteries are full, which is usually mid morning onwards and the portable devices are not being heavily used. Just an idea that might appeal and the Votronic range are good controllers.
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Thanks guys for the responses. Much to think on!

 

PWM vs MPPT -no brainer as you get more charge?

 

Managed to look at an MPPT contoller and measure resistance between terminals. 0 ohms between all the positives and infinite between the negatives.

 

Looking at the Victron and Votronic options: the later looks good as it takes care of the vehicle battery.

 

Thanks for your comments

 

PS Mike have PM'ed you

 

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