Reg­u­lat­ing so­lar power

Canal Boat - - Back Cabin -

QI have re­cently in­stalled a so­lar panel sys­tem on my nar­row­boat us­ing two 100 watt pan­els con­nected to my 12 volt leisure bat­ter­ies via a MPPT controller.

The wiring of the so­lar sys­tem is ex­actly as the di­a­gram at­tached (without the bat­tery charger but charg­ing from the al­ter­na­tor) copied from a Back Cabin item in the CB is­sue dated Fe­bru­ary 2017.

My query is: does the reg­u­la­tor on my al­ter­na­tor (I have a sin­gle 55amp al­ter­na­tor) fed to the two bat­tery banks (leisure and en­gine) via a split charge diode have any con­flict with so­lar sys­tem, or should there be a switch in­cor­po­rated within the so­lar sys­tem to iso­late any so­lar bat­tery charg­ing when the en­gine is run­ning? If re­quired, which side of the MPPT panel should any switch be po­si­tioned, i.e. in­put or out­put side of the MPPT panel? SI­MON GARD­NER

ATONY REPLIES: The controller must never be iso­lated from the bat­tery when the pan­els are con­nected. Oth­er­wise it could well set it­self to the wrong volt­age (24 volts in this case) and then dam­age the bat­ter­ies when re­con­nected. This means any switch MUST go be­tween pan­els and controller.

The so­lar controller and al­ter­na­tor reg­u­la­tor should work to­gether with no issues ex­cept in a few cases when the so­lar controller man­ages to try an equal­i­sa­tion charge or if it’s set to a higher volt­age than the al­ter­na­tor. In those cir­cum­stances and with very well charged bat­ter­ies the al­ter­na­tor controller MIGHT shut down but with such well-charged bat­ter­ies it’s of lit­tle con­se­quence apart from the charge warn­ing lamp glow­ing and the warn­ing buzzer sound­ing. No dam­age will be done.

If your split charge diode is a pas­sive de­vice (not elec­tronic) with just three thick wires con­nect­ing to it then it will be wast­ing half a volt or more of charg­ing volt­age. With so­lar charg­ing I would ad­vise get­ting rid of such old tech­nol­ogy and fit­ting a prop­erly wired Volt­age Sen­si­tive Re­lay in­stead. Then when you leave the boat away from shore power the so­lar will charge both bat­tery banks rather than just the do­mes­tic bank. Email me if you want wiring de­tails.

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