# What size regulator

Discussion in 'Solar Power' started by MikeandCarolyn, Jul 18, 2010.

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How do you calculate the size of regulator required ?
We have 2x80w panels,so what regulator should we have,and what would be the effect of having one that is lower than it should be ?

Mike.

2. ### scotjimlandFunsterLife Member

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Hi

total wattage divide by 12v .. = amps

in your example , 160/12 = 13.3 Amps ..

always better to get slightly larger, so a 20A regulator would be fine , also gives you a bit extra if you add another panel ..

too small and it may/will burn out

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If it's too small would that also affect the reading I get on my battery condition monitor ?
I get 14.4v and a max of 5.2amp on a sunny day.

4. ### scotjimlandFunsterLife Member

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The maximum voltage output from the panel is about 17v .. the regulator reduces this to the correct charging voltage , as you have observed, 14.4 v

If you have a volt meter, measure the input to the regulator on a sunny day, if it is well below 17v the you may have a poor connection .. or the cable isn't heavy enough for the panels.. as 5.2 amps sounds a bit low..

if unsure about how to check have it checked by a competent solar panel installer ... especially the cable size as far too many are installed with inadequate sized cable..

some spend hundreds of pounds on panels then skimp on the proper sized cable

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Panels

Just had two of the same panels fitted ,plus two extra 115 batteries ,I was told a 20 amp control panel was more than enough. Does your system charge vehicle battery? as mine doesn't. My vehicle however charges all when running as does the electric charging system fitted under driver seat when on hook up so dont fully understand why the panels only charge the three leisure. Also I cant work out why if the 12V isolator switch is turned off nothing works. But if on electric hook up all the 12v system works of the charger? even 12V isolator switch is turned off probably a simple reason behind it.
Alan

6. ### hilldwellerFunsterLife Member

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Not if it's limiting current to hold 14.4V.

7. ### pappajohnFunsterLife Member

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isolator switch will be between battery and control panel...

charger/power supply will be between isolator and control panel...

soooo...with isolator switched off, the charger/power supply will feed the panel only...and all 12v via the panel.
with it switched on, it will feed the panel and charge battery simultaneously.

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how long

Hi
How long should it take to charge ,on average 2 x115 leisure batteries and 1 x 850 leisure battery wired together?

I have also Just had a switch connected today,via auto electrician ,if turned over transfers load to vehicle battery for trickle, charge/booster..

I was hoping the system would give me at least three or four days of site before I had to connect to an electric hook up to fully recharge batteries . I suppose be trial and error for a while till I get used to it.:thumb::thumb: Alan

9. ### pappajohnFunsterLife Member

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too many variables to give a proper answer.
how much output from panels and for how long per day.
what output is the mains charger.
how discharged are the batteries.
will you use any power while charging or everything turned off.

in a perfect world, a 15amp charger should fully recharge your batteries, if they are discharged to 50%, in around 11hrs...it takes considerably longer in real life.

solar panel is constantly charging in daylight...even if theres no sun.