Solar panel

[DeliDave]

Would like solar panel to charge battery while van is in storage,was thinking of panel going inside skylight and plugging into 12 volt socket to keep battery charged.Anyone got any ideas on size,cost or alternatives?

 

[rob_jax]

Hi David,

This topic was recently discussed (at length) in the thread "Solar panels vs micro wind generators"

Robert

 

[DeliDave]

Thanks I,ll have a look for it

 

[DeliDave]

found it but it seems more for use instead of electric hook up all i want is to keep battery topped up as i have to use motor move to get van out of storage once on site always have electric,would just a small unit do the job

 

[rob_jax]

Hi David,

If the battery is fully charged when you put it away, then a 14 watt 12 volt panel will keep it that way - depending on the average light intensity it may be able to do more.

Like most things, the recognisable brand names are probably the "best" in terms of quality, warranty, life expectancy, etc. So Sharp or Kyocera would be a good make to go for.

Sun elevation - in the winter the sun climbs to a maximum (at noon) of 30 degrees above the horizon, 50 degrees in Spring and Autumn, and 70 degrees in Summer. These are approximate values for the whole of the UK.

The panels work best point "flat on" to the sun - so the sunlight strikes at right angles.

The skylight would be sort of OK in the Summer and terrible in Winter, but if you can arrange it, then the front or rear windows would work best - with the panel at say 45 degrees.

Robert

 

[DeliDave]

Thanks for that I'll check which way the sun goes to where it is parked,checked the battery today and its still over 12volts after 3 weeks,got to use van more.Its a big help having your knowhow on the site,been looking at DAB aerial post as well

 

[rob_jax]

Hi David,

A fully charged lead-acid battery should show a (disconnected or no-load) reading of 12.7 volts, 75% is 12.4 V, 50% is 12.2 V and 25% charged is 12.0 V.

You will note that a battery goes from fully charged to 25% - which is effectively fully discharged, and only shows a voltage difference of 0.7 volts - which is why you need a digital voltmeter to measure this change.

If you have a sealed Gel battery then expect the 100% charge voltage to read 12.8 V or maybe 12.9 V. IF you see 13.8 V or more, then either the battery is still connected to the charger or you are measuring too soon after charging - the battery needs to settle for 30 minutes or so.

Never let the battery discharge so that it drops below 12 V, and you will get the best life from the battery if you keep it above 50% charged.

Robert

 

[JohnI.Stephen]

More words of wisdom that have printed off to supplement my knowledge. Thanks Robert (What do you do for a living ?)

 

[rob_jax]

John,

I just sit here at my computer making up fake but feasible sounding stories for internet forums.

In reality, not much more.

Thirty something years ago I read Chemistry at York, then Chemical Instrumentation postgraduate studies at Imperial College (NMR instrumentation research - which 30 years on you know as hospital body scanners - only the best we could do then was scan a 1 cm cube inside a 2 tonne electromagnet).

Then paid employment at a German pharmaceutical company elucidating chemical structures of anti-cancer drugs, then worked for a Californian based company in Palo Alto designing instrumentation and software.

Then back in the UK, started my own software and instrumentation business, and after several company mergers, I'm joint owner of an international company headquartered in Rotterdam, designing and manufacturing instrumentation for the petrochemical and pharmaceutical industries.

And because of the specialist knowledge I've picked up, I chair an Energy Institute panel in the UK and represent the UK at some EN technical committees in Brussels (petrochemical and bio-fuel based motor vehicle fuels and lubricants).

Then some weekends we go caravanning.

Robert

 

[Julie_5081178]

Our 50w solar panel keeps us going - we had a month away in the summer with only that for company. TV was used approx 2 - 3 times a week for about an hour and half each time. We bought it from the NEC show and got a show offer.