Solar power?????????

[Nicky_374308305]

Hi all!

I have been giving serious thought towards getting a solar panel, so as to charge my battery.

I only ever use car batteries, but dont have a clue what i would need to buy in order to keep them charged using a solar panel!!?

What exactly would i need to buy?

And how would i set it up?

Many thanks and kind regards

Nicky

 

[Rod_5041370]

It very much depends how you are going to use your 12 volt supply i.e. what do you expect to run and for how long?

I use an 80 watt mono-crystalline permanently bonded to the roof and a charge controller to ensure that the battery doesn't over charge.

For most short stays, using lights, water pump, 12v TV and gas for hot water, cooking and space heating, I would suggest a panel of at least 50 watts, a charge controller, 110 A/h battery plus cable, fuse holder etc.

My set up is quite sophisticated and uses a marine battery monitor which informs me what the charge or discharge current is, how many Amp/hours remain and how long it will last at the present consumption but I do take it rather seriously!

 

[ProfJohnL]

Hello Nicky

It seems that about a 50to 55W solar panel is the minimum size you need. This will keep a battery well charged (Using a proper charge controller) and cover light daily usage when on holiday.

For best 12V performance you should be using Leisure Batteries not car batteries. There is a difference in their construction that allows leisure batteries to discharge to a lower limit than car batteries. This makes the far more suitable for caravans.

 

[Nicky_374308305]

Hi.

Thanks for your reply, Rod and John L!!

John L......... The reason i use car batteries is because i got sick of buying leisure batteries and killing them!!

I only go away with my children for the 6 weeks hols, and we dont have hook up or any other mods and cons provided.

I use the battery for the lights/water.......... the basics basically!! No TV's or anything like that.

My leisure battery would last me a week, and then i would have to send it up to the farm to charge.

Years ago, i started with 1 leisure battery. The year after 2. The year after that 3.

Only come the next year and my leisure battery would be dead. Or almost dead. And last at maximum 2 days before dying again!!!!

So for the last 4 years i have stuck with car batteries. They are cheaper to replace. And like the Duracell rabbit, they keep going and going..................!!!

So can Solar panels not be used with car batteries?

Thanks again

Nicky

 

[Rod_5041370]

Yes, solar panels will charge cars batteries just fine.

 

[DeliDave]

maplins have an offer on a suitcase type including charge regulater,i think its 59.99 13 watt with 4amp regulater N00CX

 

[rob_jax]

Nicky,

Leisure batteries need to be kept continuously charged up for them to remain alive. Below about 50% charge they start to irreversibly "sulfate-up", this becomes really bad below 25%, and the battery will die if left in this discharged state.

You may not appreciate that all lead acid (car and leisure) batteries self discharge by about 0.5 AH per day. This means that if you have a 80AH battery, in around 160 days it will have bleed away all the charge and be totally flat - and that after 80 days it will have reached the self-damaging period.

If you want to keep a battery alive from one year to the next - it must be recharged at least once a month - and better yet - kept on a trickle charger that will both recharge the battery and replace the lost 0.5AH each day.

Solar (PV) panels are a good way of doing this - if you only want to keep the battery topped up - then a low powered panel - around 15 watts is good enough

If you want to have the battery recharged (by the sun) for you whilst on vacation - then as a rule of thumb choose a solar panel rated in Watts at half the AH rating of the battery - So a 40 watt panel is needed for an 80 AH battery.

If you decide to go this way, then you'll need to ask for extra advice on fitting because the higher rated panels need semi-permanent fitting.

But don't use car batteries - they die quicker than leisure batteries - and if you keep the leisure battery properly charged during storage then then will last years.

We were started on PV panels by a Swiss friend who goes "wild-camping" for three or more weeks in the summer and uses a 40 watt panel to replace the electricity used from the battery for the water pump, reading lights, and radio

Robert

 

[colin_5079068]

Nicky,

Leisure batteries need to be kept continuously charged up for them to remain alive. Below about 50% charge they start to irreversibly "sulfate-up", this becomes really bad below 25%, and the battery will die if left in this discharged state.

You may not appreciate that all lead acid (car and leisure) batteries self discharge by about 0.5 AH per day. This means that if you have a 80AH battery, in around 160 days it will have bleed away all the charge and be totally flat - and that after 80 days it will have reached the self-damaging period.

If you want to keep a battery alive from one year to the next - it must be recharged at least once a month - and better yet - kept on a trickle charger that will both recharge the battery and replace the lost 0.5AH each day.

Solar (PV) panels are a good way of doing this - if you only want to keep the battery topped up - then a low powered panel - around 15 watts is good enough

If you want to have the battery recharged (by the sun) for you whilst on vacation - then as a rule of thumb choose a solar panel rated in Watts at half the AH rating of the battery - So a 40 watt panel is needed for an 80 AH battery.

If you decide to go this way, then you'll need to ask for extra advice on fitting because the higher rated panels need semi-permanent fitting.

But don't use car batteries - they die quicker than leisure batteries - and if you keep the leisure battery properly charged during storage then then will last years.

We were started on PV panels by a Swiss friend who goes "wild-camping" for three or more weeks in the summer and uses a 40 watt panel to replace the electricity used from the battery for the water pump, reading lights, and radio

Robert

Big col says there are some good deals to be had on ebay

 

[JeremyClarksson]

Rob Jax

Although I agree with most of what you and others have said, I have to disagree with your statement

"then as a rule of thumb choose a solar panel rated in Watts at half the AH rating of the battery - So a 40 watt panel is needed for an 80 AH battery."

If you have a larger battery and your power usage is unchanged the only thing that really affects your need for a solar panel is how long you are going to stay.

We make our 110AH last about 4 days with no top up, a 20w panel makes it last appx a week.

If we had a smaller battery we would need a larger panel to get that 1 week of power not a smaller one.

I have to agree with all the other comments though.

BTW Maplins were doing a 13W solar panel for

 

[rob_jax]

Hi Garry,

I'll explain the reasoning behind the 50% ratio, which is designed to re-charge the battery each day:

1. If your daily electrical battery demand is say, 4 by 10 watt lamps by 2 hours, water pump, and say a radio / music system for 4 hours - that's a typical total of 200 watts - about 16 AH

It doesn't matter if you take that self same load from a big or a small capacity battery - it's still a load of 16 AH so you need the same sized panel to replenish this.

2. The assumption is that you won't be taking the battery below 50% because of Sulfation issues, so you'd have bought an appropriately rated battery for the task - if you only have a demand of 16 AH then a 50 AH battery would be fine, but if you're drawing 40 AH each day then a 100+ AH battery is required

3. And then you'd need a higher performance panel to replace the 40 AH daily demand.

4. A 40 watt panel - during the summer - could in theory supply between 30 and 40 AH - and rather less away from mid-summer

The idea is not to run the battery down - that shortens the life considerably

Robert

 

[rob_jax]

Colin,

On the subject of eBay as a provider of PV panels - they probably yes - the only important thing is to buy a good quality panel - and that's relatively easy, because you'd recognise the company names - like Sharp, Kyocera, etc.

A search on pricerunner, kelkoo, and a trawl through eBay should point out the bargains.

Robert

 

[JeremyClarksson]

So the panel needs to be bigger because of the power usage not the size of the battery and I agree if you anticipate higher usage through running more equipment or a longer stay then a bigger battery would be wise.

We do not run our battery flat I have the green yellow red type indicator and change it well before it gets to red, our TV also has a low voltage warning message which is handy.

Roll on cheap gas powered fuel cells which would supply power and hot water, they are not that far away - 5-10 years at a guess.

 

[rob_jax]

Methanol powered fuel cells were announced today as a standard fit item in Dethleffs motorhomes - and whilst the Methnol is cheap and it's conversion into electricity is very efficient, I wouldn't like to buy a replacement fuel cell

Robert

 

[JeremyClarksson]

RJ

There are some cheaper production methods coming with cells like the ones made by Ceres Power and others.

I did send an e-mail to Ceres about 2 years ago and these are the relevant bits.

I quote

"The remote power market is one of our target markets, but it is difficult to compare directly with battery technologies but I can offer the following comments.

In the caravan example you describe, I would assume that there is possibly a 200W steady load which may peak at around 500W.

We are targeting about 1kW ~ 5kW initially; below this power, the efficiency drops off markedly as parasitic loads (such as the control board, fans/blowers and thermal heat losses etc) become significant.

In addition, to absorb these peak loads, it is likely that a solid-oxide fuel cell (such as ours) would probably require a parallel-connected battery to operate.

Therefore it is difficult to envisage a direct offering (from a solid-oxide fuel cell company) to replace a battery below about 1kW.

However, there are several companies developing small fuel cell units operating on methanol (based around a polymeric membrane fuel cell technology) aimed at replacing electronics batteries, for, say a PC.

These are entering field trials at the moment and may be applicable. My personal feeling is that it is likely to be several years before any of these are commercially available in volumes significant enough for the price to be competitive.

In order to compare prices with a battery, you would also have to consider both capital cost and operating cost over the product's life - charging a battery is not an efficient process and would be costly in terms of electricity (or fuel if charging from your car).

A fuel cell unit is likely to be expensive to buy, but substantially cheaper to operate, hence the difficulty in comparing directly without knowledge of intended operation.

For applications in the 1kW ~ 5kW range, we definitely view applications on a yacht, powering mobile-phone transmitters, ground-well pumps or auxiliary power units for trucks (providing electrical load when the engine is off overnight) as likely.

I hope this provides some further information for you, even if it doesn't directly answer some of your questions."

All in all quite promising and prices will come down - Thanks for the info about Dethleffs, news to me - again promising.

The ideal I guess would be a cheap relatively low power cell that ran off propane and enabled a much smaller battery to be used - it does look like motorhomes are the obvious choice because of price, initial extra weight, battery etc.

 

[shaun_374336076]

I'd recommend that for any caravan owner - the entry level trickle chargers perfrom very poorly. Most of the entry level solar panels are manufactured from thin film (plastic) or amporphous silicon which only works for 5 years or so then degrades.

The entry level trickle charger needs to be a 10W rating and above for longevity you should purchase a monocrystalline solar panle these are typically guaranteed for 25 years to produce the rated output less 20% which is great pay a little more get something that lasts and can be moved to your next van.

For weekend and 2 weeks wild camping and caravanning you need to be looking between 30W - 55W for a solar panel that will operate and actually put back up to 3-4 amps per hour - a geally green energy battery charger with enough amps to make the purchase worthwile.

My adviuse for what its worth dont waste your money on entry level plastic solar brief cases and trickle chargers buy a ce, tuv and iso approved panel made of monocrystalline solar cells that will last a lifetime.

We purchased a 51w panel from Free Solar Energy Uk a specialist in Caravan, motorhome, camping and narrowboat 12v battery charging. There web site is here but it looks like a lot of the great products are out of stock till Jan 08 due to the christmas demand http://shop.freesolarenergy.co.uk. I found these people to he honest, value for money and you could call them for fee advise.