# 2nd leisure battery v solar panel?



## shingi (Apr 18, 2008)

Ok, all out there in motorhomeland. I've read all your why's and wherefore's on 2nd. leisure batteries, & all there is to know about solar panels. So, apart from asking "What's best?" & shouting "Fight !"  , if one has a choice of going either solar panel or second battery in parallel, which is the best option, as it seems a good gel battery versus a suitably sized solar panel will cost about the same ?


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## DABurleigh (May 9, 2005)

shingi said:


> ...So, *apart* from asking "What's best?" .... which is the best option.....?


Err, define "best". Do you think there would be a consensus of sound advice on the "best" motorhome?

Price-wise, I note a second battery is FAR cheaper than a usefully sized solar panel. And I would always have at least two leisure batteries before contemplating solar.

Dave


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## Annsman (Nov 8, 2007)

Consensus here from me! I agree with Dave! 

I'm not sure what van or how long you've had it, or how you use it, but I would get the second battery fitted, see what usage you get in lots of differing situations. i.e no hook up for as many days as is practicable, will you be able to use your usual electrical items, how often do you move off a site and for how long, because it might suit you more to get a battery to battery charging system.

I can give you our experience. We have a 2nd 110 Amp leisure battery but eventually after 12 months we decided on 2X85 Watt panels fitted by Leisurepower and it has been money well spent as far as I'm concerned. It does everything we want so I've moved away from an EFOY, which had been a firm favourite at one point.


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## Jented (Jan 12, 2010)

Hi. 
I am lucky to have 2 Batts and solar panel,"Belt and Braces",there is no substitute for power,and now i have spare capacity,equals,peace of mind. The freedom the m/home offers is wasted if you have to seek a hook up,and the weight/constrictions of a generator in todays "weighbridge" fraught times,make them a no no. Hope this helps.
Jented.


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## ColinC (Oct 19, 2007)

*2nd leisure battery v solar*

What is your payload? Ours was quite tight and as the solar panel was less than half the weight of second battery we went the solar route. Has the benefit of keeping both leisure and engine batteries charged up when not doing any driving and we do not bother much with mains hookups.

Colin


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## Patrick_Phillips (Aug 17, 2006)

There are three questions to ask:
1. How will you recharge your batteries?
2. How often will you do so?
3. How many amps will you use per day?

Then you will know how many amps you need to gain from whatever source each day, or at least how many days you can go before you take your batteries down below the 50% mark.
To get indefinite off-grid conditions you will need to put in what you take out each day but otherwise you will have a shortfall of x amps which over n days will take you down to the 50% allowed by your battery capacity.

Basic rules of thumb:
5 watts of solar panel will get you 1 amp per day.
A battery will cost £1 for every 1.25 amps it stores.
A solar panel should cost you about £2.50 to £3 per watt of power (though many will charge you much more!)

The rest is maths and alcohol...

Patrick


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## rayc (Jun 3, 2008)

Patrick_Phillips said:


> Basic rules of thumb:
> 5 watts of solar panel will get you 1 amp per day.
> 
> Patrick


Patrick, can you please explain what you mean in a bit more detail? Ray


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## kevanna1959 (Apr 5, 2010)

*re 2nd batteries*

if you fit a second battery do they both have to be brought at the same time ie both new, and do they both have to be the same amp ie 2 x 110amp or 2 x 85amp


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## DABurleigh (May 9, 2005)

In order to maximise life, paralleled batteries should be matched in terms of their charging and discharging characteristics (think "effective internal resistance throughout cycle". In order to do this, the battery type, construction, age and "history" should be similar. And the best way of achieving that is buying two new ones from the same batch.

Dave


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## Patrick_Phillips (Aug 17, 2006)

rayc said:


> Patrick_Phillips said:
> 
> 
> > Basic rules of thumb:
> ...


If you take, for example, a 180 watt panel and reckon on a resonably bright grey day you should get about half the 15 amp theoretical output or 7.5 amps but for much of the year you will only get that for a maximum of 5 hours a day so you could expect to prodice around 37 amps over the day.
Divide the 180 by the 37 shows that it is taking 5 watts to generate an amp.
I did say that it was a rule of thumb...

We have 2 x 180 at 24v and 1 x 110 at 12v feeding 3 x 110Ah flooded batteries + 1 x 90Ah sealed L/A engine battery. We use around 350 amps a day.
On an average mid winter day in Northern UK, our solar farm gets us back up to 100% by early afternoon. This weather, its back before we get up in the morning!

Hope that makes sense
Patrick


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## Patrick_Phillips (Aug 17, 2006)

Patrick_Phillips said:


> .We have 2 x 180 at 24v and 1 x 110 at 12v feeding 3 x 110Ah flooded batteries + 1 x 90Ah sealed L/A engine battery. We use around 350 amps a day.
> On an average mid winter day in Northern UK, our solar farm gets us back up to 100% by early afternoon. This weather, its back before we get up in the morning!


Should have added that we use two MPPT controllers on the 24v panels which does improve the yield a fair bit.
Patrick


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## rayc (Jun 3, 2008)

Patrick_Phillips said:


> rayc said:
> 
> 
> > Patrick_Phillips said:
> ...


Patrick, I think you are saying,but stand to be corrected, that you produce 37amps over a 5 hour period thereby putting 7.4AH back into the battery in that time. Ray


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## Patrick_Phillips (Aug 17, 2006)

rayc said:


> Patrick, I think you are saying,but stand to be corrected, that you produce 37amps over a 5 hour period thereby putting 7.4AH back into the battery in that time. Ray


Yes. To split hairs, though, I am saying that the 37 amps is all you will get back into the batteries over a 24 hour period.
The 37amps = 7.4Ah is a bit of maths I didn't bother with as it tends to open up the arguments about 20 hour etc.
Patrick


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