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Hi All,
Have decided we really need to do more wild stuff to achieve the things we bought the van for.
We've 2 x 85amp batteries, and a webasto heater (uses electric for the fans). We do have satellite tv but v rarely use it.
The van came with an aircon unit which has eaten up a lot of the roof space.
LeisureTech say I'll only fit an 85w onto the roof.
As our requirement is likely to mostly be lights & heating & water pump - but we would like to be more self sufficient in winter too - my question is ..."Is an 85W panel worth the investment?"
Well, whether it is worth the money to you, you can only answer yourself.
I have 80W and find that after a night with a couple of hours TV, lights (LED), water pump, etc, the panels, in good weather in the Summer, easily keep the batteries topped up.
Problem, of course, is that with shorter days, when you will actually need more electricity, the panels will provide you with less. So, in Summer: great. In Winter you will need another solution if you are stationary and off EHU for a long time. But 2x85Ah batteries should give you some independence.
I would say it's the best money I have spent on the van..
80w panel and a 110amp battery does us fine and we usually travel with grandkids who will attempt to drain my battery by watching Tv and running the water/toilet pump as much as they can..
But also be aware of what comsumption you are actualy using, ie a TV on for a couple of hours may seem very little BUT if it's an older TV it could have a very high drain.. My old LCD TV was 48watts, so with my maths thats 4 amps per hour.. Recently I bought a 16" LED TV from Asda (Ģ85!!) that is only 20watts = 1.6 amps.. Big savings..
______________________________________________________________ Steve Tonks...
There are all shapes and sizes on the market and it's likely that you'll get more wattage and more effective use of what space you have with a mixture of panels.
I have an 80 and a 60 but wanted 200 to maximise the efficiency of my 200 watt mppt controller. I've found I can easily get 2 x 30 watt panels in as they are only 445mm wide. I would take some accurate measurements of your roof and transfer to graph paper for scale.
Once the sikaflex is open may as well stick 4 small panels on rather than 1 limited size that happens to be an easy answer for a fitter.
These can be a good solution too and worth having a 12 volt external skt fitted.
got more of a lecture than i really wanted [about 1/2hr] from the solar man at shrewsbury but part of what he said stuck
rough calculation's amp = 5-10% of wattage dependant on quality of light > 80 watt panel will put back between 4-8 amps a day
so if combined usage is say 14 amps per day and you have already got 170 amps batt power you would last 12 days but with a panel giving an average boost of 6 amps a day if you do a calculation of use 14 put back 6 you can effectifly stay out a further 12 day's doubling your independence.
he used rounded estimates all the time & gave a formula where d = draw on supply c = replenishment over my head i said so he calculated it longhand something like,
day1 170 amps in batteries use 14 amps leaves 156 gain6=162amps
day2 162 amps -----------------------"-----------------148 --"--- = 154
day3 154-------------------------------------------------140-----------146
i'm sure you get the picture, my eyes had glazed over a couple of times so i'm sure someone with a more technical background will be able to point out a few what if's but it made sense to me explained this way,
i would have thought working it out at a net loss of 8 amps a day would do but its not a proper formula???
got more of a lecture than i really wanted [about 1/2hr] from the solar man at shrewsbury but part of what he said stuck
rough calculation's amp = 5-10% of wattage dependant on quality of light > 80 watt panel will put back between 4-8 amps a day
so if combined usage is say 14 amps per day and you have already got 170 amps batt power you would last 12 days but with a panel giving an average boost of 6 amps a day if you do a calculation of use 14 put back 6 you can effectifly stay out a further 12 day's doubling your independence.
he used rounded estimates all the time & gave a formula where d = draw on supply c = replenishment over my head i said so he calculated it longhand something like,
day1 170 amps in batteries use 14 amps leaves 156 gain6=162amps
day2 162 amps -----------------------"-----------------148 --"--- = 154
day3 154-------------------------------------------------140-----------146
i'm sure you get the picture, my eyes had glazed over a couple of times so i'm sure someone with a more technical background will be able to point out a few what if's but it made sense to me explained this way,
i would have thought working it out at a net loss of 8 amps a day would do but its not a proper formula???
No, that doesn't sound right. An 80W panel might produce between 4 and 8 Amps as stated (bit optimistic I think). But your usage is in Ah (Amp hours, e.g. if you use 3 A for 2 hours you have taken 6Ah out of the battery).
Therefore, the amount of charge you put back over the day is the current the panel generates, times the amount of hours it does that.
sorry pieterv that is what i was saying the figures he gave were an 80 watt panel would produce 4-8 amps a day and average usage during a day were 14 amps whether as 2 amps for 7 hours or 1 amp for 14 hours they were all daily totals
amp = 5-10% of wattage dependant on quality of light > 80 watt panel will put back between 4-8 amps a day
I think this is wrong. The current, in amps, is produced at any one time. So an 80W panel will, in bright sunlight, produce 80W / 12V = 6.6A. Allowing for inefficiencies, we should say it will produce 4A at any one time. Sitting in sunlight for, say, 6 hours would result in 24 A.hr being put back into your batteries. This is about a third of the capacity of an 85A.hr battery.
We have a 120W panel on our roof, and in summer, we can watch the TV for 4 hours in the evening, use water pump etc, and we'll be fully recharged before lunchtime the next day.
Its a misconception that an 80w panel will produce 80w .....
All panels have 2 quoted voltages and 2 quoted amperages and by taking the 2 lower figures and multiplying them you arrive at the quoted 80w...
Typical figures for an 80w panel would be 18v and 4.4 a ...
conected to a fully charged battery via normal regulator ,you typically see a voltage of 14.5 thus if you multiply -
14.5 x 4.4 = 63.4 watts in absolute optimum conditions....
so if combined usage is say 14 amps per day and you have already got 170 amps batt power you would last 12 days ....
You are assuming that you fully discharge your batteries. This will damage them and significantly reduce their life if done a few times. I think you should be aiming to no more than half discharge them.
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