Solar Charging / How Long From Flat ?

RS_rob

Free Member
Joined
Dec 14, 2013
Posts
1,010
Likes collected
669
Location
Turnford
Funster No
29,372
MH
C Class
Exp
over a Year Yay................
This is a theoretical question prior to actually putting it in to practice.
My MH has a solar panel possibly 100 watt I don't know fer sure as there are no markings to determine the size.
My leisure battery is 85amp & I only have the one for now.

So assuming the above & taking into account I have flattened my battery overnight say using a plugged in fridge (& this is not a question of how long my cool box will last on battery)

How long would my battery take to charge on solar alone...................?
 

Minxy

LIFE MEMBER
Joined
Aug 22, 2007
Posts
33,684
Likes collected
70,358
Location
E Yorks
Funster No
149
MH
Carthago Compactline
Exp
Since 1996, had Elddis/Swift/Rapido/Rimor/Chausson MHs. Autocruise/Globecar PVCs/Compactline i-138
.... how long is a bit of string! Depends on how much light there is for a start ... and whether you've totally stuffed your batteries in the process of letting them go flat ... best to get a second battery fitted to take advantage of all the power the solar panel is producing on a good sunny day then you won't ever have to find out! :D
 

BwB

LIFE MEMBER
Joined
Apr 3, 2011
Posts
920
Likes collected
1,174
Location
Suffolk UK
Funster No
15,893
MH
Resting b'twix vans
Exp
Since 1990
As a rough guess I'd allow a week of average summer weather and assuming no other draw on the battery during that time.

But, as stated already, lots of other factors and equipment efficiencies involved.
 

Munchie

LIFE MEMBER
Joined
Jul 28, 2007
Posts
8,921
Likes collected
12,581
Location
Camping Les Vigeres
Funster No
26
MH
Font Vendôme
Exp
Since 2004
A plugged in fridge?

It would be flat in no time!!! That is why m/home fridges only run on 12v when engine is running!
 

DBK

LIFE MEMBER
Joined
Jan 9, 2013
Posts
18,589
Likes collected
51,056
Location
Plympton, Devon
Funster No
24,219
MH
PVC, Murvi Morocco
Exp
2013
The question is further complicated by the fact that whatever drained the battery overnight might also be running during the day, diverting the solar power.

The panel also won't produce 100w, perhaps only 30 averaged over a 12 hour period, it depends on the season, weather and latitude.

Subscribers  do not see these advertisements

 

Wildman

Free Member
Joined
May 30, 2008
Posts
0
Likes collected
8,471
Location
Ilfracombe, Devon
Funster No
2,913
MH
Amazon Ambassador
Exp
since 1967
well at midday your solar may produce 5 amps the est of the day 2-3amps, assuming you only depleted the battery by 50% i.e. 42.5 amp/hrs then I'd guess on average 2 days to really recharge it, not just to show 13.8V which would only be the charge voltage anyway. If the fridge or cool box is still plugged in the you have probably killed the battery anyway. Should only be on 12v when the engine is running. If you must run a compressor fridge or cool box on 12v then it should be connected to the load terminals of the solar controller so that the controller protects the battery and switches off before any damage is done and then remains switched off until the batteries have recovered a bit.
 
9

9526

Deleted User
Wildman's figures are a good guide.

In my experience with a 100w panel a sunny day will give you 20-30 AH's worth of charge.

Scotland less so, the South of France more so :)
 

Don Quixote

Free Member
Joined
Jul 29, 2012
Posts
2,966
Likes collected
5,262
Location
Lost in La Mancha, Spain
Funster No
22,171
MH
VW T6 Campervan
Exp
Not long enough, but a little common sense helps..........
Sorry guy's, but UK sun you have NO chance of fully charging a battery.
Average UK day 100 watt panel 15/20 amps MAX, why watch your solar charger ( that is if you have one with an amp read out ) 1 second you have 3 amps next second you have .5 of an amp because of cloud or angle of sun to your panel on the roof. So if NOTHING is connected to battery at all other then solar panel it would at best take 5/6 days, however as it is connected to the MH and drawing amps however little that is it WILL never charge ONLY "Top up" the battery.
Average MH draws 3 amps an hour ( lights, pump, etc ) but most these days draw around 5 amps an hour (lights, pump, TV, DVD, phone the list goes on and on ) so: 5 hours at 3 amps is 15 or 5 hours at 5 is 25 amps.......... but your UK 100watt panel is only giving you 20amps.......... So to answer the OP'er NOT A CHANCE of CHARGING BATTERY alone. Sorry
 

Wildman

Free Member
Joined
May 30, 2008
Posts
0
Likes collected
8,471
Location
Ilfracombe, Devon
Funster No
2,913
MH
Amazon Ambassador
Exp
since 1967
solar has accounted for 100% of my motorhome charging for the past 5 years, whilst there is less sun than spain it does work in the UK. My 2nd battery bank is not connected to the alternator only the solar. Batteries are normally fully charged by lunchtime even when overcast. It is a matter of how much battery power and how much solar you have.
 

Don Quixote

Free Member
Joined
Jul 29, 2012
Posts
2,966
Likes collected
5,262
Location
Lost in La Mancha, Spain
Funster No
22,171
MH
VW T6 Campervan
Exp
Not long enough, but a little common sense helps..........
Removed by me.....

Subscribers  do not see these advertisements

 

Brian and Jo

LIFE MEMBER
Joined
Sep 24, 2007
Posts
3,002
Likes collected
6,451
Location
oswestry,shropshire
Funster No
368
MH
A-Class N+B Arto 88F
Exp
Been motorhoming for 15yrs.had an American RV for 7yrs,Now got a Niesmann Bischoff Arto 88F
correct me if im wrong but I didn't think solar panels would charge a battery ,only trickle current to keep them topped up.if the battery has been totally flattened then there is no chance of the solar panel bringing it back to life.
Brian & Jo
 

Wildman

Free Member
Joined
May 30, 2008
Posts
0
Likes collected
8,471
Location
Ilfracombe, Devon
Funster No
2,913
MH
Amazon Ambassador
Exp
since 1967
4-5 amps is a decent charge rate, I suppose it all depends just how low a battery has been discharged, below 10.5v irreparable damage has been done anyway. Plus you cannot charge a "dead" battery any more than a conventional charger can.
 

Don Quixote

Free Member
Joined
Jul 29, 2012
Posts
2,966
Likes collected
5,262
Location
Lost in La Mancha, Spain
Funster No
22,171
MH
VW T6 Campervan
Exp
Not long enough, but a little common sense helps..........
C
correct me if im wrong but I didn't think solar panels would charge a battery ,only trickle current to keep them topped up.if the battery has been totally flattened then there is no chance of the solar panel bringing it back to life.
Brian & Jo
Correct.................
 

Don Quixote

Free Member
Joined
Jul 29, 2012
Posts
2,966
Likes collected
5,262
Location
Lost in La Mancha, Spain
Funster No
22,171
MH
VW T6 Campervan
Exp
Not long enough, but a little common sense helps..........
4-5 amps is a decent charge rate, I suppose it all depends just how low a battery has been discharged, below 10.5v irreparable damage has been done anyway. Plus you cannot charge a "dead" battery any more than a conventional charger can.
4 or 5 amps at 14.4 volts is charging at 13.???? is topping up.
 
Joined
Nov 12, 2010
Posts
149
Likes collected
83
Location
Northamptonshire
Funster No
14,422
MH
Hi Top
Exp
5 Years
from a different view, when not in our MH we live on a narrowboat, this boat is fitted with 4 * 110 AH leisure batteries, it also has a 100 Watt solar panel.
If we leave the boat moored up and go elsewhere, like a funster meet and the batteries are flat! when we come back 3 days later the batteries are fully charged and that is with a 12 volt fridge running all the time.
I can assure you the boat seldom goes anywhere other than UK ( sorry England) and thus that is the sunshine levels we are used to.:)
I base my evaluation of battery state on a fairly sophisticated battery management system and good number of years living at the mercy of battery state.

Subscribers  do not see these advertisements

 
Joined
Nov 18, 2011
Posts
12,035
Likes collected
46,129
Location
In the van
Funster No
18,938
MH
A van
Exp
Over 25 year's
I don't know what I have done wrong but I made my solar panel lest year flattened my battery's completely dead after leaving the light on when it was in storage over winter
I replaced the controller after I got out of hospital six days later the battery's were fully charged and all green in the indicator window.
Wee have ben away for a full week using TV lights DVD's game stanchion's was off grid no power problems
bill
 

Join us or log in to post a reply.

To join in you must be a member of MotorhomeFun

Join MotorhomeFun

Join us, it quick and easy!

Log in

Already a member? Log in here.

Latest journal entries

Back
Top