Solar vs alternator charging

Submitted: Friday, May 29, 2009 at 07:26
ThreadID: 69290 Views:2990 Replies:5 FollowUps:4
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We have a 100wat BP Solar (2x50watt hinged & wired together) fitted permanently to the roof of our Patrol, and are after any info as to whether it is better to charge the camper trailer 120amp hr AGM battery on the road by the alternator via an anderson plug or by the solar panel via an anderson plug. The Patrol is fiited with dual batteries - 1 standard battery and 1 marine deep cycle. Any info would be appreciated.
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Reply By: Member - John and Val W (ACT) - Friday, May 29, 2009 at 07:42

Friday, May 29, 2009 at 07:42
Grahame,

We use both, and find this very satisfactory. The auxilliary battery is switched by a controller to the alternator/cranking battery once the engine has started. The solar panels are permanently connected via their own controller to the auxilliary battery. This arrangement makes use of the higher current available from the alternator when the aux battery is low, with the benefit of the higher voltage available from the panels to top up the charge when approaching full.

HTH

John
J and V
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Follow Up By: Member - Wayne David (NSW) - Friday, May 29, 2009 at 08:10

Friday, May 29, 2009 at 08:10
John & Val

I'm always after a way to keep my camper battery charged to the max.

In your case you said "The auxilliary battery is switched by a controller to the alternator/cranking battery once the engine has started."

Do you mind telling me if this switching is automatic or is it something that you need to switch on & off yourself?

I really like the idea of SP's mounted on the roof (all the free sunshine when motoring about) but wondered iF they are likely to get damaged during travel.

I a member on this forum with a Nissan Patrol as his pic. Not too sure but it looks like he can possibly even swivel the panels on the car roof when camped or at least he can alter the angles. I suppose the car just gets moved for the best directional advantage.

So that's a great idea for maximising the solar effect and reducing all that lugging around of those heavy panels.

Now I'm reading that it's possible to combine solar panels with car alternator & wondering why my auto electrician didn't suggest it for my application.

Finally - I really like your picture. Night camp by fire next to Boab tree. Lovely.



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Follow Up By: Member - John and Val W (ACT) - Friday, May 29, 2009 at 10:53

Friday, May 29, 2009 at 10:53
Wayne,

My switching from the alternator to the auxilliary battery is automatic. The commercial controllers make this connection after the cranking battery has come up to voltage. Initially I used such a system, but found that this point is reached virtually as soon as the alternator starts charging. So, I now have automatic switching based simply on when the engine is running (NOT just ignition on, but when there is oil pressure.) I'll elaborate on my system and blog it when I get a few minutes.

Cheers

John
J and V
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Reply By: Maîneÿ . . .- Friday, May 29, 2009 at 09:26

Friday, May 29, 2009 at 09:26
Grahame,
My Solar panels sit on the roof 24/7 and are connected direct to the 2 x parallel wired AGM's via the Solar Regulator.
They maintain the AGM's when not driving, ie; when parked any time during the day.
The ~200 Watt panel configuration is capable of delivering ~12 Amps on a good day when installed horizontal on the roof, as is shown on the 'my profile' pictures.

I connect the Cranking battery into the Accessory battery system every now an then to recharge when camped for extended periods, that way I always have a fully charged Cranking battery.

Maîneÿ . . .
AnswerID: 367348

Reply By: Member - Norm C (QLD) - Friday, May 29, 2009 at 12:24

Friday, May 29, 2009 at 12:24
Like others, my batteries are always connected to the solar panels via regulator, whether charging via Anderson Plug to alternator or not. It is a set and forget method. You take advantage of the much higher charge current available from the alternator while driving and solar whenever the sun is shining.

Norm C
AnswerID: 367382

Reply By: Mandrake - Friday, May 29, 2009 at 16:16

Friday, May 29, 2009 at 16:16
I don't have the luxury of Alternator power for my Auxiliary batteries (yet) - The only high drain item I have is a Waeco CF50 which runs off the vehicle when driving .
I have a pair of 26aH batteries in the back of the Jeep connected to 2 X 15 watt
Solar Panels on the roof .. When I park the Jeep I simply swap the fridge to the Aux Battery - In theory that gives me 4-5 hours fridge time ...
The camper has an 85aH Battery connected to an 80 watt Solar panel ..

I'm hoping that this system will work while I am away from 240v power - All of the Batteries and panels have Anderson plugs and extension leads so I can switch power to any setup I want ..
According to popular opinion here eventually I will run out of power and if that happens then I will have to consider an Alternator connection for the Camper Battery and the small Aux batteries in Jeep...

Until then the big test is on in September travelling to St George !!

Rgds

Mandrake
AnswerID: 367420

Follow Up By: oldtrack123 - Friday, May 29, 2009 at 20:41

Friday, May 29, 2009 at 20:41
Hi Mandrake
Mandrake replied:
I don't have the luxury of Alternator power for my Auxiliary batteries (yet) - The only high drain item I have is a Waeco CF50 which runs off the vehicle when driving .
I have a pair of 26aH batteries in the back of the Jeep connected to 2 X 15 watt
Solar Panels on the roof .. When I park the Jeep I simply swap the fridge to the Aux Battery - In theory that gives me 4-5 hours fridge time''


I dont know if you actually tested this setup,but 30watts is only going to put in about 2amps in bright sun ,ON a good day your total input would probably be about 12amphrs max I believe you will be going backwards.
A cheap easy way to parallell the starter& aux batts ,in your case, is to use an ignition switch controlled relay such as a head light or preferably a higher current rating relay to auto connect & disconnect the aux with engine operation This will ensure that the aux batts do get more quickly charged when you are driving.
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FollowupID: 635129

Follow Up By: Mandrake - Friday, May 29, 2009 at 22:35

Friday, May 29, 2009 at 22:35
As I sort of stated in the blurb - I do have an 80 watt panel connected to an 85aH battery in the camper - well actually on the camper so I can with an extension lead plug the 4.5 Amp 80 watt panel into the smaller battery in the back of the jeep whilst motoring - which should perk it up fairly quickly ..

I am sure this will work but I will need to be vigilant -

But we shall see what we shall see - If I find the 2 X 15 are inadequate then I'll have to move the 80 watter to the Jeep roof and put a 140 watt over the camper -- which is probably going to be the final answer - But first there is St George and 4 weeks of "Sunny" S.A and N.T travel and camping to get through as the test ..

Energy independance ... and cold beer !!

Rgds

Mandrake
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FollowupID: 635161

Reply By: RV Powerstream P/L - Friday, May 29, 2009 at 18:05

Friday, May 29, 2009 at 18:05
There is no way you can equate solar charging with alternator charging if you travel regularly.
You should maximise your travelling with alternator charging of the bulk sense and then use solar to supplement as you could not fit enough solar to match what is available and wasted from the alternator with inefficient systems.
The size of a solar footprint would exceed the size of the normal vehicle but Im sure most realise this fact.
If you travel regularly you can supply all your power from the alternator but I have a simple theory that you start with 60W of solar and then add 10Watts for every day you anticipate being stationary until you have between 120W and 160W to run your compressor fridge 24/7.What you do from there is according to your puse strings and your needs.
Ian
AnswerID: 367441

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