Increasing solar panel or adding battery? Which would work better?

Submitted: Saturday, Sep 16, 2017 at 12:26
ThreadID: 135599 Views:3929 Replies:7 FollowUps:11
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Hi,
I have just purchased a Jayco outback pop top caravan (17.58-3) with a 150 watt solar panel running through a TPS 1230 regulator into a 100 AH battery.

I also have a folding solar panel of which from memory is 180 watt.

What would be a better option, running the extra solar panels through the TPS 1230 giving roughly 330watts or using the existing 150 watt panel and adding a second 100 AH battery.

Primarily concerned with being able to bush camp longer and not stressing about taking the generator, we will be running the fridge on gas, lights are LED, TV is 12 v, the only other draw is a VPAP machine which will run through an inverter for the time being. The VPAP runs at 24v at 3.75 amps, we will be running the machine through a 12v to 24v converter later on. (See thread 135519)
I hope this makes sense, increase solar or battery or both?

William
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Reply By: IvanTheTerrible - Saturday, Sep 16, 2017 at 12:35

Saturday, Sep 16, 2017 at 12:35
Batteries is only there to run things during low light conditions. If the battery isn't going flat overnight then you dont need to add more. Solar panels are there to run things during the day and recharge the batteries. If everything is running all day and the battery is being fully charged then you dont need more panels
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Follow Up By: Member - William B (The Shire) - Saturday, Sep 16, 2017 at 12:39

Saturday, Sep 16, 2017 at 12:39
Thanks Ivan,
We are travelling away in a couple of weeks and will be taking the generator with us just in case, we will then take stock of usage then.
William
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Reply By: The Bantam - Saturday, Sep 16, 2017 at 13:22

Saturday, Sep 16, 2017 at 13:22
from what you have poster neither will get the job done.

If the figures on the VPAP are correct.
It will draw 7.5 amps at 12 volts time 8 hours equals 60 amp hours. there is your 100ah battery too deeply discharged for long life .... that is IF it is heathy and running at full capacity now

now for the charging demand
60 amp hours times 12 volts equals 720 watt hours, divided by 6 hours when the solar panel will be outputting it's rated capacity and you have the output of a 120 watt panel totally consumed ..... the extra hours of sun either side of the 6 peak ours will be connsumed in charging losses.

No allowance for cloud, rain or obstruction.

so JUST to run the VPAP, it would be reasonable to expect 200Ah of battery capacity and 240 watts of solar pannels ... MINIMUM.

cheers
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Follow Up By: RMD - Saturday, Sep 16, 2017 at 15:08

Saturday, Sep 16, 2017 at 15:08
I second that, no TV or lights there either. You have to over cater for the expected load and then allow more still, to make up for the days that don't yield much from the light in the sky.
I agree with the minimum. 240w 200 ah.
If recharging from a generator it can't be from the 12v charge port either and has to be via a battery charger powered from the 240v output of the generator.

The piddly 12v charge would have you running the genny all day, every day, in an attempt to bring the batteries up in charge but it will never make it from that 12v recepticle.
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Reply By: Gronk - Saturday, Sep 16, 2017 at 13:58

Saturday, Sep 16, 2017 at 13:58
Run both panels through the controller and add a 2nd battery.
If it rains for 2 days, and you haven't got the gennie, you are stuffed whether you have one or two batteries.
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Follow Up By: Member - William B (The Shire) - Saturday, Sep 16, 2017 at 19:37

Saturday, Sep 16, 2017 at 19:37
That's a good point Gronk about the rain.
It looks like another battery and wiring in the portables via a plug to the controller.
It looks like the gennie will have to travel with us for insurance.
William
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Reply By: swampy - Saturday, Sep 16, 2017 at 16:58

Saturday, Sep 16, 2017 at 16:58
hi
You can only use what u recharge
160watt = 38 Ah harvest in 24hr
200watt = 48Ah harvest in 24 hr

Consumption is based on 50% discharge limit
[balance between life vs performance ]

100ah batt = 50ah available for consumption

How we arrive at the figures ..
Average available in Aust of summer and winter 5.5hrs [peak sun hours ]
[sun outside these hrs and mppt is inconsistent so this production is a bonus]
Max prod. less wiring loss , controller loss, panel position loss =20%

basically 160--200 watt per 100ah of battery [200watt preferred ]

25amp 240v charger with at least 1 kv gene
AnswerID: 613812

Follow Up By: Sigmund - Sunday, Sep 17, 2017 at 04:52

Sunday, Sep 17, 2017 at 04:52
Av peak sun hours can be misleading. It can be as low as 1.5 - 2 depending on season and location.
Map
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Follow Up By: swampy - Sunday, Sep 17, 2017 at 08:39

Sunday, Sep 17, 2017 at 08:39
hi
peak sun hour map
http://www.rpc.com.au/pdf/Solar_Radiation_Figures.pdf
eg low 3hrs thru 7.5 hr high
low = southern Tazzy
High = northern Ozzy
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Reply By: Member - William B (The Shire) - Saturday, Sep 16, 2017 at 21:52

Saturday, Sep 16, 2017 at 21:52
Thanks every one for their insights.

Some good points have been raised.

Connecting the other solar panels and adding another 100 AH battery will cover (just) or needs but we will need to take along the generator as insurance.

I would run the gennie to charge the batteries through the standard fitment BMPRO J35A management system.

I will add the extra battery and test the system out in 2 weeks time.

William
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Reply By: Geoff K4 - Sunday, Sep 17, 2017 at 09:29

Sunday, Sep 17, 2017 at 09:29
Just remember, if you add another battery to your caravan, the battery will add another 30-35 Kgs to the van weight. check your compliance plate for GTM, and perhaps weigh the van first so then you would know how much weight you can legally add.
AnswerID: 613826

Reply By: Member - William B (The Shire) - Sunday, Sep 17, 2017 at 16:41

Sunday, Sep 17, 2017 at 16:41
So don't start a new thread,
I am thinking of a extra battery and using additional solar panels.
Does any body have opinions on the flexible solar panels.
I have just had a look at ebay and a 200 w panel only weights 2.2 kilos instead of the ones I have now (folding)that must weigh at least 20 kilos.
William
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Follow Up By: Dean K3 - Monday, Sep 18, 2017 at 18:36

Monday, Sep 18, 2017 at 18:36
Flexible like a blanket style or smaller poly-crystalline units wired together and folded like a map ?

For compactness a folding has its benefits of space saving the down side is can only really be left flat on ground or bonnet.

This is Ok middle of summer but winter panels for optimum sun rays need closer to 50 degree mark, and next to impossible to hold at that angle add wind may make them parasailign devices as well.

After reading a compare/test session results in a caravan magazine the good old foldable (suitcase) panels are still one of the best preforming units around - two reasons

A: can be angled to correct angle for optimum sun angle - you can get a smart phone app which calculates this out

B: if your having a bludge day and sitting back relaxing can move panels and follow the sun from mid morning until late afternoon.

Adding a 2nd battery giving 200ah (ish) is a good idea as long as within weights of caravan

Not sure i like the idea of a inverter being used for cpap machine - maybe a direct voltage convertor is better option but they usually designed for volt step down not volt step up
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Follow Up By: Member - William B (The Shire) - Monday, Sep 18, 2017 at 22:18

Monday, Sep 18, 2017 at 22:18
Hi Dean K3,

These are the sort of flexible panel I was looking at, flexible panels "flexible" they describe them as.

They look a bit more rigid then the fold up type, and should be able to stand up against a wall or table.

They only weigh 2.2 kilos instead of 25 kilos which is where their advantage would be, especially if I have to install a second battery.

William
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Follow Up By: Bob Y. - Qld - Tuesday, Sep 19, 2017 at 05:47

Tuesday, Sep 19, 2017 at 05:47
William,

RTM(road track marine) has flexible panels, but the backing is quite rigid. Might be the way to go?

Bob

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Follow Up By: Member - William B (The Shire) - Tuesday, Sep 19, 2017 at 09:04

Tuesday, Sep 19, 2017 at 09:04
Hi Bob,
That's the sort of thing I was thinking of.
William
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Follow Up By: Dean K3 - Tuesday, Sep 19, 2017 at 15:55

Tuesday, Sep 19, 2017 at 15:55
Understand a bit better now, my initial thoughts of where to place them esp at angle and keeping at that angle still apply, and probably have a greater chance of becoming a para-sail as they so light

One thing I would not do -is mount them permanently on any roof

I read recently (another forum page/fb ?) somebody decided to glue them onto caravan roof as it saved weight etc - same things your after.

After awhile glue perished panel went flying off and became part of the modern day roadside litter only to be discovered after a days drive.
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Follow Up By: Frank P (NSW) - Friday, Sep 22, 2017 at 09:17

Friday, Sep 22, 2017 at 09:17
A: can be angled to correct angle for optimum sun angle - you can get a smart phone app which calculates this out

You don't need a smartphone app for that. Just turn your panels so the shadow falls directly behind them. Then adjust the tilt so the shadow is as long as possible.

However there are useful apps that show what the sun's path will be during the day. If you are seeking max solar you can use these to help select the best camp site.

Cheers
FrankP

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