Portable solar panel questions

Hi all

I'm a complete novice on electrical matters (mechanicals not quite such a mystery), and despite reading various forums on battery charging issues I have some very basic questions re my planned purchase of portable solar panels.

For background, my rig is a TVan towed by a D4D Hilux, and I have 100AH batteries one each in tug and trailer, The main draw is 2x40L Engels, again one each in tug and trailer (plus the usual lighting in both). Factory fitted Projecta charger in the camper, and Redarc BMS in the vehicle. Anderson plug connections between the two.

So, questions are:
>> What size solar panels should I be looking for? (my thinking was 2x80W)
>> Do all panel set ups come with suitable regulator, or should I look for that separately? (have noted forum references to MPPT solar charge boost regulators)
>> Can I get portable solar panel kit with two Anderson plug points so I can plug in to tug and trailer simultaneously?
>> When using my generator or a 240V plug into van, if camper is connected to the tow vehicle then do both batteries charge simultaneously.

Forgive the dumb questions, but would appreciate any thought prior to spending.


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Reply By: Member - Rosco from way back - Friday, Aug 08, 2014 at 15:06

Friday, Aug 08, 2014 at 15:06
Firstly, I doubt 2x80W would be sufficient. I have an 80W roof mounted panel + an 80W portable and together they are not enough to run my 60l Waeco as a freezer off a 120 AH batt .. as a fridge, not a problem, but not when running full stick as a freezer.

We also have a 130W for the camper which runs a 70 odd litre Engel happily as a fridge.

Have you considered mounting a large panel on racks over your cab, maybe a 130W on a pair of racks. Some ppl reckon it doesn't work for them as they like to park in the shade however I've had a roof mounted on 2 rigs for over 10 yrs and it certainly suits us.

Most, but not all panels come with a regulator (it's your choice). If roof mounting I would suggest mounting the reg near to your batt.

I would steer away from plugging one panel into both batts. I'm not sure of the implications of plugging into 2 at once, but regardless the panel would probably not have enough oomph for the job.

Can't see why you wouldn't charge both simultaneously (I do it often).

So ... I suggest 1x130W on the roof and 2x80-90 portables. They're relatively cheap as chips now. When I bought our first 80W BP panel they were $10/watt.

AnswerID: 537381

Follow Up By: Member - Wildmax - Friday, Aug 08, 2014 at 17:48

Friday, Aug 08, 2014 at 17:48
Thanks for your comments Rosco - certainly food for thought there.
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Reply By: Ross M - Friday, Aug 08, 2014 at 19:56

Friday, Aug 08, 2014 at 19:56
i also have an egg with a 120ah and a 105ah in the tub of a Dmax, so similar setup. Running a small Waeco as a freezer and a 39L Engel as fridge, in 30 C ambient temps two 80watt panels don't keep up very well at all.
An MPPT controller will give a slightly better power capture into the two batteries though.
The two panels of suitable size can be fed via a Y connection ie two Andersons to feed the input of the MPPT unit. With large (low drop) cable, the charge will be distributed to both batteries. It does on Rosco's unit too.
Your generator or 240v option? Is that through a suitable charger? using the Tvan's onboard charger?(if fitted).

If you have a smaller panel ie 60W or similar, it can be on the Tvan roof and when not with the vehicle, it can be switched with it's own regulator to maintain the Tvan battery and fridge, so when you again connect the 12v Anderson to the Tvan it's battery isn't much lower in SOC than the vehicle tub battery. Sort of parallel maintaining of both.

Possibly if it is a pulse type regulator in the TVAN then it may be able to be connected all the time. If it's lower output doesn't conflict with the vehicle aux system when both are charging it might work quite well.

I charge both with a 240v switchmode charger and still have the pulse reg connected.

Someone electrical engineer may reply with a definite on MPPT and other charge reg options to keep the whole system at peak charge.

AnswerID: 537397

Reply By: Member - Bigred13 - Friday, Aug 08, 2014 at 20:13

Friday, Aug 08, 2014 at 20:13
Hi Wildmax ,If you have a Redarc BMS ,and you want to use solar panels ,either fitted or portable ,you must bypass the normal regulator on the solar panels if you go to the BMS as it will take the voltage direct ,including the MPPT tracking ,best invention since sliced bread .If in any doubt call Redarc direct, they have the best people to set you straight .(no affiliation with Redarc ) I have fitted two of the BMS 1215S ,and they are great.
Bigred 13

AnswerID: 537399

Reply By: Malcolm 02 - Saturday, Aug 09, 2014 at 10:23

Saturday, Aug 09, 2014 at 10:23
I also have a Tvan (2008) with a similar set up except with only one fridge which I keep in the tow vehicle. On the Tvan I have mounted a 60w panel (I found that's about the biggest you could mount on the Tvan roof) permanently connected to the Tvan battery through a regulator. The vehicle battery is controlled by a Ctek dual which has a solar input, so that when camping and stationary I plug my 120w panel into the Ctek solar input (bypassing the solar panels regulator). Overnight I have the Tvan and vehicle battery's connected together with a Anderson plug extension lead (you can get them from Jaycar for a reasonable price). This system works well for me. If you are going to run one of your fridges as a freezer then I would suggest you would need more solar power especially in the warmer climates.
Hope this helps.
AnswerID: 537418

Reply By: cvhq - Saturday, Aug 09, 2014 at 13:54

Saturday, Aug 09, 2014 at 13:54
I recently travelled through central Australia running 50litre waco a fridge ,41 litre engle as freezer full of meat and icecream for 3 week trip+tv and dvd player to keep kids entertained.Have a red arc bcdc1225 battery charger which has mppt solar reg.Ran this for 3 days with out starting car on a 105 ah battery had 2 80watt solar panels wired together.Worked extremely well could not be happier.Battery /charger was in float/absorbation by end of day.
AnswerID: 537431

Reply By: Garry S3 - Saturday, Aug 09, 2014 at 22:42

Saturday, Aug 09, 2014 at 22:42
i'd go for a bigger size panels to charge up 2 x 100Ah battery.
most folding panels now come with regulator built in but I have also found that these regulators aren't very reliable. you probably need to change it after 1 year. however, they don't seem to cost a lot.
most regulator gives you the option of running 2 separate cables off to charge 2 separate battery.
as for whether your generator would end up charging the vehicle's battery, I am not sure but it should.

one way to check what size panel you should go for is to try your system without having any way of charging them and see how long the batteries last before it goes flat.
AnswerID: 537458

Reply By: Bob Y. - Qld - Sunday, Aug 10, 2014 at 07:31

Sunday, Aug 10, 2014 at 07:31
We've got a Redarc BMS and 2 120 amphr batteries in our slide on camper. Mounted a 160 watt panel on top, and originally planned to fit an extra 60 watt panel as well, but gave that idea away because of extra weight where it was to be positioned.

Plan to run 2 fridges, a 40L & 30L, but haven't done any trips to test the set-up. Think you'd need close to 200 watts of solar, unless you plan to run the genny, say every morning. If you did, you could hook an extension lead to both your BMS and the Tvan, and let each charger do it's thing.

Took a couple of photos to show you our set-up.

The panel is not in an optimum charging position, but far more efficient than flat on the roof. Noticed about 8.5 amps going into the batteries yesterday, about midday.

I've also looked at some of the flexible panels too, Wildmax, to save on rooftop weight. Just need extra $$$$ for that way.


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AnswerID: 537462

Reply By: olcoolone - Sunday, Aug 10, 2014 at 09:25

Sunday, Aug 10, 2014 at 09:25
Do you have a BMS or a BCDC in your Hilux and what other loads whilst travelling do you draw off of the aux Hilux battery whilst travelling?

AnswerID: 537472

Follow Up By: Member - Wildmax - Thursday, Aug 14, 2014 at 22:41

Thursday, Aug 14, 2014 at 22:41
BMS as I understand it. Only load when travelling is running the two fridges (one in the canopy and one in the camper), and recharging the camper battery after it's dropped charge while camping. No problems for a couple of days, but when we sit still for a week the generator gets a pretty solid workout without any solar back up at present.
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FollowupID: 821923

Reply By: Member - Wildmax - Thursday, Aug 14, 2014 at 22:45

Thursday, Aug 14, 2014 at 22:45
Thanks to everyone for your follow up, very helpful food for thought in my purchasing decisions.

Sorry for late response to those of you who took the time to reply - have been out of range for almost a week enjoying the delights of Gregory River, and trying not to shatter the peace too often with my generator !!

All the best,
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