Can I boost my battery charging with portable solar panel when required ?

RobDor · Veteran Member

Can I boost my battery charging with portable solar panel when required ?

Jaahn · Guru

Hi Rob,
Short answer is yes you can use a portable panel as well.
But the details need to be worked out to suit what you have. I am surprised that you are running short of power with 300W panels. I get by with 200W most of the time (and my alternator). Do you use your alternator ?
Give us moreinformation for a reliable reply. I do not like the soft type as they seem rubbish generally, and the folding type are over priced for what you get too. I have used just normal panels as portables.
Jaahn

Whenarewethere · Guru

My fridge uses about 4ah when running. 120 watts of solar is more than adequate.

Do you have the slightest of a shadow on the panels as this will bring input to its knees.

RobDor · Veteran Member

Jaahn wrote:
Hi Rob,
Short answer is yes you can use a portable panel as well.
But the details need to be worked out to suit what you have. I am surprised that you are running short of power with 300W panels. I get by with 200W most of the time (and my alternator). Do you use your alternator ?
Give us moreinformation for a reliable reply. I do not like the soft type as they seem rubbish generally, and the folding type are over priced for what you get too. I have used just normal panels as portables.
Jaahn

Yes, I can use alternator to boost charge. I assume you mean to plug in car and let idle for a couple of hours ? I have a redarc bcdc 40 amp charger which does a good job. The solar panels that are mounted on the caravan go through the pwm controller which is already in the caravan and I think this is mainly the problem maybe ? Its not an mppt type controller and not delivering enough juice to the lithiums. What I should probably do is run the panels through the solar input of the redarc, but then I wont have the led display that is mounted in the caravan already, to show me voltage, status etc. The panels are in full sun for these tests Im doing. Look forward to any advice you may have. Cheers

Whenarewethere · Guru

Is the controller using a lithium profile for charging?

It is critical that lithium batteries are not over charged.

Jaahn · Guru

RobDor wrote:
Jaahn wrote:
Hi Rob,
Short answer is yes you can use a portable panel as well.
But the details need to be worked out to suit what you have. I am surprised that you are running short of power with 300W panels. I get by with 200W most of the time (and my alternator). Do you use your alternator ?
Give us more information for a reliable reply. I do not like the soft type as they seem rubbish generally, and the folding type are over priced for what you get too. I have used just normal panels as portables.
Jaahn
Yes, I can use alternator to boost charge. I assume you mean to plug in car and let idle for a couple of hours ? I have a redarc bcdc 40 amp charger which does a good job. The solar panels that are mounted on the caravan go through the pwm controller which is already in the caravan and I think this is mainly the problem maybe ? Its not an mppt type controller and not delivering enough juice to the lithiums. What I should probably do is run the panels through the solar input of the redarc, but then I wont have the led display that is mounted in the caravan already, to show me voltage, status etc. The panels are in full sun for these tests Im doing. Look forward to any advice you may have. Cheers

Hi Rob smile

I do not think a MPPT regulator is your answer. They do work well if you buy a good one but only give a modest % more power, do not believe the 30% more in the add speils. They have other benefits too.

I would check out your system to measure what is happening. Do the panels actually put out their rated power or are they only half power. Is one panel faulty or a diode shorted or similar? Is the wiring good enough or undersized. What is the regulator set to do, bulk, float settings. WHAT IS YOUR BATTERY recommended settings. Is the wiring to the battery good enough. Just basic trouble shooting with a basic multi meter(or better one!).

Then check the things on the roof as said ANY shading ruins the panel power. Just a corner shaded, an a/c, aerial or a vent shade will kill a panel output.

Jaahn

PS I use my alternator to charge whenever I drive as I have a MH. But if i use it as a boost in poor weather I lift the engine speed up a bit well above idle to get a good charge quickly. Say 1500-2000RPM is good with something on the throttle.

-- Edited by Jaahn on Sunday 14th of November 2021 09:06:49 AM

Mike Harding · Guru

You live in Cairns apparently so I would expect your 300W of solar panel to readily produce 10A even on cloudy days and 15A+ on sunny days.

A 12V fridge (assuming no freezer) in Cairns will use around 35Ah per day so you need 3.5+ hours each day to keep the batteries charged - throw in lights/water pump etc and call it five hours a day - this should be readily achievable in Cairns.

You have 200Ah of lithium which take seven days to flatten themselves: call that 180Ah over seven days equals 26Ah per day which suggests your solar panels are doing very little charging.

Whilst you may have a damaged panel I'll take a guess that your solar controller is doing a very poor job. Do you have a multimeter with which you can measure how much current is flowing into the battery from the controller? With a PWM controller this is not a definitive measurement but it may provide an indication. Otherwise toss the solar controller in the bin and buy a known quality brand.

I'm assuming your panels are spending the majority of their time in sun as opposed to shade? If that is not the case then more panel real estate is needed.

As an example: right now (11am), in the forest in Victoria and on a day of 8/8 cloud and it's raining on and off, I have 800W of panels which are producing 175W and via a Victron 100/30 controller are putting 12A into my batteries.

yobarr · Guru

Mike Harding wrote:
You live in Cairns apparently so I would expect your 300W of solar panel to readily produce 10A even on cloudy days and 15A+ on sunny days.
A 12V fridge (assuming no freezer) in Cairns will use around 35Ah per day so you need 3.5+ hours each day to keep the batteries charged - throw in lights/water pump etc and call it five hours a day - this should be readily achievable in Cairns.
You have 200Ah of lithium which take seven days to flatten themselves: call that 180Ah over seven days equals 26Ah per day which suggests your solar panels are doing very little charging.
Whilst you may have a damaged panel I'll take a guess that your solar controller is doing a very poor job. Do you have a multimeter with which you can measure how much current is flowing into the battery from the controller? With a PWM controller this is not a definitive measurement but it may provide an indication. Otherwise toss the solar controller in the bin and buy a known quality brand.
I'm assuming your panels are spending the majority of their time in sun as opposed to shade? If that is not the case then more panel real estate is needed.
As an example: right now (11am), in the forest in Victoria and on a day of 8/8 cloud and it's raining on and off, I have 800W of panels which are producing 175W and via a Victron 100/30 controller are putting 12A into my batteries.

Hi Mike.The highlighted comment above is pretty well right on the money,as the generally accepted figure in Queensland for peak sunshine is 5.4 hours per day.This is what is to be used when doing calculations,but if the panels are installed East and West you'll get power,in varying amounts,from sunrise to sunset.On a house,East and West will beat North every time,if we're talking USABLE power.Cheers

Mike Harding · Guru

yobarr wrote:
if the panels are installed East and West you'll get power,in varying amounts,from sunrise to sunset.On a house,East and West will beat North every time,if we're talking USABLE power.Cheers

An interesting comment Yobarr.

I'd not be surprised if that were the case although I suspect latitude will be a factor. I'll give it a try over the next few months and see what happens.

My, four, panels are portable and I have two which face north constantly but the other two I move two or three times during the day. Of course, given my nomad lifestyle, it's hard to produce a consistent experiment. Still... it'll give me something to fiddle with and may keep me out of trouble :)

yobarr · Guru

Mike Harding wrote:
yobarr wrote:
if the panels are installed East and West you'll get power,in varying amounts,from sunrise to sunset.On a house,East and West will beat North every time,if we're talking USABLE power.Cheers
An interesting comment Yobarr.
I'd not be surprised if that were the case although I suspect latitude will be a factor. I'll give it a try over the next few months and see what happens.
My, four, panels are portable and I have two which face north constantly but the other two I move two or three times during the day. Of course, given my nomad lifestyle, it's hard to produce a consistent experiment. Still... it'll give me something to fiddle with and may keep me out of trouble :)

Trust me Mike,if your panels are indeed all portable,face them East until around midday,and then West,unless you want to regularly move them,as a Suntracker system would do.In the winter months they need to be stood up a bit more,and sometimes face North,but in a fixed panel system on a house,East and West will beat North every time.Bear in mind that a mobile system is a little different from a fixed system.When I last saw a solar system installed on a Police Bus,all panels were on fixed racks,some West and some East.PC was on to it,and the bus was being driven with the panels still in place,another advantage.Cheers

Mike Harding · Guru

Hi Yobarr

Easy enough to do, I'll give it a go and report back :)

watsea · Guru

Here is one link regarding orientation of solar panels:
www.solaranalytics.com.au/community-news/orientation-how-it-affects-solar-panels

Jaahn · Guru

Hi Mike smile

I think that Yobarr's system works best when closer to the equator and the sun is higher in the sky and over the middle of the day the both sides get sun. As you move south, facing the panels north is more important. Then move them several times a day, east north, west. change the angle too. aww

There is a lot of information about pointing of panels for fixed applications. But having them movable works well too. The solar farms do that and equatorial mounting is best to cater for the earths movement in smaller groups. Like a star telescope mounting. You could use the mount for panels in the day and stargazing in the night. wink

Jaahn

peatop · Senior Member

I have a fridge that uses around 6 Amps on startup but the general use over 24 hours is about 26-28 Amps, recently I camped offgrid for 4 days using 2 145w panels in series and a 20 amp mppt controller, this kept my battery (120Ah AGM) fully charged each day in part sun part cloudy and part rainy conditions, my suggestion is to check your panels output and also the controller, my 20Amp dc to dc charger was never intended to top up the battery unless I have a real need to use it. I have also got another 100w panel as as spare also a PWM controller as a spare, I bought a 200w blanket for backup only but now that I have seen what my system does I very much doubt it will get much use.

Since that trip I have built a 105Ah lifepo4 battery and charged it using my solar setup and it had no issues pumping the Amps in through the 100/50 Mppt or the 30Amp PWM controller. both controllers were reading 8 Amps at 36V although I was repositioning the panels to best collect the rays.