Solar power/charger ?

[garymck]

Hi,
as part of my aim to get away to dark sky sites regularly, I need a power supply.

I know nothing about solar power and using it to charge batteries. I would anticipate getting a deep cycle battery and charging it whilst away using a portable solar panel.

What do I need to get - the battery I'm OK on, it's the solar panel/charger that I'm not sure of.

EG do I need a solar panel and a separate charge controller, some panels seem to have some sort of controller attached?

Can someone please give me a bit of guidance on this?

TIA
Gary

[GrampianStars]

G'day Gary
I have 12Volt 33Ah deep cycle running my led lights in the obs
I use a 20watt poly 12 volt panel
http://www.ebay.com.au/itm/New-20-Watt-12v-Polycrystalline-Solar-Panel-20W-BRAND-NEW-SIZE-/331264460234?hash=item4d20e685ca
and you will need a regulator
http://www.ebay.com.au/itm/10A-12V-Solar-Regulator-Charge-controller-FREE-FREIGHT-/321771270666?hash=item4aeb0ff20a

My lights come on auto at dusk to dawn to cycle the battery
with an over ride switch to turn off as needed
:thumbsup:

[glend]

Some of the foldable camping type panel systems include a charge controller on the back of the panel/s, many other panels come without a charge controller. You can buy solar charge controllers for around $20 on ebay. You need to consider what your overall power requirements will be for each night and work out the size of the battery required and this will give you an idea of the size of the panel. The potential load during the night informs all the other decisions. If your running a full imaging setup on an EQ mount you will need more power than a simple goto dob, and the goto dob will use more power than a pushto dob system..

So fro your signature line I will assume your looking at the G11 mount, and you have a couple of cameras there as well. Work out the current draw or wattage rated for each device, including your laptop and any inverter required to run that, and add it up. There are a number of online calculators that can help work out the battery size required to run a load for a defined period.

Personally I take alot of battery power, a couple of inverters, a 80W solar panel and a generator. The last thing you want is for your carefully setup imaging run to die in the middle of a wonderful dark site night.

[garymck]

Thanks guys,

I figure a 120amp/hour battery ought to run my imaging rig, so thinking about a 120/180watt solar panel... Do the charge controllers have selection for normal/deep cycle batteries as my understanding is that the charge profiles on the types of batteries are different?

cheers
Gary

[loc46south]

Hi - For a portable cost effective unit with a minimum of clutter you probably be better to use a small 500 watt to 800 watt generator plus a battery charger. It would cost less and be more flexible. Despite what people tell you Solar power is expensive power. Even with solar power I still have a generator for back up power.

Geof

[lazjen]

The problem with generators is noise and in some places (e.g. some national parks) you can't use them or they're starting to crack down on their use. Something to keep in mind if you're wanting to recharge after a night out.

[GrampianStars]

I use this high end Morningstar 6amp regulator
http://www.ebay.com.au/itm/Morningstar-Sunsaver-6A-12V-Solar-Panel-Regulator-Charge-Controller-/301668074784?hash=item463cd18520

This panel would suit your needs
http://www.ebay.com.au/itm/120W-12v-Mono-Crystalline-Rectangular-Panel-FREE-FREIGHT-FREE-FREIGHT-/331297687561?hash=item4d22e18809

:thumbsup:

[glend]

There are many free camp reserves which do allow generators. The one we use every month certainly does and it's large enough that my generator does not disturb anyone (especially if you baffle the sound with a box or something similiar). The price of generators has certainly come down and if you use them to run chargers for your batteries then you always have a backup for the solar panel. And solar panels don't work at night.

[Allan_L]

I don't know if it is the same in Victoria, but in Sydney this coming Saturday ALDI are selling both
120 watt FOLDING solar panel (for $249)
■Includes foldable monocrystalline solar panel with controller, cable with alligator clips and durable carry bag

and
2000 watt inverter generator for $499
■Quiet, compact and easy to use inverter generator
■Designed to power a wide range of sensitive electrical appliances, including laptops and phones

Those are both good prices, but you probably could go cheaper on ebay.
However ALDI provide security and warranty. (and generally high quality products)

[glend]

Thanks for the heads up Allan, I might head into Tuggerah early Saturday before they all disappear.

[codemonkey]

A timely thread! Since I'm going to DIY my pier, I've been looking for the next thing to spend money on and that's probably solar.

I've got a couple of bulging discs in my back which are precarious, and, to be honest, I'm a lazy sod, so I'm a bit over carting up the ~28.5kg AGM battery I mostly use and I've been thinking about getting solar up at "the box" for a while.

I've got two batteries, I think one of them's busted though. I have my dew heater on that and I only get a couple of hours on it before voltage drops and the lights start flickering.

The main one, a 120Ah AGM, runs my mount and camera. I currently use only battery power on the laptop but that only gets me 2-3hrs and I'm thinking I'd like to be able to run that longer; probably an inverter hooked up to its own battery.

I tried plugging the inverter into the same battery as the mount and camera briefly once but the camera dropped out immediately so that's a no-go. Probably not the best idea anyway.

So now I'm thinking maybe three batteries; one for the camera and mount, one for the laptop, and one for the dew heater and other accessories.

The question is, how many panels should I get and what size? Would it be easier to have one panel to one controller to one battery? How much difference does PWM to MPPT make?

North is blocked by a large gum tree so I can face it NE, or W, but the N-NW will get a fair bit of shade, and since I understand north is the best direction to face the panels, this may play a factor.

[garymck]

Thanks for all the suggestions, think I'll see if I can score at Aldi.....have to get there early though!!

cheers
Gary

[Allan_L]

The question is difficult to answer without knowing the power draw of each application.

As it is a bad idea to put different batteries of different states in series, (The bad battery will suck the goodness out of the good battery and you will soon have two bad batteries) then the idea of one at a time or one PV cell per battery seems the simplest.

I believe the best you can expect from any PV panel is about 80% in optimual conditions. On a 120watt PV that should produce about 8amps (@12v) per hour at best. So to recharge your 120aH battery from say 50% drain may take 8 hours. but there are a lot of variables.

I am not sure what you mean by the difference between PWM and MPPT.

Hopefully someone with more knowledge will clarify.

[GrampianStars]

PWM charging algorithm slowly reduces the charging current to avoid heating and gassing of the battery, yet the charging continues to return the maximum amount of energy to the battery in the shortest time. The result is a higher charging efficiency, rapid recharging, and a healthy battery at full capacity.

The area that is enhanced by an MPPT charge controller is power loss. Lower voltage in the wires (long runs) running from the solar panels to the charge controller results in higher energy loss in the wires than higher voltage.

With a PWM charge controller used with 12v batteries, the voltage from the solar panel to the charge controller typically has to be 18v. Using an MPPT controller allows much higher voltages in the cables from the panels to the solar charge controller.

The MPPT controller then converts the excess voltage into additional amps. By running higher voltage in the cables from the solar panels to the charge controller, power loss in the cable is reduced significantly.

:thumbsup:

[codemonkey]

Thanks Allan & Rob, that was very helpful!

[OffGrid]

G'day Gary and Lee,
Before you can successfully scope some sort of battery and charging system you do really need to measure your 12vDC consumption with your rig at home.
This will then permit you to size your battery and then charging needs.

As a general rule of thumb, you never draw more than 50% of your amp hour capacity from a battery between cycles in order to give a reasonable life expectancy.

I use these little Watt Meters and find them very helpful to measure how many amp hours I consume. They measure a number of 12volt parameters, the most useful being the accumulated Amp Hours consumed.
Eg
http://www.beachloversleds.com.au/shop/voltage-meters/12v-voltage-current-meter/
Or
http://www.aussiebatteries.com.au/?rf=kw&kw=Watt+meter

There are variants of these type of meters as with prices.

Once you know your consumption, you are well on the way to being able to size solar charging systems and with them, the considerable variants that need consideration.

Steve

[astro_nutt]

Hi all. Say you use a 12 volt car battery as your power supply. Would it be feasible to charge a second car battery, (stored in a battery box in the boot), when driving around during the daytime taking in the sights, etc?
Just a thought.
Cheers!

[glend]

Certainly is feasible. Many 4wd vehicles have dual battery systems, that charge the start battery then switch over to the storage battery, based on voltage need of the respective batteries. Australian company Redarc make a good dual battery system but there are many others. You can even buy themm at Supercheap Auto. You can self install if you know what your doing, and use the correct gauge cables. Putting a Anderson plug at the back is a good idea so you can charge camper or caravan batteries on the go, and it is feasible for your soare battery to supply telescope/mount power at a dark site. Plenty of info on the Net about these systems.

[RKenning]

Hi all,
I just thought I'd comment on the Solar Panels. I have recently purchased the folding 160w solar panels sold by the 4wdSupacentre https://www.4wdsupacentre.com.au/products/bush-power.html
I haven't got a battery yet but for the price of $199 free freight, they might be worth a look.

Cheers Rob

[jenchris]

I have a charge controller on my boat that flips to the one with the lowest charge - not expensive.
Here in Oz I have a pair of foldable panels that have their own charger - I've been camping for a few days and come home with a full battery after using the battery to power lights and scope all evening.

[Camelopardalis]

120Ah :eyepop: dare I ask what exactly you're powering with that lot :question:

Rather than splashing out on large batteries and solar panels, it might be worth thinking about low consumption devices...just a thought ;)

As a frame of reference, I run my EQ6, cooled astro camera, laptop and dew straps from a 55Ah battery that will run for 2 nights with a little headroom. I then use a solar panel to recharge it within a couple of hours...