In Ray's Outdoors they have this solar panel setup which folds up into a suitcase type arrangement. Each panel has its wiring coming out of it and into what looks like a junction box, then from there into what I presume is a voltage controller, then output to 2 clamps (like jumper leads). In their case they had it connected to a Waeco battery box and from that to a Waeco fridge.
The PV unit was 150w. But on this setup, there was a JB which had what looks like a spare connection point. Would this allow a second set of panels to be daisy chained to double the output, for example, from the 150w to 300w?
I want to get something like what Ray's had set up, but not necessarily what they sell there. The woman who was there suggested that I buy a "battery box" and put my own battery in it. The Waeco one was around 40 a/h. The fridge itself uses 7a so if it's running continuously (rare or if the lid is always being opened and closed on a hot day) then the battery would last a max of 5 hrs if there's no charging happening.
I don't know how to calculate the charge rate other than what the PV puts out as i don't know how many amp/hours it will take to charge a battery from flat to full. That I suppose, would depend on battery type, huh?
The 150w panel, at 12v would output around 12a if running at max output. So, with 7a being used by the fridge that leaves 5a in "reserve" to top up the battery.
Do these things cut out automatically once the battery's fully charged? Or is that in the battery box's electronics?
What about an inverter to run some AC stuff? I know that you'd be lucky to run anything more than lights, the van's fridge and entertainment on 12v DC, but I'm trying to work out in my mind the best way to make use of the available tech, particularly if we decide to go bush or whatever where there's no mains power and where running portable gen-sets are frowned upon.
Some of the experienced contributers on the forum have put up some really good stuff on solar here. Read it all for the ideas first, before you do anything.
However IMHO those ready made folding panels are VERY overpriced and the regulators supplied with them are not very good. You could buy some individual panels and a good regulator seperately and some heavy gauge wire and do it yourself better at half the price or less.
To answer your questions.
The panels must feed into a regulator/controller unit which senses the battery voltage and switches it as required. There are basic ones and better ones too.
The panels do not give the power that the rating says. Like most things you only get somewhat less than the rated power at best, normally even less depending-----. Allow for that.
You cannot run the batteries down 100% flat or they will throw in the towel very rapidly. 50% discharge would be normal for a good battery life. Allow for that too !
Inverters are power hungry devices. You need plenty of power for them and big batteries. Stick to 12v and live simply is my recommendation to start with. Also read the good oil here.
Daisy chaining probably puts the panels in series so that the voltage will increase simlar to batteries. Two x 12 V panels will result in 24 V to controller. This is not a problem with most controllers particularly MPPTs. There are reasons to go to higher voltages for larger systems, primarily using smaller MPPTs, longer runs, and/or smaller cabling.
However, there is reason to go beyond 12 V systems for small to moderate systems with short cable runs so you probably want to set these panels in parallel, again, as with most battery systems.
Our PSWI inverter has a parasitic draw of over 50 W so we turn it off when not in use (Elaine likes it on so she can see the clock on the microwave) on rainy/cloud days or when "camped" in shade. Last year called one of the National Park CGs in Olympia National Park and asked if they had any sites where we could get good sun. The answer was "Sir, this is a rain forest with 200' (61 m) trees, you solar panels shall not be of much use."
Have noticed that LFP batteries are far more popular in Australia than in US. They are more expensive but far lighter, charge faster and completely, and can be discharged to 20% status of charge.
Took our 5th wheel over Wolf Creek Pass, Colorado today which is 3310 m (10857') and had great solar charging all day.
mjt57 wrote:1..The PV unit was 150w. But on this setup, there was a JB which had what looks like a spare connection point. Would this allow a second set of panels to be daisy chained to double the output, for example, from the 150w to 300w?
2.. I want to get something like what Ray's had set up, but not necessarily what they sell there. The woman who was there suggested that I buy a "battery box" and put my own battery in it. The Waeco one was around 40 a/h. The fridge itself uses 7a so if it's running continuously (rare or if the lid is always being opened and closed on a hot day) then the battery would last a max of 5 hrs if there's no charging happening.
3.. The 150w panel, at 12v would output around 12a if running at max output. So, with 7a being used by the fridge that leaves 5a in "reserve" to top up the battery.
4.. Do these things cut out automatically once the battery's fully charged? Or is that in the battery box's electronics?
5.. What about an inverter to run some AC stuff? I know that you'd be lucky to run anything more than lights, the van's fridge and entertainment on 12v DC, but I'm trying to work out in my mind the best way to make use of the available tech, particularly if we decide to go bush or whatever where there's no mains power and where running portable gen-sets are frowned upon.
1.. Careful here, what will the controller handle? It may not be able to handle that extra 150 W of solar power.
2.. I will drink to that. 40 Ah is far too small for your load.
3.. Solar panels don't work like that. They have a rather strange voltage and current output relationship to those who used to power supplies and batteries. The panels we use for 12 V charging develop their maximum power at around 17 V. This equates to around 8.82 A. If you draw less than maximum power their output voltage will rise a bit. if you remove all the load the voltage will rise to around 22 V when no current is flowing If you attempt to draw more power the voltage drops sharply as the current rises a little. With a short circuit across the panel it will supply around 9 A at next to zero volts.
4.. A good regulator will charge the battery and then switch its output down to a float voltage of around 13.8 V. However the rubbish controllers that are supplied in those kits will most likely just give you a fixed voltage of 14.something V constantly. In the same vein as answer 2.. you will get a much better product if you purchase your panel and controller separately.
5.. Unless you spend a few thousand dollars setting yourself up don't even consider an inverter for serious 240 V power use. You can use something like a beer can size inverter for occasional laptop use or a little bit of phone charging. You are much better off using a 12 V power supply for a laptop and 12 V chargers for small items. You will waste far less power not using an inverter, it takes 10 to 30% of the power drawn from the batteries just to drive the inverter itself. I would also be inclined to carry a battery powered radio for use in the bush.
-- Edited by PeterD on Tuesday 17th of November 2015 11:55:38 PM
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PeterD Nissan Navara D23 diesel auto, Spaceland pop-top Retired radio and electronics technician. NSW Central Coast.
