 Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me. |
Forum Index : Electronics : Electronics help needed.
| Author | Message | ||||
| Mickus Newbie  Joined: 14/11/2011 Location: AustraliaPosts: 17 |
I am hoping someone can give me some direction. I have absolutely no knowledge of electronics unfortunately. I wanted to make a system that uses wind and solar to charge a battery. I was hoping both could input to the battery at the same time. Would this be able to have two sources into it? 
Specifications: * Input: 14 to 22V (open circuit voltage), nominal 12V * Max. input current: 5A * Inrush voltage: battery voltage < approx. 13.2V * Interrupting voltage: battery voltage > approx. 13.9V * Own power consumption: <3.9mA (LEDs on) * Dimensions: 72 x 50 x 34mm Would each source going into it need a diode (not sure what sort) that would stop them feeding back into the other source. IE the solar panels sending power to the wind generator? I wanted to charge a battery or two for a camping fridge (unsure how much it draws) and 1-2 small led lights. The batteries I was looking at are: 12V 9Ah SLA Battery Rated capacity: 12V 9Ah 20 hr rate: 600mA (12Ah) 10 hr rate: 486mA (4.86Ah) 5 hr rate: 864mA (4.32Ah) 1 hr rate: 3.24A (3.24Ah) Discharge current max: 135A for 5 sec Initial charge current: 2.7A Cycle voltage: 14.4 - 15V Standby voltage: 13.5 - 13.9V Size: 150(L) x 65(W) x 93(H) 0r 7.2 Amp Hour 12V Sealed Lead Acid Battery SLA • Size 151(L) x 65(D) x 101(H)mm • Charge current 720mA for 10-14 hours • Discharge current 20 hr rate 350mA Capacity: • 20hr rate (0.35A) 7.0Ah • 10hr rate (0.67A) 6.7Ah • 5hr rate (1.19A) 5.95Ah • 1hr rate (4.00A) 4.0Ah • Int Resistance: • Fully charged (20°C,68°F) 25m Ohm • Max Discharge Current (5 sec):40A • Constant Voltage Charge: • Initial charging current < 2.1A Cycle: • Voltage 14.40V~15.00V @ 20°C (68°F) • Temp Coefficient: - 30mV/°C Standby: • Voltage 13.5V~13.80V @ 20°C (68°F) • Temp Coefficient: - 20mV/°C Are these considered robust enough to travel and be in a hot environment? (kept in shade) Also with batteries, at what volts does a 12v battery start charging. I thought (which I found out is wrong) that batteries would charge no-matter what voltage went into them, within reason, ie; a VAWT producing 3.4v would slowly charge a 12v battery. Any help is greatly appreciated. |
||||
| davef Guru  Joined: 14/05/2006 Location: New ZealandPosts: 499 |
A battery only accepts charge when the external voltage is higher than the battery voltage. Or else the battery supplies current to whatever is "trying to charge it". Yup, a series diode in each source will allow them to charge the battery when one or both source voltages are higher than the battery voltage. General purpose silicon diodes rated say 100Volts PIV and 5Amps should be pretty easy to find. Those batteries sound pretty small to me. 13V at 5 Amps (what the controller is capable of) is way over the charging current of the SLAs. How many Amps were you hoping the solar panel and/or wind turbine was going to supply? |
||||
| Mickus Newbie Joined: 14/11/2011 Location: AustraliaPosts: 17 |
The solar panel I was looking at is: 12 Volt 1.26 Watt Solar Panel - Voltage (max): 18V- Current (max): Up to 70mA- Panel Size: 159 x 175 x 17mm - $45 or 12V 4W Briefcase Solar Charger - $40 Specifications Pmax 4W Voltage (max) 18V Current (max) 220mA both are cheap and able to be stored in the back of my car. Regarding the batteries, there are bigger sizes at Jaycar that I will check. I wanted to make a plastic box with batteries and charging unit in it and all I would do is park and plug in solar panels and/or wind gen. I will mostly be using it when fishing on the beach, so solar will always be around to collect. I have ordered some books on electronics (very basic) to start learning from. My main problem is the theory of electronics which you have helped with, regarding how batteries charge. There is a battery on the jaycar site. 12V 12Ah SLA Battery Rated capacity: 12V 12Ah 20 hr rate: 600mA (12Ah) 10 hr rate: 1.08A (10.8Ah) 5 hr rate: 1.92A (9.6.A) 1 hr rate: 7.2A (7.2Ah) Discharge current max: 180A for 5 sec Initial charge current: 3.6A Cycle voltage: 14.4 - 15V Standby voltage: 13.5 - 13.9V Size: 150(L) x 100(W) x 93(H) I dont understand the info about the hr rates, will try to find out about this. The amps from the wind gen is still unknown as I am in the planning stage of making it. As its my first attempt at this stuff, it could take a while. If the controller is attached to the batteries can a pos and neg still come off the terminals and go to a 12v socket to accept the fridge and lights using a 12v twin socket? Would this cause any problems if the battery is big enough? the fridge I was looking at uses Ave. power consumption: 0.86 amps/hr, does that mean it can run off the battery above for more than 20hrs (it can supply 12amps over 20hrs) Regarding the controller being well over the rate of the batteries, will that open up the possibility over charging the battery or charging too quickly or causing a fire or cell problems in them. Sorry for so many questions. |
||||
| davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499 |
If the controller is attached to the batteries can a pos and neg still come off the terminals and go to a 12v socket to accept the fridge and lights using a 12v twin socket? Yes Would this cause any problems if the battery is big enough? Batteries and the charging system are "matched" for economical reasons. There is a balance between the size of the charging system, battery capacity and amount of power you want to draw from the system. You want enough storage to last you through the cloudy windless days and you want enough charging "power" to cope with those demands. does that mean it can run off the battery above for more than 20hrs (it can supply 12amps over 20hrs) No, it can only supply .6A for those 20 hours and your fridge uses .86A/hour, so it would be more like the "10hr rate". Also, remember that charging batteries and discharging them are NOT 100% efficient processes. Regarding the controller being well over the rate of the batteries, will that open up the possibility over charging the battery or charging too quickly or causing a fire or cell problems in them. No, the controller should terminate charge when the batteries are full. That charge controller is "over-sized" for the size of your batteries and charging system. But, it will be more useful as you increase your charging resource up to 5amps/hour and your battery capacity. |
||||
| Mickus Newbie Joined: 14/11/2011 Location: AustraliaPosts: 17 |
Thanks for the help Dave. I see your point about the fridge using 0.86a an hour., I didnt realise that the 20 hr rate: 600mA (12Ah) means 0.6A.(no electrical knowledge on my part) I might look at using two of the same battery in the setup as theoretcally it could only run 10hrs and like you said chargeing and discharging are not exact measurements. I will research battery banks for the next stage. Now that I understand the numbers regarding amps, I see the solar panels I have put in my post are well under sized as during the day it would need to charge the battery as well as run the fridge. So that means the panel needs to put out 0.86a plus more to go into the battery for night time and use of lights. The specs of the panels I include would mean I needed at least 5 of them. I like the travel size and sturdy construction so I will start looking at bigger ones. With the panels I included, they say they output 70a and 200a. Is that per hour under perfect conditions? That would mean 4hrs of sun could give enough amps for 1 hour use of the fridge. I doubt I will be able to get much out of the wind gen I am looking at making. |
||||
| aargee Senior Member  Joined: 21/08/2008 Location: AustraliaPosts: 255 |
Mickus, You're saying the fridge draws an average of 0.86A. Does the fridge run of 12V or 240V? 0.86A for a fridge seems a bit low for 12V. - Rob. For crying out loud, all I wanted to do was flash this blasted LED. |
||||
| Mickus Newbie Joined: 14/11/2011 Location: AustraliaPosts: 17 |
The info given on the Waeco websites says 0.86 amps/hr. I don't know if that's high or low. The fridge can run both 12/240 link to it is: http://www.waeco.com.au/products5.asp?id=334&catId=57&subCat Id=60&subCatId2=69 |
||||
| davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499 |
Roughly 300Watts per day. 85Watt PV panel, say 7 hours of full sunlight is about 600Watts. That just keeps the fridge going for one or two following cloudy days. You need to store about 50-60Amp/hours at 13V from that sunny day. Keep batteries more than 50% charged, so you are looking at 100-150Amp/hours worth of deep cycle batteries. |
||||
graynomad Senior Member Joined: 21/07/2010 Location: AustraliaPosts: 122 |
A fridge with Danfoss-style compressor of BD35 size will use maybe 2A @ 24v when running. The Waeco figure will assume a certain duty cycle which in turn assumes a certain ambient temp, this may or may not apply to you. ______ Rob Rob Gray, AKA the Graynomad, www.robgray.com |
||||
 Print this page |
