In my home i have installed solar pannel in 9 years ago. (20W pannel, 12V Solar Battry 35 A, 20Hr). Where my battry is almost dead but still it is working.we can use its 8w load to max 3hrs. But in day time its work good.  So my question is, i have 12V 1A router, that i want to utilize it during power cut. But when i measure voltage its quite fluctuating from 12.3V to sometime 15V. Is it good idea to connect it directly without its adapter?  And the interesting part is i am posting this, using this method. I am afraid to blow mg router at this time.  I have no inverter, so i did cut the wire from adapter and connect it directly to router.  Please expert explain what is the better option. Please help me to sove the provlem.   Will it blow my router? How do i stabilize its voltage to 12v constantly. Can i use my 1250VA UPS for this solar battery? Can I replace Car battery to solar battery in my existing home solar pannel?
123252
I have a Huawei internet router with 12 volt 2 ampere input power.  I bought a solar panel 18V 10 watt with direct connection plug which I'm to use for the router but it seem to not working.     Please I need solution on how to make this to device work because I'm using this where there is AC power at all typically sun base device is what is needed there, I thought of connecting the 12 volt adapter direct to the panel then to router but I don't just know how well it will work.
35071
Can any one help? I purchased a solar powered PIR security light, with the intention of putting it inside my kitchen window. The PIR would be inside the window, but this does not work.  When I go outside to activate the light, it does not work. When I go inside to run my hand across the sensor, it works.  Will a PIR unit penetrate glass, or am I barking up the wrong tree?
83716
I recently bought a potentiometer to regulate the speed of two 12V/1.1A DC fans in parallel, powered by a 12V source. Its specifications are the following: Resistance= 10k Ohm, MaxPower = 0.2W. Can I connect the fans, the potentiometer and the power source in series, or do I need additional circuitry to avoid circuit damage? I feel like the potentiometer's maximum power is too low, but I may be wrong.
56600
I've search for a solution to my problem both on this site and on Google but I did not find a complete and adequate response.  I need a circuit that switches two 12v sources (one that comes from a lead-acid battery powered by a solar panel and the other source comes from the output of a 220-12v switching power supply) without the final power output being interrupted during switching (this is very important!).  Notes:  - The final power output will be used to power 12v devices (30 Ampere maximum).  - The sources voltage range is 11-14.7v  How can I switch between two 12V sources?
30982
I found the  at Digikey.  The datasheet says the device is rated for 400A @ 25C, 1200A @ 25C for 1ms, with a voltage rating of 300V and PD of 1000W.  Really?  This TO-264 package can control 400A of current all day long?  I can short out my TIG welder with it in DC mode?  How do those leads even carry 400A of current?
106345
I presume there will be opposite movements of the charged particles inside, with collision energy being exhaust as heat.   On the other hand, such a setup would probably introduce an extra noise/voltage fluctuation immunity, would also greatly simplify the circuit layout, would enable short-term high current anytime (i.e. motors, stroboscopes etc.).  Can I simultaneously charge &amp; discharge the battery? Might it cause any harm to it?
84243
I've just bought a portable battery, but the portable battery don't comes with an adapter for the house current; it only comes with a USB cable so I can charge it with my laptop. My mobile phone came with a charger, and I want to know if is safe to use that charger with the battery without problems, even though the output has a higher amperage. These are the specifications:  Battery input: 5V, 1A Charger output: 5V, 2A  Will the output only give the quantity that the input is requesting, or will the input overheat because it cannot handle all the current it receives?
23953
Is it safe to connect a battery in series to wall via adapter?  I have an AC adapter which gives me 10 vDC from the wall (220 volts). I've measured the adapter and it outputs 10 vDC. I have a 3 volt battery. I would like to connect in series to get 13 vDC.   Is this possible? Is this safe? If not, what can go wrong?
121793
I have a power supply of 5v DC 5Ah and a 12v 2Ah lead battery. I was thinking to make a circuit to switch battery line when power is off. I made a little schema, what i'd have to put instead of switch that i draw?  Here's the circuit schematics I made. Thank you
86803
I want to run a micro-controller from a 1S lipo through a 3V linear regulator. I need to measure the battery voltage however. The problem with using a voltage divider is that it would drain the battery over time which may or may not have protection circuitry built in. Since the AVR I'm using has a recommended input impedance of no higher than 10K I can't make the divider too large either.  Can anyone suggest a solution that would allow me to monitor this voltage without killing an unprotected battery over a couple of months? The circuit might enter deep sleep mode for an extended period meaning a voltage divider solution would consume the most power.    I ended up using both Hanno and Andy's solution. Thanks for all the input. Can only choose one answer unfortunately.
86994
I know it's not NEC and far from the right thing to do.  I need 30 amps at the garage.  I already have two unused 12/2 cables (w/ground) running to the garage. I was thinking to use one 12/2 cable, combine the black and white from one, put it on one phase and use another 12/2 wire, combine the black and white from that one, and put it on the other phase. The grounds of both would be tied to neutral.  In the garage I'd make a breakout box and attach each 12/2 to a wire of a 6/3. Each 12/2 would be a hot, 120VAC of a leg of the 2 double circuit breaker.   I'd be pulling about 30 amps for an electric car charger.  Please give me all the reasons why NOT to do this, and that it's a bad idea.  12/2 - Black &amp; White - Phase 1, 120VAC   > Black wire on 6/3  12/2 - Black &amp; White - Phase 2, 120VAC   > Red wire on 6/3 Ground > White on 6/3  Grounds of each would be tied to neutral/ground.
111327
I need to prototype something quickly as a proof of concept. Is it safe to use mains (UK 230V) on ? It will be going to a transformer so I can control some appliance. Or should I design a custom PCB to do this?
95773
I have a quick questions: can I safely power a LED with 3.3v without a resistor? I have some LEDs that I typically power with 5v and a 220Ω resistor, but I can only supply 3.3v at the moment.  Additionally I have push-buttons that I typically pull-down with 10kΩ resistors when using 5v. What resistor should I use in this case? Is there a general rule on what resistor should be used given the voltage?  Thank you in advanced for your help!
26160
I do understand that similar questions and maybe even the same question has been asked before, I've found them but unfortunately as a result of inexperience on my part I have been unable to adapt the posted solutions to my design specifically.  I am currently working to build the power side of my overall circuit that uses an 18650 (3.7v, 2600mAh) battery that is charged through an MCP73833 IC. The source power for charging will be a 5V wall wart power supply. What I am trying to accomplish now is to create a path or switch that disconnects the battery when the 5V power supply is connected, while preferably allowing the the 5V to be used to power the project and charge the battery at the same time.  Based on prior answers here on EE, I've heard that two Schottky diodes can be used with a little forward voltage drop; I've also seen recommendations for FET's. I'm trying not to add any more IC's to the project if I do not need too especially since I'm hand soldering all of this (not meaning FET's, but actual IC's).   Forward voltage drop is not critical since I'll need to step-up the battery voltage anyway after this circuit (to 5V for MAX7219). So it wouldn't be a big deal to run both power sources through the same booster.  My problem is that I have zero experience with Schottky diodes and even less with Mosfets. I've been reading and trying to understand but just when I think I do, I look at my circuit and my brain turns to mush.     Obviously if you see any errors within the circuit and wouldn't mind pointing them out, I'd appreciate that as well.
116586
Hi I asked  question on SU but seemed to have gotten into a bit of trouble, I was referenced here.  I am getting into doing hardware build based on things like microcontrollers and microprocessors.  I am curious how to calculate how long a battery can power a certain object.  Let's say we have a motor that says something like  3.5V and 100W   I don't have a motor yet a search lead me to this one: AmpFlow G43-500 Motor  The big G43-500 motors work great for applications that require sustained power output of up to 500 Watts (0.67 horsepower).  Specs Watts - Continuous  500 Diameter    4.3 in. Length  5.3 in. Efficiency  80% No-Load RPM @ 24V   3300 Output Shaft    11-Tooth #25 Sprocket Weight  8.6 lb The above specifications are for 24V. The motors can also be used at 12V or 18V. The RPM is proportional to the voltage so running at 12V will result in half the no-load RPM that is shown above for 24V. The lower voltage also reduces the maximum achievable torque by 50%. The motors have also been tested and used at higher voltages resulting in higher RPM, torque, and power. Shorter duty-cycles are recommended for higher voltages to allow the motors time to cool.   I also saw these specs on another site  Model                G43-500     Watts - Continuous   500         Diameter (inches)    4.3         Length (inches)      5.3         Efficiency           80%         Voltage*             24*         No-Load RPM @24V     3300        Output Shaft         Sprocket       The above specifications are for 24V. The motors can also be used at 12V or 18V. The RPM is proportional to the voltage so running at 12V will result in half the no-load RPM that is shown above for 24V. The lower voltage also reduces the maximum achievable torque by 50%. The motors have also been tested and used at higher voltages resulting in higher RPM, torque, and power. Shorter duty-cycles are recommended for higher voltages to allow the motors time to cool.   or something like that, how can I then say okay I have a  3.5 Volt 1000mAh battery  How long should it last?  If there's a formula that I can follow that would help. I am not trained EE.   [EDIT] I want to thank  for actually providing a good information to help clarify what I needed to then go do further research and learn the math behind all of this. I'd like to add  on how to calculate how much batteries you will need. I didn't go to school for engineering so this is all new to me.
49071
So I'm trying to power 2 of these  together in series. I know that I have to add the voltage of the two lights together and get a resistor that restricts the power to that level. I have a 9V battery and the lights are 3V each. I brand new to all of this, and understand almost nothing, so any help would be appreciated. Can someone help me choose the correct resistor (And how to identify that resistor with the color branding thing) so two of those lights listed above can be wired in series? Thanks!
90807
I am currently working on a project that uses a 9.8V 1000mAh battery to power a solenoid, and as I understand it (please correct me if I got this wrong.) a battery capable of delivering 1000mAh is also capable of delivering 1Ah, or 2A for 1/2 hour, 4A for 1/4 hour, etc.  So, assuming I got the above correct, I need to know how to limit the battery output current to 1.0A (My circuit would get really hot otherwise.)