Timeline for How to drop the voltage of a power supply?
Current License: CC BY-SA 4.0
8 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Aug 12, 2020 at 19:14 | comment | added | Kyle B | I'm with @Bimpelrekkie. This is NOT a suitable application for a resistor, don't even try it. Or if you do, wear a full hazmat suit and eye protection so the battery acid doesn't permanently disfigure you. Dude, you can literally buy a "real" battery charger for like $10. Sometimes you just gotta suck it up and take the pre-engineered solution. | |
| Aug 12, 2020 at 14:02 | history | edited | JRE | CC BY-SA 4.0 |
added 11 characters in body; edited title
|
| Aug 12, 2020 at 13:26 | comment | added | Circuit fantasist | Try to limit the charge current by connecting a car lamp or a combination of lamps between the power supply and the battery. For example, try with two 21 W lamps in parallel or two 60 W in series... or something else (as a bonus you will also have free lighting:) You can make simple calculations but keep in mind that the lamp resistance is nonlinear (it increases with temperature). I have done it many times in the past when I was dealing with cars... and not once did a battery explode... You can enlarge this idea with some else useful ballast load (e.g. a fan:) | |
| Aug 12, 2020 at 13:00 | answer | added | Sneaky Puffin | timeline score: 2 | |
| Aug 12, 2020 at 12:57 | comment | added | D.A.S. | (21-12)/2A=4.5 Ohm. (21-11.5V)/3.9 = 2.43 A . overcurrent on low battery, manual cuttoff needs monitor in real-time. | |
| Aug 12, 2020 at 12:47 | comment | added | brhans | Resistors don't work that way. At the very least you need a voltage regulator, which could be a single component or a circuit of multiple components (some of which may be resistors). But a single resistor will not do what you want. | |
| Aug 12, 2020 at 12:39 | comment | added | Bimpelrekkie | You cannot and should not charge a car battery this way. The voltage is too high (more than 13.8 V) so you'll overcharge the car battery and damage it. The resistor will not limit the voltage to 14 V when the battery is full. Also explosive gasses could escape. Car battery chargers are cheap, just get one of those. | |
| Aug 12, 2020 at 12:36 | history | asked | Junaid | CC BY-SA 4.0 |