 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 : Microcontroller and PC projects : 5V Power Supply
| Author | Message | ||||
James_From_Canb Senior Member  Joined: 19/06/2011 Location: AustraliaPosts: 265 |
I recently bought two items from DX that I think would make a good power supply for a Maximite. It charges via USB and outputs 5V through the USB connector. It uses 2 x 3.7V batteries - I used these. Each battery is 1800 - 2000mAh so they should provide power for a fair while. They fit into a case with a built in voltage adapter. The batteries are $6.30 for two and the case is $US4.67. No cables are provided. My quality complaints are that the case only fits unprotected batteries (the protected ones are much too long), and that there are such tight tolerances. The batteries are a tight fit, and the plastic top cover only just fits. There's a raised connector on the positive end of the batteries that makes fitting the cover difficult. It will go on, but it takes some effort - or at least it did with mine. Still, it looks useful and inexpensive. Edit: Added mAh rating for batteries. James My mind is aglow with whirling, transient nodes of thought careening through a cosmic vapor of invention. Hedley Lamarr, Blazing Saddles (1974) |
||||
palcal Guru  Joined: 12/10/2011 Location: AustraliaPosts: 1873 |
The problem with the Lithiums is that they need to be protected against over discharge. I use them quite often but have to be careful. SC had a project recently on a protection circuit but it was a bit expensive. Paul. "It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all" |
||||
| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3805 |
Sorry to hijack, but please say more about over discharge of them. What should one not do / why / how to prevent etc. John |
||||
| palcal Guru Joined: 12/10/2011 Location: AustraliaPosts: 1873 |
In short they can't take an overcharge or be discharged beyond about 2.7v per cell. Discharging beyond this will ruin the cell. Most devices that use them (drills etc.) have an inbuilt protection circuit to open circuit when the voltage falls to this critical level. Just Google "charging lithium batteries" and you will find a wealth of information. Paul. "It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all" |
||||
| palcal Guru Joined: 12/10/2011 Location: AustraliaPosts: 1873 |
The article for the protection device was in Silicon Chip mag. here in Oz. The PCB was only 30x18mm. so it would fit in most projects but one supplier was offering a kit for A$29.95 which kills it for me. Paul. "It is better to be ignorant and ask a stupid question than to be plain Stupid and not ask at all" |
||||
| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3805 |
Thanks - that's bad news as I'm sure I've mistreated them without knowing :( John |
||||
 Print this page |
