2016-01-26

6pcs Supercapacitor Bank, some simple calculations

BRIEFLY...

Here I am going to talk about these supercap banks....
















They are made mainly for 12V applications, and got cheaper, because the 500F elements probably have the best price/capacity ratio.

However I am going to show you WHY a 5 pcs bank has more energy than a 6pcs.....!



IN DETAIL

500F 2.7V


With 6 caps:

2.7V * 6 = 16.2V - max voltage, you have more than 4 volts tolerance which is good!

however if you charge the supercaps up to 12V only, and they are well balanced, you have:

12V / 6 = 2V - per capacitor

2V * 2V * 500F / 2 = 1000  - Joules of energy per capacitor, which makes:
1000 * 6 = 6000 - Joules for a 6pcs supercap bank, charged up to 12V



With 5 caps:

2.7V * 5 = 13.5V - max voltage, which is not so good, you have to be careful, only 1.5V tolerance

if you charge the 5 pcs bank to 12V you have:

12V / 5 = 2.4V - per capacitor

2.4V * 2.4V *500F / 2 = 1440 - Joules per supercap, and

1440 * 5 = 7200 - Joules for a 5pcs supercap bank! (20% more)


CONCLUSION

A bank with 5 supercapacitors , charged to 12V, has more energy than 6pcs, because of the bigger voltage per capacitor, leading to much more energy per capacitor, which is so much more, that even that they are only 5, they have more energy in total!




2016-01-08

Upgrade DECT phone battery

This is my first blog for 2016! Happy new year to all!

Problem

I don't like putting my dect phone (General Electric CE21886GE9-A) on its stand all the time, because I am not sure that the battery will survive and I want to situate it anywhere around the house, not necessarily near a power socket.
Anyway - the built-in battery NiMH 300mah is too small for that. If I don't use the phone, it goes down for a week, and if I use it for 4-5 days.


Solution

I won't explain much about my solution, because the picture speaks for itself.



1. is the standard set-up with 300mah NiMH. I find it more and more difficult to find this type of battery in the shops.




2. I tried to find out a Li-ION battery on ebay that is almost the same size, with bigger capacity. I managed to find only 600mah from here:
http://www.ebay.co.uk/itm/251883140017?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
The battery is 7mm x 30mm x 30mm. A bigger battery can fit there - like 10mm or so, but I could not find one. You just have to cut the wires from the previous battery, so that you can use the plug. Use just tape, or better solder them (red-red, black-black) together and you're done.
The phone got lighter. It lasts for 2 weeks now. The battery can stand more charging cycles because it is Li-ION and because it is one single element, not 3 in series.
The battery voltage matches because 3x1.2NiMH elements = 3.6V , while the LiIon battery is around 3.7V.


3. If you really want big battery you can mount this 3 AA battery pack on the back of your dect, then drill a tiny hole on the cover (as you see on 2.) so that the wires can reach the small socket inside.
The disadvantages are:
- the phone gets really heavy and not comfortable for talking
- it is better if you remove the batteries and charge them separately, because it takes a lot of time to be charged on the stand, and they do not charge equally (like in the original one actually)

I did it and it worked with 3 old 2000mah NiMH batteries from my camera, and it stays on for a month or more.


Cheers