Blowing up capacitors

[Mark Lloyd]

[snip]

I thought the usual maximum was 5.1V.

[Jim Jackson]

I think you misunderstand. The voltage quoted is the maximum voltage that can be applied. SuperCaps often have quite a low Max. voltage.

[invalid unparseable]

You don't have to put "three" 12V lead acids in series to see the adverse effect. A 12V lead acid battery is in itself 6 lead acid cells in series. That's why when you over-discharge a 12V lead acid battery, you risk killing the weakest cell by being reversely charged from the electric current driven the remaining good cells in the circuit, and then the second weakest cell will be the next to go.

I have bought some gel-ball toy guns from Amazon recently. Most of them use 7.4V lithium-ion battery pack. Each 7.4V is two 3.7V connected in series. I notice that the charger is designed to charge the internal

3.7V separately. The charging plug is 4-prong. That will eliminate the risk of overcharging each 3.7V and thus weakening it.

[The Natural Philosopher]

Bollocks. Think lightning. Air is not a chemical insulator

[Commander Kinsey]

I've never seen one.

[Commander Kinsey]

I've never seen one.

[Commander Kinsey]

I've never seen one.

[Max Demian]

Why 5.1 and not 5?

[The Natural Philosopher]

E24 series standard logarithimic progession

1.0 1.1 1.2 1.3 1.5 1.6 1.8 2.0 2.2 2.4 2.7 3.0 3.3 3.6 3.9 4.3 4.7 5.1 5.6 6.2 6.8 7.5 8.2 9.1

[Mark Lloyd]

Could it be because a 5V power supply may not be EXACTLY 5V?

[Commander Kinsey]

It is assumed when one cell of a battery goes, the whole battery was almost ready to throw out anyway. But if one cell of a poor battery dies, it can take out an entire good battery.

What I did with my electric drill, which used to be NiCad, was I put in Li Ion cells instead. The charger I removed the circuitry from and just use it as a connector to the battery and use a bench power supply, set at 4.2V per cell and a sensible max current. Inside the battery pack, I connected a cheap (a few dollars) equaliser, which boosts the weakest cell from the strongest at all times, charging, discharging, or idling. I have the same on my UPS battery system with lead acids. They could put one inside a lead acid for each of the 6 cells.

[Commander Kinsey]

What?

[Commander Kinsey]

Isn't it more to do with what nature wants and not us? We didn't want NiCad batteries to be 1.2V. 1.5V would have worked better to replace duracells.

[invalid unparseable]

I have not seen a 12V lead acid battery that provides easy access to the

6 internal cells.

The 2-cell, 4-connector setup is the ultimate solution to prevent charging the 2 internal cells in series. The 7.4V battery charger has two sets of 3.7V charging circuits to connect to the two 3.7V cells individually through the 4-prong plug. When the battery is unplugged from the charger and plugged back into the toy, the toy's 4-prong receptacle visually has a short wire shorting out the #2 and #3 to connect the two internals cells in series, and use #1 and #4 to connect the combined 7.4V to the toy. It will be quite tedious to apply this principle to a 6-cell, 12V battery.

[Bob Eager]

Back in the 1960s, I thinbk it was relatively common. The interconnects were on top of the case, not inside, and one could tap at whatever multiple of ~2v one desired.

[jon]

True

[Fredxx]

A man of your claimed calibre with an IQ > 100 and claimed to have completed the university degree of Micro-electronics course should be aware of the E24 series.

All the claims you make about yourself simply don't add up.

[Fredxx]

No, a standard power source is 5V, so a voltage rating with modest tolerance above that would be 5.1V This has nothing to do with the E24 series that is based on preferred values such as capacitance and resistance.

Yours is a typical stock Art Student reply that is plain wrong.

[Fredxx]

By way of example 5.1V rating is quite rare:

Designers would use a voltage rating in excess of the expected power supply. Even a 5V power rail will have a tolerance, typically a few %.

Most of the supercaps intended for +5V operation would have a rating of >5.4V as per the ratings in the above link. 5.1V rating on a 5V rail would be pushing it and would be designed around the supercap, not the other way round!

[Fredxx]

I was going to say the same thing. Some batteries still retain the external connections such as fork-lift batteries.