Battery charger power supply


Battery charger using 24VDC power supply

I have some 24VDC power supplies. Many industrial fields use 24VDC as well as process and power plant. Industrial PLC (Programmable Logic Controller) usually apply to the DC voltage only.

Fig.1 Charger trial
The photo shows a trial battery charger. The power supply is available for 2A and can regulate in the range of 22 to 27V. The maker is MITSUMI. I bought a charger kit that uses a power control IC, type 723 of JRC. Specifications of the kit are,

In order to increase current, I used another power transistor 2SC2580 by Darlington circuit. The collector dissipation power is 90W. The kit are on the board. I will mount some cement resistors of 10W in series to drop voltage of the power supply. The board and the power supply are on a chassis of 1mm thick steel plate.

The result was not good, because power dissipation was too big that the chassis was heated at considerable temperature. The dissipation was,

( 24 - 14) x 2 = 20 W

The power dissipation was the same of a soldering iron. I don't accept that the hot status continues at the high temperature almost half a day. I designed to mount 6 cement resistors and shorten them to step up voltage using clips at first. As bared clips are carful to treatment, I would adopt mechanical SW. But these SW are expensive because SW is soft type of FET now. I gave up the idea. I want a voltage variable power supply, allowable for 2A.

Alkaline battery capacity

Clock swing

Although swing of clock on cupboard has stopped for a few months, the clock indicates time. I replaced the dry battery for a stocked one. How much does LR6B have capacity? A site tells that it has 1000mAH.[1] I measured the open voltage of the used one. It was 1.151V. The movement of the clock may at 1.0V. How much does the swing dissipate current? I do not know when I replaced the battery. If it took three years, the total working hour would be 3x8760 h. The dissipate current,

Current = 1000/(3x8760) = 38μA

But the validity date of the used battery is 08-2014. If it was productioned before five years of the validity date, the used time would be two years. The current is 57μA. The used battery was made by SANYO in Indonesia. Why do Japanese battery makers make in Indonesia? Fujitsu shows how to make alkaline battery. Japanese press wrote that SANYO was excellent to make battery. Looking at the drawing of the production, It is important to make can, separator, conductive coat and gel. I think that Sanyo bought the can and the materials. NEC and a few makers withdrew production of battery for hybrid cars. I think the decision is right, because the battery material makers will sell their materials abroad. Why did Panasonic buy Sanyo, though Panasonic sold her stock of JVC?
14:36 Feb19 GMT+9

[1] ¥100 shop alkaline battery seino hyoka jikken
[2] Fujitsu kan-denchi no dekirumade

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