[sdiy] Combined Battery Charger / Power Supply Kit?

[Ullrich Peter]

Hello Michael!

I would not use 4 rechargeable 9V blocks. I would use one battery block and generate the necessary +/- 15V via 
a DC/DC converter circuit. This way you only have to manage the charging for one battery, and if the battery goes down all
output voltages go down what is not garanteed with 4 batteries.

As battery the cheapest solution would be the use of battery packs for RC cars. You can buy them for cheap in Austria
at Schweighofer Modellbau in Corinthia. www.der-schweighofer.at
The battery page is here: 
http://www.der-schweighofer.at/wg/114/akkus_und_batterien

Of course also Conrad has them, normally more expensive...

If you use a 12V battery pack you could use DC/DC converters that works from 9 to 36V input voltage, good quality
DC/DC converters I can recommend are from Recom - you can buy them from www.rs-components.at .
Or you can build your own DC/DC-converter using small chips from Linear Technology, Maxim or others. You can get
a higher efficieny with non isolated designs. Isolated DC/DC converter are normally in the range of 82 to 85%, non isolated
converters can reach up to 93 or 95%. But be careful with these 95% - they are for onw exact input voltage, so with
batteries going down you need to have a look if these DC/DC converters can work with the battery range... the good
efficiency converters are Point Of Load (POL) converters that work from a stabilized input voltage and convert into
the output voltage at the "point of load" with maximum efficiency.

For charging you need to search on Google for a solution that fits your needs.

Ciao
Peter

http://come.to/synpro

________________________________________
Von: synth-diy-bounces at dropmix.xs4all.nl [synth-diy-bounces at dropmix.xs4all.nl] im Auftrag von Michael Zacherl. [sdiy-mz01 at blauwurf.info]
Gesendet: Samstag, 01. Mai 2010 02:44
An: synth-diy DIY
Betreff: [sdiy] Combined Battery Charger / Power Supply Kit?

Hi All,

   I'm conceiving a portable synth +  fx-box which I'd like to also have battery powered.

My idea is to have 4 rechargeable 9V NiMH blocks to get +/- 15V from the charger/supply unit.
I have no experience with such circuits and charging batteries hence I'm looking for a kit or pcb.

I want to have it this way since charging 9V batteries usually  means to have 2 to 4 chargers,
Even my big Ansmann Energy8 provides only 2 slots for 9V batteries.
And once it works it's much more convenient.

Basically it should be like in notebooks (this synth will be a laptop too ;-) :
Wall-wart connected, the device is being supplied and the batteries are charging.
Wall-wart disconnected runs the box from the 9V blocks.
The circuit also should work as a PSU when no batteries are inserted and for backup it should
be able to deal with Alkaline cells (w/ no charging of course) as well.
An optional switch to prevent charging and an accurate status LED would be nice.

I'm also looking at NiMH and Li-Ion battery packs but I'm not sure if I want to go for something proprietary.
(and adding Alkalines wouldn't be possible as well).

Since I'm located in Austria an EU based vendor would be nice.
(but I prefer quality over shipping charges and custom fees ;-)

This is an rough idea and I'm still collecting thoughts, nothing's carved in stone.

Any hints, pointers?

Thanks a lot, Michael.


--
noise chasers: http://blauwurf.at

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