6v power supply from 12v gel batteries question

[chrisp9au]

Just wondering what the most efficient method would be for supplying 6v to an EQ5 mount from 12v gel batteries might be? I can see "DC-DC 12V to 6V 3A 15W Car power adapter Converter Regulator Step down Supply" on ebay from China and Hong Kong, for example: http://tinyurl.com/bn872qz
Cheap, but I wonder how efficient they would be, would they have heatsinks?
is there a better way? :question:

Chris

[tlgerdes]

You first need to know your load (how many Amps) the system is going to draw.

You can get a kit from Jaycar for about $17 http://www.jaycar.com.au/productView.asp?ID=KC5446&form=CAT2&SUBCATID=965#11

Just add a case and a heat sink

You can change the regulator and diodes for about another $15 and bump it up to 3A.

[Steffen]

I think the Chinese converter from eBay would be the better choice. I seems as if it works like a switch-mode power supply (chopper-transformer-rectifier-regulator), whereas the JayCar kit will simply turn the same amount of energy into heat as your mount uses to operate (i.e. it functions as a variable equal resistance serial resistor). Hence, the loss with the Chinese converter will be much less and mostly limited to eddy and hysteresis losses in the transformer.

EDIT – The Chinese converter likely has an efficiency around the 85% mark and won't need a heat sink (less than 3W heat). The JayCar DC regulator can at best reach 50% efficiency and will probably need a heat sink at almost 10W heat dissipation.

Cheers
Steffen.

[chrisp9au]

Thanks Steffen, Trevor, and Rally (PM), for your suggestions.

The consensus seems to be for a switching solution, and I have some leads on suppliers here in OZ rather than waiting many weeks for a delivery from China!

Thanks again! :thumbsup:

Chris

[SteveInNZ]

If you don't already have the batteries, a simpler solution would be to buy two 6V batteries and wire them in series. Take the 6V from the center-point and 12V from the ends. Charge them in series with a 12V charger.

[chrisp9au]

Thanks SteveInNZ but I already have the 12v batteries, hence the need to find a way of getting a 6v supply. I have now ordered the switching solution.

Thanks again :thumbsup:

Chris