12V DC and 24V DC Power Management

[tjtjtj]

I am designing a very small prototype device it needs to power external devices which require various power voltages and amperage draws. 12 12 V and about 7 amp continuous with a starting device peak of about 10 to 12 amps.
the inputs are from three nominal 12V batteries. The actual fresh voltage is about 14.4 these can be either nicads, or other chemestries.
The power supply board must be very small. The case contains a lot of wiring and is limited to about 3" by 4" by 2"

I need to seperate the output of the no1 battery to the system itself since the outboard devices can adversly affect the related video of the device when their motors are on.

At times I need to run the whole system on one battery, including outboard devices on the same connectors as normally run on 2nd and 3rd batteries below.

I need to have the 2nd and 3rd batteries power 12V devices which will blow a circuit breaker about 28volts about 7 amp draw and higher spike at starts.

I need to power 12 volt devices either from the 2nd battery or the second and third batteries. together. and want in that case to have even draw between them.

I need to have one output variable down to about 4V for a specialized device running only on this lower voltage.

If you can help me it will be very much appreciated. any advice about where to obtain
the means to do this is also certainly appreciated.

TJTJTJ tjsteadicam@qwest.net

 

[jbartos]

Suggestions marked ///\\I am designing a very small prototype device it needs to power external devices which require various power voltages and amperage draws. 12 12 V
///Please, clarify this\\ and about 7 amp continuous with a starting device peak of about 10 to 12 amps.
the inputs are from three nominal 12V batteries. The actual fresh voltage is about 14.4 these can be either nicads, or other chemestries.
The power supply board must be very small. The case contains a lot of wiring and is limited to about 3" by 4" by 2"

I need to seperate the output of the no1 battery to the system itself since the outboard devices can adversly affect the related video of the device when their motors are on.
///It can be done via diodes or via a separate battery.\\At times I need to run the whole system on one battery, including outboard devices on the same connectors as normally run on 2nd and 3rd batteries below.

I need to have the 2nd and 3rd batteries power 12V devices which will blow a circuit breaker about 28volts about 7 amp draw and higher spike at starts.

I need to power 12 volt devices either from the 2nd battery or the second and third batteries. together. and want in that case to have even draw between them.
///More info is needed, namely, is this supposed to be controlled manually or done automatically?\\I need to have one output variable down to about 4V for a specialized device running only on this lower voltage.
///A battery tap at about 4VDC may be built.\\
///Switching logic analysis and diagrams might help.\\\