Battery solutions - tips M5 - help

You're asking valid questions, Paulo.

The general strategy is to make a list of all the devices and the voltage they need and the amount of current they draw.

e.g.
Black Magic: Volts = x, Milliamps = y
Paralinx Transmitter: Volts = p, Milliamps = q
and so on.

If you can create such a list either I or someone else can walk you through the calculations.

The 4S battery will delivery from 16.8 volts (fully charged) down to about 14.4 volts. It can supply a *lot* of current, but the more current it supplies, the shorter the time it will last.

Can you post the table with the information filled in, please?

Andy

 

The maths involved is based on Ohm's law: Voltage = Amps x Resistance.
And the additional math that Watts = Volts x Amps.

However, the first step is to understand the pattern of requirements. You have a battery that that operations from 16.8 to 14.4 volts (depending on its state of charge).

Given the devices you list, they divide into one that needs 12 volts, and three need 5 volts.

So that tells me that you need two different DC to DC converters. One at 12 volts and 2,5 amps.
And one at 5 volts at 6 amps.

In both cases you want to add some spare capacity, so I would tend to go for:
a. One DC/DC converter that produces 12 volts at 4 amps.
b. One DC/DC converter operating at, say, 5 volts at 8 or 10 amps.

Bearing in mind that the numbers for the amps you show are probably maxima rather than the actual steady state, you can afford to choose DC/DC converter that are a little bit closer to the rated amps you show above.

Now you know that, you can start to search for DC/DC converters, however, you'll quickly discover that many DC/DC converters are sold based on the maximum output Wattage they can provide.

So now you look at your Watts = Volts x Amps formula. We know the voltage -- it's either 5v or 12v.
So for the three 5v devices, you need 6 Amps. So 5 x 6 is 30 Watts.
For the 12 volt device you need 2.5 Amps. So 12 x 2.5 is also 30 Watts. (Just a coincidence...don't attach any significance to it).

So then you do a Google search for: DC/DC converter 5v output 50 watts -- and that's where you'll need to find local suppliers. Note the 50 watts -- that's just to give some spare capacity. Then do the same kind of search but for 12v output 50 watts.

Hope that helps
Andy.

 

Paulo:
You say "I'll need two more with different voltage..." but I'm not quite sure why you say that.

The M5 Lipo voltage produces from 16.8 v to 14.4v (that's the typical useful range). If you use two DC to DC converters, you can take that output voltage and produce 5v with one converter, and produce 12v with a second converter -- both converters receiving the output from the M5 LiPo. The converters will be different models, of course as one has to drop the voltage to 5v and the other to 12v.

So you do not need two more batteries -- although the additional load will shorten the discharge time for the M5 battery and therefore you might choose to use a higher capacity M5 battery. How much larger capacity -- that's purely a function of how often you want to change the battery. If you double the capacity of the battery, you will (as an approximation) only need to change it half as often.

Andy.

 

Nice find (as usual), Group Captain Maller.


Andy