For example if i need 18V for a project, what is the difference if i use 2 9V batteries and 1 9V battery boosting it to 18V?
Thanks in advance.
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\$\begingroup\$ Do you mean batteries A and B in parallel, and this combination in series with C? \$\endgroup\$– ChuCommented Oct 3, 2018 at 6:36
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\$\begingroup\$ You need to specify your current requirements, but consider that no boost circuit is 100% efficient \$\endgroup\$– R DrastCommented Oct 3, 2018 at 8:10
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1.) Converter losses, but not too much. Good converters have 90-95% efficiency 2.) What is your load? If you have 9V 1A batteries as example, P= U*I = 9W. At 18V you will be able to draw 500mA from 1 battery in this case. 2 batteries in series, which would give you 18V directly without boost, you can draw 500mA. Of course, 2 batteries also have a higher capacity, so you could power your project for longer before recharging batteries.
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\$\begingroup\$ 2 batteries in series does not double the current that can be drawn from them. If they are in series, the maximum current that can be drawn is the maximum current that any one of them by itself can output. Putting batteries in parallel multiplies the current that can be drawn by the number of batteries placed in parallel. Your answer isn't entirely clear if you address the problem of each battery's maximum current draw vs the current required to be drawn from the output of the converter. \$\endgroup\$– mithCommented Oct 3, 2018 at 12:40
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\$\begingroup\$ You are correct, my apologies. I meant that the power doubles, and you can keep same load, but with 1 battery and boost, the maximum current drops, since power must always stay constant \$\endgroup\$ Commented Oct 3, 2018 at 13:15