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The block diagram below is for a simple use of a solar array in conjunction with a battery, in a battery tied bus format. The diagram is simple and straightforward excepting the capacitor configuration.

One possible use of this configuration (usually) is to create a specific value of non standard capacitance using standard capacitors. This is clearly not the case as they are all equal and the equivalent capacitance is simply 100uF.

The configuration looks like it is acting as a filter in case of any sudden spikes in voltage, is this why it exists?

Could this configuration exist as some sort of redundancy?

schematic

simulate this circuit – Schematic created using CircuitLab

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  • \$\begingroup\$ Where did that circuit come from? The only way it makes sense is if 100uF capacitors aren't available (or too expensive) in the required voltage. And even then it won't balance the charge across them very well. \$\endgroup\$ – Brian Drummond Jun 4 '15 at 17:44
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Sometimes you see electrolytics in series to increase the overall voltage rating: -

enter image description here

Here you see five 50V rated caps in series. Note that bleed resistors are needed to equalize the voltage sharing evenly.

Having two series strings of capacitors is just a means of doubling the value.

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As you say equivalent capacitance is \$100\mu F\$, but what about maximum voltage? In an ideal world each capacitor would see only half of the total applied voltage, so you can use 200VDC caps up to 400VDC, for example.

(un)luckily enough we do not live in an ideal world: the central node will not stay nice and quiet at Vdd/2 but it will float around, and sooner or later your caps are liable to see an high voltage, high as in higher than Vdd/2. To overcome this problem some high value resistors are usually added in parallel to the caps: they provide a sort of DC bias and guarantee the middle node not to float around too much. You can even connect the two central nodes together and use only two resistors. A good starting value might be \$1M\Omega\$, but that depends on your maximum applied voltage.

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