Capacitor specifications, ripple current and life

Question

What does the "Ripple current" and the "Life (in Hours)" in electrolytic capacitors specifications mean?
My intuition says it's the highest current it can handle and it can operate for that hours (when it works under that ripple current) before it fails, is that right?

In this picture it's not mentioned the "life" specs but I've seen it in many other (mainly electrolytic) capacitors. It's usually something around 2000 hours.

Let me know if I get this right. This is a theoretical question.
Let's say we have the following specs (after calculations) for a DC to DC converter.

\$C = 350 μF\$
\$ ESR_{min}=10 mΩ\$
\$V_{OUTripple} = 50 mV\$
\$I_{Lripple} = 3,5 A_{peak-to-peak}\$

What would happen if the capacitors can handle lower ripple current (even in parallel)?
For example, if I put 2 capacitors like the specs above does that mean my capacitors can handle up to 1700 mA?
Would it be destructive for the capacitors if they can't handle the specified ripple current?

Could I ignore the ESR if I'm okay with higher voltage ripple (\$V_{OUTripple} = ESR * I_{Lripple}\$)?

Answer 1

Electrolytic capacitor lifetime is given in hours at the maximum operating temperature, and that's what it depends on: its operating temperature.
For every 10°C reduction in operating temperature, the capacitor lifetime is doubled, so for a 105°C cap rated for 2,000 hours that means that it could last about 32 times longer, or about 64,000 hours at 55°C.

The ripple current rating tells you the manufacturer's recommended maximum so that it doesn't cause a detrimental rise of the capacitor's temperature. You could ignore it and that will shorten the capacitor's lifetime.

You should either use a larger capacitor or multiple capacitors in parallel so that their combined rated ripple current is higher, and their combined ESR is lower than the ones calculated for your circuit. Using higher (than calculated) capacitor values can only benefit both your circuit and your capacitors (and their lifetime), while using lower values will shorten the lifetime of the capacitors and the circuit along with them, and could also impair the circuit's functioning.

Answer 2

The main failure mechanism of an electrolytic capacitor is time at temperature drying out the electrolyte. The lifetime is usually quoted to an increase in ESR or a reduction in capacitance, often in the 10% to 20% range, rather than total failure.

850 mA rms ripple current in your specified capacitor will cause a heating of \$I^2R\$, so 0.85²0.08 = about 60 mW. This doesn't sound a lot, but it's a small case, so there will be a temperature rise above ambient. At lower temperatures you would hope for a longer lifetime. Two of those in parallel would be able to handle 0.85 Arms each, or 1.7 Arms total. You would need five of those in parallel to handle 3.5 Arms, it depends how your ILripple is specified, is it rms, peak, or pk-pk?