These capacitors use carbon aerogel to attain immense electrode surface area, can attain huge values, up to thousands of farads. EDLCs can be used as replacements for batteries in applications where a high discharge current is required, e.g. in electric vehicles. They can also be recharged hundreds of thousands of times, unlike conventional batteries which last for only a few hundred or thousand recharge cycles. However, capacitor voltage drops faster than battery voltage during discharge, so a DC to DC converter may be used to maintain voltage and to make more of the energy stored in the capacitor usable.