Large supercapacitors need a current limiting device in series when they are initially charged, because they store a large amount of energy and have very little internal resistance. Because of these qualities in addition to initial capacitor voltage typically starting from zero volts, the capacitor may act like a short when wiring it in parallel to a battery or power source.

**Click here**for examples of larger capacitors.

It is common to see violent sparks and melting of wires and posts along with damage to power supplies and batteries if there is nothing in line to slow down the initial charge surge current. Although a properly selected current limiting resistor to go in series with the capacitor would work for the initial charge, one may also simply use an incandescent light bulb with an equivalent voltage in a series connection to the power source. This series bulb can be in line on either the positive or negative lead since it is a series connection. **289-1216-ND** is an example bulb for use with 12v sources.

Depending how large your capacitor is and bulb being used, It may take an hour or so to charge the capacitor fully since the current flowing through the capacitor is only that of the bulb current, so make sure you have it wired in a comfortable fashion. You may choose to wire a few bulbs in parallel to increase the capacitor charge current and lower the charging time. The added benefit of charging a capacitor with a light bulb other than simplicity is an indication showing a completed charge by when the light becomes dim or quits illuminating. Once charged, you can unhook the bulb, verify the capacitor voltage is equal or near rated voltage with a multi-meter and wire the capacitor directly in parallel to the power source.

One may choose to use a series **resistor** instead for faster charging of the capacitor. You will need to select the proper resistance value in order for the capacitor to not pull more current than the battery or power supply can handle. For an example, if a 1-Ohm resistor is used, the charge current will be the same value as the system voltage, therefore a 1-Ohm resistor being used on a 12V system will charge the capacitor at 12A. The current will slightly decrease as the capacitor becomes fully charged. Power rating of the resistor will have to be calculated unlike the incandescent bulb method using the P=IV formula, sometimes remembered as "poison ivy’'. If we use above example, 12A x 12V = 144W.

## Permanent Battery & Supercapacitor Application

Since a supercap has such little resistance, leaving one in parallel to a battery will drain the battery if not intermittently or constantly charged from the alternator or battery charger. For this reason, one may wire a disconnect switch or a N.O. (normally open) relay in series to the supercap in order to prevent battery drain. In automotive applications, it is common to use a N.O. relay where the coil is powered from a +12v (switched) accessory wire from the fuse box or behind the radio. The relay current rating will need to be greater than the max current draw from the battery.

For these applications, it is common to have a permanently fixed resistor in place (R1) and to use a **diode** (D1) in series to the load from the capacitor when the load is pulling current from both the capacitor and the battery (or other power source). The diode being a “one-way-gate” provides full output current from the capacitor but prevents bypassing of the resistor. Every time the circuit is switched on, the capacitor will safely charge with limited current through the resistor, but is also able to supply full capacitor current to the load. The diode current rating will need to be greater than the max current draw from the capacitor.

## Summary

338-DSM254Q018W075PB-ND

338-DSM504Q018W075PB-ND

338-DSM165Q018W075PB-ND

338-DSM255Q018W075PB-ND

338-DSM585Q018W075PB-ND

338-DSM126Q018W075PB-ND

399-A958AL112M800S-ND

2610-SM0062-017-NB-1-ND

338-DSM186Q018W075PB-ND

2610-SM0058-016-P-1-ND

2610-SM0058-015-NB-1-ND

2610-SM0062-018-P-1-ND

2085-PBLH-12R0/87ST-ND

2085-PBLH-12R0/100ST-ND

2085-PBLH-12R0/112ST-ND

589-BMOD0058E016C02-ND

283-XVM-16R2656-R-ND

2085-SCAPPBL-25/16.2-ND

283-XTM-18R0626-R-ND

2610-SM0500-016-PT-ND

2610-SM0500-016-ATH-ND

283-XLR-16R2507-R-ND

283-XLR-16R2507B-R-ND

2085-PBLH-18R0/500SD-ND

283-XLR-18R0507B-R-ND

2610-SM0006-160-P-ND

2610-SM0006-150-NB-ND

2610-SM0006-180-P-ND

2610-SM0006-170-NB-ND

589-BMOD0006E160C02-ND

2610-SM0165-048-ATH-ND

2610-SM0165-054-ATH-ND

2085-PBLH-54R0/166SD-ND

2610-SM0125-064-ATH-ND

283-4786-ND

2969-SKELMOD51V-ND

283-XVM-259R2425-R-ND

283-XLM-62R1137B-R-ND

283-XLM-62R1137A-T-ND

283-XLM-62R1137B-T-ND

283-XVM-259R2635-R-ND

283-XVM-315R9345-R-ND

2969-SKELMOD102V-ND

283-XVM-315R9515-R-ND

B48621A7205Q018-ND

B48621A9115Q024-ND

495-2067-ND

495-2068-ND

495-2069-ND

495-2070-ND

495-2072-ND

495-2073-ND

399-11550-ND

283-4611-ND

2610-SM0058-015-NB-ND

2610-SM0058-016-P-ND

2610-SM0062-018-P-ND

2610-SM0062-017-NB-ND

2969-SKELSTART24V-ND

2969-SKELMOD170V-ND

2969-SKELSTART12V-ND

399-A957AL132M800S-ND

DSM254Q018W075PB

DSM504Q018W075PB

DSM165Q018W075PB

DSM255Q018W075PB

DSM585Q018W075PB

DSM126Q018W075PB

A958AL112M800S

SM0062-017-NB-1

DSM186Q018W075PB

SM0058-016-P-1

SM0058-015-NB-1

SM0062-018-P-1

PBLH-12R0/87ST

PBLH-12R0/100ST

PBLH-12R0/112ST

BMOD0058 E016 C02

XVM-16R2656-R

SCAP,PBL-25/16.2

XTM-18R0626-R

SM0500-016-PT

SM0500-016-ATH

XLR-16R2507-R

XLR-16R2507B-R

PBLH-18R0/500SD

XLR-18R0507B-R

SM0006-160-P

SM0006-150-NB

SM0006-180-P

SM0006-170-NB

BMOD0006 E160 C02

SM0165-048-ATH

SM0165-054-ATH

PBLH-54R0/166SD

SM0125-064-ATH

XLM-62R1137A-R

SKELMOD 51V

XVM-259R2425-R

XLM-62R1137B-R

XLM-62R1137A-T

XLM-62R1137B-T

XVM-259R2635-R

XVM-315R9345-R

SKELMOD 102V

XVM-315R9515-R

B48621A7205Q018

B48621A9115Q024

B48621A4205Q006

B48621A4455Q006

B48621A4605Q006

B48611A5903Q012

B48621A7334Q018

B48621A7105Q018

S01PM5805K016A

XLM-62R1137-R

SM0058-015-NB

SM0058-016-P

SM0062-018-P

SM0062-017-NB

SKELSTART 24V

SKELMOD 170V

SKELSTART 12V

A957AL132M800S