Stop Headlights Flashing 101
This gets asked a lot, so here's a basic guide..
1. Get a better battery. It doesn't need to be a $$$ Optima or Odyssey, just a nice Exide with 500+CCA & 120+ minutes reserve...
2. Upgrade the earths. Buy 4 gauge cable. Replace the battery -ve to chassis earth and engine block to chassis earth straps with the 4g. While your at it, run another 4g from the battery -ve to the firewall.
3. Upgrade the earth cables on your amps to 4g. The +ve should also be 4g.
4. Get an auto-electrician to check out the alternator and see how healthy it. You can also ask them to upgrade the alternator to battery charge wire to something bigger while you're at it.
5. Clean your battery terminals & clamps with steel wool or sand paper for a good clean connection.
In 99% of cases these simple steps will solve any problems you have with lights dimming, etc. Caps are worthless, spend the money on cable or battery upgrades.