Normally, since in the USA we are forced to run with the headlight (and tail and instrument lights, by default) ON all the time, the 500/550 alternator is strapped to the max in the normal bike's wiring/loads arrangement. With the OEM headlight (40/45 watts) and taillight (8 watts) ON, there is only about 11 watts (9.6 watts, 0.8 amp) left to charge the battery. If the bike is stopped at a stoplight, it is draining the battery (with points ignition) about 2.4 amps with the lights ON, until about 4000 RPM when it breaks even and begins to charge again. This is with the OEM coils aboard, which are 0nly charging 1 at a time with points ignition.
When the Dyna triggers are used, this changes the picture quite a bit. The Dyna charges BOTH coils (instead of just one at a time) all the time except during the very short period when the trigger magnet passes the pickup. This adds one whole coil's current to the constant load picture. The Honda coils are 4.3 ohms (2.8 amps each at 12.0 volts), so the bike is forced to try to charge more current than the alternator can even make when the lights are ON with the Dyna. Typically this means the bike's battery will drop lower and lower until the voltage falls far enough for the overall current load to stay at maximum charge rate, which I've found is somewhere around 11.4 volts in a fully-functional 500/550 system. This isn't healthy for the battery, as it encourages sulphation to start on the lead plates when the chemistry falls short of the needed ions.
I've seen this lead to some serious troubles in the 500/550, including wiring fires when someone tries to "fix" this without removing the Dyna. Adding things like a lithium battery and its required "smart" charging regulator is not practical, as their charging method requires that before the battery will accept a charge, it must be "tickled" until the chemistry will accept a charge: this isn't how these bikes' charging systems work, nor can they be made to work that way. This requires a "smart" voltage regulator and enough run & charge time that the bike would end up being useful only for (as example) all-out Interstate touring every day, with a short startup period with no charge at all, followed by a long charge time: rather impractical in real life with traffic lights, stop signs, and uneven engine speeds. This system was designed to run with the lights OFF in daylight (1971-72 era), and ON occasionally for night riding. It was the US DOT who changed the lighting rules AFTER these bikes were designed (1973) that created the problem.
So, I'm sorry to say that in the USA with lights ON all the time, the only way to make a Dyna S [almost] work is with an LED headlight and taillight bulb (which isn't bright enough in a red lens) and freeway touring to work and back, and Dyna's 5-ohm coils instead of normal ones. The other way is to (re)use points (and [many also use] my Transistor Ignition, which was created precisely to solve this problem and stop the frequent points maintenance needs, in 1973) and at least OEM coils (4.3 ohms), or the Dyna 5-ohm coils. The latter has improved many 500/550 bikes by just adding them to the bike with points, too.
I don't intend to use this as a 'forum' to advertise my Ignition, but rather as an explanation of why it was created in the first place, and specifically for (my) CB500 and CB750 in 1973. It was to reduce the points maintenance that these SOHC4 bikes had greatly increased because they were so happy to run all day - which was novel in the 1970s.
