several members here have browning portalamps.
magnetic ballast with a vibrator.
no sand.
In that respect all DC ballasts are "the same":
The only difference is the operating frequency, the vibrator can not operate much above some 100Hz or so, while a semiconductor switch can operate at 10's of kHz. In both cases it uses some switch to convert the DC into some form of AC, which then passes through a transformer.
The concept the Browning uses is one of the worsts: The lamp current is really hugely dependent on the battery. But that is the cost to pay when being so limited by the available components - in 50's you really could not do better with reasonable size and budget.
The single transistor inverters (as topology; do not confuse with how they use to be rated) perform way better - the lamp power is way less dependent on the battery voltage. The output DC current component could be quite reasonably tackled by careful thermal design of the fixture.
Of course, the modern commercial vehicle converters are the best, but are way more complex (speaking about complexity, when you draw the complete schematic, include the inner circuits of the used IC's).
But either from these has anything common with the underdriving problems with the battery lanterns. There the problem come mainly from the desire to get as much possible battery runtime with a given light output at the minimum TCO (total cost of ownership). Because the batteries (assume the single use cells) are the most expensive part of the TCO, everything is designed around sufficing with as little power. At the power levels mostly used there, it is better to use longer higher power lamp and underdrive it, not lower power one and drive it at its rated power (with F8T5 you suffice with 2..3W and get the same light output as with F4T5 driven full power, so 4W; obviously the first will give you longer battery life). Of course, it has huge impact on the lamp life (10khour -> 100's hour), but that is an acceptable cost to pay when saving on the batteries.
With lamps intended for use with running motor vehicles (the bus, trains,...) the most expensive part are the lamps, so there the ballasts are made so, they really drive the lamps at rated power, use decent preheats or so, regardless if that costs some extra power, the lamp life is just the priority there.
So you may find a perfectly symmetrical ballast with no DC component within an emergency lantern, which kills the lamps one by one (because the F6T5 is driven there at about 2W or so).
Compare to a single transistor asymmetric 24V bus ballast driving a F20T12 at about 18W, with significant DC component, yet the lamp life there exceeds the normal mains rating even when they are much more frequently switched in the bus application (the filaments get external heating power all the time, even when it eats up some power from the arc, so lower the light output).
The browning was designed more around the "bus" lines, but the consequence is, the power input is around 20W at 14V (engine running), but lamp power just barely 8W at 12V input, going way lower when the battery discharges further. But at that time it was quite good success, to achieve at least this...
