12 volt automotive sealed beam lamps in series

Basically, you'd put a resistor across the higher-resistance lamp. If you know the voltage across each lamp, and the current through them, you know their resistances -- so this should be easy to compute.

Of course, since the filament's resistance varies with the current through it, "deflecting" some of that current will lower its resistance. You're probably going to have to experiment a bit.

Is the *battery* on said vehicle a *single* "24V" battery? I.e., if, instead, it is two 12V batteries in series (which is what the 24V battery would look like internally), then why not run another conductor to each "lamp assembly" (3 wires instead of 2) and run each filament off of its intended 12V?

One should never tap off the bottom battery in a two battery 24V system, it will result in improper charging of the batteries.

Two solutions are either do what the OP does (two in series) or use a voltage regulator capable of handling the current (not an efficient solution). You can get 24 volt headlights on eBay if you want them, as well... There are other solutions too, such as getting housings that handle replaceable bulbs, which may be available cheaper as a 24 volt unit. (Not sure on costs there).

Just go series, don't worry about minor light output differences, but realize that if one goes out, both will go dark! Always carry two spares with you.

How about a 24 V to 12 V converter to power the headlamps? National Semiconductor makes the 'Simple Switcher' series of regulators.

That depends on the actual charger configuration -- hence my asking if it was a 24V monoblock or a pair of 12V monoblocks.

Given that this is the *military*, I am assuming that they have deep enough pockets to create their own standards (e.g., 400Hz power). As such, if they opted for two 12V monoblocks in the vehicle, I would assume they would have also designed a charging system that *treated* them as two 12V monoblocks and not a "24V battery" -- since the added cost of charging them as two monoblocks would easily be outweighed by the increased "battery" life that obtains from that since imbalances between cells are a (the?) primary cause of battery failure (presumably the military wouldn't want to have to lug around spare batteries if they could make the ones they had last longer -- esp. in a war zone). Cells will *try* to equalize with overcharging in short strings but, as the string gets longer, battery life goes to hell (since the "good" cells get overstressed trying to "coax" the bad ones back in line; and, as a cell gets bad, it gets bad-er!)

But, I've never peeked under the hood of a military vehicle so can't tell if:

- 1 monoblock or two

- three terminals to the battery or just two

- is the *entire* system running at 24V (or just parts that draw higher currents)

Nothing to do with the post Lenny - just a casual question about your nic ! :-)

I never knew who or what Klem Kedidlehopper was, until I was in a movie memorabilia shop in Vegas last week. There was a suit on display that claimed to have been worn by this guy on his TV show (I'm assuming he is a left-pondian comedian. Me being right-pondian, he's not one that I know). But anyway, here's the thing. They had his name spelled with a "C" as in Clem Kedidelhopper. Is that wrong of them, or is your spelling with a "K" some comedic twist that I'm missing ?

Arfa

The military battery system consists of two 12volt batteries in series..Every load in the vehicle is connected between 24 volts and ground. There is no 12 volt load connected "halfway" between batteries. Electrically the charging system treats the two separate batteries as though they were one 24 volt battery. I like the idea of connecting each lamp to each battery, ( a three wire circuit), however in the event that a cell in either battery goes dead, the imbalance in voltage across the two batteries would be far greater than that created by a weak filament.

Klem Kedidelhopper was a comediene of 1950's vintage I think.that he was the brain child of Red Skelton. When my son persuaded me to open an email account many years ago after I repeatedly told him that I would never have any use for one I had to pick a screen name. Never really thinking that this would ever even go anywhere and not fully taking this whole computer thing seriously at the time anyway, I chose the name of one of my favorite TV characters. Well these days I use email a lot, Klem is still on the job, I still think computers are a royal pain in the ass, and surprisingly most people have no idea as to who he was. Lenny .

He was a 'County Bumpkin' character perfomed by Red Skelton on his TV variety show. Along with 'The mean widdle Kid', a bum named 'Freddy the Freeloader' and other characters.

He was a 'County Bumpkin' character perfomed by Red Skelton on his TV variety show. Along with 'The mean widdle Kid', a bum named 'Freddy the Freeloader' and other characters.

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My favorite is/was Cauiflower McPug. Red performed all those characters on radio long before TV came along.

Not *the* Lenny Bruce?? ;-)

Gertrude and Heathcliff

With the exception of a few vehicles, all military vehicles use a standardized 24V alternator to charge two 12V batteries connected in series. The exceptions are some new HMMWVs with the 4L80E transmission which have a combination 24/12 volt alternator (which is really expensive, a couple of thousand dollars), needed because the transmission controller requires 12Volts, and some older military pickup trucks (based on commercial pickups) that used two 12V alternators to minimize the modifications needed to the electrical system to convert them to military voltage standards.

The military didn't create 400Hz power, IIRC, it is a standard for aircraft electronics. It is used to keep transformer weights down in an environment where weight is critical. The military uses 400 Hz for some ground equipment, but often this equipment is based on airborn electronics.

Not sure what you are saying when you use the term 'monoblocks', all military vehicles use 12V batteries in series. There is never (excluding the exceptions noted above) a connection to the lower battery except to the upper battery.

Generally speaking you try to keep the battery pairs as matched as possible, and occasionally you check the charge for each one. If one is not being charged properly, replace them.

Again, what's a monoblock? A battery? Then yes, all have two 12volt batteries. Yes, I have a number of military vehicles. And yes, I'm well famiiliar with the electrical configurations for these setups.

Standard batteries. In fact, I often use batteries I buy from TSC in my equipment--they are cheaper and usually have a compatible form factor. Big trucks (like the 2 1/2 ton truck) use big truck batteries, but they are still standard batteries.

Generally everything that can be run on 24 volts runs on 24volts. The transmission controller on HMMWVs can't, so it runs on 12volts from the dual voltage system. It is an exception! But all lights, electronics, etc., are 24 volts on military vehicles--the military doens't like multiple standards...

Would this 'simple switcher' handle the 5 amps that a headlamp draws? If so then it would be a really interesting solution. (A typical halogen headlight draws 4.5 to 5 amps.)

I suppose if you didn't care about efficiency a series regulator might work, but it would sure generate a lot of heat! Course in the winter, when it is cold out, that heat might be less of a problem. But your suggestion of a switcher (which is much more efficient) is good.

nal

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Last night I put two 12 volt sealed beam lamps that I got from a vehicle in the junk yard on the bench and tested each one at 13V .They were both halogen but appeared to be not from the same lot. Each lamp drew almost 5.0A. The power supply showed a difference of about .125A between lamps. I then wired the high beams in series and ran 28 volts, (theoretical worst case charging voltage) across them. Then I measured the voltage across each lamp. There was difference of about .450Volt between each lamp. Probably not enough to worry about. I have more lamps in the basement. I could possibly find a closer match if I really look I suppose however .450V doesn't seem like an awful lot to get upset about. Too bad I just couldn't employ a 10 amp zener diode, if such a thing existed. Imagine the size of the series resistor...What a seat warmer that would make on a cold Winter's night. Peter, I'd like to talk to you further about your military vehicles if you'd like to .It seems that we share the same hobby. Please email me privately at: snipped-for-privacy@yahoo.com Lenny

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I just noticed that the full number on my email address did not come through. The full number is 462002

They have free software to design the switcher. Since you can use an external pass transistor, you can handle whatever current you need. Keep in mind that the lamps draw more than 5 A when they are cold, so you want to double the capacity, or more. If you do, you could also power a radio or other 12 V items from one switcher.

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I liked all his characters. I watched his TV show every week, till he went off the air. I have a couple VHS tapes & DVDs of his shows. :)

The silly seagulls..

re

n his TV

y the

Wasn't he also on the Jackie Gleason show?

You could also just buy a DC-DC converter.. 24:12 at 200W will run around $170, in stock at Mouser.

Looks expensive compared to the raw components, perhaps, but I'll bet most parts for your truck cost more than that.

There's enough adjustment range that you can set it to 13.8VDC or whatever you think should be nominal. It will also run the lights at full brightness with the motor off (at the expense of some battery life, of course).

Best regards, Spehro Pefhany