About what is the amp draw for 6 volt wipers ? I build and sell voltage dropping resistors mounted on heat sinks to run 6 volt car radios in 12 volt cars. I've been asked several times if these will work for 6 volt wiper motors in 12 volt cars, but I don't know without knowing how many amps 6 volt wipers use. 6 volt radios use about 5 amps at 6 volts. Maybe 6 volt wipers have have more than 1 speed which would be different amp draws but I'm just trying to get in the ballpark here.
Most 6V cars had vacuum wipers. I suppose amp draw would be relative a modern 6V motor will not draw nearly as much as an old one. The original fuse on stude 6V electric wipers was 15 amp. At least that is what was how the fuse panel was marked for my '53.
Figuring a 15 amp draw should put you in the ballpark; most 12V wiper motors draw about 7-8 amps, a 6V would be double...
Resistors? That's a bit crude, I think. Sure, it may work well when the current is known and stable enough, but if it varies there will also be a big change in voltage. Generally, using a resistor to drop the voltage to an electric motor is not a very good idea. Sure it's simple and usually it works well enough, but a electric motor draws WAY more current during start (or any other time it's at very low rpm) than when running on normal rpm. That means that if the resistor is dimensioned for correct voltage during normal operation, the increased current draw at startup would cause the voltage to drop way down. The motor may start but take longer time to reach normal rpm, or it might simply not start at all, because 1V or whatever it actually gets isn't enough to get it moving. Worse still, if the motor is left on but unable to start, the current may be enough to fry it. It may not be very old style, but today I'd go for electronic voltage reduction, one way or another. For low power items, I'd suggest a 7806 regulator, it's a simple device that costs probably a dollar or two (it needs a couple of small capacitors, also cheap, and a cooling fin depending on how high current you need). There are many versions of these, I think they can handle up to 1,5A or maybe 2A if you pick the right one. If you sell resistors to reduce voltage already, those would be a nice complement. More stable output, but limited current available. For higher powered items that doesn't require a stable, interference free voltage I could go for a PWM regulator. PWM is short for pulse width modulation, it works by turning the current of for (usually) thousands of times per second. If it's on 50% och off 50% of the time, the output will be equal to 50% of the input voltage - i.e, at 12V input you would get 6V output. The upside of this method is simplicity and low losses. The downside is that sensitive electronics like radios will not work on this, but lamps, motors etc. will be just fine. In theory, these regulators can be able to handle relatively high currents witn minimal losses - if the output transistor is chosen for that. The speed control on your cordless drill works this way, for example. The best method to get a nice, clean and even 6V is to use a switching step down regulator, also called a buck converter. You give it 12V, adjust it and get any lower voltage you want (within its specs) out of it. (They also often have a constant or max current adjustable, suitable for charging batteries for example.) Those regulators (and boost regulators, that can increase voltage for those who need that) are available on ebay for example. I made a quick search and found this one as an example, able to handle 12A or max 300W. It costs less than four dollars. https://www.ebay.com/itm/DC-DC-CC-C...076948&hash=item2a83f9de59:g:buUAAOSw5cRZMQV- Yeah, sure, it isn't traditional. But functional has its perks too.
You can use a 7808 in conjunction with an NPN output transistor to greatly increase the current capability of the regulator. Because there is a voltage drop of about .7 volts across the base/emitter junction of the output transistor, a 7808 (8 volt) regulator is used, which nets you 7.3 volt output. Use a large heat sink.
Or use a LM7806, it will give you just a shade under 6volts, but most loads won't care too much either way. The 2N5881 will work up to a 15Amp load (with a good heatsink)
7.3 volts is close to where a good 6 volt system would be when the charging system is in good shape. Sent from my SAMSUNG-SM-G900A using The H.A.M.B. mobile app
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