Building a Battery Charger with Car Alternator

In summary: You will need to use a different setup with a higher wattage motor and/or a different type of alternator.
  • #1
rolly
2
0
hi
i wish to build a battery charger using a 3/4hp240voltac motor driving a 55amp car alternator will this work has anyone done this before and will my caravan batteries be oka i have a gen set to drive the electric motor all these questions i hope to be reveled rolly
 
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  • #2
Punctuation is your friend.

If I understand your problem correctly, you have a 240vac electric motor with which you wish to drive an alternator to produce a 13.6vdc output in order to charge the batteries for your van?

This would be a waste of energy, to begin with... you are using two phase 240vac wall power to turn a motor which turns a generator that makes a three phase ac voltage which is then rectified into a dc voltage to charge your batteries.

http://members.1stconnect.com/anozira/SiteTops/energy/Alternator/alternator.htm [Broken] is a decent explanation on the internal workings of an alternator along with ways to use one for other than its intended purpose. I would say that you might want to add some load other than the batteries to the alternator, and you will also need to calculate the correct rotational speed for the alternator.
 
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  • #3
As Dngrsone pointed out this is a rather inefficient way to go.

In addition you will not be able to get full rated output (55 Amps) from the alternator as 3/4 horsepower works out to about 40 amps at 13.8v.
 
  • #4
It's not that bad of a way to go. I've done it. If you already have the motor and alternator why not? Efficiency isn't always that big of a deal.
 
  • #5
True, a motor generator is almost the only way to go in some applications, like changing the frequency of a primary power source (going from, say 60Hz to 400Hz). I was just pointing out the inefficiency in this case.

With a little engineering homework, he might be able to bypass the moving parts and just run the AC straight through the regulator-section... that's a little beyond my knowledge and scope at the moment.
 
  • #6
BTW Dngrsone, he is not using 2 phase.
 
  • #7
Oh? He not American, then? I didn't know if those 50Hz/240vac systems over there were one or two phase.
 
  • #8
There is no such thing as 2-phase. Not in the sense you are thinking of it anyway.
 
  • #9
:grumpy: I'm thinking my house is powered with phases A and C from the neighborhood network... two phases of the three available from the sub-station.
 
  • #10
Dngrsone said:
:grumpy: I'm thinking my house is powered with phases A and C from the neighborhood network... two phases of the three available from the sub-station.
Residential electrical power and confusion about the number of phases has been discussed in several threads recently so I won’t get into it again (search for "phase").

FYI the typical home in the USA receives single-phase 240vac. The 120vac is derived from the 240vac.


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1. How does a car alternator work as a battery charger?

The car alternator works by using the engine's mechanical energy to turn a rotor inside the alternator, which generates an alternating current (AC). The AC current is then converted to direct current (DC) through a rectifier and then sent to the battery for charging.

2. What are the necessary components for building a battery charger with a car alternator?

The necessary components include a car alternator, a voltage regulator, a diode trio, a rectifier, a battery, and appropriate wiring and connectors.

3. Are there any safety precautions to consider when building a battery charger with a car alternator?

Yes, it is important to disconnect the negative battery cable before beginning any work on the alternator. It is also important to wear protective gear and follow proper wiring and grounding techniques to prevent electrical shocks.

4. Can a car alternator charge multiple batteries simultaneously?

Yes, a car alternator can charge multiple batteries at the same time using a parallel charging system. However, it is important to make sure the batteries are connected correctly and have similar voltage levels to avoid overcharging.

5. How long does it take to fully charge a battery using a car alternator?

The time it takes to fully charge a battery using a car alternator depends on the size and condition of the battery as well as the output of the alternator. On average, it can take anywhere from 2-8 hours to fully charge a battery.

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