$50.00 to the first person who answers this correctly.I need to solve this problem?

Question

why is my alternator (PMA) not keeping up with the load and letting my battery run down? I have a 48 volt system and I'm useing a 48 volt permenant magnet alternator unregulated direct to the battery. It takes 51 volts to charge but I'm running it between 53 to 60 volts to get these voltages I'm running at 2700 to 3000 RPM at the PMA, so far so good. According to the power curve chart at that RPM it should produce 75 AMPS. My load is 30 AMPS but it only produces 17 AMPS and I can't figure why. Why is the PMA not meeting the demand and how do i fix it? I have tried other alternators and they have a larger AMP deficit than this one. I need a fundamental reason why its not working. All the batteries,cables,and connectors are new. I've tested the RPMS the volts the AMP load and the AMP output from 4 different alternators. My PMA is producing power but will not meet demand by an average of 17 AMPS. Why?

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all answers will be tested...correct answer will be posted.

i am currently testing all answers...i will post the closest answer that is correct for me to solve my problem...thank you all...

Answer 1

You might take a close look at power curve chart and be sure the information is actually relevant, for example one web site I found (http://www.survivalunlimited.com/windpower/pmapowercurves.htm) says:
"Since we do not know the torque of the driver, this data is given in absolute separate peaks.
Amps are read as a short in the circuit closed condition. Then we read Volts in the circuit open condition. These charts do not reflect working conditions only the absolute separate readings."
if your chart is constructed similarly, you may have to run somewhat faster to actually get the output you need.

Also the comment made earlier about a rectifier is valid, if you are feeding the batteries with AC, a net _negative_ current might be expected as the discharge on the negative half of the cycle will probably be faster than the charge on the positive half

Answer 2

I'm assuming that when you say you are connecting the alternator direct to the battery you mean that you are connecting the rectified (DC) output - not trying to charge a DC system from AC. A fully charged 12v lead-acid battery is 13.2 volts. 4 of them is thus 52.8 volts. You need to exceed this voltage at the battery terminals to charge the batteries. There is a voltage drop across your rectifier diodes and your ammeter as well as the cables.You probably are not getting a high enough voltage to supply your charging current, especially if more than one alternator gives you the same results. Connect the alternator to the load AND the batteries, crank up the RPM until you see 53 volts at the battery terminals with full electrical load applied. This will be the minimum RPM you can run at. I could be more specific if supplied with your alternator specifications or model.

Answer 3

First Have you checked the diodes of the alternator to ensure you are running a DC out on all three legs of the alternators' internal windings?
Second, You should regulate the voltages, at the higher voltages, you are running 20 to 25% above nominal, which if you follow Ohm's law, will actually reduce the current by the same percentage given the same load.
Third, the higher internal resistance of a depleted battery, against a higher than normal charging voltage, will increase the internal temperature of the battery, and ultimately increase the internal resistance, ie, less current flow, less charge.
Last , recalculate your load, At the higher voltages you are running a strictly resistance load will drop the current by about 8 to 9 volts, but If you have any inductive loads included in your total load, reactive power will reduce the total load current inverse to the increase in reactance.
Oh one other item that may put all else to moot, Are you sure the battery is good?

Answer 4

You say "...permanent magnet alternator unregulated direct to the battery...", but most PMAs I came across deliver AC and not DC....
Do you have a rectifier between PMA and Battery?
Because if not, then you only make use of one half wave which would explain the 17Amps somehow.
And the other half wave DIS-charges your battery, which would also explain "...letting my battery run down..."

Your PMA will slow down, and output voltage will drop with high current demand, but not by half...

Answer 5

Your alternator is the problem. Change it. They don't last forever. Perhaps a diode has blown.
IT IS THE DIODE that allows AC current from an alternator to flow only in one direction for DC charging.
With a new alternator, your 48 volt system will recharge the batteries as designed.
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Answer 6

3/4 +1/8 = 6/8 +1/8= 7/8 1/2-3/10= 5/10-3/10=2/10 which is the same as 1/5

Answer 7

I don't understand even half of what you said. This is wild guess, but is it possible you have the polarity reversed? If the battery if fighting the alternator, that could be your problem.

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Answer 8

solve it by kirchoff's law;
all are in parallel and there's a circulating current in two loops, you measure dc current at load and current in the loop of genset and battery. observe polarities.

Answer 9

Have you tried more than one instrument for each of your measurements? Could a faulty instrument be leading you astray? Something must not be what it seems to be.

Answer 10

the permanant valgulator is unregulated configuring it to make it sustaianbly impossible to with held anything at hand in desire to make it combatibly un cooperative