Questions about feeding a solar charge controller through a small alternator

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  • butterbean
    butterbean Solar Expert Posts: 37
    Re: Questions about feeding a solar charge controller through a small alternator

    As soon as I get the scooter regulator, I'll wire it up and test it. I'll be disconnecting the positive and negative from the battery and testing them for dc current with the generator running. I do know that the generator is producing up to 16vac, so it should work well with the scooter regulator provided I wire it correctly. I have a diagram to follow, and testing will confirm if its correct or not. A rectifier and capacitors cannot bump the current up, but can a resistor or two? I know that I don't need it, just trying to figure out if any of the info people were reporting was correct.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Questions about feeding a solar charge controller through a small alternator

    Here is a very simple voltage doubler:

    Attachment not found.

    Resistors cannot boost voltage. They sometimes are used to limit maximum current flow (which can damage diodes and capacitors with high surge current on larger power systems).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Questions about feeding a solar charge controller through a small alternator

    Resistors take Voltage down, basically. Since in this case you're looking at Voltage based power sources they won't do anything to help because the current is dependent on the Voltage difference between the charge source and the battery.

    Where the advantage comes from is in rectifying the AC to produce DC: AC Voltage is measured as relative mean source; a "weighted average" along the Voltage curve of the output waveform. When this is converted to DC you get the peak Voltage of that waveform (often with a filter cap which "smooths" the rise & fall into a steady-state Voltage).

    The thing about a Voltage doubling circuit is that the same amount of power is available (disregarding losses) just the V to A ratio is changed. But it is sometimes necessary because for a battery to charge the source must have higher than battery Voltage. Otherwise the battery can only rise to whatever Voltage the charger is at and no further.

    I seem to be rambling a bit.
  • butterbean
    butterbean Solar Expert Posts: 37
    Re: Questions about feeding a solar charge controller through a small alternator

    Then it seems that the info being reported was inaccurate. Perhaps they were reading their meters incorrectly. Either way, I'm sure the scooter regulator will work well with the alternator, as scooter generators (on a gy6 its the magneto, part of the ignition system, probably the same on a lot of other scooters as well) have a similar output as my alternator, varying from ~14-30vac. I read my alternator at 16vac, so it should work just fine.
  • butterbean
    butterbean Solar Expert Posts: 37
    Re: Questions about feeding a solar charge controller through a small alternator

    The scooter regulator shipped out of Houston today. Scheduled delivery date is Thursday, so we'll see. Two other packages I ordered were scheduled to be delivered yesterday and didnt make it here till today. I'm hoping it gets here Thursday though, thats my day off.
  • butterbean
    butterbean Solar Expert Posts: 37
    Re: Questions about feeding a solar charge controller through a small alternator

    I figured out the wiring diagram for the regulator finally. As long as there isn't a short in the wiring anywhere, then the scooter regulator should work fine.
  • butterbean
    butterbean Solar Expert Posts: 37
    Re: Questions about feeding a solar charge controller through a small alternator

    The sccooter regulator got here today. I'll be wiring it up tomorrow and letting you all know how it goes.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Questions about feeding a solar charge controller through a small alternator

    Good Luck! :D

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • butterbean
    butterbean Solar Expert Posts: 37
    Re: Questions about feeding a solar charge controller through a small alternator

    The scooter regulator works, but I don't think there was anything wrong with the charger I was using, and here's why. When I first hooked up the new regulator, I was getting the same readings as before on my dmm, which was basically nothing. I checked all my wire connections and everything looked pretty good. I decided to check my fuse. Its a 4A glass fuse. I have checked it repeatedly at other times, and it wasn't blown or anything like that. But this time it was. I decided to replace it, and when I did, I got a proper dc voltage reading on my dmm. I disconnected my positive and negative wires from my battery and connected the leads of my dmm to them. After I replaced the fuse, I started the engine and gave it a little gas and got a reading of 10vdc, and that was just with starting it in place and not revving it very high. My theory is that the fuse I was using was defective out of the box, and finally blew completely when I hooked up the new regulator. Its also possible that a 4A fuse is not enough, and the fuse wasn't defective but got overloaded over time. If I blow another fuse, I'll go to a higher amp rating, maybe 10. The battery can handle up to 18A, so a 10A fuse wouldn't hurt anything.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Questions about feeding a solar charge controller through a small alternator

    Fuses are always a weak point of any design.... The are "designed" to break (with too much current).

    Remember that fuses are designed to protect your wiring... 4 amps should be more than enough for your needs...And if you use too large of fuse, you can end up cooking your wiring (and start a fire, worst case).

    Remember, you need Vregulator input > Vbatt charging. And you want to see the battery in the ~13.8-14.2 volt range with the generator running and the battery 80% charged.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • butterbean
    butterbean Solar Expert Posts: 37
    Re: Questions about feeding a solar charge controller through a small alternator

    I'll keep an eye on the fuse that's in there, but if it blows again I'll be switching to a higher amp rating. Maybe 5 or 6A.
  • butterbean
    butterbean Solar Expert Posts: 37
    Re: Questions about feeding a solar charge controller through a small alternator

    I thought fuses were mainly to protect the battery, considering the fact that there is only one fuse in my entire system and its on the wire going from the regulator to the battery. I'm not trying to sound smart, just saying that most motorcycles and scooters only have one fuse, and its usually on the wire going to the battery. How can one fuse protect all the wiring? Even when the fuse breaks, there is still current flowing through the rest of the circuit. I know because I tested the wire that connects the fuse to see if voltage was getting to it to make sure that the blown fuse was the only problem. In my case, the fuse does protect most of the system, because all my lights and my battery are connected after the fuse, but in most systems thats not the case. I'm not sure with cars though, I guess they have a bunch of fuses. I just thought that in my type of system, the main benefit of a fuse was to keep the battery from blowing up. I have no idea how many amps my alternator is producing, but the battery is supposed to be able to handle up to 18A.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Questions about feeding a solar charge controller through a small alternator

    A battery can output large amounts of current into a dead short... The alternators on a motorcycle are generally able to output a few ampere at most.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Questions about feeding a solar charge controller through a small alternator
    butterbean wrote: »
    I thought fuses were mainly to protect the battery, considering the fact that there is only one fuse in my entire system and its on the wire going from the regulator to the battery. I'm not trying to sound smart, just saying that most motorcycles and scooters only have one fuse, and its usually on the wire going to the battery. How can one fuse protect all the wiring?

    A fuse will protect any circuit it is part of from over-current, even if that circuit branches out into parallel circuits. It will not protect those individual smaller circuits. Your motorcycle has only one fuse because of two things: A). they're cheapskates and; B). people who design automotive wiring tend to do this in a very convoluted manner. :D
    Even when the fuse breaks, there is still current flowing through the rest of the circuit. I know because I tested the wire that connects the fuse to see if voltage was getting to it to make sure that the blown fuse was the only problem.

    Nope; not possible. If a fuse on a circuit blows no current flows. If you still had Voltage/current in places then there is a path around that fuse to provide it.
    In my case, the fuse does protect most of the system, because all my lights and my battery are connected after the fuse, but in most systems thats not the case. I'm not sure with cars though, I guess they have a bunch of fuses. I just thought that in my type of system, the main benefit of a fuse was to keep the battery from blowing up. I have no idea how many amps my alternator is producing, but the battery is supposed to be able to handle up to 18A.

    Much depends on whether they treat all the wiring as a whole, so that any short blows the main fuse and kills everything (acceptable on systems with very low/similar current on all paths) or need to branch out to accommodate multiple circuits that will operate at quite different currents.
  • butterbean
    butterbean Solar Expert Posts: 37
    Re: Questions about feeding a solar charge controller through a small alternator

    When I said current still flows after a fuse has blown, what I meant was the rest of the circuit not including the wire containing the fuse. When I found that the fuse in my circuit was blown, I tested the rest of the circuit with the fuse removed to see if current was flowing at all, or if there might be another problem somewhere else in the circuit. I took the end of the wire that connects to the fuse and touched one of the leads from the dmm to it and checked what the reading was. What I'm saying is, when a fuse blows, there is still current flowing through the rest of the circuit up until the point where the fuse actually is. I guess if you think of a fuse as a sort of switch, and one side of the fuse is the input and the other side is the output, then current is still flowing everywhere on the input side of the fuse, therefore I can't see how a blown fuse protects that side of the circuit. I dont know if what I said makes sense, but hopefully its not too confusing.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Questions about feeding a solar charge controller through a small alternator

    Yep, a fuse/breaker is a current sensitive switch. When there is too much current, the switch opens.

    For battery based systems, the source of high current is almost always the battery (or battery bank) itself.

    When working with larger off grid power systems, we have hundreds of AH's worth of batteries which can deliver 100's to 1,000's of Amperes into a dead short.

    Of course, your battery is much smaller, and can only deliver ~10's of amps of current into a dead short--But if you have relatively small diameter wire, that wire can still overheat and start a fire (and/or kill you battery by discharging to dead).

    No other part of a small power system (such as a small motor cycle) can deliver enough current into a dead short and overheat the wiring (in a typical small motor cycle design).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • butterbean
    butterbean Solar Expert Posts: 37
    Re: Questions about feeding a solar charge controller through a small alternator

    I see what you're saying now.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Questions about feeding a solar charge controller through a small alternator

    I think you are mistaking Voltage presence for current flow. When a fuse blows there is no more circuit so current can not flow. Voltage will still be present at any point in the circuit before the blown fuse interrupts it.
  • butterbean
    butterbean Solar Expert Posts: 37
    Re: Questions about feeding a solar charge controller through a small alternator

    On the way to work this morning, I ran both lights and the generator. The battery did not charge. On the way home from work, I didn't run the headlight and the battery did charge a little bit. So it seems I've got two choices. A), run the headlight only when needed and leave the alternator drive wheel the size it is, or B), switch to a smaller drive wheel on the alternator and see if it produces higher voltage and possibly be able to run both lights and still charge the battery. It actually seems that maybe the battery is still charging even with the headlight running, but when I stop and the battery runs the lights instead of the generator, the draw from both lights is more than what the battery has gotten charged in the amount of time I've been moving. But perhaps a smaller drive wheel would produce a bit more voltage, charging the battery faster and thus enabling me to run both lights without draining the battery too much.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Questions about feeding a solar charge controller through a small alternator

    If the alternator is turning fast enough to generate the minimum voltage to charge the battery--Then spinning it fast is probably not going to generate that much more current.

    Can you find/build a flasher circuit for your head/tail lamp? At least during the day, you could set the duty cycle to be on 1/4 second and off 3/4 of a second--This will cut your average energy usage by 3/4 and let your alternator charge the battery during the daytime portion of your ride.

    Otherwise, you probably need to figure out a higher current charging source (or lower current/power lighting). Would something like this work for you?

    12 VOLTS MINI-GEN MAX For Motorized Bicycle Lighting (you may have to search for this string on Ebay--Not sure if this is a permanent page or not)

    Basically install another coil next to your magneto--This second coil is used to charge your battery.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • butterbean
    butterbean Solar Expert Posts: 37
    Re: Questions about feeding a solar charge controller through a small alternator

    That generator wont work for me, as its designed for a different type of engine than I'm using.
  • butterbean
    butterbean Solar Expert Posts: 37
    Re: Questions about feeding a solar charge controller through a small alternator

    from my understanding with certain types of regulator/rectifiers (maybe all types, but not sure) the output is proportional to the input. When I tested the alternator, I got 16vac. Testing the regulator in the same manner (spinning the alternator roughly the same amount to check the regulator output) I only got 10vdc. A 12v battery needs 14vdc+ for anything more than trickle charging. If the alternator is producing ~16vac and the regulator is putting out 10vdc, then I probably need to get the alternator producing about ~20vac to get 14vdc output from the regulator. I may also need a 5 or 6A fuse.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Questions about feeding a solar charge controller through a small alternator

    Alternators have a maximum current limit... And as you increase RPM, mostly, it will increase output voltage.

    You want the alternator to produce >15 VDC (after rectifier) to fully/quickly charge your battery bank... However, if the battery is "dead" at 10.x volts, that will be the battery voltage until it gets more and more charge into it.

    A "simple" regulator will output maximum available current and only "regulate" when the battery approaches the voltage set point (say 14.2 volts)... At that point, the regulator reduces current to the battery to reduce over charging.

    The "typical regulator" will read (for example):

    10.0 volts battery; ~11 volts regulator input from charging source
    12.5 volts battery; ~13.x volts input
    14.0 volts battery; ~15.x volts input
    14.2 volts battery; ~15-17+ volts input

    The input and output voltages for the regulator will be pretty close together until the battery is near full charge--Then the regulator output will be "fixed" at set point voltage and the regulator input can be much higher voltage because the regulator is not letting all of the current through.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • butterbean
    butterbean Solar Expert Posts: 37
    Re: Questions about feeding a solar charge controller through a small alternator

    All I know is that at the alternator's current rpm's, its basically only maintaining the battery's current charge level, ~12.3v. I don't know if a scooter regulator is what you would refer to as a "simple" regulator or not. From doing some reading on scooter forums, some scooter stators are capable of ~30vac at idle, and the type of regulator I'm using regulates that 30vac down to about ~14vdc rectified. And from what people have said on those forums, the output of these regulators is proportional to the input. So if I want anything more than a trickle charge, I'll need to increase the input. All it really takes is a simple test, removing the larger drive wheel on the alternator and hooking up my dmm to test the output with the smaller drive wheel. If the ouput increases, then I'll know that it works. If not, then I guess I'm stuck with trickle charging or I need to figure out a way to build a step-up circuit.
  • butterbean
    butterbean Solar Expert Posts: 37
    Re: Questions about feeding a solar charge controller through a small alternator

    Unfortunately, my wall charger stopped working. Guess that's what I get for buying cheap Chinese **stuff**. Anyway, I removed the r/c car tire from the alternator and used the drive wheel it came with. Testing the output from the regulator with the battery hooked up, I'm getting 13vdc roughly while revving the engine with the bike stationary. My battery gauge tells me the battery voltage has gone up from 11.3v to 11.9v on my way to work this morning. I realize its still not fully charged, but since my wall charger is not working, not much I can do about it. Both lights are working fine, and as long as the battery is getting some charge, I'm good. Maybe if I took a nice long cruise, the battery might get charged more, but its charging about 0.5v during a 15 minute drive, so I think it will be ok for now.
  • butterbean
    butterbean Solar Expert Posts: 37
    Re: Questions about feeding a solar charge controller through a small alternator

    Figured out why my wall charger wasn't working. It starts like this. My wall charger has alligator clips, and my dmm does not. What easier way to put alligator clips on my dmm, than to take the ones off my charger and make them quick disconnect. So I bought some male/female wire connectors and removed the alligator clips from the charger. I marked the positive wire of the charger with some red shrink tube, so as to be sure which wire to connect which alligator clip to, should I ever need to use the wall charger again. I crimped male wire connectors to the ends of the aligator clips, and female connectors to my wall charger and the leads on my dmm. This way I could connect the same alligator clips to the dmm or the charger as needed. I connected the alligator clips to the dmm, and they worked just fine. Connected them to the charger, nothing. Got to thinking, maybe I didn't crimp the connectors on the charger properly. So I removed them and re-crimped them, tested the charger, and now I'm getting voltage again. I will charge the battery inside tomorrow, and once the battery is fully charged, the alternator and scooter regulator should be able to maintain the full charge. So this time I should blame my own hastiness, rather than the cheap chinese **stuff**.
  • butterbean
    butterbean Solar Expert Posts: 37
    Re: Questions about feeding a solar charge controller through a small alternator

    The alternator and scooter regulator has been keeping the battery charged fairly well. The battery has been staying right around 12.5v or higher. Its still not charging quite as well with the headlight on, but its not really a problem for clear days, so I'll just use the headlight only when I need it. Been very happy with the charging system since I got it working good.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,431 admin
    Re: Questions about feeding a solar charge controller through a small alternator

    Sounds like it will work ok... Not ideal, but if you can put it on a small AC charger once in a while, your battery to last longer.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • butterbean
    butterbean Solar Expert Posts: 37
    Re: Questions about feeding a solar charge controller through a small alternator

    Its working a lot better than it was. I might top the battery off once a month, maybe more often once the weather gets really cold. PA winters can get pretty cold, so maybe every two weeks once the temp starts dropping.
  • butterbean
    butterbean Solar Expert Posts: 37
    Re: Questions about feeding a solar charge controller through a small alternator

    I previously did not think that my battery gauge would read the output from the regulator, but I decided to switch the gauge on yesterday while driving, and it did read the voltage. My alternator is putting out up to 17v rectified through the regulator. This means the alternator itself is producing at least 21vac. Weirdly enough the headlight still drains the battery some, but not as bad as it did before.