Questions about feeding a solar charge controller through a small alternator

butterbean

I wasn't sure where to post this question, so if this is the wrong area, mods please feel free to move to the appropriate area.

A little background before I ask the question. I have a motorized bicycle. The engine doesn't run off a battery, its got a pullstart and electronic ignition. I do however use a 12v sla battery for running a headlight and a brake light. I have a "bottle dynamo", a tire-driven generator that some of you may be familiar with.

I currently have it connected to a charger that contains a simple rectifier and regulator, but I do not know if the charger has overcharge protection or not, and I doubt that it does. The generator is 12v, 5.5w. The charger does contain an inline fuse holder, which i am running a 4A glass fuse in. My battery is 1.2Ah, my headlight is 5w and my brake light is 3.6w (gotta love led's).

Understanding the limitations of rpm's in the generator and concerns for overheating, I'm using a 2" drive wheel on the generator to reduce the rpm's for motorized speeds. So here is my question.

I've been looking at this charge controller: http://www.homedepot.com/p/Sunforce-7-Amp-Solar-Charge-Controller-60012/202218721#.UiQMgv5q0VU my questions are 1), does the charge controller contain a rectifier (I know what rectifiers do, but dont know if solar panels produce ac or dc), and will it hurt anything to run this controller in tandem with my current charger, or will it simply be redundant? The reason I'd like to run this controller with my current charger is that the current charger has a fuse as I mentioned earlier.

Also, I know the controller has a maximum output of 7A, but is there a minimum input (generator is 5.5w, making it less than 0.5A output @12v. In case anyone may point out the possibility of the generator not producing enough juice to charge the battery, it already is. Before installing the generator, the battery had dropped to -9vdc, due to several days' use without a charge. After one trip back and forth to work (about 6mi round trip) the battery was up to 9.5vdc.

Also as far as what the charge controller will do with the current when the battery is full, I plan to run both lights full time once I have a proper charge controller, and since electricity takes the path of least resistance, running both lights should allow the current to divert from the charge controller to the lights and keep the charge controller's shutoff mechanism from being overridden.

So basically, are all my assumptins correct, and can I run this charge controller in tandem with my current charger, and are there any concerns I'm missing?

BB.

Re: Questions about feeding a solar charge controller through a small alternator

Welcome to the forum Butterbean!

butterbean wrote: »

I wasn't sure where to post this question, so if this is the wrong area, mods please feel free to move to the appropriate area.

A little background before I ask the question. I have a motorized bicycle. The engine doesn't run off a battery, its got a pullstart and electronic ignition. I do however use a 12v sla battery for running a headlight and a brake light. I have a "bottle dynamo", a tire-driven generator that some of you may be familiar with.

Are you sure the bottle dynamo you have is a 12 volt one? Most of them, as far as I know, are ~6 volts at 5 watts or so.

And are not very efficient--Just putting the dynamo against the tire really adds a lot of load. The higher end products are now hub type alternators.

http://www.peterwhitecycles.com/lightingsystems.htm

I currently have it connected to a charger that contains a simple rectifier and regulator, but I do not know if the charger has overcharge protection or not, and I doubt that it does. The generator is 12v, 5.5w. The charger does contain an inline fuse holder, which i am running a 4A glass fuse in. My battery is 1.2Ah, my headlight is 5w and my brake light is 3.6w (gotta love led's).

Are you sure of the generator's output voltage/current? To properly charge a 12 volt lead acid battery, you will usually need around 14.2 to 14.4 volts (sealed lead acid).

Also, how long do you expect to run the lights from the battery? If your run your lights (without using the generator), you can expect about one hour... If you run the lights too long, it will take the battery dead--And lead acid batteries do not like to be taken to "dead".

Even with the generator, it will not recharge the battery when the lights are on (5.5 watts generator, 8.6 watts of load)

Understanding the limitations of rpm's in the generator and concerns for overheating, I'm using a 2" drive wheel on the generator to reduce the rpm's for motorized speeds. So here is my question.

I've been looking at this charge controller: http://www.homedepot.com/p/Sunforce-7-Amp-Solar-Charge-Controller-60012/202218721#.UiQMgv5q0VU my questions are 1), does the charge controller contain a rectifier (I know what rectifiers do, but dont know if solar panels produce ac or dc), and will it hurt anything to run this controller in tandem with my current charger, or will it simply be redundant? The reason I'd like to run this controller with my current charger is that the current charger has a fuse as I mentioned earlier.

The charge controller does not contain a rectifier. Solar panels output DC voltage/current so none is needed. The panel you are looking for will have a Vmp (voltage maximum power) of ~17.5 volts or so typically.

Yes, you can put different charging sources in parallel. However, you should use a regulator to ensure that the battery is not over charged.

You would need to look at the output voltage of the dynamo with nothing connected. The sun force controller is probably expecting a maximum input voltage of around 25 volts--You want to make sure your dynamo does not output more than that (and should output ~15 volts minimum at 5.5 watts or ~0.3 amps to charge the 12 volt SLA battery).

Also, I know the controller has a maximum output of 7A, but is there a minimum input (generator is 5.5w, making it less than 0.5A output @12v. In case anyone may point out the possibility of the generator not producing enough juice to charge the battery, it already is. Before installing the generator, the battery had dropped to -9vdc, due to several days' use without a charge. After one trip back and forth to work (about 6mi round trip) the battery was up to 9.5vdc.

A lead acid battery is "dead" at ~10.5 volts (resting voltage). You should not take your battery below ~12.0 to 11.5 volts maximum. Below that point, the batteries usually do not have a very long life.

A resting battery should read around 12.7 volts (or a bit higher) when fully charged and resting for several hours.

Also as far as what the charge controller will do with the current when the battery is full, I plan to run both lights full time once I have a proper charge controller, and since electricity takes the path of least resistance, running both lights should allow the current to divert from the charge controller to the lights and keep the charge controller's shutoff mechanism from being overridden.

The Sunforce unit you are looking at simply "opens a switch" when the battery is full. That is why you need to make sure the dynamo does not exceed ~25 volts or it will damage the charge controller.

So basically, are all my assumptions correct, and can I run this charge controller in tandem with my current charger, and are there any concerns I'm missing?

I am a little confused--You want to install a solar panel+charge controller, or just use the Sunforce as a charge controller for the dynamo?

It can work if the generator+rectifier (that you supply) has less than ~25 volts output with no load.

But at this point, at least according to specifications, your dynamo has less output current/wattage than your loads draw. You cannot run the lights 100% of the time when biking. The battery will never get charged. You will need a second charger (AC wall charger, solar panels, etc.) to actually fully charge the battery between rides.

-Bill

butterbean

Re: Questions about feeding a solar charge controller through a small alternator

Thank you for your response. I'll try to cover all the points you brought up.

Yes, I'm sure the generator is 12v. It says 12v, 5.5w for the headlight and 2.5v, 0.5w for a tail light. I'm not using the tail light connection at all. Since my wall charger is 12v, I assume that a sealed lead acid battery can be charged with 12v, even though 13v is optimal. I did some research on charging requirements for 12v lead-acid batteries, and the charging requirement increase in input vs output is only ~0.2v per cell. Apparently, 12v sla batteries are one cell, so its perfectly acceptable to charge them on 12v.

The plan is to fully charge the battery with my wall charger, then install the charge controller and run the generator full-time. When the battery is charged, the generator will power the lights and the charge controller will cut off the charge to the battery. The battery will only take a charge when its needed.

Fyi, this is how a charging circuit works on a motorcycle or scooter. I do realize that technically the draw exceeds the output of the generator, but seeing that the total draw of both lights is less than 1 amp, I don't think it will hurt anything. Also, the brake light is only on when I stop, so in actuality the full-time draw would be 5w, then 3.6w intermittently whenever I use the brake light, then whatever the battery draws intermittently when it needs a charge. Rough estimate shows my charge rate from the generator to be about 1v per hour.

I also think that you may have missed a couple things in my OP, and I apologize if it was confusing. The first thing I think you missed is that this is on a motorized bicycle. Its propelled by a 98cc minibike engine, meaning that I almost never pedal. The reason I mentioned this again is to explain what I meant about the rpm's of the generator. These generators are designed to produce 12v at pedal speeds. I'm no expert, but most motors produce a certain amount of power based on the rpm's they produce. On a motorized bike, the rear wheel is spinning at least twice as fast as it would at normal pedal speeds. Now I dont know if this means the generator would produce twice the voltage, because every motor has its power limits regardless or rpm's. So what I did was calculate the rpm's of the generator at pedal speeds based on a standard size drive wheel (what comes with the generator) and a 26" wheel (the size wheel I'm using). I then calculated the rpm's of the generator at motorized speeds using the same size bicycle wheel and a 2" r/c car tire as the generator drive wheel. The rpm's I came up with for both sets of figures are comparable to one another. My reason for wanting to limit the rpm's of the generator was for concerns with overheating the generator or overpowering my charging circuit. The second thing I think you missed was that my generator is already charging my battery.

The voltage of the battery went up 0.5v after one trip back and forth to work. As far as the battery being dead below a certain voltage, both my lights still work at ~9vdc, albeit not as brightly. And to clarify, here is how my charging circuit is setup. The generator is connected to a charger that contains a rectifier and voltage regulator. The charger, which also has a 4A inline fuse in the positive output wire, is connected to a terminal. It is a rockford fosgate single pole terminal with 5 connections. It can be used as positive or negative, but I have it set up as a positive terminal for obvious reasons.

The charger, the battery, both lights and a digital battery gauge are connected to the power terminal. The generator can power anything that is connected to the power terminal, and everything is grounded to the frame. The goal is to wire the charge controller between the charger and the battery. If the charge controller can handle up to 25v, this should be no problem as the charger has a voltage regulator in it. For further clarification, I am not using a solar charger, just the generator and charger I currently have.

Again I apologize for any confusion in the OP. I've tried to clarify everything as well as cover all the points you brought up. Basically the main reason for installing the charge controller is to be able to run the generator full time without overcharging the battery, and also prevent the battery from discharging when its not being used. Once the battery is fully charged, it will only power the lights when I'm stopped. The rest of the time, the generator will power the lights.

butterbean

Re: Questions about feeding a solar charge controller through a small alternator

I missed one point you brought up. The generator isn't creating any extra drag on the rear wheel. The r/c car wheel I'm using to drive the generator is rubber, and the bicycle tire is also rubber, and I'm driving the generator off the bicycle tire, so its rubber on rubber. I did some research and rubber on rubber provides a greater coefficient of friction than rubber on any other material. This means better grip and less wear. I also know from personal experience that rubber brake pads wear out very quickly on a steel rim on a motorized bike, so a rubber wheel on a metal rim would probably do the same. The softer the rubber, the faster it wear, and the rubber of the r/c car tire is much softer than a brake pad. I no longer use caliper brakes for this reason. I realize that most modern bicycle dynamos are hub driven, but they are far more expensive than a bottle generator. I got the generator as part of a kit that included a headlight and tail light to be used with the generator (neither of which I'm currently using) for $25 with free shipping. Those dynamo hubs cost about 4 times that, and thats just the hub alone. I'd still have to lace it into a wheel myself. I'm completely fine with my setup.

butterbean

Re: Questions about feeding a solar charge controller through a small alternator

Now here is another question. Does the charge controller have only one positive and negative? Can I connect it directly to my battery and still have the battery run the lights while the charge controller is connected? I had assumed the charge controller would have input and output wires, and the current would flow through its circuit, but now it seems like all the charge controller does is read the voltage and switch the current on or off, basically making it a "smart switch" for the battery. I guess maybe I'm a little confused?

BB.

Re: Questions about feeding a solar charge controller through a small alternator

A "simple" PWM controller is just a "smart switch". It is "on" when the battery needs charging. As the battery starts to reach 14.4 volts (or whatever) the switch starts cycling on and off (PWM pulse width modulation... spends more time in "off" to reduce the average current to the battery.

And it needs a ground connection to the battery (to measure voltage and get a little power for its electronics).

You may have one ground lead, or two (one to solar panel, a second to the battery)--Most (but not all) controllers, the ground lead on the panel side and on the battery side are the same.

-Bill

butterbean

Re: Questions about feeding a solar charge controller through a small alternator

I answered part of my own question just by thinking about it. I don't want the charge controller between the generator and the rest of the circuit, because the charge controller shuts off the circuit when the battery is full, therefore no power from the generator when the battery is full. It is possible to disengage the generator when the battery is full (I have a battery gauge), but the whole point of using the charge controller is to be able to run the generator full time without worrying about the battery overcharging. I also wouldn't want the generator running and producing current without it going anywhere, so the best way to use the charge controller is to connect it directly to the battery. The user manual for that charge controller says to connect the alligator clips to the battery, I'm good with that, red to positive, black to negative. The one part I'm confused about is how the charge controller prevents the battery from discharging. I understand what a blocking diode does, what I'm not sure about is when I come to a stop and my generator is not producing anything, will my lights be able to draw frrom the battery or does the blocking diode just prevent backflow to the generator and not the rest of the system?

PNjunction

Re: Questions about feeding a solar charge controller through a small alternator

Man, even after pouring myself 3 espressos and traveling through a time portal once or twice it was hard to keep up.

As long as you do this SAFELY, I think you'll have to be the pioneer on this project.

The basics: a 1.2ah agm sla. A cheap solar charge controller that is merely an on/off switch at 14.6v high and 13.2v low. The charge controller is essentially serving as a reverse-current blocking diode itself, so no need to wire an external one. A charge supply that slightly exceeds the normal ups-style agm rating of .25 to .3C current. You 1.2ah agm is only probably rated to handle 360 milliamps current inrush max, perhaps less.

With all the variables introduced here in a non-solar application more or less, I'd say do so if you can do so safely as long as your TOTAL charge current does not exceed .25 to .3C, that is 360 milliamps charge. The label on your battery, or it's own data sheet will be more accurate. Other than that, it is hard to predict how successful this project will be in the long run.

BB.

Re: Questions about feeding a solar charge controller through a small alternator

butterbean wrote: »

Yes, I'm sure the generator is 12v. It says 12v, 5.5w for the headlight and 2.5v, 0.5w for a tail light. I'm not using the tail light connection at all. Since my wall charger is 12v, I assume that a sealed lead acid battery can be charged with 12v, even though 13v is optimal. I did some research on charging requirements for 12v lead-acid batteries, and the charging requirement increase in input vs output is only ~0.2v per cell. Apparently, 12v sla batteries are one cell, so its perfectly acceptable to charge them on 12v.

Working backwards, a 12 volt lead acid (SLA, VRLA, AGM, GEL, Flooded, etc.) are all ~2 volt cells. Your battery has 6x 2 volt cells.

To "quickly recharge" your battery, I am guessing it is will need ~14.2 to 14.4 volts and be able to hold that for 1-4 hours. You can, slowly, charge the battery at 13.8 volts. A fully charged battery, resting, will be around 12.7 volts.

At 11.5 volts resting, the battery is ~20% state of charge. At 10.5 volts, the battery is, effectively, dead.

The plan is to fully charge the battery with my wall charger, then install the charge controller and run the generator full-time. When the battery is charged, the generator will power the lights and the charge controller will cut off the charge to the battery. The battery will only take a charge when its needed.

I am not sure how you are wiring the charger, or what you are using specifically... Batteries are pretty simple... >13.8 volts, they are charging. Under 12.7 volts, the are discharging (or less than fully charged).

Fyi, this is how a charging circuit works on a motorcycle or scooter. I do realize that technically the draw exceeds the output of the generator, but seeing that the total draw of both lights is less than 1 amp, I don't think it will hurt anything. Also, the brake light is only on when I stop, so in actuality the full-time draw would be 5w, then 3.6w intermittently whenever I use the brake light, then whatever the battery draws intermittently when it needs a charge. Rough estimate shows my charge rate from the generator to be about 1v per hour.

The voltage/current profile on a Lead Acid battery is not straight forward. And to estimate that it rises ~1 volt per hour from 9-10 volts is not really useful. That would be charging from Dead to Dead.

Lead Acid batteries are nearly 100% efficient based on current flow... If you have a 1.2 AH battery, and input 0.3 amps for 4 hours, it will be almost full (0.3 amps * 4 hours = 1.2. Amp*Hours).

I also think that you may have missed a couple things in my OP, and I apologize if it was confusing. The first thing I think you missed is that this is on a motorized bicycle. Its propelled by a 98cc minibike engine, meaning that I almost never pedal. The reason I mentioned this again is to explain what I meant about the rpm's of the generator.

I understood that-- was not sure how much is peddle vs how much is motor--If you are motoring most of the time, then using that as your average speed is fine.

These generators are designed to produce 12v at pedal speeds. I'm no expert, but most motors produce a certain amount of power based on the rpm's they produce. On a motorized bike, the rear wheel is spinning at least twice as fast as it would at normal pedal speeds. Now I dont know if this means the generator would produce twice the voltage, because every motor has its power limits regardless or rpm's. So what I did was calculate the rpm's of the generator at pedal speeds based on a standard size drive wheel (what comes with the generator) and a 26" wheel (the size wheel I'm using). I then calculated the rpm's of the generator at motorized speeds using the same size bicycle wheel and a 2" r/c car tire as the generator drive wheel. The rpm's I came up with for both sets of figures are comparable to one another. My reason for wanting to limit the rpm's of the generator was for concerns with overheating the generator or overpowering my charging circuit. The second thing I think you missed was that my generator is already charging my battery.

I agree with your math on the RPM. And if you have a 12 volt rated alternator--That is good. Alternators will typically output a maximum current (say 0.5 amps * 12 volts = 6 watts). You need ~14.4 volts to charge, so you should spin the alternator ~1.2 times faster to increase its output voltage (assuming it is capable of the RPM and does not have any sort of shunt regulator internally).

If the alternator is designed to output 12 volts for lighting... That is not the same as 14.4 volts for battery charging. Another issue is that assuming this is a Permanent Magnet Alternator, it is outputting AC Voltage/Current and you are using a full wave rectifier. The sine wave voltage peak is about 1.4x higher than the RMS AC voltage from the alternator. So, with a rectifier, it is possible that it is capable of pushing >14.0 volts to the battery (at a reduced duty cycle, because of the sine wave peaks are only >14.0 volts for part of a cycle--and you have rectifier losses).

The voltage of the battery went up 0.5v after one trip back and forth to work. As far as the battery being dead below a certain voltage, both my lights still work at ~9vdc, albeit not as brightly. And to clarify, here is how my charging circuit is setup.

If you are seeing the LED lights dim--More than likely, their operating current/power is 1/4 or less than the "5/3.6 watt rated power). The way our eyes perceive light intensity, we can barely see a factor of 2x or 1/2x change in output (logarithmic scale for how our eyes respond to light). A factor of 10 of 1/10 times is a major difference.

So--with your battery at ~9.x volts, your electrical draw is probably closer to 1-2 watts, and your 5 watt generator may be making some head way in recharging the battery (but not much).

The generator is connected to a charger that contains a rectifier and voltage regulator. The charger, which also has a 4A inline fuse in the positive output wire, is connected to a terminal. It is a rockford fosgate single pole terminal with 5 connections. It can be used as positive or negative, but I have it set up as a positive terminal for obvious reasons.

Do you have any information on the regulator (brand/model/link)? I am not sure if this is your AC charger, or something made for the bike generator/battery set you have.

The charger, the battery, both lights and a digital battery gauge are connected to the power terminal. The generator can power anything that is connected to the power terminal, and everything is grounded to the frame. The goal is to wire the charge controller between the charger and the battery. If the charge controller can handle up to 25v, this should be no problem as the charger has a voltage regulator in it. For further clarification, I am not using a solar charger, just the generator and charger I currently have.

What is the digital battery gauge telling you? Volts, percent of battery capacity?

Again I apologize for any confusion in the OP. I've tried to clarify everything as well as cover all the points you brought up. Basically the main reason for installing the charge controller is to be able to run the generator full time without overcharging the battery, and also prevent the battery from discharging when its not being used. Once the battery is fully charged, it will only power the lights when I'm stopped. The rest of the time, the generator will power the lights.

Not a problem... Many threads start out this way trying to understand your setup and issues from opening posts.

Anyway--Lead Acid battery chemistry is pretty well defined and understood. If you have Li-Ion, NiMH, NiCad, or other chemistry, it would be a different discussion.

At this point, you have a severely "dead" 12 volt battery (based on what you have said so far). You can confirm by measuring the voltage at the battery terminals (no diode/rectifier drops, flaky wiring, etc.)...

And, you could get some more information... What is the voltage output of the alternator and output current (use a voltage/current meter that can measure AC and DC values). And see what is happening.

If you are going to work a lot with DC power--An AC/DC Current Clamp DMM is really nice of this (here is one not too expensive). For smaller battery systems, one of these RC battery monitors can work well (unfortunately, they only measure current in one direction).

-Bill

butterbean

Re: Questions about feeding a solar charge controller through a small alternator

If the battery were fully charged, I'm guessing the current from the alternator is just enough to maintain a trickle charge. I drove the bike to work without wall-charging the battery because I wanted to get an idea of how fast the alternator/charger puts current through the battery, not for any sort of hard data, just to get a rough idea of the charge rate. I don't have much info on the charger I am using. What I can tell you, which is pretty much useless, is that the charger is made and sold by a store on ebay that designs and sells custom made lighting products for motorized bicycles. I emailed them and they told me that it contains a rectifier and regulator, but wouldn't say much else about it, most likely for proprietary reasons. Here is a link to it: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=400108748072 I have a dmm from harbor freight cost me $3 on sale. I've tried testing the voltage of the generator at the power terminal by putting the bike up on the kickstand (double kickstand, the bike leans forward on the front wheel and the back wheel can spin freely) and starting the engine, giving it gas while having the multimeter connected to the power terminal. The voltage fluctuated a bit, making it difficult to get an accurate reading. I also don't give it too much gas for too long for fear of overrevving the engine with no load on it. But I did once get a reading of 26vdc at the power terminal, this would be the voltage of the battery plus the voltage of the alternator, so I think the alternator is capable of 14v+dc, at least with no load (bike stationary). The battery gauge (sort of homemade, just to give some background, I bought a battery meter on amazon for $10, intended for a boat panel, then I gutted a tail light and epoxied the battery meter into the tail light housing. The tail light is the type with a snap-on cover that you pry off with a coin or screwdriver to change the batteries, obviously I left the cover off after putting the battery meter in the housing. I zip-tied the tail light housing to my handlebars and voila! homemade battery gauge) only reads voltage. It has a maximum input of 30v. I connected it to my power terminal hoping it would give me a reading of the battery as well as the alternator, but even with the alternator engaged it only reads battery voltage, which I thought odd but whatever, I only really need it to tell me if my battery is charged or not. The meter works, but currently I don't have it grounded as I'm waiting on a switch to turn it on or off. Once I get the switch, I'll ground the meter and be able to turn it on when I need to see my battery voltage. I know it sounds like a lot of work for something I wont always use, but this way I can read my battery voltage without having to dig out my dmm. The switch for the meter will be here tomorrow. Its a rocker switch that is designed to mount on my handlebars. I am curious what my battery voltage would read right now, I think I'll go check with the dmm right on the battery terminals as you suggested. If its more than the meter displays, then the meter is not accurate. We'll see what happens with that.

butterbean

Re: Questions about feeding a solar charge controller through a small alternator

The dmm reads 9.1v at the battery and at the power terminal, but the battery meter only reads 8.6. This is not good.

butterbean

Re: Questions about feeding a solar charge controller through a small alternator

Maybe the accuracy of the meter is affected by the charge state of the battery. The battery is almost dead right now, perhaps that is causing the meter to not be accurate. I guess I'll know more after I charge the battery tomorrow.

butterbean

Re: Questions about feeding a solar charge controller through a small alternator

Here is something interesting. I just tested my wall charger with my dmm for kicks and giggles. Maybe this is just a no-load voltage, but the charger only reads 11.7v. If that's what the wall charger puts out and it can effectively charge the battery (which it already has), then the battery should charge fine off the alternator.

BB.

Re: Questions about feeding a solar charge controller through a small alternator

Put the wall charger on the battery and monitor the battery voltage (check it once every hour or so)--And see what happens.



[TH="width: 132, bgcolor: #FFFFFF, align: center"]State of Charge[/TH]
[TH="width: 132, bgcolor: #FFFFFF, align: center"]12 Volt battery[/TH]
[TH="width: 132, bgcolor: #FFFFFF, align: center"]Volts per Cell[/TH]


100%
12.7
2.12


90%
12.5
2.08


80%
12.42
2.07


70%
12.32
2.05


60%
12.20
2.03


50%
12.06
2.01


40%
11.9
1.98


30%
11.75
1.96


20%
11.58
1.93


10%
11.31
1.89


0
10.5
1.75



You can read more about batteries here:

http://www.solar-electric.com/deep-cycle-battery-faq.html

New poster "leaf" has a really nice set of charts that compare battery voltage against different rates of discharging and charging (as well as resting voltage readings).

leaf wrote: »

Am trying to upload the charts I am using...

Attachment not found.Attachment not found.

[note charts are from: I believe those charts are from Home Power #36, August- September 1993. Lead-Acid Battery State of Charge vs. Voltage ©1993 Richard Perez.
Here is a link: http://www.scubaengineer.com/documen...ing_graphs.pdf

vtMaps]

I don't quite a agree with the resting voltage line (I think the voltage is a bit low)--But it shows how to estimate a battery's state of charge while operating.

Note, where the charts "flatten out"--the room for error estimating state of charge is pretty high.

-Bill

butterbean

Re: Questions about feeding a solar charge controller through a small alternator

Well, my switch for my battery gauge got here today. The company I ordered it from said it was a single pole, it sort of is but the way they designed it was as a killswitch. Its meant to short out a connection by connecting the positive and negative. But you can use it as a single pole, just connect both wires to the positive and it completes the circuit instead of shorting it out. I've already got it hooked up. I'm charging my battery right now. I tested the load voltage of the charger when I put the battery on it, and it was 13.0v. I'll keep testing it to see if anything changes. I'm going to let the battery fully charge while I do other stuff. I'll be picking up the charge controller from home depot this weekend.

BB.

Re: Questions about feeding a solar charge controller through a small alternator

Check the specifications for the solar charge controller's maximum input voltage... It sounds like your AC generator can exceed the input voltage rating at high speeds.

I am still a little confused about where you will be using the solar charge controller... You already have a bike generator/charge controller and a wall charger--What/how are you planning on using the solar charge controller if you are not using a solar panel?

-Bill

butterbean

Re: Questions about feeding a solar charge controller through a small alternator

When I said I tested the load voltage of the charger while it was charging my battery, I meant I tested my wall charger. No-load voltage (not charging anything) was 11.7vdc. Load voltage (charging the battery) was 13vdc. The battery is wall-charging right now. The charger that I am using on the bike right now isn't a charge controller as far as I can tell, just a simple regulator/rectifier like you might find on a scooter, minus the funky wiring harness. The charger has a positive and negative input and a positive and negative output. The positive input of the charger is wired to the generator, and the positive output is connected to my power distributor, which my battery is also connected to. To my knowledge, the charger I am using does not have overcharge protection, thus the interest in a charge controller. I will not be using a solar charger at all, just my alternator and charger that I'm currently using. I will be connecting the charge controller directly to the battery (I think anyway, might have to think on that some more once I get the cc and see what's what with it).

BB.

Re: Questions about feeding a solar charge controller through a small alternator

Until you can hold the battery >14.0 volts for several hours--You do not have to worry about over charging yet. That little volt meter will tell you how good the present charging system (without charge controller) is working for you.

If you present charger cannot hold the battery >13.8 volts at a minimum, adding a charge controller will not help, and may make things worse (need another 1 volt or so for controller voltage drop too).

-Bill

butterbean

Re: Questions about feeding a solar charge controller through a small alternator

Are you saying that I can run my alternator full time without ever overcharging the battery? If that's what you're saying, I think I understand why. I think the reason you are saying that is because since the alternator is not constant (being driven by the tire means when the bike stops, the alternator stops), the battery will never overcharge because its simply not getting a constant, uninterrupted current. Also, when the battery is full, even though it has no inherent overcharge protection of its own, wouldn't there still be at least some resistance? And since electricity always takes the path of least resistance, when the battery is fully charged, any energy produced by the alternator would automatically divert to the lights? Am I making the correct assumptions, or am I way off-base here?

butterbean

Re: Questions about feeding a solar charge controller through a small alternator

The battery gauge I installed on my handlebars turned out to be accurate after all. I just finished wall charging the battery and putting it back on the bike. I flipped the switch that controls my battery gauge, and it read 12.2v. When I finished charging the battery, it read 12.7 with the dmm, but after putting it back on the bike and connecting both wires to it, it read 12.3. The battery gauge is accurate within 0.1v, just as the description on amazon said it would be. I'm good with that.

BB.

Re: Questions about feeding a solar charge controller through a small alternator

Yes--You don't need a regulator unless the battery is being overcharged.

And, yes, you are only driving a few hours a day--Not the same as plugging a wall charger in 24x7.

The generator is a source of current--The battery and loads will share the available current from the generator, and the battery will add its own current to the loads if the battery bus voltage falls below ~12.7 volts.

At this point, it still sounds like your battery is undercharged.

You should plug it into the wall charger and monitor with it a DMM. Ideally, you want to see ~14.0 to 14.2 volts or so for 2-4 hours. Then unplug from the wall charger. And after resting for 3+ hours (or over night), see what the resting voltage is... Ideally, it should be ~12.7 volts or a little higher.

Once you get the battery charged and on the motor bike, monitor the battery voltage... As long as the voltage is between ~13.0 volts and 14.4 volts you are doing OK... If you see the voltage drifting to 12.6 to 12.0 volts--You will need to recharge the battery (or a bigger bike generator).

-Bill

butterbean

Re: Questions about feeding a solar charge controller through a small alternator

I'll see what happens after a few rides back and forth to work. If the battery voltage drops again, I'll bring it inside to top off again and leave it on the charger longer this time. For now, I'll just see how it does with charging off the generator. I really appreciate all the info, though. I got the idea of using a charge controller from a fellow motorbiker on another forum, but I think he's kind of a stuffy know-it-all who doesn't really know anything. He criticized me and condescended to me for having the creativity to install a battery gauge on my handlebars, and when I decided to take some of his advice and asked him a few questions, he ignored me. He is using a solar charge controller with a "12v, 5-6 amp alternator and a bridge circuit, with repeated 10-20 second discharges at 30-60 watts and similar charging, and the battery and charge controller are in a poorly ventilated box with lots of stop and go riding in 95 degree heat". Supposedly he has been running this setup for 18 months with no problems and describes his setup as "unique to his application". And this person has the nerve to condescend to me about using a battery gauge, because it might keep my eyes off the road and no other motorbiker has ever bothered to try to use one.

ggunn

Re: Questions about feeding a solar charge controller through a small alternator

butterbean wrote: »

...since electricity always takes the path of least resistance...

People always say that, and it's incorrect. Electricity takes all the paths it can simultaneously. The current in each path is inversely proportional to the resistance of the path.

butterbean

Re: Questions about feeding a solar charge controller through a small alternator

Well, I decided to see how my generator was working today by disconnecting the battery, turning the headlight on and revving the engine with the bike stationary to see if the light came on at all. It did not. So I grabbed the dmm, and tested the generator. Less than 1v. I'm theorizing that the generator was not grounded very well. I made a ground cable and connected one end to one of the bolts holding the generator to the frame. I connected the other end to the seatpost clamp bolt where most everything else is grounded. I didn't really have time to test the generator after connecting the ground cable, so we'll see what happens next time I drive the bike.

butterbean

Re: Questions about feeding a solar charge controller through a small alternator

So I was testing the output voltage of the charger for dc and got less than 0.5v. I was also testing the generator for dc voltage and getting the same reading. It then occurred to me at a later time that the generator is not dc, but ac. Switched the dmm to ac voltage to test the generator, 16vac. Haven't tested the charger output for ac voltage yet, but I'm betting that I'll get a reading of about ~14vac. I emailed the vendor that sells the charger (which by the way looks to be a copy of a universal snowmobile regulator), and was told that the charger unit contains a regulator and rectifier. What I wasn't told but am betting is that they also installed a capacitor and a resistor, which I understand from reading on other forums will convert the dc output back to ac and bump it up. Its also possible that the charger was somehow damaged or overloaded. Its like $40 and I don't have that kind of money, so I ordered a scooter regulator (4 pin, $8 with free shipping, us seller) and am going to use that instead. One thing I do know, the generator currently does not power my lights (generator output through charger output wired to power distributor, which my lights and battery are also connected to, which means the generator should power the entire system), so I'm betting its more likely that my charger somehow got fried, because my lights will run on ac or dc.

Cariboocoot

Re: Questions about feeding a solar charge controller through a small alternator

butterbean wrote: »

What I wasn't told but am betting is that they also installed a capacitor and a resistor, which I understand from reading on other forums will convert the dc output back to ac and bump it up.

Nope.
That's why you shouldn't read other forums.

Your lights will run on either AC or DC, true. But your battery isn't going to charge from AC.

If your generator puts out AC you need at least one rectifier to provide DC for charging. That is simple and cheap enough to accomplish.

It does sound as though your wall charger has a problem. Try connecting it to the battery and measuring the current flow - see if there is any. Possibly its rectifier(s) fried but the transformer is still good. In that case installing the regulator you bought may well solve that problem.

Forty years ago I did this same project with a bicycle and wheel generator. We didn't have the technology then for Voltage regulators on a chip, but there wasn't much problem because the whole hing was low Voltage and low current - little chance of overcharging the battery. My regulator? If the light got bright, shut the generator off.

BB.

Re: Questions about feeding a solar charge controller through a small alternator

I am not quite sure what is going on with the AC battery charger... Generally, they have a small transformer and a rectifier. Many do not even have a regulator (you have to unplug them when the battery is full). Many chargers can be fried if they are connected backwards--But some are "polarity protected" and will not be damaged.

If there is a filter capacitor--It will not make a big difference to you.

Regarding your lighting, LEDs do need a DC voltage to light (only will light with "forward" current). If you feed them AC, they will be 1/2 as bright and may be damaged during the other 1/2 of the AC cycle (LEDs are diodes, but usually do not have a very high Vreverse rated withstand voltage).

-Bill

butterbean

Re: Questions about feeding a solar charge controller through a small alternator

When I said the charger might be fried, I was referring to the charger unit on the bike, not the wall-charger. Sorry for the confusion. Other people have said that with a 6v system (different type of engine than mine, not a generator, voltage of the engine electrical system, secondary wire on the coil for lighting etc) and a circuit consisting of a rectifier, a capacitor and a resistor or two, they bumped the voltage up from 6vac to ~15vac. I'm no expert, but the only way I can figure a circuit with a rectifier would put out ac is if the capacitor and the resistor were wired in on the output side of the rectifier, and this combination somehow inverted the current. That is why I think my charger was designed the same way. Testing the output wire for ac voltage and getting a positive reading would confirm this theory, but I haven't gotten that far. It is also likely that the charger unit was assembled correctly and designed to output dc voltage, and somehow got fried. I have disconnected my battery several times and attempted to see if the lights would run off the generator/charger, and they do not. Seems to me if the charger were putting out enough ac voltage, the lights should still run with the battery disconnected, if the generator is producing voltage. But like I said, I ordered a scooter regulator/rectifier, and when that gets here I'll wire it up and test it. Hopefully I get better results with it.

butterbean

Re: Questions about feeding a solar charge controller through a small alternator

Regarding the led lights, they are automotive lights and according to the vendor's description can run on 8-30vdc or 12vac. I think with the right circuitry built into them, this would easily be possible.

BB.

Re: Questions about feeding a solar charge controller through a small alternator

If you have a 6 Volt alternator, you can use diodes and capacitors to make a voltage doubler.

http://www.allaboutcircuits.com/vol_3/chpt_3/8.html

-Bill

Cariboocoot

Re: Questions about feeding a solar charge controller through a small alternator

butterbean wrote: »

When I said the charger might be fried, I was referring to the charger unit on the bike, not the wall-charger. Sorry for the confusion. Other people have said that with a 6v system (different type of engine than mine, not a generator, voltage of the engine electrical system, secondary wire on the coil for lighting etc) and a circuit consisting of a rectifier, a capacitor and a resistor or two, they bumped the voltage up from 6vac to ~15vac. I'm no expert, but the only way I can figure a circuit with a rectifier would put out ac is if the capacitor and the resistor were wired in on the output side of the rectifier, and this combination somehow inverted the current. That is why I think my charger was designed the same way. Testing the output wire for ac voltage and getting a positive reading would confirm this theory, but I haven't gotten that far. It is also likely that the charger unit was assembled correctly and designed to output dc voltage, and somehow got fried. I have disconnected my battery several times and attempted to see if the lights would run off the generator/charger, and they do not. Seems to me if the charger were putting out enough ac voltage, the lights should still run with the battery disconnected, if the generator is producing voltage. But like I said, I ordered a scooter regulator/rectifier, and when that gets here I'll wire it up and test it. Hopefully I get better results with it.

They didn't turn 6 VAC into 15 VAC with a rectifier and a capacitor. It isn't possible. Probably they were reading the AC on the DC scale, which will be low, and then rectified and filtered it and voilà! 15 VDC.

Curiously there is a way to use a couple of capacitors and a couple of rectifiers to turn a VAC into 2XVDC - a Voltage doubling circuit. But for all practical purposes you don't need this.

If I were you I'd sort out your system according to both Voltage and current type and make sure both charging sources agree with each other in that respect - and the load as well.