Author Topic: 6 volt battery system?  (Read 6895 times)

Offline Erigorn

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6 volt battery system?
« on: March 01, 2013, 12:28:04 PM »
I hope this is in the right area. Please move if needed.

I know that standard is 12 v with 24 v sometimes used but I haven't seen much with 6 volts. My main motivation is that I began working on a DIY wind turbine and although i haven't finished I'm onlycranking out about 8-9 volts in a pretty good wind (still need to mount it on the swivel  and such)

Instead of trying to rebuild from scratch with a pully or gear system to get in the 16-18volt range I thought where I am right now I could charge a 6 volt battery (golf cart). 6 volts would be enough to charge all those USB devices and AA/AAA eneloop batteries, some LED lights, etc. 

My concern is finding controllers for a 6 volt system, battery chargers that work off 6 v rather than 120 or 12, Lights that run off 6 V, etc.

does anyone know if they are availible?
Would a USB charger work directly from 6 volts or would i need to ramp it down to 5? Or would a 12 v one work since they already ramp down to 5?

Any advice would be great. Thanks

PS this will be a backup to a more standard/dedicated battery backup system.

Offline Jakevf

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Re: 6 volt battery system?
« Reply #1 on: March 01, 2013, 01:39:50 PM »
I hope this is in the right area. Please move if needed.

I know that standard is 12 v with 24 v sometimes used but I haven't seen much with 6 volts. My main motivation is that I began working on a DIY wind turbine and although i haven't finished I'm onlycranking out about 8-9 volts in a pretty good wind (still need to mount it on the swivel  and such)

Instead of trying to rebuild from scratch with a pully or gear system to get in the 16-18volt range I thought where I am right now I could charge a 6 volt battery (golf cart). 6 volts would be enough to charge all those USB devices and AA/AAA eneloop batteries, some LED lights, etc. 

My concern is finding controllers for a 6 volt system, battery chargers that work off 6 v rather than 120 or 12, Lights that run off 6 V, etc.

does anyone know if they are availible?
Would a USB charger work directly from 6 volts or would i need to ramp it down to 5? Or would a 12 v one work since they already ramp down to 5?

Any advice would be great. Thanks

PS this will be a backup to a more standard/dedicated battery backup system.

Erigorn.

My first thought was something like this:

http://www.ebay.com/itm/DC-DC-4A-4-5-32V-to-5-42V-12V-24V-step-up-BOOST-converter-power-module-/130770051722?pt=LH_DefaultDomain_0&hash=item1e7280a28a

It's called a boost converter and will efficiently convert a lower DC voltage to a higher one (at reduced amperage of course). This, or something like it, could take your turbine output (which may vary quite a bit) and turn it into a stable output voltage that you can feed into more widely available 12 V electronics to charge batteries, USB devices, etc. You can think of it as a transformer for DC voltage, thanks to modern electronics and cheap solid-state switching stuff like this is now cheaper than an equivalent transformer would be for an AC circuit.

Obviously this is cheap Chinese stuff. If someone is making this stuff state-side I don't know about it. But for this price I would be tempted to buy 2 or 3 and feel pretty comfortable with having at least 1 and probably 2 good units in the lot. Just be aware of how much power your turbine outputs and make sure you're not overloading the converter. If you have a big turbine you might need to shop for a higher-power converter if you're interested in going this route.

IF you build a 6V system you could probably hook it up to a 12V to USB converter and let the electronics that are designed to regulate 12-14V down to 5 regulate 6-7V instead. This should work but it may depend on the components used in the converter so some may work fine and others not at all. I'd be reluctant to connect 6V to a USB directly, but I've never tried it so maybe it's fine.

Offline Erigorn

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Re: 6 volt battery system?
« Reply #2 on: March 01, 2013, 09:30:11 PM »
Thanks for the advice. I think i need a bigger one than you pointed out...if i'm getting 8-9 volts i have a max of 32-36 watts. (says 0-4 amps) Off had I don't recall how many amps I will get. Its an old treadmill motor but I really would hope to be getting near 100 watts.
I'm sure they make them bigger.

When it says that it has "Output voltage :5-42V continuously adjustable" Does that mean i can set it to say 14 volts and it will always step up to that no matter what the input or does that mean i can contantly fiddle with it manually (not really an option)?

The price is certainly not outrageous.

On using 12v chargers I just wonder it they are set to reduce from anything to 5 volts or reduce it by 60% or whatever to end at 5 volts (so if starting at 6 it would end at 2.5 or something)

Thanks again.

Offline Jakevf

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Re: 6 volt battery system?
« Reply #3 on: March 01, 2013, 10:51:57 PM »
Thanks for the advice. I think i need a bigger one than you pointed out...if i'm getting 8-9 volts i have a max of 32-36 watts. (says 0-4 amps) Off had I don't recall how many amps I will get. Its an old treadmill motor but I really would hope to be getting near 100 watts.
I'm sure they make them bigger.

When it says that it has "Output voltage :5-42V continuously adjustable" Does that mean i can set it to say 14 volts and it will always step up to that no matter what the input or does that mean i can contantly fiddle with it manually (not really an option)?

The price is certainly not outrageous.

On using 12v chargers I just wonder it they are set to reduce from anything to 5 volts or reduce it by 60% or whatever to end at 5 volts (so if starting at 6 it would end at 2.5 or something)

Thanks again.

To answer you questions, yes, you should be able to set it once to 14 volts and have it maintain that as your input varies. There's a little micro processor on there that monitors the output voltage and varies the intake as needed to maintain your set output. You might need to adjust it slightly from time to time but in general the output voltage will be held as you set. As for power, looking closer at them it looks like the primary limitation is the amperage, many handle up to 3A which won't represent much power for you but the link below is to a model that at least claims to work up to 10 amps, so if your turbine was supplying 7 V you could output as much as 70 W. To get 100W through this your turbine output would have to get up to 10 V.

This looks like the closest fit:

http://www.ebay.com/itm/LED-Voltmeter-DC-DC-Step-up-Boost-Power-Supply-Module-3-0-35V-to-3-5-35V-100W-/290801352577?pt=LH_DefaultDomain_0&hash=item43b51c7f81

When you say your getting 8-9 V is that open circuit or across a load, and if across a load, what kind of load? If you're seeing 8-9 V open circuit voltage then I'd expect it to drop lower when you're actually drawing current. Before you buy a converter like this, or a bunch of 6V stuff to run off this turbine, I'd recommend having a pretty good idea of the power it can put out and the voltage you'll get under load. To do this you'll want to connect a load (a big resistor such as an incandescent light bulb for example) and measure both the current and voltage the generator is outputting. If you don't have an easy way of measuring current then you can calculate it based on the resistance of your load (Voltage = Current * Resistance) but it's best to measure both directly because resistance tends to change as the resistor heats up. You're going to have to play with the load you put across it to get something that roughly simulates your intended use conditions. If you want 100W from this turbine at 6V then your looking at 16.7 A and a resistance of 0.35 ohms... which is going to be difficult to manage, but start with a smaller load (higher ohm) and see what you find out. The best load I can think of would be a car headlamp, which is probably something like 40-60W at ~14V. I know you want more than that, but it seems like a good place to start. I wouldn't rule out a mechanical gearing or (better) chain and sprocket however, as it sounds to me like you might not be turning this motor fast enough to really get it humming.

On your question about chargers. I am about 95% sure that all or almost all 12V-5V "USB" adapters use a linear regulator which outputs 5V from any input voltage higher than ~6V (within reason). The one or two I've taken apart were done this way and I don't think there's a great alternative way to do it.

Out of curiosity, how big is your turbine?

Cheers,

Offline Erigorn

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Re: 6 volt battery system?
« Reply #4 on: March 02, 2013, 04:33:01 PM »
wow thats some great information. I hadn't thought of most of it.
The turbine has 3 blades at 2 feet each. I had been working on it and we has a pretty good wind one day so I strapped it to a saw horse and ran it out there and tried to point it into the wind. I was measureing 7-9 volts under no load. (thing sounded like it was really humming and a bit scary) its a treadmill motor that I think can get up into the 1000-2000 rpm range but won't get anywhere near that with the blades on there. I've thought of some sort of belt or chain but I already welded it in place and mounted the blades and such.
I'm hoping to increase the speed a little bit and think it will ones i can get it up about 10-15 feet and get it free rotating.

I guess its more of a science project that might provide a little backup power in a bad situation. I guess i don't really need 100 volts if i'm most just trying to keep a battery topped off.  Fun to learn about all this stuff though.

Offline Jakevf

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Re: 6 volt battery system?
« Reply #5 on: March 02, 2013, 04:58:55 PM »
wow thats some great information. I hadn't thought of most of it.
The turbine has 3 blades at 2 feet each. I had been working on it and we has a pretty good wind one day so I strapped it to a saw horse and ran it out there and tried to point it into the wind. I was measureing 7-9 volts under no load. (thing sounded like it was really humming and a bit scary) its a treadmill motor that I think can get up into the 1000-2000 rpm range but won't get anywhere near that with the blades on there. I've thought of some sort of belt or chain but I already welded it in place and mounted the blades and such.
I'm hoping to increase the speed a little bit and think it will ones i can get it up about 10-15 feet and get it free rotating.

I guess its more of a science project that might provide a little backup power in a bad situation. I guess i don't really need 100 volts if i'm most just trying to keep a battery topped off.  Fun to learn about all this stuff though.

No problem. I looked it up once and live in a really bad place for wind power, and plan to move "home" in the next 5 years or so to a terrible place for wind, so I have to kinda experience the technology vicariously. I've also had to run through all the math and study up on the topic for my job a time or two. A 4' diameter turbine will need something like a 17-20 mph wind to pull 100W out of the air if everything's done right. The power increases by the square of the diameter (double the diameter = 4x the power) and by the cube of the wind velocity (double the wind speed => EIGHT times the power). So what you get out of it will vary wildly with how hard the wind is blowing. This is one of the big problems with wind, making something that can produce usable power in a typical breeze, but not fry itself or fly apart on a really windy day. If you get past the point of science experiment and into "this is an important source of power" you'll need to have a means of "furling" the turbine so that it actually limits how much it produces during a strong wind. This could be "go out and and take it down" or "pull a cable to activate a brake" or it can be any number of methods by which the system automatically throttles back as the wind speed exceeds design limits. As long as you're just playing with it I wouldn't worry about it too much, but it's something to keep in mind.

Offline Luke Townsley

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Re: 6 volt battery system?
« Reply #6 on: March 06, 2014, 09:41:21 AM »
The biggest problem with 6volt tech is that it takes really big cables to run any real current for any reasonable length.

More practically, it is hard to find things to run off of six volts. I agree with the idea you should just get a voltage booster to go from 6v to 12v or even higher. Unless you are in it for the challenge or have really short cable runs and need 6volts specifically, it just makes sense.