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RoboKaren
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NotThe charging bit is not easily done. Most bicycle dynamos / dynohubs produce 6 VAC (the actual voltage varies depending on speed; if they follow the German StVZO requirements, they produce at least 3 watts). The nominal 6 VAC is relatively easy to rectify to 5VDC for a USB charger, but in order to charge a 12VDC battery, you would need to rectify and step it up to 13.2 VDC. You'd most probably have to build the circuit yourself as I do not know of any off-the-shelf devices that will do this (there are IC chips that will do this, but you'd have to build the circuit yourself).

What you could do is to charge a 5VDC USB lithium-ion battery pack (using a variation of the USB Bike Generator circuit) and then use a 5VDC->12VDC step-up to power the horn (or to get a 5 or 6 VDC horn). It would be much smaller and lighter than a 12VDC lead-acid battery.

Alternately if for some reason you're set on lead-acid, you could get a 6VDC lead-acid battery. The charging voltage for these is 6.6 VDC so it'd still be a bit tough to get your dynohub to charge it safely and efficiently, but it's doable. There are as I said, 5VDC horns.

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Not easily. Most bicycle dynamos / dynohubs produce 6 VAC (the actual voltage varies depending on speed; if they follow the German StVZO requirements, they produce at least 3 watts). The nominal 6 VAC is relatively easy to rectify to 5VDC for a USB charger, but in order to charge a 12VDC battery, you would need to rectify and step it up to 13.2 VDC. You'd most probably have to build the circuit yourself as I do not know of any off-the-shelf devices that will do this (there are IC chips that will do this, but you'd have to build the circuit yourself).

What you could do is to charge a 5VDC USB lithium-ion battery pack (using a variation of the USB Bike Generator circuit) and then use a 5VDC->12VDC step-up to power the horn (or to get a 5 or 6 VDC horn). It would be much smaller and lighter than a 12VDC lead-acid battery.

Alternately if for some reason you're set on lead-acid, you could get a 6VDC lead-acid battery. The charging voltage for these is 6.6 VDC so it'd still be a bit tough to get your dynohub to charge it safely and efficiently, but it's doable. There are as I said, 5VDC horns.

Resources:

The charging bit is not easily done. Most bicycle dynamos / dynohubs produce 6 VAC (the actual voltage varies depending on speed; if they follow the German StVZO requirements, they produce at least 3 watts). The nominal 6 VAC is relatively easy to rectify to 5VDC for a USB charger, but in order to charge a 12VDC battery, you would need to rectify and step it up to 13.2 VDC. You'd most probably have to build the circuit yourself as I do not know of any off-the-shelf devices that will do this (there are IC chips that will do this, but you'd have to build the circuit yourself).

What you could do is to charge a 5VDC USB lithium-ion battery pack (using a variation of the USB Bike Generator circuit) and then use a 5VDC->12VDC step-up to power the horn (or to get a 5 or 6 VDC horn). It would be much smaller and lighter than a 12VDC lead-acid battery.

Alternately if for some reason you're set on lead-acid, you could get a 6VDC lead-acid battery. The charging voltage for these is 6.6 VDC so it'd still be a bit tough to get your dynohub to charge it safely and efficiently, but it's doable. There are as I said, 5VDC horns.

Resources:

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RoboKaren
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Not easily. Most bicycle dynamos / dynohubs only produce around 6-8 VAC (the actual voltage varies depending on speed; if they follow the German StVZO requirements, they produce at least 3 watts). ThisThe nominal 6 VAC is relatively easy to rectify to 5VDC for a USB charger, but in order to charge a 12VDC battery, you would need to rectify and step it up to 13.2 VDC. You'd most probably have to build the circuit yourself as I do not know of any off-the-shelf devices that will do this (there are IC chips that will do this, but you'd have to build the circuit yourself).

What you could do is to charge a 5VDC USB lithium-ion battery pack (using a variation of the USB Bike Generator circuit) and then use a 5VDC->12VDC step-up to power the horn (or to get a 5 or 6 VDC horn). It would be much smaller and lighter than a 12VDC lead-acid battery.

Alternately if for some reason you're set on lead-acid, you could get a 6VDC lead-acid battery. The charging voltage for these is 6.6 VDC so it'd still be a bit tough to get your dynohub to charge it safely and efficiently, but it's doable. There are as I said, 5VDC horns.

Resources:

Not easily. Most bicycle dynamos / dynohubs only produce around 6-8 VAC. This is relatively easy to rectify to 5VDC for a USB charger, but in order to charge a 12VDC battery, you would need to rectify and step it up to 13.2 VDC. You'd most probably have to build the circuit yourself as I do not know of any off-the-shelf devices that will do this (there are IC chips that will do this, but you'd have to build the circuit yourself).

What you could do is to charge a 5VDC USB lithium-ion battery pack (using a variation of the USB Bike Generator circuit) and then use a 5VDC->12VDC step-up to power the horn (or to get a 5 or 6 VDC horn). It would be much smaller and lighter than a 12VDC lead-acid battery.

Alternately if for some reason you're set on lead-acid, you could get a 6VDC lead-acid battery. The charging voltage for these is 6.6 VDC so it'd still be a bit tough to get your dynohub to charge it safely and efficiently, but it's doable. There are as I said, 5VDC horns.

Resources:

Not easily. Most bicycle dynamos / dynohubs produce 6 VAC (the actual voltage varies depending on speed; if they follow the German StVZO requirements, they produce at least 3 watts). The nominal 6 VAC is relatively easy to rectify to 5VDC for a USB charger, but in order to charge a 12VDC battery, you would need to rectify and step it up to 13.2 VDC. You'd most probably have to build the circuit yourself as I do not know of any off-the-shelf devices that will do this (there are IC chips that will do this, but you'd have to build the circuit yourself).

What you could do is to charge a 5VDC USB lithium-ion battery pack (using a variation of the USB Bike Generator circuit) and then use a 5VDC->12VDC step-up to power the horn (or to get a 5 or 6 VDC horn). It would be much smaller and lighter than a 12VDC lead-acid battery.

Alternately if for some reason you're set on lead-acid, you could get a 6VDC lead-acid battery. The charging voltage for these is 6.6 VDC so it'd still be a bit tough to get your dynohub to charge it safely and efficiently, but it's doable. There are as I said, 5VDC horns.

Resources:

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RoboKaren
  • 29.5k
  • 18
  • 93
  • 174

Not easily. Most bicycle dynamos / dynohubs only produce around 6-8 VAC. This is relatively easy to rectify to 5VDC for a USB charger, but in order to charge a 12VDC battery, you would need to rectify and step it up to 13.2 VDC. You'd most probably have to build the circuit yourself as I do not know of any off-the-shelf devices that will do this (there are IC chips that will do this, but you'd have to build the circuit yourself).

What you could do is to charge a 5VDC USB lithium-ion battery pack (using a variation of the USB Bike Generator circuit) and then use a 5VDC->12VDC step-up to power the horn (or to get a 5 or 6 VDC horn). It would be much smaller and lighter than a 12VDC lead-acid battery.

Alternately if for some reason you're set on lead-acid, you could get a 6VDC lead-acid battery. The charging voltage for these is 6.6 VDC so it'd still be a bit tough to get your dynohub to charge it safely and efficiently, but it's doable. There are as I said, 5VDC horns.

Resources: