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When batteries run low out on tail lights - what happens?

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When batteries run low out on tail lights - what happens?

Old 09-05-11, 08:00 PM
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Easy Peasy
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When batteries run low out on tail lights - what happens?

For example, Planet Bike and RAdbot 1000, what happens when batteries run low or out. Do they get progressively dimmer or do they just stop working? Thank you.
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Old 09-05-11, 08:26 PM
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Both, it depends.

The Radbot light is so bright that it looks OK even when the batteries are almost dead. When the batteries are almost gone, mine shuts off over a bump once in a while. New batteries and it's fine. If yours start shutting off on a bump don't worry about the light, just put in new batteries. I use rechargeable batteries and have a very nice charger and an excellent battery tester. That's how I know the low batteries cause it to shut off.I just carry an extra light. Now I know to recharge the batteries before they get very low. The planet bike super flash opens with a coin in just a second, so it's convenient to just carry extra batteries. The Radbot needs a screwdriver to change the batteries. Not so nice on the road, That's why I often carry an extra light.
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Old 09-05-11, 08:53 PM
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My PB SuperFlash does get dimmer when the batteries run down. But turning it off requires two pushes of the switch. The first push switches it to constant on instead of flashing and when the batteries start to get weak it's very obvious in this mode - the light starts out bright and then dims a bit. So every time I turn the light off I end up doing a battery check at the same time. Makes me remember to change the battery while the flash mode is still at almost full brightness.
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Old 09-06-11, 12:34 AM
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When it's no longer slightly painful to look directly at my CatEye taillight, I know the batteries are on their way out.
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Old 09-06-11, 01:01 AM
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they die somewhat slowly if you use Alkaline batteries. If you use Lithium Ion they die more quickly. I never find out because I check my batteries very carefully.
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Old 09-06-11, 02:31 AM
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Originally Posted by digibud View Post
they die somewhat slowly if you use Alkaline batteries. If you use Lithium Ion they die more quickly. I never find out because I check my batteries very carefully.
I think you mean lithium (non-rechargable 1.7V), not lithium-ion (rechargable, 3.7V).
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Old 09-06-11, 09:32 AM
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Since there isn't any circuit to regulate the power the a PBSF light just blinks dimmer. However, I've seen weird things happen to Magic Shine. They will lose their normal "pulse mode" and sort of go into "dim strobe" while dimming. But there's no proof that happens to all of them.

I wonder if Dinotte has voltage/current regulation in their tail lights. I would imagine they do -same as head lights.
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Old 09-06-11, 12:10 PM
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I recharge mine periodically so they dont get low. On the off chance they should, I carry a pack of those cheap alkalines that come with cheap blinkies.
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Old 09-06-11, 03:32 PM
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Vetta TSL-C w/Flat Pack Tail Light: Flashing-> steady low, drains batteries faster!

The Vetta TSL-C w/Flat Pack Bicycle Tail Light has the interesting behavior of if it is in flashing mode (which unfortunately uses the low, not high, light output), it stops flashing and goes into steady low output. This, of course, proceeds to drain the remaining energy in the batteries even faster than the flashing mode.
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Old 09-06-11, 04:28 PM
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that may be a failsafe circuit cutting in when the voltage is too low to drive the flashing circuit.
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Old 09-06-11, 05:43 PM
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Originally Posted by Easy Peasy View Post
For example, Planet Bike and RAdbot 1000, what happens when batteries run low or out. Do they get progressively dimmer or do they just stop working? Thank you.
I don't know the answer (but from the posts others do ), but that is why I still have my reflector on the seat post, the Cherrybomb on the rack has a reflector, and the next one will probably have one as well... most likely this Cateye.
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Old 09-10-11, 09:26 PM
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A stupid question: If the light comes originally with the regular alkaline AAA batteries, can I replace them with rechargeable AAA batteries? Does it work or not?
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Old 09-10-11, 09:34 PM
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Mine gets dimmer. Batteries in my blinkies last a looong time. My LED flashlights OTOH start blinking when they're going out. What's up with that... pretty annoying.
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Old 09-11-11, 07:55 AM
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Originally Posted by vol View Post
A stupid question: If the light comes originally with the regular alkaline AAA batteries, can I replace them with rechargeable AAA batteries? Does it work or not?
It works fine. I never use anything but rechargeable batteries. Saves money if you use your light often, like commuting.
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Old 09-11-11, 12:18 PM
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Thanks, that's great. I'll do that (although I still have plenty alkaline batteries to be finished, since I don't often ride at night).
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Old 09-11-11, 04:10 PM
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Originally Posted by prathmann View Post
My PB SuperFlash does get dimmer when the batteries run down. But turning it off requires two pushes of the switch. The first push switches it to constant on instead of flashing and when the batteries start to get weak it's very obvious in this mode - the light starts out bright and then dims a bit. So every time I turn the light off I end up doing a battery check at the same time. Makes me remember to change the battery while the flash mode is still at almost full brightness.
I've noticed on my PB SF that if I hold the power button that it shuts off without going to the constant mode. As it came secondhand on the bike that I am currently riding I didn't get any of the paperwork that one would normally get with it so I don't know if this is usual or not.
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Old 09-11-11, 04:12 PM
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Originally Posted by ThermionicScott View Post
When it's no longer slightly painful to look directly at my CatEye taillight, I know the batteries are on their way out.
Not to long ago when I was at the LBS that I go to most often we had a good laugh at the packaging that the lights came in. It warned not to look into or shine the lights into another person's eyes. Uh, correct me if I'm mistaken, but if one has their lights properly positioned on their bikes aren't they going to shine in the drivers eyes?
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Old 09-11-11, 06:56 PM
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Originally Posted by 2manybikes View Post
It works fine. I never use anything but rechargeable batteries. Saves money if you use your light often, like commuting.
Which rechargeable system do you use? I know that there are several different types. I remember on system that was based on a AAA battery and had sleeves that would increase it from a AAA to a AA to a C and finally to a D.
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Old 09-11-11, 07:18 PM
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That's the set I have. It is eneloops. It came with a charger too. There are all kinds of eneloop based sets on Amazon.

I think that's it, but only AA's go in to the c and d shells. No different cells for AAA. It's great anyway.
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Old 09-12-11, 08:46 AM
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Originally Posted by no1mad View Post
I don't know the answer (but from the posts others do ), but that is why I still have my reflector on the seat post, the Cherrybomb on the rack has a reflector, and the next one will probably have one as well... most likely this Cateye.
Radbot has a reflector. Since Pennsylvania law does not say that a rear light replaces the requirement for a reflector, it's nice to have a belt/suspenders solution.
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Old 09-12-11, 09:02 AM
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Originally Posted by Digital_Cowboy View Post
Not to long ago when I was at the LBS that I go to most often we had a good laugh at the packaging that the lights came in. It warned not to look into or shine the lights into another person's eyes. Uh, correct me if I'm mistaken, but if one has their lights properly positioned on their bikes aren't they going to shine in the drivers eyes?
Sure, but hopefully they're more than a yard away.
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Originally Posted by noglider
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Old 10-02-11, 06:03 PM
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Originally Posted by 2manybikes View Post
Both, it depends.

The Radbot light is so bright that it looks OK even when the batteries are almost dead. When the batteries are almost gone, mine shuts off over a bump once in a while. New batteries and it's fine. If yours start shutting off on a bump don't worry about the light, just put in new batteries. I use rechargeable batteries and have a very nice charger and an excellent battery tester. That's how I know the low batteries cause it to shut off.I just carry an extra light. Now I know to recharge the batteries before they get very low. The planet bike super flash opens with a coin in just a second, so it's convenient to just carry extra batteries. The Radbot needs a screwdriver to change the batteries. Not so nice on the road, That's why I often carry an extra light.
Well, my Planet Bike Super Flash started to shut off by itself when riding (not when stationary). I put in some fresh AAAs, and I'll keep my eye on it on tomorrow's commute. Thanks.

Last edited by Easy Peasy; 10-03-11 at 06:19 PM.
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Old 10-02-11, 07:42 PM
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My original Superflash would dim. My Superflash Turbo, as I discovered and posted about recently, shuts itself off. I didn't notice much dimming before hand but that only means that I didn't notice it. New batteries fixed it right up.
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Old 10-03-11, 07:43 AM
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If you are riding in the codl expect the cold to give you the same problems. As it gets close to freezing the batteries will get weak and shut off the light too. When they get warm again the batteries will work for a while , until cold again. I have had good results putting a light under my jacket to warm up batteries, for another run intill they get cold again. Of course the air temp determines how long it will go untill cold again.
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Old 10-04-11, 08:26 PM
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Originally Posted by Easy Peasy View Post
Well, my Planet Bike Super Flash started to shut off by itself when riding (not when stationary). I put in some fresh AAAs, and I'll keep my eye on it on tomorrow's commute. Thanks.
So far the fresh batteries solved the problem. I commuted in the rain, about 50 degrees this morning, and returned home in the 50s, and no problems with it shutting off.
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