12V batteries with BMS?

[InkTheWall]

I'm looking for a 12V battery to run lights on my bike. The reason for needing 12V is there are other accessories like cameras, handlebar heaters etc. that I want to run as well.

I wanted to use off-the-shelf batteries that are easy to get and have a convenient charger. I was going to use Milwaukee M12 batteries, but I found out they don't have any built in protection or management system. That means I will probably kill them by over-discharging them. Apparently most 18V tool batteries do, but I think 18V will be too much voltage.

I looked into standalone circuits to prevent over-discharge and all of them are too big and expensive.

Are there any other sources of 12V batteries that have built in discharge protection? I looked into RC car batteries, which are available in 3s/11.1V, but they have the same problem, except worse because LiPo batteries have a reputation for catching on fire as it is. If I made a holder for three 18650s, could I use 3 protected 18650s in series just like they were AAs?

 

[sbj]

Yes, that would work in principle.
But you should rethink or recalculate your power requirements.

A bright LED bicycle light alone needs around 4 - 6 18650 cells for a few hours of operation. A handlebar heater will probably consume four times that? Then you would need around 30 cells!

I know how unpleasant it is now in winter, when temperatures are close to freezing and your hands get cold very quickly when you ride your bike, even if you are wearing gloves. But I think it is impossible to power the handlebar heater for a longer period of time, e.g. more than an hour, using a small battery pack.

 

[InkTheWall]

A normal M12 battery, which is actually three 18650s in series, has about 30 Watt-hours (3Ah * ~10V). The bigger ones have 60.

Most LEDs are about 3 Watts, which should last 10 to 20 hours by itself .

Grip heaters are 30 to 60W which will only last an hour or two, but that's enough if I can just swap batteries.

 

[bluflaam777]

30w probably won't be felt in 'actual' cold conditions. 60w is more realistic.
12v boat/rv batteries will last longer than li-ion cells.
Just find a deep cycle marine battery and be done with it. Recharge it when you get home, use it when out and about.

 

[Hooked on Fenix]

A normal M12 battery, which is actually three 18650s in series, has about 30 Watt-hours (3Ah * ~10V). The bigger ones have 60.

Most LEDs are about 3 Watts, which should last 10 to 20 hours by itself .

Grip heaters are 30 to 60W which will only last an hour or two, but that's enough if I can just swap batteries.

Actually, Milwaukee 12 volt M12 3 amp battery is 36 watt hours, 6 amp is 72 watt hours. I have both.

 

[InkTheWall]

The batteries aren't really 12V; they are nominally 11.1v batteries and only called 12V for marketing reasons. Actual Watt-hours depends on a few factors but 36W from a 3Ah M12 is probably unrealistic and it's probably closer to 25 or 30.

 

[Macgravy]

The deep discharge marine battery is in actuality about the only choice, unless you want to go with heated gloves, jacket, pants with their own batteries. The marine batteries are mostly lead acid...that equals heavy. The other battery is LiFEPO4 for lithium Iron Phosphate. They are very light when compared to any same size lead acid. They are much better than Lipo and even Lion. They are safer too. I just did a quick search on lifepo4 and found a skinny one thinking that you might like it because of the bike installation. But there are many others. Take a look. Maybe you might be able to use one of these.

Amazon.com

It has a bulit in BMS, 25Ahr. That might be enough for a couple of hours out in the weather. They can be paralleled or you can get a larger one with more capacity. They only cost $$. The link above state 75$. If your a prime member you can get it for 59$

 

[PhotonWrangler]

Yes, that would work in principle.
But you should rethink or recalculate your power requirements.

A bright LED bicycle light alone needs around 4 - 6 18650 cells for a few hours of operation. A handlebar heater will probably consume four times that? Then you would need around 30 cells!

I know how unpleasant it is now in winter, when temperatures are close to freezing and your hands get cold very quickly when you ride your bike, even if you are wearing gloves. But I think it is impossible to power the handlebar heater for a longer period of time, e.g. more than an hour, using a small battery pack.

Heated gloves should be much more efficient than a handlebar heater. All of the heat goes to your skin, not the atmosphere.

 

[aznsx]

Heated gloves should be much more efficient than a handlebar heater. All of the heat goes to your skin, not the atmosphere.

When I rode a motorcycle in very cold conditions (when I was young and more stupid;-), often wearing a snowmobile suit, I wore a nice pair of gloves which kept my hands in pretty good shape. I wish I could recall who made them (I can't locate them at this time), but I bought them at a motorcycle shop. They were insulated and had supple leather outer. They worked pretty dang well, with no power required.

 

[orbital]

+

I'd just use a LiPo,, I have dozen or so in different voltages used in low & high output.

for you, this is $43 in checkout ~ 153Wh & BMS

https://www.litime.com/products/litime-12v-12ah-lifepo4-lithium-battery

 

[Macgravy]

I'm not sure about using a battery with tab terminals on a moving vehicle??? I do not have any experience with that kind of termination. Plus you can get these cheaper at A.com