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Building a custom battery pack

Old 11-22-20, 11:05 AM
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Building a custom battery pack

Searched but didn't find much. Any advice or suggested links or forums to check out for advice on how to build a custom battery pack for lighting? Would like to increase my battery pack and have a back up on hand. Would like to build an 8.4v pack with 4-6 18650 cells to get 6200+ mah in a waterproof container. Seen some on Amazon but would like some experienced feedback or direction to another forum. Looked in in Candle Power forums but didn't find anything specific. Specific questions at this point:


How well do the generic Amazon battery housings work? Something like this as example

Do those have adequate low voltage protections?

Could I charge directly in the housing or should I look at getting a separate charger to charge each cell directly.

If I go the charger route can I get one to use the much cheaper un protected cells?

Would love to find a housing that has electronics to protect the cells from discharge and use as charging base using unprotected cells and be able to use my current cheap chargers.
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Old 11-22-20, 11:11 AM
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I use these:
$13.82 8.4V 6000mAh Rechargeable 4*18650 Battery Pack - IPX6 waterproof at FastTech - Free Shipping
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Old 11-25-20, 02:14 AM
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Originally Posted by Paniolo View Post
Searched but didn't find much. Any advice or suggested links or forums to check out for advice on how to build a custom battery pack for lighting? Would like to increase my battery pack and have a back up on hand. Would like to build an 8.4v pack with 4-6 18650 cells to get 6200+ mah in a waterproof container.
I wouldn't ever build a pack, and I love soldering things.
Kai do 2/4/6/8 batteries in a rugged rubber pack. They are excellent. Grab a 2 cell for backup.
https://kaidomain.com/bike-lights-and.../battery-packs
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Old 11-25-20, 03:27 PM
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Oh, I wouldn't build one by soldering. Was thinking more of finding a good case with electronics in in the top of the case and then using stand alone cells (4 or 6) inserted in case like you would AA batteries. I would source case, batteries and possibly charger separately. For long rides could then carry 4 back up cells just like carrying 4 extra AA batteries and just drop in case when first ones discharge.

But both the complete packs you both mentioned seem like less hassle and I will look into both of those.

Thanks for the input!
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Old 12-02-20, 10:51 AM
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Originally Posted by Paniolo View Post
Searched but didn't find much. Any advice or suggested links or forums to check out for advice on how to build a custom battery pack for lighting? Would like to increase my battery pack and have a back up on hand. Would like to build an 8.4v pack with 4-6 18650 cells to get 6200+ mah in a waterproof container. Seen some on Amazon but would like some experienced feedback or direction to another forum. Looked in in Candle Power forums but didn't find anything specific. Specific questions at this point:


How well do the generic Amazon battery housings work? Something like this as example

Do those have adequate low voltage protections?

Could I charge directly in the housing or should I look at getting a separate charger to charge each cell directly.

If I go the charger route can I get one to use the much cheaper un protected cells?

Would love to find a housing that has electronics to protect the cells from discharge and use as charging base using unprotected cells and be able to use my current cheap chargers.
I have one of the Trustfire 4-cell holders. It works but I don't use mine on the frame of the bike. I use mine to power a helmet light and put the pack in my hydration backpack. I've heard of people using them on the frame. Some have complained that if you hit a big bump that the lamp might can go out ( if the batteries move too much ) Never had any problems myself.

Not sure if the circuit inside the case has a low voltage protection but likely it does. I use mine with unprotected batteries but I rarely ride more than a couple hours at night. Regardless, you want to take the top off the case after you are done riding so the circuit inside the battery for the USB attachment doesn't discharge and kill the batteries while being stored. Yes you charge with a regular battery pack charger but better to use a separate 4-bay cell charger so all cells get charged to their maximum levels. I believe there is a 6-cell version but you might have to search a bit to find one. That said if you have the 4-cell version you can always carry two extra cells along and if the 4 cells start to get too low you can take them out and operate on just two cells ( when in series ) It will work with just two cells, just not as long of course.

Now if you wanted to be extra safe and yet save a few $$ you could buy 2 unprotected cells and 2 protected cells. Put one protected cell in series with one unprotected cell ( one on each side ) and should provide an extra bit of voltage cutoff protection. I buy my loose brand name cells from Orbtronic ( based in Fla. USA ) good prices on the brand name cells and quick shipping. ( my choice was the LG MJ-1 3500mAh unprotected cells.
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Old 12-03-20, 03:48 PM
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Originally Posted by 01 CAt Man Do View Post
I have one of the Trustfire 4-cell holders. It works but I don't use mine on the frame of the bike. I use mine to power a helmet light and put the pack in my hydration backpack. I've heard of people using them on the frame. Some have complained that if you hit a big bump that the lamp might can go out ( if the batteries move too much ) Never had any problems myself.

Not sure if the circuit inside the case has a low voltage protection but likely it does. I use mine with unprotected batteries but I rarely ride more than a couple hours at night. Regardless, you want to take the top off the case after you are done riding so the circuit inside the battery for the USB attachment doesn't discharge and kill the batteries while being stored. Yes you charge with a regular battery pack charger but better to use a separate 4-bay cell charger so all cells get charged to their maximum levels. I believe there is a 6-cell version but you might have to search a bit to find one. That said if you have the 4-cell version you can always carry two extra cells along and if the 4 cells start to get too low you can take them out and operate on just two cells ( when in series ) It will work with just two cells, just not as long of course.

Now if you wanted to be extra safe and yet save a few $$ you could buy 2 unprotected cells and 2 protected cells. Put one protected cell in series with one unprotected cell ( one on each side ) and should provide an extra bit of voltage cutoff protection. I buy my loose brand name cells from Orbtronic ( based in Fla. USA ) good prices on the brand name cells and quick shipping. ( my choice was the LG MJ-1 3500mAh unprotected cells.
Thanks for the real world review! Exactly what I would like to do, get much higher capacity and quality along with ability to just replace cells as they go bad. I like having a component approach for case, batteries and charger allowing you to build a much safer, higher quality battery with 2-3x the capacity and run time. For use on my road bike bars would like to frame mount the battery, so road shocks or bumps causing power interruption/ shut down would be a problem.

Will probably wait till next season as I just ordered one of the cheap Chinese premade packs referenced above that claims like 8400 mah and ipx8 water protection. Though price was higher due to US battery postage surcharge, final price in the low $20 range. The original that came with my light is still going strong and charges last about 2.5 hours and the one I ordered will be on a back up light. otoh maybe this can be a winter project!

Last edited by Paniolo; 12-03-20 at 03:49 PM. Reason: clarification
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Old 12-05-20, 04:38 AM
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Originally Posted by Paniolo View Post
Thanks for the real world review! Exactly what I would like to do, get much higher capacity and quality along with ability to just replace cells as they go bad. I like having a component approach for case, batteries and charger allowing you to build a much safer, higher quality battery with 2-3x the capacity and run time. For use on my road bike bars would like to frame mount the battery, so road shocks or bumps causing power interruption/ shut down would be a problem.

Will probably wait till next season as I just ordered one of the cheap Chinese premade packs referenced above that claims like 8400 mah and ipx8 water protection. Though price was higher due to US battery postage surcharge, final price in the low $20 range. The original that came with my light is still going strong and charges last about 2.5 hours and the one I ordered will be on a back up light. otoh maybe this can be a winter project!
Talk to VegasTriker . He uses the same 4-cell Trustfire cell holder as me although he likely mounts his to his frame. He should be able to give you a better idea of how the cell holder works while mounted to a frame.
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Old 01-04-21, 02:27 AM
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18650's are used as back up for lots of devices now but I have always been put off by the cost to make up a big enough bank. I find that lead acid although heavy is more cost effective.
I am working on a bike trailer to tow two old car batteries, that still have life. Its surprising how long they last drawing about 12 amps.
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Old 01-04-21, 03:26 AM
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Originally Posted by Swarf View Post
I am working on a bike trailer to tow two old car batteries, that still have life.
That would make an excellent training setup.
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Old 01-04-21, 10:30 AM
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Originally Posted by znomit View Post
That would make an excellent training setup.
but imagine the brakes that would be required to stop that trailer quickly! Definitely not something for the hilly places!

Steve in Peoria
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Old 01-05-21, 04:54 AM
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Brakes

Originally Posted by steelbikeguy View Post
but imagine the brakes that would be required to stop that trailer quickly! Definitely not something for the hilly places!

Steve in Peoria
Yes Steve, Thanks for the thought., I was thinking about that one, especially in the rain.
If I made the drive fixed (no freewheel) I would have the solution, Motor overrun.. but couldn't then pedal it.
If I found a freewheel that locked the problem would be solved. Any Ideas ??
My aim is to have a sort of mobility machine for the elderly with arthritic knees, like me. !!
Chris.
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Old 01-05-21, 07:41 AM
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Originally Posted by Swarf View Post
Yes Steve, Thanks for the thought., I was thinking about that one, especially in the rain.
If I made the drive fixed (no freewheel) I would have the solution, Motor overrun.. but couldn't then pedal it.
If I found a freewheel that locked the problem would be solved. Any Ideas ??
My aim is to have a sort of mobility machine for the elderly with arthritic knees, like me. !!
Chris.
Upon reflection, dragging a couple of car batteries around is probably less weight than a person, and tandems manage to stop. However, a trailer will be pushing the bike sideways if you aren't aligned in the same direction. Not sure how much difference it makes, but it's something to think about.

I'd be inclined to go with a more modern battery technology. Battery charging is always the dangerous part of working with batteries. I used to work at a place that built large ni-cad battery packs for aerospace, and we treated them like they were dynamite whenever they were charged. NiMH batteries are safer to charge than lithium ion batteries and are lighter than lead-acid or ni-cad batteries. I'm not sure if they are cheaper than lithium ion, and they will certainly be more expensive than lead-acid.
Generally, it's not bad to repurpose something that is already in production. Maybe use some battery modules made for power tools?

Steve in Peoria
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Old 01-11-21, 04:46 AM
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The EndlessSphere guys live this topic. Check them out.
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