Battery diagrams for small 12 V light

[MarkJohnston]

Hi,

I just need someone to look over this very crude diagram if at all possible and tell me if this is feasible build if at all possible. This would be my first battery. I am starting small and hoping there is less chance of something blowing up dealing with smaller voltages, amps, watts, etc. I know it's still dangerous and taking precautions, hence this post. It looks right to me so far, I do see a pattern in all this which usually means it's going to work. this is a 3s3p battery I believe with a BMS that has a balance charge. The BMS is right here. My plan eventually is to build a large 100 V 100 amp 18650 battery and retro fit a motor and other electronics onto a motorcycle chassis. Thank you for helping me out in advance. here is the link to BMS.

Also I read on the link that perhaps you don't need a seperate charge line for this particular BMS or should I include one for saftey's sake with a fuse? thanks again

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[lnanek]

That doesn't look correct, no. Charger + and - go on these pads on the BMS:

Charger doesn't connect to the battery at all, which would circumvent the BMS' protections.

Maybe you should make a 3s1p battery first following the OEM diagram exactly. After that, making it 3s2p is as simple as, for every cell, adding another cell that connects plus to plus and minus to minus of the existing cell.

 

[docw009]

Diagram is wrong. This one is better, but it's also wrong because it's unsafe to glue cells like this, The green PVC on these cells melts at hair dryer temperatures, because it's shrink wrap. It also scratches pretty easily. If you happen to bridge between two layers, a cell will short circuit, heat up and maybe catch on fire.



Use cell holders.| And this pic is wrong too, because you need washers on the positive terminals. You see them in the first picture.


Finally, you can use insulating paper like these, if you don't like the holders. Don't forget the washer. All the extras, like cell holders, washers,and the fishpaper add up to the cost of the battery, but it's all about trying to prevent a fire if the cells short circuit against each other.

Even one cell can burn down your house,

Oh yeah, don't believe those guys who show you on Youtube how they get dead cells and restore them. DO that enough times and one of them will eventually burn up.

 

[From-A-To-B]

Jumping in to say that DocW009's comments are excellent -- including pointing out the ways that manufacturers cut corners to save a dime and dramatically reduce battery safety along the way.

Use cell spaces and paper washers and mimic the designs in the first photo. BMS Negative (often, not always, labeled "B-") goes to battery negative. Charge and discharge positive both typically connect to Pack Positive (+12V), but some BMS's have the positive charge wire run through the BMS, first. Share photos and manuals for your equipment if you have specific questions.

 

[MarkJohnston]

That doesn't look correct, no. Charger + and - go on these pads on the BMS:
View attachment 332812
Charger doesn't connect to the battery at all, which would circumvent the BMS' protections.

Maybe you should make a 3s1p battery first following the OEM diagram exactly. After that, making it 3s2p is as simple as, for every cell, adding another cell that connects plus to plus and minus to m

Diagram is wrong. This one is better, but it's also wrong because it's unsafe to glue cells like this, The green PVC on these cells melts at hair dryer temperatures, because it's shrink wrap. It also scratches pretty easily. If you happen to bridge between two layers, a cell will short circuit, heat up and maybe catch on fire.

View attachment 332838

Use cell holders.| And this pic is wrong too, because you need washers on the positive terminals. You see them in the first picture.
View attachment 332839

Finally, you can use insulating paper like these, if you don't like the holders. Don't forget the washer. All the extras, like cell holders, washers,and the fishpaper add up to the cost of the battery, but it's all about trying to prevent a fire if the cells short circuit against each other.
View attachment 332840
Even one cell can burn down your house,

Oh yeah, don't believe those guys who show you on Youtube how they get dead cells and restore them. DO that enough times and one of them will eventually burn up.

Your right, I dont like the holders. How about electrical tape instead of insulated paper?

 

[MarkJohnston]

That doesn't look correct, no. Charger + and - go on these pads on the BMS:
View attachment 332812
Charger doesn't connect to the battery at all, which would circumvent the BMS' protections.

Maybe you should make a 3s1p battery first following the OEM diagram exactly. After that, making it 3s2p is as simple as, for every cell, adding another cell that connects plus to plus and minus to minus of the existing cell.

I thought that's what I did, but perhaps its just not a good diagram. Ok, so I need to hook up the charge and discharge spot to the same place.

I hope that doesn't throw a wrench in plans. I have a 12 V internet router adapter I am repurposing for this. I was hoping to directly attach the 12 V straight to this and let the BMS do the balancing. I really don't want to spend any more money on this, all these little packages of bolts, and washers, and other things adds up very quickly! I definitely don't want to dish out a bunch of money for another Li ION charger.

I see all these videos on youtube of these people in India being so resourceful and awesome with minimal resources, they build really cool stuff that seems to work even though it looks ghetto. I am using recycled cells for this project to save money. They have inspired me

 

[MarkJohnston]

Here is the manual

 

[MarkJohnston]

I will be charging the battery outside for the first 100 charges at least. I have a big back yard. I will also test a few discharges outside too first, but I fear charging more than discharging.