Greetings! This will be my first forum post here.
I, as many newbies, have big plans to eventually build a nice pack for my long-in-progress-dream-camper-conversion, but as a starter, I figured i'd take on a smaller project:
My father's birthday is coming up soon, he recently bought land and started building stuff about but he does not have the tools necessary, I've spent some money on a few second-hand cordless 18v powertools which work fine but their batteries (NiCad) are lacking. I've tried all the "Revival" techniques in the book and managed to make 1 use-ablebattery out of the 4 bad ones I've collected but I figured, why not try to make a battery pack myself? would be great practice for my future project.
I'm now appealing to you, seasoned 18650 wizards to look over my plan and call out any mistakes, I'm going to spill it all out, what I think can go wrong and what's my approach, hoping that this will be a great learning experience for me and my father will have two functional batteries to work with.
My first "oopsie" came from the choice of powertools, I went with 18v because I figured, more voltage = more power right? ([1]Correct me if I'm wrong, I figure at least half of my statements in this post will be incorrect) I've done the math [2]and figured I would need a 5sXp configuration, but upon looking for a BMS for 5s [3]I've noticed my options are scarce, I then thought, could it be that the 5s configuration is not stable?[4] perhaps something to do with the voltage not being exactly optimal for use?[4]I remember I've read somewhere that achieving 12v with 18650's is awkward[5] because you'd need 3.5sXp, but didn't know anything about 18v.
My second "oopsie" happened when I realized that power tools are, well, power hungry[6] and they can discharge their NiCad/NiMH batteries at 4C[7] (Side note, I have no clue what 4C means) I'm really confused about max draws, but a glimmer of hope came when I remembered high school physics class which taught me that wiring stuff in parallel spreads [8] the load so making the pack 5s3p [9] (Pure guesstimation on the 3p part) could/maybe/should allow the power tools to work in their max draw case? [10].
My plan of action is currently as follows:
Step 1: Aquire 16cheap 18650 batteries with similar capacitiesalready tested by people smarter than mefrom the german Ebay Kleinanzeigen website.[11]
Step 2: Look for a BMS onAmazon[12].
Step 2.5: Wonder why BMS boards have this strange "A" rating and what does it mean. (Image 1)
Step 2.78: Do a fruitless search about this ampere rating of BMS boards, guess that it has something to do with how many you put in parallel, pick the BMS with the most understandable wiring diagram and a bigger "A" rating, because perhaps it'simportant. [13]
step 2.99: order this:https://www.amazon.de/dp/B07RM4MMQJ(Not yet ordered, awaiting input from you guys)
Step 3: Solder[14]3 cells together, + to + to+ and - to- to- [15], using some thick-ish copper wire [16],repeat4 more times.
[size=small]Step 4:[size=small][size=small]Solder[/size][/size][size=small][/size][size=small][14]the copper wires from the first +++ set to the first pin of the BMS, from the second + + + set to the 2nd pin of the bms, from the thirds + + + set (Does it have to always be on the + side?[17])... until the last + + + copper wire, which I think may be called a bus bar? [18][/size]
Step 5:Solder[14] the bus bars [18]+ to - to + to - to + to - to + to -, solder the first -and the last + to the BMS, also solder the last + to the + of the battery housing, solder the - of the battery housing down to the BMS accordingly.
Step 6: Apply generous amounts ofSolder [14]to the spot pointed by the redarrows below, hope that's how you short circuit it and it actually helps with the initial power surge [19] (Image 2)[/size]
[size=small][size=small]
[/size][/size]Step 7: Wonder if it was such a good idea to Solder[14]everything without even a single attempt at self-electrocution by making a DIY spot welder from one of the two broken microwaves you have.[20]
Step 7.2: Wonder if the charger from the NiCad batteries is suitable for your use case[21],given that it charges at 18V 2A when my DIY battery should technically reach 21V. [22] (Image 3)
[size=small][/size]
Step 7.47: Wonder if the battery should ever reach 21V [23]since the NiCad batteries provided seem to top off at 18V (Image 4)
[size=small]
Step 7.86: Wonder why there are no power rating stickers on any of the power tools, consider opening one up to learn more about the circuitry but figure that you probably don't have the knowledge to understand how to calculate[23](Would love to know how it's done) if 21V will fry it or even the required knowledge to put it back together.
Step 7.92: Figure that the original charger won't put the cellsover 18v, the tools won't break and you'll get excellent [24]life cycles from these cells since you only charge them to 50% all the time.
Step 7.99: Keep wondering if 2,0 A of charge will be enough to ever charge this battery. (I guess yes, in like 15 hours?)[25]
Step 8: Put everything together, drain the battery pack to 18V and after putting it in a power tool try activating it with a comicallylong stick to see if it works [26]
Step 9: Success?!
Thanks for reading this far! Feel free to replya list pointing at the references I've made to let me know what I'm wrong or right about, I'm open to suggestions for other BMS boards as long as they're from amazon and would ship within the week. (I'm on a schedule, dad's birthday won't come around again for another year). I hope this was the right sub-forum to post in.[/size]
After thought: I realize that before connecting any battery to any other I might want to make sure they give a similar voltage reading, not sure if it's 100% important since they'll be connected to the BMS, but do correct me if I'm wrong.
I have a e-cig that uses 18650 batteries, I'm wondering if I can creatively use it alongside a multimeter to bring all the cells to a similar charge state before starting the soldering work. preferably 3.6V since 3.6*5 is 18
I, as many newbies, have big plans to eventually build a nice pack for my long-in-progress-dream-camper-conversion, but as a starter, I figured i'd take on a smaller project:
My father's birthday is coming up soon, he recently bought land and started building stuff about but he does not have the tools necessary, I've spent some money on a few second-hand cordless 18v powertools which work fine but their batteries (NiCad) are lacking. I've tried all the "Revival" techniques in the book and managed to make 1 use-ablebattery out of the 4 bad ones I've collected but I figured, why not try to make a battery pack myself? would be great practice for my future project.
I'm now appealing to you, seasoned 18650 wizards to look over my plan and call out any mistakes, I'm going to spill it all out, what I think can go wrong and what's my approach, hoping that this will be a great learning experience for me and my father will have two functional batteries to work with.
My first "oopsie" came from the choice of powertools, I went with 18v because I figured, more voltage = more power right? ([1]Correct me if I'm wrong, I figure at least half of my statements in this post will be incorrect) I've done the math [2]and figured I would need a 5sXp configuration, but upon looking for a BMS for 5s [3]I've noticed my options are scarce, I then thought, could it be that the 5s configuration is not stable?[4] perhaps something to do with the voltage not being exactly optimal for use?[4]I remember I've read somewhere that achieving 12v with 18650's is awkward[5] because you'd need 3.5sXp, but didn't know anything about 18v.
My second "oopsie" happened when I realized that power tools are, well, power hungry[6] and they can discharge their NiCad/NiMH batteries at 4C[7] (Side note, I have no clue what 4C means) I'm really confused about max draws, but a glimmer of hope came when I remembered high school physics class which taught me that wiring stuff in parallel spreads [8] the load so making the pack 5s3p [9] (Pure guesstimation on the 3p part) could/maybe/should allow the power tools to work in their max draw case? [10].
My plan of action is currently as follows:
Step 1: Aquire 16cheap 18650 batteries with similar capacitiesalready tested by people smarter than mefrom the german Ebay Kleinanzeigen website.[11]
Step 2: Look for a BMS onAmazon[12].
Step 2.5: Wonder why BMS boards have this strange "A" rating and what does it mean. (Image 1)
Step 2.78: Do a fruitless search about this ampere rating of BMS boards, guess that it has something to do with how many you put in parallel, pick the BMS with the most understandable wiring diagram and a bigger "A" rating, because perhaps it'simportant. [13]
step 2.99: order this:https://www.amazon.de/dp/B07RM4MMQJ(Not yet ordered, awaiting input from you guys)
Step 3: Solder[14]3 cells together, + to + to+ and - to- to- [15], using some thick-ish copper wire [16],repeat4 more times.
[size=small]Step 4:[size=small][size=small]Solder[/size][/size][size=small][/size][size=small][14]the copper wires from the first +++ set to the first pin of the BMS, from the second + + + set to the 2nd pin of the bms, from the thirds + + + set (Does it have to always be on the + side?[17])... until the last + + + copper wire, which I think may be called a bus bar? [18][/size]
Step 5:Solder[14] the bus bars [18]+ to - to + to - to + to - to + to -, solder the first -and the last + to the BMS, also solder the last + to the + of the battery housing, solder the - of the battery housing down to the BMS accordingly.
Step 6: Apply generous amounts ofSolder [14]to the spot pointed by the redarrows below, hope that's how you short circuit it and it actually helps with the initial power surge [19] (Image 2)[/size]
[size=small][size=small]
[/size][/size]Step 7: Wonder if it was such a good idea to Solder[14]everything without even a single attempt at self-electrocution by making a DIY spot welder from one of the two broken microwaves you have.[20]
Step 7.2: Wonder if the charger from the NiCad batteries is suitable for your use case[21],given that it charges at 18V 2A when my DIY battery should technically reach 21V. [22] (Image 3)
[size=small][/size]
Step 7.47: Wonder if the battery should ever reach 21V [23]since the NiCad batteries provided seem to top off at 18V (Image 4)
[size=small]
Step 7.86: Wonder why there are no power rating stickers on any of the power tools, consider opening one up to learn more about the circuitry but figure that you probably don't have the knowledge to understand how to calculate[23](Would love to know how it's done) if 21V will fry it or even the required knowledge to put it back together.
Step 7.92: Figure that the original charger won't put the cellsover 18v, the tools won't break and you'll get excellent [24]life cycles from these cells since you only charge them to 50% all the time.
Step 7.99: Keep wondering if 2,0 A of charge will be enough to ever charge this battery. (I guess yes, in like 15 hours?)[25]
Step 8: Put everything together, drain the battery pack to 18V and after putting it in a power tool try activating it with a comicallylong stick to see if it works [26]
Step 9: Success?!
Thanks for reading this far! Feel free to replya list pointing at the references I've made to let me know what I'm wrong or right about, I'm open to suggestions for other BMS boards as long as they're from amazon and would ship within the week. (I'm on a schedule, dad's birthday won't come around again for another year). I hope this was the right sub-forum to post in.[/size]
After thought: I realize that before connecting any battery to any other I might want to make sure they give a similar voltage reading, not sure if it's 100% important since they'll be connected to the BMS, but do correct me if I'm wrong.
I have a e-cig that uses 18650 batteries, I'm wondering if I can creatively use it alongside a multimeter to bring all the cells to a similar charge state before starting the soldering work. preferably 3.6V since 3.6*5 is 18