configuring my own pack. Type of battery cells and where to buy them?

[Joshuaesp]

Hey Forum.

In designing a battery pack, I'm deciding what batteries to try to find and what configuration to use. I have been trying to figure out what max amp for range battery can fit in my old e350 schwinn scooter. Right now i am running a lithium pack i bought years ago in the back basket which does not fit in the bottom battery compartment. I am also running over volted, but it does wheelies unless i put weight forward, because battery is behind the center of gravity. The maximum shape the battery the intended battery compartment can hold is rectangle of 305mm (12 inches)x 118mm (4,75 inches) x 68mm (2,75 inches), so i want to build a pack that is equal too or smaller than that size, including the bms. So I have two questions really, What battery cells, where to suggest purchasing and how to configure them. I actually have a lot of electrical experience and I can figure most of the shape and parallel series stuff out, even the BMS. You tube is very helpful, but my dimensions are unique and I do not see any battery packs for sale with both the 2.75 inch and 4.75 inch limitations on two of the dimensions. I am going to make a battery style spot welder with a solenoid so i will be spot welding and not soldering. One Chinese seller on ebay says he can configure a pack that will fit for $229.00. he says "We can make the battery smaller than that size with a 20A BMS using new G25 2500mAH 8A 3C The battery model is 36V 15Ah (10S6P) build within 60 pieces of G25 cells. The cells are quality" should i copy his specs?. I so not see g25 cells much on the web for sale. i want to choose good cell and know where to purchase the best cells. Im in no rush but really want to hear people opinion. As too my current configuration. Right now I am running a a 36volt 750 watt 16amp pack with 24volt 500 watt brushed controller and and over volted 25v 500 watt motor running at the 36volts. I have uploaded a pic from the web on the type of scooter compartment i am fitting the pack into. Any help appreciated!!!!!!!

 

[harryS]

I think the vendor is selling you lower rated cells, at 2500 maH with 8A peak discharge. Nothing wrong with that, but who makes them?. For safety and reliability, most people would prefer a well known brand name cell, LG, Panasonic. Sony. Samsung. Then you might as well get good ones. He promises 15AH with 6P. The following could do that with 5P.

The Panasonic GA cell is rated for 10A and 3.35 AH. The Samsung 30A cell is rated for 15A discharge and is 3.3AH. LG MJ1 cells are 10A and 3.5AH.

No, I wouldn't know where to get them. Not interested in building batteries.

Is your scooter cavity really 68mm high? That's the height of a bare 18650 cell.

 

[Ebiker01]

What type of welder(brand) are you using ? Looking to get into building ebike pack myself.

 

[Joshuaesp]

I think the vendor is selling you lower rated cells, at 2500 maH with 8A peak discharge. Nothing wrong with that, but who makes them?. For safety and reliability, most people would prefer a well known brand name cell, LG, Panasonic. Sony. Samsung. Then you might as well get good ones. He promises 15AH with 6P. The following could do that with 5P.

The Panasonic GA cell is rated for 10A and 3.35 AH. The Samsung 30A cell is rated for 15A discharge and is 3.3AH. LG MJ1 cells are 10A and 3.5AH.

No, I wouldn't know where to get them. Not interested in building batteries.

Is your scooter cavity really 68mm high? That's the height of a bare 18650 cell.

thanks, this is helpful, especially knowing what cells are better quality--and yes, my scooter cavity is a little under 3 inches high. I was saying 2.75 inch (68mm) to be safe. It measure 3 inches when i do not have the cover on it, but the plastic cover hangs down a bit.

The cavity was designed to hold two 12v 10amp sla lying on their side and they are 2.56 inches high in that position, or 65mm. There was a piece of foam on top of them between them and the cover. I am thinking I cannot go much more than 2.75 inches maybe 5 or 6 mm more max.

I see on line that 1860 cells are 65mm high. and 18.4 diameter. So that means if i have them vertical then my work has to be precise and i have to also wrap them tight. So if I wanted too, with the batteries vertical and if lined up 6 cells in a row. with the total length, i could fit up to 16 cells going the long way, but that would be a little over a 53 volt pack, maybe too many volts for my current controller. in other words if I were not thinking of voltage but just total volume I could fit up to 96 cells in the space.

What is interesting to me is when I first got my current lithium pack which I bought years ago I measured the voltage and it was more like 40 or 41 volts. I did not yet take apart that pack to actually see the design because it is still in my bike. It makes sense to have a 41 volt pack, since since s SLAs when fully charged usually run higher than 36 volt sla pack. 12volt SLA when charged are more like 41.1 volts so a 36 volt controller has to be made to run on at least a max of 43 volts.

In build I think I can do more than 10 in series, but I am of course limited to 6 in parallel unless I was creative in welding nickle pathways. If I do 13sx6p that would be about 43 volt pack.I could also try 14 cells series by 6 parallel for about a 47 volt pack. I think that will work with my controller and that still gives me space for the controller and BMS . I wonder how many amps that pack would be rated at?

The Seller on ebay who can build a cheap 10s6p pack says his pack is 15amps. how do they determine this? if these are 10 amp cells i do not understand how we end up with 15amps?

My scooter initially had SLA's in serries that were only 10 amp total. So that is one question about how to figure out amp rating, which I think influences the range possibilities that i do not understand yet about these packs.

Since by space I am limited maybe to 6 cells parallel so that is a limitation on amps I assume.

One more question if if I make a different number of batteries in serries and higher voltage pack, how will I charge it? Related to this, looking at BMS for sale, they do have some for 14 cells in series and it says the BMS sets the charge at 53 volts to charge the cells, but i think the charger also has to have the right specs?

So can the 2 amp charger (that came with my "36volt pack" that measures more like 42 volts) work with a higher voltage battery pack if I build one? Any ideas for what to use for a charger if I make an oddly voltaged pack like a 47 volt pack?

Also on a website for solar battery banks i think they have programmable bms units? If it is possible it would be ideal to limit the volts I charge too because if I can set my bms to not totally charge fully to 47 volts and just go to say 45 that will make the batteries last through a whole many more cycles. I read that keeping the batteries fully charged at max voltage while sitting around for days hurts the battery packs.

I really appreciate the discussion since think from it I now am starting to understanding this stuff. Going with a longer serried like 14 in a row seems the best way to max out my space. I wish I could increase the amps. I kinda want to increase the range. The worst thing I can do is blow a controller and just buy a bigger one as they are not to much money to buy, but still wanting to research all the issues before I do anything. I would like to use my charger or buy another charger. This is a great learning experience, thanks!!!!!

 

[harryS]

WIth 18650 cells, your standard charger and BMS options are 10S (36V) 13S (48V) and 14S (52V). The charger can go no higher than the max pack voltages, which are 42.0V, 54.6V, and 58.8V for those three packs, but many peopledo like to set it at 80-90% of max.

You could go with odd numbers like 12S, but now you're making it more complicated for yourself. Your controller might either have a hard programmed low voltage cutoff (LVC) or set it based on whether it detects a 36V or 48V pack. So if you pick an odd voltage like 12S, that pack can go down to 36V safely, but the controller might shut off at 40V.

 

[Joshuaesp]

WIth 18650 cells, your standard charger and BMS options are 10S (36V) 13S (48V) and 14S (52V). The charger can go no higher than the max pack voltages, which are 42.0V, 54.6V, and 58.8V for those three packs, but many peopledo like to set it at 80-90% of max.

You could go with odd numbers like 12S, but now you're making it more complicated for yourself. Your controller might either have a hard programmed low voltage cutoff (LVC) or set it based on whether it detects a 36V or 48V pack. So if you pick an odd voltage like 12S, that pack can go down to 36V safely, but the controller might shut off at 40V.

Thanks, this information is really helpful and I think I understand. But I still have a few questions. Earlier you mention some of the cell voltage of the specific brands they are like 3.3 + 3.5 so that is why when I add it up 14 cells and series I get either 46 or 49 volts. So I don't quite understand why the standard 14s they have rated at 52 volts. I just don't understand how the math Works there. Maybe we are just assuming that when they say the voltage of a cell is 3.5 that sometimes when it's being charged it goes up to 3.6 or 3.7 but its average at 50 percent use is 3.5? Also regarding the charger and BMS I still have a question how people limit to 80% or 90%. If one limits the charger to charge at a lower voltage say instead of charging at 58.8 it only charges at 57 , is that how the charging is limited? Or is it limited somehow in the BMS? The reason I ask also is because most BMS has I think our top balancing, meaning they balance the cells when they are fully charged so I wonder if I am limiting the charge through the charger that it will end up that the will not ever really balance and go out of balance. I know they also make type of balancing systems that do bottom balancing which balance when the cells are nearing their lowered discharge limit. at least I know they make those for battery banks in RVs . And that is where I'm getting some of my ideas on running out of a lower voltage from to increase the life cycle of the pack . So those are few questions that arise in my mind. And I think the answer to my question about the charger is I have to buy a new charger because I think these brick chargers only charge at specific voltage from the information you show that makes sense.
. I guess my charger right now charges is it a bit higher than 41 volts and that's the max my current battery can take. and the charger has some kind of sensor that since is when the battery is not taking a charge it as that since is when the battery is not taking a charge it as fast that since is when the battery is not taking a charge it as fast and reaching full capacity and so that's when the Chargers Light changes from red to Green and the charger shuts off. I'm sorry if I'm answering my own questions as I type. what I really need to know here is the question about balancing and then start to make my decision on what I want to build and find more information on where to buy the cells. Thanks for your help Harry I really appreciate it I am enjoying learning about this stuff

 

[harryS]

18650 Lithium cells are half charged at 3.6-3.7V. That's called their nominal voltage. So 10S is 36V, 13S is 48V, and 14S is 52V. THe max allowed charge is 4.2V. Do the math. You get 42.0, 54.6 and 58.8 volts respectively. That's also the charger voltage for a simple charger. People that charge to 80 or 90% have chargers where they set the max voltage to 80% or 90%.

When you hook a charger to a battery, the output voltage will be close to whatever voltage was left on the pack. Like you discharge your 36V pack to 38V. That's what the charger will apply. As the pack charges, the applied voltage rises. At 100%, the charge current will go down to zero. I believe the light turns green when the charger senses no current flows. With chargers that charge to 80/90%, they just stop when the applied voltage rises to 80/90%. The the light goes green. You could almost approximate this with a timer.

You can't go above 4.2V on a cell or you damage it. Neither can you go below 2.5-2.7V. Either case precipitates metal deposits in the electrolyte. If enough deposits form, the cell short circuits, overheats, and could catch fire. That overheats neighboring cells and then your house can burn down. The most recent case in Sydney. That gal loves her ebike though. No house, but she bought a new battery.

The role of a BMS in charging is to watch the cell voltages. It shuts off current flow into the battery when any cell group hits the max voltage of 4.2V, The 100% charger will see the current flow stops and turn green. If your pack is unbalanced, you might have one group at 4.2V and all the rest are at 4.0V. A balance BMS will bleed some voltage off that high cell, which restarts the charging process, and allows the other cells to catch up. It keeps doing this till all cells are even.

Not all BMS have balance functions. You have to look at the specs to be sure. When you charge to 80/90%, you can't balance because none of the cells ever get to 4.2V.

I don't charge to 80%. One time a vendor sold me a 48V battery, but it was really a 52V battery mislabled with a 48V sticker.When I put my 48V charger on it, I was really only charging to 80%. I didn't think the battery was very strong. Well it wasn't, not at 80%. I eventually opened that pack up to see what was wrong,. I counted the cell groups and got 14 instead of 13, Wow.

 

[Joshuaesp]

What type of welder(brand) are you using ? Looking to get into building ebike pack myself.

Im not using a welder brand. I am making my own somewhat like the one on this link. Actually my local junk yard sometimes has 50% off sales and there are car batteries that are 400 CC which I think will work and i will only pay like $14 - $18 for a good used car battery which is what provides the power for the welding. The solenoid I will likely order on line. check out this video

 

[Joshuaesp]

18650 Lithium cells are half charged at 3.6-3.7V. That's called their nominal voltage. So 10S is 36V, 13S is 48V, and 14S is 52V. THe max allowed charge is 4.2V. Do the math. You get 42.0, 54.6 and 58.8 volts respectively. That's also the charger voltage for a simple charger. People that charge to 80 or 90% have chargers where they set the max voltage to 80% or 90%.

When you hook a charger to a battery, the output voltage will be close to whatever voltage was left on the pack. Like you discharge your 36V pack to 38V. That's what the charger will apply. As the pack charges, the applied voltage rises. At 100%, the charge current will go down to zero. I believe the light turns green when the charger senses no current flows. With chargers that charge to 80/90%, they just stop when the applied voltage rises to 80/90%. The the light goes green. You could almost approximate this with a timer.

You can't go above 4.2V on a cell or you damage it. Neither can you go below 2.5-2.7V. Either case precipitates metal deposits in the electrolyte. If enough deposits form, the cell short circuits, overheats, and could catch fire. That overheats neighboring cells and then your house can burn down. The most recent case in Sydney. That gal loves her ebike though. No house, but she bought a new battery.

The role of a BMS in charging is to watch the cell voltages. It shuts off current flow into the battery when any cell group hits the max voltage of 4.2V, The 100% charger will see the current flow stops and turn green. If your pack is unbalanced, you might have one group at 4.2V and all the rest are at 4.0V. A balance BMS will bleed some voltage off that high cell, which restarts the charging process, and allows the other cells to catch up. It keeps doing this till all cells are even.

Not all BMS have balance functions. You have to look at the specs to be sure. When you charge to 80/90%, you can't balance because none of the cells ever get to 4.2V.

I don't charge to 80%. One time a vendor sold me a 48V battery, but it was really a 52V battery mislabled with a 48V sticker.When I put my 48V charger on it, I was really only charging to 80%. I didn't think the battery was very strong. Well it wasn't, not at 80%. I eventually opened that pack up to see what was wrong,. I counted the cell groups and got 14 instead of 13, Wow.

Thanks this helps. I will definitely get a BMS with balancer. What I think I should do with charging is try to buy or create two different chargers one that charges all the way and one that charges to 80 or 90%. that way once in a while i will charge all the way to make sure the cells are balanced. If there is a charger that has a setting for stopping at a certain percent and that setting can be changed then one charger can do both. I will look into that. There is the you tuber video where a guy says he just always charges all the way but then takes his bike for a short ride right after, and then pays attention to his miles rode and ride it for a few days or a week until he is finished draining it and then recharges all the way and repeats the process. so most of the time it is not sitting 100%, but that does not fit my use right now. I might ride to school 2 times a week and have it sitting for all other times. Anyway Thanks again I bet this discussion is probably helpful to others.

 

[tomjasz]

thanks

It would be so much easier to read if you used paragraphs...

 

[tomjasz]

I use JP Welder, and KWeld from endless_sphere. If you use Facebook endless has a page. At least a dozen builders post there. Good leads on safe battery purchases as well. I just got the newest Vruzend battery kits. A very simple method of building without a welder. I’ve blown two Sunnko welders and never again. LiPo batteries can be used two. There’s also a fella in Korea building nice little welders. So far the JP Welder has held up the best, but I’m building Vruzend packs that’ll live in a triangle bag. Two new Sark cases for frame packs with the Baserunner controller in the battery base. Spendy but darn nice.

Get Micah Tolls book on amazon. It’s a must have!

I’m liking these BMS.
https://www.aliexpress.com/item/Dal...691.html?spm=a2g0s.9042311.0.0.53744c4duyBI0t

Always have a spare! Sadly I’m a BMS hoarder...

Your calculations are wonky. Use nominal to calculate battery rating, 10s is 36v, 42v Max. 16s is closer to a 60v battery. My old eyes struggle to read your wild punctuation.

With what I learned I’d recommend not proceeding until you devour Micah’s book. There are LOTS of potential problems. Some of which can be disasterous. I’ve seen plenty Kentucky fried fingers. None here due to following my bench rules.

 

[harryS]

Thomas, I've got a 36V battery (UPP) that is losing about 1/2 volt in three days. It took 1/2 AH to bring it back to max. Does that sound like a leaky BMS to you? I haven't cracked it open yet.

 

[tomjasz]

Thomas, I've got a 36V battery (UPP) that is losing about 1/2 volt in three days. It took 1/2 AH to bring it back to max. Does that sound like a leaky BMS to you? I haven't cracked it open yet.

Hi Harry! How old is the battery? My 4-year-old UPP does that too.

 

[Ebiker01]

I use JP Welder, and KWeld from endless_sphere. If you use Facebook endless has a page. At least a dozen builders post there. Good leads on safe battery purchases as well. I just got the newest Vruzend battery kits. A very simple method of building without a welder. I’ve blown two Sunnko welders and never again. LiPo batteries can be used two. There’s also a fella in Korea building nice little welders. So far the JP Welder has held up the best, but I’m building Vruzend packs that’ll live in a triangle bag. Two new Sark cases for frame packs with the Baserunner controller in the battery base. Spendy but darn nice.

Get Micah Tolls book on amazon. It’s a must have!

I’m liking these BMS.
https://www.aliexpress.com/item/Dal...691.html?spm=a2g0s.9042311.0.0.53744c4duyBI0t

Always have a spare! Sadly I’m a BMS hoarder...

Your calculations are wonky. Use nominal to calculate battery rating, 10s is 36v, 42v Max. 16s is closer to a 60v battery. My old eyes struggle to read your wild punctuation.

With what I learned I’d recommend not proceeding until you devour Micah’s book. There are LOTS of potential problems. Some of which can be disasterous. I’ve seen plenty Kentucky fried fingers. None here due to following my bench rules.

How do you dispose of the older cells ?

 

[tomjasz]

How do you dispose of the older cells ?

At our County recycling center.

 

[harryS]

Hi Harry! How old is the battery? My 4-year-old UPP does that too.

Late 2017 purchase. Paid for GA cells too. I have a BMS coming in. I'll look at it when it arrives.

 

[Joshuaesp]

18650 Lithium cells are half charged at 3.6-3.7V. That's called their nominal voltage. So 10S is 36V, 13S is 48V, and 14S is 52V. THe max allowed charge is 4.2V. Do the math. You get 42.0, 54.6 and 58.8 volts respectively. That's also the charger voltage for a simple charger. People that charge to 80 or 90% have chargers where they set the max voltage to 80% or 90%.

When you hook a charger to a battery, the output voltage will be close to whatever voltage was left on the pack. Like you discharge your 36V pack to 38V. That's what the charger will apply. As the pack charges, the applied voltage rises. At 100%, the charge current will go down to zero. I believe the light turns green when the charger senses no current flows. With chargers that charge to 80/90%, they just stop when the applied voltage rises to 80/90%. The the light goes green. You could almost approximate this with a timer.

You can't go above 4.2V on a cell or you damage it. Neither can you go below 2.5-2.7V. Either case precipitates metal deposits in the electrolyte. If enough deposits form, the cell short circuits, overheats, and could catch fire. That overheats neighboring cells and then your house can burn down. The most recent case in Sydney. That gal loves her ebike though. No house, but she bought a new battery.

The role of a BMS in charging is to watch the cell voltages. It shuts off current flow into the battery when any cell group hits the max voltage of 4.2V, The 100% charger will see the current flow stops and turn green. If your pack is unbalanced, you might have one group at 4.2V and all the rest are at 4.0V. A balance BMS will bleed some voltage off that high cell, which restarts the charging process, and allows the other cells to catch up. It keeps doing this till all cells are even.

Not all BMS have balance functions. You have to look at the specs to be sure. When you charge to 80/90%, you can't balance because none of the cells ever get to 4.2V.

I don't charge to 80%. One time a vendor sold me a 48V battery, but it was really a 52V battery mislabled with a 48V sticker.When I put my 48V charger on it, I was really only charging to 80%. I didn't think the battery was very strong. Well it wasn't, not at 80%. I eventually opened that pack up to see what was wrong,. I counted the cell groups and got 14 instead of 13, Wow.

I really appreciate this help, as i am a newbie, even writing these questions has been a learning exp. Im still a bit unsure how people set their chargers for a max voltage when charging when you say "People that charge to 80 or 90% have chargers where they set the max voltage to 80% or 90%. I mean do they just use the charger for the next smallest group like you did by accident? Also when using on the road on my scooter right now the lithium battery even after running for some times still feels powerful and maintains close to max amps. then near the very end of its capacity the voltage drops. So why would 80% feel not that strong?

Im just deciding what charger to buy when i do this build at 13s to make it last tong. And still trying to find where to buy these cells in builk.

Thanks

 

[Joshuaesp]

I really appreciate this help, as i am a newbie, even writing these questions has been a learning exp. Im still a bit unsure how people set their chargers for a max voltage when charging when you say "People that charge to 80 or 90% have chargers where they set the max voltage to 80% or 90%. I mean do they just use the charger for the next smallest group like you did by accident? Also when using on the road on my scooter right now the lithium battery even after running for some times still feels powerful and maintains close to max amps. then near the very end of its capacity the voltage drops. So why would 80% feel not that strong? maybe you were much lower than 80%?

Im just deciding what charger to buy when i do this build at 13s to make it last tong. And still trying to find where to buy these cells in bulk.

Thanks

 

[tomjasz]

Im just deciding what charger to buy when i do this build at 13s to make it last tong. And still trying to find where to buy these cells in builk.

First part is easy. Satiator charger from ebikes.ca
Battery Bro for a couple of expensive orders, but all genuine cells. Vruzend ships cells, check them out.
There are a couple of long threads on endless_sphere rich in details and reviews. Google is our pal.. boning up on nomenclature and Chinglish translations a plus!