Questions about 18650 DIY battery build

[macribs]

So making a 18650 battery, eh?

Well I got to start somewhere, so I might as well try to get a little help with things that are on me mind. I must say I am more then a little intimidated by the task at hand.

1: Starting with the basic, when making cells do I start by making blocks in series or parallel? For me it will be a 22s12p battery. Or maybe less cells if my currency keeps dropping.

2: I don't know if I should skip BMS or not. If I do skip BMS it will make creation of the battery pack a little less daunting, and I will save time on soldering. Do I ever need to balance charge the pack, or can I just charge it all up to say 4,1v?

3: I see different ways of making batteries. Some just use nickel strips and calls it a day. Others feel that nickel alone can cause voltage drop because of heat so the solder on copper wire or silver wire on top of the nickel. Is that overkill, or something worth doing? I am thinking most power possible from the battery, and if that trick will help me get more power out without heating battery it just might be worth it?

4: Choosing a brand and a model seems like a lot of work just to know what separates the brands and models apart. I've been reading up for some days now, but I must say I am a little cooked in the head now. So at the moment I am considering one of these; Sanyo NCR18650GA or Samsung INR-18650-35E. Then there are 20R , 25R and 30Q. Panasonic NCR18650B same as in Tesla, right? Kind of tempted to go with Sanyo or 35E from tumich.
Is there other cells that might give me higher C rate and more fun for repeatedly accelerations etc? Or are any of those from tumich a good choice?

5: Was planning to fit an on-board charger, like an Eaton APR48-3G. Do they have any way to regulate the charging, like a high voltage cutoff or must I personally keep my eye on the charging if I use this without BMS? I got really bad short term memory so putting me in charge of watching the voltage will end in pain and wasted money. How can I control high voltage cutoff without a BMS?

6: I see a lot of people are making pre-charge, I know it is beside the battery thread but for me it got to do with electricity so for me it is in the same alley. What does a pre-charge do? And should I use it?

7: Do people usually by a bit more cells then what they are building, to count for bad cells, bad welds, bad welder etc? I will use some recycled cells for trial and error on the spot welding. I mean for 264 cell pack how many could be bad - like 1-2% extra should be sufficient?


Forgot to mention that I got a QS 205, and I plan to pump 12-14 kw peak into that hub. The reason I decided to go 22s12p was to give each cell an easier life and get better C rate.



Some phrases might be worded wrongly, if in doubt you should assume I have no clue as to this topic. If I am mixing up words, thinking of this the wrong way or in any way don't make sense to you, let me know and I will try to explain. But I am in way over my head here

 

[Syonyk]

I must say I am more then a little intimidated by the task at hand.

That's a good start. It's not particularly trivial, and screwing up will, at minimum, get your attention, and at maximum, burn down whatever structure you're building or charging the pack in.

1: Starting with the basic, when making cells do I start by making blocks in series or parallel? For me it will be a 22s12p battery. Or maybe less cells if my currency keeps dropping.

With most modern battery types, you build parallel groups and then string those groups in series. The reason for this is that it makes balancing possible. Your BMS will have a balance wire to each parallel group, and if you don't have a BMS you'll still need to measure each parallel group. There exist some older cell chemistries (spinel LiMn) that supposedly self balance slightly, but the energy density on those is low so they're not commonly used anymore.

Why are you building a battery that huge? With modern cells (3000mAh), that's a 80v nominal, 36Ah pack, for nearly 3kWh of capacity. That's huge, heavy, 100 miles of heavy throttle use, and it's going to be very, very difficult to build as your first pack.

2: I don't know if I should skip BMS or not. If I do skip BMS it will make creation of the battery pack a little less daunting, and I will save time on soldering. Do I ever need to balance charge the pack, or can I just charge it all up to say 4,1v?

Please use a BMS. They offer you several things, all important:
- Balance charging. The BMS should balance the pack when charged, which is important for longevity and maximal useful energy.
- High voltage cutoff. If a parallel group of cells is overcharged, the BMS should stop charging the pack and throw an error.
- Low voltage cutoff. If, during discharge, a parallel group hits the low voltage cutoff, the BMS should disconnect the battery to prevent dragging cell voltages below safe levels. On most large packs, the swing from fully charged to fully empty is greater than the voltage of a single cell group, so you can end up with a bank of cells at or below 0v without triggering the bulk pack cutoff. This is bad.

If you have a BMS, it should balance charge each time you charge.

3: I see different ways of making batteries. Some just use nickel strips and calls it a day. Others feel that nickel alone can cause voltage drop because of heat so the solder on copper wire or silver wire on top of the nickel. Is that overkill, or something worth doing? I am thinking most power possible from the battery, and if that trick will help me get more power out without heating battery it just might be worth it?

It depends on how many amps you're going to draw. For a low power pack (250-500W), it doesn't matter much. For a high power pack (1kW+), there are some gains to be had from adding conductor capacity. It's probably overkill for most uses. The battery heating will mostly be from the cell internal resistance.

Is there other cells that might give me higher C rate and more fun for repeatedly accelerations etc? Or are any of those from tumich a good choice?

Your pack at a 1C discharge will be sourcing nearly 3kW. What on earth are you planning to do with this pack?

5: Was planning to fit an on-board charger, like an Eaton APR48-3G. Do they have any way to regulate the charging, like a high voltage cutoff or must I personally keep my eye on the charging if I use this without BMS? I got really bad short term memory so putting me in charge of watching the voltage will end in pain and wasted money. How can I control high voltage cutoff without a BMS?

... again, 3kWh + an onboard charger? What are you doing with this thing?

Generally, the charger is set to output the maximum voltage of the pack, so for your pack you'd set the charger to 90.2v (4.1v/cell) or 92.4v (4.2v/cell). When the charger is done, it just sits at that voltage (many BMSs take a bit once the pack is charged to even everything out). Even without a BMS, it won't overcharge the bulk pack, but without a BMS it could severely overcharge a parallel group if a cell is bad. So use a BMS. Seriously.

6: I see a lot of people are making pre-charge, I know it is beside the battery thread but for me it got to do with electricity so for me it is in the same alley. What does a pre-charge do? And should I use it?

I think you may be referring to a pre-charge resistor or similar, which just prevents arcing when connecting a battery to a controller (inrush current). The precharge resistor allows the capacitors in the controller to charge slowly and equalize the voltage before you make the main contact.

7: Do people usually by a bit more cells then what they are building, to count for bad cells, bad welds, bad welder etc? I will use some recycled cells for trial and error on the spot welding. I mean for 264 cell pack how many could be bad - like 1-2% extra should be sufficient?

I generally pick up a few extra. But I don't think you understand just how large, unwieldy, and complex building a 264 cell pack is going to be. Try some smaller stuff first. I've rebuilt a good number of packs and I don't think I'd be inclined to build a pack like you're proposing (though I'd also have no use for it).

Some phrases might be worded wrongly, if in doubt you should assume I have no clue as to this topic. If I am mixing up words, thinking of this the wrong way or in any way don't make sense to you, let me know and I will try to explain. But I am in way over my head here

Yes, you sort of are... seriously, build some small packs first. And what on earth do you need such an insanely huge and heavy pack for anyway?

 

[macribs]

Thx for your reply. Much obliged.

Well I got a qs 205 v3 laced into a 18" moto rim that I plan to use every last kw from 12-14 kw + peak.The bike is heavy, wheels are heavy and to top it all the rider is really heavy too. So to propel all that weight I figured I needed plenty of battery. For the fun factor and to make sure I don't run out of juice after several red lights run at WOT I wanted to go big with the battery. It is my understanding that if I choose a smaller pack like say 22s6p I would be more likely to get a lower C rate and less current pumped into the fat hub motor. This build is first and foremost about fun - big fun, big speed and endless rapid accelerations.

My choice of 22s12p might be way overkill - I have based it on what I've read others are making. And during summer I will use the bike hard on back roads with little traffic and even less police. So it is all about fun, acceleration and speed 60 mph.

If I can still have my fun with half the number of cells that would be wonderful, cos of the currency drop lately. What do you think, 22s6p worth starting with?

 

[Syonyk]

What sort of frame are you planning to do 60mph on?

Good luck. I have no further advice. I don't think 60mph on anything short of a motorcycle frame is remotely intelligent. Bike frames are simply not designed for that level of abuse.

 

[macribs]

The frame is a sturdy steel frame, Vector frame. Just because it got pedals don't think it is a bicycle 8)

 

[joostj]

I'm building a pack for a QS 205 right now. I've settled on a 22s8p with 30q cells. These cells will do 15-20 amps per cell....giving me about 160 amp max discharge from the battery. For me a larger pack would give me more range, but not necessarily more power since I will be using a 150amp bms.

I've been riding with this motor with a 14s8p 25r pack for several weeks now with a 80 amp max bms (which cuts the power when I up the amps to high in the controller). Even with this pack the bike is a beast. Can't wait to get 80volts and double the amps.

I think the 6p configuration you are suggesting will put you in the 100-120 max amp range...leaving potential power on the table.

 

[macribs]

joostj are your BMS regulating the current? I've thought that was the job for the controller and or the Cycle Analyst. What kind of BMS are you running? And what kind of controller?

 

[joostj]

The current is regulated/limited at many levels. starting with your choice of cell (a 30q or 25r will give you much higher discharge than the 26f I used on my kids bikes).

Next is the BMS which will cut out when exceeding the rating. It feels like a slight hiccup when going full throttle. This is primarily to protect the battery pack making it important to match your pack to the proper bms. This is my biggest complaint about the battery pack I purchased from Lunacycle....they put a 50a continuous / 80a max BMS in a pack capable of discharging well over 120 amps.

Then it goes to the controller where you can set it were-ever you want ( assuming you use a high end controller like Adapptto or with a CA).

It does no good to program 150amp battery / 300 amp phase into your controller if you don't build a battery pack / BMS capable of handling that current.

I bought my BMS from;
http://www.supowerbattery.com/

They have different current versions for a 22s pack to suit your goals

 

[macribs]

Hm all I could find was lifepo BMS, could not see any li ion BMS.

 

[joostj]

Sorry, I gave you the link to there sister site, here is the link direct to the page.

http://www.batterysupports.com/lion-lipo-nbsp-80v-nbsp-22s-c-32_66.html

 

[macribs]

Thx. I keep hearing some horror stories about BMS = Battery Murdering System and how several ES members have had their expensive battery packs destroyed by a faulty BMS. Are those well known vendors with good reputation and well know products?

From what I can read on their site, their BMS looks like it can do all that I would need and then some. Did you get a comprehensive owners manual how to use it and how to set it up, or did you have to figure it out all on your own? Seems I should go for this one, if I so choose: http://www.batterysupports.com/80v-924v-22s-150a-22x-36v-lithium-ion-liion-lipo-battery-bms-p-421.html
The relationship with BMS and current restriction was all new information for me, I had no idea BMS could even handle that.

I think the 6p configuration you are suggesting will put you in the 100-120 max amp range...leaving potential power on the table.

So bigger pack it is then. 8p or 10 p depending on what cell I choose. I guess my first thought of 12p was not that far off. But hey less is sometimes more. At least in terms of weight.

It does no good to program 150amp battery / 300 amp phase into your controller if you don't build a battery pack / BMS capable of handling that current.

So unless I use a hi current Battery/Bms it will be like having a large wide hose and then turn faucet only half way open?

 

[Wheazel]

I would say building a pack is trivial but timeconsuming when there are many cells. As long as you are thinking of what you are doing and isolating the areas you arent working on.
Also work on a nonconductive surface How are you putting the pack together?

I have done a few 18650 packs and tried some different ways of securing the cells. The first method was using 50mm thick ground isolation foam, that i drilled 180 holes in for the 12s15p. (17mm for a snug fit)
This method is good if the pack is used at low current in cold temps. Helps with keeping the pack slightly warmer. Its a very cheap way to make a safe structure, but still a nische and cheap solution.
This pack uses a ping bms that is pretty stupid. Only draws standby current from parallell group 1 in the battery and low voltage cutoff is a total shutdown. SInce I dont charge it very often, I have to supportcharge group 1 now and then.

Next pack was made with welded nickeltabs and the cells glued together for minimum form factor. 12s8p. No bms, uses balancewires and a rc charger. Used as a replacement for an old hobbyking lipopack where a cell died.

My largest pack is the cargobike pack out of 18s26p. 468 cells. These are held together by 18650 spacers bought in bulk. Welding was made easier and more timeefficient by getting 2p nickeltabs. (saved alot of time)
Charged with an eaton arp48 into the adaptto. Very userfriendly setup.

Other than that Ive made a few small 7s6p batteries with bms and 18650 spacers. (bms from bestechpower)

If I would do another pack I would go with spacers, and some extra insulation gasket on the positive end can be peace of mind aswell.
One of the convenient things about the spacers is that the balancewires can be routed inside the pack between the cells and exited on the same location.
If not using an adaptto, I would read up on supower and bestech bmsés and grab an approperiate one.

When it comes to charging a pack with a dedicated charger or just a powersupply, the difference is that the charger will turn off when current goes under a set value.
The powersupply will not, it will just try to charge until no more current will flow into the pack, due to them both being the equal voltage. Then it just stays that way until you disconnect it.
I dont know if this is bad for the pack in any way. Point is that the charge will "regulate" itself regardless of using a charger or powersupply.

 

[Wheazel]

The relationship with BMS and current restriction was all new information for me, I had no idea BMS could even handle that. So unless I use a hi current BMS it will be like having a large hose and then turn faucet only half way open?

Yes, depending on how its made it could possibly get overheated and break, or some fuse wire blows, or it can restrict the power. I havent tested mine above stated limits to know exactly what happens.

 

[joostj]

These high amp BMS's are hard to find. Another option is using the Adaptto BMS which has the benefit of on-board charging as well.

I am using the Adaptto controller but wanted the flexibility of swapping my batteries to other projects easy.

Battery murdering system opinion seems to be going around, but I believe that the pros of having a BMS outweigh the cons.

The BMS will slowly drain the battery over time(6-12 months), so make sure you monitor / charger the pack if left in storage for some time.

Also the BMS will give you full capacity for longer by giving you a balance every charge cycle.

The theory is that the cell quality has come so far that BMS is not necessary to keep a balance, but I would rather be safe than sorry.

I'm waiting for someone to do a 1000 cycle test with and without a BMS to see the effect it has over time.

I don't know much about this company. I've opened it up and it looks very well made, but still haven't installed it yet.

Everything you need to know to install it is right on the page link of your last post. I just built two battery packs with 50a BMS for my kids last week. The BMS I used involved some soldering to the board. This one from SuPower has the wires already soldered making it a simpler install.

You are right about the hose example. If you put a low amp BMS in your battery build it will become a choke point for the current you want going to the motor

 

[macribs]

Also work on a nonconductive surface How are you putting the pack together?

I am ordering some fiberglass sheets, to use as isolators. Big one for use on the work bench when working and small ones to use between different groups of cells in order to prevent shorting. I will be spot welding using nickel strips, and it seems I might even need to solder some copper wire or silver wire on top of that nickel. Not sat on how I will space the batteries, it depends on some other ideas for heating/cooling of pack. But I think I will use glue, but I might need to do a "battery jig" of some sort to assure correct and alike spacing between cells. I will use cardboard insulators, the ones that glue on to the battery.

These high amp BMS's are hard to find. Another option is using the Adaptto BMS which has the benefit of on-board charging as well.

I've been set on the Adaptto, but not so sure anymore. After the currency madness I will pay almost 30% more then last summer. And we are talking a 1.000 $ controller. And it has that fugly outdated screen. I think I will end up with Sabvaton. Save me some change and put out as much power as the Adaptto. But yes that also means look elsewhere for BMS, and yes I was kind of hooked on that adaptto BMS and how easy they have done it. Then the NOk took a dive.

Btw, the adaptto uses those big chunky coils, do I need anything like that for this BMS or can I just plug in the Eaton PSU?
http://www.batterysupports.com/80v-924v-22s-150a-22x-36v-lithium-ion-liion-lipo-battery-bms-p-421.html

 

[macribs]

I am looking for a charger and came across various 700 w chargers. I know the eaton will manage close to 2 kw so charging time should be much faster. But the eaton is high priced also, and other chargers I can pick up for about 15$ and upwards. Can I use two of them and reduce charging time by two?
How long will it take to charge 22s10p with a single 700w charger.

 

[joostj]

The Eaton is a Power Supply, not a charger. A power supply will only work if you go the Adapptto / Coil route.

I purchased this one initially;
http://www.batterysupports.com/924v-81v-80v-3a-lithium-ion-lipo-battery-charger-22s-22x-36v-p-411.html

But have since invested in a high voltage cycle Satiator (up to 8amp charge). They sell some at a discount that have not passed the waterproof test.

If there are two items in the ebike world that are 'must have', It's the JP spot welder and the new high voltage Cycle Satiator.

I still only charge at a 5 amp rate. I don't see the value in going faster, especially when I only need to charge once a day overnight.

I typically will allow for 4-6 hours to charge a 24 amp/hr pack, plus maybe some balance time. I leave it overnight...something I would not do with a PSU charger or Lipos.

 

[macribs]

Thx for clearing that up for me. Glad I didn't put in the order for the PSU yet.

I love when people get really emotional about a product, that usually means their expectations was met and then some.
That charger from Grin sounds like you are very pleased. I will have to check with them what shipping will be like. Maybe I can stretch the budget.

 

[joostj]

With Grin's charger I can now charge both my boys bikes at 48v. My tangent drive at 52v....my 80v 22s NYX(QS 205) and my upcoming LMX project which will be 72v. If I had to buy individual charger for all these it would add needless $$$ and complexity. Not to mention you can do 90% charges if you want to extend battery pack life.

 

[Syonyk]

...the new high voltage Cycle Satiator.

Is this the $300 one that's currently on their site, or a different higher voltage one?

 

[joostj]

They have a new high voltage one. the original will only get you to about 14s level.

Contact them about the ones that failed the waterproof certification for a good discount.

I always charge in a dry garage, so no need for the waterproof for me.

 

[Syonyk]

Link to the high voltage one? I'd been interested in one, but I wanted something that could charge a slightly higher voltage pack for future expansion.

//EDIT: Never mind, found it! Awesome! *goes to order*

 

[joostj]

Great, you won't regret it!

 

[Lurkin]

Macribs, have you considered deciding on your voltage, then breaking your pack down in P? That way, if you pick up another bike (which will happen) you can use it on that two?

This also means construction wise, you do not need to make the whole thing at once and you could use a reduced pack for reduced weight, speedy runs?

As for BMS, I found Bestech was the supplier I came across frequently on here. As I'm actually doing the same thing as you, rather than repeat it all here, feel free to have a looksee at https://endless-sphere.com/forums/viewtopic.php?f=14&t=75415 ...

 

[macribs]

I am currently looking/digging into the mysterious path of chargers. So any thing you feel I should know about is welcome. I do know of the one from Grin and the SUpower. Feel free to name drop, or paste links.

@Lurkin thx for you suggestion, dually noted. I was gonna make batteries into "compartments" anyway with fiberglass panel as insulators. Now even a better reason to do that. I will give it more thought