Homemade Pack

Batteries, Chargers, and Battery Management Systems.
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adamsavage79   100 W

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Homemade Pack

Post by adamsavage79 » May 12 2018 10:05pm

Question. How easy or hard would it be to build a battery pack, using Headway 38120 screw top cells ?This would get rid of the need for soldering. On paper, it seems quite bit cheaper, vs buying a premade pack. I have a pack that has new and old cells mixed, and defective BMS that tends to kill cells, in the exact same spot. So I could salavage some of the wiring from it, like the XLR plug and the discharge port.

If the BMS comes with simple wiring directions, it looks like it would be a simple process. I could use the existing pack, as a reference point for how the cells should line up. I guess the harder part, would be finding high qaulity Headway cells.

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Re: Homemade Pack

Post by amberwolf » May 12 2018 10:31pm

Well, my personal opinion is that I dont really think there is any such thing, but you can look. ;)

Like most of the LiFePO4 cells out there they are generally low-C-rate cells, so 1C / 2C, with a fair bit of voltage sag when higher loads are applied.

There are at least three different models (not counting the different types of terminals on the ends) that I have seen on ES over the years, with different capacities and perhaps different capabilities.

As for how to build a pack, theres quite a few here on ES. Its fairly simple, compared to cells that dont bolt together. Technically you just make plates of the right shape and size and material to connect the groups together and series the pack, then drill holes in the right places on them, then bolt it all together. Add wires for balance leads to BMS if youre using one, and wires for charge/discharge. Package it up to keep it safe on a ride, etc.

This list of threads includes some pack builds that might help, including the big Headway Pack Builders Thread:
search.php?st=0&sk=t&sd=d&sr=topics&key ... =titleonly

This one lists some bike builds with headway packs, and some headway pack builds
search.php?st=0&sk=t&sd=d&sr=topics&key ... =titleonly



This just finds all the headway threads, which you can look at the titles of to see if any are relevant that arent in the other lists above:
search.php?keywords=headway&terms=all&a ... mit=Search

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adamsavage79   100 W

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Re: Homemade Pack

Post by adamsavage79 » May 12 2018 10:36pm

This website sells the headway cells, and also has plastic holders and conecting plates. This would make it easier. Based on the website it would cost $508.59 for the cells. I would still a BMS. I have a discharging cable and charging cable I can salvage from my 1st pack.

http://www.evassemble.com/index.php?mai ... ucts_id=21

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Re: Homemade Pack

Post by amberwolf » May 12 2018 10:53pm

You might want to look around for EVA / EVAssemble / EV Assemble here on ES; not everybody has had good luck with them. A Michael used to post here (and spam too) for them, so you can look thru those posts to see how their support/etc might be.
memberlist.php?mode=viewprofile&u=15767

search.php?keywords=EVAssemble&terms=al ... mit=Search

THis is a sale thread by them, which indicates some good and some bad--for instance, there is a case where they didnt send the items that were ordered, but rather lower capacity cells instead--they did refund the difference, but it doesnt help if the other cell type was needed.
viewtopic.php?f=31&t=20046&hilit=*Assemble+promise


Note that the page you link says they are 10C cells (120A continuous for a 12Ah cell); I wouldnt believe that. I dont know about the listed 5C charge rate, either.

Heres a post that gives some data:
viewtopic.php?f=14&t=81822&p=1203476&hi ... e#p1203476
and that assumes the internal resistance is actually what they say it is, which is probably lower than reality, possibly significantly.


So whether these will do what youre after will depend on your needs, and how big a pack you can actually fit and carry. The cost you list appears to be for 26 cells, which would either be 26s1p (about 83v full), or 13s2p (about 42v full). The latter makes sense for a 36v ebike.

If you consider them 1C cells, then the latter gives you a 24Ah pack that can do 24A continous, which is more than good enough for most purposes. It could support bursts of higher currents, if needed.
Last edited by amberwolf on May 12 2018 11:00pm, edited 1 time in total.

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Re: Homemade Pack

Post by adamsavage79 » May 12 2018 10:56pm

The cost was for 16 cells, which is the number of cells I have in my old 10ah 48v Battery pack. It also has shipping to Canada, in the cost I listed.

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Re: Homemade Pack

Post by amberwolf » May 12 2018 11:03pm

Ok. 16s1p makes sense for a 48v 12Ah pack, which is probably still ok given that 12A at 48V is still about 500w continous, and stays at 1C for the cells, to keep them cooler and last longer and have less voltage sag.

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adamsavage79   100 W

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Re: Homemade Pack

Post by adamsavage79 » May 12 2018 11:05pm

amberwolf wrote:
May 12 2018 11:03pm
Ok. 16s1p makes sense for a 48v 12Ah pack, which is probably still ok given that 12A at 48V is still about 500w continous, and stays at 1C for the cells, to keep them cooler and last longer and have less voltage sag.
How do make sure you keep the cells @ 1C ?

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Re: Homemade Pack

Post by amberwolf » May 12 2018 11:20pm

1C means 1 x the Ah rating of the cell. So for a 12Ah cell, dont use them at more than 12A, and theyll be at or under 1C.

2C is 2X the Ah rating.

On the site they say they can do 120Ah, which is 10C, which they claim is continous. But at the internal resistance they *actually* have (which is significantly higher than they say it is--which is a bad thing), the cells will waste a lot of power inside them, which heats them up (aging them faster, etc) and means you dont get all the charge in them out to your wheel, either. See the post I linked about that in the previous post.

As an example of how bad the resistance these celsl have is, in this post
viewtopic.php?f=14&t=81601&p=1200890&hi ... y#p1200890
Peter measured around 12-15 milliohm at half-charge (so call it an average) per cell. My entire EIG packs actual resistance (as measured by the Cycle Analyst during use, at all states of charge from full down to empty) is only 38 milliohm, and its 14 cells in series--so each cell is only 2.7 milliohm, or less than half of what he measured for the *full* charge resistance of a single Headway cell.

Mine are not the best cells you can get, either, by far, but theyre pretty good, and they came to me already used, so they mightve been better when they started out.

Anyway, as long as the current you need out of the Headway cells isnt too high, theyll work--but the higher the current you need, the worse the voltage drop will be, and the more heating of the cells will happen.

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adamsavage79   100 W

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Re: Homemade Pack

Post by adamsavage79 » May 12 2018 11:25pm

I have a basic understanding of what you said, but it's just that. Basic. haha. I understand that the faster I go, the more power demand and thus the pack heats up. My old kit would go crazy fast. I was able to get it up to stupid speeds of like 55km/h, which I see now is really bad for the cells.
Last edited by adamsavage79 on May 13 2018 9:18pm, edited 1 time in total.

999zip999   100 GW

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Re: Homemade Pack

Post by 999zip999 » May 13 2018 9:15pm

You need a book.viewtopic.php?f=31&t=87300&hilit=Diy+li ... k#p1274916
Headways can have trouble keeping balance and are big and heavy.

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adamsavage79   100 W

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Re: Homemade Pack

Post by adamsavage79 » May 13 2018 9:20pm

999zip999 wrote:
May 13 2018 9:15pm
You need a book.viewtopic.php?f=31&t=87300&hilit=Diy+li ... k#p1274916
Headways can have trouble keeping balance and are big and heavy.
I don't know what cells I have. This is Ping Battery pack and they are pouch cells. They resemble a cell phone battery.

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Re: Homemade Pack

Post by 999zip999 » May 13 2018 10:45pm

You have info and cross talking through 3 different threads. A ping 48v 15ah has 16s 3 p so three 5ah pouches parallel for 15ah then 16 in series. .Or 48 puches total.
But you have another Thread about that battery This Thread is about you wanting to build a battery for yourself that's why the suggestion for a book for you to study learn read and understand so you can get a leg up on this stuff.

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adamsavage79   100 W

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Re: Homemade Pack

Post by adamsavage79 » May 13 2018 10:49pm

999zip999 wrote:
May 13 2018 10:45pm
You have info and cross talking through 3 different threads. A ping 48v 15ah has 16s 3 p so three 5ah pouches parallel for 15ah then 16 in series. .Or 48 puches total.
But you have another Thread about that battery This Thread is about you wanting to build a battery for yourself that's why the suggestion for a book for you to study learn read and understand so you can get a leg up on this stuff.
Ah ok. I understand now.

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adamsavage79   100 W

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Re: Homemade Pack

Post by adamsavage79 » May 22 2018 5:23pm

I got in touch with a site/store called Total Battery...

I've talked to different reps from Total Battery, via the chat system and I keep getting the run around. The first guy, kept evading my question on the cost, going on about how it's complicated, and how they can catch on fire easily, that they have to spot weld them etc.. Which I'm already well aware of... I understand how the packs are built, but don't have the means, or know how to do it.

The 2nd rep, flat out told me they only do rebuilds and don't do lithium li-ion or LiFePO4 . Yet, the website says it very clear they do... " FOR NEARLY 25 YEARS TOTAL BATTERY HAS BEEN SPECIALIZING IN THE DESIGN AND ASSEMBLY OF SPECIALITY AND CUSTOM BATTERY PACKS.

No matter if your requirement is for a single custom assembly or you require production runs of many thousands of batteries we have the resources and industry contact to facilitate your requirements.

For any custom battery pack or specialty battery please contact us directly."

http://www.totalbattery.com/product/bat ... ssembly-2/

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Re: Homemade Pack

Post by adamsavage79 » May 23 2018 5:37pm

It would seem I can't replace the cell, as I don't know enough about it or where to get a new one, aside from ping. Even then, the way PING made these, it is very tricky remove them and then somehow get the group of them to connect to the square. I attached a picture to show what my pack basically looks like.

I tried going to that battery store, that has some bold claims on it's website, only to be told they don't build batterys and they refuse to deal with Lion batterys, as they are too dangerous.

So it looks like I will be stuck buying a new pack. I'm thinking about going with Golden motor, but not sure. I would like know though, if I can get replacement cells should I get a weak cell. This would extend the life of the battery for maybe another year, or even longer if lucky. Would depend on the health of the rest.
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