My battery builds

Batteries, Chargers, and Battery Management Systems.
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EbikeAus
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My battery builds

Post by EbikeAus » Mar 16, 2018 5:37 am

Hey all,
Starting this thread to document some battery builds planned and already completed.

My packs will be built using recycled high drain power tool 18650 cells, as I have access to large quantities of near new cells, including Samsung 25R & 30Q, LG HE2, and more.

I've already built 2 packs so far one 36 volt 10s4p Sony VTC6 and recently a 48 volt 14s 4p using 30Qs which I'm using daily on my 48V 1000 watt rear hub mtb conversion. I'm getting around 25 km of mostly hill climbing rides from this pack.

I also have a few 4 AH 58v AEG lawn mower/ chainsaw packs with faulty bms I'd like to use as back up packs for longer rides.

I'll add some photos soon

SlowCo
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Re: My battery builds

Post by SlowCo » Mar 16, 2018 7:58 am

Maybe this is helpful?:
https://endless-sphere.com/forums/viewt ... 14&t=84412

I hope you document your builds here with photo's for others to follow. Good luck!

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Re: My battery builds

Post by EbikeAus » Mar 16, 2018 8:35 pm

Thanks for the link SlowCo, I'm definitely open to advice, critique etc.

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Re: My battery builds

Post by EbikeAus » Mar 18, 2018 5:46 am

Think I've finally worked out the photo thing

Here are some photos of the 14s 4p 30Q pack I recently built. I also added anti spark XT90, fuel guage and on/ off switch.

It's going great!

Image

Image

Image
Last edited by EbikeAus on Mar 20, 2018 5:51 pm, edited 1 time in total.

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Re: My battery builds

Post by EbikeAus » Mar 19, 2018 5:52 am

I have a few of these AEG 58V packs, in the past I've stripped them down for the cells, which have all tested perfectly and have had as new stated capacity.

I reconfigured one to 4s 7p which is making a fantastic power bank for charging my phone/ tablet etc.

The cells have also been in perfect balance. I can only assume the BMS has failed. Out of the 7 packs I have had so far all capacity indicator lights have not worked, except for the one pictured below.

I think these may be marketed as Echo brand in some parts of the world, they look very similar at least.

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Image

Image

Now that I have a 48v ebike they have caught my attention in a new way.

These are the cells inside in 14s 2p configuration. They are 2100 mah 20 amp 18650

Image

My question is could one of these packs be used as a back up to get me home etc?

The amp rating seems adequate but just wondering if it's too much to ask of two cells in parallel??

Probably should add that the bike I'm talking about is a 1000 watt 48v ebay rear hub mtb conversion.

I'd love to hear your thoughts :)

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Re: My battery builds

Post by EbikeAus » Mar 21, 2018 12:04 pm


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fechter
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Re: My battery builds

Post by fechter » Mar 21, 2018 2:04 pm

I know Luna Cycle has a little pack that would be something like that. Voltage sag will be sort of an issue even if the cells survive.

Question: what gauge of wire did you use to connect the cells to the bus bar? Have you ever tried testing one by shorting to see if the wire will actually fuse?
"One test is worth a thousand opinions"

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Re: My battery builds

Post by EbikeAus » Mar 21, 2018 7:15 pm

Thanks for the reply. :)

Yes, I thought this could be an issue. I would only use it to get home...with lots of pedalling :lol:
I ran out of juice a few kms from home the other day. Not fun!

Regarding the fuse wire:
It's rated at 8 amps but usually blows around 10 amps.
I thought this should be suitable, what do you think?

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fechter
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Re: My battery builds

Post by fechter » Mar 22, 2018 8:12 am

10A blow should be good for most cells. What kind of wire is it?

I guess the other thought was you could measure the voltage drop across the wire under a typical load to see if it is significant. As long as they don't get hot, it's a good sign.
"One test is worth a thousand opinions"

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Re: My battery builds

Post by Willow » Mar 22, 2018 3:32 pm

Getting the most draw, least resistance from your cells/pack is generally the aim (especially in an e-bike). You have a massive increase in resistance because of use of the small fuse wires, and as such they will get very hot.... before failing. I know why you have done this, but the pack will only be as good as the weakest link.... and you have dozens of them.

Max current flow is the go.
copper.jpg
copper.jpg (224.29 KiB) Viewed 722 times

EbikeAus
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Re: My battery builds

Post by EbikeAus » Mar 22, 2018 5:01 pm

fechter wrote:
Mar 22, 2018 8:12 am
10A blow should be good for most cells. What kind of wire is it?

I guess the other thought was you could measure the voltage drop across the wire under a typical load to see if it is significant. As long as they don't get hot, it's a good sign.
I believe the wire is tinned copper.

I'll admit that I have limited electrical/ electronic knowledge but have learned a lot recently and every day is a school day :D

The fuse wires and battery in general isn't even getting warm so it must be happy.
My next pack will be 14s5p with 25R, so should be even less stress.

The beauty of having the clear heat shrink is that I can clearly see what's going on

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Re: My battery builds

Post by EbikeAus » Mar 23, 2018 4:49 pm

Willow wrote:
Mar 22, 2018 3:32 pm
Getting the most draw, least resistance from your cells/pack is generally the aim (especially in an e-bike). You have a massive increase in resistance because of use of the small fuse wires, and as such they will get very hot.... before failing. I know why you have done this, but the pack will only be as good as the weakest link.... and you have dozens of them.

Max current flow is the go.

copper.jpg
While I don't disagree with most of what you said. That type of battery is not an option for me to build as I don't have a spot welder.
I like the safety factor of cell level fusing..

I would love to be able to compare my pack to to a more conventional pack but don't have the opportunity atm.
I am very happy with how this pack performs however!

As i said in a previous reply the battery or fuses aren't even getting warm and I'm riding it hard so I don't see any sign of massive resistance at this stage but will keep an eye on it :)

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Re: My battery builds

Post by EbikeAus » Mar 29, 2018 11:53 pm

Image

I've bulk charged my 30Q pack a few times and thought I'd better check cell group voltages.

I poked small holes in the heat shrink over each group to so i can check with a DMM.

Well I'm very happy to report it's looking great!

Parallel group voltages ranged between 3.59 -3.62 for around 50.4 volts before charging.
After a full charge to around 57.5v. Voltages ranged between 4.05 to 4.15

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Re: My battery builds

Post by gpauwels0820 » Apr 01, 2018 11:32 pm

Great battery pack. I plan to use cell level fuses as well, but for now trying to understand battery layouts and BMS rigging. Below is a 12S8P battery pack i am trying to hook up to a BMS. I am though not sure if i have correctly placed each BMW wire. Could use some help in regards to this and if it really matters where i place the wires on the series connections?

-G
2018-04-01_20-22-18 - battery BMS example.jpg
(178.35 KiB) Not downloaded yet

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Willow
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Re: My battery builds

Post by Willow » Apr 02, 2018 12:00 am

EbikeAus wrote:
Mar 29, 2018 11:53 pm
Image

I've bulk charged my 30Q pack a few times and thought I'd better check cell group voltages.

I poked small holes in the heat shrink over each group to so i can check with a DMM.

Well I'm very happy to report it's looking great!

Parallel group voltages ranged between 3.59 -3.62 for around 50.4 volts before charging.
After a full charge to around 57.5v. Voltages ranged between 4.05 to 4.15
Thats far from balanced. Hopefully the BMS will get that down to 0.01V difference after a few cycles.

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Re: My battery builds

Post by EbikeAus » Apr 02, 2018 5:54 am

gpauwels0820 wrote:
Apr 01, 2018 11:32 pm
Great battery pack. I plan to use cell level fuses as well, but for now trying to understand battery layouts and BMS rigging. Below is a 12S8P battery pack i am trying to hook up to a BMS. I am though not sure if i have correctly placed each BMW wire. Could use some help in regards to this and if it really matters where i place the wires on the series connections?

-G
2018-04-01_20-22-18 - battery BMS example.jpg
Thanks! I'm super impressed with the pack so far. Looking forward to building my next. It will be 14s 5p Samsung 25R.
Cell level fusing is the way to go IMO.
As far as the BMS wiring goes, this vid may be helpful

https://youtu.be/u-4mKh1WaLo

I personally don't think it's critical where you connect the wires on series connections, if you are meaning the BMS wires?

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Re: My battery builds

Post by EbikeAus » Apr 02, 2018 6:00 am

Willow wrote:
Apr 02, 2018 12:00 am
EbikeAus wrote:
Mar 29, 2018 11:53 pm
Image

I've bulk charged my 30Q pack a few times and thought I'd better check cell group voltages.

I poked small holes in the heat shrink over each group to so i can check with a DMM.

Well I'm very happy to report it's looking great!

Parallel group voltages ranged between 3.59 -3.62 for around 50.4 volts before charging.
After a full charge to around 57.5v. Voltages ranged between 4.05 to 4.15
Thats far from balanced. Hopefully the BMS will get that down to 0.01V difference after a few cycles.

It's not perfectly balanced no, however these are recycled cells. Also I haven't really fully charged the pack yet, which is where the BMS will balance.
Maybe I should do a few full charges?
If they don't drift further than what they are now I'll be happy!
Love Tasmania BTW. 😁

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Willow
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Re: My battery builds

Post by Willow » Apr 02, 2018 9:10 pm

You have done a neat job and i hope the used cells hold out for you. It does look like some of the solder joints are 'cold' and could become unstable in time.

There are some good cheap spot welders available through forum members. Soldering the cells is problematic because of the heat needed to get a good join... Which translates to cell damage and increased internal resistance. Solder is also a relatively poor conducter. Check out the other (good) battery builds and copy.

In time you will realise that building packs with only new cells and in such a way that maximises current flow is the way to go. Second hand cells are frought with issues due to the fact that each cell has an unknown amount of cycles/abuse, and as such they will each perform differently.

Out of interest measure the entire pack resistance
Vs a single cell and report back. Also, what is the voltage drop (sag) under full load.?

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Re: My battery builds

Post by EbikeAus » Apr 03, 2018 3:22 pm

Willow wrote:
Apr 02, 2018 9:10 pm
You have done a neat job and i hope the used cells hold out for you. It does look like some of the solder joints are 'cold' and could become unstable in time.

There are some good cheap spot welders available through forum members. Soldering the cells is problematic because of the heat needed to get a good join... Which translates to cell damage and increased internal resistance. Solder is also a relatively poor conducter. Check out the other (good) battery builds and copy.

In time you will realise that building packs with only new cells and in such a way that maximises current flow is the way to go. Second hand cells are frought with issues due to the fact that each cell has an unknown amount of cycles/abuse, and as such they will each perform differently.

Out of interest measure the entire pack resistance
Vs a single cell and report back. Also, what is the voltage drop (sag) under full load.?
Thanks!

I have found that solder joints can sometimes look cold in photos when they aren't, but I do make sure the solder flows.
I'm not convinced that soldering cells is that bad if using an appropriate iron and minimal contact is made with cells.
I may look at a SW in the future though.

Due to the fact that I have access to large quantities of near new cells I don't think I'll ever be buying new cells.

Here are around 500 30Qs and some 25Rs I collected recently.

30Qs https://imgur.com/a/o2CLy

These aren't cells from packs at the end of their life, some show very minimal use and I'm able to choose these for my packs.
I will test the IR of cell and pack when I get a chance. Still need to add a wattmeter to my bike.

I can say there is no noticable voltage sag for the first 10-15 kms of a charge and I live on a mountain, so should be noticeable :)

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Willow
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Re: My battery builds

Post by Willow » Apr 03, 2018 6:37 pm

Those cells are indeed decent. But voltage sag is not something you feel... You are talking about pack voltage decreasing as it drains rather than voltage sag, which relates directly to resistance.If you have no gauges to show voltage then you will not be able to determine voltage drop under load. You are obviously running a low power setup so the cells will not have to work very hard anyway... But....

Good luck with it....

Out.

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Re: My battery builds

Post by EbikeAus » Apr 07, 2018 4:45 am

Getting ready for the second battery build. Will be 14s 5p Samsung 25Rs.

I ordered a 14 x 5 holder from Ali but found the cells are loose in it which was disappointing!

Image

So will be using the 5 x 4 holders again, with one trimmed to make the 14 x 5.

I've also ordered a 14s 60 amp bluetooth BMS. It will be interesting to see how it manages recycled cells :)

Pics so far

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Image

If anyone notices one of the positive ring protectors missing, my daughter already pointed that out to me and have since added it :D

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Re: My battery builds

Post by EbikeAus » Apr 09, 2018 11:50 pm

made a start on the 25R pack

Busbars added

Image

And fuses to negative side

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Waiting on bluetooth BMS to arrive

For anyone soldering packs..always be careful not to allow any small particles of solder to enter the gap on the positive end, could lead to a short

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