New battery, Building a Pack from Turnigy Hardcase packs

[Ricky_nz]

I decided it was time to build a new pack for my bike and take the old pack off to use for controller development. the battery is a few years old and still quite usable but I want more volts! The old pack is turnigy normal 5Ah 20C packs.

My new pack is being made out of the cheap 4S 5Ah hard case packs.

My first order was for 9 packs to allow for a dud but they are all good . even after a few cycles and a resting period to detect self discharge. I ordered another to bring the total packs up to 10. The 10th pack is also looking good so far.

My plan is to build bricks two of 8S10Ah and one brick of 4S10Ah which should be quite flexible.

I just measured the self discharge from the first 9 packs that sat for well over a month at mid charge and here is the stats.

Self discharge of Turnigy 5Ah hard case cells

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The cell numbers are across the top and the packs are the rows. All values are in delta volts

The voltage measurements were done with a single cellog.
I am unsure of the voltage calibration of the cell log but since the same channel was used both times for each cell the deltas should be good enough

There is the possibility of typos causing errors but the results look reasonably consistent apart from the one cell with zero self discharge.

My plan is to use Molex Minifit Jr connectors rather than JSTs for the balance connectors and then It becomes possible to charge through the connector at reasonable amps across the end terminals and to balance when necessary. The JST balance connectors were the worst thing with my original packs. Any poor connection and you can end up unbalancing your pack... Their pin spacing was too close for corrosion reasons when exposed to rain etc

All the parts are in so time to start building the packs .

Battery Parts

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Hopefully I won't be reporting KFF or worse in the next few days

[Ricky_nz]

To make things easier to handle I put a couple of beads of hot melt glue between the bricks. This helps with their sloped sides and just holds things together until I heat shrink the lot. Using hot melt means easy disassembly if there is a problem with a pack.

I've started wiring the balance connector of the first pack.
I shortened the balance wires slightly but kept them all the same length for equal voltage drop etc. I could have shortened the balance wires more but its easier to have a little length when soldering and putting the heat shrink on.

first pair of cells balance taps

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The numbering on the mini fit connectors didn't match my idea of ideal. It counts down one side and then the other but I wanted to minimise the voltage between each adjacent pins so I started at pin 1 as 0V and alternated top bottom all the way down. increasing separation helps with possible corrosion.

First brick with balance taps done.

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Yes those are safety glasses. Sensible precautions when playing with high current sources and confined spaces.


The first Brick with wiring done. Just needs output connector.

Electrical done for all but output connector

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The red wire that looks like its exiting in the back middle is just an offcut sitting on the bench. the 8GA + and minus exit to the left.
I might run thicker wires for each end of the pack to the balance connector to allow bulk current charging at say 5A but its not really necessary at the moment as I intend to charge all three packs as one on the bike and I don't have any nice wire of an appropriate size at the moment.

The fuse is an 125A 80V electric forklift fuse! Quite cheap compared to some options and I have a datasheet that defines its characteristics for DC.

The fuse will be glued down. I am planning to place a piece of polycarb on top covering everything on some spacers before shrinking the whole lot in 100mm heat shrink. On my older packs I didn't do this and the packs ended up all lumpy at the top which made it hard to stack them.

This was all done with absolutely no sparks!


I'm sure other cat owners will appreciate how annoying it is when the cat wants to play and you are playing with fire (Well lipo anyway)

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[Ricky_nz]

Here's the pin out I used for my balance connector.

Balance connector pinout

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These connectors have surprisingly good current ratings for quite a compact connector if you use the correct crimps in the plug.
They specify lower currents for all positions used but for just using the first and last pins for a bulk charge they would be fine at their full 7A rating.

I need to either make an adaptor or solder a lead with a plug onto a cellmon to make checking the pack easy. I also need to make an 8S JST to Minifit JR adaptor for my accucell 8150 which will remain permanently connected to the charger.

[Ricky_nz]

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Built up the second 4 brick pack. I need to get some more glue to hold the connector and fuse in place.

The photo below starts to give an idea of how it will stack up. Each pack will have a piece lexane with stand offs across its top to protect with wires/fuse and then will be shrunk in 100mm heatshrink with the ends flattened while its hot. it worked well for my older pack and kept the water out. The only difference being i need to cut a hole around the balance connector this time and put a bit of silicon around it.

100_3617_stack.jpg (20.88 KiB) Viewed 1075 times

I will stack the 2 packs of 4 bricks as above and then put the 2 brick pack below when needed. This all fits easially in the frame of my specialised hard rock.
Each 4 brick pack is 300Wh.


To attach the packs to the bike I will probably use light weight plastic universal shock absorbing battery mounts.
AKA All weather tape.

universal battery mount

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This stuff is great and applied well it looks pretty tidy and I have had it last for about 1 year through winter and summer riding on my old pack and then it didn't fail suddenly. Plenty of warning and I replaced it before it could fail.

[Ricky_nz]

Just built up the 2p pack (half size)

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I then decided to make the charge adapter to use the connectors I had been using up until recently the red turnigy 4mm bullets.

Spot the difference between these two adapter leads.

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Thats right the connectors are identical but the polarity is different in the red connector!
I'vd had them contribute to a polarity reversal before because of the difference between source and load.
That is the reason for the labels! If you are going to use the red connectors only use them for the batteries themselves to avoid the risk.
Y adapters and the above charge/discharge adapters are risky and when I have more connectors I will change everything over to something better.

[Ricky_nz]

Just thought a few of you might like to know the fuses I used.

They are
RS components 226-0850
which is
Pudenz 157.5701.6121
For the 125A one.
80 V dc
NZ$5.50+GST Each (Approx $5US)

They have other currents. This fuse will handle high currents for significant time as specified at the bottom of its datasheet. I will run a second one depending on the controller I'm using for protection but these 125A ones protect the packs.

It has a datasheet unlike most automotive fuses so you actual can understand how it will react.

pudenz.pdf

(41.96 KiB) Downloaded 38 times

Interestingly some current ratings are $15 and a few are $5, I'm guessing the more common ones.

They stock from 50A to 425A. Just remember to blow quickly you need several times their rated current.

[JimW]

Totally interesting and truly excellent !

Thank you for posting this.

Jim.

[Ricky_nz]

Thans Jim, glad its useful.


A few safety Rules for those building packs:

1) Remove any metal rings or watches before starting!

2) only cut 1 wire at a time!

3) cover any wires or contacts at a different voltage potential that are exposed. temporary use heatshrink etc to avoid accidental shorts. The only exposed copper should be on the wires your are working on now.

4) double check you have the correct wires before bring them into contact. You can measure the voltage between them if you are uncertain. It should be 0V

5) only cut, strip,solder and insulate one balance tap voltage level at a time. Ensure it is fully insulated with heatshrink before moving on.

You should also start with all calls at the same voltage +/- a few 10s of mV. The storage mode on your charger is probably good for this although balanced at full voltage is also ok.

Since all wires in the pack are silicon insulated the likely hood of melting through a wire on accient is rather low but it pays to be careful anyway.

[Ricky_nz]

Finally made a balance adapter to connect to my accucell 8150.
One of the packs is now happily balancing/charging on my accucell right now with no issues .

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I have to keep the current down as the charger is currently connected to a 150W 13.8V meanwell which means I can't quite run the charger at the full 150W out due to losses etc.

I will make a longer balance lead for balancing on the bike but this confirms no silly wiring errors.

I cheated a bit on this lead and reused the JST XH crimps with the wires from some HK extension leads I had surplus. I removed them from the old 6 S housings and fitted them into a 9 position housing and then on the other end I crimped using needle nose pliers the crimps for the Minifit Jr connector.

A bit too many adaptors in the charge output of the accucel but it works and one day I will standardise my connectors.

[Ricky_nz]

Ok, Just finished the beefy series lead. 8AWG with EC5 connectors. I really need a bigger soldering iron for this sort of work but cranking up the temp on my hakko did the job but its tips don't have much thermal mass.

The loop connector is for when one pack is not used.

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This photo has the two large packs fully charged and the small pack at storage level approx 3.8V per cell.
Now I need to make the spacers and glue everything down and heatshrink them.
I'm thinking of cutting a window in the heatshrink of one of the packs so you can see the top through the perspex but I would need to run a bead of silicon around the window to seal it.

Weight wise the Lipo used in this setup is 10 * 528g using hobby kings weight which is 5.28Kg of lipo.
To this the weight of fuses, 8AWG cable, perspex and heatshrink would be added but it will probably total around 5.5Kg at a guess for the entire setup.

[fechter]

Nice. I like the fuses. I'll have to try finding a supplier with those around here.

[jonescg]

If only they made fuses that big for >400V and >300 amps, not the beer-can sized ones we have to use...

[cwah]

What's the benefit about having hard pack compared to soft pack when you have that many lipo?

Wouldn't a big protected box for all the lipo ligther and stronger?

[Ricky_nz]

What's the benefit about having hard pack compared to soft pack when you have that many lipo?

$ per Wh is really good for these hardcase packs . It matters when you have a lot.

Wouldn't a big protected box for all the lipo ligther and stronger?

I'm not sure it would be much lighter. the hard case packs are pretty thin plastic. I wanted to break the packs into the three blocks because I intend to mix and match and use them on 3 different bikes so I haven't bothered with a battery box as such. These should be pretty well protected with the perspex top and heatshrink. They will be in the frame.

I haven't had any issues with soft packs taped together and wrapped in corragated cardboard and heatshrinked.
I'm of the opinion that as long as the pack is well attached to the bike and in the frame the likley hood of impact damage is low and if it occurs somthing major has gone wrong.
These hardcase packs are still pretty resilliant. I have one pack that is not part of my pack build that I dropped from kitchen bench height and there is no major damage , just loosened the join between the plastic and electrically its fine . Might not survive every time but thats good enough for me.

[Ricky_nz]

Nice. I like the fuses. I'll have to try finding a supplier with those around here.

It appears they are also sold under the littlefuse brand by http://www.farnell.com/datasheets/40916.pdf
so should be available from Farnell/element14/newark

[Tommy L]

Very Nice!

Tommy L sends.... \\m//

[fechter]

Mouser has those fuses in stock.
Mouser part# 576-157.5701.6121 $9.05 ea

[mr.electric]

What about this fuse?
125a
dc 450v
bc 2000A
From Toyota gen II prius. I have a few lying around.
I would remove it from the orange housing.

[fechter]

Nice fuse! Bet they're expensive though. I should check my old Honda pack.

[mr.electric]

I am building a pack from 4s hard case packs too. I will add pics soon. I love the way they are durable. You can stack them and use double tape to make a giant brick. They will not be ruined by bouncing around in a bike bag.

[Ricky_nz]

I am building a pack from 4s hard case packs too. I will add pics soon. I love the way they are durable. You can stack them and use double tape to make a giant brick. They will not be ruined by bouncing around in a bike bag.

Yep, definitely convenient. I will be interested to see how you pack comes out.
The way I packed them together is a bit wasteful of space and I suspect mounting the fuse on the end of a block of 4 packs would be better space wise but that wasn't going to happen with the 100mm heatshrink I had and also where I want to put the packs.

[Ricky_nz]

Here is a photo of the top perspex sheet being glued down.

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I'm considering cutting a window in the heat shrink of the best looking pack so the tops of the hardcase packs and wiring are visible but protected by the perspex.

I've heat shrunk all three packs. I'm not too happy about the middle packs heat shrink around the balance connector but I didn't have any spear heat shrink to redo it. Its sealed so water shouldn't get in. I won't seal the discharge lead end fully to allow the pack to breath and any moisture to evaporate out.

All packs heat shrunk

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I still need to trim and glue down the heat shrink flap at the discharge lead end on each pack.
This is pretty much how the packs will sit in the frame of a bike.
Lighter colour heat shrink would have probably been a better choice for in the sun but I never had any issues with black on my old soft packs. My bike is normally parked in the shade.
If I regularly parked in it the sun I would probably paint the pack white.

Overall I'm happy with the way the packs turned out.
There is better ways to combine these hard case packs for the smallest volume but since I am not short of space and my design goal was flexibility for experimenting with different bikes and voltages which required each sub-pack to be stand alone and individually protected.

[Ricky_nz]

I did some testing today and it all looks good. The 8s2p bricks are giving just over 10Ah when I adjust for the incorrect current measurement in my Accucell 8150. Its about 7% out so reads pack capacity low.
The 4s2p pack is about 9.6Ah which I expected because it got the weak cells on purpose.
The cells stay in good balance all the way down.

Another feature of my design was the minimising of un-fused wire lengths. These are kept as short as possible including the balance leads to help prevent any accidental damage causing a short or fire.

Some of the packs I see on the sphere really make me cringe when I see harnesses using the stock connectors of the batteries and relatively long parallel series harnesses and if you add up the amount of un-fused wires in those setups it would be well over a meter, possibly several. . The fuse is often positioned too far away from the cells increasing the risk of spectacular failure, then its all stuffed into a space too small to get abraded etc.
A fuse down the line only limits the current in the everything downstream of it. If there is a short before the fuse I hope you like your batteries cremated .
In each of my packs there is <100mm of unfused High current cable in the +ve side . Sure If I wanted to go overboard I could have fused the + and - but for the common failures the + is sufficient.

[Emoto]

I have one pack that is not part of my pack build that I dropped from kitchen bench height and there is no major damage , just loosened the join between the plastic and electrically its fine . Might not survive every time but thats good enough for me.

Hi ricky im concidering some of these pacs, any chance posting some pic's case opened and end connections.

[Ricky_nz]

Hi ricky im concidering some of these pacs, any chance posting some pic's case opened and end connections.

Unfortunately I don't have any photos of the insides of these hard case packs but they are pretty similar to the other packs in that they have a circuit board on the end linking the cells. Maybe someone else has photos of inside the hard case. From memory the thin edge of the cells is up towards the label side of the hardcase.
When I built my pack I just used the existing wires coming out of the pack. I can provide more details of my wiring if anyone needs that.