Antiscab's NWH10 Prius plugin Lithium conversion

Post up a thread for your EV. Progress pics, description and assorted alliteration
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Antiscab's NWH10 Prius plugin Lithium conversion

Post by gtyler54 » Fri, 23 Jan 2015, 23:41

After working on packs maybe 50+ times I have come to the conclusion that the NHW10 pack has a major problem, like you say, because the air flow is through the height of the pack, i.e. through 7 strings and the top cells get the air that has been heated by the lower cells. the bottom row of strings is wrapped in clear plastic as an afterthought to help with this problem. the self discharge rate increases with temperature sharply and this means that the cells get unbalanced.
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Antiscab's NWH10 Prius plugin Lithium conversion

Post by antiscab » Sat, 24 Jan 2015, 05:10

Simon wrote: Antiscab could it be the stacked arrangement of the battery pack contributing to the heat buildup? Toyota changed their Prius packs to a single layer of cells with the NHW11.


The Lithium battery is stacked - however - there is no airflow within the battery at all - it's too densely packed

I would say it's having no effect really - the issue is the batteries have too much internal resistance

this becomes more apparent in winter, where the battery is not able to put out enough current at a high enough voltage to keep the car happy

The A123 cells should solve the above problem

Matt
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Antiscab's NWH10 Prius plugin Lithium conversion

Post by T1 Terry » Sat, 24 Jan 2015, 12:08

antiscab wrote:
Simon wrote: Antiscab could it be the stacked arrangement of the battery pack contributing to the heat buildup? Toyota changed their Prius packs to a single layer of cells with the NHW11.


The Lithium battery is stacked - however - there is no airflow within the battery at all - it's too densely packed

I would say it's having no effect really - the issue is the batteries have too much internal resistance

this becomes more apparent in winter, where the battery is not able to put out enough current at a high enough voltage to keep the car happy

The A123 cells should solve the above problem

Did these cells always have the high internal resistance, or has this increased as they cycled?

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Antiscab's NWH10 Prius plugin Lithium conversion

Post by antiscab » Sat, 24 Jan 2015, 16:42

T1 Terry wrote:
Did these cells always have the high internal resistance, or has this increased as they cycled?


it's always been the case - and it's very temperature dependent

But it's all relative - for an EV these batteries would be fine (where continuous discharge is below 1C), but in a hybrid, where the continuous discharge rate is always above 1C/20A (1.5C/30A average) they are marginal.

The regen is also significant - it's between 20A and 50A - so the battery is pretty much always working

The car can go 40km on mostly battery only before the battery is depleted (closer to 80km if the aircon is working due to the engine being used more)
Matt
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Antiscab's NWH10 Prius plugin Lithium conversion

Post by T1 Terry » Sat, 24 Jan 2015, 17:03

So a bigger capacity pack would better load share? Just trying to determine between a small pack with high CA rating or a larger pack with safer chemistry cells but a lesser CA capability would be the best choice for my Prius upgrade.

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Antiscab's NWH10 Prius plugin Lithium conversion

Post by Adverse Effects » Sat, 24 Jan 2015, 17:14

if i have it correct

you want the smallest C rating possible as the battery's will give you more cycle life

the one thing i have found with Lipos is the higher the C the less cycles you get out of them because you push them harder

pulling 50A out of a 5.8Ah pack that is rated at 10C is less damaging than pulling 50A out of a 3.5Ah pack that is ratted at 25C

well that is what i have found with my ones i get 4 times or more the charge cycles out of the lower C rating pack

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Antiscab's NWH10 Prius plugin Lithium conversion

Post by T1 Terry » Sat, 24 Jan 2015, 19:10

So I should stick with the planned Winston or CALB grey cell upgrade then? Probably the Winston cells because I'm familiar with how they perform.... but that is in a house battery scenario, an WV scenario is a different story, so maybe the CALB grey cells after all.
What is special about the A123 cells?

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Antiscab's NWH10 Prius plugin Lithium conversion

Post by antiscab » Sat, 24 Jan 2015, 19:58

T1 Terry wrote: So a bigger capacity pack would better load share?


In my application there is only the one battery - so no load sharing

in my application, the car gets very unhappy if there's more than a 1V variation between the highest group of 5 cells, and the lowest

The GBS cells don't stay that close together when drawing 30A+ from 20Ah cells.


In a situation where you are keeping the original prius battery, and boosting it with a separate lithium battery, the GBS/TS/Winston/CALB cells will all be fine, but you may have issues fitting enough of them in from a weight perspective.

My 20Ah GBS pack only weighs 65kg

The new A123 20Ah pack will only weigh 55kg

TS/Winston/CALB don't make cells any smaller than 40AH/1.6kg
given you need 78 cells for the later prius, how much weight can it handle?

The special thing about the A123 cells is they are rated for 25C (or 500A) continuous, but I only need to use 40A continuous.
They are unlikely to sag by 1V across 5 cells, much less have that muh variation.

Where as the GBS cells are only rated to 2C (or 40A continuous), which is right at the limits of what they are capable of.

In your case, with keeping the original prius battery, you don't have to keep the car BMS happy, because you are using a separate one. The Lithium pack also won't see the full discharge current, particularly the peaks, it will just see the averages.
Matt
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Antiscab's NWH10 Prius plugin Lithium conversion

Post by antiscab » Sun, 01 Feb 2015, 17:39

I stumbled across this in my searches:

car pc in nhw10

which lead me here:

build thread
Matt
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Antiscab's NWH10 Prius plugin Lithium conversion

Post by T1 Terry » Sun, 01 Feb 2015, 19:02

Is there a translator program to run the build thread through :lol: I thought Chinglish was a challenge but this is a real test of the code breaking skills, maybe an Enigma Mk3 is required :lol:

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Antiscab's NWH10 Prius plugin Lithium conversion

Post by antiscab » Sun, 01 Feb 2015, 19:47

I used google translate - most of it made sense :D

I especially liked how he made the screen touch screen
that was cool
Matt
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Antiscab's NWH10 Prius plugin Lithium conversion

Post by gtyler54 » Tue, 03 Feb 2015, 22:54

Antiscab:- your ECU left today. one problem though, my wife took it to the ost shop, they told her to value it at $250 for insurance purposes, it may be enough to attract customs charges?
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Antiscab's NWH10 Prius plugin Lithium conversion

Post by Adverse Effects » Wed, 04 Feb 2015, 00:25

it shouldn't $1000 is the basic level

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Antiscab's NWH10 Prius plugin Lithium conversion

Post by antiscab » Wed, 04 Feb 2015, 02:46

yep, under $1000 and you are ok

For common carriers (NZ post, Aust Post, etc) there are no fees this end at all :D
Matt
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Antiscab's NWH10 Prius plugin Lithium conversion

Post by antiscab » Wed, 04 Feb 2015, 03:48

Got around to start building the A123 20Ah battery for my second prius

Cells in packaging:
Image


checking the fit in the battery box - I'll need to do some cutting after all
Image


Starting to build up using the connection kit - The plastic is actually quite brittle.

Also the cell spacing is a bit wide :(
Image


Tried again, this time using the original packing plastic as spacers:
Image

who can see the problem with wiring up?
Matt
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Antiscab's NWH10 Prius plugin Lithium conversion

Post by T1 Terry » Wed, 04 Feb 2015, 04:07

Are both the tabs aluminium? I wonder why, the normal set up is copper and aluminium so it's easy to tell the positive plate from the negative plate.

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Antiscab's NWH10 Prius plugin Lithium conversion

Post by antiscab » Wed, 04 Feb 2015, 04:50

T1 Terry wrote: Are both the tabs aluminium? I wonder why, the normal set up is copper and aluminium so it's easy to tell the positive plate from the negative plate.



ooo, good question - I will have to check tomorrow

the negative I think is tinned copper, and the positive is either aluminium or it has something attached to extend it (these cells were removed from a different battery pack in china)

Matt
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Antiscab's NWH10 Prius plugin Lithium conversion

Post by antiscab » Thu, 05 Feb 2015, 04:51

today I was dismantling the battery stick holders:

the inside dia of the outer stick holes is 36mm, but interestingly, the inner holes are 40mm - with rubber inserts to make up the difference.

If you were planning on using headway cells here, they would probably fit (though other issues)

Image


After Dad took to it with a large wood saw (good thinking dad :D)
Image

This will allow be to mount up the original prius control board with ease.

Now, for the question from yesterday:
the issue with bolting interconnects on when the battery is on it's side, is when you have a bolt in one side, the other wants to fall down and touch the other interconnects.

the results can be rather exciting

So I siliconed some acrylic 6mm square bar in the gaps, so should I lose my grip, the interconnect doesn't go anywhere

Image
Matt
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Antiscab's NWH10 Prius plugin Lithium conversion

Post by antiscab » Fri, 06 Feb 2015, 05:48


update time:

I settled on connecting up the cells in groups of 5, to match the prius BMS wiring

I'm still not sure on the cell mounting method - but I did mind that using packing tape to keep them together worked quite well.
I may actually go back and use double sided tape

I did 13 of the 20 5 cells blocks needed today:
Image

It's exceptionally time consuming

I'm also finding the connection kit parts to be rather brittle, I've managed to break 9 of them so far (down to my last spare)
Matt
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Antiscab's NWH10 Prius plugin Lithium conversion

Post by T1 Terry » Fri, 06 Feb 2015, 13:51

How do you plan to keep the pouch cells compressed? If you compress them now won't that pull on the tabs? will you now remove all the Perspex pieces to allow the link plates to fit flat on the tops or do you plan to bend the links so they go over the Perspex pieces?
It's starting to take shape now so you must feel you are getting some where now. It's fine to have all the bits, but I find the mind numbing task of assembling takes an extra special effort to get on with it and just get it over and done with, then the fun stuff starts.

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Antiscab's NWH10 Prius plugin Lithium conversion

Post by antiscab » Sat, 07 Feb 2015, 01:32

T1 Terry wrote: How do you plan to keep the pouch cells compressed? If you compress them now won't that pull on the tabs?


I plan to use aluminium plates to compress the cells in the blocks of 5 cells

I haven't made them yet, but they aren't going to be overly complicated, just two aluminium plates and 4 x M5 bolts going through
the distance between the plates is only going to be 38mm, so I'm just using normal bolts and nylocs (I might use nordlocks as well)

I have a small bender, so i plan to bend out a tab on the alu plates to bolt to the chasis for mechanical retraint

The cell tabs are unlikely to be overly stressed when only crushing 5 cells together - because I taped them, there's already no gap between them
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Antiscab's NWH10 Prius plugin Lithium conversion

Post by antiscab » Sat, 07 Feb 2015, 04:41

T1 Terry wrote: will you now remove all the Perspex pieces to allow the link plates to fit flat on the tops or do you plan to bend the links so they go over the Perspex pieces?


perspex (actually they're arcylic, it was cheaper) pieces are siliconed in place - they stop the interconnects from shorting out the cell tabs during assembly


to illustrate:
cells as they are put into the connection bits:
Image

a fully populated 5 cell block:
Image

same 5 cell block with interconnects bolted down:
Image
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Antiscab's NWH10 Prius plugin Lithium conversion

Post by jonescg » Sat, 07 Feb 2015, 04:48

Oh man that termination kit looks dodgy! I know some guys on Endless Sphere were struggling with these kits too. They will compress the corners beautifully, and leave the meat of the tab bowed :(

You reckon you'll have one of these ready for Electrikhana?
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Antiscab's NWH10 Prius plugin Lithium conversion

Post by antiscab » Sat, 07 Feb 2015, 05:19

yeah, they're not particularly strong

I'm giving some thought to getting some beefier ones made

one of the guys on visforvoltage drilled a small hole through the middle of each one and put a wood screw through
I might do that if the connections aren't good enough
I must admit I have yet to try them - might have to break up my carbon pile

the prius only needs 35A continuously and 70A peak, so I might get away with it

time will tell

I'm not holding my breath on getting it done before electikana - prototypes always take a long time
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Antiscab's NWH10 Prius plugin Lithium conversion

Post by T1 Terry » Sat, 07 Feb 2015, 14:41

antiscab wrote:
T1 Terry wrote: How do you plan to keep the pouch cells compressed? If you compress them now won't that pull on the tabs?


I plan to use aluminium plates to compress the cells in the blocks of 5 cells

I haven't made them yet, but they aren't going to be overly complicated, just two aluminium plates and 4 x M5 bolts going through
the distance between the plates is only going to be 38mm, so I'm just using normal bolts and nylocs (I might use nordlocks as well)

I have a small bender, so i plan to bend out a tab on the alu plates to bolt to the chasis for mechanical retraint

The cell tabs are unlikely to be overly stressed when only crushing 5 cells together - because I taped them, there's already no gap between them

If you go to Blackwoods or their equivalent over there you can buy stainless strapping in a bulk roll in a plastic carry cassette. Cut the length enough to give a 15mm tab each end, drill a 4.5mm hole each end, bend one end to 90*. Mark both plates top so you can identify top outer, drill and tap one plate for the 6 straps to fit using countersunk screws, allen key socket screws will make tightening between the packs easier. Compress the 5 cells with a G clamp, bend the tabs to fit the second plate and mark with a permanent black marker. Remove the plates, drill and tap, clamp and assemble. Sounds like a long complicated way to do it but the first one will give you the strap lengths required and the screw positions for the first plate on all the rest of the packs so you have templates. If you can get the strap lengths exact and the drill holes exact you can mass produce after the first and speed the job up.

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