Battery Replacement - MX-5

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CZal
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Battery Replacement - MX-5

Post by CZal » Thu, 13 Jul 2017, 23:09

Hi team,

It's time for me to replace my old battery pack and was wondering on people's thoughts to complete.

I currently run 45 x 90Ah LiFePo4 Winstons
They're all in series broken into 2 packs (front and rear of the vehicle)

My drivetrain is a WarP9 driven by the ZEVA MC600S controller:
• Max motor current: 600A
• Maximum battery current: 600A
• Nominal battery voltage range: 96V-144V
• Absolute maximum voltage range (self-limiting): 72V-180V

I use the EVPower string BMS and a Kingpan 144V charger (would most likely have to replace these)

Ideally I would like to get the battery up to about 20KWh to really give the car the range and oomph she always deserved :0)

144V @ 150Ah would be nice (45cells)
153.6V @ 120Ah would be ok too (48cells)

Cost as always is an issue... $5k would be great, I think $7.5k is better expectation management.

Anyone else out there been looking? Perhaps a group buy in the pipeline??
Last edited by CZal on Thu, 13 Jul 2017, 13:14, edited 1 time in total.

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Battery Replacement - MX-5

Post by CZal » Thu, 13 Jul 2017, 23:10

I've summarised with pictures in this doc:
New_Battery_Requirements.docx

I would love to get the 4 pack of TESLA packs available for $5.5k US with $600 delivery shown here:

http://www.ebay.com/itm/4-Tesla-Model-S ... 2288917272

20KWhrs at only 100Kg! except that the voltage only comes up to 96V.. I'd have to get 6 packs... Still great except for the price Image

I've been playing around on Alibaba but with great trepidation... Image
Last edited by CZal on Thu, 13 Jul 2017, 14:17, edited 1 time in total.

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Battery Replacement - MX-5

Post by jonescg » Thu, 13 Jul 2017, 23:24

Tesla battery modules are the only way you'll get bulk power and energy for lowest cost. Otherwise, $7.5k won't get you much else. I've got some good Lithium cobalt pouch cells which are about $860 per kWh before you even start to assemble them into a battery.   However it depends on the volumes available inside the car.

Buy the Tesla modules. If you want bang for buck, it's the best deal going.
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Battery Replacement - MX-5

Post by CZal » Thu, 13 Jul 2017, 23:35

Thanks for the quick reply Chris! I'm inclined to agree, they do look nice and powerful.... but 6 packs at $11.5k with delivery will kill my marriage Image And I've still got to factor in a new charger...

But let's play devil's advocate (only because I want to convince myself that I should do it and to hell with the consequences!!)
Do I need 6 packs? Reckon I can get away with 5? Brings my voltage down to 120V but also saves me $1,790
And would you know how the BMS output works? Surely there's no 6S balancer/charger at this power requirement. Would I just get an Elcon 120V charger and periodically balance?
Last edited by CZal on Thu, 13 Jul 2017, 14:19, edited 1 time in total.

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Battery Replacement - MX-5

Post by jonescg » Fri, 14 Jul 2017, 03:05

You could bypass the Tesla BMS and use your own (Zeva, Batrium, EV-Power, Fybalite) or just leave balance taps somewhere convenient (and waterproof) and balance charge them once a year.

You will be disappointed if you bought LiFePO4 again. Save your money and get the better batteries if you know they will fit.
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Battery Replacement - MX-5

Post by Adverse Effects » Fri, 14 Jul 2017, 19:31


CZal
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Battery Replacement - MX-5

Post by CZal » Sat, 15 Jul 2017, 02:52

Thanks Adverse,

I've sent them an email today... let's see what happens...

C.

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Battery Replacement - MX-5

Post by Adverse Effects » Sun, 16 Jul 2017, 01:56

i think others here (including me) may be interested in costs from them

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Battery Replacement - MX-5

Post by Richo » Mon, 17 Jul 2017, 20:28

CZal wrote:I currently run 45 x 90Ah LiFePo4 Winstons


And what happens to these once you replace them?
Surely they aren't completely dead.
Perhaps you can sell them on to a smaller conversion or someone's BESS.
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Battery Replacement - MX-5

Post by Johny » Mon, 17 Jul 2017, 21:00

Out of curiosity - how long did they last - km?

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Battery Replacement - MX-5

Post by CZal » Tue, 18 Jul 2017, 04:29

OK I received an email back from EVWest.

The upshot is:
They do deliver to Aus. They say that delivery to the port will be the most economical
Price is in US and they'll accept Paypal so the conversion can all happen there.
There isn't a BMS in the module, just cables so you can us your own.
I've replied back asking for an actual price to Melbourne port.
Also if there are volume discounts

@Richo, I think I'll use the old set as a powerwall (well maybe a power floor) here at home. They've had a hard life, so I don't think they'll be too great even in a smaller conversion.

@Johny I actually changed dashes (and hence odometers) partway through the conversion. I've tried to go back through my photos but none of the numbers make sense. It might be more useful to piece together their life span:
I have a photo of when I originally received the cells dated 05/01/2011
They then sat around during the build. First test drive was 22/04/2012.
A few more very light test drives through 2012 where big changes in personal life occurred during which I pulled her back down for a proper resto of the car.
Finally registered in 05/2014 where she became a daily driver.
This is where the cells really went to work. I must say i think I would improve most things about their use during this time.
- Firstly I don't rate the Kingpan charger I've been using. The first one I bought died and the second one seems to send a large ripple through the pack.
- The cells weren't a stranger to 3C discharge (occasionally over that when showing off). On the freeway they spent long minutes at 150A which is about 1.7C
- In the hot summer months the front pack received a lot of heat from the motor (approx 70c). Although the voltage sag now seems to be spread pretty evenly across the front and rear pack

My best guess is 20,000km in the registered period. Which on reflection is not that great.

Next pack will have:
- a better charger (Elcon TC if it's prismatics again)
- a larger size so that it's rarely at 3C (@150Ah is over 50% larger)
- be well insulated from the motor by sealing off the lower motor section from the upper cell section. (Which strangely enough will help the motor as well as the air wont circulate in the engine bay)
Last edited by CZal on Mon, 17 Jul 2017, 18:32, edited 1 time in total.

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Battery Replacement - MX-5

Post by CZal » Tue, 18 Jul 2017, 04:55

Hey Johny,

Are they 38140s in your avatar? I seem to remember your cells being in nice ~12V packs... What's been your experience? (happy for you to PM me for a chat if you have time?)

Also maybe people can riddle me this... My cells voltage sag under modest acceleration, which is why I'm looking to replace.
Funny thing is if I feather them they sag out of range at ~120A draw but if I pulse them with two short accelerator thrusts (200 - 250A) they then don't complain at 150A - 180A draw.

My last reasonable drive was to Cremorne approximately 25km away. Although I have poor acceleration to avoid the voltage sag, I made the 25km ok. I charged again at Cremorne for about 2 hours and made it back under modest acceleration. This included slowly getting up to 100km/h on the freeway.... I'm not missing anything here before I outlay a few thousand dollars am I?

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Battery Replacement - MX-5

Post by jonescg » Tue, 18 Jul 2017, 05:35

CZal wrote: My cells voltage sag under modest acceleration, which is why I'm looking to replace.
Funny thing is if I feather them they sag out of range at ~120A draw but if I pulse them with two short accelerator thrusts (200 - 250A) they then don't complain at 150A - 180A draw.


The battery will only sag at sustained high discharge, and the highest discharge rate there is would be 150 km/h on the freeway. Rapid acceleration only bothers the motor for the first 3 seconds of the launch; the battery will be delivering modest current at a high voltage (VI)motor=(VI)battery. I'd say the pulse is long enough for the current to do its job, but now quite long enough to bring the voltage right down.

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Battery Replacement - MX-5

Post by Richo » Tue, 18 Jul 2017, 20:44

CZal wrote: My cells voltage sag under modest acceleration, which is why I'm looking to replace.
Funny thing is if I feather them they sag out of range at ~120A draw but if I pulse them with two short accelerator thrusts (200 - 250A) they then don't complain at 150A - 180A draw.

jonescg wrote: The battery will only sag at sustained high discharge...

Maybe if everything was perfect and new.

So either a terminal, not necessarily on a battery, has an oxidation layer that the high current punches through.
Or the high current causes a rapid heating internal to the battery that puts it in a temporarily more functional state.
How about prismatic cell sloshy fluid permeated through the plastic case and evaporated.
Electrode damage/wear within the cell that a pulse current punches through some build up.


Terminal cleaning would take a while but doable.
A BMS per cell reporting would help identify a possible cause.
But at the end of the day it may not be fixable anyway.
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Battery Replacement - MX-5

Post by CZal » Fri, 28 Jul 2017, 21:20

Thanks for the replies guys,

Probably the only bit of information I haven't provided is that I had a bulged cell early last year that I replaced... That nice new cell may have been pushing current through the others if there was significant sag?

I think the theories will keep me busy for a little while yet, but I think you're right Richo, at the end of the day it's probably not fixable.

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Battery Replacement - MX-5

Post by CZal » Fri, 28 Jul 2017, 21:42

Further to the original post then, I've put a spread sheet together of the (non LiFePo4) options. These are predominantly second hand Tesla modules and new Leaf modules from the US.

All my dealings on Alibaba for LiFePo4 (or anything) seem really, really dodgy (incorrect Ah specs, the size/weight of the cells don't match what can reasonably be expected as the output) so I think a large financial transaction is out at this time.

New_Battery_Comparison.xlsx
(I've put in a rough estimate of $600US transport for all options)

@jonescj... I actually think you're right about the Tesla modules... Great build quality, great weight characteristics and a good per kWh price makes them pretty compelling... Especially the build quality... Overall cost may be an issue, just bearing in mind that a BMS and charger are required at an additional $1.5 - $2k

@AdverseEffects, the old Smart modules are really attractive and I can get 18kWh for about $6.5k AUD... That would be enough for my purposes but unfortunately their form factor puts them at 1M in length and I don't think I'll be able to fit them in. (I need to get the old pack out to do proper measurements)

The newer 5.3kWh packs are really good and if I'd built a beetle (that could now transport the entire family) instead of an MX-5 (that is now a drive for not enough passengers) I'd just pay the $10.5k and get 30kWh making the car essentially future proofed for 10 years.
I've found the slightly smaller units (from the pre-90D models S) for $1,199US at Edison Motors

Anyhoo this is what I'm doing (basically waiting 1 month):
1. I have a friend travelling to China in 3 weeks. He will see if these modules are available there (or perhaps something from BYD or similar car there, I've specified it has to be out of a high quality car)

2. AUD is on it's way up just at the moment and each .01 change is $100 change in price, so am watching carefully.
Last edited by CZal on Sun, 30 Jul 2017, 10:01, edited 1 time in total.

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Re: Battery Replacement - MX-5

Post by Peter C in Canberra » Tue, 01 Aug 2017, 11:23

CZal wrote:
Tue, 18 Jul 2017, 04:29
- The cells weren't a stranger to 3C discharge (occasionally over that when showing off). On the freeway they spent long minutes at 150A which is about 1.7C...
My best guess is 20,000km in the registered period....
This was for 45 x 90Ah Winston cells. I have the same except older since they were Thudersky branded. Now, after more than 8 years and 55,000km I can still pull 500A out of them even though they now have only 70Ah capacity. I changed controller part way though and that was a big performance boost - from a 500A Curtis that in the end would barely do 400A to a Kelly that could do 1000A but limited to 800A. "long minutes at 150A" makes me wonder if the controller might not be taking any more, not that the battery couldn't deliver more. Remember that the 600A limit out at the motor could be hit with much lower current/higher voltage at the battery. With a series DC motor torque is proportional to the square of motor current so 800A is a lot more torque than 500A or 600A.

45x90A is a limit on range but also what I could easily fit in the car and could afford at the time. Mine very often do 3C and always when showing off. So, I agree they have had a hard life. If either of us had (say) 45 x 180Ah rather than 90Ah the cells would have an easier life because 2x bigger cells would always be at 2x lower C rate. Also they would less often be taken to a low state of charge. I would suggest that the larger the capacity, the less important to have high C rated cells since they will do as much as the controller can take at a low C rate.
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Re: Battery Replacement - MX-5

Post by CZal » Tue, 01 Aug 2017, 12:27

Wow that's really interesting Peter,

I still think my prob is on the battery side rather than in the controller. the car doesn't seem to be stalling, it's that the BMS modules alert that the batteries are out of (voltage) range.
Yours don't sag the voltage and alert the BMS when you're pulling 500A?

Your story sounds really similar to mine, just a different outcome... Just out of curiousity, which BMS are you running?

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Re: Battery Replacement - MX-5

Post by CZal » Tue, 01 Aug 2017, 15:51

btw team I've gotten a bulk buy price on the following: http://www.ebay.com.au/itm/142458481269?ul_noapp=true
(in deference to the running auction I won't disclose cost unless there's a genuine interest)

I've requested a shipping cost from TGF

These are the model S modules. Anyone want to join in please let me know now and let's see if we can reduce it a little further.

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Re: Battery Replacement - MX-5

Post by jonescg » Tue, 01 Aug 2017, 17:05

Hey Costa,

(Thanks to the new forum I can see it was you!)

The Tesla packs are great if you can rig up the cooling loop. They won't deliver anything like what they promise unless that coolant is working. It's pretty thin aluminium tube, so the coolant needs to be mainly glycol. If you used water and a leak were to form, the packs would get wet and potentially corrode. They do have a bit of a handbrake on power, but probably still better than the LiFePO4 that's there already.

Oh - the 5 Ah cells I normally bring in are now $15 each instead of $16 each... Exchange rate could get a move on any time now :)
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Re: Battery Replacement - MX-5

Post by CZal » Tue, 01 Aug 2017, 18:21

I'm surprised you couldn't tell from my rambling!

So something else to add to the re-design! Well before tackling that I still need to settle on a base solution (yes based on bang for buck)

I've covered most everything and I think the decision is getting to the pointy end now (this new Tesla opportunity might mean that I shouldn't wait to see what my mate finds in China)
I want the Tesla packs but:

One thing I've added to my version of the spreadsheet that I'm hoping to get more info on is used Chevy Volt cells.
They're bigger and heavier but really really cost effective. 18kWh in 3S3P (144V/141Ah) = 4,400AUD + delivery + GST
They're 164kg compared to my existing pack of 150Kg but they're max output exceeds the 600A of my controller

They're from a 2013 car and apparently no Volt pack has been over worked because the fossil burner kicks in when required...

Nowhere near as good as the Tesla packs but the volts/Amps and kWhrs are definitely enough to meet my needs (even though they don't meet my wants) at 60% of the outlay.

Comments welcome

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Re: Battery Replacement - MX-5

Post by CZal » Tue, 01 Aug 2017, 18:37

So it looks like:

1. The Smart 3kWh Tesla packs look awesome but won't fit in the car
2. The volt packs will definitely do the job but aren't as sexy as the Model S packs and there's a question mark due to their age
3. The Model S packs have come up for a good per kWh price but I would still need to get a lot of kWhrs to make up the voltage.
decisions, decisions

One last question on the Model S packs. Can I get away with 5 in series?
Reason for the question is of course that there's a significant price consideration.

5 packs is 26kWhrs which is more than enough.
The max current of 700A is more than the controller will draw so there's some natural protection against myself.
It's really about the volts. Is 114V nominal (100Vmin) too low?

If I go with these modules I'm going to put my negotiation skills to the test (both with the vendor and more importantly with, the more challenging, minister of finance) to try and get 6 but really is 5 in series enough???

Again, comments welcome...

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Re: Battery Replacement - MX-5

Post by CZal » Thu, 24 Aug 2017, 21:48

No comments good or bad? I thought I'd hear something along the lines of "You're soft, go the 6 or even better go the 7, 159V will really make her go!! " :D

Bang for buck, the Tesla modules are the best value, so that's where I'm leaning. Mainly because I see that the BMS boards have been reverse engineered enough to be useful.

Next thing was getting the shipping sorted. That took a little while as LiPo needs some extra paperwork, the crate has to meet a standard to get on a ship, etc, etc
Anyway, I've managed to get a decent rate but the smallest size purchasable is 1 cubic meter. I'll be taking up about 1/3 of that so if there's anyone that needs to bring something down from the US I'd be more than happy to split costs. (The Cubic Meter costs me $AU1,500 + Insurance, insurance is optional)

I'm looking at Low Milage Model S Modules if anyone is interested. Although US vendor has been having a harder time getting cars as they're becoming popular not just with EV enthusiasts but with the Solar crew (30kWh in a 3P2S config is getting bigger and bigger for solar storage)
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Re: Battery Replacement - MX-5

Post by jonescg » Thu, 24 Aug 2017, 22:02

Nice one Costa! Yes it's pretty hard to beat that kind of $/kWh.
You might even have room for your luggage!
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Re: Battery Replacement - MX-5

Post by Adverse Effects » Fri, 25 Aug 2017, 08:07

anyone making EBike's may want them as well each module could make an awesome custom Ebike

you could even ask over at endless-sphere.com or other ebike auzzie forums if there are others that want to group buy because i know it just gets cheaper and cheaper the more you get in 1 go

with shipping last time i looked in to it you could fill a 20' container and ship it from china for less than $5K and that is a hell of a lot of battery packs lol

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