AEVA Homepage
Forum Home Forum Home > Technical Discussion > Batteries, charging, management and monitoring
  New Posts New Posts RSS Feed - Battery Replacement - MX-5
  FAQ FAQ  Forum Search   Events   Register Register  Login Login

Battery Replacement - MX-5

 Post Reply Post Reply
Author
Message
CZal View Drop Down
Groupie
Groupie
Avatar

Joined: 12 May 2009
Location: Melbourne
Status: Offline
Points: 59
Post Options Post Options   Thanks (0) Thanks(0)   Quote CZal Quote  Post ReplyReply Direct Link To This Post Topic: Battery Replacement - MX-5
    Posted: 13 July 2017 at 3:09pm
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??


Edited by CZal - 13 July 2017 at 3:14pm
Back to Top
CZal View Drop Down
Groupie
Groupie
Avatar

Joined: 12 May 2009
Location: Melbourne
Status: Offline
Points: 59
Post Options Post Options   Thanks (0) Thanks(0)   Quote CZal Quote  Post ReplyReply Direct Link To This Post Posted: 13 July 2017 at 3:10pm
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-battery-modules-24V-21-2kWh-1776-Panasonic-18650-cells-/262288917272

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

I've been playing around on Alibaba but with great trepidation...

Edited by CZal - 13 July 2017 at 4:17pm
Back to Top
jonescg View Drop Down
AEVA Member
AEVA Member
Avatar

Joined: 21 January 2010
Location: Perth, WA.
Status: Offline
Points: 2357
Post Options Post Options   Thanks (0) Thanks(0)   Quote jonescg Quote  Post ReplyReply Direct Link To This Post Posted: 13 July 2017 at 3:24pm
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.
I challenge you to come up with a better invention than the bicycle
Back to Top
CZal View Drop Down
Groupie
Groupie
Avatar

Joined: 12 May 2009
Location: Melbourne
Status: Offline
Points: 59
Post Options Post Options   Thanks (0) Thanks(0)   Quote CZal Quote  Post ReplyReply Direct Link To This Post Posted: 13 July 2017 at 3:35pm
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 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?


Edited by CZal - 13 July 2017 at 4:19pm
Back to Top
jonescg View Drop Down
AEVA Member
AEVA Member
Avatar

Joined: 21 January 2010
Location: Perth, WA.
Status: Offline
Points: 2357
Post Options Post Options   Thanks (0) Thanks(0)   Quote jonescg Quote  Post ReplyReply Direct Link To This Post Posted: 13 July 2017 at 7:05pm
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.
I challenge you to come up with a better invention than the bicycle
Back to Top
Adverse Effects View Drop Down
Senior Member
Senior Member
Avatar

Joined: 31 December 2010
Location: Brisbane
Status: Offline
Points: 1099
Post Options Post Options   Thanks (0) Thanks(0)   Quote Adverse Effects Quote  Post ReplyReply Direct Link To This Post Posted: 14 July 2017 at 11:31am
Back to Top
CZal View Drop Down
Groupie
Groupie
Avatar

Joined: 12 May 2009
Location: Melbourne
Status: Offline
Points: 59
Post Options Post Options   Thanks (0) Thanks(0)   Quote CZal Quote  Post ReplyReply Direct Link To This Post Posted: 14 July 2017 at 6:52pm
Thanks Adverse,

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

C.
Back to Top
Adverse Effects View Drop Down
Senior Member
Senior Member
Avatar

Joined: 31 December 2010
Location: Brisbane
Status: Offline
Points: 1099
Post Options Post Options   Thanks (0) Thanks(0)   Quote Adverse Effects Quote  Post ReplyReply Direct Link To This Post Posted: 15 July 2017 at 5:56pm
i think others here (including me) may be interested in costs from them
Back to Top
Richo View Drop Down
AEVA Member
AEVA Member
Avatar

Joined: 15 June 2008
Location: Perth, WA
Status: Offline
Points: 3247
Post Options Post Options   Thanks (0) Thanks(0)   Quote Richo Quote  Post ReplyReply Direct Link To This Post Posted: 17 July 2017 at 12:28pm
Originally posted by CZal 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.
If the sun's not up turn your lights ON - duh! Help prevent road rage - get outta my way!!
Back to Top
Johny View Drop Down
AEVA Member
AEVA Member
Avatar

Joined: 23 June 2008
Location: Melbourne
Status: Offline
Points: 4049
Post Options Post Options   Thanks (0) Thanks(0)   Quote Johny Quote  Post ReplyReply Direct Link To This Post Posted: 17 July 2017 at 1:00pm
Out of curiosity - how long did they last - km?
Back to Top
CZal View Drop Down
Groupie
Groupie
Avatar

Joined: 12 May 2009
Location: Melbourne
Status: Offline
Points: 59
Post Options Post Options   Thanks (0) Thanks(0)   Quote CZal Quote  Post ReplyReply Direct Link To This Post Posted: 17 July 2017 at 8:29pm
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)

Edited by CZal - 17 July 2017 at 8:32pm
Back to Top
CZal View Drop Down
Groupie
Groupie
Avatar

Joined: 12 May 2009
Location: Melbourne
Status: Offline
Points: 59
Post Options Post Options   Thanks (0) Thanks(0)   Quote CZal Quote  Post ReplyReply Direct Link To This Post Posted: 17 July 2017 at 8:55pm
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?
Back to Top
jonescg View Drop Down
AEVA Member
AEVA Member
Avatar

Joined: 21 January 2010
Location: Perth, WA.
Status: Offline
Points: 2357
Post Options Post Options   Thanks (0) Thanks(0)   Quote jonescg Quote  Post ReplyReply Direct Link To This Post Posted: 17 July 2017 at 9:35pm
Originally posted by CZal 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.

I challenge you to come up with a better invention than the bicycle
Back to Top
Richo View Drop Down
AEVA Member
AEVA Member
Avatar

Joined: 15 June 2008
Location: Perth, WA
Status: Offline
Points: 3247
Post Options Post Options   Thanks (0) Thanks(0)   Quote Richo Quote  Post ReplyReply Direct Link To This Post Posted: 18 July 2017 at 12:44pm
Originally posted by CZal 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.


Originally posted by jonescg 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.
If the sun's not up turn your lights ON - duh! Help prevent road rage - get outta my way!!
Back to Top
 Post Reply Post Reply
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 11.03
Copyright ©2001-2015 Web Wiz Ltd.

This page was generated in 0.235 seconds.