Replacing cells in a Leaf Battery Pack installed in an EV conversion.

Batteries from a Nissan Leaf used in an MGB conversion had some cells which became over charged. 4 cells were replaced in the main battery unit.

[@ateshnarayan9769]

You guys are genius. This is what many people don't tell or share in the you tube for viewers but are doing it. God bless you all

[@flyguille]

a complete recovery battery pack.................we hope! says!, at the end!

[@paguliukas]

would be interesting to see more about MGB what motors you used how long you spend converting very interesting

[@SynergisticECOnomy]

Why the BMS did not protect your pack?

[@mikeatyouttube]

+SynergisticECOnomy Short answer : because there's no BMS attached. Longer answer as to why the Leaf BMS is not attached is because the Leaf BMS is expecting the batteries to be wired in series and in this conversion, the whole pack is divided into 4 equal parts of 128Volts each and these are wired in parallel while driving (because that is what the controller/motor is expecting). The pack is charged in series. So when charging the entire pack is rewired to be in series and charged at 512V. The eagle eye person will notice that this is larger than the standard Leaf pack which maxes out at about 384V. In this conversion we are using 128 battery cells (64 'bricks') rather than the standard 96 battery cells (48 'bricks'). This was done to increase the range. What is completely clear from this video is that some sort of battery management or at least battery monitoring is definitely needed.

[@kailahti8195]

What was went wrong with those damaged battery bolcks? Why dead battery blocks expanded so bad...? Overheatig or over charged...? Is BMS still alive...? How old those leaf battery blocks are...?

[@mikeatyouttube]

It's explained in the video. 4 cells got overcharged and when that happens the temperatures rise and the chemistry changes irrevocably. No BMS was operating during charge time. A bms MIGHT have prevented this failure - but quite possibly not. It was a wiring/configuration error. At least only 4 cells were lost.

[@NewmanAutomotive]

Why on earth are you running a DC/DC converter from only a section of the pack??? You should never do this, it's extremely bad practice and will guarantee cell imbalance and damage!! Any load should only ever be taken from the whole battery, this way all cells will stay at the same state of charge. I can't imagine how you could even successfully charge such a set up even with an active BMS, it's a disaster waiting to happen...

[@mikeatyouttube]

+NewmanAutomotive The other videos about this car would explain why this setup is valid (except that the original valid setup was altered and that's why only 4 cells were damaged not all 16). Briefly, the DC-DC converter was ONLY operational when the entire battery pack was connected to it (thereby depleting the pack uniformly). The DC-DC only operated when the car was in 'drive' mode where the entire 400V pack was wired such that it was divided into 4 'quarter' packs of 100V each. These 100V packs were wired in parallel to drive the 100V controller. Only when charging was the pack rewired to be in 400V to satisfy the Brusa charger. (See the other videos for an explanation as to how this was done). When charging, the DC-DC was (supposed) to be off. Things started to go wrong when we upgraded to pack to 520V (nominal) meaning that dividing the pack into 4 for 'drive' mode meant supplying 130V to the controller. The pack was charging at 520V. The mistake made was to keep the DC-DC wired over 100V (12 Leaf battery cells) rather than re-wire it over 130V (16 cells). Then the other mistake was to somehow leave the DC-DC on while charging - then then, even more critically, not charging but also not in the drive configuration. A veritable catalog of errors but also not too expensive (except that we believe the controller got damaged when the bad cells swelled and consequently connected the body of the car to about 120V relative to pack zero). Glad I'm not paying the bills :)

[@NewmanAutomotive]

+mikeatyouttube Thanks for the reply, I also run nissan modules in my own conversion, love 'em, but please do be very careful, you're lucky they just swelled up and didn't catch fire. Do you have a link to a build diary for your car?, I'd be interested to take a look at it. I really mean no disrespect, but the setup sounds like an over complicated cludge in order to use a 400v charger. Why not just use a 100v charger? Also, when not using an active BMS, from a balance point of view, it's much better to re-configure the modules to buddy sets. A series string of 12 packs of 4 modules in parallel. This does require dis-assembly and re-assembly and some bus bar work, but is much better practice than running larger series strings of modules in parallel.

[@mikeatyouttube]

+NewmanAutomotive It is a tad complicated, I agree. It's a friend's car but it pretty much my build. On my MG (roadster) I have pretty much what you suggest - that is: half a Leaf pack but wired as two parallel 100V (really 96V) sets with a 100V charger. I have a monitoring system - just 48 voltmeters showing the state of each cell - not quite a BMS but better than nothing. Going back to my friend's car, the 400/100V switch over was fun to design and the reason for the charging at 400V was (originally) two fold - firstly we could used the Leaf BMS - you certainly cannot use it when the cells are paralleled up into 100V blocks - and secondly we were going to use the Leaf charger - we had the whole car (totaled) so why not? The motor and controller were 100V so hence the change over mechanism. As it happens we couldn't get the charger to work without the car's VCU and it needed liquid cooling so quickly we switched to a programmable Brusa charger that could take 3kW input. Later we got hold of more Leaf cells and wanted to add more capacity. So his car now has 1.25 Leaf packs and 100+ miles of range but the BMS doesn't work any more. The car was working just fine (8000+ miles of commute driving over about 9 months) then problem started when the car was in the shop getting the respray job. Somehow the ignition was on which meant the DC-DC was on and things when down hill from there. I was equally worried about the possibility of fire especially when charging in a paint shop! I should have suggested not doing that. I'm very interested in knowing about your project - any links for that? I watched the video. I see you're in the UK. I think you're fortunate in the UK because there are so many small, light cars available for potential conversion and they're cheap too! I'll ask some questions on your site to keep the information in the right place. This is the link for the description part for the MGB GT: kzbin.info/www/bejne/l4bPl2mNbLKIn9k

[@tayseerelayan]

Is it possible to replace the broken cells. For a complete battery? 12 bar. If the car battery 8 bar. So we do not replace the battery when you become weak?

[@mikeatyouttube]

Yes, it would be possible to replace individual cells. It would be a big task. Firstly, you need to identify which cells are weak (using the LeafSpy App). Make a note of all the cells that you'd like to replace (the cells are not numbered but you can just count up from zero volts on the pack to find the right cell). Then you have to remove the pack from the car - it weighs 300kgs - and open it. (This will void the warranty, of course.) Next dismantle the three packs of batteries from the framework and, with care, unbolt and remove the bad cells. The hard part will be getting replacement cells! Finding a crashed Leaf is probably the best solution - take that apart too. The key important task before inserting the good battery in your pack, is to make sure the battery voltages are all equal to within 0.1 volts. To to this you will need to manually discharge some cells (using some resistance device, like a small 12V heater). Check the voltages constantly. When all the cells are even you can bolt everything back together. And, critically, seal the battery box perfectly using the same sealant as used when installing windshield glass. If you don't seal it properly then water WILL get in and you'll end up burning the car. See this video for evidence :)... kzbin.info/www/bejne/aJSsoGxrjJKpnKc I think it would take about one week to do this job.

[@tayseerelayan]

thanks allot

[@3dmotormaker]

Shame you did not name your video correctly

[@randycarter2001]

Lesson to learn: never tap a traction battery in the middle. It looks simple and inexpensive but the damage done over time can be catastrophic.

[@ShahabIntezari]

hi where did you get the the new cells from?

[@mikeatyouttube]

They were left over from the second Leaf we took apart. This car in this video uses a whole Leaf pack (96 cells, I.E. 48 physical battery units) plus another 32 cells, 16 physical battery units (total 128 cells or 64 units) . Having taken two Leafs apart we had a total of 182 cells (96 battery units) and this car got 128 cells, my car (another MG) got half a pack - 48 cells (24 units) Having divided up the packs we had, if you do the arithmetic, we had 16 cells (8 battery units) and we used four of those in this battery replacement project.

[@kakudakachchayana7697]

tell me more abount how to repair and how to get new betteries??

[@mikeatyouttube]

The replacement batteries were extracted from another crashed Leaf.

[@TimFrentz]

I bet you have a victron Battery protect installed now....

[@nickreid5297]

Please wear special 500 volt gloves before touching anything on the battery pack.

[@DannyBokma]

Are you using the battery without a BMS :o?

[@mikeatyouttube]

+Danny Bokma It's not a good idea at all. At the very least there should be a battery voltage monitoring system - just a digital display on each cell so you can visually see voltage discrepancies between cells. There are issues with active BMS modules in that most (including the Leaf BMS) balance the modules by resistively depleting the cells which have higher voltages. This type of BMS is fine so long as things dont go wrong. I have heard of two such battery packs where the BMS drained the cells down to zero which, of course, ruined all the cells. The real answer, of course, is to incorporate the BMS module INTO the cells directly. That way each cell can decide it's own health, prevent overcharging and also protect itself from over depletion. One of the huge challenges of BMS installation and maintenance is the large number of wires requires to connect all the batteries to the BMS module. On the Leaf there are 96 wires which trail around the battery box all of which have to make perfect connections. It must cost a fortune to wire them all up. Putting the BMS in the cell would make wiring simpler albeit at the expense of more electronics per cell. In this project, the 4 cells were damaged by a mistake during charging and it's interesting to note that no amount of battery management would have prevented the damage. We were just rather lucky that the cells were held together so well that they didn't explode in the vehicle while charging.

[@DannyBokma]

The battery management systems I have worked with are also in control of the charge relais and discharge relay. Depending on cell voltage / state of charge the load or charger where disconnected. I would surely never sleep well if my LiIon based battery was charging without individual cell voltage monitoring. Industrial cells are all short circuit proof (as in will not start a fire). They will not survive it, but the place would not burn down. good luck in your project!

[@mikeatyouttube]

+Danny Bokma Interesting. The Leaf cells are hard-wired in series : there are no relays or control on individual cells. Each cell is monitored by the BMS and maybe, as well as doing balancing, the computer might be able to shut the charger off if one cell registers a dangerously high over-voltage or a short-circuit. It's difficult to know if that would actually happen. Whether a detection of a overcharge voltage and subsequent shutdown would stop a fire is unknown. Nissan must be doing something right because I haven't heard of any fires during charging or otherwise. BTW - what battery systems are you familiar with?

[@DannyBokma]

Your statement -> "if nothing alters the soc nothing will change " is fine by me. However when you use a battery that statement no longer holds. For example the discharge current will heat the battery, since the middle of the battery will become hotter than the outside batteries the situation is no longer the same for all batteries resulting in a shift of SOC.

[@DannyBokma]

+m1aws on charging there is less current so different temperature distribution. Yeah it's little but this is only one thing I am talking about now, there are so many other things creating inequalities. But hey I don't mind you not using a BMS, your house isn't next to mine xD. But please don't defend and tell others to do so.

[@Ecoenergy]

One very smart person in NASA once said about people DIY'ing life and limb stuff. "they don't know what they don't know" so some are going to get injured or even die.

[@markwilliams5654]

Depending on why you done the conversion in the first place if it's to save on pollution and save the Planet you succeeded but you created a death trap that's not safe for the road for first responders or anybody else well done what have you achieved you wasted a lot of money and you could have just bought a Nissan Leaf

[@markwilliams5654]

Wow u have a frame leak this is a death trap

[@markwilliams5654]

Wow this is a very dangerous and bad conversion and u drive that on the public roads thanks then if u crash into anything