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Discussion Starter · #1 ·
I know this is probably a silly question but if the physical size of the battery casing is the same in the 24/30, could you in theory add cells to your 24 pack to make a 30 pack or is the inners designed different ?
 

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Not as simple as that. The BMS software is designed for the 24kw and you would need to change the software to reflect the increase in battery size. The 24kw BMS might not be able to do this change so you would probably need a 30kw BMS from a scrapped vehicle and then have it installed and registered to your vehicle.

Anything is possible, any engineering job can be done if you want to throw enough time and resources at it.
However, it may be far less hassle just to px your car for a 30kw!:)
 

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Discussion Starter · #3 ·
Ok I see what you are saying and I agree , but say I get a 30kw BMS Ecu and the extra cells will they fit into the case? I think you would also need to get the bms paired or a CAN bridge fitted?
 

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One problem with that right away is that adding more cells in series would increase the voltage... and more series cells means that the BMS would have more individual cells to monitor - which it is not capable of doing as it only has the circuitry to monitor the number of series cell pairs that the car already has. (Also the HV system of the car will be designed with a certain maximum voltage in mind - you can't just increase that without consequence)

You could only increase capacity by replacing all the cells with the same number of cells but larger Ah capacity. As long as there is a way to do a capacity calibration (which I'm sure there would be in the Nissan diagnostic tool) the BMS can be taught the increased Ah capacity of the new cells to fully utilise them.
 

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Davey- do you have access to diagnostic rigs for EV's? Some of that equipment is bespoke (Not many sales so high costs) and very costly to calibrate and interpret results correctly. You really need to know what you are doing and take all the precautions when dealing with HV components that are capable of delivering high-current lethal charges.

I have spent most of my working life repairing and maintaining video projector systems that generate voltages of up to 35,000 volts - but these were with very low current supplies. I was always extremely careful when working on equipment, NEVER using 2 hands, always with one hand in our pocket as our lecturers drilled into us as students.

The sort of equipment in an EV is much lower voltage than I was dealing with, but it is the current that kills, not the voltage. In layman's terms, think of a current supply as the sheer amount of supply a source can deliver, a battery in an EV can deliver huge amounts. If you have ever shorted a lithium battery's terminals and seen the explosion and resulting fire, multiply that by many thousandfold from a Leaf battery and you get an idea of the sheer energy available to kill you.

I would not attempt such a modification, and I know a bit about what is involved, for a layman it is potentially lethal.
 
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Nissan Leaf Accenta 30kWh, 3.3kW, 2017
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Unless I am mistaken, there are the same number of cells in a 24kWh and 30kWh pack, it's just that the cells themselves have a higher capacity. So adding cells wouldn't work in the package, along with the all the other issues raised above. Adding cells would also break the 400V barrier into the next class of inverter which I would have to guess the Leaf's one wouldn't really be rated for.

Just replacing the cells for higher capacity could work without a software update if the BMS generates a SOC from an open cell voltage. However, that would most likely only occur when the car is switched off and on and instead relies on columb counting whilst running, which it would assume for a 24kWh capacity rather than a larger one.
 

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Discussion Starter · #7 ·
Ok thanks for all your replies It was only a hypothetical question. I thought that the 30 pack had more cells , not the same amount with larger A/h hence the question I asked and no I am not an expert in this field .
I work for a lorry main dealer as a technician and am starting the training on full battery trucks next month. I would love to do a conversion my self but just weighing up costs. I think unless you are very skilled it’s probably not best to crack open a pack unless you know what you are doing!
 

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Ok thanks for all your replies It was only a hypothetical question. I thought that the 30 pack had more cells , not the same amount with larger A/h hence the question I asked and no I am not an expert in this field .
I work for a lorry main dealer as a technician and am starting the training on full battery trucks next month. I would love to do a conversion my self but just weighing up costs. I think unless you are very skilled it’s probably not best to crack open a pack unless you know what you are doing!
The more I think about it the more it terrifies me to think of an inexperienced person messing about with these battery packs.
I am hoping the training you will be receiving is up to the task. If it is you will probably think again about this project.
Just PX your car and get a 40 or 62kw if you can afford it. Save yourself a lot of aggro.
Cheers Tony.
 

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Probably not internally, but see what the Muxsan range extenders can do. They know their way around Nissan battery packs, and Cleevely EV make use of the Muxsan kit to translate and allow battery packs to pair with vehicles that aren't expecting it.
 

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Still think a px is the best value you are likely to get.
If you are going to spend the best part of £5-6000 on a battery upgrade or replacement, just put that towards a px.
To me it's a no-brainer.
 
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Davey- do you have access to diagnostic rigs for EV's? Some of that equipment is bespoke (Not many sales so high costs) and very costly to calibrate and interpret results correctly. You really need to know what you are doing and take all the precautions when dealing with HV components that are capable of delivering high-current lethal charges.

I have spent most of my working life repairing and maintaining video projector systems that generate voltages of up to 35,000 volts - but these were with very low current supplies. I was always extremely careful when working on equipment, NEVER using 2 hands, always with one hand in our pocket as our lecturers drilled into us as students.

The sort of equipment in an EV is much lower voltage than I was dealing with, but it is the current that kills, not the voltage. In layman's terms, think of a current supply as the sheer amount of supply a source can deliver, a battery in an EV can deliver huge amounts. If you have ever shorted a lithium battery's terminals and seen the explosion and resulting fire, multiply that by many thousandfold from a Leaf battery and you get an idea of the sheer energy available to kill you.

I would not attempt such a modification, and I know a bit about what is involved, for a layman it is potentially lethal.
Indeed. The traction battery in an EV is absolutely deadly unless treated with respect - far more dangerous than directly touching 240v AC. (which I have accidentally done a few times in my life and lived to tell about it - it is not pleasant to say the least)

With AC the current stops momentarily and reverses 50 times a second giving a moment for you to regain control of your muscles and let go, (although it's still difficult) but a high voltage DC shock which is continuous current in one polarity causes your hand to clamp around a cable meaning you can never let go as the same polarity is constantly applied and the muscles simply will not release. (Never touch something with the open palm of a hand that could be live as it will tend to make the hand close around what you are touching. If you touch with the back of your hand a shock will cause your hand to pull away - not that I advocate touching anything that could be a shock risk of course!)

I did a cell swap in my Ion and had the pack disassembled on the floor in my garage but I was super, super careful with what I was doing and what I was touching and have a reasonable amount of experience of working with high voltages. Individual modules of 8 cells (on the Ion) are around 32 volts so safe to touch within that module once removed from the overall pack, but touching between still connected modules is a no-no. The high voltage safety disconnect in most traction batteries is located half way along the series string meaning that half of the maximum voltage (about 180 volts) is still available if you touch between the wrong places - still plenty to kill you. The safety disconnect only makes the outside of the battery enclosure safe to disconnect from the car, it doesn't make the inside safe...

As well as the shock risk there is a risk of short circuit. Drop a spanner across any cell or between any groups of cells and you'd better run and dive for cover rather than try to retrieve the spanner... :LOL: (It will be molten steel in a couple of seconds and probably spat molten metal and/or sparks in your face, soon likely followed by the cells energetically catching fire)

I do worry a bit about the average car DIY'er starting to dabble with EV batteries without enough knowledge and experience. I haven't heard of any deaths from this sort of tinkering by people not sufficiently experienced but I'm sure it will happen eventually. :(
 

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I've been jolted a few times over the years from brushing HaV to Ground when not paying attention! It's like touching an electric fence. Luckily, because it's only the capacitance between the HV system and ground, it's very little energy so it's only a brief jolt!

The safe DC voltage is <50V, or 12 cells/modules if fully charged. The biggest risk with shorts is burns and flying molten metal (safety glasses would be minimum, preferably a full face mask is better). However, normally there's enough energy in it that it isn't sustained. It's when there is water involved (coolant leak for example) that the risk of fire is greatly increased as it tends to be sustainable to let the cells get hot enough to start rupturing.
 

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Ok thanks for all your replies It was only a hypothetical question. I thought that the 30 pack had more cells , not the same amount with larger A/h hence the question I asked and no I am not an expert in this field .
I work for a lorry main dealer as a technician and am starting the training on full battery trucks next month. I would love to do a conversion my self but just weighing up costs. I think unless you are very skilled it’s probably not best to crack open a pack unless you know what you are doing!
Buying a 30kw battery and fitting a CAN bridge may be a better route to go - if you're comfortable with the safety precautions you'd need to take, and can handle the install of 270-300kg battery pack. 30Kw batteries are fairly easy to source, obvs it's important to locate one with good SoH. This would be a lot safer than opening up a pack, but also more costly.
 

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The EV course at work will certainly reinforce the risks of working with HV batteries - I’d imagine the trainer will be an Electrical lecturer from a college, and they’ve seen enough to drill the importance of safety into their audience!
 
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Discussion Starter · #16 ·
The EV course at work will certainly reinforce the risks of working with HV batteries - I’d imagine the trainer will be an Electrical lecturer from a college, and they’ve seen enough to drill the importance of safety into their audience!
yes I think you are right but they are keeping us in the dark a bit about how in depth the training will be !
All I know is they are spending a lot of money on a new part of the workshop which will have chargers etc
We have to have different colour overalls to show that we are HV trained and there is talk about having to work in pairs while working on the HV side of things. This is probably common practice in the car world but strange to me in the truck world.
 

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Yes - one guy will be holding a big sheep hook to pull you away if it goes wrong
 

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I think @muxsan take existing battery shell and replaced inside with newer ones.

While battery size is the same, there are differences in the communication cable interface and mounting points.

From what I know if Leaf all have 96 cells in series and capacity of what increases the overall pack capacity

@Dalathegreat might be the person to answer these are he replaces pack directly


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