[scerbera]

Hi All,

So I am converting a VW T2 Bay Camper to electric by using all the systems from a 2011 leaf. My only real concern is as follows, the SOH of the battery is 68% if relevant, I do not plan to use this battery or more specifically the cells, but I do plan to use everything else, contactors, bms etc.

I intend to make a new pack out of 18650 cells, but I want to increase the capacity. I understand from watching the few videos there are on extender packs that the bms in conjunction with a current sensor will only allow a certain amount of power in or out. I would like to increase the kWh to approx 60/70.

I did intend for the bms to control all the cells in my new pack in terms of balancing and charging. Will this be possible, or will the bms only allow a max of approx 21kWh to be used?

Any thoughts or information you can give me on this unusal request would be most welcome. Thanks, Ryan.

 

[cah197]

Probably cheaper and easier to buy a load of Tesla packs where there are BMS and cooling solutions.

You'll need cooling for that size of pack, as well as temperature monitoring.

 

[scerbera]

Probably cheaper and easier to buy a load of Tesla packs where there are BMS and cooling solutions.

You'll need cooling for that size of pack, as well as temperature monitoring.

I already have the cells, I can make a pack easy enough, i am using all the leaf running gear, motor, charger, inverter, everything, except it's going to be in a different chassis with a larger battery. The questions in my first post are what I'm interested in. Thanks.

 

[cah197]

Well you'll need to get a different BMS solution. There are a number of options.

In terms of reverse engineering the charger, inverter, etc. Good luck.

 

[scerbera]

I don't think you understand, the car systems wont know any different, I will use the ECU from the Leaf, all the electronics, everything. I don't need to reverse engineer anything. I just need to make sure I can use a larger battery pack.

 

[whereswally606]

I am not wholly convinced that you need a new bms. The cell chemistry is going to be different to what's in the original aesc cells from the leaf but if you make the modules out of 18650's big enough then you might get away with the charging and discharging profiles being similar enough. Dala who uses Emile's mitm board helped a spanish company use LG1 cells to do that 64kwh leaf retrofit the other day so that the dash reported the correct miles left on the GOM, (it was worth noting that Mux (Emile was not best pleased with the quality of that battery in its mechanical design). I would be careful using 18650s especially without water cooling and even more so if they are just ones pulled out of old laptops. I.e. not the same beast as ones from tool packs. Anyway, where there is a will there is a way but please be aware of the risks.

Cool project by the way.

 

[Edd Beesley]

Hi All,

So I am converting a VW T2 Bay Camper to electric by using all the systems from a 2011 leaf. My only real concern is as follows, the SOH of the battery is 68% if relevant, I do not plan to use this battery or more specifically the cells, but I do plan to use everything else, contactors, bms etc.

I intend to make a new pack out of 18650 cells, but I want to increase the capacity. I understand from watching the few videos there are on extender packs that the bms in conjunction with a current sensor will only allow a certain amount of power in or out. I would like to increase the kWh to approx 60/70.

I did intend for the bms to control all the cells in my new pack in terms of balancing and charging. Will this be possible, or will the bms only allow a max of approx 21kWh to be used?

Any thoughts or information you can give me on this unusal request would be most welcome. Thanks, Ryan.

The Leaf BMS is not designed to work with 18650 cells. It does not have sufficient temperature monitoring and the cutoff voltages are incorrect. If you do as you're proposing (just disconnect the Leaf cells and connect some paralleled 18650s in their place) you will start a fire, destroy your vehicle, possibly your garage/house and injure or kill yourself or others. Don't do this.

 

[whereswally606]

@Edd Beesley I wondered this hence my "might get away with the charging and discharging profiles being similar enough", but i probably should have been more on the side of caution. I wonder whether he can run a separate BMS in parallel with the first which can monitor temps and increase the lvc, throwing a can message via the MITM to Stop Discharge and or Charge when there are issues.

Personally i'd rather not be messing with 18650s on a vehicle I maybe inside of (on ebikes you can hop off) especially if you are planning on sleeping in it.

 

[scerbera]

I am not wholly convinced that you need a new bms. The cell chemistry is going to be different to what's in the original aesc cells from the leaf but if you make the modules out of 18650's big enough then you might get away with the charging and discharging profiles being similar enough. Dala who uses Emile's mitm board helped a spanish company use LG1 cells to do that 64kwh leaf retrofit the other day so that the dash reported the correct miles left on the GOM, (it was worth noting that Mux (Emile was not best pleased with the quality of that battery in its mechanical design). I would be careful using 18650s especially without water cooling and even more so if they are just ones pulled out of old laptops. I.e. not the same beast as ones from tool packs. Anyway, where there is a will there is a way but please be aware of the risks.

Cool project by the way.

I understand the cell chemistry is different, i understand different charge and discharge profiles, but ultimately the bms reads voltage and resistance so it wont know any different. I have the 2011 leaf and full SOC reads 4.08V per cell and I get turtle mode at roughly 4.2/4.3.

SOC at 8% gives a cell voltage of 3.66 approx. However the car happily runs at 3.3v per cell which for full range if needed is where I could run the 18650 cells down to.

The 18650 cells will be well within their limit in terms of charging and discharging. I am aiming for 9600 cells in total. I am not concerned with there being an accurate display of miles remaining etc. All I'm concerned with is will the BMS allow me to use all capacity, and if not, how to work around.

 

[Edd Beesley]

No, it will not:

 

[scerbera]

Thanks Edd, I have watched that video, and the conclusion was that they need to route after the current sensor. I could in theory make 2 24 packs, one effectively as normal, one bypassing the sensor which may work, but I was planning for more capacity than that.

 

[whereswally606]

Hang on @Edd Beesley that's not what I was saying, yes that video is pretty sketchy but not what I was implying the OP did.

I think you could have a can-bus based BMS like the Orion and also have the leaf BMS also connected to the same pack. The Orion would need to be able to send a can message which could make the Leaf contacted disconnect when the temps went out of spec or the lvc was wrong.

I don't think that @scerbera is fully aware of the dangers of over discharging the 18650s so I don't think he should do it.

However I want to see hypothetically what is possible.

The other way to attack the problem is just spoof the leaf BMS can signals entirely and use and orion one to control the contactors and chademo charging. This is probably the safest approach and everything can be bench tested before ever being placed in a vehicle.

 

[scerbera]

Hang on @Edd Beesley that's not what I was saying, yes that video is pretty sketchy but not what I was implying the OP did.

I think you could have a can-bus based BMS like the Orion and also have the leaf BMS also connected to the same pack. The Orion would need to be able to send a can message which could make the Leaf contacted disconnect when the temps went out of spec or the lvc was wrong.

I don't think that @scerbera is fully aware of the dangers of over discharging the 18650s so I don't think he should do it.

However I want to see hypothetically what is possible.

The other way to attack the problem is just spoof the leaf BMS can signals entirely and use and orion one to control the contactors and chademo charging. This is probably the safest approach and everything can be bench tested before ever being placed in a vehicle.

What might I be missing here? I would if going for maximum range on this vehicle be looking at taking the cells no lower than 3.3v, this would be a rare occurrence and the aim would be to preserve cell health day to day. The maxmium draw on the cells would be 1c under full acceleration, normal driving would average 0.2c.

 

[whereswally606]

I have it in my head to never go lower than 3.6v when discharging but this is a remnant of the li cobalt RC chemistry so maybe not such a good reference to go by. I have however seen first hand an 18650 which was a brand new cell get shorted by a not so careful insertion into a weldless pack where a bit of metal welded itself between the positive and negative and it went up like a roman candle. Pretty scary.

Can you tell us what 18650s you intend to use and how you came by them? also will you be doing cell level fusing? Spot Welding or soldering? what enclosure are you intending to fabricate for the battery. These days VOSA check such things on the Single Vehicle approval that you need to go through to convert a van such as you are looking to do.

All credit to you though and I wish you the very best of luck but there is quite alot to this project you have proposed.

 

[scerbera]

I have it in my head to never go lower than 3.6v when discharging but this is a remnant of the li cobalt RC chemistry so maybe not such a good reference to go by. I have however seen first hand an 18650 which was a brand new cell get shorted by a not so careful insertion into a weldless pack where a bit of metal welded itself between the positive and negative and it went up like a roman candle. Pretty scary.

Can you tell us what 18650s you intend to use and how you came by them? also will you be doing cell level fusing? Spot Welding or soldering? what enclosure are you intending to fabricate for the battery. These days VOSA check such things on the Single Vehicle approval that you need to go through to convert a van such as you are looking to do.

All credit to you though and I wish you the very best of luck but there is quite alot to this project you have proposed.

Sure, I have some options for the cells, I have started to buy 90% Samsung 29E cells, but I may switch to BAK ev cells, i have some arriving soon for testing capacity and discharge profiles etc. The Samsung cells I have tested are looking most likely and very happy with them.

I intend to construct a new tubular chassis to replace the camper chassis which has had it anyway, this will allow for a central tunnel in which i will house the cells. They will be made into the correct size packs and I'm still finalising the exact packaging but probably 10 * 9s packs with one 6s. Each one will be housed in a metal enclosed case, then bolted up into slot, with further covers. The batteries will be held inside either a printed holder or similar. I intend to have fusing i'm not 100% to what level as yet in terms of will it be each individual cell like the Tesla packs or a fuse on each parallel section, or if it will be on each block.

I have made a number of typical cell packs so have a spot welder, but i want to avoid nickel in the pack if at all possible. I have a novel design for the negative side of the cell which I will test soon, and most likely run individual cable to each positive cell top, and from there to a busbar within the module.

I intend to do this in a professional manner, I have an engineering company, cnc etc, so construction of these sorts of things is the easy side for me. I have only recently learned of this power limit with the leaf BMS which is annoying so I have to figure out my way forward on that front.

The camper will not really be a camper as such, it will be a 7 seat family run around as I have child 4 on the way, we have a leaf at the moment and we enjoy driving it but it's so small and I don't want to spend 70k on a model X!!

 

[Hairy Leafer]

erm given a brand new Leaf of that age could only just eek out 100 miles in perfect weather on a full charge and what you have now has a SOH of 68%... How far are you expecting to be able to travel?

I know you said you would like to increase capacity to 60-70 kWh but to do that you would need another 2 full leaf leaf battery packs in a similar state of health. Unless Im missing something you are going to end up with the worlds heaviest samba bus with severely compromised packaging

 

[scerbera]

erm given a brand new Leaf of that age could only just eek out 100 miles in perfect weather on a full charge and what you have now has a SOH of 68%... How far are you expecting to be able to travel?

I know you said you would like to increase capacity to 60-70 kWh but to do that you would need another 2 full leaf leaf battery packs in a similar state of health. Unless Im missing something you are going to end up with the worlds heaviest samba bus with severely compromised packaging

I won't be using the leaf battery. I'm not sure you have read the posts.

 

[Hairy Leafer]

I won't be using the leaf battery. I'm not sure you have read the posts.

apols
as it happens eye sight test already booked next weekend..

 

[Aragorn]

Why try to retain all the LEAF electronics? Fit a custom controller to the inverter, there are plenty of options, and use a standalone BMS thats actually upto the job. Will be far simpler and wont require you to shift huge amounts of LEAF parts over.... that just adds huge complication for what gain? Espeically when your changing the battery so drastically.

 

[scerbera]

Why try to retain all the LEAF electronics? Fit a custom controller to the inverter, there are plenty of options, and use a standalone BMS thats actually upto the job. Will be far simpler and wont require you to shift huge amounts of LEAF parts over.... that just adds huge complication for what gain? Espeically when your changing the battery so drastically.

Thanks for your reply, what options spring to mind for what you have suggested?