DIY HV Battery upgrade

[Joff]

We know BMW can swap out a 60ah pack for a 92 ah pack and make it work. There is a lot more to it than just removing one and installing the other. The vin number of the new part has to be entered, among other things. As far as I can tell, no one has done it without BMW help. What you you think would happen if you just swapped out the 60 ah cells with 92ah cells? As I understand it, 12 cells are glued into each of the 8, 48v modules. Each module has it own bms. if the 48v bms can be removed from the 60ah modules, you could put them on salvage 92ah modules, and put the battery back together with 92ah modules. I don't think the bms could tell the difference...same voltage range per cell, right? Batt Kappa is calculated, so I think it should be able to figure out how far it can go eventually. I haven't found specs on the 60ah cell and what the voltage the bms considers max charged and discharged.

 

[i3Houston]

Definitely sounds feasible on paper! Maybe an electrical engineer can shed some light.

 

[ronbot]

While in most consumer-scale applications, this may be viable, but EV-scale BMS could very well have original capacity stored in memory... even if for no other reason than to set a hard limit on charging capacity... over-charging cells this size results in very bad events...

 

[Oleksiy]

At least it's being done in Leafs on almost industrial scale by third party workshops in Ukraine, and with great success. There are plenty of reports on Youtube. Haven't seen anything re i3 though.

 

[Joff]

My understanding of a typical lithium bms is that overcharging is prevented by limiting the cell max voltage and tapering off the charge current as full charge is approached. It shouldn't have to keep track of how many watt hours have gone in as long as the voltage and temperature remains within specs. Not quite ready to bet $5000 that I am right though!

While in most consumer-scale applications, this may be viable, but EV-scale BMS could very well have original capacity stored in memory... even if for no other reason than to set a hard limit on charging capacity... over-charging cells this size results in very bad events...

 

[jadnashuanh]

Logic to determine time to full charge and distance to empty estimates likely would need to be tweaked in order for them to be accurate. This is also tied into the logic used for the nav system, but fixing one, may fix all of the parameters for all functions...one of those things you'd probably need to dig into further to verify and resolve.

 

[Joff]

I figure time to full charge and distance to go are calculated, as those numbers will change as battery holds less Ah over time. I would be ok if got the extra range but it told me I have the standard range. It might trigger some sort of error if the charging system registers a given number of kwh going in to the battery but the rise in battery voltage is less than it expects because the cells can hold more. I also wonder if the bmw connected drive will alert bmw of any weird/abnormal readings if make changes. Oddly enough I am more worried about messing with the air-conditioning system than making changes to the battery. I have no experience in air conditioning and the I3 has an expensive one!

 

[3pete]

My gut is thinking the same thing as you, Joff; it would either take extra work (programming a check to see that it's a 60ah battery or setting a max/min range for ah on the battery) or 'shortcuts' (hardcoding a battery capacity value) for BMW to check whether the car has been retrofitted with a different sized battery since they do have to handle capacity differences based on normal variations in temp, battery age etc. My battery is significantly different from new and I think the navigation system accurately represents my car's condition, so I'm inclined to say it's not a hard-coded value.

Also, it is definitely possible to retrofit a bigger battery to the i3, but this doesn't specify what else besides the battery was changed out so it doesn't help with those 'minor details'.
https://insideevs.com/news/339632/this-bmw-i3-goes-435-miles-per-charge/

All this is to say I support your idea to upgrade the HV battery. If you do it and it works, that gives me more ability to do it down the road should I choose to!

 

[EVMan]

Yes, surely the software configuration on which the BMS relies will need to be adjusted to make things work properly.

Also note the battery chemistry is changing with each generation , so the charging , discharging characteristics and curves also change.

All in all, the best Evs are the most optimized once

And without software configuration and specific firmware's which were tested, it may not be even compatible.
It can be a danger too.

 

[EVMan]

At least it's being done in Leafs on almost industrial scale by third party workshops in Ukraine, and with great success. There are plenty of reports on Youtube. Haven't seen anything re i3 though.

Did Nissan not say , that the batteries are not up-gradable.
The 24kwh cannot be replaced by the newer 30KWH.

The official new batteries of Leaf are very cheap upgrade . i think i heard $5000 for the 24kwh
Considering there r so many Leafs around and they are cheap , due to poor batteries,.
If they are up-gradable , they become good buys

 

[jadnashuanh]

In some markets (not the USA), BMW offered a battery upgrade. Why, or potentially when it is offered here, it should end up seamless to the user. Whether it will be cost effective remains to be seen. At least in the US, the cars depreciate pretty fast, so making the investment for a new battery might not be sane. Probably good for the environment, but maybe not for your pocketbook.

 

[i3Houston]

In some markets (not the USA), BMW offered a battery upgrade. Why, or potentially when it is offered here, it should end up seamless to the user. Whether it will be cost effective remains to be seen. At least in the US, the cars depreciate pretty fast, so making the investment for a new battery might not be sane. Probably good for the environment, but maybe not for your pocketbook.

Nissan was selling it for Leaf, until they stopped. Maybe they stopped because they sold their battery factory. I believe the battery replacement cost was about $5-$6K which was not a lot IMO but I dont believe manufactures care anything beside $. Battery replacement, IOW, giving second life to the car is less profitable then selling a new car so they are not doing it.

BMW claimed that i3 battery packs are upgrade able but they have not offered nothing and that is so sad. Unless something changes, this would be my last BMW.

 

[Oleksiy]

At least it's being done in Leafs on almost industrial scale by third party workshops in Ukraine, and with great success. There are plenty of reports on Youtube. Haven't seen anything re i3 though.

Did Nissan not say , that the batteries are not up-gradable.
The 24kwh cannot be replaced by the newer 30KWH.

The official new batteries of Leaf are very cheap upgrade . i think i heard $5000 for the 24kwh
Considering there r so many Leafs around and they are cheap , due to poor batteries,.
If they are up-gradable , they become good buys

Nissan could have said anything, people in Ukraine are trying anyways, that's just how things work here. And they've been successful in upgrading from 24 to 30 kWh (https://www.youtube.com/watch?v=XHLddeIxxig). BTW, these guys even tried going from 24 kWh to 40 kWh, but failed - the car drove only in turtle mode.

 

[3pete]

Yes, surely the software configuration on which the BMS relies will need to be adjusted to make things work properly.

Also note the battery chemistry is changing with each generation , so the charging , discharging characteristics and curves also change.

All in all, the best Evs are the most optimized once

And without software configuration and specific firmware's which were tested, it may not be even compatible.
It can be a danger too.

Honest question: what part of this do you consider to be unaccounted for in the existing firmware/ software optimization that handles changes in climate, driving style, and battery degradation?

If your i3 can handle a batt kappa max at 13.8 instead of 18.8, why wouldn't it be able to handle 36.0? Again, legitimate question, and I think it comes down to how BMW designed the i3's software and electronics. The way they originally advertised it catering towards 'sustainability' makes me think they were thinking about eventual battery replacements and how to make it easiest for themselves to do it. Maybe I'm giving them too much credit though...

 

[Obioban]

https://www.youtube.com/watch?v=L6DVQnHQHPM

 

[Joff]

The main reason I was lookin into this, was that there was a 94ah HV battery for $5000 for sale Another seller was selling the individual 48v modules for 800$ each , which is still less than the 7 to 9k these used 60 ah and 94ah batteries are listed at on ebay. They don't seem to be actually selling at that 7-9k price, but there they are.

 

[i3Houston]

7G plus labor. Maybe reselling 6,Ah battery can cover portion of the upgrade cost.

But is this something you can diy it?

 

[Joff]

7G plus labor. Maybe reselling 6,Ah battery can cover portion of the upgrade cost.

But is this something you can diy it?

Only one way to find out! It seems someone in Germany upgraded a 60ah to 120 outside of BMW and posed about it on a EV site. wish I could read German! They paid 15k euros, so I don't think it was DIY
https://www.goingelectric.de/forum/viewtopic.php?f=71&t=51220&fbclid=IwAR06ri82nHmb3cBgCfEkggClITevziks7DobhLg80GEJRvBhXsD70AeeCSc

 

[i3Houston]

That sounds like one off custom job! Not practical for most on general

 

[Anonymous]

$16,500 for a battery upgrade is a little pricey

I didn't pay much more for my 2015 fully loaded Tera World lease-return with 9,600 miles on it a year ago.