Battery replacement cost, £15,000!!!

[Caddyshack]

annodomini2 said:

kambites said:

annodomini2 said:

The issue is the business needs to maintain stock of batteries.

Given new ones are £20k, a 2nd hand one will be £5-10k as they are still usable for grid storage.

Keeping a stock for all the different cars with all the different variants is not going to be cheap.

Swap is more convenient for the customer, but expensive for the business, so unlikely.

I was referring to fixing broken, rather than degraded, packs. A broken pack has no immediate value until it's fixed so whoever reuses it for whatever they reuse it for needs to at least hold it in stock for long enough to fix it!

I guess whether it's better to swap the packs over or repair the customer's own will depend on the time it takes to replace a module in the pack once it's out of the car. Companies wont want to hold too much expensive stock, but there will be a significant competitive advantage to being able to fix a customer's car in one day rather than having to hold it for several. Even if the mechanical side of fixing a pack isn't too long-winded, re-balancing a pack from scratch is a pretty slow process.

It used to be very common to buy refurbished components on an exchange basis, at least in classic car circles. No idea if it still is.

Edited by kambites on Saturday 29th January 10:45

To begin with, the repair companies will probably offer to dismantle and replace the defective cells. Assuming they can get parts and with the associated delay.

Most EV batteries are modular, as time progresses, EVs become more common and age, parts will become more readily available, at that point they'd probably keep a stock of modules, as it would be unlikely that all modules are dead.

So for a repair they'd replace the defective module(s) and repair those removed, to speed up the process.

Why is re-balancing a pack a slow process? I thought most multiple cell packs balance at the end of most charge cycles, wouldn’t it be just an hour on an intelligent charger?

[kambites]

Caddyshack said:

Why is re-balancing a pack a slow process? I thought most multiple cell packs balance at the end of most charge cycles, wouldn’t it be just an hour on an intelligent charger?

They do re-balance at the end of charge cycles and it's generally quick because the cells are already very close to being balanced. When you install new cells into an existing pack, everything is way out of balance so it takes longer. You could just shove the new cell in and let it self balance, but that would mean the new unit was either being over-charged or over-drained until the gradual bleed balancing built into the pack can sort it out (which would probably take months if there's a big discrepancy.

I think (I'm not an expert in these huge packs, I work with much smaller ones) the correct approach would be something like to fully charge the car, let it re-balance itself, then allow it to drain at steady load down to below about 50%; charge the new module off-car to about the same level the car is now at; install it then recharge the whole car to 100% and let it re-balance again. It still wouldn't be perfect but it should get you fairly close.

Someone who actually works on big battery packs might be along in a sec to shoot down that down in flames though.

Edited by kambites on Sunday 30th January 10:28

[anonymous-user]

kambites said:

Caddyshack said:

Someone who actually works on big battery packs might be along in a sec to shoot down that down in flames though.

Flame thrower at the ready.... ;-)

Actually, you are not wrong, the BEST approach is to do just that, the ensure the SoC of any new cell or module is within about 3 to 5% of the originals, then install it, and to do a couple of slow (7kW max single phase ac counts as slow, in fact for most pas cars, probably anything less than about 50kW is slow in reality) charges an run the battery to nearly empty to allow max balancing time and the SoC / SoH prediction to home in on the right numbers

But:

Assume you are talking about a series module being changed, which is most likely in most battery architectures (and not a parallel one, that really needs to be within say 100mV or so of the rest before being connected), then you could just stuff in the new cell/module at practically any voltage, and the BMS will simply call time when that cell/module is at max or min voltage. That will limit the total energy you can charge with, but most batteriey balancing can nullify around 1% imbalance in a few hours, so it won't actually take that long for the pack to regain its balance passively so to speak

[anonymous-user]

Caddyshack said:

A good merc specialist could rebuild an engine for a fraction of the dealer price…not sure what you can do with a fubar battery?

An modern ICE engine is extremely complex, has hundreds of very finely machined and tolleranced parts, that must be carefully assembled with the correct sequencym tools, torques and in a suitable clean environment. To even remove and replace that engine means the disconnection of a huge amount of wiring, and plumbing.


A modern BEV battery is a collection of cells, stuck in boxes and bolted down. Most modern batteries just need a 13mm spanner to completely tear them down. No parts require precision alignment or special tools, and a spec of dirt or grit that would render the main bearings in your rebuild ICE scrap in short order will have no effect.


So, if you can today find a "good" specialist to rebuild your (massively complex) engine, then you will clearly be able to eventually find a specialist to repair your battery. The reason you can't (outside of a couple of existing entities) is simple, there is no demand for this service. Not many BEVs are out there, and those that are are very reliable on average. But as more and more are sold, and existing older BEVs age, then these specialists will increase in demand and hence availability........