'06 Prius battery upgrade to LTO 55Ah cells

I bought my '06 Prius from Jason from Oz a few yrs back. It had extensive modifications already, including the Enginer plug in battery set up, 74 x 40Ah LFP cells that topped up the NiMh battery as required until fully discharged.

After an unfortunate traction battery fire that was of my own making, the vehicle was an insurance financial write off and I bought the vehicle back from them.

I've finally started the Yinlong 55Ah cylindrical cell battery upgrade. The objective is the build a high capacity traction battery that will work with the original Prius equipment ..... time will tell if I'm dream or not .....






The dry powder from the fire extinguishers doesn't do the average vacuum cleaner a lot of good, even the workshop H/Duty units had a hard time with it.




This was the first layout idea, all 84 cells would fit and there would now be some room above the battery to carry the spare wheel, jack and charging cables, that was all lost with the Enginer kit battery.

The downside of this arrangement was only utilising part of the spare wheel well and only around 36 cells over the rear axle, the rest behind the axle.
I know this is better weight distribution than the Enginer set up, but I wanted more :lol:



This arrangement puts 48 of the cells standing up over the rear axle and the remaining 40 cells will be mounted in two layers 2S10P in a box where the spare wheel well was originally. This will give me the whole floor available to build a box to carry the spare tyre, jack, charging cables and a lot of other gear while still having a flat floor at the rear.

T1 Terry

 

Fortunately my maths isn't all it could be, if I fit 40 cells under the floor I only need to stand 44 cells up where the original traction battery was .... I say fortunately, because I realised unless I mount the pack a bit more towards the rear of the vehicle, the seats would hit when opened up .... Removing 2 cells from each side gives me plenty of room and still the required 84 cells.

T1 Terry

 

Thank you, at least this means someone has read it :lol:

T1 Terry

 

This was yesterdays effort, sure doesn't look much for a whole day, but I had already made the base for the 48 cell, so I had to modify it .... that at least accounts for a bit of the time



T1 Terry

 

I've started welding the aluminium tread plate box for the top battery pack ..... mig welding aluminium isn't like riding a bike, it doesn't take long to loose any finesse I might have had, then again maybe my memory is painting a better picture of what my welding looked like in the past :lol: Wish I could TIG weld aluminium, but I shake so bad I wouldn't be able to keep the tip out of the weld pool ....

T1 Terry

 

I'm about half way through welding up the top battery box. Haven't decided if it will be the base with a lid, or the cover with the cell mounted to the base and the cover bolting down onto the base.
I'm certainly not going to post any of my welding effort photos, I'm even thinking of locking the doors so no one can come and and see any of them before I can clean them up a lot with the grinder. The floor around the bench looks like it's been snowing aluminium .... if my welding is going to improve with practice ... it seems I need a lot more practice
Between aluminium pigeon droppings attempts, I've been trying to figure out how to do the cell links, get enough spacing so to terminals don't come into contact with the aluminium box and not suffer any damage from bouncing around on the base of the box. Looks like lots of stainless all thread 5mm rods required, just gotta figure out how to anchor them to the base because I don't want to drill holes ..... at some stage I want to try flooding the box with "E fluid" to act as a coolant while protecting the connections from the air to stop oxidisation ..... my crap welding is requiring a lot of rewelding in an attempt to make it oil tight .... even harder than water tight because oil will creep through the smallest pin prick

T1 Terry

T1 Terry

 

Yes, a hybrid PEV that can charge from the fast charger networks being rolled out and the ultimate aim is to be able to use the DC ultra-fast chargers.
Once I get that all working, the next aim is to replace the ICE with an electric motor to simulate the ICE spinning the planetary set so the 80km/h (50 mph) limit the limp home mode has can be eliminated because MG1 will no longer go into over speed.

The other aim is to increase the regen capacity so the traction battery doesn't reach its max capacity on the run down a long hill. Maybe by incorporating regen on the electric motor that will replace the ICE, the B mode can be used for added regen braking where needed.
The fact an electric motor uses less current when spinning fast than an ICE uses fuel, that "scream my tits off" mode the ICE goes into when climbing a hill will no longer be a mode to try and avoid.
Lots of plans for the extended project, but just at the moment, simply building the first battery box is eating up all my spare time ..... partly because my welding requires better eye sight than I seem to have at the moment .... once the cataracts are done, that should improve.

T1 Terry

 

I've read all the posts about how great the LFP cells are, so you must be mistaken :lol: Out of interest, what capacity cells and how long did the last?

T1 Terry

 

I read on another thread from yrs back, that the bloke pressurised the cell through the hole he drilled to re hydrate the battery and it took over 120 psi to get the relief valve to finally vent. After that it was back to 80 psi.

My plan, that I haven't actually tried yet mind you, was to drill a hole each end of each module and tap it with a 4mm thread. Then, using those irrigation hose fittings, extend the tube on one side to the bottom of the module and the other side just the standard plastic nipple. Glue them in with T Rex adhesive that sticks to everything and creates a very strong bond.
Next, run a hose from each nipple, the one at the upper level of the module to one tank and the one with the extended piece going to the bottom of the module to a second tank.
The tank feeding the upper part of the module is mounted slightly higher than the other tank, but the top of the second tank comes about half way up the higher mounted tank.
Run a balance pipe between the two tank, but high enough up so the rubbish from the modules doesn't enter the balance tube but rather settles on the bottom of the tank.

Now fill the higher tank with KOH and it will siphon through the modules pushing the excess out the tube in the lower part of the module, flushing out any rubbish.
Slowly the air in the top of the module will escape back up the inlet hose, being flushed out each time the module pressurises, then the module will refill when the pressure drops.

This will keep the modules full and end the over pressure problem that causes the leaking terminal posts.

The alternate version was the very carefully drill a hole in the depression beside the vent tube and tap a ... 6mm I think it was, fitting into the threaded bit and run the tube to a tank full of KOH to allow the trapped air to escape and KOH to refill the module. This idea doesn't flush the rubbish out of the module, but at least it addresses the over pressure and dehydration issues.

T1 Terry


EDIT: Just a foot note, if you want to go the drill a hole in the depression method, be very careful how deep you drill, if you go too deep and hit the cell plates the cell shorts out and goodbye module

 

Finally finished welding up the box, went to put it in place and bolt a back seat in to see how it looked ..... that great Aussie-ism. yeah/nah ... too tall so it needed to be leaned backwards to follow the angle of the eat back .... looked ok with the seat up, but when it was laid out flat, too tall to look halfway acceptable .... start again, back to the first idea and see how that looks with the extra cells in the now modified wheel well.

T1 Terry

 

Idea number .... lost count actually :lol:
Pack 1 : 3 cells high x 3 cells long x 2 cells wide to fit between the rear seat mounts and the rear strut pillars.

Pack 2 : 3 cells high x 2 cells long x 1 cell wide to fit between the rear strut towers

Pack 3 : Same as pack 1 but mounts behind the rear strut towers.

That adds up to 42 cells roughly in the same position the original traction pack was, the other 42 cells to go in the hole I made by cutting the wheel well out.

Here is a photo of pack 1


How annoying is it when you get the pack together and then realise you don't have any way to connect the sense wire to monitor cell voltage or balancing ......
It has taken 3 days to get to this point .... at least all the 12mm stainless nuts are welded to make the cell links and the threaded terminals on each cell are cut down to size, so I won't have to repeat those bits Also, I found a better method for spacers between the cell racking so I don't have to run the 5mm rivnuts and 5mm nut between them on the next assembly ...... but I do have to unscrew them

T1 Terry