Lithium replacement pack nearing market. Sounds great

Looking forward to what you find in regards to the voltages so I can get a better idea of just what voltage pack to build. I'd much prefer the bigger battery pack because it would give me more range because the minimum operating voltage is closer to the lower SOC of the cells, so not as much capacity is left in the cells.

T1 Terry

 

Well, looks like the LTO cells go into another project, they did write the silver Prius off but it was a statutory write off, that means it can never be re-registered in Australia ..... so no LTO battery build project ...... The wife won't let me take the taxi Prius off the road to do the project on it so it might be the VW Kombi or the Blade Electron V I bought recently

T1 Terry

 

Yeah, an update regarding the '06 Prius, they have reassessed the claim, I get the vehicle back and AUD$7,500 (less excess of course) So the LTO conversion is back on .... I'm a very happy camper

T1 Terry

 

I hope it works out!

 

I've been looking into LTO for both a 12V and a full hybrid conversion. Three reasons.

• Amateur radio operator. 6 cells in the 12V would keep the voltage up closer to the 13.5V that amateur radio tranceivers prefer. (12 Elerix cells may fit actually in a box that would fit in the battery compartment. That would be 60AH compared to 40AH stock lead acid, but would be over $600)
• Mountains. I drive over lots of mountains and having a way to absorb some of the kinetic energy would be nice. Like the Elerix (30ah over $4,000) or Yinlong (40ah, almost $7,000) cells.
• Cold weather. It gets down to well below 0°F (18°C) and sometimes as cold as -40°F (-40°C) although rarely these days. But LTO is apparently better at handling the cold than LFP. (Elerix rated at -40°C and Yinlong rated at -15°).

 

I started the strip out of the burnt NiMh battery pack yesterday, ready to install what ever battery combination I plan to experiment with and the 50Ah LTO upgrade would give me more storage that the latest Prius Prime @ 10kWh nom. using 6 cells per 2 modules (84 cells) and a fully charged voltage of 240vdc ....
but, if I use 7 cells per 2 modules it pushes it up to 98 cells, but that pushes the nominal voltage up to 235vdc and 280vdc fully charged and I'm not sure the Prius control system will handle that.
The LTO cells have around 90% capacity @ 2.8v to give a 90% SOC of 235v that is roughly 8.4v per modules or 1.4v per NiMh cell, 90% SOC the NiMh cell voltage is 1.5v and 9v per module so 252vdc fully charged .... but I've never seen that sort of rested voltage in my NiMh pack, but I have seen 242vdc quite often .... so ......

I reckon I'll start off with a re-hydrated s/h NiMh pack, then link 84 LTO cells @ 6 per 2 modules so it feds into the same place the Prius computer takes its battery voltage sensing ..... and see what happens then ...... If I get what I'm hoping to achieve, that'll do me.
If I was doing this the second time, I wouldn't use the 50Ah cyl cells, the size is a pain to work with ..... but if I have a win doing this, I'll get the little cells I want to experiment with next and build up modules using the series/parallel approach that can be better configured as far as capacity and shape goes .....

T1 Terry

 

I don't think resting voltage matters that much, but I could be wrong. To me it would seem best to shoot for a battery that falls between max and min, regardless of the exact resting voltage. I need to check my voltages again, but seems like I've seen over 18V per block during regen, but I don't remember by how much. The documentation I've seen online puts the absolute max battery voltage at 258.1V and absolute min at 174.7V.

I'm not sure if 7 per block (two modules) would be best as that would translate between 1.78V to 2.63V when perfectly balanced. 6 per block would be 3.07V per cell at max voltage if perfectly balanced. Maybe if the LTO didn't replace the NiMH but had 92 cells and connected to the terminals at the contactors??

As far as capacity goes, I think 30Ah should be enough. Depending on the amount of capacity that can actually be used, I need to assorb no more than 4kWh for downhill slopes. 30Ah x 201.6V = about 6kWh One mountain pass in particular is almost 1,000m rise and drop in altittude. The Prius is less than 1,500kg. 1,000 x 1,500 x 10 = 15,000,000 joules or watt seconds. Divide into 60 is 250,000 watt-minutes, then into 60 again and that's 4,167 watt-hours or just over 4kWh. Of course part of that will be lost to aerodynamic drag, rolling resistance, motor losses, inverter losses and battery losses. But if I could have at lest 2kWh of absorbtion, that might just do it.

What do you think of a 12V LTO battery? 5 cells seems a bit low and 6 seems a bit high to me.

 

You've yet to mention matching the power curve that hybrid battery ECU expects... And why go to all this effort to reinvent the wheel when projectlithium.com has already been perfecting this effort for a 1/2 dozen years?

 

I've heard that the cells used by projectlithium have been tested at low temperatures and have passed. But I've also been under the understanding that LiFePO4 cells will be damaged if charged at too low of a temperature. Seeing how I live in what most people call the coldest town in Colorado, with temperatures that can reach -40°F (-40°F) on occasion and usually reach at least -25° to -30°F (about -29° to -34°C IIRC) every year I'm concerned I'd damage the Project Lithium battery. I don't have a garage to keep it warm in.

If someone could point me to info on how to the Project Lithium battery performs longevitywise at those temps, if there are any BMS designs that were taken into consideration to prevent cold weather damage or if there's a solid garanty behind the battery that specifically mentions free replacement if there were damage even after driving around at those temps then I would buy one in a heartbeat when I get around to replacing this 15 year old whack-a-mole NiMH battery.

I was tempted to buy a 12V LiFePO4 replacement for the Avalon since my only other option was the OEM battery for nearly $350. But hearing how the cold kills LiFePO4 got me to worrying and I ended up going with the stupid lead acid OEM battery since lead acid can tolerate the cold clear down to -70°F, although they have to be fully charged in order to do so.

I'm not sure what the NiMH battery can handle, but they seem to work just fine in the bitter cold as far as longevity goes. I haven't noticed any drop in EV power or range in the summers after these batteries were driven in temperatures as cold as -40°F (-40°C) with no heated garage.

 

@PriusCamper
I noticed on the FAQs – NexPower Energy (projectlithium.com) page that the minimum storage temperature is -20°C for one month, -10°C for three months and ideally +15C. And that doesn't say what the minimum working temperature is. I wouldn't mind having some sort of heater, but it would need to be pretty fool proof. I'm open to ideas. I'm not saying one way or the other is the absolute way to go just yet. I just don't want to spend thousands on a battery that I'm going to kill because of my climate or driving habits.

 

You can review all their torture testing in the lab here: Hybrid App - YouTube

But in general, nobody is going to go out of their way to ensure product operation at -40' F because that's not where very many people live. I can tell you I winter tested this pack in my 2007 Prius in below freezing weather briefly into the teens 2 winters in a row and it was fine. And for those rare times you're gonna have extreme temps you're just gonna have to build some kind of simple ambient heating system for peace of mind.

 

Thank you! I'll look into it.

Even if it's ensured down to 32°F 0°C is better than 50°F 10°C. But 0°F -18°C would be even better.

I guess if I try LiFePO4 I'd start with the 12V battery. If I could make a heater for that battery that works then the question would be if it's feasible to upscale for the HV battery. After all, even a battery heater for the NiMH HV and the lead acid 12V batteries would be beneficial.

But pros and cons. A heater requires a heating source. Part of having a LiFePO4 battery for amateur radio is the benefit of having a lot of energy in a small package for emergency use when the electric grid is out. But if the electric grid is necessary for warming the LiFePO4 battery then that would be counter productive. Maybe in my case just sticking with NiMH may be the way to go.

 

It's like having a 30 year of advancement in your hybrid battery box with just one install with projectlithium... way more power up mountains and in EV mode when you get down to 3 bars... And you might want to talk to direct with them about what they'll warranty the pack for? Currently everything is going great and they aren't having to cover any warranty work, so you might be passing up something worth getting sooner than later.

As for 12v version, it's pretty easy, but requires its own BMS...

 

5 x LTO cells will give you a range of 9.25v to 14.25v ... well inside the 12v battery operating range in the Prius system.
Keep in mind, the LTO cells aren't limited to 2.85v max, they can handle higher, they just loose some cycle life .... but the short term the voltage would go over the 3v per cell would be very short.

Have you thought about adding a second set of NiMh modules and building a second battery with 28 modules in it .... 2 modules in parallel so actually 14 modules in one battery and 14 modules in the other battery for a total capacity 12.5Ah that have proven they can handle the job as far as temp and regen current.

T1 Terry

 

You're tempting me!

For me, all I know is I will not get some $600 refurbished pack. It's brand new OEM NiMH or ProjectLithium.

I dealt with a diesel car that needed preheating in order to start. Actually, I worked driving a fleat of diesel trucks with fuel fired pre heaters. Maybe a gasoline powered preheater would make sense to keep everything warm (including me) as long as I have a way of ducting the heat to where it needs to go (HV battery and 12V battery, for an example) The Prius heater just doesn't cut it on the coldest of days anyway. Then, for the rest of the year, I can benefit from things like the LithiumProject HV battery.

For amateur radio, the ideal battery would stay at 13.5V without going over 14.5V and no less than about 12V. LiFePO4's seem to do well at staying around their nominal voltage of 12.8V total up to near 0% SOC. I'm not sure about LTO's though. 2.23V x 5 would be almost 11.2V.

I have thought about adding a second NiMH battery. Cooling does come into play, as well as space. At the moment I am thinking that keeping the battery within it's current location and not too much bigger than that would be a good idea seeing how I have a wife and two teens and the amateur radio stuff, emergency bags, tire cable, etc. mostly fit in the tray as is.

 

When you say the tray, are you talking about the space under the floor above the wanna be spare tyre?
Just looked at my two Pri, one is a standard pack and the other is the bells a whistles pack, both gen 2, the full bells and whistles one actually has a spare tyre well that the standard model doesn't, so not quite as much space in the standard model ........
Cooling can be sorted reasonably easily and keep in mind, the modules will be working half as hard with the 2 in parallel, so heating isn't as big an issue as the standard set up.

As far as keeping the car warm, a diesels powered air heater works a treat, we have one in our motorhome because we don't enjoy being cold and cold to us is under 15*C :lol: but then we are built for 45*C days that sometimes turn into over 50*C, so we don't have a lot of insulation under the skin .....
The Chinese sell a really good unit cheap https://www.ebay.com.au/itm/255025681811?chn=ps&_ul=AU&norover=1&mkevt=1&mkrid=705-139619-5960-0&mkcid=2&itemid=255025681811&targetid=1278990506306&device=c&mktype=pla&googleloc=9112752&poi=&campaignid=10101784982&mkgroupid=129537798384&rlsatarget=pla-1278990506306&abcId=9300367&merchantid=116514809&gclid=CjwKCAiAgbiQBhAHEiwAuQ6Bkm1kPnUyO84fMOeduYGXxxdTZrJPuXMufax5OEs2yRWArrxcO2gPrhoCKZwQAvD_BwE but as this is evilbay Australia I'm sure on the US site it will be cheaper.
As you live in a cold climate, you would already have winter fuel diesel and that is what these diesel heaters work on best .....

T1 Terry

 

There were several startups before 2010 that added a second NiMH battery and successfully designed all the electronics to work without issue. You on rare occasion see a gen2 for sale with this conversion. But all those businesses went broke because Toyota said "great idea" and copied the design, which led to the first plugin Prius at a lower price point and better warranty.

As for the heating, I said ambient heating, which might not be the most accurate term but the idea is that heating method heats objects rather than the air. So easiest way to keep battery warm would be to put heating blanket coils on outside of the case. Perhaps some battery powered heated socks or blanket would address your concerns? Also ProjectLithium said they will give me $100 credit for every pack I sell, which means I'd love to sell a couple dozen so I can get earn my own pack that way. So when you're ready to buy hit me up and I'll share my affiliate link and in trade I'll provide tech support, mail you minor spare parts for free, whatever you need...

 

NiMH and Lithium batteries have very different charge and discharge characteristics. I would be reluctant to just drop a lithium pack in a vehicle with electronics designed to manage NiMH batteries. Not sure it would rise to the level of a fire (though it could), I would think it would certainly negatively impact the life and performance of the battery.

 

And what if someone like @jacktheripper dedicated a 1/2 dozen years developing the perfect lithium pack for old Prius and torture tested it in many, many ways and then you were part of the final winter testing efforts and put a prototype pack in your 2007 Prius 16 months ago and the pack has worked flawlessly with triple the distance in EV mode and triple the power when charge gets down to three bars on mountain passes? And after the first 1/2 year of these packs being sold across the country there's no issues with any of them yet... At that point would you continue to be reluctant? Because that's my view... As in there's almost nothing you can do to upgrade an old Prius, but this is one of them and I've no doubts whatsoever about performance.

 

Engineers do not design by trial anymore. This is the old style of build a brick building taller and taller until eventually it collapses. Then build the next one slightly shorter than that. Voila.

The math says this is a bad idea for some of all cases. For most cases, no issue. Automotive design is some of the most rigorous design environments outside of aerospace and shares a lot of similarities.