[Clueless Gearhead]

Hello,
I'm a new member, and I've been doing some random amateur research here and there on EVs. Being also an amateur RC hobbyist, I've been exposed to the theoretical capabilities of Lipos in a larger scale setup. Which leads me to the question:

Would it seem feasible/reasonable to use Turnigy Graphene RC lipos (https://hobbyking.com/en_us/batteries/turnigy-graphene-batteries.html?dir=desc&order=capacity) for an everyday driver setup?

I am well aware of a previous thread about using regular RC lipos for an EV (http://www.diyelectriccar.com/forums/showthread.php/turnigy-lithium-polymer-battery-evi-131970.html), so I know one of the first objections will be "RC lipos do not have a long enough life cycle". However, these "Graphene" lipos have been tested to up to 900+ cycles on them w/o any loss in capacity (https://www.rcgroups.com/forums/showthread.php?2592234-Turnigy-Graphene), so in my mind they seem like a plausible solution to the whole dilemma of lower lipo cell life.
Any comments? I couldn't seem to find threads that had already discussed this, so if there was already previous info on the topic, that would be great to see.

Keep in mind, this is not a project I am actually building, just a curious thought, so I have no specifics on an actual application.

 

[goingbush]

I'm also into RC , have converted fully Electric now from gas /glow

Those Turnigy Graphene batteries are good but still way too expensive , as are even ordinary RC Lipos. BMS system is going to be a major headache too, the batteries will need disassembly and cells hooked up in parallel banks then the banks in series.

900 charge cycles is fairly medoicre, my LiFePo4 cells are quoted at 3,000 but my research suggests they will be good for 10,000 cycles if not fully charged /. discharged .

 

[Clueless Gearhead]

I'm also into RC , have converted fully Electric now from gas /glow

Those Turnigy Graphene batteries are good but still way too expensive , as are even ordinary RC Lipos. BMS system is going to be a major headache too, the batteries will need disassembly and cells hooked up in parallel banks then the banks in series.

900 charge cycles is fairly medoicre, my LiFePo4 cells are quoted at 3,000 but my research suggests they will be good for 10,000 cycles if not fully charged /. discharged .

Ok, so I see your point there.

Suppose hypothetically that those graphene cells were not chunked together the way they are, and that cost was not a concern. Could it still be "reasonable" to run a rig with T. Graphene? I understand the arguement for LeFePo4, and I am in complete agreement that LiFe may be the best overall chemistry for EVs, but suppose we were to compare these Graphenes to, say, 18650 cells? Would lifetime still be too limited? Again, just curious, and hope I'm not being a pain in the gluteous maximus with my insistence on Graphene.

 

[Clueless Gearhead]

Ok, so I see you point there.

Suppose these T. Graphene were not chunked together the way they are and were separate cells, and cost was also not a concern. Could it still be reasonable to use these cells in a setup like this? I understand the arguement for LiFePo4, and I agree completely. However, I would like to compare them to something more like, say, 18650 cells, in terms of life time. As far as performance goes, I'm sure we can both agree that lipos are possible the best bet for power-weight reasons. I'm just curious about how long these "improved" lipo structures will last in comparison to already well-established li-ion chemistries. And sorry if I'm being a pain in the gluteus maximus with my insistence on T. Graphene.

 

[Clueless Gearhead]

I forgot to add, also suppose BMS was not a concern either

 

[Karter2]

RC lipo has a poor reputation for safety.
Primariy fire risk as the electrolyte is highly flamable and the foil pouches are fragile, easily damaged, and quality control is not at the standard of proprietry EV cells.
However , RC lipo has been used for performance EVs where maximum power density is of primary concern, and safety can be monitored.
Check the Ampaholic site and John Metrics "Panic in Detroit" threads etc

 

[e^2]

I ran through this calculation before. The problem I saw was to get a 60kwhr pack you'd have to buy a ton of them (cost) and weight as these style of packs are more designed for max output than runtime. The only plus side is you would have a 60kwhr pack with an 18 megawatt output capability!

For a 120V rail you would need 30S (30*1.3Ahr cell is 39whr per string). You would then need 1538P to get 60kWhr. At 75C that is 1.3*75*1538, or 150,000A peak. Multiply by the 120V rail gets you 18MW output...

Check my math, did I do that right?

 

[Clueless Gearhead]

E^2, what specific packs did you use for reference? I see you used 1.3 ah packs, but how many cells per pack? I also was thinking of using a pack of lower power rating, with 12ah cells with 15c continuous discharge. These were in 6s configuration. At 399.6 battery volts and 216ah (18p), we're around 86 kwh. That is a fairly bulky and heavy pack, I know. I see why now why no one has really taken the leap towards using this kind of li-ion for a track performer that doubles as an everyday driver. I knew standard lipos did not outweigh overall practicality of other chemistries, but I hadn't imagined Graphene still didn't offer enough to fill in that gap. Now I do.
So as I'm seeing it now, although Graphene seems pretty good on paper with a longer life than standard lipo, it is still not advantageous enough to double for a street car. That seem about right?

 

[goingbush]

have you seen this

https://youtu.be/9CDzrDjBTNU

 

[Karter2]

E......I see why now why no one has really taken the leap towards using this kind of li-ion for a track performer that doubles as an everyday driver. I knew standard lipos did not outweigh overall practicality of other chemistries, but I hadn't imagined Graphene still didn't offer enough to fill in that gap. Now I do.
So as I'm seeing it now, although Graphene seems pretty good on paper with a longer life than standard lipo, it is still not advantageous enough to double for a street car. That seem about right?

What sort of "track" car are you thinking of ?
EVs are a long way from being useful as a circuit car, weight and capacity (range) are major issues.
But for Drag tracks, an EV makes a lot of sense , hence the links i gave above, but again , a good drag car doesnt make a good street car. A Small RC Lipo pack can work well in a drag car giving high power and light weight from a small capacity pack...good for a couple of runs down the strip, but not enough capacity to drive to the track !
But graphine doesnt bring much to the party from a drag race point of view.

 

[Clueless Gearhead]

Sorry, I didn't clarify what I meant by "track" car. I meant the drag strip, not an actual winding track or oval or something like that. My mistake.

 

[brian_]

Sorry, I didn't clarify what I meant by "track" car. I meant the drag strip, not an actual winding track or oval or something like that. My mistake.

Not a mistake, just some missing detail. Thanks for the clarification.

While drag racing is a natural home of racing EVs with current battery technology, autoslalom/autocross is a good match, too - there are couple of forum members in this type of competition.

 

[Clueless Gearhead]

So that being said, what chemistries would you place in life longetivity from greatest to least (I'm sure LiFePo4 will be 1st, lipo and/or lead acid dead last). If possible, actual life cycle numbers, rather than years or simply "X chemistry lasts better". Thanks!