LiFePo batteries

WarpedOne · 08-18-2008, 03:19 PM

Today I was dedicating my usual daily WOMBAT (Waste of Money, Brain And Time) into trying to "reverse engingeer" Venture One or construct an all-electric tilting trike using parts available online. While searching I came accros Thunder Sky Energy Group. This company is building large format LiFePo bateries and also some end products - electric scooters and buses.

Between their products I found TS-LFP260AHA. This is a large format LiFePo pack with 260Ah capacity at 2,5V - 4,25V (empty - full).

Now, take 48 of them and put them into series. You get 53kWh pack that weighs 400kg (800 pounds or 100 pounds less then Roadsters ESS). It's voltage would vary between 120V and 204 V. The pack is rated at 2C constant discharge, meaning this pack is capable of 520A of constant discharge current (for 30 minutes) giving 106kW (full) - 63kW (empty) constant power. But its peak discharge current is rated at 10C giving 530kW (full) down to 312kW (empty) of max power.

Smaller 90Ah pack retails for 220 USD at Electric Motorsports so I guess this larger 260Ah pack sells for around 600 USD. This superpack would thus cost around 28k USD.

Where are the benefits in comparison to current Tesla's ESS?
- lower weight (100 pounds less) for same capacity (53kWH)
- lower complexity (no or less cooling required, even less weight?)
- much longer lifetime (manufacturer claims 3000 recharge cycles at 80% DOD and even 4000 cycles at 70% DOD)
- much higher peak power (from 300kW to 500kW )

Downsides?
- somewhat more expensive upfront but it should have 6 times longer lifetime: 100.000 miles for 20k USD (ESS) in comparison to 600.000 miles for 28k USD. If measured in cost per driven mile it becomes 20 cents/mile for ESS and 5 cents/mile for this LiFePo pack.
- manufacturer tie-in

It is nice to see technology marching on.

TEG · 08-18-2008, 04:43 PM

If you dig enough into ThunderSky you will find some sordid tales of "group buy" home brew EVers who felt they got burned by problematic product. Maybe ThunderSky has improved since then, but still you want to do "due diligence" on them before spending real money on their products.

Some of the customer dissatisfaction was portrayed as "poor manufacturing and quality control" (not unheard of from bargain Chinese made products), and some was kicked back as "the batteries were mistreated by the customers".

To have any chance of long term reliability with these batteries one has to provide a proper BMS (Battery Management System) that provides individual battery balancing functions and avoids over charging or over-discharging any of the individual batteries. If you just string them together in series and charge them as a group unit then you are likely to get cells out of balance and have short lifespan. I have also heard that the batteries need to be physically contained in some sort of rigid battery box. If you let them expand and contract it may also shorten their life.

Here was a prototype eBike with Thundersky LiFePo batteries just hanging off the chassis:

another:

The main advantage of LiFePo over the cells Tesla uses is that they are resistant to thermal runaway so you don't need all the safety systems Tesla uses.
The downside is they don't have as good an energy density so you end up needing more volume of batteries for the same kWh.

Some more:
Real World Thundersky Discharge Specs - DIY Electric Car Forums
Robyn Lundstrom's 1986 Yamaha FZ600
RX7 Electric Vehicle Conversion
Richard Hatfield of Lightning Motors presentation @ EAA Silicon Valley meeting | V is for Voltage Community

This old video of Thundersky Lithium-Cobalt failures may be responsible for some of the concern over their products:

YouTube Video

TEG · 08-18-2008, 05:01 PM

An alternative to Thundersky:
- HIGHPOWER Profession Battery Manufarcturer

stopcrazypp · 08-18-2008, 05:58 PM

I've also heard about Thundersky a while back, but most seems to agree the quality is questionable being they are from a Chinese manufacturer. Perhaps these LiFePo cells are safer and they have improved in quality since then.

JRP3 · 08-18-2008, 07:08 PM

For all the bad press on the old Lithium Cobalt TS cells I've heard nothing but good things about the Lithium Polymer TS cells. Some US companies are importing them and giving a real warranty, for a price.
Not to mention a US company producing TS cells right here, for a premium of course International Battery

Joseph · 08-18-2008, 09:07 PM

TS is infamous on the EVDL. What I remember reading from one account is that about half of the batteries were bad, and the company did not reimburse them in anyway.

If you're looking for a BMS, I'd go to metricmind.com On the EVDL the owner of that website (Victor) is always very helpful and it seems like everybody likes his service. The products he sells are near OEM quality....so they're very expensive also. I think ProEV, located in Florida, uses their BMS for their Kokam lithum batteries.

WarpedOne · 08-19-2008, 01:12 AM

Quote:

The downside is they don't have as good an energy density so you end up needing more volume of batteries for the same kWh.

Well, I do not know the weght of needed support systems for TS batteries but 53kWh of their batteries weighs LESS then Tesla's ESS not including the front cooler and fans.

You have to look at energy density of the whole system, not the cells alone. More than a third of ESS's weight is in support systems.
Also, the volume of such 53kW powerpack is smaller than ESS.

TEG · 08-19-2008, 01:31 AM

Yeah, I know...

JRP3 · 08-19-2008, 07:29 AM

Here is a another BMS option: BEQ1 LiFePO4 Regulator