EVT4000: Testing LiFePO4 Lithium Ion is a big upgrade.

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moveon70
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EVT4000: Testing LiFePO4 Lithium Ion is a big upgrade.

I recently picked up an EVT4000 with the 4x 50ah SLA batteries.
I decided to try a little experiment.
I pulled the small 15Ah 48V LiFePO4 from my Voy electric (converted to 1kW motor) bike and put it in the EVT4000 (1.5kW motor).
I know full well the little LIFePO4 battery cannot deliver very high currents, but I thought I would try. My logic is that if it worked, even a little, then I would be encouraged to buy a 40Ah version of the same battery for ~$1.5k.
To my great suprise, it worked great for ~15 blocks until the little guy started to get lower on voltage and cut out.
I tired both Economy mode, and Power mode.
Spedo said ~32mph. With the SLA batteries it was maybe a little less.

The SLA batteries are 15kg each x4 = 60kg
The 15Ah LiFePO4 is only 10kg
If I bought the 40Ah version it would still only be 25kg which would lighten the bike up by 35kg (78 lbs)
You can really feel how much mor nimble the bike is with the wight removed.
I dont have enough current in the undersized batt to do hill climbing experiments, but with less weight, it should be much better.
Also, the LifePO4 has a higher voltage when fully charged ~55V, so more power.
For those that want to over-voltage their bike, its easy to do when changing the whole batt system.

Also, in the long run, it should be cheaper. This batt can be cycled many more times than the SLA.

I left the old Anderson Power Connectors in place, and just connected to the two that feed the motor. No wire cutting. Totally reversable.

Pictures attached for your enjoyment.
P1010592.JPG
Before starting

P1010593.JPG
4 SLA batts out, and my one little 15Ah batt with a couple of Anderson Power connectors attached.

P1010595.JPG
Batt is in! 30min of work, and look at all the trunk space I have. I could have laid it flat if I wanted.

P1010594.JPG
Close up showing what I did with the wiring.

-Mark

reikiman
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Re: EVT4000: Testing LiFePO4 Lithium Ion is a big upgrade.

This is good to know 'cause I've got my own EVT 4000 sitting idle in the driveway.

peter3L
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Re: EVT4000: Testing LiFePO4 Lithium Ion is a big upgrade.

LiFePo4-packs can be found anywhere on the internet. However, I've discovered that most suppliers suggest that a standard 48V/40Ah is suitable for motors up to 1500W. This should be enough for the old EVT's, but my 2010 model has a 2800W motor. Is it OK to order a 40Ah LiFePO4 pack for this scooter, or should I upgrade to 60Ah or so to be on the safe side ?

reikiman
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Re: EVT4000: Testing LiFePO4 Lithium Ion is a big upgrade.

Depends on the discharge rate the pack is rated for.

2800w / 48v = 58.333333A which is about 1.5C which isn't that steep of a discharge rate.

moveon70
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Re: EVT4000: Testing LiFePO4 Lithium Ion is a big upgrade.

Output current depends on the battery (draining the cells too fast shortens their life) and also the BMS (which will limit the current to protect the battery even if the battery could give higher current.

Most of these have a desired disscharge current of 1C (A 15 Ah battery delivers 15A at 1C), and a max current (before BMS shuts off) of 2C.

So a 40Ah battery should be happy at 40A, and have a max (usually only for a short time) of 80A.

This 15Ah battery some times cuts out on my 1000W motor though. My 1000W motor should only pull about 20A, but some how I am hitting 30A when I accelerate from a stop pointing up hill.

As Reikiman says, a 2.8kW motor pulls about 60A, which is the higher end of a 40Ah battery. You may sometimes pull more than that (like I do) and hit the current limit.

So, I think 40Ah would work for a 2.8kW motor, but you would be better off with a 60Ah.....but they are harder to find. Ebay only shows 40Ah, but they will make you a 60Ah on request. Just make sure the BMS is alos upgraded to 120A

wookey
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Re: EVT4000: Testing LiFePO4 Lithium Ion is a big upgrade.

I upgraded my 48V 1500W bike earlier this year: http://wookware.org/pics/moped/lithbatts/

The headway cells used there are fine for the 50A max current. That 30Ah pack could do 150A continuous so would also be fine for a 2.8kW motor. The cheapest packs like Ping are indeed underpowered for this application. The medium ones like Thundersky, Foxx and CELB should be OK too - certainly for 1.5kW. Check the numbers (generally 3C so 90A max which should be OK for 2kW too).

I too found that the combination of lower voltage sag and much lower weight meant that the lithium upgrade was a big imporvement.

Wookey
Sakura s50 (Efun A)

Reid250
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Re: EVT4000: Testing LiFePO4 Lithium Ion is a big upgrade.

I have 20 X 40Ah LiFePO4's with a 3500W motor. TS says they are 2C. I get @40 mile range in hilly country at 35mph. Top speed is 50mph+.

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