Ego Street Scoota LiFePO4 Lithium Upgrade
Here's my upgraded "Ego Street Scoota". It started life as a 48V SLA bike, but after several upgrades it's now fully converted into a Lithium Ion based system using LiFePO4 Headway cells.
The pack is a 24s2p, nominal 76.8V, built out of 48 Headway LiFePO4 38140S 12Ah screw-tap cells. It weighs just over 19Kg, versus the 48Kg my SLA bank, so I've shed nearly 30Kg! I elected to mount mine vertically. It wouldn't fit flat as it was too wide, so I sacrificed some seat space as before. The advantage of this arrangement, though, is I can more easily remove it if needs be. I also have enough space down the side to slide the BMS down alongside it so it is flush with the battery case, which can be used as an extra heat sink to protect it if it ever gets too hot shunting if cells are particularly out of balance. It usually runs cool as a cucumber though, even at 9A!
Here's the final arrangement. I had to take a chunk out of the seat, but I'm quite happy with the result Smile. My Lyen's controller is en route back to me, so I've only had chance to use it with my cheapo controller, but I'm delighted by the improvement to its all round performance.
Here's my painstakingly constructed Goodrum Fechter BMS doing its thing... I'm using a BMSBattery EMC-900 with it, which gives me the aforementioned 9A, though I've wired it all up with nice, thick wiring so that I can take advantage of the 20A charge rate that the GF Zephyr is capable of handling, if needs be. I used an ATX connector, as a 25-pin serial couldn't accommodate my 1mm2 tap wires.
I'm delighted with the improved charge rate, which is almost four times what I got with my 2.5A SLA charger! A bit of weatherproofing is in order, now, to protect the bank and battery compartment from the wet when poorer weather arrives.
The Range Test
I've now had a chance to give the setup a proper range test. I have my Lyen's 12-FET controller set to 45A, which is pretty hungry as far as power consumption goes. Though the Lithium pack is nominally 76.8V, in actual practise the pack spends most of its discharge between 84V and 77V, with their voltages quickly collapsing once they pass below the nominal 3.2V per cell level.
The CellLog monitor for my 24s LiFePO4 pack
Over a couple of days, I charted the distance I travelled through 9 different journeys, all of them in city conditions (with a good amount of stopping and starting at lights). The bike made it 27 miles in all before the weakest cells passed below 2.5V and I called it a day. I'm confident that if I kept to a lower speed control setting, and did a long uninterrupted out of town run between cities, I could greatly improve on this range. Bear in mind also that this was using my power-hungry LYEN edition controller on its highest setting, which cost the bike about 40% of its range when it was running on SLAs.
For my next range test, with my charger in the top-box, I'm going to see if I can traverse the 35-40 miles to a nearby city, then recharge and return.
From completely flat to a full charge, the pack took 2 hours 50 minutes to fully recharge from my EMC-900 charger, which delivers 86V at 9A. I've wired the Goodrum-Fechter "Zephyr" BMS so that it can comfortably support the full 20 amps that the board is capable of managing, and so have the option of upgrading to a more powerful charger.
The charge setup, running at 9 amps
Based on this, I could probably get the recharge time down to 1 hour 15 minutes with a suitable power supply unit.