So enter my new front hub, a 500w golden motor kit from ebay.
The new hub did around 32-34km/hr which I was much happier with, but of course I wanted more
Mind you, after a ride through the national park down the road, even that speed was too fast over This terrain
Once I was happy with this hub I bought a new bike as the old one was now full of holes and with the remnants of old brackets and welds all over it from my early experiments.
I picked up a 37v 10ah LiMn pack quite cheap and was very happy with the weight of it after lugging around a metric kilotonne of SLAs, however my joy was short lived after I found it had a dud cell. I wired up a wattsup meter and found I was only getting around 3ah out of it. Pooey! Fortunately the guy I got it from was quite reasonable and gave me a full refund.
In the mean time I went back to SLAs, in a rack on the back this time. While it was better on my back it completely changed the feel of the bike and made the handling clumsy and very top heavy.
After hunting around for a cheap LiFePO4 pack I decided on giving lipos a go.
I found some cheap 22.2v 6S 4ah packs on ebay and decided to give them a go.
For the price of just over $50 AUD delivered, even with our crappy exchange rate they are great.
Running the packs in series they're just over 50v off the charge so too much for my stock 36v GM controller. No dramas, I quickly did the resistor mod on the controller and it now takes up to 58v before it cuts out. Although the batteries are rated at 15C they sagged pretty savagly with when trying to pull 20-30 amps out of them. The sag was minimal around 10a though and being otherwise happy with the 4ah packs I ordered another 2 for a 12S2P configuration (44.4v 8ah)
So next up, where to put them that's fairly inconspicious...
For fun I tried making a larger seat that I could build them in to, but after testing it I found it too wide and the front to comfortably pedal with.
I then thought I'd just get one of those seatpost racks and put them on that in a small neat box. After a trip to the local bike shop I find that they're sold out, so decided to make my own. Looking at how the racks are made I saw that they were a heavy piece of tube with the rack sitting on top. I wanted to make mine as stealthy and possible, so I decided to put the tube down the centre with the batteries either side to keep it all low profile.
Again with the left over parts from the old bike from the junk pile I used the seat post and mount to attach to my existing seat.
Then using some metal from an old computer case I bent up a housing to surround the batteries.
I rode it like this for a few weeks while I wait for the rest of my batteries to arrive and then decided I wanted something a bit neater and sturdier, so I made up a battery box in 2 halves from some 40mm aluminium channel. (the batteries are actually in the top part so they can be removed from the bike without removing the rack and seat)
The lipos get really hot when pulling alot of current from them, so I left the top of the rack open for cooling with some sturdy mesh (again from a junk pile
Batteries in place
And finished in black hammer coat with the mesh insert in red to match the bike.
And how it looks at the moment
I took it for a ride this afternoon and the 8ah pack performs very well and I'm quite impressed with it for it's size and weight (~ 2kg). I tested it with my GPS and it does 40km/hr which I'm happy with. On the road I feel like I could do with a bit more but when you're belting along a narrow dirt trail you really feel like you're moving!
More to come!
I'd really like to cut the top bar out of the frame and weld in a slightly thicker one with the batteries inside that, but it's probably not worth the effort for the sake of the small rack on the back. Maybe on v4.0