Upgrading Battery in PX50

Riot Fest was great fun, as it always is. This year I though I’d push the PX50 to it’s absolute limit and give 4 people a ride to and from Riot Fest each day (+me = total payload of five people).

I’m not going to lie, it was a bit scary at a couple of points, but all-in-all the car drivers were pretty cool AND I unlocked a personal achievement: I got a taxi cab parked in the bike lane to move! (I pulled up behind him and kept laying on my phone until they took off).

But there will be another post on the fun rides too and from Riot Fest. (I’m mainly waiting for the people I took to post/tag me in their photos.) So day two, we’re getting ready to take off in the morning and the PX50 is dead. Deader than cyclist on Lakeshore Drive. I kind of poke around, to short circuit (pun intended) a long meandering story, I’ll break down the bullet points:
 

Bikes / Trikes from China may come with cheap lead acid batteries.

Note the italics on "may", because life is like ordering something from China, you never know what you're going to get.

I knew this, and already had a LiFePO4 on standby, I was hoping to swap it out in November.

If you’re not familiar with the different sorts of EBike batteries, I probably should write a whole post on it, but in short you have lead acid, which are the worst, and lithium ions, which are better and have battery management board built in that explicitly prevent the next things I’m about to describe from happening. So if you’re thinking about building- the punchline of this article is-

DON’T BE CHEAP - DON’T USE LEAD ACID BATTERIES

I Started Charging While the Battery was hot ... Don't do that.

So this poor battery/controller/motor had just put on a Herculean effort, hauling a full payload of four humans to and from Riot Fest... with an unexpected detour. I come in on (the electric version of) fumes, and of course we want to all to get to the bar, so I throw it on the charger and off we head.

This is a problem because multiple sites I came across while trying to figure out how exactly I destroyed this thing all say very explicitly for LithiumIon AND lead acid batteries:

DON'T TRY TO CHARGE A HOT BATTERY ... LET IT COOL OFF FOR A BIT

Which brings me to my last lesson of this demo job:

I Also (probably) Over Charged the Night Before ... Don't do that either.

So I had been all excited for Riot Fest and taking the PX50 out on Thuresday night. The charge was showing it was a bit over 70% and I though, well I want a FULL charge for the maiden voyage, so I'll just leave it on over night. 

When I came back the next morning it did smell a bit like spent fireworks. The smell when a cloud of firework smoke blows over you, or when you are in a Civil War Reinactment. That's how my garage smelled. I thought, "hmm... not good" and figured my replacement battery might be coming out sooner than I expected. 

I'm not going to bold this one, since over charging is a lead-acid problem. Most LiIon batteries have board to prevent over and under charging. I will show you some pictures though. 

But I'm getting ahead of myself. Let's take a quick stop to talk about accessing the battery.

Pulling the 'Bed' Off of the Px50.

After dealing with cars so long, this bit really is a dream. The bed is held on with three bolts. One above each wheel- and one toward the front, facing downward.

I would have taken more pictures and made this the first in a series of 'Technical Posts' ie instead of a Hayne's manual you will just have this blog for tear down and repair information, but it is apparent that the PX50, while the most likely contender for production will still have some serious modifications before we go to market. So instead I'll just show this picture of the bed kind of tilted off.

The controller is in the white box off to the right. The battery was in a black box off to the left. My new LiFePO4 battery looked like heck as the one I got off of Amazon had a loose wire which I had to tear into it to find/reconnect. I re-skinned it after with Duck tape (Sidebar: there was an episode of Home Improvement where Tim corrected Jill for calling it Duck tape that it was in fact duct tape, or to push the issue, it was not for ducks, but for HVAC ducts. This is innacurate. 3M tape was invented for patching ammo boxes and speedholes and earned the nick name duck tape among GIs. 3M Trademarked their duct tape as Duck tape. /rant)

So the only other hack of note, is that the lead acid battery pack (4x12v in series) only had two wires, as lead-acid charges and discharges on the same circuit. For the LiFePO4 battery I hooked the two power wires up to the original wires going to the battery pack- but cut the original charging port wires that were in the white box and ran jumper 14 gauge wires to the charge wires of the new battery pack. NOTE: don't just cut things all quick, you'll arc along the cutters, cut wires one at a time and kind of have an idea of what you're doing. If you need help and can't figure it out on line elsewhere PLEASE EMAIL ME.