Friday, 14 March 2014

More mods on bike.1

First, the pannier. While I was in London a few weeks ago, one of the plastic hooks broke off my nice big pannier, the one that's big enough to take my big ammo can that can hold 12 of my 4s1p batteries. So I bought a replacement, they're quite cheap. On the replacement, one of the hooks has started to bend, and I'm not confident that it will stand up to the  combination of the heavy weight (several kg of battery) and very rough ground that I often bike over.

So I went back to the one with the broken hook, drilled out both hooks, and replaced them with a steel hook, made from an old broken 1U power supply. That looks a lot more sturdy.

I've been thinking about how I'm using these batteries, and I'm going to change. Using the 5AH batteries paired as 8s1p one at a time has worked, but it means that some batteries get fully discharged, and some don't get used at all. From what I've read about Lipos, it would be better for the longevity of the batteries to connect them in parallel, and not fully use all of them.

So I'm planning a new wiring harness. Pairs of batteries will be connected in series, so they'll be 8s instead of 4s, and I'll put four of those pairs in parallel, and end that with an EC5 female connector, because those are easier to solder than other types. That will connect to another wire, made up of an EC5 male, a 40 amp fuse, a contact breaker and a wattmeter, with an EC5 female at the other end. On the bike, will be an EC5 male. So normally, I'll ride with the batteries configured as 8s4p (eight cells in series, four in parallel) and if I want to know how much I've used, the wattmeter will tell me; 20 AH being the nominal capacity, 16-18 AH being a realistic number.

The tricky bit will be to wire up the balance ports. I have to connect two 4s cables to an 8s, and I have to get it exactly right, or I'll cause a short circuit, the wires will melt and I'll have a garage full of smoke. I think I know how to do it, though, and I know how to test that I got it right, and when I eventually connect it to the battery, I'll do it outside, just in case!

So then I'll use the 8-port balance cable for the cell monitors, so while I'm riding, each of those 32 cells will be monitored.

For charging, I'll use the exact same power cable that I use for riding, and charge them as 8s cells (I was wise enough to buy an 8s charger). I'll use a 1-to-4 parallel balance cable for balance charging (which I'll make by simply plugging three 1-to-2 cables together.

This should greatly simplify my battery management.

And I have these nice sturdy but light boxes that will take exacly eight batteries in each one. So I'll have an 8s4p in one, and and 8s3p (which I might upgrade to 8s4p by buying two more batteries, they're only £16 each) in the other.

And then, the PDA. While I was circling Letchworth, I ran out of battery on the PDA, which is no surprise, because I'd been out for 10 hours. So I've added another cable to the bike, running from the panniers (where I'll have a 20AH, 5v battery intended for powering iPhones and suchlike, which I suspect is actually only 10AH, but that's enough) up to the handlebars, so I can plug the PDA into that external battery. I had thought of taking a feed from the main bike batteries and putting that through a fuse, a switch and a step-down circuit, but I decided that simpler was better. And I can use the same lead to power anything else I decide to put on the handlebars.

Finally, I took off the wireless speedometer. Wireless sounds great, but they simply don't work very well, so I've replaced it with a wireful one.


  1. I think you might have invented a word.. I was unable to find a reference to 'wireful', as an antonym to wireless, anywhere else on the webworld.

  2. Yes, I know. It's a word I needed, so I made it.