Thought I should create a stand-alone thread for this.
My original Yuasa battery is 3 years old and still going strong. Despite this, I decided to make up a battery using A123 lithium iron phosphate cells. These are small cells with extremely high power density. Each cell is 3.3V, and is able to deliver 120A.
A string of four cells in series is thus 13.2V, just the right voltage to start my bike with. If I add a second string of four cells, the maximum current goes to 240A.
I bought my cells on ebay. They cost $10 each, for a total of $80. They came without tabs and are of unknown quality. I was originally going to construct a spot welder to assemble the pack, but then came across a cool battery holder by someone here in Sydney. Details are here: http://www.1000rr.net/forums/showthread.php?t=54463 (http://www.1000rr.net/forums/showthread.php?t=54463).
Here's what the cells look like in their nice new home:
(http://farm6.static.flickr.com/5245/5241983182_a9912377d9.jpg) (http://www.flickr.com/photos/suzy_j/5241983182/)
Weight for the assembled pack as shown is 754g. This contrasts with ~3500g for the standard Yuasa YT12B-BS lead acid battery that comes with my bike.
The cell holder is a wonderful design. Screws on either side of each cell clamp contacts to the cells. The little holes shown allow me to poke my multimeter probes in and measure the voltage on each cell, which is really handy.
Next step is to charge them. I'll do that using a lab power supply at work. Then I'll put a load bank on them to test them. Then, assuming all that works out, I'll try them in the bike.
wow, so glad you are using your powers for good instead of evil!! ;D
how did you come to think of this? Weight saving? Battery longevity? Be interesting to see what the load testing brings, the CCA is the big test of a battery.
Great work and keep us updated! [thumbsup]
Will they tolerate the somewhat neanderthal charging system on our Ducs?
I think the charging system will shorten the cell life. I plan on building a replacement rectifier/regulator (see http://www.ducatimonsterforum.org/index.php?topic=38021.0 (http://www.ducatimonsterforum.org/index.php?topic=38021.0)), but in the meantime, I fully intend on having some fun with these cells. When I stuff them, I can replace them very easily, thanks to the cool cell holder.
Been thinking about them too, suzyj, and waiting for a reliable VR/R. Would probably use only four instead of eight and mount them in the tail of the bike, under the beertray, in case they flame up.
Alas my load is only good for 300W, which limits me to 20A.
At 0A load the terminal voltage is 13.26V. At 20A, 12.35V. That's a 910mV drop, or 46mohm resistance. The spec for the cells is 10mohm/cell. A perfect 2p4s pack should be 20mohm, so I presume the rest is coming from my holder (or else the cells are a little sub-par).
Dunno how to specify CCA, but a terminal voltage of 6V will imply 160A. I imagine it should be plenty to start the bike.
I'll give it a go.
very interesting suzyj - out of curiosity what it is the total load on the bike? I am assuming everything is standard so load should be ok from what you have tested.
Wow Suzyj. Youv'e blown me away in the past but this is way out there ! :o
I'll have to redo some of the wiring before it can go on the bike, as the terminal locations are significantly different to the present battery. In the meantime I weighed the standard lead acid battery (3964g), so the weight saving will be more than 3kg.
The load after the bike is started doesn't really matter, as this is supplied by the regulator, not the battery.
can i ask how much you picked up the pack/holder off Ripper for?
looks pretty decent all up i reckon! easy 3kg save :D
btw, i'd be extremely interested in a rec/reg if you do end up making a few.... wasn't that supposed to happen when you got a new battery (aka now)? :P
Hi Suzy
How's that battery going?
It isn't at the moment - I got up to the point of making new wiring up from 4ga cable. I replaced the wire from the solenoid to the starter and all my starting issues vanished, so there was clearly a poor connection there.
So at the moment it's on the back burner (again). When my present battery goes, all I need to do is make some wiring up for the low current connections to the battery (I have wires made up for the high current bits) and fabricate something to hold the new battery in the battery box, and I'm good to go.
In the meantime, I'm making bicycles :)
I was looking thru the UK "Performance Bike"mag today and came across this exact same set up. Apparently put together by one of their staffers and being sold commercially for 180 pounds! They must be making a bit of a markup.
Any intention of making to order Suzy?
http://www.ebay.com.au/itm/RCE-12V-Lithium-Ion-A123-LiFePO4-Starterbattery-4-6Ah-/220784869688?pt=AU_Electronics_Batteries_Chargers&hash=item3367cdc138#ht_10594wt_1139 (http://www.ebay.com.au/itm/RCE-12V-Lithium-Ion-A123-LiFePO4-Starterbattery-4-6Ah-/220784869688?pt=AU_Electronics_Batteries_Chargers&hash=item3367cdc138#ht_10594wt_1139)
My old battery finally gave up the ghost enough to annoy me, so I replaced it just now.
As well as changing the battery, I made up new cables from it to the solenoid, from the solenoid to the starter motor, and from the battery to the engine, from 4 ga ultra flexible wire. This stuff is about the diameter of your finger, so should be good for plenty of current.
I removed the Yuasa lead acid battery (heavy!) and the rubber tray it sits on, and made a new base from thick rubber sheet. Then I reduced the length of the battery strap.
Here's the result.
(http://farm3.static.flickr.com/2004/5798531815_a94deb8a89.jpg)
(http://farm3.static.flickr.com/2687/5798531821_4bf0888848.jpg)
(http://farm6.static.flickr.com/5228/5798531829_fda1bba360.jpg)
The cells are cheapy ebay ones, but they appear to be plenty to start the bike. Time will tell.
:'(
Well time has told me the dodgy ebay cells aren't really up to the job. When the bike is warm they start it fine, but on cold mornings, nope. I'm starting to get sick of roll starting my bike.
So that's $80 down the toilet. I just pulled the pin on a set of 8 cells from http://www.hobbyking.com/hobbycity/store/uh_viewItem.asp?idProduct=6444 (http://www.hobbyking.com/hobbycity/store/uh_viewItem.asp?idProduct=6444). These guys have a weird website - it initially says they're $18 per cell, but if you leave the page up for a few minutes, the price comes down to $12 per cell. These are reputedly genuine A grade cells, so fingers crossed they'll have the teensy bit more go that the bike needs when it's cold.
Hi Suzy,
Would like to know if you notice any difference riding the bike with a lighter battery?
Paul
Quote from: Paul on June 24, 2011, 12:35:00 AM
Hi Suzy,
Would like to know if you notice any difference riding the bike with a lighter battery?
Hard to tell. It feels like the difference between a full or empty fuel tank. It's probably more placebo than anything though.
I'm not super electrically minded, but if you made it a 10 cell job instead of 8, would that mean more CCA for those cold mornings? Or the eBay cells ain't putting out what they're sposed to anymore?
Quote from: Nibor on June 24, 2011, 05:15:16 PM
I'm not super electrically minded, but if you made it a 10 cell job instead of 8, would that mean more CCA for those cold mornings? Or the eBay cells ain't putting out what they're sposed to anymore?
It would have to be 12. Each cell is 3V, so four in series gives 12. I'm using 2 strings of 4 for extra current. You can also do 3 strings of 4.
If I used 12 cells, even the dodgy ebay cells would work fine. As it is with 8, they're on the annoying side of marginal. A cell holder to hold 12 cells plus four more cells would cost more than just replacing the 8 dodgy cells with good ones.