Smaller Battery - using starter

750steve wrote: Yeah, all of the above is probably true, BH you're an intelligent guy with a hell of a background in this field, infinately more than me! I'm not knocking anything you guys say BUT just sometimes the conventional battery just doesn;t suit the application. If my battery goes prematurely i'll replace it, hopefully it won't but the well laid out explaination you posted seems to indicate a probable shorter lifespan than a lead/acid. That bike i built would just have looked daft (maybe you guys think it does anyway :lol:) with the std size battery hanging out of its arse

Actually, the Li battery may have a longer lifespan than lead acid because it seems they are running it "short" which means probably not fully recharging it because the charge voltage is a shade below nominal. That actually increases battery life because Li batteries are a "fixed energy" device over life span. I remember Sanyo lowered the recommended charge voltage a bit on their cells at one point because they wanted to get more recharge cycles for the batteries they were putting in laptop computers. Running them a little short is no big deal as long as they have enough charge to do the job and the Li seem to have plenty.

As for lifespan of lead acid: in the Kawi 1979 B4 model 750s, they sucked. I got 18 months out of the first battery, about the same on the next two batteries. It's because my model (by federal law) has all the lights on with the key which really overloads the battery when you crank the starter. I changed the wiring so mine disconnects all the lights when I hit the starter button and average battery life went from about 18 months to about 6 years.

The Shorai batteries may have an OK performance. One thing that concerned me was they seem to have a problem cranking the starter when they are cold. The Shorai website says that if it doesn't crank, the battery will warm up a little each time it tries (and fails) to crank the starter so eventually it will warm the battery enough and it will work. That didn't make me feel real confident..... :ohmy:

From the Shorai web page:

Q. I hear that lithium crank poorly when it gets cold, is that right?

A.Lithium do increase in resistance more as temperature drops, compared to lead-acid. However, they also react to cranking under cold conditions in a much better way. //If your LFX fails to start the engine on first crank, that first crank has warmed the battery, and the second attempt will be much stronger, and so on until you get a good start.

bountyhunter wrote: As for lifespan of lead acid: in the Kawi 1979 B4 model 750s, they sucked. I got 18 months out of the first battery, about the same on the next two batteries. It's because my model (by federal law) has all the lights on with the key which really overloads the battery when you crank the starter. I changed the wiring so mine disconnects all the lights when I hit the starter button and average battery life went from about 18 months to about 6 years.

Jeez thats a hell of a difference, in the UK we were lucky enough to have the option of no lights on startup, thats the way i done my rewire as well, on starting all my bike powers is all thats necessary......ignition, coil....thats about it

bountyhunter wrote: The Shorai batteries may have an OK performance. One thing that concerned me was they seem to have a problem cranking the starter when they are cold. The Shorai website says that if it doesn't crank, the battery will warm up a little each time it tries (and fails) to crank the starter so eventually it will warm the battery enough and it will work. That didn't make me feel real confident..... :ohmy:

From the Shorai web page:

Q. I hear that lithium crank poorly when it gets cold, is that right?

A.Lithium do increase in resistance more as temperature drops, compared to lead-acid. However, they also react to cranking under cold conditions in a much better way. //If your LFX fails to start the engine on first crank, that first crank has warmed the battery, and the second attempt will be much stronger, and so on until you get a good start.

True, i did read that as well though i havent had a problem starting so far with their correctly rated replacement. It did, im sure, say somewhere to run the headlight for a short time which increased the cranking power......i couldn't get my head around that so i have never tried, if it's difficult to start some day i'll give it a go. The only thing im really concerned about with is the voltage in it dropping below 9v if stood for a long time......time will tell & i don't mind being a guinea pig.

750steve wrote: The only thing im really concerned about with is the voltage in it dropping below 9v if stood for a long time......time will tell & i don't mind being a guinea pig.

One of the major advantages of an LiFe battery is that it's self discharge rate should be very low over time. Lead acid self discharge quite a bit which is why they have to have a battery tender for storage. Li batteries should have very low loss, I would guess less than 5%/month for a healthy battery. I think the battery would have to sit for a very long time to drop to 9V.

You could hook it to a tender to keep it peaked up. I think Shorai sells them.