Author Topic: GS500F Restomod Street Tracker  (Read 9509 times)

Offline SK Racing

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FEEDBACK ON THE USE OF A LiFePO4 BATTERY
« Reply #120 on: June 03, 2021, 01:42:46 PM »
As some of you may have noticed, Iíve been endorsing the use of newer battery chemistries in motorcycles. To be more specific: LiFePO4 batteries. I donít advocate using any other type, like LiPo, Li-ion, or whatever. But LiFePO4, or LiFe batteries in short, tick all the boxes for small size, long life, zero maintenance, etc. There are some caveats, however. They donít like very cold temperatures, and balancing the cells is usually a necessity, whether that be with a BMS, active balancer or a charging balancer. I also wholeheartedly agree that one shouldnít fix something if it aint broke. So, if your bikeís battery is working fine, donít change it out just for the sake of change.

In my case, with my project GS500 where I chopped off the sub-frame and built a new tubular ďcafť racerĒ type sub-frame, space was scarce and the bulky lead-acid battery had to go. Fitting a much smaller LiFePO4 battery was the answer as it fits right inside the custom seat, under the seat pan. Obviously, I first made sure that the new battery was working OK by testing it for three months before putting saw to metal. It worked flawlessly, but I did realize that with such a small capacity battery (3.8Ah vs 10Ah stock), I would have to be more careful to not abuse it. That is typical of custom projects, I guess. There are often compromises.

Iíve shown this before, but here it is againÖ The size comparison of the stock and the new LiFe battery Iím using.


FEEDBACK
OK, here is my feedback on the use of a LiFePO4 battery in a GS500. (Please keep in mind that it is a DIY battery that I built from individual, soldered together cells)

When the cells were new, the one cell charged to a higher voltage. Not by much, about 0.7V, but I was concerned. A BMS with active balancing cured that phenomenon. The LiFe battery + BMS worked well for a number of months. But an engine oil change that coincided with winter temperatures introduced a problem. It turns out the 100A BMS is too sensitive and cuts out when trying to start on cold mornings due to the engine being heavier to turn from the cold new oil (10W40). The solution was to remove the BMS and now all is well. It starts easily without a hint of strain on the battery.

Is it safe to use this battery without a BMS? I would normally advise against it, but after carefully observing the cell voltages, Iím confident that the cells are now staying balanced, even without the BMS. So why is the same battery behaving different now? My guess is after working with a BMS connected for a few months, it seems that the cells got conditioned or maybe just properly balanced. I have a neat little device that draws a bar graph of the 4 individual cell voltages in real time. So I can check the condition of the cells while starting and also when the engine is running and therefore charging the battery. All 4 cells now hold the same voltage under heavy discharging (starting) and charging conditions Ė and without a BMS of any kind! The BMS that Iíve been using is rated for 100A and 150A burst, which seems too low for a 500cc engine when itís very cold. The 3800mAh (3.8Ah) LiFePO4 battery o.t.o.h. seems completely happy to deliver the amps - or cranking amps as they call it in the battery industry. I may add an active balancer later, just for peace of mind, but the battery seems to be happy on its own now.

I know most people are usually reluctant to try new stuff, but if you have been thinking about getting a LiFePO4 battery, hopefully this information will be helpful. I canít guarantee that you wonít have problems, but if you size the battery right, I think your chances of success are very good. I know that commercial LiFe batteries made for starting vehicles have a BMS built-in. Therefore all you have to get right is the correct size for your vehicle. For normal usage in a GS500, I would suggest about 5Ah or slightly bigger as a sensible size. Unfortunately, some manufacturers only specify the cold cranking amps (CCA) and not the capacity. I can't help you there. Try to verify the cell capacity before you buy. CCA can be very misleading. Cell capacity is a more accurate indication of the ability to start an engine, if you have a benchmark to go by. Now you do.  :cheers:

Last thoughts
I mentioned earlier that there are some caveats, although this one is not specific to LiFe batteries:
If you elect to use a battery of lower capacity than stock (10Ah), then the engine and carbs had better be in good nick. It should start easily. Smaller capacity batteries don't have the grunt to keep on cranking the motor while you try to start it. Do all starting troubleshooting with a stock battery first.

Iím thinking of getting one of these: Active Equalizing Balancer for 4S LiFePO4. Available on eBay and Aliexpress.

« Last Edit: June 08, 2021, 08:53:35 AM by SK Racing »
You donít stop riding when you get old, you get old when you stop riding!
1939 Panther 600cc Single - Stolen, 1970 Suzuki 50cc - Sold
1969 Triumph Bonneville 650 T120R - Sold, 1981 Honda 750F - Sold
1989 Suzuki GS500E - Sold, 2004 Suzuki GS500F - Current ride

Offline cbrfxr67

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Re: GS500F Restomod Street Tracker
« Reply #121 on: June 08, 2021, 06:52:19 AM »
Really interesting and thanks for sharing!  I wish I knew more about electronics.  The size of the battery seems good reason for me to learn!
"Its something you take apart in 2-3 days and takes 10 years to go back together."
-buddha

Offline SK Racing

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Re: GS500F Restomod Street Tracker
« Reply #122 on: June 08, 2021, 08:58:36 AM »
You're very welcome CB. I'd be happy to answer any questions.
« Last Edit: June 08, 2021, 01:16:58 PM by SK Racing »
You donít stop riding when you get old, you get old when you stop riding!
1939 Panther 600cc Single - Stolen, 1970 Suzuki 50cc - Sold
1969 Triumph Bonneville 650 T120R - Sold, 1981 Honda 750F - Sold
1989 Suzuki GS500E - Sold, 2004 Suzuki GS500F - Current ride

Offline The Buddha

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Re: GS500F Restomod Street Tracker
« Reply #123 on: June 08, 2021, 10:00:59 AM »
That last sentence - if you're trying to start the thing with a weak battery the engine and carbs should be in good nick, That's true. I used to tune the carbs to start on a near dead battery.
Cool.
Buddha.
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Offline SK Racing

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Re: GS500F Restomod Street Tracker
« Reply #124 on: July 22, 2021, 07:28:56 AM »
The latest gadget added to my bike is an automatic headlight switch. It will help with starting on cold winter mornings, because the headlight now stays off until the engine is running.

For those who didn't follow the development of the headlight switch, it was discussed in this thread: gstwins.com/gsboard/index.php?topic=73729




You donít stop riding when you get old, you get old when you stop riding!
1939 Panther 600cc Single - Stolen, 1970 Suzuki 50cc - Sold
1969 Triumph Bonneville 650 T120R - Sold, 1981 Honda 750F - Sold
1989 Suzuki GS500E - Sold, 2004 Suzuki GS500F - Current ride

 

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