[nulldevice]

I have a 2008 Burgman 400 k8 with no issues at the moment, but want to change out the lead acid battery and make a home made lifep04 (lithium iron phospate) in the medium term future. I have built rectifier/voltage regulators in the past with success so this ought to be easier, or at least not harder to do.

The issue is I need to know the amperage draw from the starter motor while it is cranking so I can choose appropriate amperage battery cells. A half hour of searching this site and the Internet has given me no joy at this point.

What I have found out is a replacement starter motor is rated at 1.5 kilowatts. That's about 125 amps at 12 volts. Wow! I suspect that is way more than the scooter actually uses, but how much is needed? Does anyone know? Right now the cell candidates are:

USED HEADWAY 38120 HP 3.2V 8AH LIFEPO4 BATTERY - $195/kWh

PRICE DROP AGAIN! NOW JUST $5/CELL FOR TRUE LIFEPO4 POWER CELLS! BACK WHEN THESE CELLS WERE $12 EACH USED AND THE BEST VALUE FOR CAR AUDIO, WE CONTINUED TO PUSH HARD TO SAVE YOU MONEY AND MAKE THESE CELLS THE BEST OVERALL VALUE ON THE MARKET FOR CAR AUDIO AND NOW EVEN FOR SOLAR STORAGE. THESE...

batteryhookup.com

A123 18650 APR18650M1B 1100mah Lifepo4 - $199/kWh

Price is for 1 cell. If you order 100 we will ship it in the original box. Otherwise we will ship them in custom packaging. Just $0.72/cell for excellent power cells for smaller projects. Here are brand new in the box A123 APR18650M1B Lifepo4 batteries. Our guess is A123 makes these cells for...

batteryhookup.com

The Headway cells will certainly do the job with a 200 amp discharge capacity, but if the amp draw is signficantly less than 125 amps I can make a much more compact parallel battery pack with the a123 cells with a 30 amp draw. The price for capacity per dollar is close enough I am not concerned with the price difference.

 

[Dave_J]

If I had a AN400 I'd go out with my clamp over Amm meter and get a draw reading.

One thing about the charging system of these cheap voltage regulators is they spike the voltage all over the scale in a very noisy ripple effect.

Lithium iron phosphate like a steady charge so you will need to make a GOOD BMS with some sort of front-end capacitor and/or inductor filtering.

How many pounds is this going to save?

 

[mikeyMarine]

what size fuse does your bike use for the starter? you know the starter won't use more or the fuse would blow

 

[zrx212]

what size fuse does your bike use for the starter? you know the starter won't use more or the fuse would blow

There is no fuse on the starter main power wires on the Burgman 400 or any bike AFAIK, the starter is connected directly to battery once the starter relay is closed, that's why some kind of duty cycle should be observed, like for example, 10 seconds cranking, 2 minutes off/rest.

 

[nulldevice]

If I had a AN400 I'd go out with my clamp over Amm meter and get a draw reading.

One thing about the charging system of these cheap voltage regulators is they spike the voltage all over the scale in a very noisy ripple effect.

Lithium iron phosphate like a steady charge so you will need to make a GOOD BMS with some sort of front-end capacitor and/or inductor filtering.

How many pounds is this going to save?

The attraction is not the weight saveings, 5-10 pounds maybe, but a way to get one that can sit in the basement for a few months without worrying about self discharge and perhaps get a crisper start, think nicad powered hand tools vs lithium battery powered tools. There is also the geek/nerd self training exercise and DIY satisfaction. You have just given me another aspect of this project to investigate with the filtering comment.

I am thinking over/under volt protection isn't needed. The alternator stays at or slightly below the maximum volts and the scooter won't start at well above the minimum voltage. It sits in a heated basement in the off season so low temperature protection isn't needed. That leads me to consider an active balance board instead of a BMS. High amperage BMS are expensive. For noise filtering I wonder, do I need to think in terms of micro-farads or multi-farads super-caps for a filter?

Off to try my google-fu

 

[G-Dub]

I would proceed very cautiously. Commercial Lithium batteries are more than just some.cells soldered together. They have sophisticated circuitry to control charging and safety issues. Here's one site that goes into some of that. You may already be aware, but putting this here for reference.

https://www.fastbikegear.co.nz/index.php?main_page=page&id=18&chapter=1

 

[nulldevice]

The attraction is not the weight saveings, 5-10 pounds maybe, but a way to get one that can sit in the basement for a few months without worrying about self discharge and perhaps get a crisper start, think nicad powered hand tools vs lithium battery powered tools. There is also the geek/nerd self training exercise and DIY satisfaction. You have just given me another aspect of this project to investigate with the filtering comment.

I am thinking over/under volt protection isn't needed. The alternator stays at or slightly below the maximum volts and the scooter won't start at well above the minimum voltage. It sits in a heated basement in the off season so low temperature protection isn't needed. That leads me to consider an active balance board instead of a BMS. High amperage BMS are expensive. For noise filtering I wonder, do I need to think in terms of micro-farads or multi-farads super-caps for a filter?

Off to try my google-fu

Back from my google-fu sessions. I found this.

https://electronics.stackexchange.com/questions/235195/3-phase-permanent-magnet-alternator-with-regulator-rectifier-scr-output-wavefo

From what I see the only big voltage spikes are very transient when the regulator is switching the charge rate.

Note the horizontal axis is milliseconds and the vertical axis is AC. The big spikes are 2 volts plus and minus maximum for a very few milliseconds.

Back to google-fu to see how to size an LC or RC filter. Or perhaps just an L or just a C.