Lithium Motorcycle Batteries - how do they manage to charge from vehicle power?

Thread Starter

Rich:-)

Joined Oct 14, 2016
46
This is the sort of battery, the type you can use in place of the traditional lead-acid one.
https://www.sportsbikeshop.co.uk/motorcycle_parts/content_prod/248790

It claims to have "Active balancing embedded control electronics with microprocessor control".

If you've ever taken a look at the charging supply to a battery on a motorcycle, at least one with a permanent magnet 3 phase generator, you'd see that the power feed to the battery is a string of sharp pulses that once the revs climb the regulator chops into even sharper pulses.

How does the controller manage this to charge the lithium cells?
Do the cells just get exposed to this and have to suffer low level pulse charging and thus never get fully charged?
 
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Reloadron

Joined Jan 15, 2015
6,508
If you've ever taken a look at the charging supply to a battery on a motorcycle, at least one with a permanent magnet 3 phase generator, you'd see that the power feed to the battery is a string of sharp pulses that once the revs climb the regulator chops into even sharper pulses.

How does the controller manage this to charge the lithium cells?
That's pretty much how the regulators on larger bikes work. The pulses are PWM (Pulse Width Modulated) This is why pulses go from a larger to smaller pulse width. PWM off a 3 phase stator works just fine. Enter the problem which I have no answer for. Charging a LiPo battery requires monitoring the individual cells temperatures and other parameters. My ride is a classic 92 Electra Glide with an updated charging system. When the LiPo batteries first came out my dealership passed one around for the Ah factor of how light it was but the early LiPo batteries required changing the charging system on the bikes, at least my ride for sure.

All I can figure here is manufacturers used up the free space in the container with a circuit to take the charging signal we have to the charging signal we want for a LiPo battery. I never made the transition as I saw no need. Running DayMaker LED headlight and spots the existing system has more power than it needs and works fine. Winter up here so my ride sits in the garage with a battery tender on it. About once every few weeks I go out, start and run it for about 15 min and that's it. Sorry but no clue how these newer motorcycle batteries work internally but there has to be something in there.

I also just read all of the data on the image of the battery. First line reads "Use only compatible chargers". Unless the listed motorcycles have compatible chargers I haven't a clue where they are going with this?

Ride Safe
Ron
 
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Thread Starter

Rich:-)

Joined Oct 14, 2016
46
Hi Ron.

That's pretty much how the regulators on larger bikes work. The pulses are PWM (Pulse Width Modulated) This is why pulses go from a larger to smaller pulse width. PWM off a 3 phase stator works just fine.
That a new one on me.
I was aware that bikes (which require DC for battery charging) have either single or three phase stators, or even alternators. The stator based ones generally have thyristors based shunt regulators but the higher end more modern ones have FET based R/R's and some even have series regulators.
But I have never heard of any actually using PWM - do you have any details of this (or bikes it's used on) so I can read up about it please?

Enter the problem which I have no answer for. Charging a LiPo battery requires monitoring the individual cells temperatures and other parameters.

All I can figure here is manufacturers used up the free space in the container with a circuit to take the charging signal we have to the charging signal we want for a LiPo battery.
This is what I have been trying to work out.

If I were doing it I'd put a capacitor in the package and have the controller switch over to that when the bike was running, then have the charging circuit run from that to charge the cells. Once the voltage at the capacitor drops (signalling the engine has stopped) the cells would then be linked back to the output ready to power the bike.

But if that was the case it would be difficult to charge the cell with a mains charger that is also trying to control the charge process.
I remember the very early Lithium packs couldn't be charged from your bike but I'm not sure what was needed to stop that from happening.

The more I think about this now, I'm guessing that they just allow the cells to be exposed to the bikes power. I guess the voltage from a bikes R/R doesn't get high enough to over charge / overheat the cells but it'll never fully charge them either.. but they don't care about that as we aren't interested in using the full capacity of a starter battery, just as long as it can give short burst cranking current we're happy.
 

Reloadron

Joined Jan 15, 2015
6,508
Prior to the LiPo batteries motorcycles used several different charging schemes. The 92 I mentioned came with a reverse package which was fine and well. Then when my charging system failed I made a fun discovery. The entire system was replaced with a
Thunder Heart Performance 3-Phase Charging System Couldn't buy just the regulator and my stator was fine. OK, $400 later I have my regulator and parts I didn't need. :)

During that time I looked at various charging systems and regulators. They start with single phase, my bike originally used a simple split phase and there were also 3 phase delta configured. A Google of motorcycle charging system schematics will yield many of the designs in use. This is where I discovered systems using PWM. The pulses you mentioned earlier. A Google of "Motorcycle Charging Circuits" will bring up a dozen hits on different designs. While I have no desire or need to change to a LiPo battery I have given thought to building a shunt circuit design using mosfets. Then too I still have a complete spare system of what I mentioned earlier.

I do know with the regulator disconnected when I measure the AC voltage phase to phase at about a 600 RPM idle I get about 22 VAC phase to phase. That told me my stator was just fine.

Back to the LiPo battery? I haven't a clue what they have in there. They do call out specific bikes it should work with. Eventually I see all new production bikes going with LiPo batteries and compatible charging systems.

Ron
 
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