woodway

It's the opposite - slow charging is better for a battery. Fast charging generates heat inside the battery and the heat accelerates the battery aging process.

Kontact

Okay. Call Shimano if you don't believe me. I don't design electronics. But my impression is that the low current doesn't allow the charger to send "good" current to the battery.

woodway

As it turns out. I do design electronics for a living, specifically I’m running a team that designs battery chargers 😀

I won’t call Shimano, but I did take a look at the manual for the di2 internal battery charger (the one with the usb connector), and it says:

”• The charging time of an AC adapter with a USB port is about 1.5 hours, and that of computer USB port type about 3 hours. (Note that the actual time will vary depending on the amount of charge remaining in the battery. Depending on the specifications of the AC adapter, recharging via the AC adapter may require as much time (about 3 hours) as recharging via PC.)”

The Shimano charger looks to have a boost converter in it (the battery is 7.5v and USB is 5v). It may be that in the past they had trouble with their converter if the port could not supply enough current. But it appears that if they did, they have fixed the problem. Cheers!

TerryDi2C

Woo! Here's something for you then ;-)
https://photos.app.goo.gl/7cJu9hsLHbNq14pA9

Note: none of the wiring/soldering was done by me

Lombard

^^^This.^^^ It is well known that trickle charging is best for the health and longevity of batteries.

eduskator

It doesn't require much. The only mechanical maintenance I do is to lubricate the derailleur's tension spring every once in a while. Dirt and grime can get inside and it may eventually seize, but it would be in extreme cases.

Battery lasts forever (2000-2500kms on my end and I do shift a lot due to riding in mountains) - I charge it 1x per month as a rule of thumb, regardless of the SoC.

Software updates are non frequent, but it's a good thing to check once or twice per year.

Kontact

That's the same note they had going back to at least 6800 Ultegra. Shimano warrantied batteries for my customers in 2021/22, so I wouldn't be so confident that anything changed.


"Use an AC adapter with a USB port with a voltage of 5.0 V DC and with a current equal to or higher than 1.0 A DC. If the one with a current lower than 1.0 A is used, the AC adapter may heat up, potentially causing a fire, smoke, overheating, destruction, electric shock, or burns."

"Do not connect the charger to PC when it is on standby. This may cause a PC failure depending on its specifications."

woodway

Well there you have it. What a crappy design by Shimano. They should be ashamed to release something like that into the wild. People see a USB port, they are going to plug into the USB port. That they allow their charger to go unstable and overheat like that is shocking, IMHO.

Lombard

What I can't figure out is why a LOWER current would cause a fire.

eduskator

1) Most of the AC/DC adapters (or ''cubes'') are providing at least 5V/1A so it's not a problem

2) Why would someone charge a DI2 system on a laptop?

3) Why would someone try to charge DI2 on a laptop that's on stand-by?

Shimano could also safe proof their chargers by preventing the recharge as long as the minimum requirements are not met. USB 2.0 ports are providing 0.5A I believe, and USB 3.0 are providing 0.9A. Not sure how complicated this is, but it should be feasible. I'm on the ''crappy design'' side.

woodway

If you need to charge your bike, cannot find a brick but your laptop is sitting there, what are you going to do? It's got this USB port that connects beautifully to your charger. You start charging and then go to bed and shut the laptop cover without thinking about it.

If Shimano is going to release a USB-capable charging product, it needs to work safely with ALL USB ports, laptop or other. FULL STOP. It's also not that hard to do just a little more expensive.

As far as how the lower current can cause a fire, I'm speculating, but it likely goes back to a crappy charger design. The dc-dc convertor in their charger is probably becoming unstable at low current levels and dissipates all the incoming power as heat rather than passing it into the di2 battery.

CrowSeph

Interesting point!. I have a spare power adapter (model: HW-050450E00) from an old huawei phone with those stats:
Input voltage (INPUT): 100V-240V 50 / 60HZ
Output voltage (OUTPUT): 5V (Volt) 2A (Ampere) or 4.5V (Volt) 5A (Ampere) or 5V (Volt) 4.5A (Ampere)

can be okay with charging my di2?

veganbikes

Probably just fine.

DangerousDanR

Let me put a WAG in on this.


"Use an AC adapter with a USB port with a voltage of 5.0 V DC and with a current equal to or higher than 1.0 A DC. If the one with a current lower than 1.0 A is used, the AC adapter may heat up, potentially causing a fire, smoke, overheating, destruction, electric shock, or burns."

"Do not connect the charger to PC when it is on standby. This may cause a PC failure depending on its specifications."
=============================================

Note the words I have highlighted. The issue is damage to external devices, not the DI2 battery.

My guess is similar to Woodway's. They will need a boost supply to get the voltage up to a level that will charge the batteries. If that external supply is poorly designed, it may pull more current from the charger (or laptop) than the EXTERNAL CHARGE SOURCE can safely supply. If you use a USB connector that has a specification of supplying 0.5A, then your design has to play nicely with a device that supplies 0.5A

Kontact

And yet, the Di2 batteries were damaged, Shimano did warranty them and the Shimano US tech reps gave the specific advice I've relayed to all of you:
DON'T CHARGE YOUR DI2 WITH A COMPUTER. USE A HIGH QUALITY BRICK LIKE ONE FROM AN IPHONE.

If you want to disregard that Shimano advice, have at it. But don't obscure it by saying that advice doesn't exist.

DangerousDanR

Please look at what Woodway and I have written. What the written Shimano manual posted here, which I quoted, states is that the DI2 can cause damage to an external charger. Can we agree on that?

Now if an external power supply is damaged, who knows what voltage and current is going to come out of it. So yes, a damaged external power supply can cause damage to any electrical device that it is connected to, including a DI2 battery. Absolutely nowhere did I suggest ignoring Shimano's advice if you have their DI2 system. What I was pointing out is that the initial failure they are warning about is to the external power supply.

By the way, in addition to my work on battery powered electronic devices, I have spent a fair amount of time getting a pile of certifications as a fire cause and point of origin investigator from the NFPA.

Koyote

Jeezus.

Please define "good current." And while you're at it, define "bad current."

Kontact

Super. The guy whose battery went bad from using his computer didn't have any computer problems. Just the Di2 battery.

Other examples were outlets with spotty output and USBs built into power strips.

I don't think anyone here has the information to state why there is a problem.

Kontact

I attempted to summarize what the Shimano techs told me, so perhaps you would like to call Shimano and grant them the honorary masters degrees you like handing out. I'll make do with the B school honors, as my electrical expertise ends with low voltage electrician matters. "Low voltage" can be a problem at outlets, but I know nothing about how rectifiers work.

Lombard

Why not just plug it into a wall outlet?

Lombard

Are you talking about voltage or current. Two different things. Charging voltage needs to match. Current generally needs to be under a certain amount.

Kontact

Good idea. Which part plugs into the wall?

Lombard

Hmmm. Couldn't you use any 120V to USB adaptor? If not, then major design flaw and one more reason I'm glad I never went to e-shifting.

Kontact

Did you happen to notice that this was a discussion about what type of 120V to USB adapter to use?

Iride01 

You can use a power supply that puts out a gagillion amps as long as the output is 5volts. The charger will only use as many of those amps as it needs. However if you use too low an amperage like the 0.5amps that your USB 1 or 2 port puts out, then the length of the wire plus the amperage required to operate the sm-bcr2 may not be sufficient to charge the battery. A USB 3 port is 0.9 amps

Shimano in some of their manuals says to plug your sm-bcr2 into a powersupply or port that can put out 1.0 amps or better. No restriction on the upper limit of amperage.

https://si.shimano.com/en/pdfs/dm/R8...050-05-ENG.pdf

In other manuals they are sort of wishy-washy about it and just say that a flashing "charge indicator" light just means it's connected to something that isn't putting out 1.0amps. Maybe their support people got tired of trying to explain what was and what wasn't a USB 3 port and why 0.9 amps and 0.5 amps made a difference.

However for either they say to don't use a USB hub. As with some USB hubs, they aren't powered and the amperage coming out of the port on the PC they are connected to gets shared between any other device on the hub. So another opportunity for some to have issues and of course there will be exceptions and some will be able to charge their Di2 battery.

So for those that want to charge with their computer, some will and some won't be able to. If you want to be certain, then plug your sm-bcr2 into most any other phone charger that you probably have laying around. The super or turbo phone chargers are ideal, IMO.