Why are all Bosch chargers so bulky?

[rampampam]

Does anyone know any technical reason why all Bosch eBike chargers are so heavy?
Looking at 4 amps weighting 600g it’s kind of heavy. An example GaN USB-C charger rated at 140W weights ~230g.
Do they just don’t want us ever to recharge during the trip?

 

[rampampam]

“The small unit weighs just shy of 800g and is easily stowable.”
I would be also shy or even ashamed to advertise such weight

 

[RustyIron]

I don't think that Bosch batteries charge at 230v... just sayin'.

The original question is regarding overall weight. Bigger components handle more current, bigger spikes, and dissipate heat better. Or maybe the Bosch just has bigger heat sinks. I can't say for sure because I've never even handled one. The one thing for sure is the smaller isn't necessarily better, and smaller is usually more delicate.

 

[rampampam]

I put 140W as an example for a reason, my “smart” system charger is 4A and 36V according to the manual.
If it was 920W, would be great, full charge in less then 1h

Rustyiron - I wouldn’t call an average laptop charger delicate

 

[rampampam]

https://www.bosch-ebike.com/fileadmin/EBC/Service/Downloads/Bedienungsanleitungen/MY2022/Bosch-eBike-Manual-Charger-MY22-WEU.pdf?_=1631178404

Page 10 says it’s 36V but yes usually they don’t tell us everything to not confuse people. Anyway this brings max charger power only a little higher.
In near future we will have USB4 2.0 chargers rated at 240W and with GaN tech they still will be about half weight of Bosch.
Maybe EU will one day force ebikes to use USB-C .

 

[rampampam]

This is interesting info, I can imagine the obfuscation to keep the prices high. I just can’t understand why they don’t want to make a premium priced lightweight charger.
Maybe it’s their automotive legacy

 

[RustyIron]

Rustyiron - I wouldn’t call an average laptop charger delicate

Are you high?
You can't plug your laptop charger into your bike.
You can't plug your bike charger into your laptop.
Just stick with the components you have, and use them according to the manufacturer's instructions.

 

[rampampam]

Of course I can’t and thats the point I am bringing up here. To understand is there any technical reason and not only profit security by manufacturers.
BTW - you wanna tell me you never charged your laptop/eBike being high?

 

[Slapbassmunky]

Technical reason? A charger is a switch mode power supply, these contain switches (FETs) inductors and capacitors amongst other things, but we'll focus on these for now. The faster a FET can switch from full on to full off the less heat they generate. The lower the on resistance the less heat they generate. The more times you can turn that FET on/off in a second the smaller the inductors and capacitors need to be for a given power output. GaN FETs offer lower resistance and faster switching speeds than 'classic' FETs, so the other components can shrink and there's less latent heat to deal with.

Given the reliability and ruggedness of the Bosch chargers I didn't think they were too bad. Remember they aren't fan cooled either, so you can only shrink them down so much before heat becomes an issue.

This is in strict laymen's terms, before all the 'engineers' jump on me....

 

[MountainBoy]

Does anyone know any technical reason why all Bosch eBike chargers are so heavy?
Looking at 4 amps weighting 600g it’s kind of heavy. An example GaN USB-C charger rated at 140W weights ~230g.
Do they just don’t want us ever to recharge during the trip?

Isn't that why asking why a Tesla Supercharger plug looks like this:

While all other car makers use a committee developed standard that looks like this:

Some companies don't care if the solution is elegant. Maybe that's why there are more Tesla Superchargers in the world than all the rest combined?

 

[Rusty]

Rustyiron - I wouldn’t call an average laptop charger delicate

Lower voltages and lower power drawer with laptop chargers. Saying that, I would get 1 or 2 calls a week to see if we have a charger for some laptop or another in stock. The bigger ones always seem to outlast the small ones.
A good example is for a client I supplied 50 notebooks a couple years ago. They were for different retail markets and came with 3 different adapters. The traditional ones were a smallish one and a larger one. All of the larger ones are still going, several of the smaller ones have failed and most of the AiO type have failed.

 

[Slapbassmunky]

Isn't that why asking why a Tesla Supercharger plug looks like this:
View attachment 98024

While all other car makers use a committee developed standard that looks like this:
View attachment 98026

Some companies don't care if the solution is elegant. Maybe that's why there are more Tesla Superchargers in the world than all the rest combined?

Not really, the bigger plug allows flexibility for I/o connections where Tesla's one is proprietary. Tesla were ahead of the game and have invested heavily in their own super chargers. It's not apples for apples.

 

[MountainBoy]

Not really, the bigger plug allows flexibility for I/o connections where Tesla's one is proprietary. Tesla were ahead of the game and have invested heavily in their own super chargers. It's not apples for apples.

It's only "proprietary" in the sense that Tesla funded the development and engineering of it. They have offered it royalty free for over a decade to whoever wants to use it. I'm not sure the technical "ownership" is particularly relevant if anyone who wants can use it. It's a much more elegant standard than the committee developed CCS standard that was adopted later by legacy car manufacturers.

Tesla wisely combined the Level 1, level 2 conductors (home and destination charging) with the level 3 (DC fast charging) conductors for ease of use, elegance, and cost savings in the manufacture of both charging handles and vehicles. It's a superior standard but legacy auto thinks they can use a different standard (CCS) as a moat to try to isolate Tesla. Ironically, the Tesla standard is, by far, the most common EV charging standard because legacy auto has proven they don't want to make electric cars at high volumes or support EV's with charging infrastructure.

I don't know if the Bosch charger has the same kind of considerations, but I think the explanation of heat dissipation, and longevity (reliability) probably do contribute to the larger size and weight. It would probably cost a lot more to manufacture something with similar reliability and robustness in a lighter package. Bicycle chargers are not intended to be packed on the bicycle, if that were the case, they would have built the charger into the bicycle (like cars have done) and only need a connecting wire to the line current. Instead, the charger is separate and has the AC to DC rectifier and voltage regulator inside.

 

[Bigfathairybiker]

Is that the inside of a bosch charger?
Looks like a pretty run of the mill switching power supply.
I take it the switching chips are underneath?

Bosch's cost of building a switcher like this is peanuts, probably around a fiver or less each.

Oh, and yes, the larger the heatsink the better the reliability ... usually...

I'm surprised they didn't include a small fan, but , then again, that would have introduced a problem of crud blocking the fan vents and a point of failure.

I currently have the 2 amp version which gets pretty hot , but not hot enough to worry about.
Strapping an ali heatsink to the top is a nice simple way of increasing reliability.
Extending the internal heatsink outside the case is not such a good idea as it is probably at mains voltage!

 

[MountainBoy]

View attachment 98074
and of corse one of the hex bolts is a smaller size, and yes it still works

I don't understand what you are saying here. I assume this might be an earlier generation Bosch charger but I have no way to know that. Or to tell its relative size. Or what the significance is of one hex bolt being a smaller size or what you are comparing it to.

Edit: I should have refreshed the page before I replied! So, the point is, it's been reliable?

 

[MountainBoy]

View attachment 98074
and of corse one of the hex bolts is a smaller size, and yes it still works

It looks like they've done a substantial redesign between then and now. This is the charger that came with my Gen 4 system this year:

It's relatively dense inside the case with considerable heat sink material. I think they could make it 30% smaller and 30% more efficient with less heat to dissipate, by using higher quality components, for perhaps 50% more cost but do eBikers want to pay for that?

 

[Slapbassmunky]

Both chargers look very well designed to me. They are both well packaged, the components are well supported and have proper heatsinking, with appropriate electrical separation & low ESR caps where needed. They're not mill spec by any means but appear to be decent commercial units, they will cost a fair bit more than a fiver to make as it's not the usual Chinese crap, but yeah bosch making a fortune out of them.

I'd imagine they've already worked hard on maximising efficiency given that they're passive cooled, as has already been said fans tend to cause trouble and of course you loose any semblance of IP rating. I think it's wise they're sealed units given they might be charging outside or jammed into a crud filled camelback.

It's very rare to find any modern electronics with heatsinks sat at line voltage, even in sealed units. The H&S police have generally put an end to all that and most of the time components are available (at the lower power end) that are fully encapsulated.

Yes you could shrink it down, probably to half the size or smaller, but the cost would absolutely rocket.

 

[Doomanic]

I don't understand what you are saying here.

No one ever does.

 

[Aussie78]

Saxon capacitors are a 2nd tier manufacturer at best.

Given the price of typical ebike chargers, I’d want to find Rubycon, United Chemi-Con, Nichicon, Elna or Samsungs, or good Panasonics being used.

Bet there has also been a cost down initiative and the most expensive active components are 2nd/3rd tier parts too. I notice the bridge rectifier is from TSMC so it’s not all bad.

Haven’t had to fix any bosch chargers yet. Many many are significantly worse then this. Love when the production manager okays the use of no name far eastern parts, like MOV’s that trip at 270vac, ignorant of IEC standards for mains voltage tolerances.

 

[RickBullotta]

Heat dissipation.