Bosch! The good, the bad and the ugly!

[flecc]

He couldn't offer a refund as the shop would have to take the hit and NOT Bosch! How the hell is this fair? if im buying a 500w battery i want to get a 500w battery! not 410!!!

Not battery Watts, the measurement is in Watt/hours

The same is true of all batteries, regardless of make, Bosch being no different. That is because there is no such thing as a definite Wh rating since that depends entirely on the consumption rate.

I can illustrate this best by quoting a test A to B Magazine ran on a particular 36 volt 10 A/h battery. They first used the full battery content to empty riding on Eco with minimal throttle and found the full 10Ah present, so 360 W/h.

They then repeated the tests each time upping the rate of usage, normal mode. more throttle etc. To cut a long story short when using the power to the fullest extent they only realised 7 Ah capacity, so 252 W/h and a 30% capacity drop.

That battery wasn't defective, it would still give the full 360 W/h if used at a minimal discharge rate.

In your case i've no idea what discharge rate was being used by the tester to measure the capacity, but as you can see it can make a big difference.

Basically all makers give the rated capacity based on a very low discharge rate, so it's the best you can possibly get with very gentle usage. Go belting up hills in the highest power mode and you won't get anywhere near the same capacity.
.

 

[kingsknight]

I think you've missed the point. The owner of the shop is saying the capacity is way off, I maybe not using the correct terminology but the capacity is lacking. A 500 w/h shouldn't be testing the same(ish) as a 400w/h.

 

[GLJoe]

I think you've missed the point. The owner of the shop is saying the capacity is way off, I maybe not using the correct terminology but the capacity is lacking. A 500 w/h shouldn't be testing the same(ish) as a 400w/h.

I think its you missing Fleccs point. He is saying that a measured capacity value can change, depending on how you discharge it. Therefore an absolute quoted figure could be construed to be meaningless unless the discharge current is also specified.
That said, I would have expected Bosch to have a standardized method of measurement. Due to the nature of the Bosch system, it seems you can't just arbitrarily slap any old measuring device on one of their batteries, therefore the tester used must also have been a propitiatory Bosch one!
Therefore, if the reported figure of 412Wh is correct, something indeed seems fishy and wrong!

Anyone got info on what Bosch officially state the acceptable capacity range of their 500Wh batteries is? I can't believe this figure doesn't exist somewhere in some small print.

 

[soundwave]

 

[EddiePJ]

Kingsknight, who is the Bosch appointed dealership that you keep referring to?

 

[flecc]

I think you've missed the point. The owner of the shop is saying the capacity is way off, I maybe not using the correct terminology but the capacity is lacking. A 500 w/h shouldn't be testing the same(ish) as a 400w/h.

See Eddie's reply and reread my post. To repeat, there is no such thing as a fixed capacity, it depends entirely on the discharge rate, which is a variable of course. In my experience manufacturers quote the most favourable figure, which is the lowest discharge rate one and what we rarely actually experience.

That battery could be low on capacity but there's not enough information on the test method at the moment to be certain of that.
.

 

[flecc]

Anyone got info on what Bosch officially state the acceptable capacity range of their 500Wh batteries is? I can't believe this figure doesn't exist somewhere in some small print.

It seems they cop out of committing themselves Eddie. On their battery page they make these two references:

"The combination of two Bosch batteries delivers up to 1,000 Watt hours." Note the "up to" here and approx. below.

Then under Technical Details for their four battery types they say:

Energy content approx. 300 Wh - 400 Wh - 500 Wh - 500 Wh

https://www.bosch-ebike.com/en/products/batteries/
.

 

[GLJoe]

It seems they cop out of committing themselves Eddie. On their battery page they make these two references:

"The combination of two Bosch batteries delivers up to 1,000 Watt hours." Note the "up to"
.

Hi,
Not Eddie here.

I suspect you're reading too much into the 'up to'.
To me, that reads as "we give you a dual battery system .... so you can stick two batteries in ... 300, 400 or 500Wh batteries are available, so if you use two of the max capacity versions, then you can get up to 1000Wh ... different capacity batteries giving less total capacity..."

 

[flecc]

Hi,
Not Eddie here.

I suspect you're reading too much into the 'up to'.
To me, that reads as "we give you a dual battery system .... so you can stick two batteries in ... 300, 400 or 500Wh batteries are available, so if you use two of the max capacity versions, then you can get up to 1000Wh ... different capacity batteries giving less total capacity..."

I noted that but wasn't misreading. What I meant is that it doesn't trap Bosch into claiming 500 Wh each, just like the use of "approx" later keeps their claims vague.
.

 

[wheeliepete]

Another factor to consider is cell capacity is often measured down to 2.5v, well below BMS cutoff voltage, so there will be charge left in the battery when the discharge test is complete.

 

[Danidl]

I think you've missed the point. The owner of the shop is saying the capacity is way off, I maybe not using the correct terminology but the capacity is lacking. A 500 w/h shouldn't be testing the same(ish) as a 400w/h.

Was he using a Bosch certified battery tester or some generic device?. The capacity of a battery will depend on the discharge rate,and the temperature it is operating at.

 

[Trevormonty]

Battery capacity (C) is stated as their one hour capacity.
For example 12V 10Ahr gelcell would have capacity of 12Vx10Ahr = 120WHr. In theory deliver 10A for 1 hour.
In case of gelcells that capacity is based on their 1/10C (1A in this case) discharge rate over 10hours. If you discharge a gelcell at 1C (10A) its only good for 30-40minute resulting in measured capacity of 0.5-0.67C (60- 80WH).

Li Ion batteries can support significantly higher discharge rates. At 1-2C they can deliver full capacity ie 10A for hour or 20A for 30minutes.
There is catch, at these higher discharge rates the battery voltage drops due to losses in battery. .At 1C it maybe 13V while at 5C could be 11V. (These are example values not real ones, see battery discharge curves for real ones)

If you measure watthours (Volts * Current averaged over hour), the watthour capacity would be lower than stated but Ahr capacity would be correct.

So the Watthour rating of battery varies depending on load.

 

[Fat Rat]

I think you've missed the point. The owner of the shop is saying the capacity is way off, I maybe not using the correct terminology but the capacity is lacking. A 500 w/h shouldn't be testing the same(ish) as a 400w/h.

Hi
Has the shop tested both a new 400 and a 500 at the same time having both come off a full charge and left to settle for the same time period?
As already said there’s lots of variables for battery testing
Charge state
Ambient temperature
And discharge load just for starters
All will render different readings if varied even on the same battery
It’s not an exact science by a long way
Just a guide to battery health

 

[soundwave]

i can tell you how long it lasts if you hammer the crap out of it at about 1hr

or 25 miles on the flat or 10 miles up a mountain climb.