Fandomii

Hi all, I have a 2 year old Bosch PowerPack 500 and I’ve done 2500km with it. I’ve noticed that the performance the last couple months (winter) is really poor. I understand that the conditions play an important role, and I keep my tires at max pressure, but I think it’s down to 60% of what it was two years ago. It seems too much of a drop in performance. The battery has always been stored in a dry heated basement and taken good care of.

I took the bike to a shop and they measured the voltage at full charge: 41.5V.

Is that an expected number? Could I measure anything else (perhaps with a multimeter) to give me some more info on the health of the battery to see if I can make a warranty case for it?

Bald Paul

Bosch warranties that pack for 2 years or 500 charge cycles, whichever comes first. I doubt warranty will cover it.
That pack is rated 36v, so that 41.5v reading is questionable (unless it was just charged and reading surface charge.) More important than voltage is discharge rate (amps.) All batteries lose their ability to produce power over time. How you store it makes a difference. It should be stored fully charged and in a COOL state, according to Bosch.
It may just be nearing the end of it's peak service life. Get ready to either pedal harder, or pony up for a new battery.

Fandomii

Thank you for the reply - I understood that batteries should be stored at 60% charge and not fully charged. Also I think it would be completely ridiculous to expect that a battery like that has two years of service life. Is there a way to measure discharge rate?

Bald Paul

You are correct in storing at 60%. I misread the data sheet. Unfortunately, the data sheet only shows capacity, and not discharge rate. Besides, it wouldn't be easy to measure that. Be aware that operating in cold temps (winter) will also affect the battery output, so you may want to wait to see how it performs in warmer weather before replacing it.

2old

Sounds like it's 10s (10 batteries in series) so at full charge it should be (4.2v per battery for 18650) 42V. If your voltmeter is accurate, that indicates some loss. My 52v batteries (14s) are still at 58.5v after several years (theoretical 58.8).

veganbikes

You don't necessarily need max pressure on your tires, that doesn't really do you much good unless you are running tubulars with latex tubes and want the tires to be at the right pressure of the cobbles but we aren't talking that here. In cold weather your battery charge will deplete faster, batteries don't like it really cold or really hot. If you are losing significant milage in the winter you might consider the Fahrer Battery Cover. My plan was to get two for my R+M but sadly they were out of stock at our U.S. distributor till very recently (as it started getting warmer) but no real worries as I was mostly commuting and have plenty of battery to get me home and back a few times before I really need to charge.

It doesn't sound like there is any warranty case to be had unless the battery is malfunctioning. That doesn't seem like the case. If you are storing the batteries at around 60% in a temperature controlled environment you should be good but if you are regularly running down to zero and storing them at full capacity it can degrade the batteries over time. If you are in cold weather when you bring the bike in let it warm up a touch before you start charging. Charging it while it is still cold is not good and will also degrade things over time. I also try to turn my bike on indoors before I go out just to give it a better chance.

If you want more info on the battery if you have a good Bosch shop that has the battery tester (which is an expensive tool a lot of shops might skip) they can use that to check the health of the batteries and all of that. It will probably cost something but is well worth it if you are worried. You can also pay them to put your batteries into sleep mode which essentially shuts them down completely to hibernate for winter or times you are not going to ride it for a long periods so it won't effect the battery at all. Then when you are ready they can re-awaken it and you will be in the same spot you were before it went into sleep mode.

Calsun

Measuring the voltage of a lithium type battery provides little useful information. The batteries are design to put out a high voltage level until they are very nearly completely drained, and that is a good thing. A pulse load type battery tester is needed to see what the capacity of the battery is when it has finished charging.

I use NiMh rechargeable batteries with my photo gear and when a standard battery tester shows them full charged I can put them on a pulse load tester and find that they have only a 80% charge. They still put out 1.2 volts which is why the standard tester fails to indicate that there is a problem.

When a battery is failing it will charge faster as less charge is needed to get it "full". Think of a car with a big dent in the gas tank that as a result holds 20% less fuel when the gas pump shuts off and so it takes less time to "fill up".

fooferdoggie 

you going to lose about 20% in the winter on a bosch battery pack. the shop should be able to give a detailed printout on the battery cycles and condition. bosch stands b behind their stuff they replaced my motor 5 months out of warranty. I had 14,000 on my battery pack and its still going strong.

speedy25

I dont agree with the loss comment in the above post. I have batteries that stay charged through the seasons with no problem.

An actual Bosch approved shop can run a diagnostic to see if its functioning OK. Ive only had one battery actually go bad.
In my shop I also have a load tester and I run batteries through 3 cycles to see if they match the claimed output.

-SP

Fandomii

Thank you got the excellent write up. I did not know that it was best to let the battery warm up to room temperature before charging it! Much appreciated.

I bought a neoprene cover for the battery to give it a bit of cold protection, but I don't think it made a significant impact. It's hard to test though... Different temperatures every day, different wind conditions. I do think the physics behind it make sense and will keep the cover on nonetheless.

I asked the shop to provide me an overview of the battery status and they printed out that I've done 36 full discharges over the last two years, and that the voltage was at 41,5 fully charged. So the performance during the winter should not be 35% less of what I was used to, two years ago.

I guess I'll try to find another shop that has a more advanced battery tester and ask them to do a test. Many thanks for your time!

veganbikes

There is only one Bosch battery tester and probably a lot of shops won't get one because it is expensive but if they have one it will open up some more info and allow other things to be done to the battery for storage and such.

The neoprene cover will help, it won't be the end all be all but it will keep it warmer just like you wear a jacket.

It sounds like though everything is OK and I wouldn't worry too much about it.

Letting things get to room temp is always good before charging sometimes you don't have the option but when you do you should do it.

Rad45

You may be talking about LiFePo3 batteries (3.2 volts per cell). They have an initial drop then remain almost constant voltage until they hit 10% or so. Lithium ion (3.6 or 3.7 volts per cell) drop in voltage at a pretty constant rate. I get about two miles per volt drop without pedaling, four or five miles with pedaling. That is for a 52 V, 12 AH pack.