Bosch 36V fatpacks opened up

[theyerb]

Search ebay for "36v Universal Charger." Also, preferably a "smart" charger. You don't want a 36v SLA one!- they will actually charge it up to 44.5v rather than the 41.1v or so that you want. Here's an example of one I found on ebay:

http://cgi.ebay.com/Universal-Smar...n-Battery_W0QQitemZ280274682793QQcmdZViewItem

Charging 6 in parallel should be fine. An epic battery pack! Keep us posted.

 

[John in CR]

Yes 6 will make for a nice pack. For charging you might think about just getting the Bosch charger. Then you could leave the slot connector on one end of your pack, maybe even include the status of charge indicator. It would probably take 6hrs for a full charge, but slow charging and the more conservative charge level of 40.5V will make them last longer.

John

 

[D-Man]

Completed the pack...for now anyway.

I noticed that the no load speed with the Bosch pack at 41.5V is 0.9 mph higher than the SLA pack right off the charger which should raise my top unassisted speed to 17.0 mph Hey I'll take every little bit I can get.

Now I just need the weather to improve to get out and test it.

-R

What charger are you using? Does each pack have a fuse or are you using one? I am curious as to what voltage the Bosch pack will stay at under load and for how long. Keep up the good testing. My sla's are pretty worn out.

 

[Russell]

Completed the pack...for now anyway.

I noticed that the no load speed with the Bosch pack at 41.5V is 0.9 mph higher than the SLA pack right off the charger which should raise my top unassisted speed to 17.0 mph Hey I'll take every little bit I can get.

Now I just need the weather to improve to get out and test it.

-R

What charger are you using? Does each pack have a fuse or are you using one? I am curious as to what voltage the Bosch pack will stay at under load and for how long. Keep up the good testing. My sla's are pretty worn out.

Today I went on a test ride and got 6.085Ah (224Wh) from the 3-pack. I started the ride at 41.46V and ended after 25.50 miles when I hit the controller's LVC of 31.5V. The resting voltage was just over 34.0V at that time.

I just finished charging the pack using a 36V SLA charger. I monitored the recharge with a Watts-Up meter and disconnected power when the voltage hit 41.90V/6.051Ah/234Wh. The voltage immediately dropped to 41.70 and a few minutes later was 41.60. It should stabilize near 41.50 shortly based on the last time I charged it. The Li-Ion charger I have coming shold be preset from the vendor to stop and hold at 41.50V so I won't have to overshoot to get the voltage I want.

I left the 60A fuses that were hard-wired in the red leads just because it was convenient to do so. I installed an in-line fuse holder for the pack as a whole with a 25A fuse. The pack is currently used with a 250W Bafang motor and 15A controller. See more details here; http://www.endless-sphere.com/forums/viewtopic.php?f=6&t=8579#p146545

-R

 

[theyerb]

Holy cow- 25 miles!

 

[Russell]

I can never leave well enough alone so of course after assembling the battery pack and going on one ride I just had to take the pack apart and rebuild it. I broke it down (the RTV came off easily) and then installed the heavy rubber end panels. I removed the in-line 60A fuses since now they were in the way and I still had the 25A fuse for the entire 3-pack. Then I went crazy with the hot glue gun and the finishing touch was a top cover cut from a Lean Cuisine tray. The end blocks are RTV’d together and the whole pack is taped with electrical tape though that will be replaced with something stronger. The end result is the pack grew in size to 7.4”L x 6.2”W x 3.9”H and the weight increased by 11 ounces to 7 lb 6 oz (as shown below) or 7 lb 11 oz in the cardboard box, which is no longer needed for protection, but which I still used just because it fits so nice and snug in the rear trunk bag.







Today's ride results:

Distance: 32.2 miles (51.5km)
Average speed: 16.6 mph (26.6kph)

Amp-Hours used: 6.216
Watt-Hours used: 229.8
Min Volts: 31.63


Compared to the longest ride with the 36V/9Ah SLA pack the Fatpacks delivered 14.8% more Amp-hours, 18.6% more Watt-hours and did it with a 58% reduction in weight though volume is comparable (the fatpacks are fatties ).

-R

 

[D-Man]

So a 10 volt drop in overall voltage for this 36v Bosch lithium battery. So much for the flat discharge curve. These are basically like sla's minus the weight. Guess you got to aim high. I'd get one more Bosch pack and make a 2s-6p Booster pack to make up for the drop in voltage. Then get a charger at batteryspace for $20 bucks.

 

[theyerb]

How one earth are you getting over 30 miles on just 3 batteries?! I only get about 6 on two batteries And my 18ah of lead only gets me 20 miles.

 

[Russell]

So a 10 volt drop in overall voltage for this 36v Bosch lithium battery. So much for the flat discharge curve. These are basically like sla's minus the weight. Guess you got to aim high. I'd get one more Bosch pack and make a 2s-6p Booster pack to make up for the drop in voltage. Then get a charger at batteryspace for $20 bucks.

They pretty much follow the standard discharge curve for lithium batteries (see here: http://www.endless-sphere.com/forums/viewtopic.php?f=16&t=9268&p=143247#p143247 ) which is well over 1V/cell and not flat at all. In fact the standard discharge curve very much resembles the discharge curve of lead-acid just with a higher working voltage across much of it. I do find they are stronger than my SLA pack especially for the first half of my rides.

-R

 

[Russell]

How one earth are you getting over 30 miles on just 3 batteries?! I only get about 6 on two batteries And my 18ah of lead only gets me 20 miles.

The reasons are simple:


Low power Bafang geared motor w/top unassisted speed in low 17 mph range. Speed takes a lot of energy.

15A peak controller

I avoid using full throttle...most of the time.

Motor freewheels so it adds negligible drag. The bike rides just like it did before except for the added weight.

I started with a good quality bike that fits me well.

I ride at lower speeds than most e-bikers but a little higher than I could do on the same bike without the motor assist.

I pedal all of the time

Hills around here are generally limited to 4-6% with most terrain fluctuating in the 1-2% range.


If I used JUST the battery I suspect my range would be limited to maybe 10-12 miles.


-R

 

[lcyclist]

How one earth are you getting over 30 miles on just 3 batteries?! I only get about 6 on two batteries And my 18ah of lead only gets me 20 miles.

I can verify that it is possible to go over 20 miles with 3 fatpacks. On my 3 bat setup, I have already logged over 1000 miles using a high power motor (1000W BMC direct hub) with 20 mph average speeds with bursts over 30 mph.

After my roundtrip of 20 miles, I only use about half the capacity out of 6 AH (with pedal assist), so it is possible to go further. Most I have gone on this pack is 28 miles.

 

[Russell]

How one earth are you getting over 30 miles on just 3 batteries?! I only get about 6 on two batteries And my 18ah of lead only gets me 20 miles.

I can verify that it is possible to go over 20 miles with 3 fatpacks. On my 3 bat setup, I have already logged over 1000 miles using a high power motor (1000W BMC direct hub) with 20 mph average speeds with bursts over 30 mph.

After my roundtrip of 20 miles, I only use about half the capacity out of 6 AH (with pedal assist), so it is possible to go further. Most I have gone on this pack is 28 miles.

Wow, average speed of 20 mph AND only 3 Ah used...now that's efficiency. Obviously you also pedal constantly and are a very fit cyclist.

BTW, can you tell me what charge voltage you use? I used 41.5V the first few times but after monitoring the charge rate closely the last time I'm thinking I will reduce that to something closer to 41.0V at which point it appeared to be at 95% of the 41.5V capacity. I will do more testing when I get my dedicated Li-Ion charger.

-R

 

[lcyclist]

Wow, average speed of 20 mph AND only 3 Ah used...now that's efficiency. Obviously you also pedal constantly and are a very fit cyclist.

BTW, can you tell me what charge voltage you use? I used 41.5V the first few times but after monitoring the charge rate closely the last time I'm thinking I will reduce that to something closer to 41.0V at which point it appeared to be at 95% of the 41.5V capacity. I will do more testing when I get my dedicated Li-Ion charger.

-R

I am a road cyclist. Yes I pedal a lot and use the motor as assist to maintain speed. Bike setup is a steel hardtail MTB with setup with road cranks, overall weight is less than 50 lbs.

For charger, I use mainly the bosch fast charger, which charges the pack to 41V. I have used a 37V li-ion charger which charges the pack to 42V, which is the max charge spec for this pack.

 

[John in CR]

I have 5 of the bulky Bosch chargers that I've yet to use except to top off the packs when they first arrived. I finally got around to opening one up today as well as test them in series. I'll try to get some pics tomorrow, but they seem to be typical German engineering and look to be built to last. eg The 2 FETs each have a monster heat sink. Each puts out 3.9 amps and charge to 40.5V, so I'm going to combine 4 of them into a beefy 7.8amp 72V charger. I love the idea of conservatively charging a 1kwh Konion pack in less than 2 hours, which will effectively make my range infinite with reasonably short opportunity charge stops.

A higher power charger has become a top priority after hitting my LVC for the first time yesterday a couple of miles from home, because my 2amp charger just doesn't cut it as a traveling charger. I don't mind pedaling as long as I don't have to pedal.

John

 

[RealPeterPan]

Lads,

as there are a few "Team Konion" member here now:

What do you use as LVC?
Are you totally rely on the LVC of your controller?
I find that a bit risky (good efficient german paranoia
But as the big advantage of the konions is that they dont need balancing, I dont want to spend a fortune on a complete battery management system.

If you know any good 36V or 36-72V 20A controller which have a twaekable LV cut could you please give me some hints?!
I have a crystalyte reseller in europe now but unfortunately they seem to be just seller as they couldnt answer me if the crystalyte 36V 20a controller is adjustable up to 30V.

crystalyte.com mention 29V Cut Off +-1V.
Buty is this +-1V an adjustable or aberration range.

Thanks for your help.

Best Regards
Sven
--

 

[Russell]

One of the purposes of my first couple of rides with the Fatpacks was to determine the capacity I could expect from them...and now I know. At around 6Ah expended from my 3-pack the resting voltage is right around 34.0V and it'll sag to the LVC of my controller (31.5V) with a heavy load. Now I can simply keep an eye on my Watts-Up meter and know exactly how full the tank is at all times. Of course without a BMS there is no way to monitor each cell but as long as you're keeping tabs on the voltage I doubt there will be a problem. You don't need a WU meter necessarily, a simple voltmeter would suffice. So that's my plan; charge it up to 41.0-41.5V then ride until the resting voltage is around 34.0 or it sags to 31.5V on a heavy load. When the pack reaches 34V it feels pretty sluggish anyway so even if you had no meter at all you'd know just by feel, and of course by how far you've travelled, that you were running low.


-R

 

[TPA]

Hey Russ,

Can you identify the device in the pack that was used for temperature sensing? If it was a typical thermocouple, it would be possible to monitor the pack temperature (if the pack were left intact). I realize that you took your packs apart, but if you still have the pieces, can you post pics of those parts?

 

[Russell]

Hey Russ,

Can you identify the device in the pack that was used for temperature sensing? If it was a typical thermocouple, it would be possible to monitor the pack temperature (if the pack were left intact). I realize that you took your packs apart, but if you still have the pieces, can you post pics of those parts?

The little blue tipped device is the thermocouple.

View attachment Bosch 044.jpg


-R

 

[TPA]

I wonder if that is a T type thermocouple...no idea where to go from there.

Will look into it in the future when I order the batteries.

 

[John in CR]

I agree with Russell. An LVC is only to protect the batteries, and you have to know your voltage if you're going to be farther than you're willing to pedal home. The Konions give you a nice warning sign via a noticeable decrease in top speed, but at that point you have maybe a 1/4 of a tank and more voltage sag too.

Also, don't think of 3.7V (37V on a fatpack) as being the halfway point and turn around then. Even if that really is the halfway point of AH's, what's left is less than 90% of the WH's used above 3.7V . If you want to use voltage like a gas gauge in a car, then use 3.75V/cell at rest or higher (37.5V on a fatpack) as a pretty good "half a tank" point. Just like in a car, it's best to always keep it above 1/4 tank.

John

 

[XRuss]

Hi Russell, So have you been able to further test out you new fatpack? What do you think? Is it a worthwhile way to go?

 

[Russell]

Hi Russell, So have you been able to further test out you new fatpack? What do you think? Is it a worthwhile way to go?

I am quite happy with the Fatpacks. I'm using them with a Bafang motor and the extra voltage over the SLA pack they replace makes it run noticeably stronger, especially in the first 10-15 miles. I only draw 15A peak from my 3-pack but that's over 2C and I don't see much sag. I reduced the charging voltage to 41.1V from 41.5V for my ride today and really put it to the test. I rode yesterday and apparently didn't fill my tank because I was pushing hard and bonked (with no snacks onboard) plus I ran the battery down to the LVC of my controller (31.5V) and didn't have anything left for the last few miles. It didn't help that I had the wind in my face in one direction then it switched and was working against me on the way back In the end I travelled 33.6 miles and used 6.386Ah/233.0Wh. I would totally recommend these inexpensive tool packs as a way to upgrade from lead-acid.

-R

 

[trialsguy]

Could I build a pack without taking them apart? I bought (2) hammer drills for $330.00, which includes (4) batteries and (2) chargers. I am going to build a bicycle for my son with one hammer drill and I want to use the other for what it was actually intended. I did impulse buy what I think is a GM 36V 750W rear hub. I would think to most practical set up would be a motor by the front freewheel so you could have gears. But my impulse buy got me into the sport and I didn't realize speed equals really expensive batteries! I would like to make a six-pack in parallel so I could use however many batteries I can afford! At work I’m the engineer that comes up with ideas that are really out there and I am often criticized with coming up with solutions that are too simple. The drill has over 600 in-lbs of torque. Thanks for your input. Bob

 

[Russell]

Sure, in fact go to page 4 of this thread to see Theyerb's post.

I originally wanted the pack to be as compact as possible so I completely dismantled the Fatpacks however I changed my mind and reinstalled the original endcaps for added protection. If I put together another group of packs I might just solder some wires to the contacts, it all depends on space constraints.

-R

 

[pwbset]

Got curious so just ordered a fatpack for $45 shipped. Sheesh... that's seriously cheap. Going to hammer on it to see what it can do, but can always harvest the 20 VT cells to add to the 40+ raw ones I've already got.