Bosch 36V fatpacks opened up

[liveforphysics]

As far as the capacity differences go, temperature plays a HUGE roll in both Ri, and capacity.

John lives in beautiful and tropical Costa Rica. I would imagine his batteries are generally around or over 100F while being discharged and getting +1.3ah/cell.

If the same pack were to be discharged in a colder climate, the discharge results could be very different. I remember flying an RC heli on a 30F deg day. The pack was full when I started. I got 3mins of fairly easy flying from a pack I normally get 5-6mins of aggressive flying out of.

It's tough to say a cell is 1.X Ah, or xC-rate without having a temperature spec to go with it, because temperature makes a minor difference with some batteries, and a major difference with others.

 

[John in CR]

pwbset,

I'm just going by the 1.5 and 1.6ah reported by the guys who have measured the V's. If you're climbing a mountain daily, then you definitely should want more batteries. Of course the additional batteries will more than carry their additional weight over the mountain. Also, you guys with the "just enough to get by" size packs will have lower real world capacity from your cells, since you are draining them at a higher C rate. I'd just use the ah rating for comparison purposes for which I believe 1.25ah for the VTs is perfectly fair, and for real world use I'd recommend staying below 1ah of discharge. Cutting it close will cost you more in the long run by premature death of your packs, and will end up leaving you stranded.


Ultraman,

The packs should arrive with nearly a full charge. If the voltage is low, I say pack it up and send it back. The charger not willing to charge it is another issue. You definitely don't want to connect a low battery to your other ones. I think the recommended balance when connecting batteries in parallel is for them to all be withing 1 volt of each other. Otherwise high current will flow from the battery pack with a higher voltage.

John

 

[John in CR]

Luke,

Yes, this is the tropics, but here in the central valley temps are much more moderate due to the altitude and constant cool breeze coming off the mountains. At my old house temps were typically low to mid 70s year round, but it's a bit warmer here at the new one and mid to high 70's with maybe some low 80's if the sun is out at midday.

John

 

[pwbset]

Also, you guys with the "just enough to get by" size packs will have lower real world capacity from your cells, since you are draining them at a higher C rate.

That's a hell of a good point.

And... for what it's worth at 48 deg north even this time of year it's not unusual for my morning climb to be in the upper 30s/low 40s... could definitely play a role also.

 

[ToughRowToHoe]

I should mention that three of these packs fit nearly perfectly in this bag that I was asking about earlier:

http://www.niagaracycle.com/product_info.php?products_id=1261

I used a handlebar bag figuring I didn't want to add more weight to the rear of my bike. I purchased a GM 500W rear motor and I have a child seat on the rear. The bag looks like it was made for it. I left the Bosch packs together to protect the batteries and I'm using lugs plugged into the terminals. I did have to add some 1 inch straps and those snap-on clips.

The 1/2 inch straps that come with the bag look like they'll pull out under the weight, are hard to put on and pull off, and loosen while you ride if they are the only things holding it up:
View attachment 2

I just duct taped the bricks together:


Just plugged some lugs into the battery slots. Picked up the lugs from Home Depot. Still have to solder them, but they are working fine:

 

[John in CR]

Don't people like riding their bikes when it's sunny? No way I'd put my batteries in any black container that gets exposed to the sun. I'd think the batteries would get hotter than recommended just while parked in the sun, yet many use exactly that.

John

 

[Russell]

A few quick points:

I keep a record of every ride and I have NOT found that the outside temperature makes much difference in the capacity I get from my battery packs. I keep my pack indoors until I'm ready to ride and don't ride below freezing.

While I have just 3 fatpacks I also use a 15A controller and discharge the pack typically over a 1 to 2 hour ride so I'm not pushing these batteries hard at all.

I charge the Fatpacks to about 41.3V which is above the level of the stock Bosch charger so I should get a little more than the rated capacity but I don't.

All three of my Fatpacks were at 35.9V when they arrived which is well below half full. I don't know if Bosch charges them up fully and the batteries I got were old or if they charge them to say half as should be done for storage.

In any event I have gotten a maximum of 6.4Ah from my 3-pack for what it's worth.



I would like to get my hands on a known freshly manufactured Fatpack to see how it would perform but so far I would say the 2.2Ah rating is probably a fair MAXIMUM one can expect from these packs based of course on my very limited sample. Has anyone here actually gotten more than the rated 2.2Ah from these packs and I mean specifically the Bosch Fatpacks not packs made of cells from other sources?

-R

 

[John in CR]

I have 10 of the fatpacks, and I can only say that I'm pretty sure mine have more capacity. I've only had a pack down to LVC once, and don't keep detailed records. I stopped worrying about capacities once I got comfortable that the better of my used V cells did in fact have almost 1.5ah of capacity. When you have the luxury of over 5kwh of capacity in Konion cells alone, not to mention LiFePo4 packs, all you worry about is keeping a good charge status on the various packs, so you can throw extra packs on for an extra long run that day.

I need to reconfigure some packs to cycle the fatpacks into my daily ride bikes, so I should wait until I gather better data before spouting off. I did get my packs from a forum member who bought them new, but never used them, though I seem to recall him saying that he received the Boschs with a good status of charge.

John

 

[liveforphysics]

Those cells optimal storage voltage is 3.65v/cell. If Bosch were to store them and ship them with higher voltages than that, they would be causeing additional aging to the cells for no reason.

 

[ToughRowToHoe]

I doubt the black bag makes any more than a nominal difference on heat. I don't leave the bike parked with the bag on the bike. When the bag is hooked up, the bike is generally moving and the bag is totally exposed to the air movement which helps dissipate heat. I think zipping the bag up probably makes a bigger difference though I could be wrong. Either way, the packs don't get warm to the touch. I haven't measured the temperature but I'm not really worried about heat. Maybe more of concern in really hot regions?

 

[John in CR]

I guess I use my bikes differently, ie as transportation, not recreational vehicles (though they are fun). My batteries stay on the bikes 24/7, and in something black it would be a real problem, obviously not while riding but while sitting.

Take a typical midday ride for example. When I go to pick the little one up after pre-K, I'll typically go to the store at least for milk (gotta go almost daily to buy the heavy stuff or else I have to break out the car. Next is a stop at the fruit stand to see what fresh stuff is in, and then a stop at the hardware store before a 5-10min wait at school. I have no doubt how hot it would be inside of any black battery container after sitting in the sun stopped for 20-30min in total. Throw in a trip to bank, and that's an additional 30min minimum parked in the sun unless it's just the ATM, so I can avoid the lines inside.

John

 

[pwbset]

Has anyone here actually gotten more than the rated 2.2Ah from these packs and I mean specifically the Bosch Fatpacks not packs made of cells from other sources?

I tend to think in watt/hrs and the fatpack I got has delivered 90wh before and I didn't rest the voltage very long, but it was around 27-28v after I did that (and dropping fast). That would be like 2.43ah at 37v nominal, which if they are marketing 2.2ah makes sense 'cause they certainly aren't going to LVC these packs to 27v. Anyway... I just assume ~80wh/pack normal usage and go from there.

 

[ToughRowToHoe]

I'm using my bike as transportation to and from work. The bag is pretty easy to attach and detach.

 

[stiffi]

Can somebody tell me what Amp charger I would use if I wanted to use one different from the Bosch stock charger?

Would I try to match the amperage of each Fatpack? If anybody has a recommendation on a brand, I would appreciate it.

Also, if I buy one, I'll be looking to get rid of my barely used Bosch charger for cheap, about $30. I just need to find something I can keep in my rack bag. The Bosch charger is just to big.

thanks for the help.

 

[John in CR]

Can somebody tell me what Amp charger I would use if I wanted to use one different from the Bosch stock charger?

Would I try to match the amperage of each Fatpack? If anybody has a recommendation on a brand, I would appreciate it.

Also, if I buy one, I'll be looking to get rid of my barely used Bosch charger for cheap, about $30. I just need to find something I can keep in my rack bag. The Bosch charger is just to big.

thanks for the help.

The Bosch charger puts out about 3.5 amps, so if you had 3 packs in parallel you'd still be charging conservatively with a 10amp charger. The issue getting away from the charger you already have is that it is tuned exactly for those packs with a nice conservative max voltage cutoff. Instead of getting rid of that charger you might consider reducing the size with you own packaging. You can only lose a bit of the triangle dimension, since that is the board's shape, but you can reduce the height by almost half. There are some tall caps and 2 tall heat sinks that prevent you from really shrinking it.

My plan is to take 4 of the chargers to combine them series/parallel to become one 7amp charger with an 81V cutoff, comprised of 2 7amp 36v chargers. Because I can turn one board over to fit the tall parts between those of the other board, I can combine 2 of the Bosch chargers into a smaller volume than a single stock charger.

With any modification of these chargers, be sure to ventilate them well, as they do put off some heat.

John

 

[stiffi]

whoa. Hang on.

If I have the packs paralleld, do I need more than 1 charger to charge the whole pack at once?

 

[John in CR]

whoa. Hang on.

If I have the packs paralleld, do I need more than 1 charger to charge the whole pack at once?

No, just one will charge any number of paralleled Bosch packs. Just divide the total ah of the pack by 3.5 amps of the charger, and you'll know about how long a full charge would take. I'm summing my chargers because I have 5 and want faster charging. I run higher voltage and have been using 2 Bosch chargers in series for several months now. The packs can handle 1c charging with no problem. That's 1hr for a full charge, and makes charging pretty darn convenient, which would be a 6-7 amp charger. If you're just getting started, then I'd suggest holding off unless money isn't a concern. Then later you'll probably have more packs and want a more powerful charger than the one you'd buy now. Make due for now by shrinking the packaging of the Bosch charger you have.

John

 

[stiffi]

So what happens if I charge with less amps? Will it just take longer? Is any amperage safe, so long as the voltage is 36 volts?

 

[John in CR]

So what happens if I charge with less amps? Will it just take longer? Is any amperage safe, so long as the voltage is 36 volts?

Ideally you want cutoff at 40.5-41.5V . Yes, any lower amperage is fine. Without the forced ventilation that comes with an intact pack on a Bosch charger I wouldn't go much over 1c during charging to avoid any heating of the cells, which reduces their life. 1c is the amperage to charge a depleted cell fully in an hour or 2.2-2.5 amps times how ever many of these Bosch packs you have in parallel.

Unless your riding is typically just a commute to work where you have hours to charge at work and how ever many hours at home, then you'll appreciate faster charging. The convenience of being able to fully charge a fully depleted in 45min to an hour is a beautiful thing. Then, if your charger is small enough to bring along, your distance capacity is as far as you want. Stop and charge while eating lunch, and get back on the road with a full pack.

Eventually I want to have a 1500W charger that is a small as possible. 1500W is about the max I'd want to suck out of an electrical socket of a stranger that I've asked to use an opportunity charge. I don't want to start tripping their breakers or heating up their wiring.

John

 

[TPA]

Most folks in this thread have purchased Bosch packs from eBay. Only one that I know of has purchased from the vendor on amazon (Max Tool) for 49.99 & free shipping
http://www.amazon.com/gp/product/B000JTBPF6/ref=ox_ya_oh_product

I thought you guys might be interested in what was received and in what condition. First a pic:View attachment battsm.jpg

As you can see, still in the plastic packaging. I ordered 6 of them and all appeared in equally good condition and got here in 4 days (California to Texas). My dear wife got these for me for my birthday....what a woman!!!

Voltages a received:
1. 35.7V
2. 35.8V
3. 35.7V
4. 35.8V
5. 32.8V
6. 35.8V

Pretty darn consistent with the exception of the one pack. I will try to charge it and see what it does.

A couple of people on this thread reported a code (K68830T 2006) on the battery that leads them to believe that the battery was manufactured in 2006. I searched the battery thoroughly and found no such code on any of these batteries (did they even have these batteries in 2006?).

Will edit the post later for the #5 low battery charged voltage.

Edit:

The #5 low battery comes hot off the charger at 40.9V. Looks like I'm in business.

The battery charges cool, but the charger gets mildly warm.

 

[pwbset]

did they even have these batteries in 2006?

That's a good question. Sony announced the V/VT cells in '04. A quick Google search reveals that Bosch announced the Fatpacks in 10/2006 and released them Nov. 1st 2006... so it's possible one of these packs is that old I suppose.

http://www.buildingonline.com/news/viewnews.pl?id=5565

I'm still amazed that I'm actually using my V "runt pack" made from leftover cells for my daily commute because it's providing plenty of oomph... much more than I anticipated. My poor main pack is just sitting waiting for the day the older greenies give out... may take awhile. These are incredible cells!

 

[stiffi]

If you more technically inclined folks would humor me....

Do you think this charger would work?

http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=4820

thanks,

paul

 

[stiffi]

Forgot to mention, I'm using 4 packs!

 

[John in CR]

Apparently it charges to 42V, so you may need a diode in the pathway to make the cutoff a bit lower. Seems a bit expensive for a 1.9 amp charger.

John

 

[stiffi]

So, nobody can recommend a good (yet smaller) charger for these packs? I'm having a hard time finding any 36 volt Li-Iion chargers, really

I'm thinking more and more about just sticking with the Bosch charger.

I would appreciate it, if anyone could point me to a particular replacement, however

thanks