In addition to the 24v 10ah pack I also bought a 36v 10ah pack. This is meant for my Electra Townie, WE 36v BD motor w/ 35A controller. I've also bought a 36v 15ah pack and it's due to arrive soon. But this is some test results with the 36v 10ah pack.
On wednesday I started to ride it to work but the pack cut out 2-3 times in the first 1/2 block so I took it home and rode a motorcycle instead. Today I wanted to test it more carefully.
First test.. I have a big honkin variable resistor that's rated for 300+ watts. Using that I could demonstrate 20+ amp discharges. I don't remember right now the specifics.
The voltage does dip quite drastically. At the fully charged state it's 46v. Since it's should be an 11 cell pack that works out to 4.1818 volts per cell. However it quickly drops to 42v and as the discharge rate rises the voltage drops down as low as 36v. I haven't observed a full discharge so I don't know the extent of this.
The pack did cut out a couple times during this test.
I installed the pack again on my bicycle and took it out for a spin. First I simply held the wheel off the ground and let it run w/o load. Even at full throttle it didn't run over 10A discharge but applying the brake a little raised the discharge rate above 20A.
Riding it I was able to experiment a little with where the pack is cutting out. This occurs between a 20A and 33A discharge.
Clearly with this pack on this bicycle I'll have to be extra careful with the throttle. And clearly that's going to be hard to do. However at moderate throttle this bike moves reasonably well. And the throttle is a little sticky and can be set to hold a 6A discharge rate which provides a very nice assist.
The BMS part of the pack was a bit warm after 5-10 minutes riding around.
The ratings are:-
Rated voltage: 36v Capacity: 10 AH
Weight: 3.5 KG
Suggested load: 400 watt, max load: 700 watt
CHarging voltage: 46v (max)
Charging current: 5A (max)
Rated discharge current: 10A
Max continuous discharge current: 20A
Cut-off current (max current): 35A +/- 5A
Power in Motion has the same problem in this video:
http://www.youtube.com/watch?v=IZ3c9pcWu_8
Please let us know if the performance improves at all with a few cycles.
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Pic from http://www.electri
If it is lithium-phosphate, the nominal voltage is 3.2 volts per cell, so your numbers are about right. The voltage at end-of charging needs to be higher to obtain a full charge. I can be up to 4.2 volts, but most people with experience using these Li-FePO4 seem to recommend no more than 3.7 volts per cell, which extends cycle life, at the expense of few percent capacity.
Yes these are LiFePO
I took a long ride today.. made a circle of about 7 miles or so. The ride took a bit over 5AH, and it handled itself fine.
I found it really nice to set the throttle at its sticky point -- like I said above, the throttle on this bike is a little sticky and will stay 'on' at a level that draws around 5A. It made for a very laid back ride on a nice spring day.
- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
So the battery pack performs better then what it's specifications say? What is your conclusion so far?
Thanks, Deron.
Actually it performs worse than the specs. Specifically the specs say the cutout is 35A but it's easy to get it to cut out at 20-25A.
However my conclusion is that for this pack -- his 10AH packs -- that it's suitable only for low power bicycles and the like. This pack isn't suitable for high speed bicycling. I've also bought a 36v15AH pack from him (kinda by mistake) and will give it a similar test when it arrives. The pingping 15AH packs have higher discharge ratings (double) and should work much better with this motor and controller.
Many places have rules requiring electric bicycles over 250 watts to be registered or simply not allowed. At 36 volts 250 watts equates to approx 7A. For most of that ride I took yesterday was at or below 7A. It was a pleasant laid back ride, which is about all you can expect from a 250watt bike, right?
- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
Well, I rode the bicycle all the way to work today. That's a 10 mile commute. The battery held up very well through the whole ride and the voltage stayed above 36v almost all the way. It took approx 1 hr to make the commute though. The riding style was light pedaling and keeping the throttle at this sticking point I mentioned above where the current stays at approx 7A (or 250 watts).
Unfortunately I messed up and lost the amp-hour and other measures the meter makes (it's a Watt's Up).
The ride is wholly flat with the only "hills" being an overpass (or two) and there are two underpasses I took where riding up the far side counts as a short hill. I was able to stay in the max gear, no pedaling, and use the motor to ride up one of these "hills" that came towards the end of the ride. It drew over 20A at that point (over 700watts) and the voltage dipped down around 34v.
Other than the 1hr each way commute this is really nifty. Unlike SLA battery packs this is light enough I didn't notice the weight, and it was like regular bicycling.
Again, this is the 36v10ah pack.
- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
I've been testing a single 36 volt 20ah ping pack on my Viento. Now there is no way this battery can run the bike (275amp controller and perm 132 motor geared for 42mph top speed). So I've been testing it as a range extender in parallel. I found the cut out on the BMS to be low (32 amps). I needed peaks of 60amps (with the Hawkers supplying the other ~200amps) and modified the shunt on the BMS to kick out just over 60 amps. The cells are rated for peaks of 3C so I'm still in spec. The power FETs on the BMS have held so far with the extra amperage just fine. In this application the results have been very good.
I also hooked the battery up to the Voloci and took it for a 17 mile ride (16ah used). Here the ping battery is working all alone. The Voloci has a 40 amp controller and actually peaks at 42amps so again it would have not worked without a mod to the BMS current shunt. The performance was about the same as the original NIMH that came with the bike. Top speed is a little higher with the LiFePO4 than the 13ah Nimh. After a couple of weeks of various testing I'm pleased with the battery except for the stock BMS cut off amperage. The Voloci pulls about 20 to 22 amps cruising at a top speed of 25 - 26 mph.
I can see how asking anything more than 2C would be disappointing with these batteries working alone. By (2C) I mean the controller amp limit on lower power systems being 2 times the capacity of the battery. The Viento really askes much more averaging about 1.5C discharge rate from the LiFePO4. I don't think I would want to pay for enough of these to run a high power system within their current limitations. But as a hybrid battery pack with Hawker lead doing most of the heavy lifting, they are perfect. Properly sized on a lower power system they are a big improvement over lead. Assuming the cycle life holds up to twice the cycle life of lead.
Aerowhatt
I too have a ping battery (48V 20ah). How did you modify the shunt to allow up to 60 amps? I don't know if I would need that much, but 40-45 would be great.
Modifying the value of the shunt is pretty easy. Basically you just want to reduce the resistance of the shunt incrimentally until you get the desired cut off. I just used very fine strands (hair like) of copper wire soldered across the shunt on the back side of the board.
Aerowhatt
I don't suppose you or anyone else on the forum have a photo of what this looks like. Like I said, I am totally a NOOB at all this and don't want to fry my BMS.
I have a photo but don't know how to post it on this forum. I could email it to you.
We are talking about the ping BMS that comes in yellow shrink right? If you have a battery with the blue shrink then the proceedure is a little different.
Aerowhatt
I just sent you a private message. Not sure if that comes to your email or what. Thanks again for your help.
V is for Voltage has a Tutorial which will show you how to load images on V is for Voltage for use in posts.
Chas S.
Thanks Chas
I hope this doesn't require learning. I'll check it out.
Aerowhatt