Building a small A123 Battery Pack
- Thread starter jerrysimon
- Start date
Hi Dan, (thnks for the PM BTW!)
My DIY special is in this thread: http://www.pedelecs.co.uk/forum/electric-bicycles/4984-my-first-entry-into-world-e-bikes.html
Its a direct drive Chinese 500w motor 24v but I'm running is a little 'hot' at 26~29v. Battery is a bank of Turnigy 5000mAh Lipos configured as 15Ah 7s3p, no idea what the controller is!
My DIY special is in this thread: http://www.pedelecs.co.uk/forum/electric-bicycles/4984-my-first-entry-into-world-e-bikes.html
Its a direct drive Chinese 500w motor 24v but I'm running is a little 'hot' at 26~29v. Battery is a bank of Turnigy 5000mAh Lipos configured as 15Ah 7s3p, no idea what the controller is!
Ok my Turnigy meter turned up yesterday.
Not a bad little unit for just over £20. Is small, seems well made and has a rubber case. I don't think it is waterproof as there is a vent grill on the back. The wires are huge which makes sense given the claims it can read up to 130amps
Anyway the display gives Volts, Amps and Watts then the fourth display cyles through various readings like Ah, Max Amps, Min Volts etc. That was a surprise as I thought it only displayed real time not max and min values. This is good as I can now see any surges.
Here it is roughly fitted to the bike. Was dead east to fit and in this position I should be able to see it when I take it out for a test ride. Display remains all the time it is plugged into the battery although you can plug in a small auxilary battery to keep it on all the time I think, as well as read below 4.6v down to 0 volts. Otherwise it takes power from the source or load depending on what's connected. It is backlit as well. I also will be able to put it in line when I charge the battery, so I can see how much charge goes in.
I haven't had chance to take it out yet but did a quick test at full power with the wheel off the ground. Readings shown
The peak amps registered at 1.8amps. I will report back further once I have taken it at for a ride. Way too cold at the moment.
Regards
Jerry
Not a bad little unit for just over £20. Is small, seems well made and has a rubber case. I don't think it is waterproof as there is a vent grill on the back. The wires are huge which makes sense given the claims it can read up to 130amps
Anyway the display gives Volts, Amps and Watts then the fourth display cyles through various readings like Ah, Max Amps, Min Volts etc. That was a surprise as I thought it only displayed real time not max and min values. This is good as I can now see any surges.
Here it is roughly fitted to the bike. Was dead east to fit and in this position I should be able to see it when I take it out for a test ride. Display remains all the time it is plugged into the battery although you can plug in a small auxilary battery to keep it on all the time I think, as well as read below 4.6v down to 0 volts. Otherwise it takes power from the source or load depending on what's connected. It is backlit as well. I also will be able to put it in line when I charge the battery, so I can see how much charge goes in.
I haven't had chance to take it out yet but did a quick test at full power with the wheel off the ground. Readings shown
The peak amps registered at 1.8amps. I will report back further once I have taken it at for a ride. Way too cold at the moment.
Regards
Jerry
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Hi Jerry, seems to do the same as the Watts UP. Like the backlit display though neat touch. 130Amps? not with those wires LOL!
To get an idea of the current draw under load without riding apply the brake and then open the throttle stalling the motor, you only need to do this for a few seconds at most...
To get an idea of the current draw under load without riding apply the brake and then open the throttle stalling the motor, you only need to do this for a few seconds at most...
The wires are pretty thick. Certainly I would be happy with them up to 60amps and I am not going anywhere near that. The instructions do say only 130amps for a short burst or it will get warmHi Jerry, seems to do the same as the Watts UP. Like the backlit display though neat touch. 130Amps? not with those wires LOL!
To get an idea of the current draw under load without riding apply the brake and then open the throttle stalling the motor, you only need to do this for a few seconds at most...
Good idea about the applying the brakes to simulate riding conditions. These Tonxins have to be be treated gently though, so not sure I would want to stall it.
Regards
Jerry
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I tried doing this on my Bafang but it just didn't "feel right" (made me cringe every time). The peak figures obtained in real-world conditions (hills and wind) are much more relevant
Jerry, does the Turnigy power meter resets its min/max values every time the battery gets disconnected ?
Cheers, Dan
(15cm snow here, so far)
Yep.
Though as I say you can connect up a small auxilary battery. On my arrangement the switch is just before the controller so as long as I don't unplug the battery it remains on. This should give me time to take the bag off and then note readings before I disconnect it.
(No snow here, Cambridge YET) EDIT *** spoke too soon its started snowing!
Regards
Jerry
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No, I dont think it would be possible, when using a shunt the volt drop across the resistace derives the current measurement.
Herb
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Video review here:
YouTube - TURNIGY POWER ANALYZER WATTMETER REVIEW by Doctorbass
From the "power meter" thread:
http://www.pedelecs.co.uk/forum/electric-bicycles/4821-watts-up-vs-turnigy-power-meter-analyser-3.html?highlight=watt+meter#post64377
Cheers, Dan
These kits look like they could ease the construction of battery packs on :
Products
RC-Network.de - Akkulution
Products
RC-Network.de - Akkulution
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Well finally the roads here have cleared so I went out for a ride the first in a week of so
Actually got to test the Turnigy meter in a real environment. Even back lit its quite hard to read so perhaps I need to mount it closer to my old eyes on the handle bars. I used the throttle a lot.
Quite interesting readings some matching what I expected and a few surprises.
On the flat if I am pedaling it barely goes over 1-2amps. On a small incline it goes up to 4-5amps but drops back to 2-3amps if I pedal.
On a steeper incline it goes up to about 8amps with me pedaling and about 10-12 if I stop.
Interestingly I had a peak of 17amps
The 15amp fuse didn't blow so it must have been for a m/s or so.
The total ride must have been about 5 miles though I don't have a trip computer fittted yet, must get one.
Readings
17.04 Ap
576.6 Wp
33.74 Vmin
1.69 Ah
61.8 Wh
Perhaps someone could help me with the Wp and Wh readings and tell me what these help show ? Can I work out more performance stats from my battery from these figures ? I assume the 33.74 Vmin was when I drew 17.04amps given the battery is 39.6v nominal ?
With 1.69Ah taken out the battery that leaves me 0.61Ah and its reading 39.13v so still 3.26v/cell assuming they are balanced. Thinking about it the battery is probably nearing discharge as I doubt it holds the full 2.3Ah though there was power left when I returned. I have to say I did not notice any drop in power really on the whole ride though, perhaps there was a fraction more if I didn't throttle for a bit and then tried again a few minutes later.
My cycle to work is about 5.25 miles so I think I probably could do a return journey (10.5 miles) on one charge, if I don't throttle a lot. I can easy take the charger to work or by a second one though.
Regards
Jerry
Actually got to test the Turnigy meter in a real environment. Even back lit its quite hard to read so perhaps I need to mount it closer to my old eyes on the handle bars. I used the throttle a lot.
Quite interesting readings some matching what I expected and a few surprises.
On the flat if I am pedaling it barely goes over 1-2amps. On a small incline it goes up to 4-5amps but drops back to 2-3amps if I pedal.
On a steeper incline it goes up to about 8amps with me pedaling and about 10-12 if I stop.
Interestingly I had a peak of 17amps
The 15amp fuse didn't blow so it must have been for a m/s or so.
The total ride must have been about 5 miles though I don't have a trip computer fittted yet, must get one.
Readings
17.04 Ap
576.6 Wp
33.74 Vmin
1.69 Ah
61.8 Wh
Perhaps someone could help me with the Wp and Wh readings and tell me what these help show ? Can I work out more performance stats from my battery from these figures ? I assume the 33.74 Vmin was when I drew 17.04amps given the battery is 39.6v nominal ?
With 1.69Ah taken out the battery that leaves me 0.61Ah and its reading 39.13v so still 3.26v/cell assuming they are balanced. Thinking about it the battery is probably nearing discharge as I doubt it holds the full 2.3Ah though there was power left when I returned. I have to say I did not notice any drop in power really on the whole ride though, perhaps there was a fraction more if I didn't throttle for a bit and then tried again a few minutes later.
My cycle to work is about 5.25 miles so I think I probably could do a return journey (10.5 miles) on one charge, if I don't throttle a lot. I can easy take the charger to work or by a second one though.
Regards
Jerry
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Jerry, great work
I believe the 576.6 Wp is the maximum watts you have used sinse the reset
This ties in with the max current of 17.04A at min volts of 33.74V
17.04 x 33.74 = 575 watts
The battery should have a capacity of 2.3 (Ah) times the voltage (say 37V - a figure in between the actual of 39.6 and the lowest 33.74)
2.3 x 37 = 85.1 wh
so you have probably used two thirds of your battery capacity
Hope this helps
Herb
I believe the 576.6 Wp is the maximum watts you have used sinse the reset
This ties in with the max current of 17.04A at min volts of 33.74V
17.04 x 33.74 = 575 watts
The battery should have a capacity of 2.3 (Ah) times the voltage (say 37V - a figure in between the actual of 39.6 and the lowest 33.74)
2.3 x 37 = 85.1 wh
so you have probably used two thirds of your battery capacity
Hope this helps
Herb
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It will be a while before our roads are clear I imagineWell finally the roads here have cleared so I went out for a ride the first in a week of so
Hi Jerry undersized in terms of Ah vs current draw.Thanks.
Sorry to be stupid but what do you mean by undersized
It seems to work ok.
Regards
Jerry
576 Wp is the Peak watts since the last reset. 17 amp is over 7C discharge rate and the voltage sag tells the story IMHO. Where on your run and for how long do think this happened? It may not be an issue if your commute is fairly flat.... I have a 15Ah 20C capable pack on my DIY bike and peak power is 850W, the voltage sag though is just 0.6v (29v to 28.4v, 7s3p Lipo based) under these conditions...
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