PS My A123 cell suppliers now sell rather nicely made up 6s packs here

 

Support Britsh Industry - Order from Jerry

Lol it was traumatic enough making up my own packs, not sure I would want to turn it into a cottage industry. The margins would never be worth it.

 

Those made up packs are excellent value and take a lot of DIY hassle out of the equation.

 

Regards

 

Jerry

Ok now that I have had my first test ride on my E Brompton a few final posts on the batteries.

 

Here is a battery taped up and then covered in some 100mm shrink wrap

 

http://farm3.static.flickr.com/2793/4223228452_5707838206_o.jpg

 

They weigh between 480g and 485g so total weight including serial lead is about 0.97kg. I need to sort out some velcrose to strap them together.

 

After the first 3 mile ride (using a lot of throttle but mainly on the flat and a couple of inclines) I put them on charge using the cheap ebay charger referred to before. Within 40mins they were charged and the light went from red to green. Note for this charger the two 6s packs are connected in series. Thus this is charging them at 36V/1.6amps. Intially I don't want to run the pack right down. Once I have a few charges through, I will then test the full range.

 

http://farm3.static.flickr.com/2627/4222463501_f58c0945de_o.jpg

 

After the first ride the voltage was down at 39.7V i.e. nominal voltage of 3.3V/cell. Checking with the Turnigy they were all still in balance. After charging with the above charger I checked with the Turnigy and it had again brought the cells up to a balanced voltage of 3.6V/cell. So all looks good.

 

Over the next few weeks I will post updates on the condition of the pack. I am hopefull that this is a really neat, light and inexpensive battery solution for short journeys. We will see. To build this 2 * 6s, A123, 39.6V. 2.3Ah pack yourself incl the cheap ebay charger works out at about £75 using new cells, cheaper if you use ex Dewalt tool pack cells. If they don't need balancing that is not bad. If they do then the Turnigy charger adds about another £40. I may build a second pack later depending on how this pack performs. Even then as I said a second charger at work would work too.

 

Regards

 

Jerry

Edited December 28, 200916 yr by jerrysimon

I like your 12s battery layout, as the individual 6s packs (each with their own cell header connector) can be balanced individually using a cheap charger.

 

I'm looking into a layout that would allow me to use my spare Tongxin-powered 36V e-bike as a short distance runabout (i.e. low A/h capacity), but that could also be used as a booster pack for my main Bafang-powered 36V e-Brompton (i.e. not to add more capacity to my 10Ah battery, but to add extra voltage above 36V => more power)...just thoughts, I need to check whether it's technically doable (I'm not even sure my controller can handle anything above 36V nominal).

 

Cheers, Dan

Hi Daniel,

 

I've run 2 identical 24V LiFePO4 packs in series to make 48V but I believe the series packs should be the same type or at least similar. This setup ran just fine and didn't cause any problems. I don't know what would happen if you ran a much smaller capacity battery in series, which also had very different discharge characteristics.

 

Were you thinking of putting the 2 * 6S packs, paralleling them and then in series with your main pack? You might get away with that, but putting 36V of booster packs in series with your main pack, might make some probs...

Thanks ! I thought it would be a bit more complicated and I intend to do a bit more research before doing anything stupid

Ok another finalish pic of the 10amp blade fuse I have put on the 2 * 6s1p connected packs.

 

http://farm3.static.flickr.com/2683/4241171404_ba98f354f2_o.jpg

 

Once I get my Turnigy meter I may reduce this to 7.5amp if I can show that it does not draw more than that in my Tongxin/Brompton application.

 

Regards

 

Jerry

Don't forget to keep spare blade fuses (of various ratings) with you when you go for a ride

Ok another finalish pic of the 10amp blade fuse I have put on the 2 * 6s1p connected packs.

 

http://farm3.static.flickr.com/2683/4241171404_ba98f354f2_o.jpg

 

Once I get my Turnigy meter I may reduce this to 7.5amp if I can show that it does not draw more than that in my Tongxin/Brompton application.

 

Regards

 

Jerry

 

Don't go too low in value, you may want to rate the fuse at 150% of your peak current draw but no more than the current rating of your wiring.

Thanks guys. Yes at the moment I am carrying a 15amp fuse out when I go

 

All my wiring is rated at 15amp at the moment. Lets hope that when I get the Turnigy meter and find its pulling 20amps, I won't have to upgarde it all :o

 

Everything is running cool at the moment but then its below freazing outside

 

Concensus is that the Tongxin should not really have more than 10amps pumped into it anyway.

 

Regards

 

Jerry

There's a power chart here:

 

Hangzhou Zhejiang University Tongxin Electricity Company

 

Not sure if this applies to your motor Jerry but this seems to indicate approx. a max. 13A peak draw so maybe you have the correct fuse already....certainly no more than 12Amp at 80% efficiency....

Thanks for that NRG. I reduced the 15amp to a 10amp one today though I did not try it on any hills just the level. I have a 15amp one in the bottom of the bag should the 10amp blow whilst out riding.

 

Once I get the Turnigy Meter I can test everything in real time to comfirm

 

Regards

 

Jerry

I found that the Tongxin controller limits to 12A, as per the spec., with a brief peak of about 15A when you open up the throttle.

Just a quick update the 12v, 10amp fuse blew today so the 15amp fuse is back in :o

 

It happened when I let a colleague at work ride it and I think he just opened the throttle up to full. I also spoke to the electronic guys at work and they said its probably because its a quick blow fuse and the occasional surges progressively damage the fuse.

 

Anyway once I get my meter I can test the actual currents involved.

 

EDIT** oh thanks John I just saw your post which lines up with what your saying.

 

Regards

 

Jerry

...and the chart I linked to earlier LOL!

 

Just fitted a Watts UP to my DIY special and was shocked to see an 850W and 30amp peak 30amp is the current limit of the controller maybe I need to think about heavier gauge wiring :o

Just fitted a Watts UP to my DIY special and was shocked to see an 850W and 30amp peak 30amp is the current limit of the controller maybe I need to think about heavier gauge wiring :o

 

LOL, what's your e-bike motor+controller+battery setup ?

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!

Ok my Turnigy meter turned up yesterday.

 

http://farm5.static.flickr.com/4070/4250873088_57889fcd5e_o.jpg

 

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.

 

http://farm5.static.flickr.com/4071/4250873142_556d1f1d1d_o.jpg

 

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

 

http://farm3.static.flickr.com/2723/4250099983_ef28441a36_o.jpg

 

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

Edited January 6, 201016 yr by jerrysimon

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...

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...

 

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 warm

 

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

Edited January 6, 201016 yr by jerrysimon

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.

 

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)

Jerry, does the Turnigy power meter resets its min/max values every time the battery gets disconnected ?

 

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

Edited January 6, 201016 yr by jerrysimon

Is it possible to use the Turnigy with a remote sense resistor?

With a rear mounted battery & controller this would be a more sensible arrangement than having to run thick wires to the handlebars & back again.

 

Robin

Same Same

 

[ATTACH]1153.vB[/ATTACH]

 

[ATTACH]1152.vB[/ATTACH]

 

Mine is marked G.T.Power but looks like a dead ringer

 

Herb

Is it possible to use the Turnigy with a remote sense resistor?

 

No, I dont think it would be possible, when using a shunt the volt drop across the resistace derives the current measurement.

 

Herb

Edited January 6, 201016 yr by Herb