[frodus]

can you give me a link of the LVC or BMS that would be perfect for headways?

thanks,

Our BMS from Manzanita Micro or one from Elithion
www.manzanitamicro.com
There are others, like MiniBMS but I'm not as familiar with them. I would absolutely avoid the cheap chinese BMS boards, as they have a high failure rate.

LVC means low voltage cutoff, its not a product, its a feature that a BMS should have to protect from overdischarge.

 

[Zuglet]

Re: Need Help, Going to buy Headway's for the Big 13 Pulling tractor

...we are ready to buy 104 Headway 38120P batteries to power the 13 inch motor in the pulling tractor.

I'm looking for the best value since I'm retired...

Hi Jimdear2,

I've been gathering data on various batteries for use in EVs and you might want to take a look at what I found. Go to the the list of batteries on the following page and sort by 'Watts (max)/pound.' The best batteries will appear at the top of the list. You can click on a battery to do some pack calculations...

http://www.zuglet.com/batteries/batteryList.php

The HeadWay batteries certainly offer the benefit of the screw terminals -- but, the maximum power density (per pound) is considerably (50%) better on the A123 and Panasonic Lithium batteries. You will have to put more batteries in parallel -- but, it might be worth looking into.

 

[Jimdear2]

Re: Need Help, Going to buy Headway's for the Big 13 Pulling tractor

Hi Jimdear2,

I've been gathering data on various batteries for use in EVs and you might want to take a look at what I found. Go to the the list of batteries on the following page and sort by 'Watts (max)/pound.' The best batteries will appear at the top of the list. You can click on a battery to do some pack calculations...

http://www.zuglet.com/batteries/batteryList.php

The HeadWay batteries certainly offer the benefit of the screw terminals -- but, the maximum power density (per pound) is considerably (50%) better on the A123 and Panasonic Lithium batteries. You will have to put more batteries in parallel -- but, it might be worth looking into.

Zuglet,

That is quite a nice bit of work there. I'll be looking through it for a bit.

I know the A123s are more power per pound but the difficulty in getting them, working with them and the cost per unit all put them on a second choice list for me in this application. Since we will be stressing the pack we will want to be able to disassemble and repair/replace without major work.

This chart should be made available to more of the people on the DIY site. I recommend that you place it in it's own thread.

Jim

 

[Harold in CR]

Re: Need Help, Going to buy Headway's for the Big 13 Pulling tractor

Just a thought, have you looked into the Nano-Tech R/C batteries from Hobby King ?? They are rated at 50C-to 90C discharge. Charging can be 20 minutes or so, IF you have the means.

Guys are using them for absurd e-bike use and abuse. They are pouch types. One guy even did some welding with a large series of those packs, tied together.

Might want to browse around on the Endless-sphere forum ??

 

[Yabert]

Hi Jim

How many Amp can delivred our controler?

I use Headway 38120S 10Ah on my suzuki DRZ coupled at a 700A controller. In my 26S 3P configuration the voltage drop at 2.3v per cell at 600A (20C) in the first second (1-2 sec.) of acceleration. After my small motor isn't capable to pull higher Amps.

If you use 1000A controller the 2P configuration will be not enought!!!
Depending of your gear ratio you probably need more Amps (torque) and less voltage (speed).

So, for a bit more money, a configuration 30S 4P could give to your 13" motor a good power for 15s. But you will be over the battery spec!!
Use headway at 30C discharge probably reduce a lot his life....
But it's probably a good test for not to much money....

Good luck!

 

[Zuglet]

Re: Need Help, Going to buy Headway's for the Big 13 Pulling tractor

...have you looked into the Nano-Tech R/C batteries from Hobby King ?? They are rated at 50C-to 90C discharge

Thanks Harold,

I hadn't looked at these batteries so I added one of the 6 cell packs to the list. These lithium-ion polymer packs come in above the A123 batteries when the list is sorted by 'Watts (max) / pound' -- they also rank real high when sorting by watt-hours / pound.

http://www.zuglet.com/batteries/batteryList.php

Thanks for the tip.

 

[Harold in CR]

Re: Need Help, Going to buy Headway's for the Big 13 Pulling tractor

There is a thread on ES about pulling a starter motor for 6 minutes, I believe, on a Honda Civic.

Also, pulling a starter motor on a High tech Ford v-8 engine, for less time. batteries took the load, still take a charge and still have not blown up.

They come in different voltage packs, lighter in weight, and the guys that are into serious battery tech, are becoming very enthused.

 

[Jimdear2]

Hi Jim

How many Amp can delivred our controler?

Yabert,

The controller is still under developement. My partner (an EE) in this madness, has bought a bunch of 600 volt 400 amp IGBTs and is slowly collecting the necessary stuff to do an at least 1000 amp 300+ volt controller using the Paul and Sabrina board.

Otherwise I keep looking at the other high end big voltage big current controllers. We will see how he does.

I use Headway 38120S 10Ah on my suzuki DRZ coupled at a 700A controller. In my 26S 3P configuration the voltage drop at 2.3v per cell at 600A (20C) in the first second (1-2 sec.) of acceleration. After my small motor isn't capable to pull higher Amps.

If you use 1000A controller the 2P configuration will be not enought!!!
Depending of your gear ratio you probably need more Amps (torque) and less voltage (speed).

So, for a bit more money, a configuration 30S 4P could give to your 13" motor a good power for 15s. But you will be over the battery spec!!
Use headway at 30C discharge probably reduce a lot his life....
But it's probably a good test for not to much money....

Good luck!

I have decided, after all of the advise I have recieved, to purchase 155 38120P 8 ah cells for their high C rating with decent capacity.

We will use them in either a 50S 3P or a 36S 4P configuration. with the extras as spares. We need fairly high rpm from the motor to keep the wheels spinning but still need grunt when the weight transfer box starts loading the pan, with the 36S and 4P configuration we are looking at 800 amps at 90 volts. Assuming the cells maintain at least 2.5 volts when under max C. we may change to a 50S 3P pack if we don't have enough wheel speed or need al of the power at the end of the pull.

The actual power curve should look something like 110 to 115 volts with maybe 300 amps for the first few seconds (5 to 7) then slowly rising to peak at at as much as 800 amps at 90 volts for the last 2 or 3 seconds. Total time span 13 to 18 seconds. eventually we want to get to a 50S 4P pack. Total gearing could vary from about 4 to 1 up to 20 to 1 depending on the sprocket selection.

There are so many variables it may take years to get it right. With tractor pulling you generally get one try to get it right. All of the tuning is done in your head. No practice or tuning runs. Thats part of what makes it fun

So you have pretty much confirmed that I am on the right track. THANKS.

Also want to tell you how very impressed I am with the quality of craftmanship on your bike. With a little tweeking and optimizing of the overall bike design as a true electric I believe it would compare favorably with any comercial product out there.

Be well,
Jim

 

[Jimdear2]

Re: Need Help, Going to buy Headway's for the Big 13 Pulling tractor

There is a thread on ES about pulling a starter motor for 6 minutes, I believe, on a Honda Civic.

Also, pulling a starter motor on a High tech Ford v-8 engine, for less time. batteries took the load, still take a charge and still have not blown up.

They come in different voltage packs, lighter in weight, and the guys that are into serious battery tech, are becoming very enthused.

Harold,

They do look enticing but they are just a bit too leading edge for my pocketbook. I'm going to go with something a bit more mainstream to start out. There are just too many variables involved without throwing in something else new.

Maybe when we get ready to hit the sand drag tracks where you need BIG power for 3 or 4 seconds, I'll look again.

Thanks for your input, hope a few others follow up because this looks interesting.

Jim

 

[Harold in CR]

Re: Need Help, Going to buy Headway's for the Big 13 Pulling tractor

Fully agree with your decision, Jim. Have been following your threads. Neat stuff you are doing.

Down here, it's damn boring.

 

[jackbauer]

Jim i thought i'd post some of my headway testing data here if you don't mind ? did'nt really want to go starting another thread. Cell pac used is a 4s2p pack of 8ah p cells. Some charges and discharges had already been carried out on this pack prior to today. I also used them to test a few chargers i purchased. Sadly these chargers aim for 3.65v per cell which , without a bms, causes overvoltage.

The first graph shows a 1C (16A) constant current discharge followed by 5A and 2.5A discharges to get as much energy out of the pack as possible.

Next i used a 12v 65w car headlight bulb to try a very rough bottom balance. I got all the cells to 2.85v +/- a few mV. They were then placed on a 10A constant current constant voltage charge to 13.8v total (3.45v/cell) until current dropped below 0.8A.

I next used my much battered "solar" battery tester to load em up to 400amps to check if the cells kept in line under severe discharge events. They did. As usual , the old battery tester started pouring smoke so i had to abandon that phase. The voltage dip on cell 4 was caused by a loose wire on the cellog.

Finally i recharged at 10A to a cv point of 13.75v. To my amazement the delta v of the pack diminished to as little as 2mV at times and i think leveled out to 14mV at cv point.

I have the data files in text format if anyone wants to veryify the fine print. Cellog interval was set at 2 secs which i admit may have been a bit coarse.

My "gut" tells me the start of the charge knee is somewhere between 3.45 and 3.5v per cell. I could also quite plainly see capacity differences in the cells today. cells 1 and 4 were lower than 2 and 3 as the former hit the charge and discharge knees much earlier.

 

[Jimdear2]

Jack,

Thanks for the info, I was getting just a little antsy about what the voltage sag would be at a full 25C. It looks like a 2.4 volt per cell or so from your data. I can't tell how long you were able to hold that load.

I guess we will try a 38S/4P layout to start. thats about 130 volts nominal at 3.45 vpc. If we can keep the sag to 2.5 volts that's still going to leave us about 95 volts.

I've went ahead and bought an Open Revolt kit that I plan to eventually run on my Cub Cadet, I might just try it out for starters on the Big 13. Darin, my partner in this thing, has a bunch of BIG IGBTs and capacitors and is planning on a 300+ volt and 1000+ amp controller to use for when we finally can afford and get the total 50S/4 or 5P pack built. The big pack is for sand drags.

We will probably be running some very similar tests to the ones you did on our batteries. Mostly we will be seeing if they will individually come up to 3.5 volts and then sustain, say a 175 amp load while maintaining +2.5/2.6 volts for 15 seconds. We have some big electric bus Brake resistors we will be using as a fixed load. Then we want to see what the resting voltage will be. From there I'll bottom balance them to a common voltage, and build each series layer and do a charge to 3.45 volts per cell and see how thay balance out then do a load and again see how they balance out.

The idea is to look for cells that don't maintain standards. Manzanita Micro only gives us a 2 week warranty on DOA so I have to get them checked fast.

How does that test program sound? Any suggestions for anything else I should look for?

Jim