[Jimdear2]

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

PLEASE!
Looking for help and advice.

Well, the money's put aside and 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. The $2000.00 or so is a big chunk for me so I have to get the best value I can.

The 72 volts we tried last season just didn't do it (of course the bad gearing choice I made didn't help).

100 batteries for the tractor and 4 spares. (the 4 will probably be used as a 12 volt control battery)

We plan to go with 50S 2P to start off this year and next year we will be adding 50 more batteries as we prove out the systems and home made controller until we reach a total of 200.

Looking for advice from people who sell and/or who have bought Headway batteries.

I can wait a while since pulling won't start until May of next year. I'll also be building a Simon/Jack charger and we are looking at various balancers.

 

[galeson]

I bought 540 for my build. I got them directly from Loraine. Everything totally above board. I had them sent directly to my house by air. The cost (including shipping, taxes and brokerage which Loraine took care of) was less than anything I have seen for sale domestically. I could have saved $2 per cell if I wanted to wait a few months if I had them sent by boat. You can always email her and ask. She usually answers quickly.

 

[dimitri]

Only 2P ? These are 10AH cells, right? How much battery current are you expecting to pull , pun intended... ?

2P sounds a little low, make sure you don't kill your investment prematurely.

 

[Jimdear2]

I bought 540 for my build. I got them directly from Loraine. Everything totally above board. I had them sent directly to my house by air. The cost (including shipping, taxes and brokerage which Loraine took care of) was less than anything I have seen for sale domestically. I could have saved $2 per cell if I wanted to wait a few months if I had them sent by boat. You can always email her and ask. She usually answers quickly.

galeson,

Thanks for the information.

The idea of saving up to $2.00 a cell for the slow boat from China shipping might mean a few extra cells. Since we are on the ragged edge of requirements, that may make the difference. To be honest I thought that the total cost from China and the cost from US suppliers was pretty equivalent.

I'll search up Lorrain's email and get with her for a quote.
Did you get link plates and the snap together pack pieces from her as well?

Have you decided on a BMS?

Jim

 

[Jimdear2]

Only 2P ? These are 10AH cells, right? How much battery current are you expecting to pull , pun intended... ?

2P sounds a little low, make sure you don't kill your investment prematurely.

dimitri.

You are right, we are right on the edge of minimum requirements. But thanks for the concern.

The batteries should give 20C, thats 200 amps per string. Pulls generally last about 15 seconds in the class we are aiming for. The first 1/4 of the pull is lightly loaded we also are planning on the controller to limit the current. so we are hoping to get through by being careful.

We have also discussed going with 33S 3P but that may drop the voltage too much to allow us to build enough momentum to keep the draw down for the last part of the pull.

Every thing is a trade off.

I also figured with the big tax increases next year to pay for all of the Obamanations plus no cost of living increase for social security AGAIN, I better get in now before the government takes it all.

Jim

 

[dimitri]

We have also discussed going with 33S 3P but that may drop the voltage too much to allow us to build enough momentum to keep the draw down for the last part of the pull.

Power is power, so 33S 3P will put the same stress on cells as 50S 2P , since decrease in voltge means proportional increase in current. The only way to address it is to add more cells, either 50S 3P or 33S 4P.

I have no hands on experience with stressing Headway cells to their limits, but I would check with someone who does. I think CroDriver has HeadWay pack in his BMW racer and he is likely giving it run for its money.

I would not just assume the cells can handle 20C just because the spreadsheet says so. Heat management and busbar connections become a concern when running at max C rates as well.

 

[galeson]

The 38120P cells are 8Ah. Back on April 9 Mike Willman posted his testing of the P cells. He got up to 60C, but he heated up the cells considerably. Who knows how long they will last with this kind of abuse.
I bought the snap together pack pieces and link plates from Lorraine also. They were about 1/3 the price.

 

[DavidDymaxion]

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

Just curious -- I thought folks added weight for tractor pulls? Might this be the rare case where the weight of lead acids could be a virtue? Just curious why the trouble and expense of lightweight, high power lithiums. Are you trying to get below a certain weight for a class?

 

[Jimdear2]

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

Just curious -- I thought folks added weight for tractor pulls? Might this be the rare case where the weight of lead acids could be a virtue? Just curious why the trouble and expense of lightweight, high power lithiums. Are you trying to get below a certain weight for a class?

David,

The class weight I am trying to match is 1350 lbs. with driver. The ICE tractors in that weight class are allowed up to 1500 cc engines.

Right now we have about 160 lbs slack for batteries with my partner in it (I'm too heavy to drive it) the eventual 200 cell battery we want will weigh just about that. There are size limits, length and width as well, we just physically can't fit enough lead into it, never mind weight.

 

[Jimdear2]

The 38120P cells are 8Ah. Back on April 9 Mike Willman posted his testing of the P cells. He got up to 60C, but he heated up the cells considerably. Who knows how long they will last with this kind of abuse.
I bought the snap together pack pieces and link plates from Lorraine also. They were about 1/3 the price.

galeson,

We saw that too. I know that the 38120 P are 8 ah, I just used the 10 ah figure David used to simplify the reply.

We plan on air cooling for sure and even discussed CO2 expansion or Ice Pack cooling. We are going to limit ourselves to 20C for starters. I'll be contacting Lorrain tonight as well as any US distributors as I find them.

Have you used the snap together pieces yet. Are the pretty strong. Pulling tractors don't have suspension and the tracks can be rough, never mind the slam down from wheelies. Do you think they could stand the abuse?

Again thanks for your comments.
Jim

 

[Jimdear2]

Power is power, so 33S 3P will put the same stress on cells as 50S 2P , since decrease in voltge means proportional increase in current. The only way to address it is to add more cells, either 50S 3P or 33S 4P.

We are thinking that 50S 2P to start off is the way to go because we want the higher voltage. The first 1/4 to 1/3 of the pull is where you build speed for momentium. By going with the higher voltage you get more speed before the transfer load starts increasing drag. Same power gets you further because you can store more inertia in the lightly loaded portion of the pull

I have no hands on experience with stressing Headway cells to their limits, but I would check with someone who does. I think CroDriver has HeadWay pack in his BMW racer and he is likely giving it run for its money.

I would not just assume the cells can handle 20C just because the spreadsheet says so. Heat management and busbar connections become a concern when running at max C rates as well.

There have been a few high load tests run that I have been reviewing and it looks like 20 C for 15 or so seconds is possible as long as you rest, cool and recharge between Runs. Since we rarely hook more then twice a day, with sufficient recharge/balance time in between. We only do 15 or so pulls a year we so hope we can get through the first year with a 100 cell battery.

We will see.

We will be contacting CroDriver as well as anyone else we can think of who are using the Headways.

Please keep your thoughts coming, they are helping. If enough of you convince me I really need to go to 150 batteries to start off instead of 100, I'll try to squeeze my 401K for more resources.

Jim

 

[galeson]

The plastic assembly blocks are made to very close tolerances. They are very hard to lock together until you figure out the proper sequence and then they are very easy. The bus bars hold the pack together on alternating sides, so if it was to come apart it would be like a fan(the old paper type. I haven't had any problems so far. If you make rectangular packs you could put straping around the whole thing and I'm sure it wouldn't come apart.

 

[rwaudio]

I'm just playing with 12 cells (10ah) at the moment for testing and the plastic blocks are "delicate" I don't think they would hold up on their own, but they do a pretty good job of aligning the cells for assembly and then use some form of banding and the bus bars to hold it all together. You should also go big on the bus bars, the last thing you need is to loose any of that precious power in connections.

I do agree that you should probably do your best to up the cell count, my "sporty" conversion will use 630 or 720 of the 10ah headways, on an 11" motor. Your 13" motor and 100 cells seems like a bit of a miss-match.
In my case 630 is the minumum cell count to get the most out of the controller and that is still using the cells upto their peak (15C for the 10ah) Perhaps the small lead cells (Hawker??) that White Zombie used before switching to lithium might be an option, I don't know anything about them though, just a thought.

What kind of HP/torque are the gas pullers putting out? Electrically before losses/motor efficiency your 100 cells have ~85hp I'm not sure how quickly your wheels get up to speed but if you only have 400 motor amps at speed that would probably be 130-160 ft-lbs on the 13" motor but probably not at very high rpm. I could be wrong but I was under the impression that for an application like yours the smallest motor that can handle the power you are putting in is a better way to go. So until your batteries masively overpower the motor you are just hauling around dead weight that could be batteries.

On the other hand seeing a small tractor with a 13" motor would just be cool, good luck and show them what an EV can do!

 

[frodus]

One thing I did with the cell holders, is since they are tight, on the one end of the cell, take some of the plastic covering off (use an xacto knife to remove the heat shrink that would sit inside the holder). I did this and they're just fine.

And as far as using only 100 cells, I agree, you'll need to go higher.

Yes they'll do 20C, but with that higher current comes voltage drop. The more you draw the worse it gets. I'd suggest putting multiple batteries in parallel, then series to get the voltage you need. Also, at higher discharge rates, the cycle life decreases, so you might be buying a pack sooner than you think.

And if the voltage drop of any single cells at 20C is too high, you'll need to immediately sense this and cut off the pack, or you could reverse a cell and ruin it.

 

[Pirape]

In a configuration of ex 20s1p do the headway's need to be balanced?

If so, how?

 

[Alexander_B]

you need a balancer or bms, or "cell shield" type bms devices, little pcb's that connect to every cell and make sure its not overcharged, and when its near full, use a transistor/resistor combo to bypass some of the charging current, untill eventually all of them are full/passing all the charge current trough the resistor, and thus balanced.

the cheapo way is to connect all the cells in parallel, and charge them all at once, a good idea to do once before assembly, charge all the cells to the same level, that would balance them out quite nicely already.

 

[frodus]

but with a pack that is pulling so many amps like that, the batteries will come out of balance pretty quickly.

I'd almost opt for individual chargers for each cell and only have a monitoring system onboard to detect LVC.

 

[Pirape]

but with a pack that is pulling so many amps like that, the batteries will come out of balance pretty quickly.

I'd almost opt for individual chargers for each cell and only have a monitoring system onboard to detect LVC.

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

thanks,

 

[galeson]

There is a very interesting thread over on the endless-sphere. "Bringing Headways back from the 0V grave."

 

[jackbauer]

Jim you might find these guys of interest:
http://www.ecitypower.com/

They have a 38120 p cell for 13.50usd. I'm getting a few samples for testing.