Aussie EV Autocross Special

[galderdi]

I think I am screwed. This guy has sold me this pack as a 150v pack. It certainly is at 150v at the moment. But it is supposed to be at 210V (I think). If that is the case it will trip my controller's over voltage protection (aything over about 175v).

So now I have a big decision.

I could just run the larger portion of the pack (4KwH) but this would only run at 122.4v (not ideal)
or I could just stop charging when the pack gets to about 170v

and of course this all assumes I can find a suitable charger. Grrrrrr
I had a response from EV Power - They do not support this chemistry.
Still waiting on a response from Zeva and EV Works.
The task is made more difficult by the fact most advice on the forums is refering to chargers plugged into 110v AC wall sockets while we run 240v ac here.

 

[galderdi]

I might be in luck. A local guy is selling a charger and some other bits that might get me out of trouble.

Can I get a Dc to Dc converter to drop from 210V to 150V ? what would I search on.

If I search on "DC to DC converter" I get too many results to be useful and if I search on "Dc to Dc converter 210V to 150V" I don't get any useful results.
What are the likely brands?

 

[Samd]

Awesome stuff~!

 

[oatnet]

I might be in luck. A local guy is selling a charger and some other bits that might get me out of trouble.

Can I get a Dc to Dc converter to drop from 210V to 150V ? what would I search on.

If I search on "DC to DC converter" I get too many results to be useful and if I search on "Dc to Dc converter 210V to 150V" I don't get any useful results.
What are the likely brands?

The DC-DC converters I have worked with deal with lower volts and amps, and waste a lot of current as heat, which you would need a cooling system to handle.

Earlier I recommended a controller like a Zilla or Soliton that takes in a higher battery-side voltage and bucks it down to what voltage you program on the motor side. My POS Kelly converter did not do this, but in the end it was lame in every aspect. I don't think I saw mention of what kind of DC controller you have, maybe it is a buck converter too, what are its battery-side voltage limits?

As for voltage, how many cells are in your pack?

-JD

 

[galderdi]

The controller is a Curtis 1231C. It is designed to run at 144v but is ok ish up to about 170v before the overvoltage protection shuts the controller down.

I do like the concept of some of the other controllers, but I can't justify the additional outlay for a "toy". If it is a choice between running 122v or spending another coupel of thousand I would have to choose 122V (reluctantly). Or maybe I'll win lotto.

The larger module holds 34 cells and the smaller holds 25 cells.

I am not confident enough to disassemble the modules and the risk that brings. I did think about somehow bypassing a few cells (to bring the total voltage under 170) but leaving the deactivated cells in the module. I don't know if that really reduces the risk all that much (if at all).

I'll try to upload a pic of the modules

*Edit* Wait I just realised I already posted that pic a few days ago

 

[galderdi]

Here is a better profile pic of the larger module from the side. The pic was taken before the cells were compressed back into their final position thus sealing the cooling galleries.

 

[oatnet]

I have no practical experience with volt cells, but I can use The Google like a boss: :lol:

http://www.schultzengineering.us/delta-11-12.htm
The above page seems to indicate that (3) 15ah pouches are paralleled into a single 45ah cell, and the module you have pictures is actually a pair of 12s3p blocks, 24s3p overall. Your smaller module is probably a 12s3p block with a 6s3p block, for 18s3p. Combined they are 42s3p.

http://avt.inl.gov/pdf/EREV/batteryvolt3929.pdf
The above page references a 3.7v/cell nominal rating which would be 155.4v nominal for your pack. This is good news, because if you really had 58 cells and they were at 150v, they would be at 2.58v/cell and likely permanently compromised.

At a 170v limit you would be able to charge them up to 4.04v/cell, which is just shy of the 4.06v indicated by the Shultz engineering page. The 18650 LG cells I see that are rated at 3.7v nominal actually charge up to 4.3v (vs INR cells that are 3.6v nominal but charged to 4.2v) so I am surprised that is so low. Shultz also indicates the cells are good for 10 second bursts of 8c (350a) but I haven't found anything that corroborates this. Worst case, you get less cycles from your pack from too high a discharge rate, but honestly I think by the time that becomes a problem you will have found something newer/better. If you paralleled 2 of these packs c rating would be less of a concern but introduce other challenges. Now you see why I prefer the 30c discharge of a123 packs.

I got a Zilla 1k for $750 on eBay; I would have saved myself a lot of $$$ and hassle by going to the Zilla instead of mucking about with the Kelly (which is a cheap Curtis clone). Curtis is a good brand, so you will probably have a better experience, but I'd still consider a Zilla or soliton more of an investment than a toy.

 

[galderdi]

Awesome. This is great news and does seem to match the facts better. You have made my day/ year.

So now I plan to pick up the second had charge and better cooling pump tonight. Connect it all and test over the next 36 hours and all going well leave for the event early Friday morning. My main challenge is stopping the drips from the cooling system. But I am hoping the new pump will help solve muchof the problem

 

[galderdi]

Also 8c for 10 seconds should be fine. I figured my minimum requirement to be 7c. My only nervousness would be around the rest required between bursts. Time will tell. I probably should install a mirror so I can see the flames, sparkes and spewing lava from behind me.

 

[galderdi]

Now that I have some confidence in the setup I have them their first test. They work great in my yard and I seem to be pulling about 210amps peak. So thats great news. But it will likely be higher on bitumen.

Now off to get a charger.

 

[Dauntless]

http://www.evmotors.com.au/products/fb1.html

Someone else said they had your same motor and mentioned this. Is that right?

I'm curious what this actually weighs. I assume under 1,000 pounds/440 kilos.

 

[galderdi]

Its actually 500kg. I could have made it a heap smaller and lighter but wanted 2 seats and a broader base for higher speed events. I actuall came in about 100kg less than my original target.


so now I have the charger. But it requires a CAN bus signal before it will charge. I got an old bms as part of the deal. But it won't work in my batts. Any hints how I can get the charger to work?

 

[oatnet]

Awesome. This is great news and does seem to match the facts better. You have made my day/ year.

Glad it helped, and that you were able to get a test run in! Earlier you mentioned the car was 700kg, was the conversion from lead to lithium what got you down to 500kg? That is the same as my mostly-fiberglass dune buggy with the same motor and 100kg battery. I guess I thought all that steel frame would weigh more, but it gives me hope that my next project, on a sandrail frame, will be just as light.

Looking forward to seeing video of an upcoming street runs!

-JD

 

[galderdi]

During the build I was guessing/aiming for 600kg. But I think 700kg was a pesimistic estimate. At the end of the build I weighed each end and the total was about 530kg. Then I weighed it on some weighbridge scales and it came in at 600kg and I put the difference down to inaccuracy of my home measurement method. But then I weighed it on the same weighbridge and it cam in at 530kg again. So there must have been a problem with the weigbridge the first time. Now I figure the lithium has saved me about 30kg

 

[galderdi]

OK so there is some hope. I am reading the manual for the charger. There are two options for operating the charger, the first is the CAN Bus, the second is an enable pin. In theory this should work for my short term objective.

I should be able to connect the charger and connect a small voltage to this PIN and charge the battery pack.
I will closely monitor the state of charge to ensure the pack does not exceed about 160v (giving me a buffer so no individual cells are over charged)
I will only do this twice. Once to top up the charge tonight and again for a fairly full charge on Saturday night.

After that I will not charge the pack again until I have a working BMS (I don't want to get the cells too far out of sync).

But this is all just a theory at the moment. I will see if it works in practice tonight.

 

[kiwiev]

Can you get a probe into the cell terminals?

I really doubt they will get too far out of sync, I know of lots of EVs that don't run a BMS. My Sonic only runs a Lv and Hv circuit mainly so other people can drive it without running the batteries off the edge

But really a Ah counter from ZEVA will count your pack down and the charger will turn off at a predetermined voltage.

Do you have a phot of the charger?

Cheers Kiwi

 

[galderdi]

Here are the pics.
I guess I have seen the nighmare stories / photos of the results of cooking batteries. I don't want to end up there.

At the moment I have taped plastic over the top of the batteries. This is just in case it rains during the event. I can't get past it to the terminals through the tape and plastic at the moment. But I can/will remove it once I get home which would expose the terminals.

 

[kiwiev]

Is that charger an Alcon?

looks like it.

You should really call your car Mad Max

Cheers Kiwi

 

[galderdi]

It is.
Maybe Mad Max Volts

no luck with the charger. I tried all sorts of options. The one that surprised me was the enable option. So simple yet it didn't work??? I am getting the battery disconnected error. I checked my connections and there is no problem. Led me to believe its set for different voltages and as a result doesn't recognise my pack. So I found the instructions for changing the charge curve but for some strange reason can't get it to enter the setup mode. I am out of time tonight. I need to finish the cooling tomorrow morning and the load up for the trip. But any ideas would be greatly appreciated as I will have more time tomorrow night and saturday night.

 

[galderdi]

So I went to Rocky.

I managed to squeeze 5 runs out of the car without using a charger. That was a little disappointing because one more run would have meant my points would count in the championship. 5 runs was less than half (by one run) of the first day.

The car felt quick at the time, but I have since seen the times and apparently it felt quicker than it really was. I have quite a few ideas to improve. I'll keep you updated.

I now need to focus on getting a working charger, even if that means getting a model charger to charge each cell individually. I have until April 24 to make sure I have a fully operational/charged car.

Here is the first of my videos from Saturday:

[youtube]u2nfdy3kj4o[/youtube]

 

[galderdi]

[youtube]Bxj7ZqVJhaQ[/youtube]

 

[galderdi]

[youtube]g7epSjIqddc[/youtube]

 

[galderdi]

[youtube]O9CbBrgZKl0[/youtube]

 

[galderdi]

[youtube]axelddvOrcM[/youtube]

 

[galderdi]

I have a dumb question:

As I have previously discussed in this thread I am still deciding what to do about monitoring and protecting my cells.
Looking at some of the cell cards available on the net (ranging from $1.50 - $3 per cell). Some of them are refered to as BMS modules. Some are refered to as protection/ balancing circuits.
so that got me thinking. What is the advantage of having a Batrium PACMON style device over having these on each cell?
If I understand correctly central style BMS gives the following advantages:

• PC interface
  Heat monitoring
  active cell isolation in the case of a faulty cell
  Voltage and current displays on dash

I that is accurate I think I might skip the BMS in favour of just having the protection balancing circuits.