DIY Electric Car Forums banner

1 - 6 of 6 Posts

·
Registered
Joined
·
1,864 Posts
Discussion Starter #1
Just thought some of you who are planning to upgrade to Lithium cells as myself may have some questions to which I just got some answers for that you would be interested in.

I'm planning to increase my pack voltage to 160V to get more range (a little more pep won't hurt either:D) since I couldn't find acceptable cells to fit my truck. I've checked with people about the motor and controller at this voltage and apparently there's no problems being reported in the field. Below in italics is a post I put on another thread, followed by additional data.

Curtis Controller: Fresh off the phone with a guy I know who's factory authorized, did a warranty issue for my Curtis 1231C controller last year...

I told him I wanted to go to 50-51 cells and at 3.85 charge would come out to 196V while charging. Said he would prefer I stay at 50 cells to keep it at about 192 or so IF I charged to 100%. I would like to only charge to 90%, 182.5V and discharge to 80% if find that acceptable range wise.


Also asked him if he could set the low voltage to keep it at 2V per cell.
He said it's currently fixed at 60V but he could change it to whatever I wanted for $150. Said you have to open it up and seal it back up to do it.

He can also increase the max operating voltage AND current.
Said one guy wanted to run his at 250V so he changed the caps for 250V and upped his amps from 500 to 900. That is some control right there! I don't need that though, just want to drive wherever I need to go.

Now to talk to the motor people...

Advance FB1-4001A: Just spoke to someone about the motor which is rated at 144V. I asked him about this and was reluctant to give his blessings, which I understand as he wouldn't want to say "Yea its' aight" then I blow it up and get mad at him. So I asked him if he had any data from failed motors returned due to higher voltages issues.

He said he had one guy running at 213V all the time with success but had another user at same voltage drawing about 900A through it and finally burned it up.

I've read about several running it at 192V nominal successfully and he confirmed that. Or course he reminded me that they only recommend 144V max. CYA, I understand that.
 

·
Registered
Joined
·
4,054 Posts
You're using the pack voltage as an indicator of cell level LVC? Good luck. You should not be depending on the controller to monitor cell level LCV. You should monitor with something that can actually detect the 2V. The controller only detects pack voltage.

Changing out the caps is not the only thing that'l change the voltage to a higher voltage. There are many problems that come with doing that. Just ask Logisystems. Its not a simple matter of changing out the caps/diodes and FET's to a higher voltage. Other components need to change as well. If you do it, make sure you get a warranty and guarantee that it'l meet the higher voltage and higher current spec. Don't take his word.

See if "opening it up and sealing it back up" voids any warranty that you'd get.

I'd still say stay closer to the nominal rating of the controller. There's a reason Curtis says its a 144V controller. Its meant to go a little higher, but that doesn't mean that the controller is built to run at the higher voltage with less overhead. Inductance, voltage, current all play into how well the controller functions. It sounds like everyone is telling you to run at 144V but you want to push it. I'd say spring for higher capacity cells and just run 144V.

Who is this "guy" that is wanting to do this work? Has he done this on other controllers on the road? Does he have proof? I'm skeptical.
 

·
Registered
Joined
·
1,864 Posts
Discussion Starter #3
You're using the pack voltage as an indicator of cell level LVC? Good luck. You should not be depending on the controller to monitor cell level LCV. You should monitor with something that can actually detect the 2V. The controller only detects pack voltage.

Changing out the caps is not the only thing that'l change the voltage to a higher voltage. There are many problems that come with doing that. Just ask Logisystems. Its not a simple matter of changing out the caps/diodes and FET's to a higher voltage. Other components need to change as well. If you do it, make sure you get a warranty and guarantee that it'l meet the higher voltage and higher current spec. Don't take his word.

See if "opening it up and sealing it back up" voids any warranty that you'd get.

I'd still say stay closer to the nominal rating of the controller. There's a reason Curtis says its a 144V controller. Its meant to go a little higher, but that doesn't mean that the controller is built to run at the higher voltage with less overhead. Inductance, voltage, current all play into how well the controller functions. It sounds like everyone is telling you to run at 144V but you want to push it. I'd say spring for higher capacity cells and just run 144V.

Who is this "guy" that is wanting to do this work? Has he done this on other controllers on the road? Does he have proof? I'm skeptical.
Frodus take a Prozac and stop being so paranoid! Are you ADD like me and didn't read it before you posted?:D He IS A CURTIS AUTHORIZED REPAIRMAN. Besides, warranty was gone a while back, it's almost 3 years old.

In the interest of brevity, I didn't say replacing the caps was all he did, just mentioned to me that's one of the things he did. He's an engineer I think as well. And you don't ever ask me to be detailed, I have no problem with that anyway! :)

Re the LVC change I feel is just another measure of safety among the other things I will do. I HAVE NO PLANS TO RUN A BMS, though I'm going to have some monitoring system with LVC ability if need be, I'm not going to have it automatically balance my pack as I'm not fond of things known to cause fires. DC voltages at more than a 12V are dangerous enough anyway.

I didn't mention that my lead pack when charging almost over is at about 186V, more than I'd have at 50 cells charging at 3.65V, about 183V. It's just that when running at low amp draw on a nearly full pack my voltage would be 155-160 I estimate, and that may be more than it actually is if I only charge to 90%.

My goal is range, not the drag strip, low amp draw. I can't fit boat load of small cells in the truck, already tried six ways from Sunday to do that, most I can fit are about 75 or so 120AH cells.
 

·
Registered
Joined
·
4,054 Posts
Frodus take a Prozac and stop being so paranoid! Are you ADD like me and didn't read it before you posted?:D He IS A CURTIS AUTHORIZED REPAIRMAN. Besides, warranty was gone a while back, it's almost 3 years old.
So he's authorized for repair... But I'm guessing not modification, not upgrade. Why wouldn't curtis up the voltage on their controllers if there was an upgrade to do it anyway. But if you're confident and can get some sort of guarantee it'l work, great. I'm only expressing concerns that might keep things from biting you in the ass like it did for Logisystems. I'm trying to save you trouble, not cause it.

Re the LVC change I feel is just another measure of safety among the other things I will do. I HAVE NO PLANS TO RUN A BMS, though I'm going to have some monitoring system with LVC ability if need be, I'm not going to have it automatically balance my pack as I'm not fond of things known to cause fires. DC voltages at more than a 12V are dangerous enough anyway.
I agree, changing the LVC on the controller is a MUST. Not running a BMS is ok as long as there is a monitoring device that'l tell you when one cell hits LVC or can cut out the charger when you hit HVC. Balancing is not something I'll argue about, to each their own. I'm running a full bms, but its up to you if you want to or not, but IMHO, you need to monitor. We see eye to eye on that.
 
1 - 6 of 6 Posts
Top