Twice now, my Think’s master solenoid has disengaged while driving. It happened when coasting to a stop both times, and then the accelerator pedal was dead until I turned the car off, waited 5 or 10 seconds and then turned the car back on. After turning the car back on, as soon as I push the accelerator again the solenoid clicks in place and I am back on my way for the rest of my drive.
My car is working great otherwise, all I have done is replace the gel batteries with two 72v lithium batteries from big battery running in parallel, I’m using a separate charger from big battery, not the original charger.
The first time I thought it was a heat issue, but it really only took 5-10 seconds of leaving the car off before I could turn it back on and it would work and then I drove full speed for another mile or so. So it’s not like it had to cool off for a while or something.
The second time, the car was parked while we grabbed our dinner to go, and after we got back in the car and as I slowly moved through the parking lot it did it again, so I wasn’t even driving full speed at all before it happened the second time.
The solenoid looks good, the cables look good, and while I’m happy to spend the money to replace the solenoid, I just wanted to see if anyone knew whether that was really the issue or if I should think of other things first.
The BMS is built into the batteries, supposedly. The voltage looks pretty stable on my meter, I’m using one of those renology battery meters with a shunt on the negative battery circuit. I didn’t have the meter the first time it happened though.
I’m running these batteries from about 82 to 74v right now before I charge them. I imagine it could dip lower at times without the meter picking it up, I think I have the alarm set for 70v where the meter will beep at me but I don’t know how fast it samples.
Since you offer no other info on what you did to your car should I assume you gutted out the original THINK control system? In which case some of the following questions may not apply…
What happens to the car display when the car stops. Does it go dark?
Are there any codes thrown?
Other systems? (lights, horn, turn signals)
Clues, man! We need more clues!!!
It could be the DC Converter shutting down. What are the specs on that? Your low speed shut down could either be agitating a loose connection via a bump or maybe a short in the brake lights.
Running 2) 72v batteries could produce unpredictable results. This means(hopefully) they have individual BMS units tucked inside. Without knowing more about these we can only guess. Can you get access(Btooth app?) for monitoring purposes? Being parallel, a problem with one may be totally unnoticed as the other would still be powering the car.
You didn’t say that you were able to check the output of the batteries. IIRC these have a V display on each battery. Next time it stops a quick glance will tell you if the BMS in one of the batteries is having an issue and shutting things down.
I haven’t modified the car other than adding the batteries and the renology meter. Each battery has its own BMS. The Think display didn’t change at all, no wrench or any different icon shows up on the display, just the mph and battery level (that I ignore now anyway since it will not be accurate anymore), but I will certainly pay extra close attention to it if it happens again.
The lights on the car stay on (I only happened to notice because it was getting dark).
I was going real slow through a parking lot with no speedbumps when this happened the second time but this was also one of my thoughts, triple checked to make sure all connections were covered and not able to touch anything or move.
First, check for codes. If it doesn’t have any, I would monitor battery pack voltage by putting a voltmeter on the positive and negative pack cables. If the voltage is good when this happens, I would put a voltmeter on the contactor signal wires OG/VT and BK/GN to see if the contactor is being commanded off. If you have good voltage and ground when this happens replace the contactor. If you need a shop manual send me your email address.
Since Thinks are not exactly my expertise, I am only speculating here…
I believe anything that upsets a drive system enough to command the MC to open will also generate a code. Even if a wire falls off the MC and it loses power, the controller will toss out a “Hey we should be moving/consuming power but we are not” fault.
The only thing that will stop a car and not throw a code (besides going totally dark), would be if the controller thinks you want to stop/not go.
ie - lack of footpedal input.
Maybe this is a footpedal going bad? Not necessarily the up switch(which will generate a code), but the Pot side of it.
My car does exactly the same thing a couple times a year. Turning the key on and off a few times bring it back to normal. Nothing to do with batteries…the car just gets stupid for a bit.
If not battery/connection related, and no error code. I would lean toward a semi-normal condition. Such as fs1 throttle not holding. I believe MC will time out without continued signal from fs1.
To test it, use the @Erniea15 trick. Connect an external switch in parallel to fs1. Once driving turn it on.
A second but similar test. Connect an “always on” wire to power the hot side of MC coil.
Do the THINKs do much for regen? I have a problem now when a rip out of my house with a full charge and downhill, when I’m stopping, I regen and push power into my pack that the BMS faults. I have to come to a stop and recycle the key. I’m running a SEVCON controller, AC motor, and aggressive regen though. Not sure if the THINKs regen at all.
Doing a quick pass of the threat, it sounds like the BMS is faulting → causing the controller to fault - > causing the solenoid to pull in. Key off give the BMS time to reset, Key on, everything is happy.
As @inwo mentioned… I have a manual FS1 switch wired in my car now. Haven’t used it in forever but it solved some throttle faults i was getting. I was able to get a DCF with work with my dual throttle setup.
That all said, I’ve been wanting to convert that manual FS1 switch into a regen off/on switch but haven’t gotten around to it.
Do you have an option to connect to the BMS and look at the logs?
What is the best way to check for codes? I am happy to read up on this myself if you can direct me where to look. My assumption is that you were referring to an ■■■■■ light on the think display or something.
The BMS’ on these big battery.com batteries has no exposed interface unfortunately, so can’t look into those as far as I know. I’ll ask the company the next time I talk to them though.
Regen on a full battery is another cool idea. My battery was nowhere near full at the time though. That’s said, my renology meter reads a few hundred watts of charge going to battery when coasting down a hill, so it seems to provide some braking, just nothing that would bring me to a stop quickly.
I had similar drivability with stock batteries and it turned out to be a bad solenoid contactor. Unfortunately the are fairly expensive and may or may not be the issue in your case. The solenoid contactor does have some logic built in it that could be faulty causing false opens when driving. As designed the solenoid itself opens when you have stopped the car for a length of time with the key on. After stopping a while when you press on the accelerator the click you hear is the contactor pulling back in allowing the battery back (+72Volts) to connect to the motor controller.
Do you have info(make/model) on what solenoid/contactor you had to replace?
As much as I like a new guy willing to step in and offer information, I think you have it not quite right in this case. I thought I’d try and clear this up and not confuse future readers.
I haven’t seen a Main Contactor with it’s own logic. The normal kick IN/OUT action is controlled by the Motor controller and the Contactor is just a big heavy duty relay. The trick is that the trigger coil needs to be continuous rated for ~72v and the switched high current side needs to rated for high voltage and high amps.