Oh! I just realized that in my earlier posts where I posted a screenshot about "Slave 5" historic "cell voltage connection fault", the slaves are numbered 1-16. While the Filt_Analog displays of CommTool have 0-15 numbering. So the earlier "slave 5" is the same "slave index 4" that now shows a cell at 2V.

And actually if you look at Module_Volt_Filt 43.3V, it's the same as in slave_index 5.. If I sum all the Cell_Volt_Filt_n together, I get only 41.53V. So 2V must be measurement error.

What I didn't tell you before, I actually swapped two battery module places in the pack. RLECs are in the same place as before, but RLEC 4 is now connected to different battery module as before. So I guess it's now confirmed this is a RLEC fault, since fault stayed at the same RLEC even when it's actually a different battery module.

This is a project that just keeps giving and giving. 

Yesterday on a test drive, the airbag light lit up. Doh. Think TechCentre shows it's an open circuit in driver's airbag. Light went away briefly, but came back and now is permanently on.

Today, I removed the power steering from the spare Think, and installed it into this one. This was actually quite easy, only perhaps one hour total removing and reinstalling to a different car.

However, the power steering still does not work. I guess there is something wrong in the car, which is why previous owner decided to install the Volvo pump which didn't really work too well either.

Looking at the power steering schematic:



There are two wires going to the steering wheel, through the clock spring... Isn't it suspicious now that the airbag has failed also? maybe the entire clock spring is bust? But obviously I have a spare in the white car..

But now to the "keeps on giving" part.

While testing the non-working power steering, car decided suddenly to pop up all possible warning lights and refuse to go further. Had to be pushed back to the garage. Now to my horror it seems there's one cell at 2V in the pack:



So, back to the drawing board... Dropping the pack again. 

Thanks! I will take a look..

Hi,

my third Think has a mysterious heater fault. Car works fine if heater is off. Also with heater on, it works maybe 30 minutes or so, and the heater is working fine during that time.

However then the car stops with isolation fault. If I remove the heater cable and connect dummy plug to the PCU, the car drives again. If I measure heater wire to ground with a "megger" (500V insulation tester) I see only 0.5-0.8 Mohm so it is leaking.

However after waiting perhaps 15 minutes and measuring again, resistance is now >550Mohm which is the maximum the meter shows.. And indeed, you can replug the heater to PCU and it works again.

I assume there must be some kind of coolant leak inside? Do you think it's fixable?

I'm now pretty sure the drive battery is fine. I think the RLEC error was caused by a combination of:

- Bad 12V battery
- Volvo electric power steering pump that seems to take huge amount of power

RLECs and MLEC are powered by 12V and perhaps can fault if the voltage drops too low?

I bought a new battery, and removed the Volvo power steering. I'm a Finn writing in Norwegian car forum. Perhaps we can all agree that Volvo parts have no place in these cars. 

I have a spare power steering pump in the white Think. I might transfer it over. It's not really too bad without power steering, but I think it might be an issue in the annual inspection because power steering is mentioned in car documents.. So it might not be legal to remove it.

Oh, while I had the main battery open, I did a few obvious improvements I have learned from your forum. I installed a 150W precharge resistor.

Also my wife made a long but thin fabric tube, something like 50cm long but only perhaps 3cm in diameter. I filled it with cat litter, and stuffed it into the empty center channel. It is possible to insert it with only this one module removed. I forgot to take a picture of the actual tube, sorry.

Sitat fra: Orbit på fre 10. apr 2026, kl. 13:11I think it would be better to install a contactor/relay close to the battery, and only run a low amperage control line to a convenient switch positon. This avoids running thick cables plus a high amperage fuse (which also implies that a short on that cabling still can do signficant damage before the fuse blows).

In my other car projects, I have often placed the battery main switch on the minus side. Then there is really no risk of short circuit, as short circuit would simply be the same as turning the switch on. And you can find the actual chassis ground point near to the switch, so the wires are reasonably short! Plus side would have to go twice the length to get back to the battery.

Speaking of the 12V battery, this new Think had very different looking battery mount to my earlier Thinks. This is a two piece design. You just open a few M6 bolts and the bottom drops out, together with the battery. There is enough loose on the cables so you can then remove them quite easily. Much better than the older(?) one piece mount..

Sitat fra: worry på fre 10. apr 2026, kl. 09:35The starting amps is more than enough to start, but I experienced empty battery after about 5-7 days. I think I wrote something about it on the thread for my red Think project. Measured the drain amps, which seemed to be normal.

Ah. Well this sort of matches my lead acid experience? Fully charged 50Ah battery is deep discharged beyond recovery in about two months.. So there must be some drain.

I figured that even if Lifepo4 would drain, it wouldn't ruin it because the BMS cuts the battery when it gets too low voltage. But perhaps it's better to invest in main switch, so car can be completely shut down easily.

Something like this from biltema:
https://www.biltema.fi/autoilu---mp/sahkojarjestelma/virrankatkaisijat/paavirtakytkin-100-a-2000016429

Oh, another thought occurred. Does PCU supply 12V when external power (230VAC) is available and charging starts? What I mean, if the integrated BMS inside 12V lithium battery disconnects the battery for protection (too cold or low voltage etc), is it possible to wake the car up by connecting charging cable?

Hi,

I have seen some of you are using lithium batteries as 12V battery. What are your long term opinions?

Think always seems to drain the 12V battery if not used for a few months. It doesn't help that the battery is in so impossible location that you can't easily remove the cable so it wouldn't drain. However it should be possible to add a "main switch" with extended wires, perhaps to the minus terminal..

Anyway, I now have two cars both with dead batteries. Cheapest suitable lead acid battery is about 50€ in Biltema. (about 550 NOK)

Then there is for example this lithium battery for 65€ :
https://www.motonet.fi/tuote/fulbat-litium-akku-12-v-387-wh-fltx4l5l7l-fltz5s6s7s?product=90-02092

but some obvious questions,

Only 3Ah! Is it enough? The stock lead acid is 45Ah or something like that. But I guess just starting the car doesn't really use that much. However you must perhaps avoid listening to radio or leaving lights on unless car is fully awake.

Does it work in winter? It can't be charged below 0C, but then again the main battery has the same limitation and seems to charge just fine.

I sprayed soap water around and again tried with compressed air. Only slight leaks I could find are around the sharp corners near the MLEC opening, and also slightly through under the HV connector. So I guess this is pretty much as airtight as Think battery can possibly be.

I opened it. Very dry looking inside. The Enerdel "warranty sticker" was broken and I can see some missing plastic tabs that hold the plastic RLEC covers.. So this is not the first time this has been opened.



I removed the RLEC ribbon cable from the MLEC, and attached my own Raspberry Pi debug device in place. I figured I leave it running for a few days or something like that, to see if faults appear again in RLEC 5..

Battery looks like it's in very good shape. It only has 56mV imbalance, between highest and lowest cell voltage, at about 3.7V per cell! And it has been sitting over the winter, charged previously in July 2025..

Well, I was interested in trying out my new lift, to see how much faster it is to drop a Think pack when compared to the old "jackstands on the floor" method..



35 minutes from car standing on wheels to battery on the floor. I first lifted the car to very high, removed half of the battery bolts, and then even pre-loosened the remaining ones. Then lower the car so it is touching the three stacked pallets, and remove rest of the bolts. Lift slightly to get clearance to remove the battery connectors, lift a bit more to be able remove the ground wire.. And that's it. Re-installing should go also very fast especially if I don't need to move the car or the battery from where they are.

Then I thought I'd look for possible leaks before disassembly, as a starting point. I made a tool with M5 thread which can be inserted to the rear of the pack after removing one of the screws..





Turns out, it the battery doesn't seem to hold any kind of pressure, it leaks from every seam. Has anyone pressure tested these before? Then again, there are no pressure relief valves or anything, perhaps it's SUPPOSED to leak from everywhere or it would turn in to ball shape when the air inside expands when heating?

Tesla batteries are pressure tested at under 0.2psi (the umbrella valves will open at higher pressure). Battery pressure is supposed to drop at maximum of 0.01psi per minute. I perhaps need to find a more accurate pressure gauge as the tire pressure scale is a bit too high. But still my initial feeling was that the battery does not hold any kind of pressure for more than a few seconds.

Maybe the ventilation could be improved somehow. Obviously first make it really airtight, perhaps by adding some sealant in addition to the gasket? But should there be "Tesla style" valves added or something?

This battery case looks really good from outside, no obvious places of rust or anything.

Thanks worry.

I decided to launch commtool again before dismantling anything.

Once again I checked the cell voltages and they look fine. All 16*12 cells shown with the Analog1-8.MSF and Analog9-16.MSF. Then I run the Analog.MSF. Here I spotted something.



While "current" slave faults were all zero, there's a 08 in Slv5_Hist_Codes! This would match the above "String A" fault as I believe RLECs 1-8 are String A and RLECs 9-16 are String B.

The fault codes probably match this field that is in the RLEC_programmers_guide.pdf:

Du kan ikke vise dette vedlegget.

08 would be "CV connection fault", which is actually very well described a bit later:

"This fault indicates to the MLEC that high impedance connections have been
detected in the RLEC cell voltage measurement circuit and as a result, the RLEC
cell voltage measurements may be invalid. This is considered a critical fault and
the MLEC responds by opening the main contactors."

This again would match the historic fault I mentioned in earlier message:
Bit 6   46   CV_CONNECTION_FLT   Cell voltage connection fault

Interesting that the condition is considered so severe that even if RLEC no longer reports fault, MLEC still doesn't let the car run. But after clicking "Clear all Malf codes" in CommTool it seems to work for several days even.

But I have to say I kind of like this part of Think repair. I haven't done anything except a few taps on my laptop, and I already have pinpointed the fault to a single RLEC or that same battery module..

Ah found another document (Vehicle_CAN_Bus_Guide_V3.0.docx) that has all the bits defined for Byte 5:

Bit 6   46   CV_CONNECTION_FLT   Cell voltage connection fault
Bit 7   47   EXTREME_UNDER_VOLT_FLT   Extreme cell undervoltage fault

For completeness, I decoded 722 (latched fault) and 723 (historic fault) as well..

Byte 1 bit 9:
EXT_ISO_FLT    External (or internal) isolation fault

Byte 4 bit 7:
IN_12V_UNDER_VOLT_FLT   12V input under voltage fault

Byte 4 bit 3:
CONT2_STUCK_OPEN_FLT    Contactor 2 detected stuck open

Byte 4 bit 2:
CONT1_STUCK_OPEN_FLT    Contactor 1 detected stuck open

Byte 5 upper bits are marked unused, no idea what that is (the D0 bytes)

contactor stuck open is probably caused by the failing 12V, if it doesn't have enough power to close the contactor?

Isolation fault is either the heater or AC. I didn't mention it before, but actually the car died a bit earlier during the "drive around the house" test run. It was isolation fault. I removed the orange PCU plugs and replaced with dummies, and car started working again. I used megger to measure the heater/AC wires and only measure 0.6Mohm which is below the accepted 1M limit, so it must be that. I say "heater/AC" because for some reason someone has connected both PCU outputs in parallel, I can't separate the two.. It's perhaps "current sharing" to not blow the internal PCU fuses so easily? Both outputs are still providing voltage..

Ah, just found can 721 explanations in "THINK City Enerdel Battery Service Manual.pdf":

Byte 3 bit 3:
UNDER_VOLT_FLT_A  Cell under voltage fault string A

Byte 5 bit 4:
IN_12V_UV_WARNING  12V input under voltage warning

Sigh.. So it is probably some RLEC issue after all. Must be randomly reading false data somehow? As all the cell voltages are looking fine.

The fact that the 12V undervolt is showing here too means that I'm interpreting the bit order correctly..

Well. Luckily I just installed a two post lift in my garage so it's easy to drop the pack if needed.