2005 E4 with lithium 22s battery, no 12v

My car’s 12v system has been intermittent for the last 2 months. I have been working with the guys that provided the lithium batteries (Dave and Bryon) We went through all the cables, connectors, fuses etc. I did change the ignition switch and thought we had solved the problem but no luck. The car used to turn on with a full display and asking the car to provide 12v the display would go dark. The display used to show the battery was plugged in and charging but that is also gone. When I plug it in I can here it pull power to charge, so the battery is charging, I think.

Does the DC converters go bad, how do I check it to see if I need to replace it. Are they repairable?

DC/DC converters go bad all the time - I am not aware of them being repairable.

Assuming it is one of the surepower units. I always had the impression they were fairly robust. Some of the real early ones had a little round fuse in one end and sometimes water gets in there and corrodes things up.
Also check the 12 pin plug going direct into the Converter.

Does the car run at all (without the display)?
When the car is plugged in to charge does it at least display the little yellow plug Icon on the dash?

Check Fuse13. This is the feed for the DC Converter. It will be one of those white ceramic fuses so you will need to check it with a meter instead of visually.

The display does not run at all. The alarm still sounds when the E-brake is released.
The Yellow Plug icon used to show but not any more.

Fuse 13 is good.

The converter fuse is good.

When I plugged the 12 pin plug back in after checking the fuse I felt one wire go in a little bit. The Yellow plug icon showed up. I unplugged the car and when I turned it on the display dimly lit up and turned off. Now it is completely dark and plugging in to charge the icon does not show, and the converter fuse is good

Try this.
Switch off battery at the Flippy breaker on the bottom of the fuse panel.
Wait 60 seconds. Flip breaker back on and try KeyON again while watching dash display. Does it light up for a moment? (Y/N?)

Also note- Do any 12v Accessories work? (headlights, Brake lights, horn, wiper)

When charger is plugged in to charge, What does the display on the Charger show? (Not the Dash Display). Is the car charging?

You seemed to have some sort of response with the Converter plug. Go back and see if you can duplicate that same result.

Still not working, removed 12 pin connector, repeated, nothing happens, tried beaker off 30 seconds, nothing happened. Nothing works except ebake warning.
The charger has is blinking red 6 times, and yellow light is constant.

Also the converter fuse spring does look rusty, I had sprayed it with contact cleaner, not sure what I could try to cleN it with with the hole being so small

Try rolling up a patch of 220 sandpaper and spinning it around in there. Let it expand a bit to the diameter of the holder.

Alt 1 - Maybe wrap 220 paper around a q-tip for some springy support
Alt 2 - Instead of Q-tip, maybe raid your kid’s candy haul next week and look for a properly sized sucker stick. Grab a couple of sizes(favorite flavor). Tell him/her it’s to fix the fun car. Fasten the end of the paper onto the stick with some blue tape and roll it up.

six flashes on the charger is an internal fault -

Are you sure your batteries are not dead?

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I am slightly conflicted tho.

Here is where I was going with my odd suggestions…
Since the handbrake uses the 12v (unswitched) to trigger the twin cube relays, this means there is at least 12v on one of the outputs of the DC Converter.

The dim display(and then going out) is hinting there might be a short on the switched leg of the output. This overloads the output and it shuts itself down to avoid damage. This is usually a really odd flashing and weird clicking as it resets and shorts out again. This is why I had you go through the power down, wait and power back up check. It usually cools off the converter and it will cycle again.

I’m feeling more like this could be the inout fuse heating up it’s dirty connection and losing contact. If you need more tension on the little spring, you might try a little wad of tinfoil once the holder is as clean as you can get it.

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When the display did work the last time maybe two weeks ago the battery showed fully charged at 85.4 Volts, I am guessing it has not discharged in that time frame. I am concerned about the internal fault however.

Why guess? Don’t you use the app?

Internal fault?

The app shows 88.6v, fully charged, I have a small display, I forget about the app in my old age.

I cleaned the converter contacts. The spring seems good. After turning ignition switch on the display showed up and immediately shut down. I tried to repeat it by removing the converter fuse etc but it didn’t work.

The charger now shows the yellow and the red light blinks 2 times

The charger now shows the yellow and the red light blinks 2 times

If the battery is full, sometimes the charger will not start and throw an error. it depends on what lithium profile it is running.

Hopefully you have a handheld meter. Time to start probing.

I would rather have you look for the battery itself. The app, and the little accessory display will still show a voltage(in this case 88.6) but you need to look directly for output FET status. If it is shutting down for some reason, the car would lose power any it would be tough to see.

If this is a DC Converter issue then we should look for it. One thing you noted was that the Brake Beep is still active. This might have been pre-sht down.
Verify that once the card goes dead, that the beep still is active?

Then (with a meter) check for 12v on the fuse block. constant hot, and Switchd(keyed).