DC-DC Converter always on

[yannd]

Hi, I'm looking for a simple way to keep the DC-DC Converter always on to keep a secondary 12V Battery Bank always charged (I already have a DC-DC 12V 20A Charger installed) I don't want to drain the 12V onboard battery and for now the only way to keep the converter ON is on Ready Mode or while charging, but I want it to stay ON as well when simply parked (without the Ready Mode draining extra power)

Any clues on how to do it ? Can I "cheat" the charging mode so the car thinks it's plugged in or is the only way to physically modify the DC-DC converter ? I already have a Canbus Telematics box connected, maybe by modifying some CAN signals ?

Basically, the goal is to use the 400V pack as a an extra stationary battery bank for my 12V Inverter solar charging system (which already has 4kWh). I know the max transfer power will be around 600-800W, which is enough to keep the 4kWh topped when needed.

Any ideas are welcome,

Thanks,

 

[veimi]

I don't want to drain the 12V onboard battery and for now the only way to keep the converter ON is on Ready Mode or while charging,

I was interested in your comment that the 12V battery is being charged when the main battery is being charged,

A few years ago my car wouldn't start because of a discharged 12V battery. If my memory serves me correctly, charging the car did not fix the problem.

I was wondering how you determined that the 12V battery is being charged when the main battery is being charged.

 

[PV1]

Watch the dome lights when you plug the car in. After a couple seconds, you should see them get slightly brighter.

As for the original question, due to the car’s design, I doubt there would be much energy savings if you can get just the DC-DC powered up without full READY.

 

[Don]

I was wondering how you determined that the 12V battery is being charged when the main battery is being charged.

Because page 1-17 of the owners manual says so -
NOTE
● The 12V starter battery will be automatically charged during charging and also while the ready indicator is illuminated. Refer
to “Ready indicator” on page 3-72.

Don

 

[yannd]

As for the original question, due to the car’s design, I doubt there would be much energy savings if you can get just the DC-DC powered up without full READY.

The goal is for the secondary 12v battery bank to always charge when I'm not driving or charging it.

 

[kiev]

Does your car have DCQC Chademo port? If so then you could access the 360V pack thru that port and use it with a DCDC converter to create a 12V supply for charging a secondary 12V bank.

i explained how to do this in a post about the Chademo port with pictures and description of how to "open" the port to expose HV on the terminals.

 

[veimi]

I was wondering how you determined that the 12V battery is being charged when the main battery is being charged.

Because page 1-17 of the owners manual says so -
NOTE
● The 12V starter battery will be automatically charged during charging and also while the ready indicator is illuminated. Refer
to “Ready indicator” on page 3-72.

Don

After some time of non use, my 12V battery recently died and the car wouldn"t start. I charged it with a battery charger.

I'm fairly certain that recharging the car that had a dead 12V battery did not recharge my discharged 12V battery on a previous occasion.

It's something I will have to retest should it ever happen again.

Others on this forum have also had their cars not start because of a bad or discharged 12V battery and to my knowledge there has never been any report of success or a suggestion to fix the problem by simply charging the car.

 

[yannd]

I was wondering how you determined that the 12V battery is being charged when the main battery is being charged.

Because page 1-17 of the owners manual says so -
NOTE
● The 12V starter battery will be automatically charged during charging and also while the ready indicator is illuminated. Refer
to “Ready indicator” on page 3-72.

Don

After some time of non use, my 12V battery recently died and i charged it with a battery charger.

I'm fairly certain that recharging the car that had a dead 12V battery did not recharge my discharged 12V battery on a previous occasion.

It's something I will have to retest should it ever happen again.

Others on this forum have also had their cars not start because of a bad 12V battery and to my knowledge there has never been any report of success or a suggestion to fix the problem by simply charging the car.

The charging will work only if the 12v battery is still around 11v. Below that it won't be able to start the 400v dc-dc contactor or charging process. So it works to keep the 12v charged, but not to "repair" a dead 12v battery.

 

[kiev]

A weak, old or worn out 12V aux can be so degraded that it no longer charges anymore by any method, either by the car when charging the HV, or externally using a lead battery charger. When unloaded it may even read 12V with a DMM, but that is a false artifact.

A good strong 12V aux is needed in order to charge the pack because of all the ECUs, relays and contactors that must first be actuated by the 12V aux before the HV charging session will begin. Maybe a weak aux will have just enough juice left to get the session started, but it is so degraded itself that it doesn't accept any significant charge from the DCDC during the session.

We have seen this many times--the pages of this forum contain numerous accounts of issues due to a weak, old or worn out 12V Auxillary Battery.

Cheers,

 

[veimi]

I was wondering how you determined that the 12V battery is being charged when the main battery is being charged.

Because page 1-17 of the owners manual says so -

The charging will work only if the 12v battery is still around 11v. Below that it won't be able to start the 400v dc-dc contactor or charging process. So it works to keep the 12v charged, but not to "repair" a dead 12v battery.

Thank you!

I feel better that it wasn't just my imagination now that it has been confirmed that charging the car does not always recharge the 12V battery.

 

[Don]

I feel better that it wasn't just my imagination now that it has been confirmed that charging the car does not always recharge the 12V battery.

If your 12 volt battery is in good shape, then it's always charged while the car is recharging. If the battery shows less than about 11 volts, many computerized chargers won't recognize it as a 12 volt battery and will fail to recharge it - I keep an old $30 6 amp analog battery charger on my shelf just for that purpose . . . . it will recharge any battery no matter how low the voltage is

One thing proven here many times over is . . . . when your 12 volt battery is near the end of it's useful life, an iMiEV will exhibit all sorts of very unusual problems. The factory battery at about 7 years of age has been the culprit more times than I can count. If you have to jump start your iMiEV for any reason, problems are just around the corner and you should probably make a trip to the store for a new battery if you do successfully get it running.

I've never had those problems, but I've never attempted to go much beyond 5 years or so before I preemptively changed out my 12 volt batteries in all 3 cars. I don't care for weird surprises . . . . and more than that, I hate to walk!

Don

 

[veimi]

I feel better that it wasn't just my imagination now that it has been confirmed that charging the car does not always recharge the 12V battery.

If your 12 volt battery is in good shape, then it's always charged while the car is recharging.

Don

What do you do when you come out a few days after removing your dashcam and discover that when being removed the power wire to the camera accidentally had turned on your inside lights by brushing against the switch? Reading page 1-17 of the owner's manual would suggest that all one had to do was charge the car.

 

[Don]

If you've left lights connected to your battery 'for a few days' then it's deader than dead and you're probably looking at buying a new battery, especially if it was a few years old to begin with. You could try recharging it with a Pulse Repair Technology battery charger and you might get it back up to 13 volts, but the damage has been done and it's very likely to give you more problems in the near future. Best case scenario, you destroyed most all of it's useful life by leaving it connected to a short (an unlit light bulb is effectively a short) for several days

If it was me, I'd bite the bullet and replace the battery - Lesson learned

Don

 

[yannd]

Anybody with more information on the original post on how to keep the DC-DC Converter ON without recharging the car or having the key turned ? Looking to have a constant charging of a secondary 12V Battery Bank (Connected with a controlled DC-DC Charger) Thanks !

 

[yannd]

Any way to reactivate this thread ?
Thanks

 

[PV1]

I still have my doubts. For the DC-DC converter to work, high voltage has to be engaged for the whole car and the DC-DC itself needs an activation command from the EV-ECU. The car would physically be READY if the converter was active.

What would do the trick is figuring out a remote start system that can sense a low 12 volt battery and automatically “start” the car for 15 minutes.

 

[yannd]

Could the remote transmitter be used to send a signal ? Maybe by modifying the charging timer command ?

Basically wondering if it would be easier to hack the software part or the hardware part...

For now plugging directly to the 400v pack with a second 12v DC-DC converter seems the fastest and easiest way, but also more dangerous and prone to other error codes if not done right by the mechanic (similar to the OBC bypass modification)

I'm sure other users would like to have an always live 12V from the traction pack with 600-800w...

 

[PV1]

The stock MiEV remote that handles charge timers and pre-conditioning won’t work. It can check the battery charge at any time when it’s near the car, but it requires the car being plugged in before it can activate the high voltage system. Maybe there’s a way to sniff the CANbus and see what command it sends to do that, and maybe sending that same command over OBDII and see what the car does. This is above my knowledge, though.

 

[kiev]

i opened one up and traced the harness, and it just may be possible to command the DCDC as a separate unit assuming you have a HV source. See the wiring and connector pinout in this thread,
http://myimiev.com/forum/viewtopic.php?f=23&t=4079&p=41781#p41781

There is no CAN buss, just a couple of discretes from the EV-ECU, don't know if they are sources or sinks yet.

[edit] Started a separate DCDC converter thread with pictures, schematics, etc
http://myimiev.com/forum/viewtopic.php?f=23&t=4737