[onegreenev]

What batteries and what is the condition of the batteries? Miles, Type. Have you checked the capacity of the pack? You could have a battery or two that are failing and that could be triggering your low voltage drop out. Batteries are the first thing to check. Check the terminals and the voltages and then the capacity and how they react under heavy load. Likely dead or dying cells. You can have a normal voltage under no load but a big drop under load. Cells sound more likely the trouble. Update us on what you find. Details will help others here diagnose your troubles.

 

[Ron Sand]

What batteries and what is the condition of the batteries? Miles, Type. Have you checked the capacity of the pack? You could have a battery or two that are failing and that could be triggering your low voltage drop out. Batteries are the first thing to check. Check the terminals and the voltages and then the capacity and how they react under heavy load. Likely dead or dying cells. You can have a normal voltage under no load but a big drop under load. Cells sound more likely the trouble. Update us on what you find. Details will help others here diagnose your troubles.

Just a f/u. After onegreenev's generous input, I tested all 12 batteries in my main pack. One as it turns out was bad. I replaced it and now the truck initiates as it should and drives normally. It charges to 155 VDC which is > 95% SOC, pretty good for batteries that are > 5 years old. Thanks for the support.

 

[remy_martian]

Am curious - is the one that died the one you were pulling 12V off of for all the lights, etc?

 

[Ron Sand]

Am curious - is the one that died the one you were pulling 12V off of for all the lights, etc?

Actually, this EV doesn't have an auxiliary 12 volt battery. Everything is run through a 144 VDC to 12 VDC converter drawing from the main pack. Pros and cons. I guess the problem I have been having is one of the cons!

 

[remy_martian]

Oh, ok. I thought maybe the 12V was getting directly peeled off the bottom of the stack.

You sure? Your DC to DC is still connected to the HV battery, even with contactors open?

 

[onegreenev]

Oh, ok. I thought maybe the 12V was getting directly peeled off the bottom of the stack.

You sure? Your DC to DC is still connected to the HV battery, even with contactors open?

Even if the DC/DC were still ON when you shut off the car it will pull equally across the whole 144 volt pack so not to unbalance a cell from the pack.

 

[remy_martian]

But that is not what I asked you. Note the paragraphs which separate context.

"Even if" is not an answer, it's a hypothetical with a known answer.

Again - is the 12V converter hot with the contactors open? It sounds like it is.

 

[onegreenev]

On my conversion the DC/DC was disconnected from the main battery pack via the circuit breaker. Once I flipped the circuit breaker the the DC/DC was hot. But it still pulled power from the entire pack and not any single battery. Since there was no single battery being with a drain on it the only option was a bad battery as I had suspected. I have had bad batteries and still showed full pack voltage or high enough to not realize a battery or cells were bad until I applied power and the performance was dismal or would shut off the main controller for lack of voltage because of severe voltage sag. As to your question specifically it could be ON but likely not. I did have one conversion that was ON when I shut off the vehicle but it kept the controller ON as well with very very very little draw on the main pack while resting for the evening. I did however prefer to just shut off the main circuit breaker ( not under load ) so to shut off every thing. I used my main circuit breaker like a light switch. On means it is on. It would allow me to also turn on my pre-charge for my controller. You don't want to leave items on if you plan on letting your electric vehicle sit for any length of time. My assessment was correct and I am glad they posted a follow up. It helps others that may run across this issue in the future.

 

[Ron Sand]

OK you guys. My system is set up so that the DC to DC converter is drawing from the pre side of the contactor, so the contactor does not need to be closed for the DC to DC to energized with 144 VDC. HOWEVER, I have a secondary switch in the cab that is used to close the circuit to the converter. To turn the vehicle on, this switch is turned on first, followed by the ignition switch. Thus all of the 12 volt devices in the car have voltage at the time the vehicle’s ignition is activated.