Possbile to Damage DC-DC Converter?

[LeftieBiker]

I've had my car since June of 2013, and have had no trouble at all with the 12 v battery. I even left the car sit for 2 weeks once. I say if it's not broke, don't fix it. If your 12v battery ever dies, worry about the battery tender then. Most likely it won't.

I think a better approach would be to not worry about using a maintainer *unless* you regularly have to leave the car plugged in for hours after charging finishes, or take lots of short trips while using accessories like the wheel and seat heaters, rear defroster, wipers, etc. Because the rules about where and when you may get stranded were written by a guy named Murphy...

 

[knightmb]

i've been searching thru the forum trying to answer these questions and wanted to let the group weigh in on this topic. i know the question of leaving the leaf in storage mode has been discussed extensively but i'm not sure the DC-DC Converter has.

in this thread http://www.mynissanleaf.com/viewtopic.php?f=31&t=12442&hilit=storage&start=20 Ingineer suggests the safety of connecting a trickle charger to the 12v battery while the battery is still connected to the DC-DC Converter. but in my readings i vaguely recall someone (don't remember who) claiming that the DC-DC Converter could be damaged by being exposed to a trickle charger and that the 12v battery should always be disconnected at the negative post before being connected to a trickle charger.

this also leads to the idea that if it's safe to connect a trickle charger connected to the 12v battery while its connected, then perhaps, for ultra-cold weather storage it would be possible to leave the EVSE plugged in to warm the Li-on battery without discharging the 12v battery.

any thoughts?

I don't see any reason why a trickle charger would damage anything. They automatically shutdown at 14 volts come back at 13 volts and any back current would simply turn into heat if the DC-DC converter was having issues. The return load heat generated would be far less than when the by the DC-DC is in use. When things go bad when dealing with electricity, heat is usually the killer of electronics.

If you have an old-school trickle charger that just floats 14 volts, then with any DC system, it is easy to sync voltages and no current will float since both sides using use the same voltage which results in a net 0 of power flow. You also have to take into account the battery itself is a consumer of power and keeps the bus voltage of the whole thing probably down to only 12 volts.

 

[jthompson8]

this is complete nonsense, charging 12v lead acid battery of a Nissan leaf while connected to the car or even while the ignition is on and the DC-DC converter is also charging it is perfectly safe (assuming your charger is designed to charge a 12v lead acid battery and the charger in question is not broken or faulty in any way)

reverse bias current does not damage a DC-DC or any other current for that matter, all DC-DC converter have a lo drop schottkey rectifier diode on there output that serves as reverse polarity protection, but even that dose not relay matter as long as you actually connect the charger the right way around.

voltage is what is likely to damage a DC-DC converter not current, any voltage less than zero like connecting the charger the wrong way round, or any voltage over 14.5v as in outside the working range of the battery because the DC-DC converter will have been designed to work at 14.5v and is likely to have components rated to not much higher than 14.5v because the engineer that designed it new the voltage would never exceed 14.5v so why try to account for a condition that will not occur within its warranty scope.

if you were to connect a 24v charger that would likely damage the DC-DC converter, but then it would also damage the battery as well so...

i have given the DC-DC converter on my 13 plate leaf quite some stick for many years now since I built a boost converter module for my leaf that powers my house off the 12v battery on my leaf leaving the DC-DC converter flat out trying to replenish the battery that continuously has a 1000 watt drain hours at a time on days i dont have much solar power,

i can honestly say that while there are numerous things on a Nissan leaf that were not thought through so well at design time, there DC-DC converter works well enough

 

[jthompson8]

The answer is - Totally easy to damage the DC to DC converter

You put more current than the forward bias on the DC to DC converter and toast!

Magic smoke and good luck on the getting a warranty repair.

this is complete nonsense, charging 12v lead acid battery of a Nissan leaf while connected to the car or even while the ignition is on and the DC-DC converter is also charging it is perfectly safe (assuming your charger is designed to charge a 12v lead acid battery and the charger in question is not broken or faulty in any way)

reverse bias current does not damage a DC-DC or any other current for that matter, all DC-DC converter have a lo drop schottkey rectifier diode on there output that serves as reverse polarity protection, but even that dose not relay matter as long as you actually connect the charger the right way around.

voltage is what is likely to damage a DC-DC converter not current, any voltage less than zero like connecting the charger the wrong way round, or any voltage over 14.5v as in outside the working range of the battery because the DC-DC converter will have been designed to work at 14.5v and is likely to have components rated to not much higher than 14.5v because the engineer that designed it new the voltage would never exceed 14.5v so why try to account for a condition that will not occur within its warranty scope.

if you were to connect a 24v charger that would likely damage the DC-DC converter, but then it would also damage the battery as well so...

i have given the DC-DC converter on my 13 plate leaf quite some stick for many years now since I built a boost converter module for my leaf that powers my house off the 12v battery on my leaf leaving the DC-DC converter flat out trying to replenish the battery that continuously has a 1000 watt drain hours at a time on days i dont have much solar power,

i can honestly say that while there are numerous things on a Nissan leaf that were not thought through so well at design time, there DC-DC converter works well enough