Pulling battery disconnect / Disabling APS for month+ storage to eliminate vampire drain...

[wiztecy]

I've been taking the metro bus to work for about 8 months now so I haven't been putting the miles on my Roadster since I no longer need it for my daily driver. I now ride my electric skateboard to/from the bus metro which is about 5 or so miles away, then ride the bus 30+ miles over to the city where my work resides. Then skate a couple of mile, just for the fun carving part. Its the best way to commute, I now get 1.5 hours or more back to my daily life and the bus has WIFI so lots of learning potential for new ideas/hobbies/etc.

Anyways, I've been keeping my Roadster's SOC at about 50-65% and always put the battery as the #1 priority to extend its usable life. One thing about not driving the Roadster is that the vampire drain slowly consumes the charge, so I have to every 3 weeks to a month do a top off to bring the SOC where I like it. Also when I do take the Roadster out for a drive I do need to balance the pack to get the best performance and capacity if I require it. Temps are mild now, 40F at night and around 75 during the day so in all honesty there's no reason for the pump to kick on nor for the car to have to wake up for anything such as checks. So what I'm looking at doing is to disable the APS and shut the pack down at 60-65% SOC. Then when I need to use the Roadster say in a month or two, I can enable it and carry on with my normal charge and balancing process. This should keep me away from any vampire drain and since its not hot out, the battery should be fine not having the coolant circulated. It also doesn't get cold enough to warrant running the battery heater. This sounds like the best way to keep my Roadster due to the change in my work commute lifestyle.

 

[Habious]

Is there a difference in parasitic drain between inhibiting APS and pulling the service disconnect? (I know one is A LOT easier than the other)

 

[wiztecy]

That's a good point. I don't know what really gets shut down, stays alive when APS is disabled as well as where it's getting its power unless I guess there's some capacitor responsible for keeping some energy around for a lifeline. For the 1.5 I could disable APS and then back off the main ESS connector by the PEM instead of pulling the driver's rear wheel to get to the disconnect and compare the difference. The connectors self back and self set themselves in place with the twist of a collar. But not that I'm thinking about it I wouldn't want to expose any excess wear on the connecting points as we have seen the PEM fan connector has a limited lifecycle.

 

[supersnoop]

I think we need to better define "vampire" drain. Actual parasitic drain is cause by shorts or other unexpected faults that draw power. I had a problem with my BMW where the car would shut down into a deep sleep and the "comfort access" wouldn't work because something was drawing too much power from the battery. That's the type of thing that needs to be isolated and corrected.

But the main drain in a Roadster is the car's intentional monitoring of sensors and critical components. I wouldn't trust that the battery "should be" fine without the coolant pump running or the heater enabled. I can't see any good reason to disable all of the cars sensors when simply plugging it in and putting it in storage mode would keep it fully intact and healthy.

 

[Habious]

I think we need to better define "vampire" drain.

Not trying to turn this into a semantics argument, I swear.

My 10 minutes of armchair research came up with these two definitions -
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Parasitic load is a term used with regard...to electrical appliances, it represents the power consumed even when the appliance is shut off, that is standby power. - Source

Standby power, also called vampire power, vampire draw, phantom load, or leaking electricity refers to the way electric power consumed by electronic and electrical appliances while they are switched off (but are designed to draw some power) or in a standby mode. - Source
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But, I think we all know what we MEAN - the car drawing power "just because" while it's simply sitting there, key off, doors closed.

The Roadster draws considerably more power "just sitting there" compared to any ICE car...but it has a considerably larger battery than any ICE car!

I'm not sure if anyone (outside of Tesla) knows what is "normal"; I'm sure it depends on several conditions (including environmental ones).

I know the Roadster owner's manual specifically does NOT state how long you can safely leave the car unplugged (I'm sure this wasn't an oversight on their part).

I think @wiztecy is trying to weigh the potential for damage to the car by killing the power to the system (so no heat/cooling pumps running) compared to the very-real, very-costly, potential to brick the battery if the car is left alone, unplugged too long.

 

[markwj]

The main thing we're worried about here is the ESS (the big battery). I guess also the little 12V lead acid, to some extent.

Ever visited a Tesla service centre and seen those big crates containing ESS in storage? They are checked once a month or so, but in that disconnected state they are good for a year without having to be topped-up charged. No cooling. No heating. No realtime monitoring. Just hanging around the service centre storage room.

So, I would say go for it. Inhibit APS and check it every few weeks. Let us know how it works out.

 

[Habious]

...in that disconnected state they are good for a year without having to be topped-up charged. No cooling. No heating. No realtime monitoring. Just hanging around the service centre storage room.

So, I would say go for it. Inhibit APS and check it every few weeks.

But, my thought on this is "that disconnected state" that you refer to has the batteries "just hanging around" with NO load/drain on them.

If you watch the PEM cleaning video that @mgemmell posted (Link here), he shows when he Inhibits the APS and, while it shuts a lot down, it clearly doesn't shut EVERYTHING down (the VDS still has power and, presumably, one or more of the computers in the car.)

Is that just powered by the 12V aux battery? I honestly don't know. But, the car is clearly still not OFF (with NO power draw).

That's why I brought up the difference between the APS Inhibit and pulling the physical service disconnect.

It was my understanding that the 12V gets charged off the main battery as-needed.

If you inhibit APS (or pull the service disconnect), won't that eventually kill the 12V (which I know brings up its own mix of problems)? Of course, while the death of the 12V aux battery is NOT a $40K repair, it seems like it would cause frustrations when it comes time to revive the car and get it running again.

 

[GarrickS]

Hi, Roadster-newbie here, but what if you just put a battery tender on the 12v battery? Surely, it's the 12v battery powering these vampire systems and the traction battery is just charging the 12v battery.

 

[wiztecy]

No 12v battery for me on the 1.5 Also unsure what they power off of the 12v battery vs the ESS, if it was the 12v battery contributing to the drain then all you'd need to do is keep your 2.x on the tender like you said, howecer, the ESS will keep dropping in SOC anyways.

I don't have much of a drain to really worry about, its more of having the entire system sleep and preserve the SOC where I want it in terms of manageability when Roadster is sitting for a prolong time.

I disabled the APS last night, was at 109 std. miles when I did. That puts me a tad bit above 50% SOC.

 

[Habious]

No 12v battery for me on the 1.5

I disabled the APS last night, was at 109 std. miles when I did.

Hmm...that poses an interesting question (for me, at least). When you inhibited the APS, I assume the VDS stayed powered on (otherwise, how would you re-enable the APS).

So, if inhibiting the APS kills any draw from the big pack...and you have no 12V aux battery...what's powering the VDS?

 

[wiztecy]

That got me thinking to sometime back. They must be getting that power from the ESS, if you pull the ESS yes you can't fire up the VMS/VDS. Inhibiting the APS must allow some voltage to come across, nothing that could cause anyone harm.

 

[ML Auto]

In the 1.5 that power comes from a separate voltage converter run off the first two sheets in the ESS. There has been talk of the APS running off those two sheets, but the APS is connected to the entire sheet voltage. In the 2.x, it feeds from the entire pack voltage along with the APS.

For those wondering how long an ESS can sit unplugged and disconnected , I let a 2.0 sit with the APS off, ESS disconnect pulled and the small drivers side connector unplugged (VMS power) for over six months. Starting with a full standard charge, the lowest brick voltage after that time was still 3.92V. Which means several years before any worry of damaging the cells. On a 1.5 the first two sheets running the internal converter would discharge the fastest, but unplugging the VMS connector should eliminate most of that.