Gen 1 Vampire Drain (Possibly) Solved (or Hacked)

[shrink]

TLDR:
I hooked up a battery charger/maintainer to the 12V battery in my R1S and so far (3+ days) there has been no loss in SOC from the main battery pack.

I returned to the mainland on Friday (8/9/2024) and left my R1S garaged in Hawaii. It was set to charge to 70%, but dropped to 69% at some point as it usually does. Before leaving for the airport with the high voltage battery SOC of 69%, I reduced the charge limit to 50%, attached the battery charger above to the 12V battery, and set it to charge an AGM battery. Vehicle is plugged in to an L2 charging station (240 V @ 40 amps)

What typically happens is that I lose 1-2% per day until my set SOC limit of 50%. The vehicle will then charge a little bit per day but usually stops at 49% for some reason until I return.

Well, it's only been 3 days but the SOC has stayed at a steady 69%. It's early, but I think this is working.

Will continue to monitor and provide 1-week, 2-week, 3-week updates, etc. until I get back on island.

I'll also post more photos of how everything is connected.

If this does work, I think the next step is attaching a Kill-A-Watt to the battery charger to get a sense of how much it's actually charging up that 12V daily.

I know these are preliminary results so no one get too excited but it's certainly a promising start so far.

Only photo I took was the one below which is the reading after I first attached the leads:

1-week update (8/9/2024 to 8/16/2024):
1% loss from the high voltage battery
(69% to 68%)

2-week update 8/16/2024 to 8/23/2024
0% loss from the high voltage battery
SOC remains at 68%

Cumulative over 14 Days: 8/9/2024 to 8/23/2024
1% loss
69% to 68% SOC

Final Results:
8/9/2024 to 8/30/2024

3 weeks/21 days (and 510 hours to be most precise):

1% loss total
0% loss in the final 2 weeks

9/13/2024 Edit:
I have discovered that the draw from the 12V battery charger is about 0.3 kWh/day.

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[Dark-Fx]

I have the same experience if I leave my camper hooked up via the 7-pin. Camper solar charges the battery and offsets the HV drain.

I have yet to check which battery is being maintained and if it causes issues because only one is.

 

[mikehmb]

Awesome, thanks for sharing. Did you put a meter behind the battery tender to see what your draw looks like there?

The computers/etc run off the 12V, and the downconversion from the HV battery to 12V is not 100% efficient. Would be really interesting to see exactly how much is being asked of the 12V.

 

[aAlpine]

The computers/etc run off the 12V, and the downconversion from the HV battery to 12V is not 100% efficient. Would be really interesting to see exactly how much is being asked of the 12V.

IIRC in interviews regarding the Gen 2 design, Rivian admitted that the old design of the 12V battery charging system was such that a large number of systems had to be powered, which is the source of the waste. The Gen 2 design now has a dedicated subsystem.

 

[NY_Rob]

Thank you @shrink!!

It's long be suspected that a good portion of Gen 1 vampire drain is due to the inefficient design of the 12V charging circuit. You have bypassed that and hopefully your results are reproducible. If so, I'll probably dig out the dual circuit Battery Tender I had been using for my boat (before I converted it to LiPo4 batts) and connect it to my R1T in the fall. Winter is the time of highest vampire drain, it will be interesting to see if this mitigates most of it, which I suspect it will.

I'd love to see your setup, how you routed the 120v setup, etc..

 

[CarlM408]

I can already imagine the hack...12v battery tender fed by a good sized Li battery that automatically recharges off the vehicle when it's actually on, therefore allowing the truck to really have a restful and efficient sleep for once.

 

[Tim-in-CA]

I mentioned this in another thread if anyone has tested a 12V tender. I'm interested as well in how the battery tender was hooked up. I have an unused BT that I'd be fine hooking up to the 12V battery. The VD is ridiculous and adding up to 1.5kW or more per day.

 

[Singletracker]

So, the HV battery is constantly maintaining the 12v battery, that is running who knows what. Hence, the vampire drain from the HV battery. Maybe this is a stupid question, but what if one were to just disconnect the 12v battery (maybe with a switch) when VD coud be an issue - for instance, on a multi-day camping trip, far away from any available charging source. Of course, you woud have to leave the vehicle open so that you could gain access, after the battery has been disconnected. If a switch was accessibe externally, maybe you wouldn’t even have to do that. Obviously, the real answer to VD is identifying and disabling, if possible, those sources that are constantly draining the 12v battery. Considering it’s now been several years dealing with this issue, I am not optimistic that Rivian, or anybody else, has an answer to vampire drain.

 

[ohseedee]

thanks for testing/sharing. This makes a lot of sense and something I had suspected. Pretty much everything is going to run off the 12v and all the HV battery is doing it keeping the 12v topped off. I have a couple of battery tenders that I use for motorcycles and ICE cars that don't get driven much, but never got around to testing myself. Probably too much effort for daily use, but if you were to park at an airport long I could see parking outside and using one of those solar battery tenders

 

[ericindc]

This is cool and all, but its still wildly inefficient. You are still paying for the electricity from the battery tender. Glad to hear the drain on gen2 vehicles are lower.

 

[CarlM408]

This is cool and all, but its still wildly inefficient. You are still paying for the electricity from the battery tender. Glad to hear the drain on gen2 vehicles are lower.

I suspect, but have no data to back up, that the SOC loss is primarily from the computer systems running instead of being asleep, not from the power actually needed to top up the 12v system. Need more data to know...

 

[HaveBlue]

One idea was a larger 12v battery so it could bridge most nights and only charge when the car was being driven. Someone else had experimented with a stateful solenoid to interrupt the negative lead when storing it.

 

[C.R. Rivian]

TLDR:
I hooked up a battery charger/maintainer to the 12V battery in my R1S and so far (3+ days) there has been no loss in SOC from the main battery pack.

I returned to the mainland on Friday (8/9/2024) and left my R1S garaged in Hawaii. It was set to charge to 70%, but dropped to 69% at some point as it usually does. Before leaving for the airport with the high voltage battery SOC of 69%, I reduced the charge limit to 50%, attached the battery charger above to the 12V battery, and set it to charge an AGM battery. Vehicle is plugged in to an L2 charging station (240 V @ 40 amps)

What typically happens is that I lose 1-2% per day until my set SOC limit of 50%. The vehicle will then charge a little bit per day but usually stops at 49% for some reason until I return.

Well, it's only been 3 days but the SOC has stayed at a steady 69%. It's early, but I think this is working.

Will continue to monitor and provide 1-week, 2-week, 3-week updates, etc. until I get back on island.

I'll also post more photos of how everything is connected.

If this does work, I think the next step is attaching a Kill-A-Watt to the battery charger to get a sense of how much it's actually charging up that 12V daily.

I know these are preliminary results so no one get too excited but it's certainly a promising start so far.

Only photo I took was the one below which is the reading after I first attached the leads:

Are you hooked up via the charging wires near the hitch?

 

[Mark_AZR1T]

Thank you @shrink!!

It's long be suspected that a good portion of Gen 1 vampire drain is due to the inefficient design of the 12V charging circuit. You have bypassed that and hopefully your results are reproducible. If so, I'll probably dig out the dual circuit Battery Tender I had been using for my boat (before I converted it to LiPo4 batts) and connect it to my R1T in the fall. Winter is the time of highest vampire drain, it will be interesting to see if this mitigates most of it, which I suspect it will.

I'd love to see your setup, how you routed the 120v setup, etc..

What is this thing you call, winter?

 

[CBRacerX]

I have the same experience if I leave my camper hooked up via the 7-pin. Camper solar charges the battery and offsets the HV drain.

I have yet to check which battery is being maintained and if it causes issues because only one is.

This makes me want to try using an RV plug to feed solar panel 12v to the 12v battery when parled for extended periods (at home). Won’t help at night but might reduce the main battery pack drain somewhat. Other use for the RV plug would be easily connect a battery tender (I’ve got lots of those) instead of adding a typical plug connection to the 12v battery terminals and routing out to under the hood by the windshield - a common approach with my garage queen vehicles.

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