Installed frunk wired solar-capable 12v battery tender to reduce vampire drain

[SSteveEV]

I used that service in Mountain View California. The driver was driving my r1s around in sport lowest height. Driving 87mph on highway. Was rolling down my windows getting close to my house. I could see all this activity because vehicle was no longer in service mode and I had phone app open and I have Rivian home assistant integration. I am guessing the driver was smoking something and rolling windows down and spraying tons of cologne. My r1s reeked of cologne for 2 weeks I had to drive with windows open.

Big brother is always watching.
Or in some cases big father. Borrowed my dad's Model S once and when I got home he mentioned I should watch my speed. Never asked what speed he saw me going

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[SSteveEV]

I suspect that after the warranties start expiring, you will see homebrew and aftermarket solutions to install a larger battery in the frunk. One possible complication would be that Rivian has tuned the High Voltage -> 12 Volt hardware charging algorithm to optimize for the factory 18AH battery. Installing a 50AH battery could "confuse" the algorithm and throw errors such as "Why is it taking so long to charge this 18AH Battery? It must be going bad so I'll just throw an error to the driver display and phone home to Rivian to let them know".

Getting myself back on subject, would something like this House2Start DC to DC charger be the trick to keep the readable capacity for the stock batteries in stock range while powering from a larger battery stashed elsewhere?
https://house2start.com/

I think our 12v drain (measured from a tender not 400v pack) is so high that even a normal car battery would only last a few days without charging but coupled with solar it might do the trick nicely as a temp storage or overlanding solution.

 

[flaky]

Do you remove/stop the battery tender when vehicle is active? If yes, would dual charging from both vehicle and battery tender cause issue?

 

[mudito]

Do you remove/stop the battery tender when vehicle is active? If yes, would dual charging from both vehicle and battery tender cause issue?

No issues. You can have everything connected. Did this Saturday night.

When the vehicle stops charging and goes to sleep, then the battery tender will detect the Battery voltage and carry on with trickle charge if needed

 

[braedon2011]

Inspired by @shrink et al's amazing detective work and follow on efforts and forum posts on vampire drain, battery tenders, etc., I decided to install a wiring setup to enable solar capable 12v charging for camping, Sierra trips, and the like in my Gen1 R1T.

I was experiencing pretty gnarly vampire drain (up to 7-8mi per day on range) and we camp and go to Sierras a lot, so was eager to improve this based on all the information in the forums.

The setup and process:

Removed frunk tub via the 6 bolts.

Attached battery wiring to terminals for both 12v batteries to frunk (with overload fuse), later wrapped in nylon protective sheath and nicely tucked away:

These wires ran to about where the frunk wiring harness connects for the powered lighting. Then, connected to frunk via powerpole wiring harness which was zip tied to existing frunk wiring harness and through driver side light gromet and the space for that.

Also wired dual USB-C cables from frunk panel cover terminated into a weather proof connector for solar input and in same harness as powerpole so frunk can be removed easily

In frunk, I installed a Powerwerx anderson powerpole connector plug (2 sockets) and dual USB-C from the wiring harness (for solar in) and eventually a 12v input from battery to charge stuff while driving. I thought about an SAE style plug since more readily available but couldn't find a dual socket one.

Solar panels on roof (portable) will charge an Anker Solix C300 via the USB-Cs. The Anker will power two USB-C battery tenders and hopefully keep both 12v batteries nice and topped off during day and overnight.

Was a fun and pretty easy project overall, but couldn't have done it without this forums help! Thank y'all for all the inspiration, technical posts, and awesome community.

Parts list:

1. 2 x SAE to powerpole (to connect battery tender to powerpole sockets)
   https://www.amazon.com/dp/B0BZZ935MR
2. 2 x powerpole to battery terminal (with inline fuse)
   https://www.amazon.com/dp/B0CFPKLSRC
3. 2 x powerpole to powerpole wires to go from in-frunk socket to frunk wiring harness connection point (so can remove frunk in future by disconnecting at this point vs. battery)
   https://www.amazon.com/dp/B0C4SD64QH
4. Waterproof USB-C connectors for solar input
   https://www.amazon.com/dp/B0DQPFJ399
5. Powerwerx powerpole panel mount plug / socket for in frunk plug
   https://www.amazon.com/dp/B097QDKJJ2
6. Dual USB-C panel mount socket for in frunk plug
   https://www.amazon.com/dp/B07SRPK349
7. Panel mount two hole socket cover for nice clean in frunk look
   https://www.amazon.com/dp/B0C862ZGD5
8. 2 x USB-C powered battery tender
   https://www.amazon.com/dp/B0DCVX6LYZ

Have the battery tenders worked and stayed healthy? Would be amazing to be able to use USB-C tenders for the long run.

 

[Ervan]

So far! I haven't used them on a daily basis, but did use them camping a few times.

I'm not sure they regulate the trickle that well so I need to do some testing as overnight (1 night) one time they drained a 288 Wh Anker (!) and that seems like a lot for 12v trickle charging/top off. But, could be extenuating circumstances like maybe I forgot to turn off GearGuard in that instance.

That said, I haven't found a single other USB-C trickle charger -- it's really hard to search for as most are opposite, powering a USB-C from the battery vs. other way around.

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