12V Questions

[chrismc]

Are you able to share any insight into the DC-DC converter architecture and capacity? In particular, if one were to theoretically add a third larger 12V battery for short-term high-draw loads, what type of charge rate for that accessory 12V system could be sustained from the DC-DC converter?

I can’t comment to that as that was not my main area of expertise at Rivian, nor will I speculate. I have my ideas why that is but I won’t share company internals that are not public knowledge. Especially here since Rivian does monitor Rivian Forums.

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[EVLander]

Are you able to share any insight into the DC-DC converter architecture and capacity? In particular, if one were to theoretically add a third larger 12V battery for short-term high-draw loads, what type of charge rate for that accessory 12V system could be sustained from the DC-DC converter?

In any system, if you are going to add a battery in parallel to a system, it should be the same capacity. Otherwise you risk short charging the larger battery or over charging the smaller one. One simply solution would be to replace the two batteries with a pair of higher capacity batteries. Voltage and charge profile would still be the same as long as the are of the same type. Charge time increases due to the larger charging capacity.
The information you seek is unknown to me, but I’m looking to find out myself just to better understand the load capacity. I would imagine that it’s pretty high. It would need to charge two batteries, and power the 12v system to what ever is on, lights, ECUs, and so on, all at the same time.

 

[chrismc]

I was thinking of using an ignition-switched amp-limiting charge controller between the Rivian 12V system and the accessory battery.

The load I’d like to solve for is a winch; which can exceed 400A. I’m quite sure the Rivian’S DC-DC converter cannot accommodate that so a “surge” battery that can slowly be refilled seemed like a good option. An ICE vehicle will typically have a 500+ CCA battery (often AGM deep-cycle) backed by an alternator charging at up to maybe 140 or 180 amps to power the winch in short bursts.

In any system, if you are going to add a battery in parallel to a system, it should be the same capacity. Otherwise you risk short charging the larger battery or over charging the smaller one. One simply solution would be to replace the two batteries with a pair of higher capacity batteries. Voltage and charge profile would still be the same as long as the are of the same type. Charge time increases due to the larger charging capacity.
The information you seek is unknown to me, but I’m looking to find out myself just to better understand the load capacity. I would imagine that it’s pretty high. It would need to charge two batteries, and power the 12v system to what ever is on, lights, ECUs, and so on, all at the same time.

 

[EVLander]

I was thinking of using an ignition-switched amp-limiting charge controller between the Rivian 12V system and the accessory battery.

The load I’d like to solve for is a winch; which can exceed 400A. I’m quite sure the Rivian’S DC-DC converter cannot accommodate that so a “surge” battery that can slowly be refilled seemed like a good option. An ICE vehicle will typically have a 500+ CCA battery (often AGM deep-cycle) backed by an alternator charging at up to maybe 140 or 180 amps to power the winch in short bursts.

Rivian winch pulled power straight from the pack using their own winch controller. I like the idea of using an AGM battery for winch power. I would need to look into this but perhaps you can use a secondary DC-DC charger Just for the winch battery. One that would kick on when the 3rd battery voltage drops below a min voltage. I imagine the winch battery wouldn’t cycle as much.

 

[EVLander]

I have a question about your, "If..."

Does this mean that some (presumably newer) R1 vehicles are been produced with a single battery in place of the dual setup? I've seen speculation about a change but I don't recall seeing anything concrete.

Thank you!

https://www.autoevolution.com/news/...olt-battery-for-newer-r1-vehicles-216823.html

 

[Thedude]

The 12v batteries have no issues down to -20°F sitting outside.

 

[SoCal Rob]

https://www.autoevolution.com/news/...olt-battery-for-newer-r1-vehicles-216823.html

Thanks, though a couple days after I asked that question, we got the important details from @rhuber on 6/16:
https://www.rivianforums.com/forum/...-r1-only-have-a-single-12v-battery-but.16138/

That AutoEvolution article from 6/20 even gives credit to Ryan’s thread via the “discovered this” link in the article.

 

[fredgass]

I can tell you it kicks in at 12.09V. Then it charges for about 1h40m, if it is a full recharge. What are you.. I mean your friend.. trying to do?

Hello
I installed two 12V 17AH batteries in my Rivian instead of the original ones which were Rivian 12V 18H. Do you think this 1AH difference can affect the vehicle functionality ? Since I have my displays which aren’t working
Thanks

 

[rivian_germany]

Hello
I installed two 12V 17AH batteries in my Rivian instead of the original ones which were Rivian 12V 18H. Do you think this 1AH difference can affect the vehicle functionality ? Since I have my displays which aren’t working
Thanks

I don't think it would make a difference, as long as the batteries can supply more than 12.2V continuously. Are you experiencing an issue currently? If you don't connect BOTH batteries at the same time, you could have issues, from what I have read. If it isn't working, try disconnecting them and then reconnecting both 12v batteries at the same exact time. You might need a friend or an extra cable to jumper them together until they are bolted in.

 

[fredgass]

Yes ! I have the 3 displays that aren’t working but the vehicle is running fine. Since I don’t have the displays I don’t have access to all functions like air conditioner, updates, etc….

 

[CruxOp]

There was a lot of discussion with going to 1 battery. After I had left the company, I wasn’t sure if they actually went with the design change. So I made that statement as a blanket statement incase they went with the change.

The switch definitely happened. Our July build R1S has one battery, verified by mobile service tech who took off cover and showed me.

 

[MPFuini]

Did anyone ever crack this nut?

I'm looking to add a second 12V AGM battery on a 2025 R1T to run a 1200W amplifier and I was wondering if anyone was able to figure out the output specs on the 400VDC-12VDC converter.

The 2025 R1T has a single 12V 20Ah battery under the passenger seat and it's not nearly enough capacity to power the amp. First big bass drop triggered my 12V service warning immediately ?

The plan is to isolate the two batteries using a Victron Argofet Battery Isolator allowing the onboard DC-DC convertor to charge both batteries independently. From what I've read, there's very little voltage drop and should work perfectly if the DC-DC converter can handle the extra load.

https://www.victronenergy.com/battery-isolators-and-combiners/argo-fet-battery-isolators

Thoughts? ?

 

[MacO512]

Did anyone ever crack this nut?

I'm looking to add a second 12V AGM battery on a 2025 R1T to run a 1200W amplifier and I was wondering if anyone was able to figure out the output specs on the 400VDC-12VDC converter.

The 2025 R1T has a single 12V 20Ah battery under the passenger seat and it's not nearly enough capacity to power the amp. First big bass drop triggered my 12V service warning immediately ?

The plan is to isolate the two batteries using a Victron Argofet Battery Isolator allowing the onboard DC-DC convertor to charge both batteries independently. From what I've read, there's very little voltage drop and should work perfectly if the DC-DC converter can handle the extra load.

https://www.victronenergy.com/battery-isolators-and-combiners/argo-fet-battery-isolators

Thoughts? ?

I'd think you might be able to get that setup working, I don't have much argofet experience but it appears to me that would involve changes to the Rivian stock 12v battery wiring.

I'd prefer to just have a 100ah Lifepo with a 200a BMS as the secondary battery power the Amp. Then the only connection between the systems is a DC-DC converter to only pull (not push) power from the Rivian 12v to the Lifepo/amp.

https://www.litime.com/products/12v-100ah-max-lithium-battery
https://www.victronenergy.com/dc-dc-converters/orion-xs-12-12-50a-dc-dc-battery-charger

 

[MPFuini]

I'd think you might be able to get that setup working, I don't have much argofet experience but it appears to me that would involve changes to the Rivian stock 12v battery wiring.

I'd prefer to just have a 100ah Lifepo with a 200a BMS as the secondary battery power the Amp. Then the only connection between the systems is a DC-DC converter to only pull (not push) power from the Rivian 12v to the Lifepo/amp.

https://www.litime.com/products/12v-100ah-max-lithium-battery
https://www.victronenergy.com/dc-dc-converters/orion-xs-12-12-50a-dc-dc-battery-charger

It's funny you say that, because that's exactly the route I ended up going. I haven't been able to test it yet though, because the battery I got from Renogy ended up being defective, so I had to send it back. Here are the components I went with though.

REGO - 12V 104Ah Super Slim Solid State Battery

RENOGY 12V/24V IP67 50A DC-DC Battery Charger with MPPT - Renogy United States

I'm also going to add a 100W solar panel on the hood to keep things topped off and hopefully cut down on vampire drain.

Rivian Hood Solar – LensunSolar

Once I have everything installed and tested, I'll post pictures and comment on how it works.

 

[Riviot]

Did anyone ever crack this nut?

I'm looking to add a second 12V AGM battery on a 2025 R1T to run a 1200W amplifier and I was wondering if anyone was able to figure out the output specs on the 400VDC-12VDC converter.

The 2025 R1T has a single 12V 20Ah battery under the passenger seat and it's not nearly enough capacity to power the amp. First big bass drop triggered my 12V service warning immediately ?

The plan is to isolate the two batteries using a Victron Argofet Battery Isolator allowing the onboard DC-DC convertor to charge both batteries independently. From what I've read, there's very little voltage drop and should work perfectly if the DC-DC converter can handle the extra load.

https://www.victronenergy.com/battery-isolators-and-combiners/argo-fet-battery-isolators

Thoughts? ?

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