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Rivian can switch to 48V for more gains. https://news.ycombinator.com/item?id=38576612 https://news.ycombinator.com/item?id=38576612: The move to 48V means muc
by thelastgallon 2y ago
Rivian can switch to 48V for more gains.
https://news.ycombinator.com/item?id=38576612 https://news.ycombinator.com/item?id=38576612: The move to 48V means much less power is lost (power loss = (IxI)xR ), cables can be much smaller, cables and terminals can be much lighter and much less copper can be used used.
Discussion:
Tesla shares 48V architecture with other automakers: https://news.ycombinator.com/item?id=38557203 https://news.ycombinator.com/item?id=38557203
- jondwillis 2y agoThose are rookie numbers. Let’s bump it up to 96V while we are at it.
- throwaway48476 2y ago50V is the generally accepted safe cutoff. There are separate electrical certifications for 'low voltage' <50V.
- addaon 2y agoSELV is often capped at 60 V, not 50 V, although this is often treated as “48 V with crappy bounds”. An example that takes advantage of this would be PoE, which allows 44 V - 57 V at the PSE; but most PSEs are, in my experience, in the 54 - 57 V range.
- yencabulator 2y ago48 V + charging ends up around 54-58 V, so the 60 V cap is needed for 48 V systems.
- addaon 2y agoOnly for 48 V systems that have a battery, which does not apply to PoE, and does not apply universally to 48 V automotive approaches (although the CyberTruck does use a 48 V battery).
- yencabulator 2y agoWe're talking about the accessory battery in a car, though.
- addaon 2y agoWe're talking about the LV rail (nominally 48 V or 12 V) in an electric car. There are two design paths here -- you can have an HV to LV converter capable of supplying the average load, and have an LV battery; or you can have an HV to LV converter capable of supplying the peak load, and save the cost, weight, and failure rate of an LV battery. Tesla chose the former, but it's not the only path here.
- yencabulator 2y agoSure, in an EV it's possible to choose not to have that second battery. In an ICE car, it's needed to start the engine. So at least the ICEs are much more likely to settle for 48V than something closer to 60V, to leave room for charging. The manufacturers that make both ICEs and EVs are going to want to share components, so the pure-EV components are likely going to be built for 48V too.
- maxerickson 2y ago60 volts DC is treated as a safety threshold. Human bodies start to conduct better about there.
- amluto 2y agoThere are massively diminishing returns. 1kW at 12V is 83A, which needs a rather beefy wire that is expensive to buy, annoying to route, difficult to route, and needs careful termination with large tools. 1kW at 48V is ~20A, which can be done with 12 gauge wire, which is not bad at all to work with.
- hulitu 2y ago[flagged]
- Vecr 2y agoNot really, if the converter's switching it should be fine either way. Generally you would want to tune it for the input voltage but in many cases the input range is large.
- stephen_g 2y agoFew microcontrollers even need 5V anymore. But your general concern sounds like something that might have been a problem in the ‘90s, but step down switching regulators are dirt cheap and a lot more efficient now.