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Comment by blueintegral | Hacker News Reader

Hey everyone! I'm Hunter, one of the cofounders of Ohm. Let me know if I can answer any questions.

> if it’s ever about to reach the point that it’ll no longer be able to start your car, it’ll just turn itself off. Your lights will fade out and the radio will go quiet — but once you turn the key, everything will spring right back to life, no jump start required.

How does that work? If the battery stops providing current to prevent itself from being fully drained, you're not going to have power to the car's computers to actually start anything.

And will I have to reset all of my radio stations every time I leave the dome light on? With a manual I would almost rather run the battery until it is nearly dead.

One possibility:

It will know when the internal batteries are running low (the internal charge/discharge monitor IC doing battery "gas gauge" measuring). It'll maintain a reserve of a few crank's worth of energy, and trigger shutdown before that's exhausted.

It can also tell if the engine is running, because the alternator will be, and charging it. It can also monitor the active discharge current.

If the battery is low and there's a small but fairly constant discharge, it's probably lights/radio, and a timeout of an hour might be reasonable.

It could then either cut power completely, or regulate discharge current to a couple of milliamps or something, just enough to sense teh spike when the starter motor is switched in. At that point, it switches in the supercap or goes back to full power 12v mode, and the starter gets cranked.

The only downside I can see is that fully isolating the battery may have side effects that upset the ECU, radio or immobiliser system (I recall our radio would go into 'presumed stolen' mode if fully disconnected and require a PIN to work properly, I have no idea if/how that happens in modern cars though)

A "dead" lead-acid battery often isn't dead enough for that to happen, just htat it can't supply the ~200A that the starter requires to crank.

Bingo.

Is the starter even going to crank before the computer is running? Old cars, sure I can see this working.

Great product idea! One possible side market: have you looked at adapting the capacitor+battery combo for electric bicycles? It could be a great application: batteries for energy density, a capacitor as a buffer that can be filled quickly in a pinch (for charging while out and about, or from regenerative braking) and the capacitor could be discharged quickly for high-power acceleration. For short trips the capacitor would bear much of the load, saving battery cycles. The total capacity may need to be somewhat higher than 10Ah, but probably not much higher.

Interesting! I had not thought of that, but it makes a lot of sense. What's the average electric bike battery capacity?

Around the same order of magnitude. Some are less than ten, some are more. It seems like most are aiming for about 10-15Ah these days, at 36V, 48V, or higher. Since capacity translates into range, the greater the better.

Hi Hunter. Do you all plan to offer the battery in a minimal form factor (without the group 35 adapter)? I currently am running one of the Shorai LiFePo4 batteries in my track car. I really love the small size and weight, and would be willing to work around the smaller form factor.

Yes, it will be available in a smaller form factor. The core of the device will be a single modular design that will be inserted in the shell shown to give it the Group 35 size. Thanks for the kind words!

Would the output of the capacitors have to change for different applications, requiring different base models; for use in motorcycles, for example?

Nope! It could be the exact same internals. We'd just need to repackage it. The voltage on the capacitors is determined by the systems charging them. As long as its below the absolute rating for the caps, it will work. I believe most motorcycles actually operate at the same voltages as cars, though I could be mistaken.

Hi Hunter

How much safety testing have you done on your battery? Specifically, if an Ohm battery is involved in a collision, how will it fare? I know you are not content with shipping anything you aren't comfortable with your own family members driving with [1]. But, how do you know this? What makes you so sure? I don't mean to come across as interrogative - I am just curious.

[1] http://www.getohm.com/

edit: grammar

Yeah, safety is obviously the most important thing. Right now we're basing the safety claims on the those of the component manufacturers. But it's also going to be a function of the enclosure and component locations, etc. Once all of that is finalized, we'll have a 3rd party lab do abuse testing, crush testing, etc to make sure there aren't any bad failure modes. There's lots of good processes and test procedures already out there for doing that kind of testing on batteries.

Have you calculated how much money a typical driver would save in fuel due to losing 34 lbs of weight?

I have no idea if this ends up being a significant number, but I think the average driver spends somewhere around $10k in fuel over the expected lifetime of this battery; if cutting down the weight by 1-2% reduces fuel consumption by a comparable amount then Ohm would pay for itself.

Wouldn't it be cheaper for them just to eat less?

It depends on a lot of things of course, but yes, over the lifetime of the battery, it will pay for at least a large percentage of itself. We estimate about $10 a year gas savings.

I was writing a reply yesterday but didn't finish it-

I was going to say, for the first iteration of the product you could consider using classic lead-acid instead of LiPo. It's cheap, so it would help keep you price-competitive. It's absolutely proven as an automotive battery chemistry.

The difference vs. a classic battery would be, your smart circuitry to shut off the battery, and the cap stage would allow for a tiny battery even on big engines. Your LiPo model already sacrifices capacity, and the only other reason for a big battery is CCA, which the caps solve. Thus you could put an itty-bitty 10Ah lead-acid in an F-550. Bigger & heavier than a 10Ah LiPo? Sure, but still way smaller and lighter than modern F-550 batteries.

You could then move to LiPo for later versions as you get the truly novel parts of the product dialed in and costs starts to come down.

Hi Hunter, is there any regulation or certification process to make and sell car batteries ?

The DOT regulates your ability to physically ship batteries through the mail, but there's actually no formal stamp of approval that the DOT gives car batteries. They do have approval processes for other car parts, including electric car batteries though. We've been doing our own temperature and lifecycle testing so far, but we're still having 3rd party labs repeat all of that and also do destructive safety tests.

Thanks for the reply. Can you give us a sense for the costs of tests by you and 3rd party labs ?

I'm trying to understand what the barriers are.

I don't understand how you can charge $200 for this (plus shipping??). A battery at Costco costs $83 for 4.5 years full warranty.

I don't know how much you can talk about the tech, but I'm interested in how it fits with existing batteries & applications. Is it possibly an add-on to lead acid? A better jump starter? What about industrial like large motor plants where you need a jolt to get a lot of weight moving?

Actually, our very first prototype was a thing that sat on top your existing car battery. After talking to some people, it seemed like they preferred it integrated into the battery itself. It makes the price easier too, since you're not spending money on a battery AND a thing you put on top of it, just a better battery.

Industrial motors aren't something I've looked into a lot yet, but it could be interesting. I was just talking with someone the other day about using supercaps in robotics applications. Apparently some people are already putting small supercaps in the joints near the motors to help provide surge current during high accelerations or loads.

FWIW, I'd be interested in the thing that sat on top. Seems like that wouldn't wear out and would be cheaper than the combination.

I have an older car with occasional electrical gremlins. My battery is fine, but an ounce of prevention...

You can buy Lithium ion jump starters on Amazon today:

http://www.cnet.com/news/pocket-sized-jump-starters/

(linking the review because I don't know which brands are reasonable...)

How many times in a row is the battery able to start the car without needing time to recover?

It varies based on the specific car you have, but the short answer is "several". We've been measuring the current needed to start a bunch of different cars, and the results are pretty varied (based on temperature, engine compression, size, etc). One of our testers often needs a couple of starting attempts on his car and it sometimes takes him 3-4 tries before it starts with Ohm.

Will this work when its -30F?

http://www.mpoweruk.com/lithiumS.htm

Stricter regulations on shipping methods than for other cell chemistries. Degrades at high temperatures.

However, for Lithium Iron Phosphate LiFePO4: "Lithium phosphate cells are incombustible in the event of mishandling during charge or discharge, they are more stable under overcharge or short circuit conditions and they can withstand high temperatures without decomposing."

I would be interested in this and high temperatures as well, few things perform as expected here in AZ when it gets above 110F

Not exactly -30 but I know this guy had some success with off the shelf caps: https://www.youtube.com/watch?v=GUXM1XuLUIs

There's a few other vids on this topic if you search through the channel

>> Rated for -30°C to +50°C [1]

-22F ~ -30C

[1] http://www.getohm.com/

Is that expected to be sufficient? Typical automotive electrical components are rated over -40C to 85 or 105C. I think the engine compartment is typically hotter than 50C when a car is running. This might be more suitable to a car that mounts the battery remotely: I have seen BMWs with the battery in the trunk.

We're being conservative with the temperature rating for now. The components are rated better than that, but we're still running cycle tests in our temp chamber and waiting to get the system tested by an outside lab.

It's not sufficient in Canada. We regularly see temperatures below 30 C. Hopefully they can push it lower, because a battery that quits when it's cold out is pretty much worthless up here.

The capacitors are fairly immune to temperature variation since they don't store energy using a chemical reaction, and we can also dynamically adjust the standing voltage of the caps to increase power in cold conditions.

We believe so, but don't want to say it until we can verify for sure. Our temp chamber unfortunately has trouble pushing anything south of -20F and it's a bit hard to find weather that cold in August.

Will you be making a version for amateur/semi pro race car drivers?

They are always looking to shave off weight so it can be redistributed in the way they want. Being able to cut 30lbs would be a big deal.

Ohm can be used for racing, assuming the rules of the race don't require using a stock battery. A lot of our early users and testers actually come from the racing community.

This is exactly what I was thinking is the best use case.

The full lithium batteries are too expensive, and or don't provide enough starting amps.

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