HW: Leveller Evo (name pending approval by Dave Mac)

[daveimi]

Don't think you're allowed NiCad's anymore, would have to be Nimh.

[maddox10]

New NiCd isn't cheaper or safer than LiFePo4.

If you can find them. In theory it's old stock that's being sold.

[JamesDavies]

Oh right- good thing I checked! Any idea why they were banned?

Do NiCads come with a C rating like Lipos do?

[daveimi]

I think nicads are banned from sale under EU law because of the harmful chemicals (cadium I think). Nimh sprang up in their place and are pretty much identical. Think they even work with the same chargers etc.

[RogueTwoRobots]

If you can get old Nicad packs, then you can use them as far as I'm aware (haven't read the rules recently) but yes they are no longer allowed to be sold commercially. There are packs that come up for sale now and again on here but they're old packs that will have been used. Yes they might be fine but they'll have seen battle in most cases.

Nimhs are the next progression. Similar in size & stats but I don't think they are/were as good at providing as high a discharge current as Nicads. For the money, you'd be as well using Lipos. If you're unsure, just ask the right people lots of questions on them, read all the rules regarding them, and have a look at how other HW users have fitted them. If you follow the right procedures and treat them properly, they'll just be like any other battery.

[maddox10]

The EU did ban NiCd due the cadmium in it. Rightfully so. It's a very harmfull heavy metal.

[daveimi]

This is a stupid question but did you build the original Leveller 2 etc. ?

[JamesDavies]

Getting this project back on track now I've got all the parts together. I was wondering what pressure relief valve people use?
Also, where do you source shutoff valves? Is there a high flow option that would eliminate the need for buffer tanks? I assume there isn't otherwise people wouldn't still be using buffer tanks!
Ta

[maddox10]

I could add an hydraulic ballvalve with a build on burst disk ,as mandatory on CO2 bottles, to an excisting extinguisher.
That would be high flow. But getting that certified, forget it.

PRV's, the search function here will give you several sources.

[grant_ploughbot]

Having a higher flow valve on the end of your main tank is likely to cause issues with sending alot of liquid CO2 through your solenoid valve. A low flow bottle valve and buffer tank seems to be fairly critical in giving any liquid that goes through time to expand into gas before having any major issues.

[JamesDavies]

Ah of course- I forgot the liquid CO2 factor.

Is the burst valve from a fire extinguisher too highly rated to be used as the safety in a bot (190 bar vs 69)?

[geeza]

The burst disk will prevent the bottle reaching its critical pressure. You need the pressure relief valve to protect the rest of the system from over pressure. I.e. a valve rated to the pressure of the weakest component in the system.

[maddox10]

The Pressure Relieve Valve has as main function to protect from overpressure or a too high working pressure (max1000psi/69bar).

The burst disk just protects the surroundings from exploding bottles.
About any modern industrial CO2 bottle is actualy a simular bottle as argon or such, therefor the test presure is 300 bar, and the working pressure 200 bar. This gives the reason for the 195 bar burst disk.

Paintball or Sodastream bottles sometimes have 135 bar burstdisks.

[JamesDavies]

Cheers guys. That's what I thought, just wanted to check.

Regarding buffers, is there any benefit in having a buffer volume of 8000cc versus 4000cc if my ram is only 943cc? I know the rule of thumb is no less than 3 times your ram volume, I'm wondering if the increase in pressure from 4L to 8L would be enough to justify the weight.

[JamesDavies]

Some progress, waiting for bullet connectors to come from China so I can get the batteries wired up. Then it's solenoid wiring and fabrication.

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