On Sun, 15 Jan 2023 10:25:05 -0000, "Commander Kinsey"
<CK1@nospam.com> wrote:

<snip>
>
>>>> Fuses that interrupt DC are different animals.
>>>
>>> Bollocks. The voltage matters, and I'm giving it way less then the 240V it's rated at.
>>
>> Read more. The I^2t rating of a fuse is good only in it's rated
>> application. AC current is self-interupting, by source reversal.
>> DC isn't and will arc, potentially with explosive results.
>
>12V DC will not arc across a 2 inch gap.
>
Wearing eye protection and gloves, you might wany to investigate
this yourself some time. Through a suirable current-limiting
impedance (~your cables are intended to do this), apply a short
circuit at the far end of the circuit and then remove the short
(if you can). Actually, welding goggles might be recommended.

You'll probably do this without flinching only once in your
life. The flinch becomes automatic on all subsequent occasions.
DC battery holders will generally be provided with a (useless)
cover.

>>>> Your illustrated clamp has obviously not run at more
>>>> than few tens of amps. At 100A you'd be able to measure
>>>> the voltage drop and probably be able to smell it.
>>>
>>> The clamp isn't carrying the current.
>>
>> With such modest terminal contact,
>
>Half of it.

Two circular objects do not mate with half of any contact
surface area, no matter how it's calculated.

>
>> the iron clamp will
>> be developing the same (increasing) voltage drop as the
>> terminal contact degrades.
>
>Bullshit. The fuse touches the terminal.
>
>> Measure it.
>
>The drop across the fuse and the clamps in total is 6.5mV at 10.3A. So at the rating of the fuse, 80A, it would drop 0.05V and dissipate 4W. Negligible.

That's about 10x what is intended for a fresh joint. It will degrade
with time, use and temperature cycling.
>
>> <snip>
>>
>> As long as the battery's no actually doing anything, as your
>> app describes, you'll not have to worry about it.
>
>Well one of the power supplies failed - I opened it and found two shorted out power transistors which were not tightly attached to the heatsink and had overheated, despite the power supply never having even blown body temperature air out of it. There was a transistor smell in the room, not sure if it was those (which didn't look damaged, only the dust on them was a little brown) or the other supply which I measured as running at the full 83 amps, so was presumably limiting itself (it doesn't actually say on the specs anything about limiting, just short circuit protection and overheat protection, so I don't know if it shuts off or slows down). Some of the cards were misbehaving, which doesn't make a lot of sense.

Derating of power from labels is common safe practice.
You should consult the manuals for limiting characteristics
if you want predictable load performance near or above
ratings.
>
>I can't find anywhere (can you?) a graph of what voltage to expect from a 130Ah leisure battery (as in the thicker plates variety presumably) at various current draws? It would only have been drawing 7 amps and I can't believe that made a drop of 1.2 volts (which should be required to make the cards play up). Mind you I'm pretty sure some of the older cards get upset at 12.3 volts, because since I installed the bus bars two are working fine that didn't used to work at all.

The closest you'll find will be 'load test' voltages, often stated as
nominal under either 15 second loading, or to 'end of discharge',
from an innitial SOC or open cct terminal voltage.

A 'load test' is nominally 1/2 of the Cold Cranking Amps (CCA) or
3 times the Amp-Hour rating. A 12V lead acid battery is considered as
dead <12V.

Your application load being ~ constant and self-determined, sets your
loading for test at your site.

>
>> Happy number crunching (WCG since Y2K on 3+ machines)
>
>Lightweight! :-P
>
>My current annoyance is LHC, their CMS tasks. They transmit a huge amount of data while running, from inside a virtualbox. But they're very impatient. When my FTTC pitiful 6Mbit uplink is saturated with them, some of them crash or give up. I'm having to manually adjust how many run, and do some of their Atlas tasks aswell, since if you ask for "anything", you only get CMS!

I've been avoiding 'Mapping Cancer Markers' because, unless there's
a cure, there's no pojnt in identifying predicators - it just becomes
another method for insurance companies to screw you.

RL