EVDL Administrator via EV wrote:
On 30 Mar 2018 at 15:21, Jan Steinman via EV wrote:
Bed frames are nasty to work with. Ever try driling them?
All the time! WhatTM the problem?
Maybe yours are different, but the steel bed frames I tried to drill years
ago took a long time and dulled my drill bits.
I've had the same experience with them. Most are very difficult to cut
or drill. I suspect they get made out of random alloys of scrap metal.
So your results are likely to vary.
Hardware store angle iron is mild steel; easier to cut, drill, and weld.
I plan to connect [the batteries] with 3/4" copper pipe
I'm not so sure you'll like that in the long run.
Care to explain?
Copper and nickel makes a pretty decent primary cell. So your bus bars will
corrode quickly in the presence of the KOH electrolyte and other moisture.
If you use rigid bus bars of any kind, you have to mount the batteries so
thay absolutely cannot move relative to one another.
These are both good reasons.
Two other problems: The amount of copper conductor you have is rather
small. 3/4" pipe is actually about 0.875" in diameter and has about a
0.030" wall thickness. That means your cross-sectional area is
Circumference x Thickness = 3.14 x 0.875" x 0.030" = 0.0824 sq.in. This
is equivalent to #0 wire.
The other is that water pipe isn't pure copper; it's an alloy. It is
also "hard drawn" for rigidity. These significantly increase its
electrical resistance compared to pure annealed copper.
It will work in a pinch; but is a "quick-n-dirty" rather than a good
solution.
A better alternative would be to get some thin soft copper sheet. Cut it
into strips. Drill a hole in each end. Stack up enough of them to have a
cross-sectional area suitable for the maximum sustained current you
expect to draw. The sheets will be flexible, so this type of connection
will have some "give" to prevent cracking or breaking your battery
terminals.
The ends can be "tinned" by dipping them in a solder pot to provide
corrosion protection. Saturate the middle section with vaseline, and
then put heat-shrink tubing over it to protect the copper without
degrading the flexibility.
--
I look for what needs to be done. After all, that's how the universe
designs itself. -- R. Buckminster Fuller
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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