A better alternator delete

[Daox]

I mounted the dc-dc converters to the side plates. This was a bit of a pain because the circuit boards required M2 bolts. My holes were just a bit on the small side, and I couldn't fully thread them in without stripping out the allen head. There was just too much torque to continue screwing them in. So, I ended up drilling them out so the bolt only engaged about 1/8" into the plastic. This seemed to work pretty well.





Next up I have to figure out the input and output for power. I need to have either an onboard AC cord for charging, or a plug. I'm leaning towards a plug since all of the power supplies came with a nice 2 pin panel mount connector. I can reuse it easily enough.





For the DC output, I'm thinking I'll get some XT30 or XT60 connectors so they can easily handle the amperage. Something like the below picture would be ideal. However, I doubt I'll find a US seller, so I may make a mount from a normal XT60 plug.

[Ecky]

I picked up my first set of metric drill bits for tapping metric threads recently. I was rather surprised that I had to buy them online.

Semi-related, but why is it that even when I buy metric-threaded bolts from large box stores, they tend to have imperial head sizes? E.g. M6 with a 1/2" head.

[Daox]

12mm is very close to 1/2". Also, 19mm is very close to 3/4". If the heads are these sizes its very easy to use imperial tools on them.

A metric drill bit set would be a good idea. However, I've always been able to just print a nice snug fitting hole for almost all my 'threaded' holes. This is just the smallest hole I've ever had to do that with. I did test print it a couple of times, but I probably could have tested it once more!

[teoman]

What i did once with 3d printed cases is create stubs for the holes, and press/mushroom them with a soldering iron to attach the boards in place (after putting the board on).

I did this when I printed parts for my students and did not want to waste time and bolts for parts that I was going to give away.

It will make removing the parts more difficult, but you do not have to deal with bolts and tapping and nuts.

[Daox]

I have a question for the more electronically inclined. What gauge wire would you suggest to run for this thing? I'm guessing I'll need about 6ft of wire and it'll need to handle 20A. I was originally thinking of using 10ga, but now I'm starting to think that that may be a bit much. What do you guys think? Please explain why. I've used the link below in the past and its a bit confusing as it has a rating for chassis wiring and another one for power transmission.

https://www.powerstream.com/Wire_Size.htm

[Daox]

I did a bit more digging on this. The link below says to keep power losses at 3% or below.

https://www.engineeringtoolbox.com/a...uge-d_730.html

Conductors in electrical systems should not be sized with voltage drops exceeding 3%.

For a 12V system the maximum voltage drop should be less than (12 V) x 3% = 0.36 V.

So, I used this link to calculate the power loss.

Voltage Drop Calculator

It looks like 12 gauge wire gives me 2.5% power loss. 10 gauge gives a 1.6% power loss. So I think that 12ga should be a good fit.

Thoughts?

[teoman]

What is the price difference? And stuffing inconvenience?

Will the wires need a second life when the car fails? Like for a welder??

[Ecky]

Generally speaking, I find the size and cost difference between 10 and 12 to be so small that I run the larger gauge. Doesn't sound like you'll be pulling more than 20A but it's going to be continuous, and that power loss is all going to be heat. 3% of 300w is just under 10w... that wire might get a little warm on longer drives.

[Daox]

Originally Posted by teoman

What is the price difference? And stuffing inconvenience?

Will the wires need a second life when the car fails? Like for a welder??

The price difference isn't huge. We're talking $10 vs $16. I don't think routing should be a problem either way.

Second life would be to move these wires to a new vehicle. So, maybe I want to have a little extra length, which may push me up in size.

Originally Posted by Ecky

Generally speaking, I find the size and cost difference between 10 and 12 to be so small that I run the larger gauge. Doesn't sound like you'll be pulling more than 20A but it's going to be continuous, and that power loss is all going to be heat. 3% of 300w is just under 10w... that wire might get a little warm on longer drives.

Good points.

Thanks guys.

I think I'm going to go with 10 ga or maybe even 8 ga. This allows me to upsize the setup later as I would like to find a dc-dc converter that can handle more than 20A. 6ft of 10 ga should be good for just under 40 amps. 6ft of 8ga would be good for 60A.

[teoman]

Depending on the environment where it will live, the cables can lose their ability to conduct over time (corrosion, and the vibrations can sever some of the internal strands). So best to go slightly larger.