Remote Battery Terminals

[s/v Jedi]

For a battery charger I recommend the 50A connector which is double pole and has a mounting hole as well. Look at which contacts you get… different ones for different wire sizes.

https://www.amazon.com/gp/product/B07CHD4JCK

[Jammer]

I again find that I agree with s/v Jedi that the SB50 connector would be the best choice for a 50a charger. The smaller "45a" connectors are undersized for 45a continuous imo.


I use both styles depending on the situation. I use the larger SB50 connectors for outboard motors and for the battery connection on small boats. I use the smaller sizes for smaller (15a) external battery chargers and for various portable equipment where many people would use a cigarette lighter connector.


Powerwerx.com has recently added quite a few mounting options for the SB50 connectors that you might find useful.

[GypsyOwner]

Whatever you do, don’t do what the previous owner of my boat did, and wire the battery to 2 large naked bolts sticking out of the woodwork to which a charger could be clipped on

1) The voltage eats away at the wood when it’s damp
2) Even worse, all it would take is a large can of WD40 or spray paint to be placed next to such an arrangement for you to have made a very effective incendiary bomb



I muttered to myself ‘I don’t like that arrangement’ the day I boat the boat. And I removed it and binned it a day later when a crew member spread out some tools and spray cans right next to it

[OS2Dude]

Steel and Stainless Steel bolts are unsuitable.

Every terminal stud I've ever seen has been a Stainless Steel bolt. The bolts are not what transfers the electricity, they only provide a way to hold the lugs to the tinned copper base. I don't see it worth the time/money/aggravation to roll your own thru-bulkhead terminal. For example, see these: ($30.00 USD/pair) https://www.amazon.com/Battery-Bulkh.../dp/B07QKPHMH1

IMO what I understand you want to do is not a good idea. You don't need/want to have exposed terminals that can be shorted. Just having a silicon cover is no guarantee. I would consider buying a real marine rated shore powered battery charger that you could wire into the main bus bars before altering my boat to make it 'easier' to use one with oversized alligator clips that clip on to the battery posts/bank busbars.

What I actually did was to just go with a 100% solar setup. No issues for over 5 years.

[Wotname]

Every terminal stud I've ever seen has been a Stainless Steel bolt. The bolts are not what transfers the electricity, they only provide a way to hold the lugs to the tinned copper base. ........

SS is fine for a terminal stud; not so fine for a through-bulkhead connection.

A through-bulkhead connection as described by the OP would transfer the current through the bolt shank.

[sailingharry]

Originally Posted by Wotname

This is the number one question!

Steel and stainless steel bolts are unsuitable. Copper is good but hard to obtain, a bit soft and corrodes quickly. Brass is sort of OK but they have to have a greater diameter than copper for a similar resistance.

Ideally you want large diameter plated (tin/silver/nickel) brass bolts. Price them before attempting to make your own.

Stainless bolts are indeed poor conductors. However, they DO conduct. With small (under 15A) battery chargers, the loss is likely minimal. Further, as the battery comes up to full charge, the current drops and the voltage loss drops, until at full charge you have no current and no loss. The point is that I doubt stainless bolts would add an hour to the total charge time, and I doubt that they would make measurable heat (or at least, heat of concern) -- again, a 1V drop at 15A is only 15W.



This of course is supposing that the charger isn't some big automotive jump start charger putting out 75A continuous!

[s/v Jedi]

You can buy copper threaded rod right from McMaster. Don’t use brass or bronze.

[GordMay]

Originally Posted by s/v Jedi

You can buy copper threaded rod right from McMaster. Don’t use brass or bronze.

Offering high electrical conductivity and formability, 110 copper [AKA: ETP copper] is 99.9% pure.

Although Copper All-Thread Rod is not uncommon, I didn’t see any at McMaster-Carr [I possibly missed it]:
Threaded Rod ➥ https://www.mcmaster.com/products/th...hreaded-rods~/
Bronze Threaded Rods ➥ https://www.mcmaster.com/products/th...threaded-rods/

[sailingharry]

Originally Posted by OS2Dude

Every terminal stud I've ever seen has been a Stainless Steel bolt. The bolts are not what transfers the electricity, they only provide a way to hold the lugs to the tinned copper base. I don't see it worth the time/money/aggravation to roll your own thru-bulkhead terminal. For example, see these: ($30.00 USD/pair) https://www.amazon.com/Battery-Bulkh.../dp/B07QKPHMH1.

In the vast majority of cases, you are correct, the terminal uses SS studs. That's because the current flows from direct contact between the cable terminal and the bus bar, with the SS stud simply holding it in place. In a thru-bulkhead arrangement, that changes -- but the link you provided has an interesting solution, where the bolt still just holds it against the "bus" but the "bus" is a copper tube that the bolt passes through. Again, essentially no current passes through the SS stud.


Of special note, the "bulkhead connector" you linked to won't fit on most bulkheads on a boat. It is limited to 13/32", which is less than 1/2", and all my boats use 1/2" plywood by the truckload.


While I agree with the general consensus that the OP's idea is a bad one, I still stand by my assertion that, if he is using a homeowner grade battery charger (ie, under 15A or so), that SS won't significantly compromise his effectiveness. EDIT: My statement stands, but doesn't apply here, as I just saw is later post that this is a 50A charger. SS studs probably aren't a good idea here. But I have noted that many alternators use a steel stud as the output conductor (I think some use a copper sleeve to solve that-- or perhaps I've just wished they did....).


The safety of this approach would be MASSIVELY increased with the addition of a decent (ANL at least) appropriately sized (one size over the charger, and suitable for the wire) fuse.

[GordMay]

Originally Posted by sailingharry

...
Of special note, the "bulkhead connector" you linked to won't fit on most bulkheads on a boat. It is limited to 13/32", which is less than 1/2", and all my boats use 1/2" plywood by the truckload...

Indeed.
But, a 1/2 inch [12.5mm] nominal [3/5 ply] sheet of plywood is, normally, 15/32 inch actual thickness. [still too thick]
A “finish” sheet of plywood [G1S/G2S], used for surfaces like cabinets or furniture, will be sanded. This will remove a small amount of thickness, as well, giving a ½" sheet [12.5mm], a thickness of 7/16" [11mm]. [still too thick]

[Pete7]

Originally Posted by jcapo

For the 15, 20, and 45 amp terminals.

https://powerwerx.com/tricrimp-power...-crimping-tool

Thanks, I have something very similar for crimping MC4 connectors. Need to see if they will do the 50A Anderson connectors.

Pete

[OS2Dude]

If you insist on putting live electrical connectors in the bulkhead, get a length of 12.7mm (1/2") or 20mm (3/4") copper rod. Cut to fit the thickness of your bulkhead plus an inch +/-. Drill and tap the side the battery cables will connect to for an M8 (5/16") or M10 (3/8") bolt. Leave the excess rod stand proud on the other side and clip to them. You will have to find something to cover them while not in use that will STAY. Remember these will be electrically live the ALL THE TIME, even when not being used to charge.