Rewiring a relic--power advice? Electrical gurus?

[Sinuous]

Not a problem, I didn't think you did.

Thing is, I have the relevant skillset in theory, and some in practice, but I'm running into things that have never been relevant considerations before. In cars and aircraft, battery endurance just isn't an issue. Now I'm up against a new problem, and it's interesting...but also a pain in the butt. Please, keep the help coming, I clearly need it!

[GordMay]

You might find this helpful:

http://www.cruisersforum.com/forums/...ats-372-2.html

[sushirama]

Also if youre planning on using 110 appliances on your inverter a good tool to have is a "kill-a-watt". You plug it in between the device and the outlet and it tells you your true power draw in watts/amps/kwh. I use this for computing to match device loads to UPSs(aka inverters) since the rated power consumption is not the true power consumption. For example my note book pulls 55watts on charge and 22watts after charging.


You can get one at Harbor Frieght for about 30bucks.

[Sinuous]

Handy device that. Just looked them up online, found one for $20. Thanks!

[GordMay]

Kill-a-Watt Power Monitor ($29.99 CDN):
P4400 - Kill-a-Watt Power Monitor

[Pblais]

Now I'm up against a new problem, and it's interesting...but also a pain in the butt. Please, keep the help coming, I clearly need it!

I think you really want to back all the way up and start by throwing away everything you have existing and even all the stuff you bought cheap at least in a virtual sense. The key to all this is to start by setting up the energy budget. You can have everything you want so long as you don't run out of power. That is the basic rule.

You could have 100 batteries but you can't recharge all of them and eventually most of them would be dead. It means the power you use in a 24 hour period has to be replaced in a similar time period. You can make it any way you like but if you don't make as much as you use you can't continue the game.

Inverter based devices that use high amp loads are very very bad. Volts X Amps = Watts. Read the UL labels on any device or use the above "Kill A Watt" device. Now do the math. A 1200 watt microwave uses about 10 amps at home but on the boat it uses 100 amps at 12 volts. But it takes some extra amps to make the amps it requires. How many minutes can I run the microwave before the battery bank goes dead? Not long! On normal bank 20 minutes would be a practical limit and no more. When you look at what it takes , you may not like the time it takes to recharge the batteries for that 20 minutes.

Start by working out amp-hours by device and look at when they get used. You'll find the AC to DC Inverter is just worst device known to a sail boat. The cheap ones waste more power than the good expensive ones. You do lose a bit of power converting power from one to the other. They are more at home on a twin screw trawler with dual alternators.

If you consider the batteries as a holding tank for the power you make whenever you can, it is easier. Unlike all the other things you have worked with you don't have a lot of power to work with. You really want to eliminate as much usage as practical. Making amp-hours is a PITA! It also costs you money - a lot of money!

There are quite a few threads in this electrical section on all the details, but I would start with an overall schematic of all the parts to the system based on an input / output study of how you expect to use power. Ripping out all the wire on the boat seems advised and replace with good tinned copper wire all neatly routed, marked and properly color coded and include a detailed diagram. That is a serious job.

Toss all electrical panels, isolators, and fuses that may already be there and use all new stuff. RE-evaluate all electrical devices that consume, create or control electrical power. You'll want both 12 volt and a 120 volt systems and maybe even a 220 volt (international) system as well. Once you can compute the loads you can size the bank, then work on charging systems that you might employ. The whole charging system needs to be synced so you have smart 3 or 4 stage voltage regulation based on battery type. This allows the charging to be as fast as possible without trashing the batteries. If you price out 280 lbs of batteries you'll know why.

This really should be a total bottom up and top down redesign before you start the destruction part. There can be a lot of choices to make and they all should work close together and be optimized for a lot of reasons. Running 12 volts DC power means wire size issues everyplace due to voltage drop over distance. This means you have to have detailed plans or you won't know how much wire to buy. Good marine grade tinned copper wire is not cheap! Don't even think about using household wire! High amp loads on DC wires can burn up the boat easily. Special details for a windlass are required - not optional.

You really should go through all the material in this entire section. Some of it makes more sense after you read it a few times and can sort through the ideas. You can find a lot of examples as well as arguments. Some of the suggested books may be handy. It also helps if you can find some brand new expensive boats and peak inside the panel and see what a great pro job looks like. Since you have done aircraft you have most of the idea. Making good water tight connections is tedious. There are about a million shortcuts you can take to kill yourself.

[Sinuous]

Given all that, what I think I'm going to do is consult with an ABYC electrician to help me design the system. I'll do the work myself, but obviously I need a hand with the overall design.

[Pblais]

I think I'm going to do is consult with an ABYC electrician to help me design the system

Sounds good. You still can do the work. I would do the energy budget. I would also add a battery monitor. It proves the case if the budget was right or wrong.

[Sinuous]

Thanks! Yes, I'm pencilling the energy budget now, and I intend to do all the physical labor.

[DeepFrz]

Here is a link to a site that will help with some wiring information.

Boat Wiring

and a checklist

Marine Electrical Check List

and some more information on wires (from a supplier)

Marine Wire, Boat Cable, Marine Battery Cable, Primary Wire - Gencable.com

[senormechanico]

Paul said:

"You could have 100 batteries but you can't recharge all of them and eventually most of them would be dead. It means the power you use in a 24 hour period has to be replaced in a similar time period. You can make it any way you like but if you don't make as much as you use you can't continue the game."

I totally agree, and at the risk of being flamed for thread drift, I wish our politicians would grasp that concept with the folks who produce the wealth and pay the taxes!

Steve B.

[CharlieJ]

Beating the expertise drum once again, I would suggest that you hire a knowledgeable, ABYC Certified Electrician to help you prepare an energy budget and then help you at least sketch out a rudimentary scheme for implementing said budget. Ten hours of consultation could well save you thousands of dollars and much frustration in the long run.
During execution of the project, have the Electrician periodically check your work. You will end up with an improved skill set, you will know your vessel's systems better than anybody, and the installation will be built to the ABYC Standards.