Power management videos are up

[Philpott]

In case you are that person who always reads ahead, here is the thread where you can share information BEFORE the seminar. A general outline of presentations will show up on these threads as soon as the speakers have a chance to cogitate and organize themselves. If you would like something addressed, ask here.

[BobJ]

The most common area of difficulty for skippers during the SHTP is power management. Some end up hand-steering for long periods of time due to insufficient power to run their autopilots, or they have a poor SSB transmission (or none) for the same reason. Some have had their engine key-switches become inoperative due to water intrusion, so they were unable to run the engine/alternator . . . well, you get the idea.

For the 2008 SHTP, Race Chair Synthia required energy budgets from the skippers. Due to power generation problems in the 2012 race, the energy budget requirement was re-instituted for the 2014 race.

Here are some of the energy budgets from 2008:
http://sfbaysss.net/archive-shtp-web...l_budgets.html

To prepare these, you need to measure how much amperage each item on your boat uses, and this leads to my question. I used to have a Xantrex Link 20 installed, which would show the change in amps flowing out as I turned on each light or other item. This made it easy to prepare the budget. However, the Link 20 caused other problems so I removed it. I now have a (portable) digital multimeter. How/where do I connect the probes to the wires for each electrical item on my boat to measure the amperage it uses?

Thanks!
.

[BobJ]

Here's another question. Those energy budget spreadsheets were somewhat bogus because the alternator output (line near the bottom) wasn't realistic. My alternator only puts out 30 amps if the batteries are nearly discharged, and output drops off quickly after only a few minutes of charging. In the budget, how can we compute a realistic charging time?

[todd22123]

I now have a (portable) digital multimeter. How/where do I connect the probes to the wires for each electrical item on my boat to measure the amperage it uses?

Thanks!

I've never done this, but I think I know the answer. The digital multimeter is set to measure current and is put in series in the circuit. http://www.youtube.com/watch?v=7lwZkl0yBqA

It seems like the multimeter could be wired in series right after the battery circuit breaker switch and then devices turned on one at a time to measure current.

Todd

[hodgmo]

An ammeter in series will work but be very careful when breaking and connecting live circuits!

Another way to measure current is with a clamp-on (Hall effect) current meter. This is convenient if the + and - wires of the circuit of interest are available separately. This video gives the basic idea, though for an AC circuit: http://www.youtube.com/watch?v=z-KfZvbjyBY Here's a more in-depth (but longer) look with specific dc measurement advice: http://www.youtube.com/watch?v=1sq2WRGPABw jump to 09:30 to see the meter in use. If you go this way make sure the DC current range matches your needs.

Does anyone know if/where the power management excel file is available?

[BobJ]

I think Synthia got it from here: (energyplan.xls)

https://pacificcup.org/kb/energy-management

But again, I don't think it's much good without a realistic alternator output - the "biggest" number on the page.

[sleddog]

For SHTP, a power management budget is sound prep. However, figures should be taken with a grain of salt. For those relying on solar, the charging figures should be cut in half.

As many have learned before, it can be cloudy much of the way to Hawaii. When running downwind for the second thousand miles, the sun goes behind the spinny or wung out jib at local apparent noon, also reducing solar charge input.

If relying on an alternator for primary charging, would suggest carrying a spare and tools to change it out.

[brianb]

Measuring with Ammeter in series: A multimeter rarely has the range to measure an alternator, in fact you can damage the meter for the cheaper models and blow a fuse in the more expensive versions.

Measuring with a shunt: A measurement "shunt" is a calibrated piece of brass that is placed in series with the battery terminals. These are used by most of the better charge controllers. They can be purchased at WM/Svendsen's etc. If you have a charge controller you may have one installed. Once in place, in series with the main 12 v power line going to the battery bank, one simply puts the multimeter, in DC VOLT mode, across the shunt terminals. Then you measure the voltage while the alternator is charging. You should see values below a volt displayed. To convert to current you simply divide the shunt resistance into the voltage read. A 0.01 ohm shunt and a 0,3 volt reading yields a charger current of 30 amps. The shunts are made to be mounted on the engine compartment and left in place. If you have a charge controller connected in a way that the alternator current passes through, it can be used as well.

Using a DC current clamp: Great if you can get one, make sure it is DC capable. Last I looked they were a bit pricey.

Here is a shunt that would work in vessels with alternators in the less than 50 amp range. They sell a variety.
http://www.rammeter.com/ram-meter-20...rent-shunt.php

I think Synthia got it from here: (energyplan.xls)

https://pacificcup.org/kb/energy-management

But again, I don't think it's much good without a realistic alternator output - the "biggest" number on the page.

[brianb]

It sounds like your alternator regulator may be a bit too aggressive in dropping the charge as the battery warms up. Do you have a separate field control on the alternator ? Likely not unless it is something like an aftermarket alternator. You may also be suffering from more voltage drop in the wires from alternator to the battery, giving the alternator a false reading of actual battery voltage. If you have a field wire that goes to the regulator, and can get to it, you can put in a little switch and a resistor or two to give you the ability to fool the regulator into telling the alternator to operate at a higher level. On my Hawkfarm I put a switch that I could throw and get full alternator output at will. This was really slick when I added a 100 amp Balmar alternator, when in full charge mode the little Volvo diesel would nearly stall. Of course this is over riding a circuit that is there to prevent over heating the batteries leading to other spectacular results if left unattended.

[Ragnar]

the Link 20 caused other problems so I removed it.

Slacker runs with a battery monitor, the Victron BMV 600 which I highly recommend. Best $160 I've spent on her. Great piece of mind since you know what's going on with your battery at all times - amps going out, amps going in - when you need to charge. It comes with the shunt, so it's easy to install. I've had no issues with it at all. There is also a 2 bank version.

Or you can screw around with a DMM...

Slacker Out