Voltage settings for Xantrex C40 in yacht

[la7qz]

Hi

I'm installing a Xantrex C40 in diversion mode on a sailboat with a Kiss wind turbine. The boat also has other charging sources like the inboard engine and shore power charger. Since the boat is chartered, we need a foolproof system.

The issue I'm worried about is the C40 dumping when other charging sources are running, particularly with the engine. Using a relay to disconnect the dump load is not an option in this case as there will be times when the boat will be motoring for several hours into a headwind, so the Kiss will be producing and still needs to be regulated.

I would expect that I can get a reasonable solution simply by setting the voltage settings for the C40 somewhat higher than the charging voltage from the engine alternator. Any suggestions for appropriate voltage settings would be welcome.

Owen

Resectioned

[Flux]

That seems your best option. See what the engine driven alternator charges at and set the C40 just above. If it is a standard vehicle alternator intended for normal starting duty you will have no problem as they tend to limit near float volts.

If you have a special marine regulator designed to charge batteries rather more quickly then the voltage will be higher and you will need to just let the C40 go above that. As long as you have flooded batteries I see no real problem.

For the limited periods on the wind turbine then even up to 14.4v shouldn't matter much.

I take it you couldn't sort the LVM regulator, a pity as it was intended for this sort of duty.

Good luck

Flux

[snowcrow]

  Would it be possible to control the field winding of the alternator with a relay off the AC side of the wind turbine??  That would insure that only power from the turbine is being dumped.

Snow Crow

[Flux]

Just another thought. You only need a low enough resistance to dump the wind generator output ( not sure what it is ). Whatever you do the dump load mustn't exceed 40A. but I doubt that the turbine is near that.

With care in the settings you shouldn't dump any engine power but even if you do then it will be when the batteries are well up.

I still don't see any problem unless you have VRLA or gell batteries.

Flux

[snowcrow]

  Sorry, I think I meant to say armature winding!!

Snow Crow

[ZooT]

Quote:

You only need a low enough resistance to dump the wind generator output ( not sure what it is ).

How would one determine the proper resistance for this dumpload?

[Flux]

Choose a resistor that will dump the turbine maximum amps at 14v.

Flux

[TomW]

In case you do don't know Ohms Law that resistance can be found by dividing the voltage by the current.

So 14 volts / [max amps from turbine] is the resistance you need.

Cheers.

TomW

[la7qz]

Hi

Interesting idea, but I don't want to be too creative here. This boat is leaving my "sphere of influence" and will most likely be worked on by several electricians with different levels of knowledge and experience down the line, so I don't want to homebrew anything that will be too confusing to the uninitiated.

The other problem is that while the owner of the boat is a friend, he is also a customer of the company I work for. They charge $65 per hour for my work, so there's a  limit to how inventive I can get on the customer's time. (Unfortunately, I don't see much of that money).

Owen

[la7qz]

Hi

Yes, I gave up on the LVM regulator. Island Waterworld have taken it back and the owner of the yacht bought a Xantrex C-40 from the US dealer of the Kiss turbine with the dump load they recommend. I installed everything today and set it to start dumping at 14.2V which should be the cutoff point for the regulator on the engine alternator in a tropical climate. Now that there is no risk of overcharging, I'll leave the turbine running until the owner comes back. By then, the batteries should be full, so we can test it with the engine running to fine tune the regulator.

One little tweak I'm thinking of is to install a small lamp in parallel with the load to give a visual indication when it is dumping. It should then be easy to fine tune the voltage setting.

I hope to get my own turbine flying this weekend. I wasn't going to use a regulator (since I live aboard full time), but I'm now considering buying a C-40 and installing a hot water tank with a 12V heating element and using that as the dump. The water heater can also be heated by the engine cooling water of course, so there is still a source of hot water when there is no wind. There is little point in using a mains powered heating element since my only source of mains power is my Freedom 10 inverter/charger.

Owen

[ghurd]

"One little tweak I'm thinking of is to install a small lamp in parallel with the load to give a visual indication when it is dumping. It should then be easy to fine tune the voltage setting."

That will be Very inaccurate.

G-

[ZooT]

My 12 volt goodies all came with those cigarette lighter plugs......and all of them had an LED with a resistor in the plug.....

Could one use something like that over the dumpload without screwing up the entire thing?

[ghurd]

If the duty cycle was high enough to see it.  An LED would be better than a bulb.

A bulb will not react fast enough when dumping with a low duty cycle (you'd never know it was on).

A small bulb migh be OK for showing a high duty cycle (full battery and high charging current), but it wouldn't be very accurate for setting or adjusting anything.

Plus IIRC, the manual says not to use a bulb, and a 40W bulb can draw 200A when cold (low duty cycle) which can lead to the unit shutting down.

G-

[la7qz]

Hi

I tested the LVM regulator (which we couldn't get to work with the Kiss turbine) on the bench with a variable power supply, small 12V battery and a 20W light bulb in place of the dump load. The light bulb started to glow at 13.9V battery voltage and was fully on at 14.2V. Very predictable and no difficulty reading it.

So, I expected that using a light bulb in parallel with the dump load on the C40 would give an equally predictable indication. So if the battery bank was full and the engine was running, I could turn the set voltage down until the bulb starts to glow and then turn it ever so slightly up again.

Oh, and the manual warns against using light bulbs as dump loads because they are unreliable, not against using a small light bulb in parallel with the dump load as an indicator.

If I were to use lightbulbs as dump loads, I would use an array of at least 10 or 20 bulbs so one bulb blowing would not make much difference.

Owen

[Ungrounded Lightning Rod]

Another reason they warn against using light bulbs as dump loads is that they pull a LOT more current when cold (i.e. first switched on) than they do once they are up to operating temperature and shining merrily.  That means the dump load controller has to be able to switch a lot more current than you would expect from calculating from the lamp rating, and a lot more current than you end up dumping on the average.

This can result in a burned out dump load controller unless it is considerably oversized for the amount of dumping you'll be doing.

[la7qz]

Hi

This is hardly going to be an issue with a 1W indicator lamp in parallel with the dump load.

Owen