Cutwater 30 Alternator

[aroos]

I have a new Cutwater 30 sedan without a generator. We don't have air conditioning. We like to spend time several days at a time at anchor and I'm wondering how much our alternator puts back into our house batteries when running at idling speed. In other words, is it practical to use the engine at idle speeds as a generator? If not, can I achieve my goal by using throttle only to increase the rpms? Noise (in a quiet anchorage) and fuel consumption would be limiting factors.

PS At idling speed, how long would it take to heat our hot water tank?

 

[SGIDAVE]

I have a new Cutwater 30 sedan without a generator. We don't have air conditioning. We like to spend time several days at a time at anchor and I'm wondering how much our alternator puts back into our house batteries when running at idling speed. In other words, is it practical to use the engine at idle speeds as a generator? If not, can I achieve my goal by using throttle only to increase the rpms? Noise (in a quiet anchorage) and fuel consumption would be limiting factors.

PS At idling speed, how long would it take to heat our hot water tank?

Hello Aroos,

I'm surprised you got no response when you posted this question earlier. It's uncharacteristic of this forum to miss something 🙂

Alternator output will be dependent upon the specs of the unit installed on your motor . Sorry Idon't have that info; I would guess that the rated output will be at least SOMEWHAT rpm-dependent, meaning, if the Alternator where rated for 80 AMPs, you wouldn't see full rated output untill you get well above idle speed.

Along the lines of IDLING your diesel for battery charging and hot water...the engine won't get very hot anytime soon at IDLE. Furthermore, it is BAD for diesels to be left idling. They do best when working at approx 80% of rated load AND at usual operating engine temps.

You are NOT the first to have this question/issue. My vague recollection was that a small genset is used (like Honda 2000 inverter generator) to recharge batteries and provide electricity to heat water. A genset like this stores easily but would require you to carry some gasoline.

In REALITY I don't know the degree of actual damage it causes your diesel to idle (or FAST IDLE) to give the results you are after. From a cost/benefit analysis, I'm not sure of how you could calculate the actual cost of using your diesel to charge batteries and produce hot water. Again, maybe other big-diesel owners can chime in here...

Fair winds,

/david

 

[walldog]

I believe that we had a 140 am alternator in our R27. I also thought that it would be more efficient to idle at anchor to recharge house batteries. It does work. However, there are some negatives that made me decide not to do it again. Our R27 had never developed the black sooty area on our dinghy that is common to a lot of Ranger Tugs. After enough idling to recharge the batteries once, we noticed a buildup of this soot on our dinghy. Also the general consensus of our group is that prolonged idling to not good for your main engine.

You should have enough battery capacity to spend a couple of nights on the hook without recharging. I assume you do have solar panels and at least 2 house batteries. If not consider adding a couple of more house batteries for longer stays. Some folks have added the thruster battery to to the house circuit for more capacity. If you can make two nights, maybe a short trip off the anchorage every third day will suffice.

We added the Cummings Onan generator to our R31 for this very reason. You may consider one of the Honda 2000s. I was at a dock with a couple of C-Dory's that had them and ran them during the day a bit. I did not find them excessively noisy or offensive.

 

[aroos]

Thanks for the responses. On the C30 we have 4 AGMs (each 110 amp hours) and the solar pannel. I will check on the alternator output. I wasn't considering idling to achieve a full recharge, just enough to get us through another day. Perhaps an hour or so. The portable generator is an option but that means carrying gas. When you did try idling to charge the batteries, do you have a sense how long it takes to get hot water? Thanks.

 

[walldog]

I do not remember about the hot water. I am sure it heated some, but we were on ultra conserve mode for water anyway. As David mentioned, it will only heat your water up to the temperature that the engine achieves. In the cool waters of BC, that may not be hot enough for a shower...grins.

 

[Bruce Moore]

Based on two cruises to Desolation Sound on our R-29, we were able to spend 2-3 nights in an anchorage without a generator. The hot water stayed reasonable warm - at least for a quick rinse on the swim grid. Once we get up there we turn the temp up on our auxiliary freezer and use it as a fridge. The solar panel keeps up with our core power requirements.

For really hot water (showers and/or dishes) we've had great success with solar shower bags.

Cheers,

Bruce

 

[aroos]

Thanks to all of you.