Mahe 36: Air Conditioning

[Michelhhhebert]

Hi Roetter, 700 ah LiFePo? Are these not very expensive? And do you have a proper charger 15.4 v? I do not have experience with these... You must have compared with gel... Could you comment your decision please?

[roetter]

Originally Posted by Michelhhhebert

Hi Roetter, 700 ah LiFePo? Are these not very expensive? And do you have a proper charger 15.4 v? I do not have experience with these... You must have compared with gel... Could you comment your decision please?

There is lots to read in the threads about LiFePo batteries. Too much to read and too much theory for most. Here is a good condensed form of it form a cruiser.
http://www.cruisersforum.com/forums/...batteries8.pdf



But here my thoughts on this.
I had 840Ah lead acid on my cat. No air conditioning, but a cappuccino machine, a toaster and electric winches. When the batteries were not really full, then just the load from the cappuccino maker would cause a low voltage alarm when sailing. Autopilot, instruments, fridges would use 20-30A depending on waves and wind. The cappuccino maker then added another 150A. If then someone would just use an electric winch for a second, the voltage dropped to 10V.

Using the Honda 2000i or engine alternator would not allow to fill the batteries past 80% , as the amps going in dropped to 30 or less, so very inefficient and time consuming.

Balqon has 700 Ah LiFePo cells for $560 each, so less than $2300 for the batteries. There are guys that charge at much lower voltage than the 15.4V. If you are happy with 95% full than the 14V or so from a regular lead acid charger will be fine. These batteries do not suffer from under charge as lead acids do.

Gel bat cost $300 for 100 Ah. I would need at least 1400 Ah to get the same usable capacity with longer charge and less performance at high draws and this would cost $4200 for the batteries, that would last less.

Advantages:
- drawing 300A will not drop the voltage by more than 0.1 or 0.2 V
- you can charge right up to full at 200A or more if you have the means. The new cat will have 125 alternators on each engine. So getting out of a marina or anchorage and running the engines just for a short time will put a lot of juice into the batteries.
- 2000 charge/discharge cycles.

I hope this answers your question.

[Michelhhhebert]

Thank you for your reply, i will consider this when i need to change my batteries in the next few years, my batts are 5 years old and doing fine, i paid 2.00$ an amp for my gels, but otherwise your idea seems valid. Thanks again.

[DtM]

Thank you Roetter for your analysis. Very helpful in making decisions.

[rgary]

Scott,

I just joined the forum this week, my wife and I have had Bluebird for a little over a year, we are slowly adding equipment in preparation for a more active cruising lifestyle. Our Mahe has the reverse cycle installation similar to Clipperton, and we are looking to power at least one of the units away from the dock. Your install of the NexGen sounds like a good plan for us - do you have anything specific to share on the starboard engine compartment install, photos, who did the work, accessibility for maintenance, etc. We have twin Volvo 30HP in the boat.

Currently in the Chesapeake Bay area.

Gary

[Scott730]

Gary
There is just enough room to build a platform and mount the 3.5 Next Gen unit with sound enclosure (I have a 1/2" to spare). This is with the 20 hp Volvo. Not much room for anything else, including my big butt. The unit is 200lbs with the enclosure. Next Gen can help you locate a local installer, they did for me.
All this talk about batteries vs generator to run AC. I will make one more comment. We are talking about a Catamaran, which is weight sensitive, a 1000 amphours is almost 700lbs!!! plus solar panels, charge controllers.... Think about it.

To all on this forum, I have sold OceanView and she now cruises the Chesapeake Bay. I wish her and her new owner following seas and smooth sailing.

Scott

[Pacey16]

After arriving in Phucket at the height of Summer i was forced to install air-conditioning in my 52ft ben Lexcen ex race boat to cool my cabin just to be able to sleep well.
The problems I had were I had not enough bilge space to install the unit under the bunk as normal and I had no generator.
I sourced a 9,000 BTU seawater cooled marine unit and installed it in the large cockpit under the BBQ table, It is well ducted to the adjacent cabin and I had made a fibreglass cover which serves as a foot brace and step also.
To power it i purchased a Honda 2000 inverter generator. As the start up amps is too high for the geny I had a soft start box installed, this I think consists basically of 3 capacitors which works well and the start up is only a couple of amps above operating current.
The only thing I would do differently would be to use a 7,000BTU instead as the cabin is quit small and the 9,000BTU cycles on and off and strains the geny a bit.
I must say I normally only run the A/C in the marina but its good to have on those really hot humid nights on the hook when there is no breeze and you are willing to put up with the hum of the geny and the disapproval of any neighbors..
Hope this is of interest.

[1rkghost]

Looking to install ac on our mahe any recommendations on ac mechanics in west florida?

[Seastream]

We just had a 16K BTU installed under the port settee running to four vents. Install performed by Beard Marine; we're well pleased with the work. Unfortunately they're located in Ft. Lauderdale & Palm Beach, FL. Although they'd likely travel to you I don't know if that'd work for you.

[a64pilot]

Installing an AC is very simple, I even installed one myself under our berth and with the mattress as sound insulation, you only hear the air coming out of the vents.
Hardest part of installing an AC is running the vents.
Actually finished the install yesterday, I had been running it off the engine's thru-hull, but when I had the boat out for a bottom job I installed two more thru-hulls, one for the AC.


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[1rkghost]

Do you have any pics of your set up? Also are you running off a genset?

[1rkghost]

Does anyone run their ac on batteries alone? I have 4 mastervolt 260a/h agm batteries in house bank and was wondering if this would be enough to run ac for 4 or 5 hours while on the hook for really hot nights. Really only need ac for sleeping.

[ShaktisBoy]

Check out zrd.com



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[ShaktisBoy]

I'm sorry if this post is too long but I think it may shed some light on the subject for the OP.

My cat a 2007 Leopard 40 is setup to run air conditioning on batteries alone. We have a 900 AH lifeline AGM housebank. AIMs power 4000 watt pure sine industrial inverter with a max surge rating for 20 seconds of 12000 watts. My Northern Lights 6kw genset bit the dust last summer and I had been contemplating going DC anyway if in fact I had to replace the genset so after a ton of research I decided to give it a shot. One of my initial contacts was John from ZRD out of Stuart Florida who I had several lively discussions with during the last few Miami boat shows. John had insisted that not only is it possible but if done correctly this type of system would actually pay for itself in fuel and maintenance savings in a short time. He had a ton of charts and graphs to backup his claim and I was impressed. There is at least one yacht manufacturer installing his DC systems as options on their yachts and having great sucess. I ultimately went with the AquaMarine AquaGen because that system is very similar to ZRDs but also has designed in a HP pump for a water maker and if the need arises a second compressor for refrigeration. Of course you cant run all at once so the HP pump and compressor are on clutches for the times the Generator is working real hard to charge the batteries. That unit can be seen here,

http://aquamarineinc.net/minigen.htmlI

The good:

Anyway we replaced the 445 pound Northern lights M673L3 genset with a 140 pound AquaGen and wired the boat for DC charging which makes a ton of sense in my mind do to the inefficiency of converting ac to dc for charging and so far I am mostly happy with the results but it is not perfect. Here is my take on the good and the bad of our new system starting with the positive stuff. The Northern lights took up a large amount of storage space in our port side forward locker, so much so that we had very little room for anything else beyond a couple of fenders. Oil changes and any maintenance on the NorthernLights to the starter, heat exchanger or simple water pump impeller changes were extremely difficult and had to be done mostly by feel. Now With the AquaGen we have gained that huge space back which allows us to keep all of our dive gear, 5 tanks, 5 BCs and all the other scuba paraphernalia one could want as well as the Aquagen in that same space. When Its time for MX on the Aquagen its very easy to accomplish do to the small size and easy access without all of the sound shielding to dig through of the previous Northern Lights. I empty the dive gear step inside and sit next to the unit with access to all 4 sides. The AquaGen recharges our House Battery Bank from 12.2 volts back to 90% 12.85 volts or there abouts state of charge in about an hour. The AquaGen literally sips fuel using about .3 of a quart at full RPM 2800 which only has to be maintained for only a short time maybe 20 minutes. Once the amps drop to 90 we can throttle the unit back to 2200 for another 20 minutes or so. At 60 amps going into the house bank we can further reduce the rpm to 1800 or so for the last 20 minutes. Once the amps drop below 10 we shut the unit down and we are good for the rest of the day. The NorthernLights took forever to get the house battery bank charged even with a state of the art Magnum 2800 watt inverter. Basically as the amp acceptance rate drops the genset still runs at its governed 1800 rpm which result in the engine being to lightly loaded causing black soot all over the side of the boat and the exaust elbow to need regular maintenance to clean out the build ups. A real P.I.T.A!


Now for the not so good

Running the air conditioners is not as simple as just turning them on like we did with the NorthernLights running.
If the boat is hot it takes quite a while to cool down so we have to plan for the need for cooling and it much more involved than before.

Here is how we do it.

Step 1 about an hour before we want to run the air conditioners we complete a charge cycle.
Step 2 once the charge cycle is complete we leave the AquaGen running and turn on a single 16k btu unit and the genset is now basically keeping the batteries topped off while the initial cool down takes place. Our AquaGen puts out 150 amps continuous and our CruiseAirs need about 10.5 amps AC each which equates to 105 amps DC per unit at full locked rotor amps. Thats a huge power draw hence starting with a full battery bank so the generator is not trying to fill up a rapidly depleting battery bank.
Step3 once the first unit has cooled the worst of the heat we start the second 16kbtu air conditioner and set it about 1 degree higher than the 1st one so that they both don't cycle on at the same time.

Once both units are cycling on and off we can turn off the genset and the air conditioners will run for about 4 hours before we need to charge the batteries again. If its just myself and my wife onboard we really only need to run one unit so we can get about double the runtime between charge.

There are a couple more items I'm not really excited about in the system we went with. One is the unit comes standard with a 12 volt lift pump for cooling water flow to the fresh water heat exchanger and the wet exhaust. If it quits we have no way of knowing until I install a sensor in the raw water line. It is on my list of things to do but for now I check under the bridge deck for water flow from the unit when we start it. Another downside is we can no longer heat water electrically unless I tie into the inverter which I don't really want to do do to the complex wiring that will have to be done. The last item is subjective and we knew full well going in that this is a hands on system. We have to control the rpm manually via a remote throttle and pay attention to what the amps are doing in order to achieve the efficiencies John from ZRD was talking about, on the one hand you have to pay attention but on the other it really makes you aware of how much energy you are using where as the NorthernLights you simply turn it on and forget it.

Hope this helps.



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[RKsailsolo]

That was a huge help. Great detail. Thanks.

Sounds like you don't regret the change but a few areas that would disappoint are where John from ZRD could have been more forthcoming.

So what I am learning is that there are no simple AC solutions when it comes to managing power supplies away from the dock. Does anyone have a better experience?