Is 3.5kw Generator OK for a 16,000btu AC?

[cat man do]

Originally Posted by OceanPlanet

For cruising with air conditioning and other AC loads, another way to approach all these issues is to use a DC genset (like the new Polar Power Volvo-powered units)

DC Generators & Alternators

Volvo? Where?

I see Kawasaki, kubota, Lombardini, Faryman but no Volvo

I also see prices 3 x more than a Honda

[Talbot]

The Marine Air 16,000 btu system http://www.marineair.com/pdfs/L-2125.pdf draws 1.9 kva when running. I would expect a 3.5 AC generator to be able to drive that, but probably not start it. Therefore you need a good sized inverter that will parrallel with the generator to be able to suck more power from the batteries just during start up loads. This demands a victron, or something of similar capability

[Meridian]

Originally Posted by Chief Engineer

Generators are white noise to me....

I would rather listen to that than slapping halyards, steel drum music, or drunks

Chief...excellent point.
We've anchored out over 500 nights in the last 2 years. In popular spots, along the "coconut milk run". Never once heard someone else's genset. Those that seem permanently bothered by gensets are, IMO, just that...permanently bothered.
I literally can't hear my own genset when 15 feet from the boat. Anchor within 15 feet of me, and you'll have bigger problems than my sound signature.
John

[OceanPlanet]

Originally Posted by cat man do

DC Generators & Alternators

Volvo? Where?

I see Kawasaki, kubota, Lombardini, Faryman but no Volvo

I also see prices 3 x more than a Honda

Just sent you a PM...the Volvo-powered units are not yet up on the PP website, but I have detailed information on them in pdf format for anyone that wants to see.

Full disclosure: I sell LiFePO4 batteries, and have been talking to PP their latest units. Nearly all other genset providers out there are still beholden to AC, which makes it problematic to charge the batteries fast enough. So I connected with PP to see what they're up to.

LiFePO4 batteries (Lithium Iron Phosphate) can easily take charge at 3C: so if you have a 100AH x 48V system you can safely charge it at 300 amps(!). That's equal to 1200 amps at 12V...

[Highlander40]

Ocean Planet,
My house bank is about 400 AH. four Lifeline AGM's
Last time replacement cost $1000. plus shipping.
Not taking into account conversion costs-- whats the lithium equivilant?

I'm guessing a factor of 3 or 4 X

[bobfnbw]

Originally Posted by OceanPlanet

I thought to chime in here regarding the AC generator/air conditioning/noise/cruising philosophy issues.

The improvements in batteries such as Odyssey thin-plate and especially LiFePO4 (Genasun, RaceCell, Mastervolt, Valence, etc.), along with the highly efficient inverters available, has really opened up more options.

For cruising with air conditioning and other AC loads, another way to approach all these issues is to use a DC genset (like the new Polar Power Volvo-powered units) along with high-efficiency batteries to dramatically shorten the charging times.

With the genset running at optimum efficiency (always charging at full power, once warmed up) the overall fuel consumption is greatly reduced along with emissions/noise/charging times.

Yes, with fast DC charging you will most likely go with a higher-voltage charging/battery system to avoid very large breakers and wiring. However, stepping down to 12V house loads (if you need to) from a 24V or 48V bank is no longer a big deal, using DC/DC converters such as Victron's, nor is running all your AC loads with inverters (also Victron, etc.).

With a properly designed system, you could run your AC loads all night (or at least most of it) without the generator turning on until the morning. Your anchorage friends will love you...;-)

Yes, the initial costs of the system may be higher but over the long haul with the increased battery cycle life of LiFePO4, less fuel used, and simply a more pleasurable experience (genset off most of the time) makes it worth considering. The whole game changes when you can charge your batteries at 10kW (with a 10kW genset).

Ahem...did I mention that the LiFePO4 batteries would weigh roughly 1/4-1/3 of the weight of lead/gel/agm for the same useable AH's?

Bruce

Bruce, do you have any info on the mastervolt 3.5kw genset in 120v ac 60 htz? like how much does one cost, noise ( runs at 3K rpm etc?) thanks

[OceanPlanet]

Not a bad guess. Of course it depends on how you size the battery system. Your 400AH agm's have a theoretical "useable" discharge range to 50% of capacity if you want to maximize their life. However, due the to slow charging to get from 20% discharged to full, you probably (or usually) really only use the range between 20% and 50% discharged. Which leaves only about 120AH available (30% of 400AH) in the fast (for lead, anyway) charging range.

To acheive the same useable range with a Genasun system you would only need a 200AH total capacity bank. This is because the LiFePO4 chemistry is rated to over 2000 cycles at an 80% discharge rate (even more if you discharge less than that, say 70%). To give a fair comparison, let's say that you will typically charge the LiFePO4 bank to just 10% discharged, and discharge to 75% or so...this will give you a solid useable range of 65%, or 130AH.

The weight of a Genasun 200AH system is 31kg, or 68.2lbs. Compare that to the AGM bank weight...

Ok...the prices: The retail price for the dual bank (2 x 100AH) system complete with dual BMS controllers, and including charge & discharge contactors (that can completely isolate the system to prevent accidental over-discharging or over-charging) is $6000. Yep, I know that's a lot. Of course one has to consider the the increased cycle life, greatly reduced weight, and more efficient charging to make the long-range decision.

For the RaceCell brand, I would probably spec out a 3P x 90AH for 270AH total capacity for a retail of $4500 (3 x $1500). The RaceCell BMS has a "top-off" balancing capability, somewhat limited overcharge protection, and does NOT have the charge/discharge contactors, so it is not as advanced as the Genasun. That is why I'd use a bit bigger bank making it easier to stay away from the "bottom" of the range.

For cruisers that carefully monitor their batteries and have a good monitor system with a low-voltage alarm, and want to save some $ (liveaboards?), then the RaceCell would be worth considering. On the other hand, once you are spending that much it is nice to have the complete protection offered by the Genasun.

Bruce

[Lost Horizons]

Apparently, $6000 is a little out of range for most people. I paid less than $1000 for 3 Odyssey 100 A*h batteries that also can be discharged down to 20% and quickly recharged back to 95%. Looks like it is the best techlogy in terms of price/performance available today. Properly placed, they also help improving ballast-to-displacement ratio...

[OceanPlanet]

Originally Posted by bobfnbw

Bruce, do you have any info on the mastervolt 3.5kw genset in 120v ac 60 htz? like how much does one cost, noise ( runs at 3K rpm etc?) thanks

For AC generators, including the MV 3.5, I highly recommend Nigel Calder's article about Victron's generator testing program (see Professional Boatbuilder June/July 2008). You have to do their "online subscription" to view it:
Professional BoatBuilder - June/July 2008

Or, check out the links on the Victron page about the testing program:
Marine Generator Test - Victron Energy

In these tests, the MV Whispergen 3.5 scored rather poorly against other units in fuel consumption/kW and noise.

Fyi, DC generators were not included in those articles, but Victron has indeed tested Polar Power units, which scored consistently 20% better on fuel consumption/kW than the best performing of any of the AC gensets.

[OceanPlanet]

Originally Posted by Lost Horizons

Apparently, $6000 is a little out of range for most people. I paid less than $1000 for 3 Odyssey 100 A*h batteries that also can be discharged down to 20% and quickly recharged back to 95%. Looks like it is the best techlogy in terms of price/performance available today. Properly placed, they also help improving ballast-to-displacement ratio...

No doubt the Odyssey thin-plate batteries are a great product. Where weight is not a concern they are a great deal.

Keep in mind they are still more than twice the weight of LiFePO4 for the same total capacity, and at 80% discharge rated for only 1/4 of the cycle life (500 vs. >2000).

Also, for high-discharge rate applications, the "Peukert's exponent" characteristics of all lead batteries means you get less than the rated AH's at high discharge rates. With LiFePO4 you get pretty much the same at high or low discharge rates. Of course, this doesn't mean much if one never needs the high rate, which is often the case for many boats. However, with big loads such as air conditioning, etc, the ability of LiFePO4 to take the high rates and provide the rated AH's gives options for system design that may have been impractical with lead/gel/agm.

Don't be me wrong. I know that the lithium batteries are not for everyone. Just thought to put them out there, along with fast DC charging as something to consider.

B

[cat man do]

Originally Posted by OceanPlanet

Just sent you a PM....

Never received it

[cat man do]

Originally Posted by OceanPlanet

Ok...the prices: The retail price for the dual bank (2 x 100AH) system complete with dual BMS controllers, and including charge & discharge contactors (that can completely isolate the system to prevent accidental over-discharging or over-charging) is $6000. Yep, I know that's a lot. Of course one has to consider the the increased cycle life, greatly reduced weight, and more efficient charging to make the long-range decision.

Have these things been around long enough to know if they really do have a longer life?

[Zydeco]

The Marine Air 16,000 btu system http://www.marineair.com/pdfs/L-2125.pdf draws 1.9 kva when running. I would expect a 3.5 AC generator to be able to drive that, but probably not start it. Therefore you need a good sized inverter that will parrallel with the generator to be able to suck more power from the batteries just during start up loads. This demands a victron, or something of similar capability

Disclaimer: My knowledge of A/C is limited to turning it on and checking for water flow. With that in mind:

Dometic/Marine Air Systems sells a "soft start" device that supposedly reduces the surge in amps necessary to start the compressor:

SmartStart Reduces Startup Surge - Dometic

Again, I know next to nothing about air conditioning, but I think "locked rotor amps" is the amount of amps normally necessary to start the compressor. I don't know what A/C unit you have installed on your boat, but the specs for a Marine Air Systems 16,000 BTU Vector Compact Unit shows a locked rotor amps of 59:

http://www.marineair.com/pdfs/L-2262.pdf

Maybe the soft start device would get this down to where your 3.5 kva generator could start and run the A/C. Seems like a good question to ask someone at Dometic.

BTW - Our Honda EU2000i generator can start and run our old Marine Air Systems 9,000 btu unit. The unit has some sort of device installed on it that may be a "soft start" type device. Whatever is, it came with the boat many moons ago.

[OceanPlanet]

Originally Posted by cat man do

Never received it

Just tried again...

[OceanPlanet]

Originally Posted by cat man do

Have these things been around long enough to know if they really do have a longer life?

Although they are relatively new to the marine world, the LFP/LiFePO4 chemistry is in very wide use in electric cars, bikes, scooters, military applications, etc. The cycle life has certainly been verified, and the completely sealed construction and stable chemistry bodes well for extremely long use in the marine environment.

However, this as particular chemistry was only invented in 1996, an absolute proven end of the lifespan is impossible to say!

Here is an excerpt from the zillions of articles out there on the net:

"Dr. John Goodenough and his team at University of Texas patented as potential cathode material LiFePO4 as a potential cathode in 1996. It is a very stable material due to the covalent P-O bonding which stabilize the fully charged cathode versus O2 release. scientists have developed the LiFePO4 battery using lithium iron phosphate as cathode to answer concerns in the battery for Electric Vehicles and other battery useages..

Safety of LiFePO4
The safety characteristics inherent to LiFePo4 technology result from the incorporation of phosphates as the cathode material. Phosphates are extremely stable in overcharge or short circuit conditions and have the ability to withstand high temperatures without decomposing. When abuse does occur, phosphates are not prone to thermal runaway and will not burn. As a result, LiFePo4 technology possesses safety characteristics that are fundamentally superior to those of Lithium-ion batteries made with other cathode materials.

LiFePo4 technology does not contain any heavy metals and does not exhibit the "memory effect" of Nickel-Cadmium and Nickel-metal Hydride solutions. LiFePo4 technology demonstrates excellent shelf life, long cycle life and is maintenance free.