AC alternator vs DC (12 / 24) volt alternator

[boater123]

Hi everyone,

 

Looking towards powering a continuously cruising wide beam and have been offered differing opinions about what alternators to use, AC/travel power set up or DC 12/24V.

 

Plan is to have the following appliances; washing machine, dish washer, microwave. (not to be run all at the same time!). All run through a 3KW victron inverter (quattro if ac alternator, multiplus if dc), currently have one alternator set up for the engine battery on a 52HP canal line.

 

I'd appreciate if those with experience could offer advice to the pros and cons of each set up (AC or DC)

Specifically

 

1) cost - AC vs DC and reliability of buying second hand / reconditioned?

 

2) Ease of installation - DC seems to require more equipment and headaches such as connecting 24V alternator to 12V system, am I correct in thinking this?

 

3) Engine Revs - I've noticed on some large 12V alternators require engine revs @4000+ to get higher amps out of them, rather have the engine idle. Is this the main advantage of AC alternators?

 

I've read previous threads but was hoping we could directly compare ac / dc, not looking to get too technical (that will come later...) but would appreciate any ideas or warnings before taking the plunge with one system or the other.

 

Thanks,

 

Adam

[ditchcrawler]

I don't think you will get much from the Travelpower at tickover

[OldGoat]

boater123, on 12 Jul 2016 - 11:59 AM, said:

Hi everyone,

 

Looking towards powering a continuously cruising wide beam and have been offered differing opinions about what alternators to use, AC/travel power set up or DC 12/24V.

 

Plan is to have the following appliances; washing machine, dish washer, microwave. (not to be run all at the same time!). All run through a 3KW victron inverter (quattro if ac alternator, multiplus if dc), currently have one alternator set up for the engine battery on a 52HP canal line.

 

If you're going to have that much equipment in regular use - I'd go for either a Travel Power OR a separate generator - you've got enough room in a wide beam

I'd appreciate if those with experience could offer advice to the pros and cons of each set up (AC or DC)

Specifically

 

1) cost - AC vs DC and reliability of buying second hand / reconditioned?

Don't think you'll find a lot od used kit available - if cost is a consideration, then cut down on the power hungry kit

 

2) Ease of installation - DC seems to require more equipment and headaches such as connecting 24V alternator to 12V system, am I correct in thinking this?

 

3) Engine Revs - I've noticed on some large 12V alternators require engine revs @4000+ to get higher amps out of them, rather have the engine idle. Is this the main advantage of AC alternators?

No - it's the alternator that has to turn at 4-6K rpm - you size pulleys so that the engine runs NOT at tickover, but at a reasonable speed, say 1500 - 1800 rpm

 

I've read previous threads but was hoping we could directly compare ac / dc, not looking to get too technical (that will come later...) but would appreciate any ideas or warnings before taking the plunge with one system or the other.

 

Thanks,

 

Adam

 

See above and -

For convenience I'd go for -

a 24V system with a good sized battery bank - say 800 Ah - for those occasions when your use of mains power is short.

A separate 1500 rpm generator or travel power unit on the engine. (3,000 genny is just too noisy and perhaps less reliable).

For those DC appliances that are only available in 12V then I'd 'take a tap in the battery bank and if necessary split the load

(0 -12 V and 12-24V)

24V alternators are generally more reliable and less expensive for a given power output than a 12V version

The same applies to 24V equipment.

 

This general subject has been well aired here this year - it might be profitable to look at some of those threads.

You will also find a lot of disagreement.

It's what I did on my boat and I've not regretted it in 16 years.

[peterboat]

I have the large 12 volt alternator and the pure sine wave inverter with 1500ah of full traction batteries. I also have 900 watts of flexi solar panels. Same as you I have a dishwasher, autowasher, kettle, coffee maker etc etc the system works.

I also have a 12 volt dc wispergen gennie which charges batteries and runs central heating/hot water. I did think of travel power but it seemed expensive for what it is.

I would go down the 24 volt route if I was starting afresh but as I bought the boat with 12 volts already on it, it was more expense for little gain

[BEngo]

You write AC or DC. It is not one or the other. If the engine or a genny os not going to run continiously you have to store power.

That means a battery.

If you want 250 V on smallish quantity then an inverter will be good. If you want a lot of 240 then a travelpower or built-in genny is good. An inverteris then handy for quiethours power.

You should do Two power audits- battery and mains. That will point you to how mich you need and thus the best/cheapest way of meeting the needs.

 

N

 

You should d

[by'eck]

240 volt AC production is more efficient than the equivalent power from a 12 or 24 vot DC system. However if you already have a large 12 or 24 volt DC output alternator and matching large pure sinewave inverter, it may be more cost effective to stick with those.

 

The TravelPower or similar Dynawatt provide a relatively large amount (3-4 kW) of engine driven AC power directy to your mains distribution system using a compact alternator, but the outlay is quite high.

 

Sticking to an engine driven DC system which you probably already have, has the advantage of allowing any shortfall in DC current needed to drive your inverter to be provided by the batteries. It also means that high power mains devices don't require the engine necessarily running well above idle as the TravelPower might, and then there is the afore mentioned cost saving.

 

I went for the DC option with two alternators and a 3200 watt PSW Combi. Typically I run the washing machine when tackling a flight of locks, where the engine is at close to idle for much of the time. The alternators comfortably keep up with demand leaving the battery bank still fully charged at the end of a cycle.