alternators and regulators

[ianj99]

200w of solar will deliver around 15 amps but only from about 10 am to about 5 in summer so you would be ok then.

The challenge of running a big engine lightly loaded for long periods to just charge the batteries is too risky. I'm with the suggestion of fitting a generator. In fact then you could do away with the solar and just drive your current shore power charger and the laptop off 220v

I agree. I've concluded that if fitting a substantially larger alternator leads to reliability problems with belts and bearings then its not worth it. Relying on the main engine as the only source of power is risky anyway as it can breakdown for numerous reasons in addition to the side effects of charging system upgrade. (advancing years = less risk adverse attitude!)
The only reason I would fit massive battery capacity would be if it was enough to last until the next shorepower outlet with minimal recharging en route.

 

[pvb]

The only reason I would fit massive battery capacity would be if it was enough to last until the next shorepower outlet with minimal recharging en route.

Increasing the battery capacity is one of the easiest and most cost-effective ways of enhancing a boat's electrical capability. Large battery banks suffer a lower percentage discharge for a given use, so the batteries last longer. Large battery banks also accept charge at a greater rate, so can take full advantage of the ability of a decent alternator with a smart regulator to restore amp-hours quickly.

 

[ianj99]

Cant seem to get any info, have tried.
Are the sterling alternators insulated return (-) or case return, I need insulated return. Proper marine engines.

I have a A127 70 amp alternator, which I converted to insulated return. However this meant removing the regulator innards leaving the Sterling Digital regulator to do all the work. Sterling said this would work, however its been troublesome - the regulator keeps shutting down (all leds flashing - overvoltage) regardless of the state of charge of the batteries so not due to voltage drop in the alternator wiring.

However I found this replacement regulator: http://www.ebay.co.uk/itm/A127-ALTERNATOR-REGULATOR-BRUSH-SET-FITS-PERKINS-SABRE-/250877089269

You can see that it also converts the regulator to insulated return but you still have to insulate the main negative output from the alternator body with insulating bushes (available from RSWWW.com). (I will document this stage so it becomes cheap and easy to convert a neg earth A127 type to insulated return)

I will install the enw regulator and see if the Sterling behaves. I also plan on doing a comparison between the standard and Sterling reg over the winter in respect of charging current and time to reach 13.8v in bulk mode.

Ian

 

[temptress]

...

Balmar make some of the best kit - yes its expensive but it does what it says on the tin. Similar to the Prestolite I believe but they are hot rated for continuous heavy duty use, dual fans, high temperature diodes - engineered to do a better job.

I struggled with the same issues for a few years and after trying various VSR/Charge regulators/Alternator managers I finally settled on twin alternators. The normal engine 60Amp alternator is used to charge the engine battery and I fitted a standalone Balmar 160amp alternator on its own dedicated dual pulleys (2 belts) to charge the Domestics. I also have wind and 200w of solar (planing to add another 100w of solar as soon as finances allow). I can get the batteries (100ah and 540ah) to 100% charge with this setup.

 

[ianj99]

Increasing the battery capacity is one of the easiest and most cost-effective ways of enhancing a boat's electrical capability. Large battery banks suffer a lower percentage discharge for a given use, so the batteries last longer. Large battery banks also accept charge at a greater rate, so can take full advantage of the ability of a decent alternator with a smart regulator to restore amp-hours quickly.

Therein lies the mistake many a boat owner makes. I.e. fitting larger batteries without thought to how they intend to charge them.
I think you need to take a holistic approach and look at your power requirements in terms of amp hours, charging system(s), typical engine running time if this is the sole charging source not to mention costs of battery and charging system upgrade.
Ian

 

[ianj99]

I struggled with the same issues for a few years and after trying various VSR/Charge regulators/Alternator managers I finally settled on twin alternators. The normal engine 60Amp alternator is used to charge the engine battery and I fitted a standalone Balmar 160amp alternator on its own dedicated dual pulleys (2 belts) to charge the Domestics. I also have wind and 200w of solar (planing to add another 100w of solar as soon as finances allow). I can get the batteries (100ah and 540ah) to 100% charge with this setup.

The perfect system: but I'd have a genny as backup as well.

 

[pvb]

Therein lies the mistake many a boat owner makes. I.e. fitting larger batteries without thought to how they intend to charge them.

Perhaps you missed the bit where I mentioned "the ability of a decent alternator with a smart regulator".

 

[ianj99]

Perhaps you missed the bit where I mentioned "the ability of a decent alternator with a smart regulator".

No I didn't. I was making the point that all too often this is not considered by many owners, hence the sheer number of threads on these forum relating to batteries and charging.
Ian

 

[noelex]

Part of the problem is your limit of not going below 70%.
You don't mention your actual usage, but with two fridges it sounds moderately high.
30% of your battery capacity gives you 162AHrs, but this is recharging to 100% which is going to be very very slow.
If you stop at 80% what're the charge rate drops off you have only 54AHrs to play with so you would need to charge probably 3 times a day.

With your current battery bank you need to expand your discharge down to around 50%. Using the 50-80% range.
Yes your batteries will have a shorter life, but you can take some consolation from the fact that you are operating them around the most economical (in terms of total battery cost) range.

Overall it will save you more money. Engine run time is expensive.

 

[temptress]

The perfect system: but I'd have a genny as backup as well.

I often consider a Genset (even a small petrol driven one) not found the need great enough to justify the expense yet. I also carry a spare 3rd alternator tucked away in the ships stores beside the spare autopilot and other things...

 

[pvb]

I also carry a spare 3rd alternator tucked away in the ships stores beside the spare autopilot and other things...

Spare engine???

 

[William_H]

Back to basics. An alternator's current rating is based on most optimistic conditions. It depends on alternator speed, temp (some get too hot at full power ) and the voltage it is expected to deliver. Certainly a bigger alternator will operate at a similar current at lower temperature and possibly will give more current at a given RPM.
All this assuming that the regulator is driving the alternator to full output and that the voltage at full output is high enough to shove the current into the batteries.
So firstly OP needs an amp meter to know exactly how much current his alternator is delivering. If this is near the rating then yes he needs a bigger alternator.
If it is lower than the rating (like half) the current may be limited by alternator RPM or the voltage output is not sufficiently high enough above the battery volts to induce charge.
Here is where the smart regulator can bump up the voltage by increasing field current and so may deliver more charge current. But still the current may be restricted by alternator RPM or battery charge state. (ie near fully charged)
If the alternator current is to be increased then it will take more horsepower which means usually you need better belt drive system.
So many factors involved. Certainly solar assist will help a lot. Another suggesting might be to fit a refrigeration compressor to the engine and a well insulated cold storage type freezer. Cold can be stored nearly as well as electricity. But of course can not be made from shore power.
So much depends on knowing what you present alternator is really doing before you jump into bigger alternator different belt drives new regulators etc. good luck olewill