Ample Power
- Thread starter Bill1565
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Is it the alternator that matters?
Didn't we have a discussion a short while ago about larger alternators being a waste because the batteries only charge up so fast? I want to say it was Roger or MS who had some calculations that basically showed a bigger alternator was just a waste of time as the batteries only charged so fast and no more.
Didn't we have a discussion a short while ago about larger alternators being a waste because the batteries only charge up so fast? I want to say it was Roger or MS who had some calculations that basically showed a bigger alternator was just a waste of time as the batteries only charged so fast and no more.
On a small wet cell bank yes, but as you get bigger and bigger the opposite happens. With AGM's you'll almost never get an alternator big enough to satisfy their hunger..
If Ample power specs are correct, I could get 100 amps near 1000 engine rpms. 100 amps will be about 20 % of my 500ish amp hour house bank. Should be fine for bulk phase recharging. Need to run engine at 26-2800 to get 100 amps from 100 amp max alternator. Can't afford either $ or space for enuff solar cells to generate 100 amps. I like quiet as much as the next person, which is why this alternator is so attractive.
I don't have a problem with a 100 amp alternator if there is a true need for it. For a boat with a large battery bank capacity which regularly may consume significant amount of amps between full recharges that may be the way to go but if you can provide your power needs with a smaller alternator that would be much preferable. A 100 amp or larger alternator will rob engine power and induce additional stress in the working parts of the engine. Besides the cost of the alternator you may require some modifications in the form of bracket, pulleys and belts. I would start with a power survey, then size the battery bank, work in my recharging options and finally decide on the size of the alternator. Once bulk rate charge is accomplished and you still have a few hours to go to attain full charge a 45 amp alternator will do just as good with less wear and tear.
Nigel Calder in his Systems Book provides pictures of the innards of a diesel engine that is all carboned up from running many hours with only a small alternator for a load (recharging batteries while at anchor). If your battery bank is more than 4 times the output of your current alternator and you spend a lot of time running your engine at anchor to recharge your batteries, you would do well to install a high-output alternator. The money you save in engine maintenace costs will pay for the alternator in the long run.
Some more info
For those of us who have been following alternators and power requirements for quite some time, the HP used by an alternator, regardless of what size the alternator may be, is based on the energy the alternator puts out. That amount is determined by the load imposed by the regulator and the acceptance of the battery bank. Most 400 ah house banks, even if reasonably discharged, won't require more than 50 to 60 A based on the battery acceptance. Therefore, even our 100A alternator on our 360 ah house bank when depleted overnight ot below the 85% charge level will only put out 50 or 60 A upon startup based on the bank acceptance. We have also discussed many times that a 100A alternator will have to work less than a 60A alternator to provide for this load. Accordingly, then, the larger alternator draws no more power from an engine for that same load, but may last longer because it is not working up to its total capacity. Running a 30 or 20 hp diesel engine at low rpms to ONLY recharge banks has always been know to be eventually damaging to the engine. Use your engine to charge your house bank when the engine is used to propel the boat. Use another source, like solar, to charge the banks instead of just the engine. For most of us weekend warriors, the simplest answer to this is to install as large a house bank as you can (400 ah if you have a fridge) and you can sit for two nights at anchor before you HAVE to start your engine for DC power. Then you motor home and plug in. Each boat gets used differently, of course, but those are the basics. Staying plugged in all week isn't good for you batteries, but neither is leaving the boat unplugged with partially discharged batteries either. Again, a simpler solution is solar: not keeping the boat plugged in helps the batteries (unless you have a charger that'll turn itself off when the bank is full) and avoids potential damaging from bad dock wiring or lightning. A boat is a compromise, but basic battery technology and battery charging is not, related specifically to alternator charging.
For those of us who have been following alternators and power requirements for quite some time, the HP used by an alternator, regardless of what size the alternator may be, is based on the energy the alternator puts out. That amount is determined by the load imposed by the regulator and the acceptance of the battery bank. Most 400 ah house banks, even if reasonably discharged, won't require more than 50 to 60 A based on the battery acceptance. Therefore, even our 100A alternator on our 360 ah house bank when depleted overnight ot below the 85% charge level will only put out 50 or 60 A upon startup based on the bank acceptance. We have also discussed many times that a 100A alternator will have to work less than a 60A alternator to provide for this load. Accordingly, then, the larger alternator draws no more power from an engine for that same load, but may last longer because it is not working up to its total capacity. Running a 30 or 20 hp diesel engine at low rpms to ONLY recharge banks has always been know to be eventually damaging to the engine. Use your engine to charge your house bank when the engine is used to propel the boat. Use another source, like solar, to charge the banks instead of just the engine. For most of us weekend warriors, the simplest answer to this is to install as large a house bank as you can (400 ah if you have a fridge) and you can sit for two nights at anchor before you HAVE to start your engine for DC power. Then you motor home and plug in. Each boat gets used differently, of course, but those are the basics. Staying plugged in all week isn't good for you batteries, but neither is leaving the boat unplugged with partially discharged batteries either. Again, a simpler solution is solar: not keeping the boat plugged in helps the batteries (unless you have a charger that'll turn itself off when the bank is full) and avoids potential damaging from bad dock wiring or lightning. A boat is a compromise, but basic battery technology and battery charging is not, related specifically to alternator charging.
Good summary, Stu.
A good smart regulator connected to the alternator will also help speed the charging process by raising the output voltage of the alternator to increase the current going into the batteries during the bulk charging stage.
For those with a low-hp engine, consider putting a switch in the alternator field circuit to remove the alternator load during emergency situations.
A good smart regulator connected to the alternator will also help speed the charging process by raising the output voltage of the alternator to increase the current going into the batteries during the bulk charging stage.
For those with a low-hp engine, consider putting a switch in the alternator field circuit to remove the alternator load during emergency situations.
From Balmar:
What horsepower load will I put on my engine with a new alternator?
Typically, when an alternator is working at full output, it will require approximately one horsepower for every 25 amps it produces. As such, a 100-amp high-output alternator will require up to four horsepower to operate.
From the engineering books: one hp equals 760 watts. 100 amps times 12 volts equals 1200 watts. Balmar alternators convert only 40 percent of the energy in to energy out?
edit to correct arithmatic.
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