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 3/11 |
When my alternator failed last august (first day after I just bought it), I had it replaced with one similar to the one in place : 60 amp. I now read that standard one is 160 amp (is it?) What is the inconvenient of such an underpowered one and what would be the minimum acceptable? Preparing for next season, Mike Breakaway 30’ 92, Cummins 6BTA (Banks Powerpack Twin Ram) (stored for winter) | ||
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First Month Member 11/13 |
At the minimum, an alternator needs to be large enough to carry all the loads on the battery with a little left over for battery charging. Does the coach have a voltmeter? What does it read when you are driving? As long as your 60 amp alternator can carry the loads, the only inconvenience will be slower battery charging. . 84 30T PeeThirty-Something, 502 powered | |||
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12/12 |
At full charge rate, I've read where an alternator eats up about 1hp for every 25 amps, so ya don't want to over-size too much either.....On the flip side, an alternator working at lower rates of designed capacity will no doubt live longer. I'd think that the charge acceptance rate of the battery ought figure into your sizing calculations too...... | |||
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| First Month Member 11/13 |
An alternator absorbs crankshaft power in direct relation to its output current. The size of the alternator really doesn't enter into it, other than the flywheel effect of a physically larger alternator. Also, even if a larger alternator did have some flywheel effect, it would have no effect at steady RPMs, and only a minuscule effect on acceleration, since we accelerate fairly slowly, anyway. In many alternator series, the higher output versions simply have more windings in the stator, which does not rotate.
Yes. But this would be tricky to calculate. A real-life measurement would be very useful. Also, some of this depends on the usage. For example, a user who just drives to a plug-in site has different needs than a dry camper who depends on his engine alternator to charge batteries while driving. . 84 30T PeeThirty-Something, 502 powered | |||
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| 4/08 |
This should almost be under a heading of batteries. Anyway I have 4 T105s for house batteries. This is equal to 450 amp hours of battery battery power. Dropping them to 50% would be using 200 amp hours. Now I need to recharge them. I would take a 50 amp alternator running full out for 4 hours to recharge them. This is not going to happen as output drops as battery charge comes up. Even a 100 amp alternator could not recharge in 4 hours because of the tapering effect. This is the reason RV has high capacity alternators. '92 Barth Breakaway - 30' 5.9 Cummins (6B) 300+ HP 2000 Allison Front entrance | |||
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| 03/22 |
I also have 4 T105 batteries for the house system. When my OEM alternator bit the dust (I think it was rated at 100 amps) I replaced it with a 200 amp alternator, even with this size alternator, after a couple of days boondocking, it will take 4-6 hours driving to bring the batteries to 80-90% charge. The change required an alternator bracket change, a new tensioner, new belt all from Cummins. Never regretted this change. I use a lot of 12 volts in my activities. Ed 94 30' Breakaway #3864 30-BS-6B side entry New Cummins 5.9L, 375+ HP Allison 6 speed Spartan chassis K9DVC Tankless water heater | |||
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| 2/16 Captain Doom  |
My odd 6.5L TD has a stock 105 A alternator. But the point I want to make is that upping the alternator capacity means you'll have to replace the cables - both hot and ground. Rusty  "StaRV II"'94 28' Breakaway: MilSpec AMG 6.5L TD 230HP Nelson and Chester, not-spoiled Golden Retrievers Sometimes I think we're alone in the universe, and sometimes I think we're not. In either case the idea is quite staggering. - Arthur C. Clarke It was a woman who drove me to drink, and I've been searching thirty years to find her and thank her - W. C. Fields | |||
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| 03/22 |
Good suggestion, mine already had 2/0 cables from the alternator to the relays and then to the batteries. My original alternator did not have a ground lead but the new alternator had a stud for grounding and I added a 2/0 cable there to the ground AT the batteries. A bit redundant but was for some insurance. Ed 94 30' Breakaway #3864 30-BS-6B side entry New Cummins 5.9L, 375+ HP Allison 6 speed Spartan chassis K9DVC Tankless water heater | |||
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3/11 |
As a suggestion to consider the cables that are sold for primary battery connections, whether 2.0 or some other size are composed of stranded copper which vary in size. The cheaper cables have fewer strands and larger gauge wire. The better ones have more strands and smaller gauge. We have found that the best cables to use, even at a higher price, are welding cables. They are still 2 gauge but have hundreds of fine wire strands (the better to conduct electricity with a minimum of loss resistance). You can buy these at any welding shop and have terminals swaged on. If you know a welder who has some older perhaps damaged cables just cut out a good section and install them. They are not cheap but they are noticeably more efficient. To get an idea of losses on a standard cable just hold your hand around it after it has been charging a while. If it is hot to the touch you are losing significant voltage to your system. 1993 32' Regency Wide Body, 4 speed Allison Trans, Front Entry door, Diamond Plate aluminum roof & 1981 Euro 22' w Chevy 350 engine and TH 400 tranny | |||
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| First Month Member 11/13 |
DC current responds to the cross sectional area of the conductor, usually expressed in circular mils. The number of strands is not a consideration, but does become more important at much higher frequencies. (Or is that frequency?) That said, some of the cheaper wire is not accurately gauged, so can be undersized in relation to its marking. And, some of the cheaper cables are poorly crimped and have poor terminals. And, welding cable is great to work with, owing to its flexibility and the limpness of its insulation. . 84 30T PeeThirty-Something, 502 powered | |||
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DC current responds to the cross sectional area of the conductor, usually expressed in circular mils. The number of strands is not a consideration, but does become more important at much higher frequencies. Apparently DC characteristics are different from AC? On AC power my understanding is: stranded wire will carry more amps (less loss) than a single solid conductor, e.g. #12 stranded is smaller overall than #12 solid. I vaguely remember it having to do with surface area (more on stranded)?? Solid would, by definition, have MORE cross-sectional area than stranded, and thus would be smaller in overall dimension, non?? As Alice said "curioser and curioser". "You are what you drive" - Clint Eastwood | |||
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| 03/22 |
At normal AC line frequency, surface area does not have any influence on the wire current handling capability and would be not difference between stranded or solid wire. It is only when the frequency get above 50Khz where skin effect starts to influence the choice of wires. Ed 94 30' Breakaway #3864 30-BS-6B side entry New Cummins 5.9L, 375+ HP Allison 6 speed Spartan chassis K9DVC Tankless water heater | |||
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| First Month Member 11/13 |
Wire gauge is a function of cross-sectional area, expressed in circular mils. A solid wire is smaller diameter than a stranded wire of the same gauge and current-carrying capacity. . 84 30T PeeThirty-Something, 502 powered | |||
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| 3/11 |
From the AWG web site: The AWG tables are for a single, solid, round conductor. The AWG of a stranded wire is determined by the total cross-sectional area of the conductor, which determines its current-carrying capacity and electrical resistance. Because there are also small gaps between the strands, a stranded wire will always have a slightly larger overall diameter than a solid wire with the same AWG. (AWG = American Wire Gauge) 1993 32' Regency Wide Body, 4 speed Allison Trans, Front Entry door, Diamond Plate aluminum roof & 1981 Euro 22' w Chevy 350 engine and TH 400 tranny | |||
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