Quote:
Originally Posted by boywonder
Are the alternator vendor links in post 1 reputable brands or examples of hype?
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As to the other brands not sure. DC Power claims to be selling into DoD & Military/Police applications. They are pretty solid on the phone and also make a secondary '270-280A' kit for Sprinters. (It is their alternator and uses MB style brackets). I liked what I heard - they source only Grade A rotors into their high current applications and make most of their own internals/parts. The cases are all generic. Pulley size would depend on final design, but they also use a clutch pulley.
Quote:
Originally Posted by Wrinkledpants
Like others, I'd be concerned with something that heavy producing that much power having reliability issues elsewhere.
SMB is not going to install that if it goes against the MB regs (which it sounds like it will).
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Agreed...and frankly I don't need/want such a massive unit. I wonder if Advanced RV has worked obtained MB permission for the 40SI case.
Quote:
Originally Posted by Wrinkledpants
Maybe I'm missing something in your math, but a nations alternator will put out 150 amps at idle, and 230 at driving speed (or high idle). That's registering at the battery by other folks that have this setup. ...
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These are good data points - thx.
And yes, assuming I can find a way to limit battery current into the lithium stack while the AC is running...an acceptable outcome could be simply confirm a Nations' style alternator is just fine for the application.
Nations datasheet/literature spec'd 198A-200A @ 'idle' - idle in the alternator industry for 2250 alternator shaft RPM. Typical hot vs cold rating is about 15% diffential with hot being less. If they are only hitting 150A, then the alternator isn't quite hitting 2250 RPM @ MB engine idle.
Most of the secondary alternators are going to be a Denso Style Case - MB OEM style. There are small case and large case. The ones in these applications are considered a 'large case' alternator for automotive applications. If it is a Denso case, then it is a newer 6phase hairpin design with a modern/latest rectifier/output regulator concept.
My numbers from before (30-40% of full rating were based on the older case designs, some 3phase, some older rectifier designs). Newer style windings with a higher phase count - we may see 50-65% of full rating at idle. (Alternators are actually variable frequency AC generators with a DC rectifier output stage).
In alternator design, there is a tradeoff between total/max output and idle current. Realistically, a '270A' alternator and '370A' (in this case size) will have a similar output current at idle RPMs levels. It isn't until the alternator RPMs start to increase is when difference really starts to appear.
In an ideal world, and in my application a system controller would observe the current flowing into the batteries, sense load current, and alter the alternator output voltage. (The batteries' current is controlled by its ability to accept charge and by the charging voltage).
By controlling the system voltage (via the alternator's field current), we can regulate/reduce current into the batteries. The load will continue to draw what it needs...all with the goal of not straining the alternator (and increasing/decreasing the amount of current into the batteries).
Since my application is running an electric A/C AND charging batteries, I could be cranking for hours. Example: I went to Phx in August through Southern CA. The only time it dropped below 105 was at night....mostly it was 110 LA Area to Queen Creek. The A/C on my jeep was on high the entire drive time trying to keep it cool in the back for the kiddos & dog. For the sprinter, I won't really know until I try and I don't want to throw away $900, when $1400 would have solved the problem.
I could also be overthinking this...