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Old 11-04-2016, 09:50 PM   #1
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Default Experimental engine generator setup

I have been watching all the threads on engine generators of the various kinds and applications with interest for a long time. We also have done an upgraded single alternator in our 07 C190P Roadtrek using DC Power 250XP with internal regulator. The single works OK, but has some things I don't care for, and the other systems I have seen, heard, or read about have some different things I didn't care for, so the search has been on for a way to cover most of the issues.

What I didn't like about the single 250XP. It charged well and did not turn itself down as much or as soon as the Balmar regulated units seem to do, but allegedly did have 3 stages of overheat output reduction. It was capable of averaging nearly 180 amps average for at least an hour, in relatively normal temps (70s). At 180 amps it would heat up the 440ah AGM bank by about 20 degrees, but the alternator does not have battery temp correction, and that would put the voltage higher than recommended at that temp. If it was hot out, it would be worse, I think. It also was being run pretty hard, as most of the setups are, and was the only alternator, so failure was always possible. Carrying a spare would be one way, or put in a parts store stock one temporarily, but redundancy would be better IMO.

The standalone systems almost always have an external regulator that is almost always a Balmar. They work OK for the most part, but there were some things I would change if I could. The Balmar cuts the charge rate in half when the alternator temp sensor gets to 225 degrees, so a 270 amp alternator will net substantially less than the rating. The numbers I have seen looked to be in the 65-70% range of rated. This is also done on and off, so lots of thermal cycling which is never a good thing. The instructions are not clear if the turndown setting is adjustable or not, and Balmar has not yet answered my email to them about that. The charging is controlled by the Balmar as a multistep based on a algorithm that has some adjustability, but bases the final transitions on field %, not the amps to the batteries or even to the batteries and loads, so is not particularly accurate if you are trying to get your batteries totally recovered to 100% full without overcharging. It also does not allow manual forcing of the charge stages, so you can't tell it to stay in absorption longer to get the batteries full, or have do an absorption cycle if it goes straight to float based on battery voltage at startup, which can be artificially high due to solar and other things. The Balmar also appears to need at least a 4 amp load on it while running or it won't transition to float properly, that some have seen. With the coach as the only load, many of us don't have that much load reliably. With a standalone you do need to make sure that the batteries cannot be disconnected when the alternator is active or could be turned on with no batteries as it could wreck the alternator.

To address the issues, it appeared that a very high capacity system connected to both the chassis and coach (with coach being able to be disconnected) would be the best. By using an external regulator that has output limits (really field % limits), you could reduce the output of oversized alternators to what the wiring and batteries could handle, making it so they would run cooler and not need cycling. If the external regulator was a smart type, it would need to be able to be forced to the different stages, in particular absorption. It would need battery temp compensation, and hopefully alternator temp protection as you lose that from the alternator when you go external.

Here is what we came up with to try to address all this stuff.

* Dual alternators, using our existing 250XP and a 280XP (Nations dual alternator kit) with both of them setup for external regulation. They are wired pure parallel in all respects, running both the coach and chassis, with a Blue Sea solenoid disconnect for the coach. They both run off the same field output on the external regulator. By going parallel, we can get massive total output from the normal case alternators, and they share the load to stay cool in the range we use.

* Ample Power V3 external regulator that has two dash switch selectable output limits and can be forced into absorption at any time from a dash mounted switch. It has battery temp compensation, but not alternator temp protection (bummer on that).

The intent is to use the two limits for different needs. One will be set at about 180 amps at highway speed, which about the max the batteries like to see longer term due to heat, although we may be able to go a bit higher if the compensation helps. This setting would be for longer drive days to recover whatever amount the batteries are down, and could take them all the way full or full enough for the solar to top off if there is good sun and enough time. The second setting will be set at something in the 260-280 amp range and will be used for short time, quick recovery, charge if needed, or a trip to the dump station or trailhead. The alternators should be able to stay cool at this load easily, but the batteries and wiring would be a bit temp limited at more than about 20 minutes. These are highway speed outputs, and because the limits are proportional, the limits also reduce output over the entire range, including idle. One or the other limit will always be in place, controlled by an either/or switch, as 500+ amps is not within the limits of the rest of the systems.

There is an on/off switch that controls the absorption stage, and when the switch is on, the regulator will stay in absorption until the switch is turned off.

To get charge accuracy, we will have the system locked in absorption and just watch the battery ammeter we have on the dash. When the batteries hit 2-3 amps of acceptance we turn off the absorption and it will go to float, or we can disconnect the coach from the engine and let the solar take care of it. Very easy and very accurate in all respects

I put thermocouples on the alternators, but have found they go nuts when the engine is running, but are accurate when it is off. Still need to work on that, as that is the fall back safety position to protect from alternator overheat. Even though at the output % we will be running is very low and should never get them too hot, it would be nice to know. At least we can stop, shut off the engine and see the temps instantly on the digital thermometer on the dash.

We have it running and preliminarily setup, and all is looking good to this point. I will put the preliminary test results in the next post.
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Old 11-04-2016, 10:04 PM   #2
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I have run two sets of data, but didn't realize the output limits were proportional on the first set, so won't list it. What follows what I got today, in the garage, doors open, on stands, hood up, mostly idling but up to 2000 rpm to get the highway speed outputs, about 68 degrees.

These are relatively warm alternator numbers, with the alternators pretty stable at about 170 degrees with the temp gun.

The actual output of the alternators is probably about 20 amps higher than the readings, which are amps to the batteries, as the chassis is also being run.

Low output setting gave (target 180 at speed) 195 amps at 2000 rpm engine and 122 amps at 545 rpm idle.

High output setting gave 250 amps at 2000rpm and 208 amps at idle.

I would expect all these numbers will be lower in hotter weather and longer run times. There is still plenty of turn up range on the limits, so they can be increased easily.

120 amps at idle is fine for us, as about all we would use for would be to cover a high amp, short time, use like running the microwave or hairdryer to save taking it out of the batteries. I can't imagine us sitting and idling to charge batteries, as I just don't like idling any engine continuously, but if we had to the 200+ amps from the high output setting would do it well, and could be use while at the dump station or similar.

We are liking the numbers so far, and they are in the range we hoped for and predicted, so all good to this point. 200 amps at idle is a lot amps for only 545 rpm idle speed (1690 alternator speed, which is really low compared to most, I think).

The thrown out first test seemed to show the idle maxing out at about 185 amps hot, and the alternators were hotter at about 200 degrees, but I am not certain of the data. It would make sense, though that some output would be lost to the heat.

Hopefully, the weather will hold so we can get out for a driving recharge test in the next few days.
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Old 11-04-2016, 10:20 PM   #3
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The big benefits, as I think they will work out are:

Lots of capacity for recharges and loads, more than the typical standalone will produce, with alternators running without excessive heating.

Very high idle output.

Forcible into absorption

Accurate charging control base on amps of ammeter

Selectable outputs based on need

No turn on or turn off damage possible

Built in redundancy as if one alternator dies, we just keep going unless it is a mechanical lockup

Easy switch to backup regulator, fixed voltage regulator. Balmar ERS which is smaller than a deck of cards to carry with.
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Old 11-04-2016, 10:40 PM   #4
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Old 11-04-2016, 11:06 PM   #5
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Hearing from Avanti reminded me of what I forgot to emphasize. This only works if you have an PCM engine system that either does not control the output of the alternator, or can be defeated without causing an issues. Older units like our 07 don't control, and there are "bypass" kits for at least some of the other models and years, mostly generated by the high output audio crowd, who want crazy outputs. Currently, I don't think that there is a bypass for the Sprinters, but I have seen some for some of the Fords, so a transit might get one. Don't know about the Fiat based Promaster.
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Old 11-04-2016, 11:12 PM   #6
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It's quite the setup:

530 amp combined rating potential. The low setting of around 180A is 34% of the potential output so very easy on the alternators. The high setting of up to 280A is still only 53% of the potential output so again easy on the alternators. Easy on the alternators should mean long life and no belt issues is my assumption.

The high setting 208A at idle would likely be guaranteed minus some temperature related loss in hotter weather. The output won't vary like when the high temperature protection of setups with the Balmar regulator kicks in and reduces the alternator output. You'd be able to run the air conditioner and simultaneously charge the batteries if you choose to do so. It would avoid the net loss of battery capacity a.k.a death spiral that we've heard of.

Obviously it is a tremendous advantage to see the amp flow through/into the system so you know when the batteries are near fully charged. There is no guessing involved, no overcharging and no wasted fuel.
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Old 11-04-2016, 11:25 PM   #7
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The whole idea of the temp turn down is interesting, and of course, needed to prevent destroying the alternators. The big question is what temp to turn down at, and how far to turn down. The 50% turn down the Balmar does essentially guarantees thermal cycling. It would be a much more useful system if it did step down, and them back up to a maintainable, non cycling output.

I found it fairly confusing in the Balmar literature, as in the MC-612 manual it very plainly states not to let the unit thermal cycle off the overtemp alternator sensor, with a statement to fix whatever caused it. With our systems of non 100% duty cycle alternators, it is nearly guaranteed that the alternator will thermal cycle unless you set the output of the Balmar manually with the belt load manager to reduce the load on the alternator compared to rated. I think you can go down 45%. Davydd's temp sensor failure, and ARV's change to the huge Delco unit, would indicate that they were just plain running them too hard, thermal cycling, and busting up parts.

All the external regulators that are being uses seem to be so marine specific, and the marine alternators are all 100% duty rated, so the whole thing with our alternators that are more like 60% duty, really messes things up. The Ample Power regulator doesn't even have alternator temp sensing as an option, they just say use a 100% duty rated alternator.
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Old 11-04-2016, 11:32 PM   #8
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Has anyone thought about installing a second AC compressor/unit to cool the RV while running? Seems it would be more efficient to run rather than alternator to battery to inverter to AC.
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Old 11-04-2016, 11:55 PM   #9
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Quote:
Originally Posted by mojoman View Post
Has anyone thought about installing a second AC compressor/unit to cool the RV while running? Seems it would be more efficient to run rather than alternator to battery to inverter to AC.
The biggest issue would probably where to put the condenser, I think. Maybe underneath with it's own fan?
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Old 11-05-2016, 12:08 AM   #10
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Quote:
Originally Posted by mojoman View Post
Has anyone thought about installing a second AC compressor/unit to cool the RV while running? Seems it would be more efficient to run rather than alternator to battery to inverter to AC.
You probably don't need a second compressor. The normal van "RearAC" uses taps off of the factory engine compressor.
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