Best ways to control big engine generators?

[booster]

One of the things that I keep getting back to thinking about, and a thing I get asked about very often, is why the installers of engine generators do a direct hook up to the coach batteries. No separator, no cutoff switch, many times not even a fuse (I hear), etc. (this is only with standalone engine generators, not oversized alternators)

These setups are often connected to big battery banks, which are also pretty expensive to replace. (I have been looking at how much 440ah of Lifeline AGM will cost us, and it is about $1200+ most places). Having a relatively uncontrolled charging source, it is really just a huge single stage charger (300 amps or more is common), continuously feeding batteries that can be full already, and be very hard on them, and shorten their life a lot. If you are the type that moves every day and drives quite a bit, the batteries could be seeing many hours a day of overcharge. Longer stays, shorter drives, etc lessens the effect.

The first question that always comes up, is why not add a disconnect switch like some of us have done on our alternators that also feed the engine battery. Best I have found out, this is not possible do to the alternator needing to see a battery to stabilize the voltage it is making. Without the battery, the voltage can go wild and ruin the regulator, and can also put a huge spike on the coach when engaged, if the engine is running. I haven't heard of any practical way around it, but it may exist somewhere.

The other common solution recommended is to use a 12v to 12 charger in the circuit. Although not perfect, this will probably eliminate 80%+ of the overcharge problems. The missing parts using the 12v to 12v charger are that the biggest one (that I know of) is 120 amps, which would be small for some folks, and that the chargers currently available (again that I know of) are all timer units that go to float based on time rather than actual battery state of charge. Not a bad solution and at a cost of somewhere in the $650 range for the charger.

The other solution that is mentioned is to use a "smart regulator" on the engine generator. This is not a bad solution either, but the same timed float transitions apply, so they have the similar profiles to the 12v to 12v charger. They don't limit the output like the charger does.

But, there may be an add on to one of the smart regulators that could take care of nearly all the issues, if I am reading the literature correctly. (could also be way off base, too).

This controller

https://amplepower.com/products/emon2/index.html

when added to this smart regulator

http://www.amplepower.com/products/sarv3/

claim that the regulator will come out of absorption based on control from the shunt based controller that is monitoring battery state of charge. It doesn't say if it does it by using return (ending) amps, % full calculation, or AH put back in, but any of them would be way better than any of the other control methods available for an engine generator.

If this stuff actually works the way it appears, it would be a very good addition to any of the direct connected engine generator setups, and give full, automatic, control of the charging to the coach batteries while driving, without over or under charging. Looks like the cost for two items is about $750, so not much more than the 12v to 12v charger, but with much more capability.

Anybody know anything about these products?

[avanti]

These are great questions. This whole area is kind of hazy to me, too. A couple of thoughts:

1) Is it really true that people simply blindly connect these generators permanently to the house battery? I guess it all depends on how "smart" the unit's integral charger is. After all, that is how the chassis charging system works--it is fine because the regulator is designed to work properly with the chassis battery. In principle this could be true for the coach as well, depending on details.

2) Your discussion begs the question of exactly why we believe that a second alternator is better than a single large one. The best argument I have heard is precisely that it permits independent regulation. If this isn't being done, then I'm not sure there is and great advantage.

3) No fuse?! That is kind of hard to believe. Certainly violates RVIA rules.

4) I wonder how these smart devices solve the "no battery" problem?

5) The other alternative is the direct-to-AC approach that Great West is taking. This is pretty attractive, since (in addition to easier and cheaper wiring), it lets you depend on your existing inverter/charger for proper charging.

[booster]

As far as I know, if they don't use a 12v to 12v charger, a smart regulator, or now the Great West AC system, they are all directly connected to the batteries. I don't think many are not direct.

It certainly does allow separate regulation, if the bother to do it .

The standard charging system "profile", for what it is, works based on passenger car use and starting battery technology. Starting batteries are almost always the low gassing, high voltage resistant, calcium? lead wet cells so they can handle being hit hard to recover quickly after starts, and suffer lower consequences from maintained higher voltages. In the real world, it kinda works. I monitor the state of charge on any of our batteries that aren't sealed, which right now is the factory Panasonic in the Honda (7 years old), and a replacement Interstate in the Roadmaster (unknown age). After a few months of use in our normal retired life driving, they are never full, usually at about 60-80%. I then do a light equalize on them to fill and recover them. Obviously, the charge system isn't perfect even for the starter battery, and it is horrible for deep cycle, IMO, so a better control system is needed for RV coach charging.

The other reason that I have heard to use a separate generator, is that it decreases the likelyhood of a primary alternator failure, putting you by the side of the road, do to overworking the single alternator. Valid to some extent IMO.

The fuse thing is something I have heard a couple of places, but could be hearsay. It may also have been referring to aftermarket installs, where all rules are off, it appears.

The no battery issue probably isn't any issue for the smart regulators, as the do the same as internal one, just smarter, and control the excitation current only. I think the 12v to 12v chargers have a reference through them, although that would be something that should be checked out. Most of the application stuff I have seen for them shows them into a single alternator setup, so the starter battery would be in the circuit for the alternator. Good question, would need to check out, I think.

I do think we are going to see solutions for these issues in a few years, as folks are going to be frying expensive batteries and demanding to know why. I wouldn't be surprised to see a separate 12v input to something like a Magnum inverter/charger that would be a 12 to 12v charger that could run off the shunt based charging system control they already have in them. That would be sweeeeet!

[avanti]

I don't find the "primary alternator failure" argument particularly persuasive. Of COURSE you can increase your reliability by installing redundant components, but that doesn't mean that it is cost-effective. It comes down to proper engineering. If you have a single alternator that is not being stressed beyond its design specs, then there is no reason to expect early failure. Plus, if you DO have a failure, you can drive a long way on a large house battery. People have been to known to complete their trips using their Onan genset and propane.

Yes, a Magnum or Outback-grade solution to this issue would be great. But those guys' attention seems to be dominated by the home solar market, so it probably isn't a priority for them. Of course, the boat guys are rich... I wonder what the mini-hydro gang does?

[Boxster1971]

Ample Power Company seems to be well thought of over on the Cruisers Forum, at least for lead batteries.

If you are considering an upgrade to Lithium I highly recommend these two places to read about how the cruiser sail boat community has embraced LiFePO4 batteries.

LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks
http://www.cruisersforum.com/forums/...nks-65069.html
This thread has over 4,000 posts - but a lot of good info and these folks will answer questions from us RVers.

LiFePO4 Batteries - Thoughts & Musings
http://www.pbase.com/mainecruising/lifepo4_on_boats
Especially read page 3 that starts out with:
"Alternator Voltage Regulation For LiFePO4
A good voltage regulator is critical for an LFP bank. It is my belief that no better regulator currently exists for LFP than the Balmar MC-614. This regulator allows every conceivable parameter to be adjusted from; voltage, to alt temp compensation, bulk, absorption and float duration, thresholds for transitions from bulk to absorption or absorption to float, the ability limit the field current and do "current limiting" of your alternator etc. etc. on and on. Of critical importance in LFP it also uses a dedicated voltage sense wire that does nothing but sense voltage, this wire carries no current on it, so you get an accurate reflection of battery terminal voltage, provided you wire it correctly."

Enjoy,
- - Mike

[booster]

I probably should have made that clear--this is in relation to lead batteries, not lithium, which have their own protection systems.

Do you recall seeing anyone on the Cruisers that is using the setup I described to control alternator charging profile off of a shunt?

[Boxster1971]

Originally Posted by booster

I probably should have made that clear--this is in relation to lead batteries, not lithium, which have their own protection systems.

Do you recall seeing anyone on the Cruisers that is using the setup I described to control alternator charging profile off of a shunt?

No worries -- I speed read lithium for Lifeline in your original post.

I just did a quick search over on the Cruisers Forum to find some positive post on the Ample Power Company. You might just consider joining the Criusers Forum and asking some questions. They seem to be a friendly group and many are also current or past RVers. That forum is operated by the same folks that now run this one so the look and feel of the forum will seem familiar.

Alternatively you could contact Ample Power directly with your questions. The Cruisers folks say they are responsive.

Have you seen this document from Ample Power?
http://www.amplepower.com/primer/primer.pdf

Also have you considered that you won't be able to alter the regulation of an OEM alternator. That is true of many, not sure about your Chevy.

[booster]

Thanks Boxster. I may have to give them a call. This is not something we intend to do for our upgrade, as we are all set to do it manually while driving, off our big alternator, but it comes up a lot.

Good point on the modifying the alternator, which would be for any of them that regulate from the ECU. With a standalone generator you don't have that issue. Our alternator isn't that way, but many are. This would probably be a good reason (Avanti's question) why they have been going to the stand alone engine generator setups because you can use any control system you want on it.

[mlts22]

A number of the high-amp alternators I looked at have really two stages: Full bore, and off. When the batteries get near 100% SoC, they stop charging. When it drops to the upper 90s, the alternator will start firing up again.

As an alternative, another member of the forum mentioned the MEPS alternator that is 120 volts, up to 5000 watts. That could always be hooked up via a high amp, multi-stage converter to feed the batteries exactly what is needed, and allow skinny, 120VAC wires to be run as opposed to the fat wires needed for high amperage, 12 volt connections. Of course, the vehicle needs support for two alternators, but that is doable in both the Sprinter and the Transit.