Under the hood generators, dual alternators etc.......

[wincrasher]

Many trucks and vans for commercial use have, as a factory option, a choice for a second alternator.

My Silverado HD had this option available. I'm sure the same is true for some of the Chevy vans. What the purpose of this option in a commercial truck I don't quite understand, unless it's for equipment like plows, hydraulic systems, dumpers or whatever. If I remember correctly, back in 2011 when I was looking to order my truck, it was only an extra couple hundred dollars.

Certainly this is why a company like Roadtrek can offer this extra alternator in their Chevy line of vans. I'm assuming they either source GM brackets and alternators, or they have a template that they can make their own. Perhaps it's the same for the Promaster, but I don't recall seeing that option on a build sheet.

[bobojay]

Originally Posted by wincrasher

Many trucks and vans for commercial use have, as a factory option, a choice for a second alternator.

My Silverado HD had this option available. I'm sure the same is true for some of the Chevy vans. What the purpose of this option in a commercial truck I don't quite understand, unless it's for equipment like plows, hydraulic systems, dumpers or whatever. If I remember correctly, back in 2011 when I was looking to order my truck, it was only an extra couple hundred dollars.

Certainly this is why a company like Roadtrek can offer this extra alternator in their Chevy line of vans. I'm assuming they either source GM brackets and alternators, or they have a template that they can make their own. Perhaps it's the same for the Promaster, but I don't recall seeing that option on a build sheet.

Second alternator is used in emergency vehicles, especially ambulances for all the electric loads. Since police and EMS are now, and have been using Silverados in some locations, as well as contractors that need 120v sources, there's another useage.

This is slowly tapering down as more and more electric loads have been paired down because of LED integration and more efficient motors etc loading

[Davydd]

After looking at what Advanced RV put in our B the second alternator installation is a bit more complex than slapping a second alternator under the hood whether there is a M-B factory bracket there or not. I didn't ask because there is a lot more involved including keeping it cool. Would you believe a 4/0 AWG wire from the alternator all the way back to the rear 800ah lithium ion battery bank behind the rear axle?

[acornpc]

Has anyone just replaced the Sprinter oem with the Nations high output alt? Can this be wired to charge both battery systems? Does this mess with the Sprinters computer?
Thanks!
Martin

[markopolo]

Interesting that this topic came back up. Last night I was thinking that if I'm not ever going to get around to installing that new alternator purchased more than two years ago then maybe I should just pay & have a shop do it.

The 19 year old 124 amp alternator in my van can supply 1000 watts to the coach and simultaneously pass a bit of amperage through the system for the batteries: http://www.classbforum.com/forums/f2...html#post36926 - you can see that the new alternator is not really needed in my van.

I'd be really curious to know what surplus wattage is available from a stock Sprinter alternator before buying a new alternator particularly if this method of powering the coach is only for occasional and short duration use.

That doesn't answer your question so hopefully others will offer some advice.

[booster]

I am sure Avanti will be able to answer most of the questions. He added the second alternator so as not interfere with the computer IIRC.

As Marko says, the Sprinter may have enough extra capacity to do what is needed, although the high load on the alternator without a indication where it is going (like seat heaters on, etc) might also confuse the MB compute.

Like Marko, we use a single alternator (250 amps), but it is able to supply upwards of 200 amps to the coach. Ours is an 07 Chevy, so the computer doesn't seem to be any issue, as all the computer does is look at the field voltage to help calculate idle parameters, it appears. We haven't noticed any difference in anything in real world use.

[avanti]

Originally Posted by acornpc

Has anyone just replaced the Sprinter oem with the Nations high output alt? Can this be wired to charge both battery systems? Does this mess with the Sprinters computer?

No, you cannot do this. Modern Sprinters have alternators that are connected to the vehicle's CANbus. They do not have a conventional voltage regulator. Rather, the ECU computes the necessary charging voltage and sends CANbus messages to the alternator. The Nation's alternators (or at least the ones I am familiar with) require external regulators (in my case a Balmar regulator/3-stage charger). So, they are not interchangeable.

This direct control of the alternator complicates the question about connecting your house systems to the coach battery. In older vehicles, this works just fine and, by most reports it still does with most modern systems. But, the OEMs are on the path toward much more sophisticated energy management. Mercedes has for some time published very conservative guidelines about how much current upfitters are supposed to take from the system. The guidelines are often ignored and so far the consequences do not appear to be dire. This may change, though. The Sprinter I4 engine has a new energy management package (mandatory on the I4, not available on the V6) which involves mysterious sensors and solid-state switches right on the battery terminals. Nobody knows exactly what this system does, but it probably has to do with tricks like only charging the battery during deceleration and deliberately delaying full charging so as to have some space to store excess energy on long downhill runs. (these are just guesses, but it is the kind of thing that the industry is looking at). One reason I went with a second alternator is that I wasn't seeing the kinds of currents I was expecting from my I4 engine, even though it has a large OEM alternator. Others have reported better results, though, so who knows?

The bottom line is that adding a second alternator gets you complete independence from all these issues; an extremely capable, dedicated power source; and proper 3-stage charging of the house battery. To me, these advantages seem so compelling that I would never consider going to all the trouble of installing an upgraded alternator without also taking the final step of installing it independently of the chassis systems.

[markopolo]

That's interesting to know.

When Avanti mentioned "Mercedes has for some time published very conservative guidelines about how much current upfitters are supposed to take from the system." he wasn't kidding. Page 47 of this doc - https://www.upfitterportal.com/files/en-ca/beg.pdf - shows the limit is only 40 amps. It's not clear to me if that limit applies to all of the available OEM alternator options. Page 48 lists an optional 250A alternator for example.

It does look like some B builders may have ignored that 40A limit.

[tex4judy]

Great information Avanti - thanks. You confirm our calculations for a house system independent of the engine system. Did you see my recent post on the system Adam Nations is putting together for my conversion? Nations alternator, Balmar VR, Lithionics batteries, Xantrex inverter.

[bobojay]

Avanti beat me to it, but the Sprinter has been this way for several years now. I suspect since the 2007 NCV3 models came out, but just a guess there....

I'm also sure that most new vehicles the last few years are the same way. It's not simple anymore like it used to be...

[booster]

I think there are degrees of how much issue there is with the big load messing up the van systems. Ours was basically, in 07, just an old style internal regulator alternator, with a reference load output to the ECM. Shortly after our unit, Chevy switched to having the voltage regulation in the van electronics so those couldn't use the drop in big alternators. DC Engineering now has a version of their big alternators that will work with that style setup in GM products that carries some electronics to interface, and they seem to work well.

Can't say for the other brands like the Chrysler stuff.

[mlts22]

I do know, from some Sportsmobile builds, that the Sprinter can use a second alternator, but it is highly recommended to get a variable high idle system to go with it. Were one to go that route, they could always go with a high output alternator and feed the battery bank like my Transit build from last year, or get a MEPS alternator which feeds 120 volts, a transfer switch, and have that feed the converter.

To me, I'd rather have a second alternator feeding the house batteries, just to keep the vehicle's subsystem as isolated from the RV's stuff as much as possible.

[avanti]

Originally Posted by mlts22

I do know, from some Sportsmobile builds, that the Sprinter can use a second alternator, but it is highly recommended to get a variable high idle system to go with it.

The Nation's Alternator will produce 200amps at normal idle, so the high idle option is not really all that important from that perspective. I am aware that there is a lot of noise on the Internet about the evils of idling a Sprinter. It may all be true. BUT, after careful search, I have been unable to identify a single published Mercedes document that says that idling is prohibited or even undesirable. Again, I am not saying that it is a good idea (and I do not do it myself), but absent any bona fide evidence, these "no idle" claims have got to be classified as Internet folklore.

Were one to go that route, they could always go with a high output alternator and feed the battery bank like my Transit build from last year, or get a MEPS alternator which feeds 120 volts, a transfer switch, and have that feed the converter.

Great West Vans had begun to install the MEPS system shortly before they closed their doors. At first I was excited about this option. But upon reflection, I have concluded that it really doesn't make a lot of sense in an RV. They are a good choice in vehicles such as ambulances that use the engine as their primary power source. But, electrically-sophisticated RVs have batteries, large inverters and shore power. The MEPS system is larger, more complex, and MUCH more expensive than a 12VDC alternator/charger. Other than the ability to use smaller wires, there is really no advantage to the MEPS system over a DC alternator used in conjunction with a standard inverter/charger.

To me, I'd rather have a second alternator feeding the house batteries, just to keep the vehicle's subsystem as isolated from the RV's stuff as much as possible.

Agree!

[pprevill]

Hello all,

I read all the post in this topic, I'm probably more confuse than I was before so I need a little bit of help !

I just buy a new Safari Condo LSX based on a GMC Savana 2016 frame with a V8 4.8L. The mothorhome have two AGM 190A/h batteries. I was concerned about the autonomy of the vehicule since we always want to use it unplugged. The saleman told me that the alternator is 242 amp and i need to drive 3 to 4 hour at highway cruise speed to charge the battery. I also have 3 90W solar pannel on the roof.

I find that 3 hours at hwy speed is very long to charge the batteries. That is why I am so interested in this topic. I have discuss with a roadtrek saleman while I was shopping for the mothorhome and he confirm that any roadtrek with the underhood generator can charged 400amp battery bank in 30 minutes iddle speed. That is interesting ! I mean, a 30 min slow drive to get some milk coud charge our batteries.

So I'm wondering if anyone can help me understanding my current (future) setup on my van (Why it take so long with a 242 amps alternator to charge two AGM batteries) and how I can boost this with a underhood generator ? My other idea was to buy a honda 2000 generator get it modifed to be able to run on propane, plug it to my van propane tank. Underhood generator is more convenient...

Thank you !!

[booster]

You have quite a few charging sources to charge and some will go fast like the alternator. The problem is with the batteries charging speed. AGM batteries will charge quickly to about 85% full, but the last 15% takes a long time. The 3-4 hour estimate is probably even on the light side to get completely full. Add to that the fact that AGM batteries do need to get completely full every 5-10 charge cycles, and you have to be able to get to a place with a way to charge for somewhere in the 8-10 hour range, assuming the charge source is set to charge that long

If you are trying to live without ever using shore power, probably the best you can do is drive until the batteries are 85% full early in the morning, and then park in the sun and let the solar take them as far as it can after that. Several of us on here do that, and it works OK, but will rarely get you totally full unless you start out nearly full and have very good sun conditions. Not ever getting full will reduce the battery life a lot.

The Roadtrek guy was talking about the lithium batteries they have available that will charge fast all the way up to nearly full, and never have to be charged all the way full like AGMs do which changes everything and makes life on the road a lot easier.

There are lots, and lots of discussions on the board about the best ways to charge AGM batteries to maximize the usable power and life, although many of the recommendations are charging components different than come with most stock units.

The place to start is to make sure you have a real battery monitor, like a Trimetric, in the van. I don't know if Safari puts them in or not, but it would pay to ask if the do, or could. Without a monitor, you will perpetually in the dark (pun intended) when it comes to how much charge you have left, and how far you got recharged. The little lights that most vans come with are pretty much useless in most cases.

[avanti]

Just because your OEM alternator is rated at 242 amps does not mean that you will necessarily get anything close to that when charging your house battery. First of all, the engine and chassis systems are consuming some of that power. Moreover, modern engines increasingly have "smart" charging systems that seek to maximize energy efficiency using complex algorithms that (for example) shut down the alternator during acceleration. The effects of these designs are not well understood for most vehicles, and represent a moving target. With a second alternator, you have 100% of the available capacity going to your house batteries. Moreover, you also get a dedicated, proper 3-stage charger, rather than depending on whatever your engine happens to decide to provide.

[gregmchugh]

The Roadtrek guy was not giving you correct info, the underhood generator provides 200 amps or less at idle and 300 amps or less when driving. A 400 amp hour Ecotrek lithium battery bank (two 200 amp hour Ecotrek modules) has about 360 amp hours capacity so to fully charge the battery bank starting from the fully discharged state would take at least 1:45 at idle and at least 1:15 while driving. A 1/2 hour underhood generator charge can replace 100-150 amp hours at most.

[avanti]

Originally Posted by gregmchugh

A 1/2 hour underhood generator charge can replace 100-150 amp hours at most.

That's true. But, for many campers, that is enough to keep going indefinitely, especially combined with solar.

[booster]

Are the 190ah batteries in a Safari Condo six volt, or twelve volt. Big difference in capacity and charge acceptance between the two. On 190ah of battery, 100-150ah of recharge is a lot and a short time to recover to 85%, while with 180ah, the time goes up. It will all boil down to how much power they use per day, I think. Does it have a compressor frig or two?

[gregmchugh]

Originally Posted by avanti

That's true. But, for many campers, that is enough to keep going indefinitely, especially combined with solar.

Agree but Roadtrek has fostered the idea that a 1/2 hour underhood generator run will recharge the batteries without providing any type of details. Many people hear the statement and reasonably assume it means bringing a fully discharged battery up to full charge.