FitRV's lithium/alternator/inverter setup

[tex4judy]

An update for the guys on this thread. We have all the major electrical components installed and they work great. Many thanks to you for your great advice - I'm sure you rolled your eyes when I rolled out my first questions; was starting at just about zero.

The interior of the van was finished enough to "camp" in it last summer for a trip from NM to WA for two reunion campouts and then to TX for another. But all the systems Fit RV and others described worked great; and having the A/C while driving (or plugged in) was perfect.

Thanks again. We now have some experience with the wiring set up and operating the inverter. Happy to share it if it would be helpful.

[Mike]

Originally Posted by cruising7388

As you point out, if the coach alternator croaks you still have ignition and propulsion but what about the reverse? Out in the boonies, with totally independent systems like RT uses, what do you do if it's the engine alternator that quits? Without some way of getting some ignition support from the coach batteries won't you end up SOL in pretty short order?

If I was able to get it the way I wanted, I would do exactly what you suggest which is to employ independent identical beefy alternators and regulators. But what I would also do is have the wiring for both alternators run into some sort of terminal block where a dead engine alternator can be disconnected and the coach can be plugged in its place and keep you going down the road. In fact, with some conservative use of coach loads there would be no reason why as an interim fix you couldn't direct the still working alternator to address coach requirements in addition to the engine side.

The irony is that in earlier years the loss of the single alternator was not as consequential. As long as you cranked up the Onan reasonably soon after the alternator is kaput warning light came on, you could drive from coast to coast with the converter charger and smart separator set up. It's noisy. But it works. Trust me.

Which reminds me, one disadvantage of fully independent charging systems, is that, at least with RT, unlike their AGM setup which uses a bi-directional separator, there is no way to charge a depleted engine battery from shore power. Unless you hook up an independent charger, the only way it can be charged is from the alternator but if the battery is so inadvertently depleted that it can't start the engine, that doesn't help. On the RT 210/190 coaches with the UH alternator, there is no battery boost to get some temporary suds from the coach batteries and if memory serves, Mercedes curiously prohibits the coach builders using their platform from installing a battery booster assist feature.

Just happened upon this lengthy thread, and was wondering if anyone had followed up on the Mercedes prohibiting chassis battery boost from the coach batteries issue, if that's what this implies? I've got a 2018 Navion on order, and the OM shows a battery boost switch is installed and available for use, in the event the chassis battery needs help to start the engine. As I read it, of course.
If it's already been debunked, then "never mind" (Roseanne Rosannadanna?).

[prfleming]

Originally Posted by cruising7388

Which reminds me, one disadvantage of fully independent charging systems, is that, at least with RT, unlike their AGM setup which uses a bi-directional separator, there is no way to charge a depleted engine battery from shore power.

I had a situation where my engine battery got run down while on shore power, listening to the van radio, etc.

I carry a 35 foot 2 gauge jumper cable. I clipped engine battery onto the inverter/charger posts and shore power charged the engine battery enough to start.

[Boxster1971]

Originally Posted by Mike

Just happened upon this lengthy thread, and was wondering if anyone had followed up on the Mercedes prohibiting chassis battery boost from the coach batteries issue, if that's what this implies? I've got a 2018 Navion on order, and the OM shows a battery boost switch is installed and available for use, in the event the chassis battery needs help to start the engine. As I read it, of course.
If it's already been debunked, then "never mind" (Roseanne Rosannadanna?).

Don't know if has been debunked. But I can tell you that the Airstream Interstate Sprinters have a battery boost switch that allows you to use the house battery bank to start the Sprinter if the chassis/starter battery goes flat.

Airstream works closely with Mercedes and I'm sure they wouldn't provide this boost feature if Mercedes didn't allow it.

- - Mike
2012 Sprinter 3500 Extended converted B-Van by Airstream

[cruising7388]

Originally Posted by Mike

Just happened upon this lengthy thread, and was wondering if anyone had followed up on the Mercedes prohibiting chassis battery boost from the coach batteries issue, if that's what this implies? I've got a 2018 Navion on order, and the OM shows a battery boost switch is installed and available for use, in the event the chassis battery needs help to start the engine. As I read it, of course.
If it's already been debunked, then "never mind" (Roseanne Rosannadanna?).

The RT Chevies still don't implement battery assist. I don't know whether the Sprinter now delivering has this feature.

The current Galleria Li3 has parallel charging capability between the coach and engine alternators, and while it could undoubtedly be engineered to do it, I doubt if their engine alternator quits that their Nations alternator would also provide chassis support.

I would still like to see a design that offers dual alternator support on a full time basis. The Mercedes alternator is rated at 200+ amps pretty much loafs and would be of great help to a Nations alternator that struggles to support the load demanded by a 13.5/15 kw roof A and/or the convection bake mode on a microwave oven.C. Some enterprising members aboard have accomplished this. It used to be easier with earlier generation engine alternators but with the latest generation of smart alternators, getting them to cooperate in paralleling with the coach alternator is problematic.

[Bud]

Purchased a battery boost earlier this year. Used it earlier this week with my neighbor's big truck engine with the engine's battery Dead, Dead, Dead.

The engine started normally, < one second.

https://smile.amazon.com/gp/product/...?ie=UTF8&psc=1

Bud

[booster]

Originally Posted by cruising7388

The RT Chevies still don't implement battery assist. I don't know whether the Sprinter now delivering has this feature.

The current Galleria Li3 has parallel charging capability between the coach and engine alternators, and while it could undoubtedly be engineered to do it, I doubt if their engine alternator quits that their Nations alternator would also provide chassis support.

I would still like to see a design that offers dual alternator support on a full time basis. The Mercedes alternator is rated at 200+ amps pretty much loafs and would be of great help to a Nations alternator that struggles to support the load demanded by a 13.5/15 kw roof A and/or the convection bake mode on a microwave oven.C. Some enterprising members aboard have accomplished this. It used to be easier with earlier generation engine alternators but with the latest generation of smart alternators, getting them to cooperate in paralleling with the coach alternator is problematic.

The claim is that the vehicle manufacturers don't want/allow having a parallel extra alternator in the system, and MB even limits how much extra power they allow you to take off their stock alternator. I think even the temporary connection of a boost would technically violate those rules. Mostly, I think it all is an excuse, though, as the aftermarket has been finding ways around those kind of things for years, particularly the big output audio crowd. I think a modern Chevy could be converted to parallel by using the parts they have come up with to integrate non pcm control alternators..

Our van was the last of the ones made with an internally regulated alternator (07 Chevy) so we did put in a parallel system, which IMO, does work better than the stand alone because the alternators run cooler and don't lose capacity as bad. We have the ability to charge at similar rates as davydd's huge Delco system.

There are some caveats to the parallel system however, my opinions:

I would always use two identical alternators so the match output and also can be run off the same regulator well. Two Nations alternators will give as many amps as a single 4/0 cable can handle, continuously.

It is best to be able to limit the output of the alternators to be able to keep them cool. The Balmar regulator does this by turning them up and down when they get hot, which works but it isn't all that great to thermal cycle things. We used an Ample Power regulator which allowed us to set two different turn downs, but it is no longer available. The Balmar can also be set to go to 50% with a manual switch which is also an option.

A critical part is that you will wind up with all the output controlled by a single regulator, so if it fails you are out of charging completely. We carry a $30 single voltage spare that is setup to easily plug in to get one alternator running until we can fix it completely

Another option is to forgo the separate regulator and use two internally regulated Nations alternators, which will also work. They use Denso regulators in them that are somewhat "smart" and turn down the output when the batteries are nearing full, and have their own built in high temp turn down (which lets the alternators get a lot hotter than the Balmar does). The good it that the system is easy to do, has built in backup with two standalone alternators, and it will have very high output. Bad is that you lose the versatility of the standalone regulator.

[Mike]

Originally Posted by prfleming

I had a situation where my engine battery got run down while on shore power, listening to the van radio, etc.

I carry a 35 foot 2 gauge jumper cable. I clipped engine battery onto the inverter/charger posts and shore power charged the engine battery enough to start.

I've used that methodology in my 2002 Roadtrek.
It also had a sundial for a clock and "engine breaking" was always a possibility.

[avanti]

A few random thought on this topic:

1) When I added my second engine alternator, I simply left the old isolation relay in place and connected it to a switch on the dash, so it functions as the "boost" feature.

2) I suspect that from the OEM perspective, the problem with the upfitters adding "boost" is that there is no simple way to prevent the user from trying to use it to start the van with a completely dead battery. These setups work fine to literally "boost" a weak starter battery, but if the battery is totally dead, the wiring and isolator are typically totally inadequate to handle the full current of the starter.

3) Another potential OEM concern might be the fear that the user might succeed in starting a van with a completely inoperative chassis battery (or even no battery at all). This will damage the charging system.

4) The problem with using the OEM alternator to supplement a second engine alternator is that (as Booster said), the OEMs (at least MB) severely restrict the amount of current you may draw for external use. IIRC on the Sprinter it is 25A. Not enough to be worth the bother.

5) As for using two external aftermarket alternators, this can be made to work with older vans, but modern LIN-based charging systems are too tightly-integrated with other vehicle systems to make this feasible. Even if you could make it work electrically (which would not be easy), the "smart" charging algorithms (basically similar to regenerative braking on EVs) would likely foil your efforts.

[booster]

Good information from Avanti.

Re #5, I don't know how the newer Chevy systems compare to MB, but they do stuff like selectively charge the battery during decel, etc, so may be similar. When I was doing a bit of reading on it a while ago, it appeared that for numerous vehicles you could get an "adapter harness" to be able to run an internally regulated alternator(s). It appeared to have some electronics in it to satisfy the PCM and prevent the light of MIL lights and codes. I didn't dig very deeply into it as it didn't really apply to us, but was curious. I had seen newer pickups with 3 and 4 alternators in them in pictures a wondered how they pulled that off.

When you get into electric vehicles with their own big battery packs, I would totally agree that isn't the place to mess with it, but on an AGM or lithium battery equipped RV, I would think it would be a very nice way to go. Especially for lithium, having 560 amps of alternator would certainly be make for quick charging, even if the only netted 330 amps continuous when hot and turned on and off with a Balmar(s). Even the voltage to the starting battery wouldn't be all that bad for doing lithium, as no most of the systems are looking at low to mid 14's volts for cutoff/continuous, which will be OK with a modern calcium lead starting wet cell.

[prfleming]

Originally Posted by avanti

4) The problem with using the OEM alternator to supplement a second engine alternator is that (as Booster said), the OEMs (at least MB) severely restrict the amount of current you may draw for external use. IIRC on the Sprinter it is 25A. Not enough to be worth the bother.

On another Sprinter forum the suggestion was this MB aux current limit was to protect their wiring, not a limit of the alternator itself. So, I'm wondering if you beefed up the alternator to battery cable, and ran your own heavy cable from there, could you then use more of the available current from the stock alternator?

[BBQ]

.

MB uses a "smart" alternator. It is controlled by the vehicle's computer.

In an effort stretch the fuel economy,
the computer will implement a charging strategy to
make the vehicle feel more powerful,
and uses less fuel at the same time.

The computer will turn off the alternator during stand-still starts. eg, at a traffic light.

The computer will turn off (or turn down) the alternator when the battery is full.

etc.,

[avanti]

No one is suggesting that it is physically impossible to get more current from a Sprinter. If you are willing to do enough hacking, pretty much anything is possible. But, you have to understand that modern alternators are part of very complex energy-management systems that involve many interacting subsystems. In addition to the example that BBQ gives, there are many other subtle actions that some of these systems take, including charging during coasting and braking, deliberately under-charging the battery at first to leave "room" for energy-harvesting during downhill coasts, an heaven knows what else. Although some of these techniques are well-known in the industry, not all of them are, and the OEMs do not generally disclose which of them are used in any given vehicle. Moreover, these behaviors are monitored by the ECU for proper component behavior, and it is difficult to predict whether the violation of some engineering assumption might trigger a CEL. For example, the ECU expects to be able to control charging rates by modulating alternator voltage. How are these algorithms affected by (in effect) adding a much larger battery to the system? who knows? Also, the Sprinter has a shunt mounted right on the primary battery terminal. Which side of this shunt should you tap into? I have no idea, but I guarantee that the system will behave differently depending on which side you choose. Anything can be gotten around, but it might be a lot trickier than it looks.

The actual reason why MB specifics a maximum current draw is that it provides an engineering specification to be used along with many others to model and specify these complex behaviors in a way that is guaranteed to work, as long as the assumptions are all met. Wire size is one of those specifications--there are many others. For these reasons, there is no real way to tell whether any given mod will keep the system happy or not. Best to follow the guidelines and be satisfied with adding a second alternator. As ARV has demonstrated, one add a mighty big alternator if it is really needed.

[cruising7388]

Originally Posted by prfleming

On another Sprinter forum the suggestion was this MB aux current limit was to protect their wiring, not a limit of the alternator itself. So, I'm wondering if you beefed up the alternator to battery cable, and ran your own heavy cable from there, could you then use more of the available current from the stock alternator?

The MB alternator has a cold rating in the whereabouts of 200 amps. Some low duty cycle systems like engine starting system can get away using undersized starter cables since 12 volt starters are actually wound to deliver specified torque at 9 volts. But with a continuous duty device like an alternator, you would think that good engineering practice would call for interconnects capable of supporting maximum amperage delivery.

Classical alternator regulators only looked at battery voltage, load demands and perhaps battery temperature to determine field winding current. The current generation of alternators still looks at these parameters but now also gets a number of additional instructions from the computer that affects regulator control of alternator field windings. Whether or not the currently designed engine alternators and regulator will cooperate when paralleled and add charging amperage to the coach charging system seems open to question particularly if the alternators are from different manufacturers.

Coachmen has implemented what they describe as a dual alternator bulk charging feature on their Li3 option and it would be interesting to determine how much suds the MB alternator is actually capable and willing to add to the charging mix and how it deals with appropriate charging to both lithium and lead acid batteries simultaneously.

[booster]

Even if they only took the approved 25 amps, it would be better than a 10% improvement over the approximately 165 amps you actually net over time with the Nations and a Baldor, so probably worth the effort when you talk about death spiral. Voltage control is got to be tough to handle, though, as if one is at a higher voltage, the other basically doens't contribute.

[cruising7388]

Originally Posted by booster

Even if they only took the approved 25 amps, it would be better than a 10% improvement over the approximately 165 amps you actually net over time with the Nations and a Baldor, so probably worth the effort when you talk about death spiral. Voltage control is got to be tough to handle, though, as if one is at a higher voltage, the other basically doens't contribute.

I've run some field tests that confirm what you say which is that when the charging sources are in voltage control, i.e. absorption charge mode, the load recognizes only the higher voltage source. I've never run a similar test for multiple sources in a current control, i.e. bulk charge mode, but the conventional wisdom is that during bulk charging, dual charging sources with disparate voltages are still are recognized by the load and are additive in total charging capacity. I imagine that even in bulk charging there is some limit to the voltage disparity permitted between two charging sources.

What I don't yet understand is how the dual alternator set up in the Galleria accomplishes the goal of increased total amperage for battery charging. What condition prevails when the Nations alternator is bulk charging and paralleled with the MB alternator which has no bulk charge mode and therefore is always in an absorption charging state? Interestingly, on the Galleria, when the Nations Balmar regulator shifts to absorption charging, it separates the alternators. I guess as a practical matter, that's not a shortcoming because at the point that the batteries are absorption charging, there is no longer any necessity for any amperage boost from the MB alternator.

The whole business with the smart Canbus alternator perplexes the hell out of me. The purported purpose is to increase engine efficiency and consequently mpg in the race toward meeting future CAFE standards. I get the concept of dropping any load when it isn't necessary, e.g, killing alternator field winding current when the computer sees a fully charged battery. But what savings are actually made? The load on the engine is a function of the watts delivered by the alternator. When batteries are fully charged the amperage delivery drops to a small level. Sure, a Canbus instruction to drop the alternator voltage might lower the alternator voltage
a volt or so, but does this drop the alternator load on the engine enough to go through this song and dance? It seems like an elegant solution that produces virtually non existent results.

[cruising7388]

Originally Posted by avanti

No one is suggesting that it is physically impossible to get more current from a Sprinter. If you are willing to do enough hacking, pretty much anything is possible. But, you have to understand that modern alternators are part of very complex energy-management systems that involve many interacting subsystems. In addition to the example that BBQ gives, there are many other subtle actions that some of these systems take, including charging during coasting and braking, deliberately under-charging the battery at first to leave "room" for energy-harvesting during downhill coasts, an heaven knows what else. Although some of these techniques are well-known in the industry, not all of them are, and the OEMs do not generally disclose which of them are used in any given vehicle. Moreover, these behaviors are monitored by the ECU for proper component behavior, and it is difficult to predict whether the violation of some engineering assumption might trigger a CEL. For example, the ECU expects to be able to control charging rates by modulating alternator voltage. How are these algorithms affected by (in effect) adding a much larger battery to the system? who knows? Also, the Sprinter has a shunt mounted right on the primary battery terminal. Which side of this shunt should you tap into? I have no idea, but I guarantee that the system will behave differently depending on which side you choose. Anything can be gotten around, but it might be a lot trickier than it looks.

The actual reason why MB specifics a maximum current draw is that it provides an engineering specification to be used along with many others to model and specify these complex behaviors in a way that is guaranteed to work, as long as the assumptions are all met. Wire size is one of those specifications--there are many others. For these reasons, there is no real way to tell whether any given mod will keep the system happy or not. Best to follow the guidelines and be satisfied with adding a second alternator. As ARV has demonstrated, one add a mighty big alternator if it is really needed.

Does Mercedes offer a dual alternator option of their own on the Sprinter?

[BBQ]

Originally Posted by cruising7388

Does Mercedes offer a dual alternator option of their own on the Sprinter?

They sell a bracket that mounts the 2nd alternator.

[Davydd]

Originally Posted by cruising7388

Does Mercedes offer a dual alternator option of their own on the Sprinter?

There is nothing in the build sheets but their offering the brackets to install a dual alternator. They have provisions for an auxiliary battery to run shop stuff and they imply that's all it's for on the single alternator. So, I suspect they have limited provisions on the primary alternator for that function. The Nations dual alternator fits the brackets. The Delco alternator that Advanced RV now uses had to have custom (ARV initiated) brackets installed.

You can download the 145 page Body and Equipment Guidelines for Sprinters that is published for upfitters. I haven't read the electrical requirements but it is all there. I downloaded it for the body do's and don't's.

[booster]

Originally Posted by cruising7388

I've run some field tests that confirm what you say which is that when the charging sources are in voltage control, i.e. absorption charge mode, the load recognizes only the higher voltage source. I've never run a similar test for multiple sources in a current control, i.e. bulk charge mode, but the conventional wisdom is that during bulk charging, dual charging sources with disparate voltages are still are recognized by the load and are additive in total charging capacity. I imagine that even in bulk charging there is some limit to the voltage disparity permitted between two charging sources.

What I don't yet understand is how the dual alternator set up in the Galleria accomplishes the goal of increased total amperage for battery charging. What condition prevails when the Nations alternator is bulk charging and paralleled with the MB alternator which has no bulk charge mode and therefore is always in an absorption charging state? Interestingly, on the Galleria, when the Nations Balmar regulator shifts to absorption charging, it separates the alternators. I guess as a practical matter, that's not a shortcoming because at the point that the batteries are absorption charging, there is no longer any necessity for any amperage boost from the MB alternator.

The whole business with the smart Canbus alternator perplexes the hell out of me. The purported purpose is to increase engine efficiency and consequently mpg in the race toward meeting future CAFE standards. I get the concept of dropping any load when it isn't necessary, e.g, killing alternator field winding current when the computer sees a fully charged battery. But what savings are actually made? The load on the engine is a function of the watts delivered by the alternator. When batteries are fully charged the amperage delivery drops to a small level. Sure, a Canbus instruction to drop the alternator voltage might lower the alternator voltage
a volt or so, but does this drop the alternator load on the engine enough to go through this song and dance? It seems like an elegant solution that produces virtually non existent results.

They are likely switching off the combined when they hit absorption because with lithium the batteries are going to be full anyway for all practical purposes. A lithium profile really doesn't have an absorption phase and is really just bulk and then off to be correct, no float either, from the latest we hear. As long as neither of the alternators is able to hold setpoint voltage, they both will be running full output, unless the MB electronics or Balmar turn them down for some reason, so as long as the Balmar is the highest setpoint, the MB should drop out first, before the Balmar switches to absorption or float. I have no idea how they could limit the output of the MB to 25 amps, though.