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Discussion Starter #1
I've been unable to find any info on how the AGM battery is recharged. I would hope that its a multi stage recharge considering the cost of an AGM battery.

This is also of concern when considering adding an additional battery- I do not have the additional battery under the drivers seat. The Metris equipment book states than only an identical AGM battery can be added to the system, which is logical since it could use the recharging profile that is designed for the orginal battery.
 

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I've been unable to find any info on how the AGM battery is recharged. I would hope that its a multi stage recharge considering the cost of an AGM battery.

This is also of concern when considering adding an additional battery- I do not have the additional battery under the drivers seat. The Metris equipment book states than only an identical AGM battery can be added to the system, which is logical since it could use the recharging profile that is designed for the orginal battery.
According to the the Equipment Book, the batteries are tied in parallel by the cutoff relay when the engine is running: "the relay is installed on the charge line to the auxiliary battery. It separates the starter battery consumers from the auxiliary battery consumers. When the engine is running, the relay allows both batteries to be charged or discharged simultaneously."
 

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Discussion Starter #3
Gottlieb- Thanks for the response. It answers part of my question- that the aux battery is separated from the start battery by the relay when the engine is off. At least that is implied and what one would expect.

Its seems odd that both batteries are charged simultaneously. Normally the start battery gets priority and once it reaches a certain voltage the majority of the alternator's current flows to the aux battery.
 

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I've been unable to find any info on how the AGM battery is recharged. I would hope that its a multi stage recharge considering the cost of an AGM battery.

This is also of concern when considering adding an additional battery- I do not have the additional battery under the drivers seat. The Metris equipment book states than only an identical AGM battery can be added to the system, which is logical since it could use the recharging profile that is designed for the orginal battery.
According to the the Equipment Book, the batteries are tied in parallel by the cutoff relay when the engine is running: "the relay is installed on the charge line to the auxiliary battery. It separates the starter battery consumers from the auxiliary battery consumers. When the engine is running, the relay allows both batteries to be charged or discharged simultaneously."
Gottlieb- Thanks for the response. It answers part of my question- that the aux battery is separated from the start battery by the relay when the engine is off. At least that is implied and what one would expect.

Its seems odd that both batteries are charged simultaneously. Normally the start battery gets priority and once it reaches a certain voltage the majority of the alternator's current flows to the aux battery.
I have a thread here and hope you guys have an answer.

Do you have a way to charge all four batteries when engine is not running?
 

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Discussion Starter #6
My question concerns HOW the main or start battery is charged, not how often.

Batteries, especially deep cycle batteries, have appreciably longer lives if they are charged correctly. A good multi stage charger goes use a bulk charge, an absorption charge and finally a trickle charge. It also adjusts for temperature. I plan on adding an additional battery but would like to know how the alternator goes about the business of recharging the main battery. Most likely its a simple two stage charge, bulk and then trickle. If that is the case, I'd consider using a battery to battery charger or other type of charger for the additional deep cycle battery.

I guess I'll have better luck on the Sprinter forum with this question.
 

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My question concerns HOW the main or start battery is charged, not how often.

Batteries, especially deep cycle batteries, have appreciably longer lives if they are charged correctly. A good multi stage charger goes use a bulk charge, an absorption charge and finally a trickle charge. It also adjusts for temperature. I plan on adding an additional battery but would like to know how the alternator goes about the business of recharging the main battery. Most likely its a simple two stage charge, bulk and then trickle. If that is the case, I'd consider using a battery to battery charger or other type of charger for the additional deep cycle battery.

I guess I'll have better luck on the Sprinter forum with this question.
the Metris charging system is not like your typical 3-stage deep cycle battery charger. But the Metris computer system does regulate charging amps to the main battery, and any aux connected to it.
 
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The Metris charging system uses a smart alternator which only charges the battery when needed, preferring to reclaim excess power during braking and downhill coasting, sort of like the regen system in a hybrid. Actually, if I recall, GM briefly tried to market a similar system as a "mild hybrid". It isn't.

You can watch the system in action if you have steering wheel buttons. On the main screen, scroll down to "instant fuel economy". Under normal operation, the graph tells you how much fuel the car is using.

When you reach a circumstance where the car will maintain speed without throttle input, the bar goes to the first line on the right, which tells you the fuel injectors have been shut off (I.e. The engine is turning but it is not burning any fuel).

When the kinetic energy of the car exceeds that of the intended speed (such as mild breaking or heavy down hill) the car begins to use the rotational energy of the unfueled engine to charge the battery, shown by the graph going past that line and into the "charge" section.

The alternator only engages in direct charging when the battery falls to an insufficient level.
 

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My question concerns HOW the main or start battery is charged, not how often.

Batteries, especially deep cycle batteries, have appreciably longer lives if they are charged correctly. A good multi stage charger goes use a bulk charge, an absorption charge and finally a trickle charge. It also adjusts for temperature. I plan on adding an additional battery but would like to know how the alternator goes about the business of recharging the main battery. Most likely its a simple two stage charge, bulk and then trickle. If that is the case, I'd consider using a battery to battery charger or other type of charger for the additional deep cycle battery.

I guess I'll have better luck on the Sprinter forum with this question.
I'm also interested in this question, please let us know what you find out. It sounds like the Metris has the dreaded "Smart Alternator" problem (sterling-power.com/pages/regen-braking), which apparently means potentially incomplete charging of the house battery with attendant shortened lifespan. Also I remember seeing a note in one of the up fitter guides indicating that house batteries have to be limited to a 40A charging rate, which might be too low for anything but a small bank (tried to find again but couldn't). Maybe your idea of a battery-to-battery charger is the way to go?

Also it looks like the new Sportsmobile Metris Terracamper requires the extra battery option. Maybe we'll be able to get some real-world feedback sometime soon.
 

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My Metris came with the auxiliary battery. Not something I was specifically looking for, but since it is there, I would like to know how to utilize it. I asked the service advisor and all he told me was stuff that didn't make any sense like "it's not a regular sized battery, it's like a motorcycle battery." I know that is not true because I took the cover off and looked! It is an exact twin of the one under the passenger seat. I told him that but still did not get any reasonable response.
My question: Is the auxiliary battery connected to the electrical system and accessed all the time by the system? The owners manual is not clear on this. It talks about the aux battery and the 12V outlets in the rear, but nothing specific enough. I'm out in the field at dog shows--dock diving, lure coursing, field training etc.--and would like to know if I could plug in things like a fan, 12V cooler, etc. and not run down the primary battery. I don't want to try it and get stranded with 2 dead batteries. Does anyone know?
 

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My question: Is the auxiliary battery connected to the electrical system and accessed all the time by the system? The owners manual is not clear on this. It talks about the aux battery and the 12V outlets in the rear, but nothing specific enough. I'm out in the field at dog shows--dock diving, lure coursing, field training etc.--and would like to know if I could plug in things like a fan, 12V cooler, etc. and not run down the primary battery. I don't want to try it and get stranded with 2 dead batteries. Does anyone know?
See post #2.
 

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The small battery the service advisor was talking about is for the Eco -start option. My service manager didn't know anything about the Aux battery either.


The Aux batter, under the drivers seat is not hooked up to any of the vans electronics. It is hooked to the starter(primary) battery so it can be charged with the starter batter, but is not discharged unless you hook electronics to it. As far as I know all of your van's 12v plugs are hooked up to the starter(primary) batter, so yes, you will drain the starter battery if you use them all day at a show. I had a new 12v plug and the roof fan installed and hooked directly to the aux battery. That way, I can run down the aux batter, and still be able to start the van. It wouldn't be a bad idea to get one of those portable jump start batteries to carry with you on trips too. I killed my primary battery once at a show by playing the radio and opening and closing my doors all day.
 

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Keep in mind that the starter battery is designed to self protect- that is to say, it tends to shut off draws when it starts reaching levels where it questions it's ability to perform its primary function (starting the engine).
 

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That helps. So what I need to do is get someone (this is definitely beyond my skill set)---an RV place perhaps--to install a couple of 12V plugs directly to the auxiliary battery and then I can use just those outlets for any accessories when parked. The relay switch will prevent the primary battery from running down and the auxiliary battery will be re-charged when the engine is running.
 

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Discussion Starter #16
The aux battery under the drivers seat is charged through a battery isolator so that when you power accessories powered by the aux battery while the vehicle is NOT running, the start battery is not drained. When the vehicle is running, it shouldn't matter as the alternator should be producing enough power to run everything.
 

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So I did some road testing today to test the 'smart charging' regen system and sure enough, it's IMO inadequate to support an aux battery. Maybe if you're ok with long driving periods in between a deep discharge or ...most notable... never having a 100% State of Charge (SoC) on either battery. Just as Sterling has said in their literature these systems are not designed to charge the battery to 100%. I measure my start battery at 12.39 before heading out. The system ramps up to 14.89 v and once the engine has reached op temps it will drop to 13v-ish range, and once you driving, say at any highway speeds, the volt meter reads anywhere from 12.3 - 12.5 v and boost up to 14.8x v during coasting or braking. After a highway/rural 15 min drive it measured just 12.5 v with ignition off once I got back. Wow. Easy to watch in the dash 'fuel consumption' when the bar passes into the Charge range. I don't have the factory 2nd batt option, so unless the 'isolator' in between also regulates a steady charging profile for the 2nd batt (which I'm sure it doesn't) the aux will never be charged to 100% and therefore any serious use will not be most performance and suffer a shorter life span. I'll be running a 3-12v 315Ah bank in my Metris and I may have to look into a good DC-to-DC multistage charger. As I see it, the charger cost should pay for itself in battery life span.
 

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Mowo, I have the Metris second battery and am considering installing a third one using a dc to dc charger from the second battery. If the second battery does not charge completely (because of the Metris smart charging system), does the dc to dc charger somehow boost the voltage, so the the third battery would get charged properly?
 
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