Any battery experts in here?

Scott Malkinson wrote:
The charger acts like an isolator. It's a battery to battery charger.

No it isn't. You probably have an actual isolator relay/solenoid.

It may only connect the house batteries to the alternator after the starting battery comes up to a certain point but it is NOT charging one set of batteries by discharging the other.

It is very likely that you should not even be LOOKING AT your "battery monitor" panel while the truck engine is running. It was designed to be useful ONLY WHEN CONNECTED TO SHORE POWER.

Scott Malkinson wrote:
Ok thanks. I'm not going to get a new one or anything. It charges the batteries %100 if I go on a long drive, which I do plenty of. I was just trying to make some sense of how this thing works.

Are you determining full off of the Xantrex monitor? If so, you have to be certain to have the fully charged parameters set properly, and not just go by time, amp hours, or voltage. Most I have seen have not been set correctly. The amps to the coach battery are the by far the best indicator, and depending on your battery brand and type and the setting can vary a lot.

A full charge on a 50% down battery will usually take 6 to 8 hours, minimum, if the charger has enough capacity to give it all it will accept, so you have to drive a lot. You can fairly quickly get to 70-80% but the rest is very slow for lead acid batteries, both AGM and wet cells.

Ok thanks. I'm not going to get a new one or anything. It charges the batteries %100 if I go on a long drive, which I do plenty of. I was just trying to make some sense of how this thing works.

Scott Malkinson wrote:
The charger acts like an isolator. It's a battery to battery charger. Promariner digital mobile charge 40. It monitors the starting battery and gives it priority. Once the starting battery is above the required volts it starts to charge the house batteries. Battery monitor is a xantrax linklite.

I just grabbed a quick look at the manual for the Promariner, and honestly, I think you will have trouble figuring out what it is up to at any given time, as it is constantly looking at things, primarily on the starting battery, and going on and off, up and down stages based on that voltage.

I also don't know how they can use the voltage of the starting battery to control anything because it is connected to the alternator and will be controlled by it's internal regulator. When the engine is running, it should always show charging voltage on the starting battery, which in vehicles is typically in the low 14s volts, but may be lower at high 13s volts.

From the description, it sounds like they are tailoring the charger to a small marine alternator, that will get dragged down by a 40 amp load, and likely is set to run at 13.8v or so. In a vehicle, you will have much higher current available, so it won't get the voltage dragged down by a 40 amp load, so all the prioritizing of batteries based on charge rates and the starting battery voltage gets to be a mute point, and probably causing more problems than solving them.

If my assumptions are correct, this may not be the best charger for your system. I am a fan of battery to battery chargers, but most of them I have looked at operate differently, it appears.

Basically, as you have plenty of amps available from the alternator, you should see charge voltage and the charger maxed out whenever the engine is running and either of the batteries is low. That voltage will be whatever the internal regulator in the alternator (or vehicle ECU) chooses for the starting battery, and whatever the charger chooses for the coach battery. The amp split will depend on how much they will accept relative to each other.

How long that charge voltage stays on each battery will depend on how the alternator regulator or the ECU turn down, or not, for the starting battery, and what the charger thinks is right for the coach battery based on it's internal algorithm for time. Since the charger is not connected to the monitor shunt, it will have really no accurate idea of the amps to the battery, and it didn't appear it will even know how big the battery is, so how good the charging actually is for getting the battery full without overcharging will likely not be stellar.

I think I would call Promariner and see what they say, although they likely will say all is good and don't worry about it (typical response by charger companies of all stripes). You could also call someone like Sterling and describe what you want to do, and see what they say about it, and how their products would handle it and be monitored.

It is a tough one to figure out what is going on without seeing it in person, and even seeing it might not shed much light with it's constant changing of parameters.

The charger acts like an isolator. It's a battery to battery charger. Promariner digital mobile charge 40. It monitors the starting battery and gives it priority. Once the starting battery is above the required volts it starts to charge the house batteries. Battery monitor is a xantrax linklite.

Scott Malkinson wrote:
Ok, so I got my batteries set up and everything. Ended up pulling the console and puttiing them there with a custom console over it. But I'm not quite understanding how the charging works. I've got 2 155 amp hour agm batteries and the pro mariner 40 amp charger and a xantrax monitor.

I've got lights, tv and mini fridge all hooked up running on a 1000 watt inverter. All works fine, but the charging part is baffling me. From what I've learned, the charger charges in "fast charge" mode until it gets over 12.8 volts then kicks into "absorption" charge.

Yesterday I got it down to about 12.2-12.3 volts. I drive down the highway for over 2 hours before the absorption charge kicked in. About half hour after that kicked in I had to stop but left it running. The volts were 13. Started driving again, and not 5 minutes after driving the absorption charge stopped and volts dropped down to 12.5. Had to stop again, this time I turned the engine off. When I started it back up the volts shot up to 12.9 and the absorption charge kicked back in.

Got to my spot for the night about 10 minutes later and shut her off. Just fired it back up like an hour ago and volts went up to 12.9 again and absorption change kicked in. Then after it idled for a bit the volts dropped back down to 12.5.

Been idleiing for over an hour and the volts are at 12.6. There are times when I will drive just in town for an hour or so and the volts will actually be .1 lower than when I left, and the inverter isn't even on. Sorry to be so long winded, but I don't know **** about this and I'm confused as hell. Can any experts shine some light on this?

All those voltages look low for running off the engine charging system, unless you have an isolator (not a relay type separator in the circuit), and even then are low.

The charger and inverter would not normally be in the circuit at all, unless you are running the charger off the inverter off the engine alternator, which can add a lot of inefficiencies to all of it.

Most chargers, if you are running off the charger, do a pretty poor job of charging batteries to full, and if you are turning them on and off repeatedly, they can get very confused due to surface charge and loads.

Your readings all over the map are likely caused by surface charge being on and then going away over time, and/or the charger, if you are using it while driving, seeing surface charge and going directly to float.

I think we need to know how you are wired for charging, especially while driving, and the model numbers of the parts used, so we can try to understand what is going on.

Scott Malkinson wrote:

Yesterday I got it down to about 12.2-12.3 volts. I drive down the highway for over 2 hours before the absorption charge kicked in.
Got to my spot for the night about 10 minutes later and shut her off.

You are missing one critical point here.

There are TWO charging systems available here.

One which works when plugged into AC shore power.....which is the main use of the "monitor" panel. This system was NOT in use at any time during your "story" as near as I can tell. That system is usually called the "converter/charger".

The other system is the one in the "truck" attached to the engine.
It works completely independently from the "house" system and has it's own parameters. The voltage regulator built into the engine alternator controls the charging voltage while the engine is running. It may react entirely differently than the "shore power" charging.

I don't see anything really bad about your story.......
EXCEPT: Running the truck engine is NOT the best way to charge your batteries. Plugging into shore power is best; running a generator, which is a substitute for shore power is second best. Running the truck engine is dead last.

And a small note: Any time the engine is running and you see a voltage below 12.6, there might be a problem with the engine alternator and it should be checked out.

Ok, so I got my batteries set up and everything. Ended up pulling the console and puttiing them there with a custom console over it. But I'm not quite understanding how the charging works. I've got 2 155 amp hour agm batteries and the pro mariner 40 amp charger and a xantrax monitor.

I've got lights, tv and mini fridge all hooked up running on a 1000 watt inverter. All works fine, but the charging part is baffling me. From what I've learned, the charger charges in "fast charge" mode until it gets over 12.8 volts then kicks into "absorption" charge.

Yesterday I got it down to about 12.2-12.3 volts. I drive down the highway for over 2 hours before the absorption charge kicked in. About half hour after that kicked in I had to stop but left it running. The volts were 13. Started driving again, and not 5 minutes after driving the absorption charge stopped and volts dropped down to 12.5. Had to stop again, this time I turned the engine off. When I started it back up the volts shot up to 12.9 and the absorption charge kicked back in.

Got to my spot for the night about 10 minutes later and shut her off. Just fired it back up like an hour ago and volts went up to 12.9 again and absorption change kicked in. Then after it idled for a bit the volts dropped back down to 12.5.

Been idleiing for over an hour and the volts are at 12.6. There are times when I will drive just in town for an hour or so and the volts will actually be .1 lower than when I left, and the inverter isn't even on. Sorry to be so long winded, but I don't know **** about this and I'm confused as hell. Can any experts shine some light on this?

Scott Malkinson wrote:
Any battery experts in here?

He just left.

Ok, thanks guys. I think I can clear room inside to mount them. Just sounds like the better option.