Newbie question on house battery voltage while driving

["007"]

Tom congrats on your new coach I hope your enjoying it because you have owned a Newmar before only it was gas.
Battery charging systems do not change that much between coach's gas or diesel.
Your batteries are charged two ways from a converter or from the alternator while driving.
This link has been around for a long time that explains the function of a BIRD or B.I.M. battery charging system and they are pretty much the same, its found in this sticky.

OWNER GUIDE

I notice some of your other questions on forum that your concerned about buttons on door or wall left side of driver that you had on your Canyon Star maybe not as many, did you ever hit one of them while driving?
Its possible but it will remind you to reposition your left arm while driving to avoid causing you a problem, so you can drive safely and enjoy your new coach.

All the information I provide people comes from COM_NET which you also have access too.

[pasdad1]

I believe since 2009 Newmar has used the battery isolation manager from precision circuits. Here are excerpts from Newmar documentation.

[Winepress]

Here is a troubleshooting sheet

[sartor]

Many thanks to 007, Pasdad1, and Winepress for your helpful replies/pointers. My apologies to the community for failing to have sufficiently reviewed some of the material in the "stickies" and at Com Net, as referred to me by 007, before asking some of my questions above. I guess I was just a bit overwhelmed and not really knowing where to start (didn't know what I didn't know)! :-)

Anyway, the information provided so far should be very helpful when I get back out to my coach (in storage), and run the suggested diagnostics. Will report back when I get a verdict.

Thanks!

Tom

[757driver]

To answer question 2 of your previous post you can rely on the displayed voltage on the Magnum remote IF and ONLY IF there is no load on the inverter (when not on shore power) OR there is no charge going to your house batteries (while on shore power). So in other words not very often.

Magnum did not install a dedicated voltage sense line for their installation so any load (charging or discharging) will skew the actual reading of the house battery bank.

[wolfe10]

Correct.


Voltage is only a good indicator of battery state of charge WITH THE BATTERIES AT REST (no charging and no discharging for at least an hour).


So, indeed, not very often.


Easy to prove how inaccurate voltage reading alone can be in reporting battery state of charge:



No shore power, no generator, using the inverter only, run the microwave for 2 minutes. Read voltage.


Do NOTHING else/run no 12 VDC loads and no generator of shore power, inverter turned OFF. Read voltage an hour later. It WILL be higher than immediately after running the load. Said another way, reading right after a heavy load will be falsely low.

[sartor]

Okay, finally got back to my coach (in storage, plugged into 50A service), and was able to do some more checking.

First off, I went through the Magnum Energy menus, and discovered that the "battery type" was set to "flooded." This seemingly in contradiction to the fact that my house batteries are 8x AGM batteries (specifically Mighty Bruin brand 8AGC2 batteries). But then this immediately raised a question in my mind: WHICH battery bank is being referred to by the Magnum Energy Remote Control: the house batteries, or the chassis batteries? I ask because my *chassis* batteries appear to be the flooded type. I couldn't actually manage to see exactly which brand/model of chassis batteries I have without actually removing them, but I was able to read the label enough to see that I have model 31-950 batteries, distributed by "Best Parts, Inc." Pretty sure those are normal/non-AGM, "flooded" batteries (2 of them).

I'm assuming that I should change the Magnum Energy settings to battery type = "AGM1," or perhaps "AGM2." The manual mentions a bunch of different brands for governing AGM1 vs. AGM2, but my brand of "Mighty Bruin" is not listed. Can someone please confirm for me?

As for the state of the batteries, with the motorhome having been sitting there stored and plugged in for almost two weeks, upon arrival I checked the indicator on the display that is above the driver's seat and immediately beneath the Magnum Energy Remote Control, and it showed house = 12.44V and chassis = 11.38V. Measuring with my meter at the batteries directly I got 12.56V/11.51V (and pretty consistently throughout my tests I got 0.13V higher with my meter at the batteries vs. the display above the driver's seat).

So it still seems to me that the chassis batteries are not getting "maintained" at at 12V or higher.

But now in trying to research further and reading through the manuals and the troubleshooting chart for the Battery Isolation Manager (BIM), I'm a bit puzzled. According to the troubleshooting chart, with ignition off and plugged into shore power (my situation), the solenoid relay only activates when chassis voltage drops below 12.6V (true) and house voltage is above 13.0V (false). But the specs for the Magnum Energy Remote seem to indicate that the whole function of the charger while plugged in is to *maintain* (via the "float charge") the house batteries at 12.5V. So if that's what the charger is doing (keeping the house batteries always around 12.5V), then they will never be high enough (13.0V or higher) to cause the BIM charge solenoid to actually activate, even after the chassis batteries have dropped below 12.6V.

So this seems to correspond to my situation: chassis batteries (upon my arrival at storage after two weeks) were all the way down to 11.38V, but since house batteries were still being properly maintained at 12.44V, the BIM charge solenoid wasn't charging the chassis batteries.

So I'm a bit confused. Perhaps this is all "as expected," and everything is working correctly?

One other thing to note: when I forced the Magnum Energy Remote into "equalize" mode, it immediately started pushing *both* the chassis and the house batteries up into the 14V range. I'm not sure whether or not this "proves" that the BIM solenoid relay must be activating. Does the Magnum Energy Remote *directly* provide this "equalize" voltage to both the house batteries and to the chassis batteries? Or does it rely upon the BIM solenoid relay to actually "connect" the equalize voltage from the house batteries to the chassis batteries? If the latter then this would seem to "prove" that the BIM solenoid relay is at least activating under "equalize" conditions.

I know I've still got some more diagnostics to do, but I'm hoping to get some more clarification from the community, so I can better understand what I'm observing.

Thanks!

Tom

[pasdad1]

Yes, you should set battery type to AGM1 or AGM2, (either of which is better than the flooded setting you have now).

The magnum only directly reads and charges the house batteries....it is the BIM which periodically connects house and chassis batteries together. Note the “periodically” part....this is supposedly so the chassis batteries do not overcharge when current is flowing with engine off....and alternator is not too taxed when engine is running.

AGM batteries have a higher resting voltage than flooded, so my theory is that the magnum charger is cutting off too soon thinking the house batteries are charged (and then it waits until voltage drops again before float charging again) This is keeping the BIM from connecting, leaving the chassis batteries very undercharged.

If you disconnect shore power and then reconnect in a few minutes, the magnum usually starts back in absorption mode (14.3v or so) and the BIM should again connect chassis+house together....you should be able to verify this by seeing 13+ volts on both sets of batteries.

[757driver]

Originally Posted by sartor

Okay, finally got back to my coach (in storage, plugged into 50A service), and was able to do some more checking.

First off, I went through the Magnum Energy menus, and discovered that the "battery type" was set to "flooded." This seemingly in contradiction to the fact that my house batteries are 8x AGM batteries (specifically Mighty Bruin brand 8AGC2 batteries). But then this immediately raised a question in my mind: WHICH battery bank is being referred to by the Magnum Energy Remote Control: the house batteries, or the chassis batteries? I ask because my *chassis* batteries appear to be the flooded type. I couldn't actually manage to see exactly which brand/model of chassis batteries I have without actually removing them, but I was able to read the label enough to see that I have model 31-950 batteries, distributed by "Best Parts, Inc." Pretty sure those are normal/non-AGM, "flooded" batteries (2 of them).

I'm assuming that I should change the Magnum Energy settings to battery type = "AGM1," or perhaps "AGM2." The manual mentions a bunch of different brands for governing AGM1 vs. AGM2, but my brand of "Mighty Bruin" is not listed. Can someone please confirm for me?

As for the state of the batteries, with the motorhome having been sitting there stored and plugged in for almost two weeks, upon arrival I checked the indicator on the display that is above the driver's seat and immediately beneath the Magnum Energy Remote Control, and it showed house = 12.44V and chassis = 11.38V. Measuring with my meter at the batteries directly I got 12.56V/11.51V (and pretty consistently throughout my tests I got 0.13V higher with my meter at the batteries vs. the display above the driver's seat).

So it still seems to me that the chassis batteries are not getting "maintained" at at 12V or higher.

But now in trying to research further and reading through the manuals and the troubleshooting chart for the Battery Isolation Manager (BIM), I'm a bit puzzled. According to the troubleshooting chart, with ignition off and plugged into shore power (my situation), the solenoid relay only activates when chassis voltage drops below 12.6V (true) and house voltage is above 13.0V (false). But the specs for the Magnum Energy Remote seem to indicate that the whole function of the charger while plugged in is to *maintain* (via the "float charge") the house batteries at 12.5V. So if that's what the charger is doing (keeping the house batteries always around 12.5V), then they will never be high enough (13.0V or higher) to cause the BIM charge solenoid to actually activate, even after the chassis batteries have dropped below 12.6V.

So this seems to correspond to my situation: chassis batteries (upon my arrival at storage after two weeks) were all the way down to 11.38V, but since house batteries were still being properly maintained at 12.44V, the BIM charge solenoid wasn't charging the chassis batteries.

So I'm a bit confused. Perhaps this is all "as expected," and everything is working correctly?

One other thing to note: when I forced the Magnum Energy Remote into "equalize" mode, it immediately started pushing *both* the chassis and the house batteries up into the 14V range. I'm not sure whether or not this "proves" that the BIM solenoid relay must be activating. Does the Magnum Energy Remote *directly* provide this "equalize" voltage to both the house batteries and to the chassis batteries? Or does it rely upon the BIM solenoid relay to actually "connect" the equalize voltage from the house batteries to the chassis batteries? If the latter then this would seem to "prove" that the BIM solenoid relay is at least activating under "equalize" conditions.

I know I've still got some more diagnostics to do, but I'm hoping to get some more clarification from the community, so I can better understand what I'm observing.

Thanks!

Tom

Tom,

The way your Magnum remote is set up what your are seeing is perfectly normal. Your Magnum remote is primarily for charging your house batteries.

The settings you need to change for your AGM batteries are:

1. Change battery type to AGM2.

2. Set your charge rate to 90%.

3. Set your Absorb time to 3.5 hours.

4. Set your final charge setting to Float.

The final charge setting which is most likely set to multi is the reason that your chassis batteries are so low. In this position it will only give a float voltage to your house batteries when they drop below approximately 12.6v and then only for a 4 hour period. The voltage most likely does not get high enough to provide much if any charge to your chassis batteries. When your chassis batteries are getting a charge they will only receive it for 1 hour at a time.

One final note most AGM batteries cannot be equalized so do not put them into equalize mode.

[sartor]

Thanks so much to all for the replies, and especially to 757driver for the detailed suggestions on the settings. I'd been wondering about them as well.

Here's what the settings WERE set to, with the new settings from 757driver in parens at the end):

Battery type: flooded (will change to AGM2)

Charge rate: 80% (will change to 90% as per 757driver)

Low battery cutoff (LBCO): 10.0V (should I change this?)

Absorb time: 1.5H (will change to 3.5H as per 757driver)

VAC dropout: 80VAC (should I change this?)

Final charge: multi (will change to Float as per 757driver)

The big clue to me that the prior owner probably hadn't set any of this up correctly was the fact that the battery type was set to "flooded" even though AGM batteries were installed.

Thanks again to the community!

Tom

[C.Martin]

LBCO: 10v ???

LBCO is a tool to buy you time. In other words...the normal charging system hasn’t worked, and now you are draining your batteries. Fact of the matter is...you drain them faster with the inverter ON, than inverter OFF. So LBCO can be set to turn off the inverter to slow down the discharge, and hopefully buy you time to take corrective action before killing the batteries. 10.5v is considered dead. I wouldn’t recommend setting it below that...because it won’t do anything really to help. I adjust LBCO depending on use. If I know that I am using the coach, and boondocking...by morning my batteries are going to be down around 75% with newer batteries. After espresso...70%. Turning on a microwave or coffee maker will cause the voltage to dip...and since I am taking responsibility for the batteries...and do not want the inverter to trip off and ruin my coffee...I set the LBCO down around 11.2 v. On the other hand...if a I have shore power, and I’m not really closely watching the batteries like I would when boondocking. Then i am not expecting the voltage to drop much. I will set it up higher to give me an early warning of an unexpected situation. Say 12.3v if using the microwave...if not using high draw inverter powered appliances...maybe 12.5v. It is just a tool. No hard and fast rule. Use it to tell you what is going in with your coach, and based in your attention level...set it to prevent a deep depth of discharge in your batteries.

Absorb time...Magnum uses time as one method. And they have a chart in the ME-RC manual to figure out the time based on the aH capacity of your bank. On the other hand battery manufacturers and other Inverter makers usually go on a sliding scale. It is based on the battery voltage when charging began, or depth of discharge. Lifeline has a chart based on depth of discharge ranging from 2hrs for shallow discharge up to 4hrs for deeper discharges. Victron’s solar charge controller looks at the bank voltage when the charger wakes up with the rising sun...and adjust the length of charge based on that. The advanced Magnum remote will let you set “tail current”. Absorb is considered complete when the charging amperage reaches the recommended percentage of battery bank capacity...

As 757Driver recommended...the multi is normally used when you have other charge sources...like solar. If it’s just your Magnum Inverter doing the work...Float is better.

[757driver]

Originally Posted by sartor

Thanks so much to all for the replies, and especially to 757driver for the detailed suggestions on the settings. I'd been wondering about them as well.

Here's what the settings WERE set to, with the new settings from 757driver in parens at the end):

Battery type: flooded (will change to AGM2)

Charge rate: 80% (will change to 90% as per 757driver)

Low battery cutoff (LBCO): 10.0V (should I change this?)

Absorb time: 1.5H (will change to 3.5H as per 757driver)

VAC dropout: 80VAC (should I change this?)

Final charge: multi (will change to Float as per 757driver)

The big clue to me that the prior owner probably hadn't set any of this up correctly was the fact that the battery type was set to "flooded" even though AGM batteries were installed.

Thanks again to the community!

Tom

Tom,

Charlie gave some good information on the two different uses of LBCO. For in use 10.8-11.0v is fine. Where it’s at is too low.

VAC dropout should be set at 90VAC.

[sartor]

Resuming this thread, which I started a couple months ago, before learning a lot more about the Magnum Energy equipment. I'm a little uncertain as to whether or not "resuming an old thread" is effective within the irv2 forums, but I'll give it a shot.

Note that since having started this thread, I also started another, semi-related thread with the title "Benefit of BMK, and problem with chassis batteries discharging." Here's the link:

https://www.irv2.com/forums/f103/ben...ng-520781.html

To summarize the relationship between this thread and the other one, my original issue was I noticed that my house batteries were not being kept charged while driving. Then my second issue (on the other thread linked above) was I had the "opposite" problem, where my chassis batteries were not being kept charged while plugged in at my storage facility.

Long story short, my issue got resolved on the other thread, and was all traced to a defective battery temperature sensor (BTS). The bad BTS was preventing my charge solenoid from closing while plugged in, so the shore power was not charging the chassis batteries. The (temporary) solution to that problem was simply to *disconnect* the bad BTS. This forced the Magnum Energy unit (ME-RC) to "default" the battery temperature to 77 degrees, thus allowing the ME-RC to close the charge solenoid and keep the chassis batteries charged.

My reason for posting now again to this original thread is that I *still* seem to have the problem with the *house* batteries not being kept charged while driving. If I drive say 5-6 hours, with the chassis batteries being kept charged by the alternator at roughly 13.5V or so, I see the house batteries slowly drop from an initial charge of say 12.5V down to maybe 11.9V upon arrival.

So my *guess* is that for some reason the charge solenoid is not closing while I'm driving. This despite the purported spec of the charge solenoid (battery isolation manager -- BIM) indicating that the solenoid should close (and charge the house batteries) while driving, with the following combination of conditions:

1) Ignition on (of course, since I'm driving)
2) Chassis batteries above 13.2V (true; due to alternator)
3) House batteries below 12.6V (eventually true, as they drop while driving)

So the key open question is why are my house batteries not being kept charged while driving? Does it make sense that for some reason the charge solenoid is *not* closing under these intended conditions, despite the fact that the charge solenoid *is* now working in the reverse condition, when plugged in and house batteries high/chassis batteries low?

Does anyone think it's possible that unplugging the defective BTS (and thus telling ME-RC the "default" temp of 77 degrees) *would* fix the problem of keeping the chassis batteries charged while plugged in, but would still *not* fix the problem of keeping the house batteries charged while driving?

I guess to cut to the chase I'm looking for suggestions of how to diagnose the continued problem of my house batteries not being kept charged while I'm driving.

Thanks for any help!

Tom

[757driver]

Originally Posted by sartor

Resuming this thread, which I started a couple months ago, before learning a lot more about the Magnum Energy equipment. I'm a little uncertain as to whether or not "resuming an old thread" is effective within the irv2 forums, but I'll give it a shot.

Note that since having started this thread, I also started another, semi-related thread with the title "Benefit of BMK, and problem with chassis batteries discharging." Here's the link:

https://www.irv2.com/forums/f103/ben...ng-520781.html

To summarize the relationship between this thread and the other one, my original issue was I noticed that my house batteries were not being kept charged while driving. Then my second issue (on the other thread linked above) was I had the "opposite" problem, where my chassis batteries were not being kept charged while plugged in at my storage facility.

Long story short, my issue got resolved on the other thread, and was all traced to a defective battery temperature sensor (BTS). The bad BTS was preventing my charge solenoid from closing while plugged in, so the shore power was not charging the chassis batteries. The (temporary) solution to that problem was simply to *disconnect* the bad BTS. This forced the Magnum Energy unit (ME-RC) to "default" the battery temperature to 77 degrees, thus allowing the ME-RC to close the charge solenoid and keep the chassis batteries charged.

My reason for posting now again to this original thread is that I *still* seem to have the problem with the *house* batteries not being kept charged while driving. If I drive say 5-6 hours, with the chassis batteries being kept charged by the alternator at roughly 13.5V or so, I see the house batteries slowly drop from an initial charge of say 12.5V down to maybe 11.9V upon arrival.

So my *guess* is that for some reason the charge solenoid is not closing while I'm driving. This despite the purported spec of the charge solenoid (battery isolation manager -- BIM) indicating that the solenoid should close (and charge the house batteries) while driving, with the following combination of conditions:

1) Ignition on (of course, since I'm driving)
2) Chassis batteries above 13.2V (true; due to alternator)
3) House batteries below 12.6V (eventually true, as they drop while driving)

So the key open question is why are my house batteries not being kept charged while driving? Does it make sense that for some reason the charge solenoid is *not* closing under these intended conditions, despite the fact that the charge solenoid *is* now working in the reverse condition, when plugged in and house batteries high/chassis batteries low?

Does anyone think it's possible that unplugging the defective BTS (and thus telling ME-RC the "default" temp of 77 degrees) *would* fix the problem of keeping the chassis batteries charged while plugged in, but would still *not* fix the problem of keeping the house batteries charged while driving?

I guess to cut to the chase I'm looking for suggestions of how to diagnose the continued problem of my house batteries not being kept charged while I'm driving.

Thanks for any help!

Tom

Tom,

With your house batteries below 12.6v unplug from shore power and start the engine. If your alternator charge is passing through the BIM to the house batteries you should see a voltage rise either with a DVM at the batteries or on your Magnum remote panel up in the area of 13.5v.

Also keep in mind that your Precision Circuits BIM only charges your house batteries from the alternator for 1 hour and then shuts off. Once the house batteries drop to less than 12.6v it will charge again for 1 hour.