Battery charging

[Boxster1971]

Originally Posted by lewster

....
Your generator run time will depend on the amperage output of your charger and the state of discharge of your batteries. ....
.... Exceeding the run time is no problem as the Magnum will go to a 13.2 VDC float charge when they are full. It is far worse to undercharge them by not completing the charge cycle.

Questions?

Class dismissed! :-))

Lew Farber

Lew - excellent point on undercharging. This is why you must use either the generator or external AC power to get the Magnum to properly charge the coach batteries. Neither the Airstream installed solar or the Mercedes alternator will get the Lifeline coach batteries to full charge. It is an inherent design weakness IMHO.

If you want to dry-camp without having to use the generator add more solar with a proper charge controller.

[nesoutlook]

Ok, we now have a better understanding how the alternator, shore, generator and both chassis and house batteries interact together with the BIM. However, we are still not sure what the airstream solar does if anything. Let's assume we add enough solar (200 to 300 watts). Now what. If I am plugged in to shore power, does the BIM use the shore power and/or the solar power to charge all batteries. Does the power source with the most amps dictate what source is used to charge both batteries? Also, say it's a sunny day and the solar is providing 10 amps or more. Is that enough to charge chassis and house batteries on its own?


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[toskeysam]

That depends upon your solar controller. The stock controller on my 2013 Ext is a shunt controller. It will not come on until battery voltage drops below set point (12.6v for me). I thought my solar was not working until i read the manual AND then let the voltage drop until it kicked in...it works.


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[73shark]

I was told by Airstream that my solar controller kicks in when the battery voltage drops to 12.45 volts.

[lewster]

Originally Posted by nesoutlook

Ok, we now have a better understanding how the alternator, shore, generator and both chassis and house batteries interact together with the BIM. However, we are still not sure what the airstream solar does if anything. Let's assume we add enough solar (200 to 300 watts). Now what. If I am plugged in to shore power, does the BIM use the shore power and/or the solar power to charge all batteries. Does the power source with the most amps dictate what source is used to charge both batteries? Also, say it's a sunny day and the solar is providing 10 amps or more. Is that enough to charge chassis and house batteries on its own?


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Depends on what solar charge controller you have, if you are parked with the engine off and 'plugged in' with direct sunlight exposure for your solar panels and the state of charge of your batteries.

With 200-300 watts of solar thru the Blue Sky 2512iX-HV controller and a Magnum MMS-1012 inverter/charger, we have seen the inverter essentially 'yield' to the solar. The voltage sensor of the inverter 'sees' the charging voltage from the solar controller and 'thinks' that the batteries are full, since the solar controller is set for 14.3 VDC bulk/absorb charge and 13.2 VDC float and is wired directly to the batteries thru an appropriate over current device.

The Magnum remote will show 'float charge' but at zero amps......which essentially means it is in standby mode. If you have sufficient solar radiance on your panels and say.....you are running a large DC amperage draw that is still drawing from your battery bank even with the solar charge addition, then the Magnum should kick in at around 75-80% state-of-charge (SOC) and begin it's charging routine.

Haven't tested this scenario yet, as most of the solar I install manages to 'keep up' with the amperage draws placed on the batteries in full sun.

Another aspect of the Blue Sky solar charge controllers is the variability of the output charge to the batteries, which changes depending on the SOC of the batteries. If the batteries are near or nearing full charge, the amperage will taper off to a value of 0.5VDC per each 100 amp/hours of battery bank capacity, but if you place a DC load on the batteries, it will increase the amperage from the controller to the batteries to maintain the state of charge, or continue with it's charging algorithm.

Did that help or confuse???

[nesoutlook]

Lew, how does all this electrical talk maintain my chassis battery?


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[lewster]

The Precision Circuits BIM is a 'smart' device that interconnects the chassis and engine batteries when certain set of parameters are met, and disconnects them for others.

According to the company literature, if one of your batteries is receiving charge, the solenoid will close to join the two battery banks together. If the BIM sees long term charging of both batteries, it will allow both battery banks to remain connected and allow the charging system to do it's job.

Once the batteries are fully charged and have reached the 'float' state for one hour, the BIM will open the solenoid and isolate the batteries to prevent overcharging. It will only re-connect the two battery banks for charging if one of the batteries drops to approx. 80% of it's capacity, based on battery voltage.

If the batteries are not being charged, the BIM isolates the two batteries to prevent one system from depleting the other system.

In your case, if you have your solar or Magnum operating to charge the batteries, the two systems will be linked together until BOTH systems are full and in float charge for an hour, when the batteries are again isolated and are separate. This will also work if you are driving after dark (no solar) and your Magnum is not charging the batteries (no generator) but the engine is running and the alternator is charging the engine battery. The BIM will again link the two battery banks until BOTH are full and have been in float mode for 1 hour and will then disconnect them again.

It works in either direction.

[nesoutlook]

I thank everyone for their help. My understanding of the RV's electrical system has improved 500% in the last few days. Knowing what to expect from the RV makes the unknown of my future travels not as intimidating.



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[Brucet45410]

Originally Posted by lewster

No apologies required!!!!

Your generator run time will depend on the amperage output of your charger and the state of discharge of your batteries. If you have the Magnum MMS-1012, it has a 50 amp charging section, which has an adjustable output.

The next variable is the size of your battery bank. Typically, Lifeline AGM batteries use the C/5 rule. That takes the Capacity of your batteries and divides by 5.

If you have the standard 180 hour Lifeline bank, then your preferred charger output is 180/5 or 36 amps. The closest you can set the Magnum is 40 amps or an 80% charge rate.

Next, determine your state of charge level. This is easily done by reading the resting voltage of your batteries. Let's say that they read 12.2 VDC, which is 50% for Lifelines, so at that level you will need to replace 80 amp/ hours into your batteries. At the charge rate of 40 amps from above, you would need to run the generator about 2 hours to fully re-charge your batteries.

Exceeding the run time is no problem as the Magnum will go to a 13.2 VDC float charge when they are full. It is far worse to undercharge them by not completing the charge cycle.

Questions?

Class dismissed! :-))


Lew Farber
RVIA/RVDA Nationally Certified Master Tech
Master Tech Energy Systems, Inc.
AM Solar Certified Installation Center
Lifeline Batteries**Magnum Inverters
541-490-6357

Lew, having installed ME-RC, I'm trying to make sure I have the settings correct for 2014 AI.
01-Search Watts-5W
02-LBCO-10.0VDC
03-Absorb Hrs-1.0
04-Bat Type-AGM 1
05-charge rate-80%
06-VAC dropout-80VAC
07-PWR Save-5min
08-screen contrast-90%brightness50%
09-Final Charge-Multi
10-Pwr Up Always-No

You comments are always appreciated.
Adding ME-RC was very straightforward. Hard to understand why that remote isn't standard issue.
Bruce T.


2014 Airstream Interstate
Currently a "Weekender" but planning a cross country trip next summer.

[lewster]

Bruce, see my comments in red below:

I need to know what your battery bank size is. Is it the standard 80 amp/hour X 2? If so, you have a total of 160 amp/hours and at the C/5 rate, you need 32 amps of charging, and the closest setting on the Magnum for your size charging section is 70% (50 amps X 70% =35 amps).

Originally Posted by Brucet45410

Lew, having installed ME-RC, I'm trying to make sure I have the settings correct for 2014 AI.
01-Search Watts-5W
02-LBCO-10.0VDC
03-Absorb Hrs-1.0
04-Bat Type-AGM 1
05-charge rate-80% 70%
06-VAC dropout-80VAC
07-PWR Save-5min I usually set this to 1 minute
08-screen contrast-90%brightness50% 100% for both
09-Final Charge-Multi
10-Pwr Up Always-No

You comments are always appreciated.
Adding ME-RC was very straightforward. Hard to understand why that remote isn't standard issue.
Bruce T.

EVERYTHING ELSE LOOKS GOOD!!

2014 Airstream Interstate
Currently a "Weekender" but planning a cross country trip next summer.

[Brucet45410]

Lew, Super response as always. I'll make the changes you suggest. I plan on getting back with you for Feb modifications as discussed in previous PMs.
BruceT.


2014 Airstream Interstate
Currently a "Weekender" but planning a cross country trip next summer.

[Semmons]

Our 2014 is dead today too. Hooked it up to shore power and still noting is working (except the microwave!?) we called the dealer, since we hadn't touched it since we got it back from them before the holidays, but they were not able to help. The key won't turn in the ignition. Any suggestions? The whole power system is still so confusing to me!

Thank you!


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[UKDUDE]

Originally Posted by Semmons

Our 2014 is dead today too. Hooked it up to shore power and still noting is working (except the microwave!?) we called the dealer, since we hadn't touched it since we got it back from them before the holidays, but they were not able to help. The key won't turn in the ignition. Any suggestions? The whole power system is still so confusing to me!

Thank you!


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The dealer is a miserable so-and-so and should be offering you some help - even over the phone. Are they a Mercedes Benz dealer or just an RV dealer?

If you cannot turn the ignition key, then clearly the chassis battery is dead; have you confirmed that by trying the headlights, etc?

If you leave it hooked up to shore power, then the chassis battery will eventually be charged enough to turn the key and start the engine.

But the mystery remains as to why the chassis battery was drained. It's my understanding the Interstate has an Isolation Manager that should prevent the chassis battery from being accidentally discharged from the coach side..... unless something has been drawing power directly from the chassis battery over the holiday. Do you have an alarm fitted, for example?

[Protagonist]

Originally Posted by Semmons

Our 2014 is dead today too. Hooked it up to shore power and still noting is working (except the microwave!?) we called the dealer, since we hadn't touched it since we got it back from them before the holidays, but they were not able to help. The key won't turn in the ignition. Any suggestions? The whole power system is still so confusing to me!

The simple solution to get you back on the road is a jump start. If you hook up the jumper cables and leave them hooked up for a couple of minutes before you insert the key in the ignition, you should be able to turn the key.

I've had to do that a couple of times; turns out my original battery was defective, with a dead cell— replaced by Mercedes Benz at no cost to me and no problems ever since.

[73shark]

The chassis battery disconnect didn't get accidentally disconnected did it?

[Semmons]

The dealer was able to help and it is charging! Now we need to figure out why it drained completely. Thanks for the feedback, as always, this group is the best!


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[Boxster1971]

If you would like some help in troubleshooting your problem we need some more details. How long was your Interstate sitting unused and not plugged in? Where you getting sunshine on the solar panel?


- - Mike
2013 Lounge EXT on 2012 Sprinter

[FromDad]

I'm glad you understand it. I've read and read again many posts here on battery charging and have NO idea what any of it means. Nothing is sinking in.
What I need is for someone to tell me, step by step:
1 - push this button
2 - turn that switch
3 - jump up and down three times
I KNOW that sounds silly to you all who understand. I feel like I'm reading another language and it's Latin!
If anyone can write step by step how to avoid depleting the house battery.....I'll give you my first born who is now 33.

[PSchw]

I have mine 2013 now for 2 weeks or so not used but hocked up on shore power my house battery is up to 13.7V my coach battery is down to 12.7V. I exercised the generator and the coach battery came up 13.6V during the 1/2 hour run of the generator.
Should the magnum charge also the coach battery? Or is this normal?
Thanks
Peter

[e93pvaz]

Another question- Just to confirm when storing the 2014.5 AI for a month or two at a time it is fine to leave it hooked up to shore power (in this case a 20 amp circuit) the whole time? Also if I do should the magnum inverter be set to on?? (green light on)? Thanks again everyone