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Old 03-05-2014, 09:40 PM   #1
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Remote Battery monitor project

Working on a project using a beaglebone micro computer to monitor and report on battery voltage levels.

I've spoken to a programmer that outlined what would be needed and I'm hoping to find someone with experience that would also be personally interested in helping build this for themselves. (Read: someone with an interstate if their own)

The basic idea is a computer that would monitor the battery voltages, record a log of voltages over time, and send an email if voltage dropped below a defined level. There are very cost ($9) USB wifi modules available. I have a ipad mini mounted in my AS that broadcasts it's own wifi network.

A second stage for the product may involve relays that would cut power to certain units to help conserve power at lower levels (such as the propane solenoid or possibly the inverter)

Any feedback on problems/recommendations welcome.
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Old 03-06-2014, 06:43 AM   #2
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A second stage for the product may involve relays that would cut power to certain units to help conserve power at lower levels (such as the propane solenoid or possibly the inverter).
Seems to me as if you're talking about a 12vDC EMS to go along with the 120vAC EMS that's already installed. Interesting idea. But deciding which devices to automatically shut off first to conserve power will be the kicker. The 120vEMS tends to shut off the biggest energy users forst since that's the fastest way to get your amperage draw down to where it needs to be. But on a 12vDC system, instead of biggest draw first, it ought to be least-essential users first.

One thing you do not want your 12vDC EMS to shut off, ever, is your fridge. Spoiled food because the EMS shut off the fridge would not be a good thing. I'd make the water heater the first thing shut off by the 12vDC EMS, if it's in electric mode, because you can always switch over the water heater to propane mode, and an electric heating element is a major electricity user as well.

If it was me, I'd also leave the propane solenoid out of the mix. Sure, it's a major parasite if you leave it switched on when you're not using the propane, but you don't want some computerized box to shut off your propane for you when you are using the propane. A better solution for the propane solenoid— in my opinion— would be an LED telltale in a conspicuous location to remind you that the propane is switched on. The LED would add slightly to the parasitic drain while the propane is switched on, but not when it's switched off and the light isn't lit. I'm thinking that placing the indicator light right next to the generator controls and water heater controls would be ideal. That way, you'd know if the propane is on before you fire up the heater or generator. And it's close enough to the furnace thermostat that you could check before turning on the furnace, too. That only leaves the stovetop, and if that fails to light because the propane is switched off then no immediate harm done.

Some folks have wired a second propane switch on the curbside locker control panel, but the LED would still be of benefit in that case. That way, if the propane refiller shut off your outside switch and didn't switch it back on when he was done, when you switched on the inside switch and the LED didn't light up, you'd know right away that the outside switch is still off.
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Old 03-06-2014, 12:25 PM   #3
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All valid points. The owners usage would obviously dictate different preferences. In my case, we use the AS almost exclusively as a travel vehicle. As such, the water heater is almost never used (used it once at the beach so the kids could hose off the sand with warm water). The propane is only used for the generator or heater. We store drinks constantly in the fridge but rarely ever food.

The advantage of a system like this is that you COULD easily set cut offs based on preference, not voltage. I'm still trying to determine if it would be possible to switch the inventor to charge only as one of the options.

My problems have been largely: taking it away from home and forgetting to kill everything when parking or thinking I don't need to plugin or shut things down because I'll be using it again before it becomes and issue.

This last weekend I had the AS at the shop for a quick fix to the camera. That turned into needing it overnight, which turned into it staying 4 days because I was out of town in business. I didn't kill everything when I dropped it off because it was only supposed to be there 2-3 hours. I'm sure the batteries ran all the way dead by the time my wife was able to get it.

Situations similar to this have happened 3-4 times and now I think I'm looking at $650+ for two new batteries.

I realize I SHOULD just shut everything down everytime I park it, but we have the AS setup in the bed configuration 90% of the time with a memory foam topper and getting to the cutoff involves me crawling on my stomach to get to the access panel.

I should also install an internal cutoff for the propane, but I'm waiting until I do the solar upgrade as I only want to tear all that apart once.

Basically, I'm lazy and I know it
So I'm looking for technology to look out for me when I forget or can't do these things myself.
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Old 03-06-2014, 09:31 PM   #4
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Protagonist -- you're right on about having an LED warning light to indicate when propane is switched on. I accomplished that by installing an second interior propane switch with an amber LED indicator light built into switch. Got it at a local auto parts store.
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Old 03-06-2014, 09:39 PM   #5
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jquayle -- a simpler solution to save batteries when you can't plug in would be a total battery cutoff switch. I plan to add one next year when I upgrade my batteries. For now the added solar is really working well to save my original batteries.
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Old 03-06-2014, 10:02 PM   #6
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The newer model Interstates have a cutoff mounted in the jam on the sliding door. I inquired about retro-fitting that onto my AS but was told it would probably be cost prohibitive. The cost cutoff switch under the rear panel needs to be replaced as well as obviously the new switch. Labor cost as well was expected to be north of $700.

Do you have a different solution you were thinking about?
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Old 03-06-2014, 10:10 PM   #7
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The newer model Interstates have a cutoff mounted in the jam on the sliding door. I inquired about retro-fitting that onto my AS but was told it would probably be cost prohibitive. The cost cutoff switch under the rear panel needs to be replaced as well as obviously the new switch. Labor cost as well was expected to be north of $700.
At least on my 2013 AI the cutoff switch in the door toggles a motor that mechanically rotates the cutoff switch under the rear lounge on or off. Strikes me as a bit of a Rube Goldberg engineering, but that would help explain the cost of the retrofit.
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Old 05-17-2014, 09:42 AM   #8
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.... ....Do you have a different solution you were thinking about?

I just noticed that I never really answered this question. I was thinking of a total battery shut-off that completely disconnects the coach battery from all loads. The current Airstream disconnect switch leaves most of the parasitic loads connected and they will drain batteries after a few days of non-use.

But now that I have lots of solar it's not an issue as long as my van gets some sun light. If the new Interstates now have 100 watt solar panels Airstream has pretty much solved this issue.

I really want a switch more for quick maintenance on 12v systems. The Sprinter has such a disconnect on the negative side near the accelerator pedal.

But there are possible issues with the coach battery isolation monitor that connects the two battery systems. I'll have to research the design further. This will have to be a winter project for next year since I'm now focused on getting ready for the summer travel season.
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Old 05-17-2014, 05:15 PM   #9
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Besides the BIM and the propane detector, what other parasitics draws are there?

The solar panel produces on cloudy days.
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Old 05-17-2014, 05:27 PM   #10
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Besides the BIM and the propane detector, what other parasitics draws are there?
Any display panel in the curbside overhead locker that still indicates anything when the main disconnect is off is a parasitic draw as well.

So is the inverter/charger, that draws power for monitoring purposes and the cooling fan unless switched completely off. The Magnum i/c units are hard to switch off. The Tripplite units are easier to switch completely off.

Antenna booster may be a parasitic draw if left switched on.
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Old 05-18-2014, 11:55 AM   #11
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Besides the BIM and the propane detector, what other parasitics draws are there?

The solar panel produces on cloudy days.
I just looked over the 12volt Main Schematic for my 2014/13 Ext body, Rear Lounge Airstream WITH solar. These are the various connections that COULD draw/use electrical power from the RV batteries. All other 12 volt electrical items are on the other side of the Main Battery Disconnect (the switch on the door frame). If the Master Battery Switch is off, those other items have no ability to access 12 volts from the RV batteries. I do not know the possible wattage draw on these items. I keep it plugged in when I'm not using it.

1. Inverter receives 12v constantly from RV batteries.
2. BIM (also called Battery Separator)
3. Dash radio is always powered to keep its memory.
4. Solar controller-it probably has some draw as it has an electrical circuit.
5. Tank heaters--only if turned on of course.
6. Rear lounge motor--only if in use to lower/raise the lounge.
7. By-pass engine start push button for Mercedes--only if pushed of course.
8. Master battery disconnect switch--if off then no draw on what is hooked to the main power distribution box.

Per Magnum specs....inverter usually draws 5 watts and NO LOAD 19 watts typical

The BIM-battery separator will charge the Mercedes start battery IF the voltages of the RV batteries are sufficient (don't know the settings) AND the MB engine battery voltages are BELOW a set-point voltage (don't know the settings).

The Carbon Monoxide (C) and Propane (LP) detectors along with the LP tank shut-off valve and the 12v side of the refrigerator do not receive ANY 12volts with the Master Switch OFF. NOTE: the CO detector does have a 9volt battery internally and it reminds you to turn off the 12v Master before opening and changing the 9v battery.

The motorized side step, the step alarm, the power awning (if equipped) and the backup camera all are supplied 12volts from the Mercedes engine starting battery.



This I had posted back in April. Sorry to repost but thought it might help.
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Old 05-18-2014, 12:40 PM   #12
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So it appears that the parasitic draws, ie things that can't be turned off are the BIM, solar controller, propane detector, and radio memory. But wouldn't the radio memory be on the chassis battery?

Since mine has the Tripp-Lite, I can turn it off.
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Old 05-18-2014, 01:05 PM   #13
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So it appears that the parasitic draws, ie things that can't be turned off are the BIM, solar controller, propane detector, and radio memory. But wouldn't the radio memory be on the chassis battery?
...
I've also posted on this topic before. On my AI the 12V parasitic or standby draw measures at 0.4 - 0.5 Amps on my Blue Sky battery monitor. The BIM is by far the single biggest draw at 0.3 Amps as per manufactures specs.

The radio draws very little, but it can be from house battery if the your house battery disconnect switch is ON.
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Old 05-18-2014, 02:07 PM   #14
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As i stated in our 2014/13 the Propane Detector is OFF and does not draw electric when the Master Switch is off. Test if yourself. Turn off the Master Switch and you probably will not see any indicator on the Propane Detector. In fact when I turn on the Master after being off overnight, I get a "chirp" sound when the Propane Detector is again activated.

The radio draw memory from the RV batteries even when the Master Switch if Off. I have a set of wiring diagrams from Airstream and I took the time to follow all the circuits to determine my statements.
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