ME-AGS-N programming

[erniet]

When setting the length of time for my generator to run, I'm instructed to look at table 8.3 There I find battery AmpHrs Capacity and suggested gen run time.


I have 4 batteries, each with 225 Ah. Would I multiply the 225 X 4 to give me a total of 900 Ah and set the time according to what the chart states?
Or would I only set for 225 Ah?


I don't want to run my generator any more than I have to. I am the 2nd owner of MH and it has a huge household refrigerator that uses 10 amps. So the generator runs more than I would like. Am wondering if I gave it a FULL charge, maybe it might not run as much in the long run. I have the Gen set to start at 12.2 V (50%). It usually goes to FLOAT charge around 1.5 hours + or -.



Thanks, Ernie

[formerFR]

I think it all depends on what you want the generator to 'do' for you...meaning, are you trying to FULLY charge your batteries from almost dead, or are you just trying to bring your battery bank back up to a usable charge?

I've never changed from our initial 30 minute RUN TIME, as I don't want the generator to run for hours, and am not 'expecting' to always get a full charge for the whole battery bank everytime the generator is used, whether when I turn it on manually for other reasons, or whether the AGS turns it on due to my VOLTAGE setting.
Since I set my VOLTS start setting to about 12.0, the battery bank is not going to get so low that I need to run my generator for hours, and I don't 'need' a fully charged battery bank all the time.

Yes, if you expect the generator to fully charge the battery bank, and you're not going to want the AGS to kick on your generator during a long overnight, such as when you have Generator run time restrictions at a campground, you might then want it to run it longer, but in those cases I just turn it on well before the restriction timeframe and let it run the whole time until I turn it off myself.

Some will disagree, and believe that the AGS's only job is to fully recharge your battery bank, but I don't think that everyone camps that way - some of us are just looking to have a more comfortable and easy way to automatically start the generator to charge the batteries for a fair length of time.
When you're using the coach and doing a lot of things, it's plausible that the AGS will kick on the Generator more often, but when you're in an overnight where little is happening, the AGS will probably only call for the Generator to run once or twice overnight.

Using a chart is not set in 'reality', at least not in my opinion, unless you like your generator to run hours and hours.... your neighbors may also not like it.

[Oscarvan]

There's a LOT that goes into the math here.....

First to address some of the math the OP posted.....

you have 4 6V 225Ah batteries. 2 in series to make 12V STILL 225Ah.

Two of those pairs in parallel to make 12V 450Ah.

If you run it down to 50% and call that 12.2V (Voltage is a very poor measurement for state fo charge for a battery that is under load but that's another chapter) You will have to pump in 225Ah.

Problem is, that the charging is not linear. As you know you get your bulk/absorption/float. Bulk will get you to 80% fairly quickly, depending on what your charger's capacity/remote setting is. Most of us are set up for 80A. So 80% of 225 is 180A.... Charge does drop of somewhat so lets call it an average of 60A.

So we can say that you can run that bank to 50%, and then charge it to 80% in 3 hours. Running between 50-80 is common in battery dependent systems. It's the shortest charge time while maintaining the max battery life.

The fact that you get to float in 1.5 hours indicates that you're not really at 50%. Probably closer to 65-70% As I mentioned above voltage is a poor indicator of SOC. The serious boon docker needs a condition monitor. (Follow the link below to my blog and under mods see the install with a lot of background).

I never use the AGS. I monitor SOC and run the generator based on that. Unfortunately, and why boggles my mind, I don't think there's a way to run the AGS based on SOC after BMK install. THAT would be the optimum.

Hope this helps.

[erniet]

Oscar,
Thanks for the data and facts. You make me feel better, I had figured the 450 Ah, that's why I was charging for 1.5 hours.


I know SOC is the way to go but I'm a little thick headed on understanding the complete 'picture'.


Your blog is great but overwhelming for me on some of it.

[formerFR]

I'll add a tid bit also in reference to the SOC (state of charge) conversation... and since some will try to say that allowing your AGS to wait until your batteries are at 12.0Volts is too 'late' and will harm the batteries...

SOC is a condition of the batteries 'at rest', with no loads...but this is very, very uncommon when actually 'using' your RV since the batteries will almost NEVER be at rest, and there will always be SOME types of loads/draws, especially if you have a residential fridge, c02 and smoke detectors, 12v lights or fans in operation, cell phone or device chargers plugged in, etc.

Most of what we 'see' in the VOLTS reading are under the current loads at the moment we are looking at the readout, such as the Magnum ME-RC remote panel. Yes, this is not the 'ideal' tell-tell of what the battery bank condition is, but is more of the 'instant' condition, 'in the moment'.... which can certainly be WELL BELOW the actual battery bank SOC. The batteries might really be 12.5volts for SOC, as a whole, but while these loads have kicked on, the VOLTS readout might show 11.8volts, or even fluctuate between 11.8 and 12.3 WHILE loads are turning themselves on and off during that time, such as when the fridge's compressor kicks on for a few minutes, or someone is using the water pump for a few moments, etc.

So, if the AGS monitors the 'instant' VOLTAGE, and uses that as it's 'starting point' for the Generator, you are actually NOT dropping the overall battery bank voltage 'too low', but are simply using another method of calculation for the AGS to operate. The AGS is designed to start the Generator when the Volts have fallen below the Volts Setting for a Continuous 2 minutes. This is so that the fluctuations of the 'instant' Voltage reading does not 'nuisance start' the Generator every time the reading happens to fall below the Volts setting, but only when it's 'sure' that the loads are really creating this lower voltage for a considerable length of time, making it a more appropriate cause to start the gen.


Yes, if the AGS could use the SOC reading to activate we could more appropriately use a much higher VOLTS setting to active the AGS, but without that you must use your best judgement as to what Volts reading is appropriate for you and your 'camping' style. Some will want the generator to start very often, and some will want it to wait for a much longer period... everyone has a differing comfort level.
The fact, though, that your AGS Volts setting is a 11.9, versus 12.4, should not necessarily be any indicator that an owner is waiting too long. Our first set of standard factory-installed 6v House batteries lasted well into 5 years of usage, and over 90,000 miles of travel, with a lot of dry-camping, AGS usage, and a typical 11.9 or 12.0 volts setting for those situations.


FUN, ain't it!!

[formerFR]

Originally Posted by formerFR

I've never changed from our initial 30 minute RUN TIME, as I don't want the generator to run for hours, and am not 'expecting' to always get a full charge for the whole battery bank everytime the generator is used, whether when I turn it on manually for other reasons, or whether the AGS turns it on due to my VOLTAGE setting...

let me also add one note to this point: use your SHORE MAX button/setting to make sure that the Battery CHARGER is getting the use of the most AMPS while the generator is running, which is mostly 'why' the generator is running in the first place.
The SHORE MAX button/setting, at least for those of us with Magnum ME-RC or similar panels, is to let the Battery Charger know how much electrical power you are either plugged into(shore power), or how much you want it to be able to use from the Generator's output.
What this means is that you have the ability to dial 'back', or dial 'UP', the amount of Battery Charging power, for a quicker charge during your generator run, specifically.

If you forget to dial UP the Shore Max setting, you may not be getting anywhere near the amount of usable battery charging while the generator is in operation.
I typically use the 50amp setting when dry-camping during temperate climate and temps since we'll unlikely be using electric heat or air conditioning, which would need some of the generator's power output.
If it's during the winter, or summer, you may have to give consideration to the other large draws that are happening at the same time, even if plugged into shore power, which means you might need to then dial down the Shore Max to make sure you don't trip the Generator's breaker, or the Shore Power breaker.
I'm plugged into 50amp Shore Power now, but don't necessarily need Battery Charging to take precedence, but have more needs for electric heating due to low temps, so I have it dialed down to only 10amps.

[Oscarvan]

FormerFR is dead on with all of that.

Problem with voltage being a moving target..... how much when?

Yes you can set the AGS lower because the actual SOC of the battery is higher than the voltage would indicate, but again how much and when?

All highly inexact.

I'm going to call Magnum and have a chat with them......