Simple Guide to Battery Life in your RV - By Redbaron73

[SavageCatHV]

I've been looking for a resource just like this!

Thank you X 1000!

[Oldcaster]

Another Great Resource out there for those who want to know everything there is to know about Batteries - Very in-depth and a great resource.

https://batteryuniversity.com/

[Grandparacer]

Math question for the OP. In the current based SOC section you described various test loads and duration that I calculated to have consumed about 125 amp hours from your 840 amp battery pack. This in turn is about 15% of your total capacity so you would have about 85% left not 94%. Did you calculate 94% or was that what the Current based monitor reported?
John

[redbaron73]

Originally Posted by Grandparacer

Math question for the OP. In the current based SOC section you described various test loads and duration that I calculated to have consumed about 125 amp hours from your 840 amp battery pack. This in turn is about 15% of your total capacity so you would have about 85% left not 94%. Did you calculate 94% or was that what the Current based monitor reported?
John

That was what the system reported.

The reason for discrepancy is the load was not constant for the time. The microwave was the largest load, and this cycles on and off. When I reported the numbers, I reported the 'max' load and the entire duration.

Another way to think about this for those that dive:

Using the dive tables, you have much less bottom time vs using a computer that takes into account the variation in dive depth profiles.

The BMK is a computer taking constant readings of amperage flow both directions, and treating it like a gas gauge.

[Grandparacer]

That makes sense, so the real load was less on average. So, it sounds like a pretty good system that monitors real battery useage !

[R0k0la]

Excellent information, not to mention a good future reference guide when needed. I just went through replacing my Magnum Inverter and headed out. I did not check the settings and found later the AGS was not enabled. After driving 14 hours in two days with my res refer, laptop, micro, phone charger all plugged in. Did not run the generator at night and ended up blowing the 300 amp fuse connected to the Inverter due to what I think was a low battery condition. Fortunately, the new inverter is ok and my batteries seem to have come back to life. Huge lesson learned, don't run more things than what your alternator can charge. Doing so will drain the batteries below the level the inverter needs thus causing a variety of problems.

[paisleytime]

Thank you for sharing your knowledge -wonderful resource. Could you help me with your example for Final Charge Rate % on the top of page 14? The example says to use the battery "bank" calculation in "C", but C is the indiv battery rate, not the "bank" calculation.

And aren't most RV LA batteries over 200Ah which makes this whole example questionable?

Could you also check my math below for my unique circumstances?
My rig has 6 x 225Ah Flooded, so 675Ah for the bank using your calculation. They are GC2-ECL-UT, BMr of 10, so your calculations give me a Max Charge rate of 67.5 Amps. My MS2012 has a max output of 100 Amps, so I'm getting a Final Charge Rate of 67.5%.

Newmar or the dealer set max charge to 80% so I've since set to 70%, but your guidelines would suggest 60% (as you say don't go over).

[757driver]

Originally Posted by paisleytime

Thank you for sharing your knowledge -wonderful resource. Could you help me with your example for Final Charge Rate % on the top of page 14? The example says to use the battery "bank" calculation in "C", but C is the indiv battery rate, not the "bank" calculation.

And aren't most RV LA batteries over 200Ah which makes this whole example questionable?

Could you also check my math below for my unique circumstances?
My rig has 6 x 225Ah Flooded, so 675Ah for the bank using your calculation. They are GC2-ECL-UT, BMr of 10, so your calculations give me a Max Charge rate of 67.5 Amps. My MS2012 has a max output of 100 Amps, so I'm getting a Final Charge Rate of 67.5%.

Newmar or the dealer set max charge to 80% so I've since set to 70%, but your guidelines would suggest 60% (as you say don't go over).

Keep in mind that if the coach is being used there is some of that charge rate that is being used up in other areas such as lights and other 12v power sources. A setting of 70% charge rate will not be too high for your batteries. A battery monitor will show you exactly how many of those charge amps are being returned to the battery bank.

[redbaron73]

Originally Posted by paisleytime

Thank you for sharing your knowledge -wonderful resource. Could you help me with your example for Final Charge Rate % on the top of page 14? The example says to use the battery "bank" calculation in "C", but C is the indiv battery rate, not the "bank" calculation.

And aren't most RV LA batteries over 200Ah which makes this whole example questionable?

Could you also check my math below for my unique circumstances?
My rig has 6 x 225Ah Flooded, so 675Ah for the bank using your calculation. They are GC2-ECL-UT, BMr of 10, so your calculations give me a Max Charge rate of 67.5 Amps. My MS2012 has a max output of 100 Amps, so I'm getting a Final Charge Rate of 67.5%.

Newmar or the dealer set max charge to 80% so I've since set to 70%, but your guidelines would suggest 60% (as you say don't go over).

I see where I need to come up with a better way to clarify this.

When we look at [G] - Battery Bank capacity - this is for the entire battery bank. To answer your first question - use the value of 675

Final Charge Rate for pg 14 states to use the value from "05-Charge rate above", and divide it by the max charge rate of the charger to get a %. The value in 05 is expressed as a rate in amps.

There is a lot of data used in this chart, and it all comes from your personal settings on page 12.The reason I put the personal settings first is that it is used for all of the settings, and it allowed me to present formulas that were accurate for every situation.

I am going to use the information you provided to fill out your personal settings here:

A. Battery Type (Choose One): Wet Flooded

B. Number of 12-volt battery banks: 3

C. Battery 20Ah Rate: 225A/h

D. Inverter Model: MS2012

E. Charger Model: MS2012

F. Max Charger DC Output: 100 Amps DC

G. Battery Bank Capacity: 675Ah

Now we can move on to "05-Charge Rate" This has 2 values it asks for

C - Total Amp Hours. This is based on [G], so 675Ah

BMr: This value comes from the battery manufacturer. Unfortunately I cannot find a recommendation for your battery, and it is *not* the HD variant. Based on that and the fact it is a wet cell, I would use the C/20 rate.

Max Charge RateThe value here should be 33.75

Final Charge Rate%: 33%


The difference here between your calculation and mine is that I cannot find a value that supports the model battery you have at the C/10 rate. The problem with charging too high of a rate is that it will boil over faster.

I hope this helps.

[paisleytime]

So my charger HAD been set to 80%, your calculations are saying 30%, big difference. And I HAVE been getting some boilover in the past (which has messed up my tray and one of the straps corroded thru at the tray connection) so this helps explained what's happened. I'll reset the charge rate to 30% today. MANY THANKS for the education on this and responding to my individual question.

[paisleytime]

Oh, and I can't find a clear answer in the Magnum manual where to set the SHORE MAX setting, 30A or 50A are my choices. I'm on 30A at home but 50A at most parks. We occassionally boondock with Gen power.

[redbaron73]

Originally Posted by paisleytime

Oh, and I can't find a clear answer in the Magnum manual where to set the SHORE MAX setting, 30A or 50A are my choices. I'm on 30A at home but 50A at most parks. We occassionally boondock with Gen power.

30amp is what I would set it to. It doesn't really matter, as the charger will not consume more than 15 Amps AC on a continuous load. This can be dialed back via the EMS automatically as needed.

If you don't have EMS, you can dial it down to tell it how much AC you want the charger to utilize. I have had to assist a friend that did not have EMS and was having trouble running even a single air conditioner off of 30 amp AC. We set his charger to a max of 7.5 amps AC and that helped with the loads of the single Air unit.

[CaptainGizmo]

Ronnie, or anyone,

So I have a specific question after just running into this scenario...

My LBCO is set to 11v.

My AGS is also set to come on at 11v.

My levels dropped to the point where the inverter was shut off. The generator didn’t come on, because we were on Quiet Time”.

Question is: If the LBCO turns the inverter OFF when the volts drop to 11, WILL THE INVERTER COME BACK ON AUTOMATICALLY once the battery levels come back up? My assumption is NO; since once the inverter kicked off, and the loads were removed, the batteries came back up to 11.6v, but the inverter stayed off in the FAULT mode.

My concern is this: Once the LBCO is met, the Magnum goes to “FAULT” and the inverter is shut off. Even if the AGS is set to the SAME voltage, ie. 11, it’s too late, and the inverter won’t come on until you clear the fault and turn it back on manually.

Therefore, it seems like the two criteria should have some separation to avoid this “collision”; ie. LBCO set to 11v, and the AGS set to 11.2v.

I know having a BMK makes this a more stable monitoring situation, but am I correct in my above concerns?

[NealC]

AGS needs to save you before you hit LBCO, it should not be the same. The quiet hours issue is a problem, next time try to see where you are voltage wise and maybe run the gen a few hours prior to quiet time or turn the inverter off manually if you're going to hit LBCO. No, inverter will not turn itself back on, I don't think, as you won't get back above 11.0. You need to manually run the gen and get your V up then turn the inverter on again. The fault is probably the LBCO hit or AGS not being able to run, you can read your faults in the tech section as needed.

As I have a ME-BMK I have a cascading failure settings the blends solar, AGS, then LBCO by percentages. Moral is AGS will hit before I get to LBCO so that LBCO is never hit.