I need a short course

[Robin Goffrier]

My 06 PT is pretty much all electric so I have 6 batteries, 2 each AGM 1000 CA starters and 4 each AGM 12V 198 aH 4D house batteries.  All batteries installed less than 2 years ago, 2018.  We don't dry camp a lot in 43 feet but now and then to take the grandkids fishing we'll find a site that we'll fit in.  My question pertains to state of charge in the morning after inverting with the Magnum all night.  The residential refer is the big draw. It is my understanding that the 4 4Ds should provide almost 800 aHs but wishing to not draw them down below 50% that's 400 aHs. After 9 hours of inverting my state of charge indicated on the Magnum remote reads 12.3 V which my understanding means the bank is getting down there.  Does that sound right or am I missing something.  The remote will say "Inverting, 12.3 V, 13 Amps.  Thanks in advance for your consideration relative to my ignorance on the matter.

[Steve Huber Co-Admin]

Robin,
Your numbers sound about right. We have a Samsung 18.5 cu ft reefer and  6 wet cell house batteries. After running all night with the DW's TV on also our battery bank is down to about 12.3V.
Steve

[Fred Brooks]

   Robin,
 That sounds about right. I too am left with 12.3 volts after and evening of fun when dry camping including sat dish, 2 tv's, Samsung Refer, Bose system and microwave.
  Here are some considerations. Inverters normally require 10 times more 12 volt energy to make it into 120 volts ac house power. Example would be a microwave which is 1500 watts. 1500 divided by 120 volts equals 12.5 amps of A/C power. Multiply 12.5 X 10 = 125 amps of 12 volt power. Now keep in mind you only run a microwave for a few minutes at a time so don't let that alarm you. My Samsung RF-18 requires 1.2 amps so it pulls 12 amps of battery power when it cycles 3 times an hour. You are correct not to discharge your batteries beyond 50% of there capacity. 11.2 volts equals a "dead" battery. 12.7 to 12.8 equals a fully charged battery. 12.0 volts is 50% discharged. Hope this helps, Fred

[George Harwell]

You have probably seen this before but here it is again. Recharge the batterys using the generator before you crank up to travel. The alternator will thank you.

[Bryan Beamon]

Robin, Fred's comments are right on but the information he
states  on12.0 volts equally 50% discharge is contrary to my experience. The 12.3 volts equals 50% discharge. I hate to disagree with Fred because he has been so accurate in the past

[David T. Richelderfer]

12-volt Battery State Of Charge Reference Chart

%     volts
100   12.70
95   12.64
90   12.58
85   12.52
80   12.46
75   12.40
70   12.36
65   12.32
60   12.28
55   12.24
50   12.20
45   12.16
40   12.12
35   12.08
30   12.04
25   12.00
20   11.98
15   11.96
10   11.94
5   11.92
0      11.90

from Marine Systems

[Robin Goffrier]

Thanks, boys.  Always a great resource.  By the way, I posted previously concerning two recent occasions when I got a red "Check Transmission"  light and subsequent inability to get the trans to shift and Freightliner's inspection and recommendation. I disconnected Silverleaf data plug from port in dash and have driven about 700 miles with no issues,  I personally delivered the Silverleaf black box to Silverleaf for diagnostic test. They had it 2 weeks and found everything nominal. Said wires in forward diagnostic port might be mis-wired relative to the #39 something or other.  I am not but a humble RV driver, uneducated or familiar with both terminology and details of coach wiring.  (I know enough not to stick a red and black wire on my tongue.  That's about it)  So most likely I will not be able to use the Silverleaf any more.  Ratmanure.  I really liked that unit.

[Fred Brooks]

    Hey Guys, Your input may be more accurate. When Vogue started installing inverters back in 88, that was the training we received from the manufacturer of the inverter and the batteries we were installing. I am pretty sure technology has marched on and they have perfected the "curve". Never my intention to mislead any one especially when we all know what a challenge it is to figure these coaches out. Blessings, Fred

[Bill Sprague]

The only time voltage works to measure a battery is when there is nothing drawing from it and it has been at rest for 30 minutes or more.   In other words, since you can't turn everything completely off in a motorhome, voltage does not accurately indicate remaining capacity.   

[Dave Atherton]

Robin, reading your post about having your silver leaf checked and the returned thoughts where
possible problem may be in wiring of forward data port connection. Remembering  back at Indio
With your older motorhome and we changed out the ECM being shorted out with plugging in a
Aftermarket code reader into data port that thought had been wired incorrectly. You mentioned running several hundred miles with unplugged attachment from data port without any problem. My suggestion
knowing that the data port wired unfused including both the hot and ground wires any aftermarket
attachment is not working correctly can short out your engine ECM. Dave Atherton Retired Cat Mechanic

[Bill Lampkin]

Robin, You may want to see if adding a battery monitor to your Magnum inverter would help, if it does not already have that function.

https://www.magnum-dimensions.com/sites/default/files/MagDocs/64-0013-Rev-A-ME-BMK.pdf