john_harris Report post Posted August 6, 2021 interior electrical system shuts down as soon as i disconnect from shore power. First thought it was the 15 year old 2000w Magnum ME modified sine wave inverter. batteries tested 12.6 volts but magnum panel showed low voltage fault. could not retract jacks or return slides without having engine on. even had trouble starting generator but thru boost got it fired up and made it home. had to run generator while driving to power residential refrigerator. when got home and plugged into shore power, all was again normal until after a few days of fully charging to float charge. again as soon as i disconnected from shore power, all power shut down. came back on as soon as reconnected. Replaced inverter with new MS 2012 and everything worked fine on start up. after an hour or so charging batteries to float, turned of shore power and power immediately shut down again, both 12v and 110v. panel indicated low batteries at 4.5 volts. I checked batteries with multimeter and each tested at 6 volts individually and 12.5 in parallel but magnum panel still indicated low voltage and no power even after connecting to shore power. went back thru start up procedures, did reset on inverter but nothing changed. shutdown shore power and tried to start generator. even with boost took a while and would not stay on. plenty of fuel. started engine and after a few minutes, power came back on and seemed to be normal and batteries at 13.8v until shutting of engine. then no power. reconnected to shore power, no change. restarted engine and power came back on as before. this time i reconnected to shore power before shutting of engine. this time power stayed on. left system plugged into shore power but confident power will go down as soon as i drop shore power. 12 years ago i bypassed the salesmen switch, so no issue there. last year i added 400 watts of solar but added a cut off switch to isolate solar panels into charge controller and controller to batteries to avoid potential conflict with charging batteries from solar while on shore power or using generator. not sure that caused issues with ATS. any thoughts of trouble shooting power issues. 2007 HR Endeavor Share this post Link to post Share on other sites
hermanmullins Report post Posted August 6, 2021 John, It may be your ATS(Automatic Transfer Switch). Herman Share this post Link to post Share on other sites
richard5933 Report post Posted August 6, 2021 How old are the batteries? How many & what size are they? Is there a large load which was inadvertently left on which is drawing on the batteries through the inverter such as a water heater or electric space heater? It will almost instantly cause the inverter to see a low-voltage situation. Share this post Link to post Share on other sites
john_harris Report post Posted August 6, 2021 Herman, ATS is my guess now, any way to check it out or test theory. Richard, no new loads other than residential refrigerator installed 2 years ago. Water heater off. Share this post Link to post Share on other sites
richard5933 Report post Posted August 6, 2021 How would a bad ATS cause the low-voltage situation at the batteries? It only controls where the 120v power goes and not the charging of the batteries. Couple of things come to mind... 1) This appears to have happened after swapping the inverter. Could something not be connected properly? 2) Voltage of 12.5 after the charging system goes to float is low. It should be higher for a freshly charged battery bank. What's the voltage output of the charging circuit on float? Share this post Link to post Share on other sites
john_harris Report post Posted August 6, 2021 Richard, no, this was the reason i swapped out inverter. this first occurred while on a trip to Virginia 3 weeks ago where we had limited run times for generator. problem occurred after being away from coach for most of the day. when we returned, batteries showing 11.9, fired up generator and after only a few minutes, went from bulk charge to absorb. generator ran for an hour or so while we did dinner, then as soon as the generator was turned off, power went down. Magnum monitor said low batteries, but charge controller on solar indicated 12.8 v with solar panels off. did not have multimeter to confirm at time but basically got the same type readings when i got home. Batteries charged for days on shore power but as soon as shore power disconnected, power went down When swapping out inverter, batteries were off shore power only for an hour so should have been pretty good shape to begin with. took pictures of all original connections and reconnected identically. Share this post Link to post Share on other sites
john_harris Report post Posted August 6, 2021 by the way, magnum monitor also switched out with inverter. Share this post Link to post Share on other sites
wildebill308 Report post Posted August 6, 2021 20 minutes ago, john_harris said: but charge controller on solar indicated 12.8 v with solar panels off. did not have multimeter to confirm at time but basically got the same type readings when i got home. Batteries charged for days on shore power but as soon as shore power disconnected, power went down 12.8V is a fully charged battery. 13.8v +/- is charging voltage. Bill Share this post Link to post Share on other sites
manholt Report post Posted August 6, 2021 John_harris, When you added the fridge, did you also add one or two extra batteries? The 2012 Magnum is for (4) 6V batteries, the 2812 is for 6 batteries. I would take each engine battery out and have it bench tested....most car parts stores will do it for free. Share this post Link to post Share on other sites
richard5933 Report post Posted August 6, 2021 50 minutes ago, john_harris said: Batteries charged for days on shore power but as soon as shore power disconnected, power went down There are only two options here if this is what you're seeing... Either they aren't truly being charged on shore power, or your batteries are not capable of holding a charge. Or perhaps a third option, a hidden load being applied to the batteries. Since you just changed out the inverter/charger and had similar issues both before and after, I'm leaning towards the batteries being the culprit. Does either your inverter/charger or your solar charge controller have a way to do equalization? If so, you might try that and see if it helps any. Be cautioned before you do that though that the higher voltages involved in equalization are not friendly to all 12v devices and appliances. When I do this in my coach I disconnect everything other than the charge controller and batteries so that the higher voltage doesn't get sent to any devices (installed a battery disconnect just for this). Otherwise, I'd agree with Carl that you need to get the batteries tested to see if one has a bad cell. This would cause one to go to low-voltage state or show other errors. Share this post Link to post Share on other sites
dickandlois Report post Posted August 6, 2021 (edited) John, Question. Is the inverter set in standby mode ? When the coach is connected to shore power? This should a low the inverter to start and supply power to the circuits it is connected to, when the inverter comes on line. If the inverter does not come on line then the inverter is not working correctly or the house batteries are not holding a charge or they are not connected correctly ! Is there an open ground connection between the batteries and the chassis ground, the common ground connection is missed at times when the batteries are reconnected or replaced. Rich. Edited August 6, 2021 by dickandlois Share this post Link to post Share on other sites
rayin Report post Posted August 6, 2021 We need some answers. Are the battery cells full of solution? Have you had your batteries load-tested yet? What is the age of your batteries? Are all battery cables clean and tight? Have you ohmed them out for solid connections? As you can tell I highly suspect your battery bank is the root of the problem. You may be confident your battery bank is fine, but without answers to those questions you cannot know absolutely. Share this post Link to post Share on other sites
richard5933 Report post Posted August 6, 2021 Scroll down to the section about "false capacity" on this page: https://www.solar-electric.com/learning-center/deep-cycle-battery-faq.html/#AGM, or Absorbed Glass Mat Batteries It might explain why you have seemingly good voltage at the batteries but still little capacity. Share this post Link to post Share on other sites
kaypsmith Report post Posted August 6, 2021 (edited) I lean strongly towards bad battery bank, but also need to know the total amp draw on the inverter when it is called upon to produce 120 volts. Has anything been added to the 120 volt system just before the problem started to occur? A 2000 watt inverter only produces about 16.6 amps when the batteries are fully charged, and will seriously discharge even a good battery bank in a very short time. A load of over 50% (8.8 amps) is about all that one can be called upon to last for any small time if the battery bank is too small. Look at the label inside the residential fridge to determine maximum amp draw, this will be at startup of the compressor and about 50% of that for running amps. As mentioned by others, what is the size of the batteries and how many of them to determine how long they should last. Also, when was the last time that the battery terminals was cleaned? Edited August 6, 2021 by kaypsmith Share this post Link to post Share on other sites
