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Battery woes

Hello All,
We awoke to 8.8 v reading on our coach battery's this morning. I immediately reset inverter to charge, not sure how it came to be off in the first place?  Within minutes the xantrex started knocking. Turned out the cooling fans weren't able to start ? Wanted to ask two separate questions. First off  after all day on an automotive battery charger the three agm's wont go above 11.5. Is it safe to say these battery are toast? Secondly is it normal for a four year old inverter to act up with battery that low? When I tried to charge with inverter this evening the knocking fan issue didn't reemerge over the 5 minutes or so we let it go . Battery's showed no improvement with inverter and charger working together.
 If we need battery's we'll survive , sure wouldn't enjoy purchasing what would be a third inverter for this coach!
                                                                    Many Thanks for any input in advance!
Tom
1998 U320 40'

Re: Battery woes

Reply #1 –
Tom,

Perhaps I can answer part of your question:  Yes, it is a common safety cut out that many inverter/chargers will NOT charge a deeply discharged battery.

So, you may have to use a supplemental "stupid" charger to get them started.

Can't answer the "are they toast" question without more information.  What charge rate did the automotive charger put into what size (in amp-hrs) battery bank?  May be dead, or may just need more of a charge before the smart inverter/charger can kick in.

Might also be a good idea to separate the batteries and charge them separately-- maybe one is good/one bad.  Short term, using only the good one is superior to the pair where one is bad.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Battery woes

Reply #2 –
The knocking you heard may have been a relay as Wolf was talking about the safety feature. The fans work off of a thermal switch and wouldn't have been running immediately after starting.
1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Battery woes

Reply #3 –
That would be absolutely marvelous!
The battery's are at least five years old, Inverter Sales in White House has great prices on gel battery's and I was going to pay them a visit to address our automatic transfer switch on Monday anyhow. REALLY didn't want to be purchasing a new inverter just yet😜
Thanks for the rapid response! Best forum ever!
Tom
1998 U320 40'

Re: Battery woes

Reply #4 –
Update: Engaged charger on xantrex this morning and aside from some initial buzzing from foot of bed all seems good for now. Battery's reading 13.2v
Tom
1998 U320 40'

Re: Battery woes

Reply #5 –
I have had trouble with my engine batteries as well. I have a freedom 25 inverter and seems to be working. Brett had said to check the settings, however, I could only find a on/off switch inside on the panel and on/off on the outside unit in the bay. inside switch is on and bay is off. I just replaced 3 batteries last week, something is drawing them down and is a mystery so far. House batteries are charging perfectly. I did have the alternator rebuilt and may have to revisit that. I also took the positive off the engine batteries and they do not discharge. Perhaps the po hooked something up I am unaware of.I could install a shutoff switch I suppose but that will not provide a solution to the problem. Any ideas?
Thank you to all for the help. Brett, welcome back!
'The strength of the effort is the measure of the result'
1995 U320SE
40'
#4740
#17648

Re: Battery woes

Reply #6 –
Quote from: cubesphere –
I have had trouble with my engine batteries as well. I have a freedom 25 inverter and seems to be working. Brett had said to check the settings, however, I could only find a on/off switch inside on the panel and on/off on the outside unit in the bay. inside switch is on and bay is off. I just replaced 3 batteries last week, something is drawing them down and is a mystery so far. House batteries are charging perfectly. I did have the alternator rebuilt and may have to revisit that. I also took the positive off the engine batteries and they do not discharge. Perhaps the po hooked something up I am unaware of.I could install a shutoff switch I suppose but that will not provide a solution to the problem. Any ideas?
Thank you to all for the help. Brett, welcome back!

The inverter doesn't charge the engine batteries. If they hold a charge with the cable off you do have a drain. A possibility would be the diodes in the alternator. Unhook the output cable at the alternator and see if the draw is still present. If it is then trouble shooting the systems that draw off the engine battery is necessary to fix the problem. You can install a cutoff switch like the ones used in marine applications but that only is a stop gap.

1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
2014 Grand Cherokee Overland
Dream as if you will live forever. Live as if you will die today.  James Dean

Re: Battery woes

Reply #7 –
Yes, OE the chassis battery is NOT charged.

And, you can not reasonably get rid of all the parasitic loads.

Common solution is to arrange for charging of the chassis batteries.

Good options include:
A "smart thief" device such as Xantrex Echo Charger that takes power from the house bank to keep up the chassis battery, with the house bank charged by converter, inverter/charger.

Solar-- can be used for both battery banks if shore power is not available where you store it.

Separate, small, smart charger (120 VAC) dedicated to charging the chassis battery.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Battery woes

Reply #8 –
Hello,

Thank you for the responses, I will check the alternator again after disconnecting the wires. I had no idea that the engine batteries can discharge in 4 days of sitting, strange. Brett, I will look at some charging options as you suggest and I did buy a marine grade shut off just in case I need it short term. Thanks guys!
'The strength of the effort is the measure of the result'
1995 U320SE
40'
#4740
#17648

Re: Battery woes

Reply #9 –
Battery's are still good! The inverter is as well. What we thought was a transfer switch issue turned out to be surge guard installed under bed after the transfer switches. Going to rewire it out of our lives and buy plug in style.
 Lesson for Shaw family: KEEP CHARGER ON!
Tom
1998 U320 40'