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MK coach batteries

My coach still has the original (3) coach batteries. 11 years old. On a recent trip I noticed the inverter drew the batteries down quicker than usual. My question is about life expectancy. Should these be changed just because of the age?  Kept in doors and not subjected to temp extremes.

David
David West
2001 U320 40'

Re: MK coach batteries

Reply #1 –
11 years is getting up there for batteries.  I think it's time for new ones.  Make sure that they are identical batteries and that the date codes are current.  The letter stands for the month the year is two numbers.  Some manufactures use a different system IE:

Interstate Batteries FAQ :: How can I tell the age of my battery?

Gel cell or AGM batteries are my choice for price/performance.  Make sure that your charger is set up for them or you will ruin them.  No higher charge voltage than 14.2 volts.

Keith
Keith, Joyce & Smokey the Australian Cattle Dog
1995 U320 SE Extreme 40' WTBI Build # 4780, with a Honda CR-V hopefully still following behind.
Motorcade # 17030
FMCA # F422159

Re: MK coach batteries

Reply #2 –
What type/size of battery?
A sealed Gel could still have 75% of original amphour capacity, while a sealed AGM will not likely have more than 60% and an open wet cell more than 30% - such is the nature of batteries. I have a 12 year old 8D gel which still has and amphour capacity of 170, measure with a ten hour test.

Answer to question involves shades of gray. How often do you  need the batteries for power and are they providing that power today? Batteries seldom suddenly fail (ie short out), however, they sometimes do and maybe one of the three you have has failed. Removing the failed battery may solve your perceived problem. Determining this involves isolating and measuring stabilized voltages for each battery.
 
What stablized voltage does each battery read when recharging is started, when fully charged, and finally 12 hours after being charged while remaining isolated?
Stabilized voltage is read after at least two hours with battery disconnected.

Measuring voltages as batteries are being discharged or charged, or when batteries are ganged together will not provide meaningful information.

Determine how many amphours you are using between recharge cycles. Knowing this provides the information needed to determine how many batteries you really need. For some folks, one 8D is suffcient, for most folks two 8D are sufficient, and for others three is not enough. This is a whole new topic.

Wyatt
96 U320 40 WTFE, build 4943
84 Toyota Supra towd
2015 Jeep Wrangler towd
Victoria, BC, Canada

Re: MK coach batteries

Reply #3 –
We are in the same boat.  Our batteries were completely discharged on our trip this summer by accident.  I or someone had turned off the autostart for the genny, we were running the inverter while going down the road (In motion TV).  We stopped for the night and did not notice the auto start was off.  We ran the batteries down to the point where the inverter threw an error.  We reset the inverter, started the genny and let it charge the batteries. 

Now they won't hold a charge much more than an afternoon.  So, we are replacing with new MK's.  I feel that 11 years is good life for a battery and they have never given us any problem before.

FOT is replacing them before the GrandVention. 

Tom & Bill

2013 Jeep Grand Cherokee

Re: MK coach batteries

Reply #4 –
The gel batteries in Forrest are 7 years old.  I disconnect them while in storage.  When I go to exercise the coach every 30 days, the voltage is still at 12.8VDC.  These have never been discharged to the 50% (12.2VDC) ever.  That alone makes a great difference in longevity of these.  I will use these for quite a while yet.  If you are hooked to shore power, then the batteries will never be taxed by heavy inverter use.  This all depends on your particular needs and style of camping.  For example, when we camp at National Parks w/o hook-ups, we are extremely stingy on 12VDC usage and keep an eagle eye on the batteries state of charge (with a DVM, not the Javelina read out.).

As usual, your results may vary.

Peter
Peter & Beth Martin
No Forrest? What have you done?
MC# 15890 until Dec 2016; FMCA #F329677
Cincinnati, OH

Re: MK coach batteries

Reply #5 –
Thanks everyone,

As we mostly are hooked to a shoreline, I have never experienced a total discharge. The day I suspected something, we were on a short trip and had trouble cranking the engine and had to use the boost feature for 3 days. Found out later the culprit was a ground issue at the main cranking batteries. One will realize real quick how important the voltage levels are when your tranny and everything else starts to go haywire!!!!

Wyatt, I am going to test them as per your instructions. I think at the end of the day I will be OK. The issue hasn't happened again since then and we have been on two more trips. Using all that boost power power and not getting recharged correctly may have been all that happened.

If genny is on auto start, then monitoring the length of time (and usage) should give me a good reading as to how long they will last without having to recharge?


Thanks,
David
David West
2001 U320 40'