[Latitude 28]

Found a potential disaster waiting to happen.  I notice that my coach batteries (Interstate 8D) where cooking on shore power in the float charge mode.  Went back into the settings on the Heart Interface Link 2000 and found the battery amp hour setting set to an abnormaly high number (don't remember the number).  The batteries had a marking of "CCA 1400" with no AMP hour markins.  The battery manufacturing spec is a 270 AMP hour rating.  Given two parallel strings I changed the setting to 540 amp hour capacity.  The batteries are now charging as they are supposed to be charged.      NOTE;  Just realized what I wrote, this setting is incorrect.  I can't have two parallel strings as that would be 24 volts.  If the battery installation was done correctly there should be six 12v batteries in parallel given me 1620 amp hours @ 12v.  I will have to go back and check the layout to verify.  

What I suspect happened, someone changed the AMP hour setting (recent battery install) to some number based on the CCA rating which resulted in the charger thinking we had a huge battery bank.  If this setup had continued unabated I would be buying new batteries before long.

 
 Steve

[Richard]

Steve,

Here are some things to think about. First, if the battery has a CCA number on it, that is a cranking battery. And although it will work just fine in the house battery bank, they are not designed for deep discharge. They will work just fine for running the fridge off the inverter, but not very good for boondocking. I may have misinterpreted your nomenclature when I read "coach" batteries. I am assuming you meant the house batteries, and not the cranking batteries.

In my experience, batteries boiling usually is associated with one bad cell in one of the batteries. The charger is supposed to taper the charge based on voltage. One bad cell will drag the voltage down enough so that the charger thinks the batteries are not charged. Of course, stopping the charge cycle, letting the batteries sit for a couple of hours, and measuring the battery voltage will tell you a lot. So, would hydrometer readings on all the cells.

I would also check the Xantrex settings to make sure that the charger is not in the Equalize mode.

And I may be dead wrong, but I don't think the amp hour setting in the charger has much to do with how much amperage the charger puts out. This is easy enough to check, look at the charger amperage output, then change the amp hour setting and see if the amperage output changes.

If the batteries are cooking in the float mode, I really think something else is going on.

[RussWhite]

Richard is right. Amp-Hour setting not associated with how the batteries are charged. Your Link 2000 will display charging amps and volts. When floating look for something like 13.4 volts. I think you will be needing new batteries as I suspect the problem is with them and not the inverter/charger. Russ

[Latitude 28]

Richard,
You're correct in your interpretation, I used the word coach battery in reference to house batteries and not meaning the cranking batteries.   The P.O. had some issues with the house battery bank and had the selling dealership change out a couple of the batteries with new ones.  There now is an imbalance between the new and old batteries.  That would explain a voltage issue with the charger thinking there is a bad cell or two in the mix.  If it quits raining tomorrow I will check the voltages of each battery. 

Russ,
When the batteries where gassing In float I didn't catch what the float voltage was at that time I will pay attention the next time around.  This looks like a good time to pick out two of the best and put them on "cranking duty" and pick up some deep cycle batteries for the house bank.

[Latitude 28]

Checked house battery voltages today...after a complete charge cycle up to and including three hours or so in float (13.4v).  Did not have any gassing like i had before.  Checked each battery after three or four hour rest....each battery was at 12.85v with one at 12.87v.  Have not had a chance to check specific gravity.  The only setting I have messed with (post gassing events) is the total amp hour setting.  I am pretty sure I did not initiate an EQ charge cycle before the gassing event(s) but the batteries sure sounded like they were in an EQ charge cycle even thought the Link 2000 indicated "float".   The batteries acted normal this time around during the float cycle.....(13.4v).

[Richard]

That is curious. Voltages look good. I wonder what the individual batteries would read under load. The newells have a built in load tester. Just let the 120v water pump run off the inverter. If you have a bad battery it should show up under load if you measure the voltages.

---

Oh yeah, one more thing. If the amp hour setting is indeed the culprit, you could change it back to see if the gassing returns.

[Latitude 28]

We are going on a three day trip....the second one as a family.  I will check the batteries under a load as you suggested.  When we get back I will change the amp setting....don't want to mess around with while on the road.

Richard, thanks for the sugestions!

[Latitude 28]

Follow-Up
Since the last post we had only one event where the batteries where gassing.  I was not able to catch the scenario and write any numbers down, that was back in April.  Yesterday checked the Link 2000.  Pushed the volts button then battery 1 & 2.  The link 2000 locked up.  Followed the book on the proper Link 2000 shutdown i.e., shore power disconnected, battery bank 1&2 off, inverter off....still have power to the Link 2K....with one exception.  I can't find the fuse that powers it....does anyone know where it might be?  

Thanks
Steve

[bestgenman]

Steve,  our coaches are not that far apart so there is a good possibility it may be wired similar.  The negative disconnect on mine only disconnects the house loads and not the inverter negative.  My inverter fuse is in the same bay as the inverter, it is ~300amps with a cover that may be carpeted.

Stealing Richard’s diplomacy, battery voltage should be measured with one of the posts disconnected for an accurate measure.  Mixing new and old is never a good idea (as you mentioned), and the only true determination (in my opinion) is specific gravity.  Easy for you to do with non deep cycle types with removable caps. AGM batteries will not have caps.  The rule of thumb for converting CA (not CCA) is CA/7.25.  It’s only a guess but close enough to calculate capacity loosely.

If you want all loads disconnected, remove the negative from the string to the stud terminal on the bulkhead.  When you reattach, you’ll likely get a big spark as the capacitor bank in the inverter charges up.

[Latitude 28]

Gordon,
Thanks for the heads up!  Ah Ha...Disconnecting the inverter that makes sense.  I don't like sparks, but will go give try and report back. 

Steve