Re: Batteries: single failed battery in the house bank, impact for other batteries


I am not sure, and I believe you believe the same. With thousands of miles ahead of you and 3+ year old battery bank, I would consider changing the entire house bank, especially since getting 3-4 years is average for high-use Amels. 

Good on the lead acid start battery. 

When troubleshooting the Onan, I believe the weak point is the cable that runs inside from the negative connection post to the battery side of the Negative start solenoid.  The connection post where cables from the battery switches connect is located on the left side, facing, about half way down. I believe you can easily bypass this undersized cable by connecting a jumper from that connection post to the battery side of the negative start solenoid. You could also test the negative start solenoid by connecting that jumper cable to the starter side of the negative solenoid. 1 jumper cable can be used to test two items. If the problem turns out to be the negative start solenoid, don't leave that jumper on the starter side of the solenoid permanently.


CW Bill Rouse
Yacht School - Supporting Amel Owners
720 Winnie St
Galveston Island, TX 77550
+1(832) 380-4970

On Sun, May 26, 2019, 11:24 AM David Vogel <david.vogel@...> wrote:
Greetings all,

Whilst trouble-shooting an unserviceable ONAN (failure to crank), I checked out the health of the 105Ah 800CCA AGM start battery (good), and house-bank (12x105Ah AGMs).  Start and house batteries were all AGM, same model and date-of-install (Sep'16).

All tested OK, with the exception of one battery in the house bank, which failed the State-of-Charge test with an Open-Circuit-Voltage (OCV) of 11.00V (as measured, so no surprises here), unstable; and failed State-of-Health of CCA of 35.0A).
The other battery in the pair containing the failed battery surprisingly tested OK, with SoC 12.72V [92%] and SoH CCA of 642A [91%].

As an interim step, whilst considering broader options ...
... I replaced the good start-battery with a 100Ah/700CCA flooded lead-acid battery; removed the failed AGM battery from the house bank, and replaced it with the 'good' AGM start battery.  The performance of the house battery bank immediately improved, I guess due to the absence of the parasitic load of the failed battery.

However, concerned about the remaining battery in the new pair contained the failed battery, I have been keeping a close eye on the charge volts, current, and temps of all batteries.  24 hours after the swap-out/in, during the second charge cycle, I noted high charging current to the new battery-pair containing the old-start battery.

The smart-charger was ordering ~150Amps from the 175A/24V Leece-Neville (normal for the start-of-charge-cycle) - 5 battery-pairs were accepting about 20Amps each (OK and as expected, at ~20% of the '20-hour rate' of 105Ah), but the 'at risk' pair was accepting 40 to 50Amps.  Temps for the 5 'good' pairs were about 1ºC above ambient and stable; but the temp of the questionable pair was ambient +2ºC and rising.  I stopped the charge cycle after 30 minutes; and isolated the questionable pair from the house-bank by removing the bridging strap between the batteries in the pair.  Shortly after the cessation of the interrupted charge cycle, the temperature of the high-current pair peaked at 36.5ºC (ambient other batteries +2.5ºC).

I am seeking clarification regarding: Is is likely that the remaining battery from the 'old pair' had already suffered irreversible damage (such as an internal short), thereby reducing internal resistance, thereby accepting a higher charge (than the other 'good' battery pairs).

On the basis of temperature alone , I do not think I have suffered temperature-related damage to the old start battery.  However:

Question - is it likely that 30-minutes of charge at twice the maximum recommend bulk/absorption current charge-rate has resulted in permanent damage to the previously 'good' start-battery?

This discussion shared for the learning, and also for the benefit of trouble-shooting by other unfortunates who may in future find themselves in a similar predicament.

Thanks in anticipation ...

On anchor, Brisas, Pacific side of Panama
  Departure for the Marquesas pending the
    return of the ONAN to service

Diagnostic tools: Magneti Marelli BT002 Battery Tester; FLIR TG165 Spot Thermal Camera; Voltcraft VC-595OLED Digital Clamp Multimeter.
Note: the OLED display on the Voltcraft multimeter is impossible to read in direct sunlight, so next time I would choose a model with a different type of display.  Otherwise, this is a great tool, although I do not use the BlueTooth functionality.

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