[C320-list] Battery Charger

[Warren Updike]

OK, so, I could be wrong. I have been wrong in the past.  I hate the taste of crow; but, not as much as I hate being ignorant.  I'm going to call on my friend and mentor Nigel Calder...
OK, Nigel says (3rd edition) "To be safe, anytime a system is designed to hold sustained charge rates above 10%-15% of battery capacity, and especially if the target is in the 25% or higher range, the voltage regulator... must include temperature compensation...sensing at the batteries (not at the regulator.)"
So what happens is that as a battery's temp rises the voltage at which the electrolyte will gas (boil off) drops.  Failure to sense battery temps results in boil-off at lower temperatures.  The sensor allows the charge regulator to cut back the voltage as battery temp rises.  
One must consider both charge sources: alternator and shore charger.  For most of us, the shore charger is not the issue.  For a single 180AH 4D, 15% is 27A and 25% is 45A.  For a paralleled 4D bank (360AH,) the numbers are 54A and 90A, respectively.  A 40A shore charger is not likely to raise these battery temps by very much.  Neither is a stock 50A alternator.  However, with a high output alternator of 100A or more, sustained output of 60A to 80A is possible for a heavily discharged bank.  What is sustained?  Nigel doesn't say.  Certainly more than a few minutes.
It's not unusual for temps here in Baltimore to reach 90deg. in July and Aug.  With batteries sequestered in an enclosed space battery temps can easily rise to 100deg or higher when being charged.  Our house bank is 2 parallel 4Ds of nearly 400AH.  When discharged to 50-60%, a sustained nominal (unregulated) charge voltage over 14V in absorption phase is likely.  The gassing voltage at 100deg is about 14V.
So, I agree with Jeff, temp sensing and/or a timer will likely prevent thermal runaway, however, battery temp sensing where sustained charge currents are possible will also prevent excess gassing (overcharging.)  Admittedly, for most of us, under conditions experienced most of the time, overcharging is not much of an issue.  If your charge sources are rated less than 15-20% of your bank capacity you might skip battery temperature sensing.  
Since I've replaced two sets of batteries because of excess gassing, when replacing my shore charger I opted for the battery temperature sensor device.  Better safe than sorry.  BTW, I have battery temp sensing on both shore charger and alternator, as well as alternator temp sensing.  
Nothing about battery management is simple or straight forward.
Jeff, do chime-in.

Warren & Pattie Updike
1994 C320 #62 "Warr De Mar"


-----Original Message-----
From: Jeff Hare [mailto:catalina at thehares.com] 
Sent: Wednesday, October 24, 2012 2:44 PM
To: C320-List at Catalina320.com
Subject: Re: [C320-list] Battery Charger

Interesting.  I thought that the battery temp sensor was only really useful for preventing thermal runaway when charging or equalizing.  Especially when the charger is used in situations where they are exposed to hi ambient temps (like engine rooms, etc.).

I wouldn't think it would make any difference at all until the batteries start seeing > 100 degree F temps due to charging.

I may have to research this some more myself.

Jeff

Warren Updike <wupdike at hotmail.com> wrote:

>I beg to disagree.  I recommend including the battery temp sensor to 
>insure proper and full charge.  Cost is nominal and benefit is 
>demonstrated.
>
>Warren & Pattie Updike
>1994 C320 #62 "Warr De Mar"
>
>
>-----Original Message-----
>From: JJ Morrison [mailto:sail-ability at sympatico.ca]
>Sent: Tuesday, October 23, 2012 11:56 AM
>To: Catalina List
>Subject: Re: [C320-list] Battery Charger
>
>
>I ditched my Pro Mariner last year for the Xantrex  TrueCharge 2, 40Amp 
>and I did the same thing on my previous boat. They work great and have 
>good features. I would go for the 40amp as 20 amp is not quite up to 
>the job of charging the 4D batteries on the C320 especially if the boat 
>is used often and the batteries are frequently discharged. If the boat 
>is only used on the weekends and has a few days to recharge then the 
>20amp will probably suffice. If you are using the boat in warm climes I 
>also would not go for the temperature monitor and use the charger at 
>the default warm setting.
>I got a really good deal on the charger from Abe's of Maine, cheaper 
>than Defender Marine.
>Cheers
>JohnM
> 
>
>> Date: Tue, 23 Oct 2012 11:36:09 +0000
>> From: hcreech at comcast.net
>> To: C320-List at Catalina320.com
>> Subject: Re: [C320-list] Battery Charger
>> 
>> Donald,
>> Can't go wrong with the Xantrac 20 or 40. Quiet and efficient , I
>replaced
>the noisy and inefficient Pro-Mariner with the Xantrac 20. Very easy to 
>install although some modifications were necessary. Went from an 
>average battery life of 3 years to over 5 years and counting.
>> 
>> Herb Creech
>> Cloud Chaser 606
>> 
>> 
>> 
>> 
>> ----- Original Message -----
>> From: "Donald Poole" <dpoole15@ gmail .com>
>> To: c320-list at lists.catalina320.com
>> Sent: Tuesday, October 23, 2012 6:26:58 AM
>> Subject: [C320-list] Battery Charger
>> 
>> My Newmar HDM 50 battery charger just died. Anyone ever replaced on
>of
>> these and can advise as to the current Newmar model or an equal by 
>> another mfg? I have two banks (12V, 6 cell lead acid).
>