[C320-list] Battery Isolation

Kirk McCullough kirk.mccullough at telus.net
Sat Apr 18 15:27:35 PDT 2009 

Is it not just about as easy to leave the house and starting batteries 
un-combined or un-isolated and just select which one to charge with the 
1-2-both switch? That's what I do and the starting battery is always good to 
go. I don't use it for anything but starting and even then if I happen to be 
on house while at anchor I often just use them to start the engine.

I didn't see or maybe didn't properly understand the benefit of the ACR when 
it was explained to me recently, so I just bought a new Blue Sea 1-2-Both 
switch when I bought new 4D deep cycle batteries last fall, just to be sure 
I wasn't getting any leakage across my old original Guest 1-2-Both I 
replaced it. All is good.

Kirk
#124

----- Original Message ----- 
From: "Jeff Church" <jc387 at att.net>
To: <C320-List at Catalina320.com>
Sent: Friday, April 17, 2009 7:35 PM
Subject: Re: [C320-list] Battery Isolation


>
> Bob,
>
> Me too. That's why I thought as soon as the combiner closes, current from 
> both the charger and starting battery would flow through the house 
> batteries until the resistance of the house bank increased.
>
> What would happen if there was a shorted cell in the house bank? With a 
> combiner couldn't the starting battery discharge thru the shorted house 
> battery?
>
> I was also told by the guys at Charles that since the discharged house 
> batteries present the least resistance, most of the bulk and absorption 
> charge will flow thru them, so the smaller starting battery will not over 
> charge.
>
> Jeff
>
>
> Robert Seastream wrote:
>> I thought a discharged battery has an extremely low resistance, thus 
>> presenting a near short to any charging source.
>>
>> Bob Seastream
>>
>>
>> On Apr 17, 2009, at 10:00 AM, <crashley at gte.net> wrote:
>>
>>> At the risk of offending Orlando again, I'll take a crack at this. When 
>>> you
>>> turn the charger on into an open circuited or discharged house battery, 
>>> it
>>> takes a little while (several seconds) for the battery voltage to climb 
>>> up
>>> to the initial charging voltage which should be about 14.4V. This delay 
>>> is
>>> because the battery looks like a large capacitor. The ACR has a time 
>>> delay
>>> in it so when it senses that the house battery voltage is 13.5V (or 
>>> higher)
>>> the timer starts and 30 seconds or so later the relay closes. At this 
>>> point
>>> the house battery is at 14.4V and the starting battery is at 12.7V (open
>>> circuit voltage) so it will start charging too. I think the only 
>>> possible
>>> issue here is that if the house battery is a lot larger than the starter
>>> battery, which is normally the case, the starter battery will see a 
>>> longer
>>> "absorb" charge time than it needs, but I don't think this is a big 
>>> problem.
>>>
>>> Long live space junk!
>>>
>>> CR Ashley
>>> Rosebud C320 Hull #882
>>>
>>>
>>>
>>>
>>> -----Original Message-----
>>> From: c320-list-bounces at lists.catalina320.com
>>> [mailto:c320-list-bounces at lists.catalina320.com] On Behalf Of Jeff 
>>> Church
>>> Sent: Wednesday, April 15, 2009 10:57 AM
>>> To: C320-List at Catalina320.com
>>> Subject: Re: [C320-list] Battery Isolation
>>>
>>> Chris,
>>>
>>> Like I said, maybe I didn't totally understand what the guys at Charles 
>>> and
>>> PS (2 independent sources) told me.
>>>
>>> Why wouldn't the ACR sense 14 volts, or more, the moment that the 
>>> charger
>>> switches on? My battery monitor does. I know that there will be some 
>>> voltage
>>> drop due to the discharged house, but the charger output is
>>> 15 or 16 volts initially.
>>> .
>>> Jeff
>>>
>>>
>>>
>>> crashley at gte.net wrote:
>>>> I disagree. It doesn't surprise me that the guys who make the
>>>> expensive MOSFET devices will tell you what they did. The ACR will not
>>>> close until the battery being charged reaches 13.5V. The starter
>>>> battery should be sitting at around 12.7V before that so it will not
>>>> discharge into the higher voltage battery, it will actually start
>>>> receiving charge current as well. I agree that the ACR will allow
>>>> current to go in either direction, but in this case it should not. The
>>>> only time this might occur is if the charging source goes away in
>>>> which case the ACR will open when the house battery drops to 12.7V, so
>>>> it should not allow the starter battery to discharge too much into the
>>> house battery since 12.7V is a fully charged state for lead acid 
>>> batteries.
>>>>
>>>>
>>>> PS: I am an EE and have been designing battery chargers and
>>>> dischargers for spacecraft for 28 years. Talk about $$$$!
>>>>
>>>> CR Ashley
>>>> Rosebud C320 Hull #882
>>>>
>>>>
>>>> -----Original Message-----
>>>> From: c320-list-bounces at lists.catalina320.com
>>>> [mailto:c320-list-bounces at lists.catalina320.com] On Behalf Of Jeff
>>>> Church
>>>> Sent: Tuesday, April 14, 2009 10:53 PM
>>>> To: C320-List at Catalina320.com
>>>> Subject: Re: [C320-list] Battery Isolation
>>>>
>>>> When I was designing my setup I spoke at length to several engineers.
>>>> The techs at Charles and Perfect Switch (PS makes MOSFET isolators
>>>> ($$$$) for the military and NASA) told me about this particular 
>>>> problem.
>>>>
>>>> My understanding is that when the charger comes ON, the ACR senses the
>>>> voltage and the switch closes. At that point current flows from any
>>>> available source towards the path of least resistance. In this case
>>>> the house batteries are the path of least resistance and current will
>>>> flow from both the charger and the starting battery to the house
>>>> batteries until the resistance in the house and starting batteries
>>> equalizes.
>>>>
>>>> An isolator does not allow any current to pass from one battery bank
>>>> to the other.
>>>>
>>>> I'm not an EE so maybe I got it wrong.
>>>>
>>>> JeffC
>>>>
>>>>
>>>>
>>>> crashley at gte.net wrote:
>>>>
>>>>> JeffC,
>>>>>
>>>>> The Blue Sea Systems battery combiner relay (ACR 7600) has a voltage
>>>>> sensor so it will not close until the house battery is being charged
>>>>> at 13.5V so the starter battery should never discharge into the house
>>>>>
>>>> battery.
>>>>
>>>>> CR Ashley
>>>>> Rosebud C320 Hull #882
>>>>>
>>>>>
>>>>> -----Original Message-----
>>>>> From: c320-list-bounces at lists.catalina320.com
>>>>> [mailto:c320-list-bounces at lists.catalina320.com] On Behalf Of Jeff
>>>>> Church
>>>>> Sent: Wednesday, April 08, 2009 5:59 PM
>>>>> To: C320-List at Catalina320.com
>>>>> Subject: Re: [C320-list] Battery Isolation
>>>>>
>>>>> Good info. I looked all over for a Schottky diode isolator and didn't
>>>>> find out that Guest made one. It also didn't occur to me that
>>>>> relay-type devices could create RF noise. I just found the Guest unit
>>>>> (#2530) at Pyacht.com for about $140.
>>>>>
>>>>> I recently installed a Sure Power Schottky-diode isolator when I
>>>>> installed a starting battery on my 387. According to several sources,
>>>>> using an isolator is a better approach than using any of the
>>>>> combiners or other relay-type devices. The biggest problem with a
>>>>> combiner/relay is that when the charging device initially starts and
>>>>> the combiner closes, the depleted house bank can immediately draw a
>>>>> lot of current from the  starting battery. Some of the devices like
>>>>> the Echo Charger might not operate that way, but you should check on
>>>>> that before buying one. The advantage of the combiner is that it is
>>>>> easier to install and
>>>>>
>>>> less wire ($$) is required.
>>>>
>>>>> In order to install an isolator you will need to remove the wire that
>>>>> connects the alternator to the starter motor, and run a #6 wire from
>>>>> the alternator to the input terminal on the isolator. Then from the
>>>>> #1 and
>>>>> #2 output terminals on the isolator you run wires to the battery
>>>>> switch
>>>>> #1 and #2 terminals, or directly to the house and starting batteries.
>>>>>
>>>>> Good luck.
>>>>>
>>>>> JeffC
>>>>>
>>>>>
>>>>>
>>>>> jelliott at landspring.net wrote:
>>>>>
>>>>>
>>>>>> I'm learning more... These are relay-based devices; Blue Sea tech
>>>>>> support says they may induce RF noise if installed at the panel vs.
>>>>>> at the battery (not desirable in my case).  Have you experienced 
>>>>>> this?
>>>>>>
>>>>>> The Guest isolators use Schottkey diodes, which induce a load (and
>>>>>> corresponding heat), but don't suffer the potential RF problem.
>>>>>>
>>>>>> As usual, there is a tradeoff...
>>>>>>
>>>>>> Julian
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>> The Yandina is the one I used (mine is a WM re-label of this
>>>>>>> product.) It's as simple as described. The Blue Seas Relay will
>>>>>>> definitely do the trick as well...
>>>>>>>
>>>>>>> Regards,
>>>>>>>
>>>>>>> Jon Vez
>>>>>>> Solstice #582
>>>>>>>
>>>>>>> -----Original Message-----
>>>>>>> From: c320-list-bounces at lists.catalina320.com
>>>>>>> [mailto:c320-list-bounces at lists.catalina320.com] On Behalf Of
>>>>>>> jelliott at landspring.net
>>>>>>> Sent: Wednesday, April 08, 2009 4:09 PM
>>>>>>> To: C320-List at Catalina320.com
>>>>>>> Subject: Re: [C320-list] Battery Isolation
>>>>>>>
>>>>>>> John,
>>>>>>>
>>>>>>> I see WM has a Blue Sea Systems Starting Isolation Charging Relay
>>>>>>> which seems to do the trick.  Is that what you installed?
>>>>>>>
>>>>>>> Also seen similar items from Guest and from a company called
>>>>>>> Yandina (http://www.yandina.com/NewCatalog.htm).
>>>>>>>
>>>>>>> Looks like this fits the bill with a fairly straightforward
>>>>>>>
>>>> installation.
>>>>
>>>>>>> Almost too simple to be real...
>>>>>>>
>>>>>>> Julian
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>> Julian,
>>>>>>>>
>>>>>>>> I have the exact setup you describe. I used a battery combiner
>>>>>>>> from West Marine. It's a simple device that you simply wire to
>>>>>>>> each pole on the back of your current switch--one wire to the '1'
>>>>>>>> and the other to the '2'.
>>>>>>>> It's
>>>>>>>> about the size of a match box and takes a couple of minutes to
>>> install.
>>>>>>>> It
>>>>>>>> will combine the batteries when motoring via the alternator and
>>>>>>>> isolate them when not receiving a charge. Is the 'easy' solution
>>>>>>>> to this problem....
>>>>>>>>
>>>>>>>> Regards,
>>>>>>>>
>>>>>>>> Jon Vez
>>>>>>>> Solstice #582
>>>>>>>>
>>>>>>>> -----Original Message-----
>>>>>>>> From: c320-list-bounces at lists.catalina320.com
>>>>>>>> [mailto:c320-list-bounces at lists.catalina320.com] On Behalf Of
>>>>>>>> jelliott at landspring.net
>>>>>>>> Sent: Wednesday, April 08, 2009 10:59 AM
>>>>>>>> To: C320-List at catalina320.com
>>>>>>>> Subject: [C320-list] Battery Isolation
>>>>>>>>
>>>>>>>> I am in the process of modifying my electrical system, and am
>>>>>>>> curious as to how others electrically isolate the house bank from
>>>>>>>> the starting battery.
>>>>>>>>
>>>>>>>> I have two 4D's under the settee paralleled as my house bank, and
>>>>>>>> a separate  starting battery located in the port lazarrette.  Both 
>>>>>>>> are
>>>>>>>> connected to independent channels of a Xantrax Truecharge 20.   The
>>>>>>>> house
>>>>>>>> bank is monitored with a Link 10.
>>>>>>>>
>>>>>>>> The banks are still not electrically isolated; I assume this is a
>>>>>>>> result of a common connection to the alternator?  How do others
>>>>>>>> handled
>>>>>>>>
>>>>>>>>
>>>>> this?
>>>>>
>>>>>
>>>>>>>> I
>>>>>>>> understand there are battery isolators that do this?  Any advice
>>>>>>>> on how to "break" this return circuit (if that's the cause) would
>>>>>>>> be appreciated.
>>>>>>>> I
>>>>>>>> am not very interested in adding a second switch which I know some
>>>>>>>> have done.
>>>>>>>>
>>>>>>>> Thanks,
>>>>>>>>
>>>>>>>> Julian
>>>>>>>> Polaris #340
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>
>>

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