Home » Public Forums » GMCnet » [GMCnet] DIY Isolator
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| Re: [GMCnet] DIY Isolator [message #70511 is a reply to message #70427] |
Mon, 11 January 2010 13:46   |
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RF_Burns
Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada
Karma: 3
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Hmmm, if you are going to make a battery isolator, don't you want a common anode, not common cathode?
Here is my crude schematic (I could not find one on-line anywhere)
The alternator connection is at the center |.
this is a diode ->|-
Battery 1-----|<-----|----->|------ battery 2
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
[Updated on: Mon, 11 January 2010 13:50] Report message to a moderator |
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| Re: [GMCnet] DIY Isolator [message #70513 is a reply to message #70511] |
Mon, 11 January 2010 14:14 |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
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yep
looks like this
http://www.gmcmhphotos.com/photos/showphoto.php?photo=5388&cat=3413
gene
On Mon, Jan 11, 2010 at 11:46 AM, Bruce Hislop <bruce@perthcomm.com> wrote:
>
>
> Hmmm, if you are going to make a battery isolator, don't you want a common
> anode, not common cathode?
>
> Here is my crude schematic (I could not find one on-line anywhere)
>
> Alternator connection
> |
> Battery 1-----|<-----|----->|------ battery 2
>
> --
> Bruce Hislop,
> S. Ontario Canada
> 77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI and ESC.
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html
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| Re: [GMCnet] DIY Isolator [message #70523 is a reply to message #70511] |
Mon, 11 January 2010 16:13 |
GMCWiperMan
Messages: 1248
Registered: December 2007
Karma: 1
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Senior Member |
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Jiminy Cricket!!! Why do I keep doing that??? As well as I know
better...Guess I just read what I want to instead of what the letters say...
I'm just gonna crawl off in a corner & keep my mout --- fingers still. :-(
Ken H.
On Mon, Jan 11, 2010 at 2:46 PM, Bruce Hislop <bruce@perthcomm.com> wrote:
>
>
> Hmmm, if you are going to make a battery isolator, don't you want a common
> anode, not common cathode?
>
> Here is my crude schematic (I could not find one on-line anywhere)
>
> Alternator connection
> |
> Battery 1-----|<-----|----->|------ battery 2
>
> --
> Bruce Hislop,
> S. Ontario Canada
> 77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI and ESC.
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] DIY Isolator [message #70529 is a reply to message #70517] |
Mon, 11 January 2010 16:56 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Senior Member |
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I just use a cheap relay--ignition on, batteries connected. ignition off, batteries not connected.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] DIY Isolator [message #70534 is a reply to message #70529] |
Mon, 11 January 2010 17:20 |
idrob
Messages: 645
Registered: January 2005
Location: Central Idaho
Karma: 0
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| Bob de Kruyff wrote on Mon, 11 January 2010 14:56 |
I just use a cheap relay--ignition on, batteries connected. ignition off, batteries not connected.
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Damn, Bob, we are just going to have to drum you out of the group. Simple? Oh my god. No solutions looking for a problem to solve? Now am I going to have to buy some beer for your visit to cogitate about Dan's emergency brake problem?
Sorry, all good fun here. Hope no one takes offense.
Rob Allen
former owner of '76 x-PB
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| Re: [GMCnet] DIY Isolator [message #70614 is a reply to message #70501] |
Tue, 12 January 2010 07:51 |
Erv Troyer
Messages: 125
Registered: February 2004
Location: Lagrange, IN
Karma: 0
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Gene said:
"not in the GMC
the OEM circuit takes care of any voltage drop. (closes the loop)
not a problem"
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Gene, Yep, just what I said -
"Standard diode V-drop is ~ .60 volts, which means you have to work around that to fully charge the batteries."
GMC already did the workaround by having the alternator sensing the battery voltage, not isolator voltage. Works for the engine battery, but the house battery may never get fully charged...
And whenever you add another charging source (gen-set, solar panel, inverter/charger, etc) you will never get full voltage to the battery that is on the other side of the isolator.
My point - I don't like isolators because of the voltage drop problem. I use a Sure Power 1315 battery separator; many others are using the Yandina Combiner. Both these devices make a direct connection between the batteries whenever either one is being charged. No workaround needed.
Erv Troyer Lagrange, IN
74 Sequoia
77 Birchhaven (for sale in spring)
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| Re: [GMCnet] DIY Isolator [message #70624 is a reply to message #70614] |
Tue, 12 January 2010 09:06 |
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RF_Burns
Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada
Karma: 3
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Senior Member |
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Erv,
I'm not sure I understand when you say "the house battery will never get fully charged"
The alternator is basically a float (constant voltage) charging system with remote voltage sense connection at the battery (engine battery only)
Therefore when the alternator starts, it raises its output voltage till it reads its setpoint voltage (14.2V I believe) at its voltage sense input. Since there are voltage drops between the alternator output and the battery (or more correctly the connection point of the remote voltage sense wire), the alternator will output a voltage high enough to overcome these losses.
The IR voltage drop in the alternator output wire are likely to be as high as the isolator voltage drop, I got a new one this summer and it was only 0.3V so its a Schottky type.
Lets just deal with the isolator voltage drop at 0.6V, therefore if the voltage sense is 14.2, the alternator output will be 14.8V to the isolator. The isolator drops the 0.6volts to both batteries, therefore BOTH BATTERIES see 14.2V. Even if we move the alternator voltage sense wire to the House Battery, the result is the same. The 0.6 voltage drop across the diodes is near constant regardless of current flow, so both batteries will see the same charging voltage across them.
If we took out the Isolator and connected the batteries in parallel (same as a combiner without voltage control), then the alternator would output only 14.2V and that is what the batteries would see.
Therefore I don't understand why the house battery would not charge the same... The alternator is not a "Smart charger" measuring battery charge voltage, current and temperature. The alternator never knows whether the battery is charged or not, it has no way of telling.
I just have a waterproof fuse holder across my isolator to provide manual charging from my house charger/power supply. I understood that vehicle batteries are not built to take a constant float charge 24/7, so I just plug in the fuse when I want to charge it from the house.
I'm likely all wet though, so never mind.
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
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| Re: [GMCnet] DIY Isolator [message #70629 is a reply to message #70523] |
Tue, 12 January 2010 10:53 |
Larry C
Messages: 1168
Registered: July 2004
Location: NE Illinois by the Illino...
Karma: 0
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Senior Member |
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Hmmm, if you are going to make a battery isolator, don't you want a common anode, not common cathode?
XX SNIP XX
Unless I have my anodes and cathodes mixed up, aren't the diodes backwards? The description says the device has a common cathode and don't you need a common anode for an isolator? However, it looks like one could cut the common bar in the middle and assemble it the other way around. For the less-than-$4 price I guess I would give it a go.
Gary
__________________________________________________________
Maybe I am missing something here.
At that price, and the H/D ness of the rectifier,,,
It seems to me with a few minor alterations, this would work fine.
It is only a rectifier and changing the common point seems all that is needed.
As far as I know, a combiner is not all that difficult to build.
Even if you had to cut the common bar and bolt on a copper bar to the opposite side, even for a spare its not a bad deal.
LarC ( Of course if the price of a combiner was super cheap, like I am " in a different sort of way " the value of the deal would change. )
Gatsbys' CRUISER  08-18-04
74 GLACIER X, 260/455-APC-4 Bagg'r
Remflex Manifold gaskets
CampGrounds needed, Add yours to "PLACES" />
http://www.gmceast.com/travel
_
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