What is this.

gmctrucks · 05-21-2009, 06:28 AM

I don't know can someone please explain

Thanks! GMC

Cole Hersee Battery Isolator Guard Max Alternator 12-36:eBay Motors (item 190307674875 end time May-21-09 14:11:51 PDT)

bradrhale · 05-21-2009, 06:49 AM

ebay has been blocked at work. for some reason, i cannot bypass the filters. our new IT man is a genius.

z07 · 05-21-2009, 07:01 AM

Some trucks and RVs have two batteries.

Ever hear or read anyone saying, "If you replace one battery you better replace both because the old one will kill the new one", or something similar?

These let you change the batteries one at a time w/o worries.

75K30 · 05-21-2009, 08:31 AM

Many people listen to their stereo or create other electrical draws without the engine running. This often leads to dead batteries and a vehicle that won't start. A battery isolator will let you completely discharge one or more batteries without discharging the starting battery.
Different Types of Isolators: There are 2 main types of battery isolators. The diode based type and the relay (solenoid) type. The above is the Diode type.
Diode Based Isolator: This type of isolator is basically two very high current diodes in a heat sink. The diode based isolator has the advantage of long life and trouble free operation but many of the diode based isolators cause a .4 to .6 volt loss which means that the batteries will not charge to as high a voltage as when they are connected directly to the alternator. Some diode type isolators have a fourth terminal which controls the current flow through the device.This is all they are for. Isolation.......

z07 · 05-21-2009, 10:13 AM

The forward voltage drop of a diode is roughly 0.6 volts. The emitter-collector drop of a saturated PNP transistor is only 0.2 volts. If the isolator were only diodes then the battery could either only be charged and never discharge or only discharge and never be charged. I haven't seen a schematic of this device but I suspet it is a diode that allows the battery to discharge and a PNP transistor with its base connected to the alt output so that when the alt is putting out volts the battery can charge. And since it is charging through the transistor the difference between full charge without the device and with the device is only 0.2 volts.

crabtruck · 05-22-2009, 01:52 AM

Ah z07, another techy here ! Very true about the Vdrop if using the old silicon types.
Not a useage problem though, since as mentioned, this is for Isolation
and it does just that for charging purposes.
This is some what like syamese twins sharing the alt, but each has its
own load side circuits (eng vs toys) and they share the ground path return,
so they are not truely completely isolated systems.
In normal wiring set up, any hot can bleed from common hot source (batt),
but this creates a barrier between the two groups.
Loads on either side do not threaten the other side.

This is not as good a system as represented, unless modified.
My mother once was in the situation where the eng batt was dead,
but the rv batt was fully charged. No way for her to "jump" the batts herself.
I since modified it with a bypass relay so a single touch bypasses
the isolator and allows starting in those conditions.
The common error in the design is folks assuming the RV side
will be the cause of dead batts, but it's sometimes the other way.

05-21-2009, 06:28 AM	#1
gmctrucks Senior Member Join Date: Nov 2006 Location: Houston,Texas Posts: 4,033	What is this. I don't know can someone please explain Thanks! GMC Cole Hersee Battery Isolator Guard Max Alternator 12-36:eBay Motors (item 190307674875 end time May-21-09 14:11:51 PDT)

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05-21-2009, 06:49 AM	#2
bradrhale Senior Moderator Join Date: Apr 2006 Location: Texas Posts: 8,025	ebay has been blocked at work. for some reason, i cannot bypass the filters. our new IT man is a genius.

05-21-2009, 07:01 AM	#3
z07 Senior Member Join Date: Feb 2008 Posts: 391	Some trucks and RVs have two batteries. Ever hear or read anyone saying, "If you replace one battery you better replace both because the old one will kill the new one", or something similar? These let you change the batteries one at a time w/o worries.

05-21-2009, 08:31 AM	#4
75K30 Senior Member Join Date: Jul 2006 Posts: 2,992	Many people listen to their stereo or create other electrical draws without the engine running. This often leads to dead batteries and a vehicle that won't start. A battery isolator will let you completely discharge one or more batteries without discharging the starting battery. Different Types of Isolators: There are 2 main types of battery isolators. The diode based type and the relay (solenoid) type. The above is the Diode type. Diode Based Isolator: This type of isolator is basically two very high current diodes in a heat sink. The diode based isolator has the advantage of long life and trouble free operation but many of the diode based isolators cause a .4 to .6 volt loss which means that the batteries will not charge to as high a voltage as when they are connected directly to the alternator. Some diode type isolators have a fourth terminal which controls the current flow through the device.This is all they are for. Isolation.......

05-21-2009, 10:13 AM	#5
z07 Senior Member Join Date: Feb 2008 Posts: 391	The forward voltage drop of a diode is roughly 0.6 volts. The emitter-collector drop of a saturated PNP transistor is only 0.2 volts. If the isolator were only diodes then the battery could either only be charged and never discharge or only discharge and never be charged. I haven't seen a schematic of this device but I suspet it is a diode that allows the battery to discharge and a PNP transistor with its base connected to the alt output so that when the alt is putting out volts the battery can charge. And since it is charging through the transistor the difference between full charge without the device and with the device is only 0.2 volts.

05-22-2009, 01:52 AM	#6
crabtruck Senior Member Join Date: Jul 2007 Location: on your 9 Posts: 3,364	Ah z07, another techy here ! Very true about the Vdrop if using the old silicon types. Not a useage problem though, since as mentioned, this is for Isolation and it does just that for charging purposes. This is some what like syamese twins sharing the alt, but each has its own load side circuits (eng vs toys) and they share the ground path return, so they are not truely completely isolated systems. In normal wiring set up, any hot can bleed from common hot source (batt), but this creates a barrier between the two groups. Loads on either side do not threaten the other side. This is not as good a system as represented, unless modified. My mother once was in the situation where the eng batt was dead, but the rv batt was fully charged. No way for her to "jump" the batts herself. I since modified it with a bypass relay so a single touch bypasses the isolator and allows starting in those conditions. The common error in the design is folks assuming the RV side will be the cause of dead batts, but it's sometimes the other way.