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I'm installing the PAC PAC-200 200-Amp Relay Battery Isolator

I have connected the positive battery terminal from my starter battery onto one of the larger isolator posts, and the other larger isolator post is connected to my aux battery.

The two smaller posts on the isolator are used to connect the device to 12v power, to turn and keep the unit "on" only when the engine is running.

So:

How or what do I physically connect to the two smaller posts of the isolator to make it get 12v power only when the engine is on, and also to connect it to ground?

Thanks!
 

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Blake,

According to the instructions,

"The two small terminals are for switching the relay on and off. Either one of the small terminals should beconnected to chassis ground or other ground location and the other terminal to switching power output. Switching power must be between 10 and 16 VDC. The relay coil draws less than 1amp when switched on."

So, take one of the small terminals and attach it to ground. If the isolator is bolted to the van chassis, this would be a good spot, just a short wire.
The other small terminal is connected to any wire that goes on and off with the van. On my van, I ran an extra wire spliced to the cigarette lighter in the dash. That wire only goes on when the van is on.

Depending on where your isolator is located, you may find a wire that goes on with the van at a closer location.

You may also want to put a switch in line with the wire going from the ignition-on wire to the small terminal on the isolator. That will allow you to turn the isolator off if you wanted to.

Ed

ps. the important part is the large posts. The wires going to them should be fused, big (6AWG or more) and as short as possible!
 

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Good advice above. I also placed an intermediate switch in the wire to the cigar lighter so I can activate the isolator (I call it an interconnect) when I need it which is almost never. I have 200 watts of solar and that runs the coach battery full in about 3 hours after a night of videos, refrigerator, LED lights, fan etc. If we have a rainny day or two I switch the interconnect on and let the alternator charge the coach battery. This way I know the batteries are isolated nless two things are true. The van is running and the interconnect switch is ON. Handy!
 

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To get access to switched 12v power you can also tap into the fuse box. It's down and left from the steering wheel behind a plastic panel held on by two screws. Some of the circuits are switched and some aren't. I believe that the top left two 5A circuits are switched but you have to check for yourself. You can use one of these (or equivalent) [ame]http://www.amazon.com/Pico-0956PT-Blade--Circuit-Holder/dp/B001QRSBW0[/ame] to add a circuit with a separate fuse. Pepboys has them if you don't want to order online.

EDIT: fixed the link
 

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I am using the Battery Doctor Isolator [ame]http://www.amazon.com/WirthCo-20092-Battery-Doctor-Isolator/dp/B0058SGDFK/ref=sr_1_1?ie=UTF8&qid=1463675886&sr=8-1&keywords=battery+doctor+isolator[/ame] it is very simple to hookup. From starter battery to isolator, isolator to aux battery and a common ground wire. Nothing else needed. It automatically disconnects the aux battery when the vehicle is not running. When the vehicle is running it senses the starter battery charging, and connects the aux battery.
 

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Ratz,

I have that too. The PAC isolator is just a simpler version... looks pretty solid!

I do note on mine that sometimes the blue charging light that is supposed to go off when it senses the van is not running, does not always do so. Sometimes I notice it stays on for a while after the van is turned off. Doesn't seem to have any impact on the charging of my dual aux battery system.

Ed
 

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Ratz,

I have that too. The PAC isolator is just a simpler version... looks pretty solid!

I do note on mine that sometimes the blue charging light that is supposed to go off when it senses the van is not running, does not always do so. Sometimes I notice it stays on for a while after the van is turned off. Doesn't seem to have any impact on the charging of my dual aux battery system.

Ed
The Battery Doctor does say the blue light will stay on till it senses the starter battery is being used and after 60 seconds of the voltage dropping below 12.8V the blue charging light will turn off and disconnect the two batteries.
 

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Hey I have a question: What's the capacity of the PM alternator? charging an extra battery won't overload it?

Thanks in advance.
 

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Hey I have a question: What's the capacity of the PM alternator? charging an extra battery won't overload it?

Thanks in advance.
I have two 100 amp house batteries and it doesn't phase (ha, ha) the alternator when I connect them up in the slightest. I think the stock alternator on gasser is 160 amp but I'm not sure.
 

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Standard alternator on the gas engine is 180 amp and the optional one is 220.
 
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Hi,
I have a similar relay type isolator and two 220 amp-hr 6 volt golf cart batteries hooked in series to make 12 volts. These are flooded lead acid batteries.

I've measured the charging current with the batteries in a low state of charge a couple times and about the highest charging current I've seen is 38 amps. AGM batteries might make for somewhat higher charging currents, but 38 amps is a long ways short of 180 amps.

Gary
 

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In a situation where the two aux batteries are close to dead, and the van battery is also almost gone too, it would be interesting to see what charging current the alternator provides. It's all controlled by the alternator's regulator, so I think it would just provide what it could until everything was brought back up to charged.
 

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Alternators are often, not always, over rated as there are many standards and methods for rating them. To get maximum rated output the alternator must be physically cold, running at max RPM, and putting its output into almost zero resistance. Even "dead" batteries have some resistance and alternators physically heat up within minutes especially when they are putting out max amps. When batteries are half charged it is very common for the alternator output to be less than half of the rating. Auto alternators are especially often over rated.

Edit: I add that in typical automotive applications pulley sizes are such that the alternator turns at twice the engine RPM. At engine RPM of 2500 the alternator is spinning at 5000 and bearing friction causes a quick temperature rise.
 

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Hi,
I have a similar relay type isolator and two 220 amp-hr 6 volt golf cart batteries hooked in series to make 12 volts. These are flooded lead acid batteries.

I've measured the charging current with the batteries in a low state of charge a couple times and about the highest charging current I've seen is 38 amps. AGM batteries might make for somewhat higher charging currents, but 38 amps is a long ways short of 180 amps.

Gary
Gary
What size wire are you using between your chassis battery / alternator and house batteries? And how long is the connecting wire? If you are getting significant voltage drop that would significantly lower your charging amperage. In my build I am using a 2-0 positive wire to my four 6 volt GCB in a 12v bank but it's not yet operational. I hope to be able to get more than 38 amps. Of course with four batteries my battery internal resistance will be lower. Bill
 

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With LiFePO4 batteries and 2/0AWG cable running from the alternator, I get 170A charging current at idle (I have the 180A alternator). I have seen it go up to 175A while driving.
 

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With LiFePO4 batteries and 2/0AWG cable running from the alternator, I get 170A charging current at idle (I have the 180A alternator). I have seen it go up to 175A while driving.

Eeeee yow! Dat'sa lotta juice! Was the alternator glowing red hot? >:D

Ed
 

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Haha it surprised me too. I am happy that I can charge my batteries so quickly just by idling, but I am a little concerned that my alternator will crap out eventually. So far so good, but it has only been a few weeks.
 
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