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Changing the Watchdog Autostart Voltage
Where is Jack Finch(jack14r) when you need him? On 10/31/16 he contributed to a thread here by posting
“I figured out a way to change the auto start voltage on the watchdog,You can use a 15K resistor between the voltage sensing point and it will start around 24.2 volts.I actually made up resistors between 10.5K-15.5K and tried them and wound up using something around 15K,it worked very well.”
I assume he knows what he’s talking about? I haven’t tried it yet?
Here’s the link to the original thread
http://prevostcommunity.com/forum/threaddetails.asp?Category=General Discussions&ThreadID=6097
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7 Replies
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Jack definitely knows what he is talking about. If I recall as part of the process he investigated and found the Watchdog does not keep the generator running until the batteries are in float, but uses timing to shut it down. That was a significant piece of knowledge because by putting the resistor in the “sense” line to the Watchdog he found it starts the generator at a higher battery voltage which increases battery life, but has no impact on shut down.
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I think this is a modification that anyone with a Watchdog who does any amount of dry camping and relies on the Watchdog to fire up the generator would be interested in.
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Jon,
Mine went into float , However the Gen run time is set to 6.5 Hrs on mine. I have been told The Low Voltage start is 11.1 ( But at least it works ) I do not plan on doing a lot of Dry-Camping. How often do You get in a situation where You do not need The creature comforts of A/C ? Mine will not run off of the inverters. If I boondocks , I will be running the Gen. What I do value about the Autostart is being able to shut everything off except the Fridge. And keep My Groceries and Goodies cold should I be away from the coach for several hours.
The scenario that Don is talking about must be a Lady / 24V Coach ? -
My operating procedures are simple.
If I am not plugged into 50 amp shore power when I am done driving or dry camping I start my generator. Then I put every switch in the 120V panel on so the generator can run anything we want to use, including keeping the batteries topped of if we use the 24V stuff like lights.
It doesn’t matter if I need to run the ACs or not. But if I do run them I NEVER will run them through the inverters.That holds true even if I am driving. I have a generator and if I need AC and I am not on shore power I am running the OTR or the ACs on generator power.
If I cannot run the generator all night such as with quiet hour I will turn it off, and restart it when allowed.
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GoneCrazy wrote: “The scenario that Don is talking about must be a Lady / 24V Coach ?”
divide by 2 for a 12v coach
It’s on my list of things to do because it’s the right thing to do
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This is real simple to do,just open the electrical box that is near the watchdog and using a volt meter find the wire that is exactly the same as the house batteries,I then put the system on auto start and un plugged the wire and if you have the right one it will auto start the gen.I used a open fuse holder that holds the small glass style fuse to solder different resistor values to the fuses that I made up(obviously the fuses must be blown),then I wired the fuse holder inline and could snap in various values to achieve the start voltage that I wanted.If you want to go back to the Watch Dog setting just pull the fuse with the resistors and insert a normal fuse.
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Jack is correct and I know what he means but the wire is a very small gauge wire, not a large one because all it does is allow the watchdog to “read” the exact same voltages as the batteries.
I am going by memory so take this as possibly misleading. My sense wire when looking at the bulkhead wall with the circuit breakers and fuses in the second bay was to the right of the main buss bars and had an inline fuse. I almost think the wire was a 22 or even 20 Ga so it will be small. Mine was black, but on my present coach I believe it is a brown color. Do not go by color.
As to voltages, keep in mind the voltages seen by the watchdog are with the batteries loaded. By that I mean they are not the resting state voltages but they have the loads of house devices so the actual resting voltage when the generator start is initiated my be 12 volts of more. The values battery manufacturers define as percent of charge are resting voltages so like Jack did, you may want to experiment to set your own percent of discharge value. Too much resistance and you will have frequent generator start cycles. Your phantom loads and those experienced by Jack may be different so there might be some experimentation required based on your particular coach.
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