Updated Does it matter where the switched power comes from on a relay? PICS

[canuguzzi]

I have an isolated battery (isolated from the main) and it can provide accessory power (accessories not part of the main system). I want to have that isolated battery power switched on/off when the bike is running.

I'd like to use the hot from the system GPS since it is on-off with the ignition. Does it matter that the isolated battery is not effectively part of the mains on the bike, in other words, the relay uses the GPS wire as the switch interrupter for the relay but the power through the relay is from the isolated battery?

I had though of using an auto shut off instead since sometimes it is a benefit to power the accessories even with the ignition off and even if the isolated battery went dead, it can't affect the mains.

[canuguzzi]

Solved. Decided to go with a low voltage disconnect since the benefits of having the accessories run with the engine off outweigh switching them off with the engine not running.

The low voltage disconnect will work on the isolated battery and let the tablet, extra light and other things run, then if the isolated battery gets to 11.9 volts, power shuts off after 5 minutes. Since the battery is isolated, it can't affect the primary battery used to operate the bike.

Best of all worlds and I can simply put a manual switch up front to turn off accessory power independent of the voltage.

[rodekyll]

Do you have a solution for recharging the aux battery?

[canuguzzi]

Yes, the battery isolator takes care of the charging for the 2nd battery. When the primary battery is charged, then the isolator detects that and charges the 2nd battery.

If the charge on the primary battery goes below a certain threshold, the charging on the 2nd battery stops until the primary is again where it should be. The isolator doesn't take all of the charging but only a percentage so there is always something going to the primary, not a simple on-off thing.

Each battery discharges independent of one another and neither can affect the other. Say the primary battery fails for some reason, left ignition on for example. You just press a switch and the isolated battery and primary turn into a parallel system and you just start the bike.

The two batteries need not be the same capacity, just the same voltage.

You could for example, put one of those small lithium high capacity batteries in the back under the seat (like the tail compartment) and connect it via the isolator. It sits there and has USB power out to say run your phone or whatever. If the main battery ever goes to low to start the bike, a simple switch press and you are good to go.

I am using another AGM motorcycle battery (14 AH job) in the tail trunk. A heavy gauge SAE connector lets me disconnect the entire affair if I take the trunk off but in that trunk is a complete 12 power system so it can go inside a tent to run just about anything I need.

A solar charge controller lets me charge that battery so during camping I don't have to worry about keeping that battery charged.

This same type of setup is used in nearly all motorhomes so it's a proven way of doing it. The key is the isolator because it protects the bikes factory wiring and battery system.

This brings up something I might add to the main system which is the low voltage disconnect. Nice to have something to completely disconnect power if the batteries go bonkers. We've seen this happen enough time on this forum to know it isn't rare. A battery disconnect with a manual override makes sure that if you are a ways from home, going into a place to eat or a night in the hotel doesn't turn into a dead battery afterwards. While the battery might not be reliable, at least you'll get started and to the next place to get a new one.

[Kiwi_Roy]

To answer your first question, No, a relay doesn't care if the contacts are fed from the same source or Voltage for that mater "It relays a message from one system to another", I use lots of relays to control mains Voltage systems from low voltage DC.

The battery isolators you often see in motorhomes are nothing more than a pair of diodes they will let the current flow from alternator to the vehicle battery and the house battery but not between the two.

[rodekyll]

Good solution and good explanation.   

+1 on the power source thing.  I run a 12vdc process controller on my powder coating oven that switches the 220vac heater coils.  My boat uses the battery power to tell the 110vac shore power charger to work.

[fotoguzzi]

I love your idea! specially going into the tent with plenty of 12v to power a light and laptop etc..

can you list the parts and a diagram of how to do it?

[canuguzzi]

I love your idea! specially going into the tent with plenty of 12v to power a light and laptop etc..

can you list the parts and a diagram of how to do it?

Absolutely yes.  I am doing the smoke test tomorrow in the AM. My final smoke test is tomorrow. Then I'll document the entire setup with a wiring diagram and parts list.

I have both a spare AGM motorcycle battery and one of those 10,000 mAh lithium batteries, the kind they sell to start cars or run mobile phones and such. I still need to make up the last SAE connectors for the portable battery and then all is good to go.

The lithium is nice because it comes with a charger for it so it can accept the charge from the Norge's system via the isolator and I don't have to worry about if it is compatible or not. That part is especially nice because it can fit on the bike without any extra luggage to hold it. It goes neatly in that small space under the seat. Even so, it has more than enough power to run things like a laptop/tablet, LED driving lights, GPS/MP3 player.

Since I dislike drilling into things, I made it completely removable from the bike and it goes to original factory since nothing is permanently attached.

I'll post the complete diagram, pictures and the parts list with sources tomorrow (Saturday here) but it might be later in the day.

[canuguzzi]

Thanks Kiwi Roy, that does help because I realized that when I don't take the tail trunk along, having the relay gives added flexibility.

[canuguzzi]

Here is the wiring schematic and parts list for installing an aux  battery isolator, low voltage disconnect along with some notes.

Please, if you are unsure of working with this stuff, don't do it. While it isn't hard to do, a mistake on your part isn't my problem, you have been warned.

That said, it works and works very well. The isolator has a function to run both batteries in parallel should your main battery go dead and thus you can start your bike. For a camping environment, this setup will let you run many accessories including lights, charge phones, a small inverter (I use a max 180 watt job for AC) and things like that. You can also connect a small solar panel to charge the aux battery if you're camping for a while.

The isolator is microprocessor controlled and has some nice features.

The aux battery can be any capacity so long as it is 12 volts. It only charges after the main battery is charged so you don't have to worry that as you go down the road that your main battery isn't being charged.

As with all such things, some common sense goes a long way. This is not some industrial type extra battery solution but something sized small to fit easily into a tail trunk on the Norge or even in the tail space depending on the size of the aux battery you use. To power a tablet for GPS, charge your phone and run a very powerful 950 lumen driving lamp you need only a small 12 volt battery. You can use an AGM, flooded or Lithium. If you use a lithium, make sure that it is compatible with the bikes charging system or comes with its own that then goes after the isolator. BEWARE, if you use another charger as with a lithium, then you can't use the reverse parallel switch to start your bike if the main is dead unless you first remove the lithium charger from the circuit. I recommend you use an AGM 12 volt battery and then you get all the benefits without any hassles or compatibility problems.

I have things set up so that I can completely remove the aux battery system and then plug the LVD into the main in case I ride sans tail trunk or side bags. SAE connectors make this really easy.

The solar panel I use is one of those square types, not the small rectangular ones. It fits in the tail trunk nicely and while it isn't going to charge a dead battery, it can easily keep up with demands for camping and things like that. It comes with a 12' power connector (also SAE) so I can put it where the sun shines while the bike is in the shade.

If you don't happen to think all this is necessary, no worries, it just works for me and might for others.

The total parts come to about $150.