Battery Isolator Questions

[stovall]

I'm prepping for the summer & plan to do a LOT of riding on my 1990 GL1500SE. I want to put a spare battery in my trailer to have for LED lighting & USB power when we camp. I know there are isolators on Amazon, but which kind do I need? Do I need to match the size if the isolator to the amperage of the battery, or does it just control the charging aspect of the battery? I'm sure this is not a new idea, as most things have been tried at least once, especially on the 1500's! I appreciate any help you guru's have to offer. I also want to thank everyone on the site for the excellent articles & advice! It is such a comfort to know that anything I have questions about can generally be answered here on the site! I also want to wish everyone a Merry Christmas & a happy New Year!!! May the coming year find you all in excellent health (and wealth...we can all wish anyways), & enjoyable, safe riding!


Keep the shiny side up!!!!
Brian

[AZgl1800]

No need to spend bucks for an isolator:

I would run a separate lead from the bike's battery, through a fuse that goes to a new relay you install.
run a new wire to the trailer hitch area, and use a 2-wire rubber connector like used for Trailer Lights, so that you can pull it apart when the trailer is not connected.

the coil of the new relay should be connected to the Accessory Terminal on the fuse block.

This wire should be 12 gauge, not a dinky little 16 gauge, or even 14 gauge.

The battery in the trailer will probably charge up to within about 0.25 volts of what the bike's battery is.

but, be aware, that just short runs will not recharge the extra battery if it is pulled down to 12 volts or less.
It takes a long time, to get a battery up to full charge.

The Alternator needs to be putting out around 14.3 volts for a long time....
you will need to have a Voltmeter installed on the bike's dash somewhere so you can monitor the situation.

Also, if the 1500 has the OEM alternator, you cannot have any extra lights added, it won't handle the load.

I would suggest installing a Toggle switch to turn off the bike's running lights, and if that is not sufficient, then also install a Toggle switch to turn off the Headlights....

Compufire makes an alternator that puts out around 80-90 amps at 3,000 RPM which would be a great help

I would also suggest a Solar Charger panel that can put out at least 100 watts, 200 watts would be better, especially if you like to camp w/o riding the bike and charging the trailer battery

[Rambozo]

Just a diode rated at the max charging current will do the job to charge your aux battery while keeping the bike from using it. You could also just use a properly sized wire as long as you disconnect it from the bike while running your camp, so you don't drain the bike battery. A true isolated system would require you to make changes to the bikes wiring, as the isolator needs to go in the line from the alternator then out to each battery.

[DenverWinger]

+1 on John's relay approach, -1 on the Diode. There's going to be a 0.7 to 1.0 volt voltage drop across a diode that can handle 10-20 amps, and this plus 20 feet of additional wire going to the trailer battery will reduce charging voltage on the aux battery by that amount.

I've carried an aux battery camping with the 1100 (before I had the 1500), it was just a big lawn tractor battery and carried it in the saddlebag of the bike, tied in directly to bike battery thru a fuse and 14 ga wire. The 14 ga wire was thin enough that starting the bike didn't draw much power from the aux battery in the saddlebag, but plenty big enough to pass charging current. Of course, when we set up camp we took the aux battery out of the saddlebag and put it under the camper, so not draining bike battery. The 1100 did a fine job of charging the aux battery going down the highway!

Now I have a much bigger aux battery (120 Ah deep cycle) so it would have to go in the trailer, haven't set up the relay and wiring for it yet as so far everywhere we've gone camping on the 1500 has had 120v available.

Doesn't matter if bike pulls a little current from the aux battery while starting the bike, it will be quickly replenished once the engine is running.

[WingAdmin]

I used a simple cheap solar charge controller like this one:

https://www.amazon.com/SUNYIMA-Controll ... ref=sr_1_4

Instead of a solar panel, I ran the bike's main power into it, and the output of the controller went into the battery in the trailer. That way it only drew power when the bike was running, and when the trailer battery was full, the charge controller would stop sending power to it.

Simple and cheap, and it worked perfectly.

[Solo So Long]

A battery isolator is just a couple of diodes in a heat sink. A diode keeps current from flowing the wrong way, while connecting the two batteries in parallel. This lets you drain one battery without also draining the second one.

I would put a switch on the trailer to cut off the positive lead to the connector when you're using the aux battery without the bike running, but that's all that I would bother with.

[AZgl1800]

the PROBLEM with diodes, is the Voltage Drop across the Junction.

depending on the substrate,

A Germanium Diode has a voltage drop of approximately 0.3V across its leads.
This might not concern you to much if you aren't aware that a battery will never get to full charge with a Diode isolator.

A Silicon Diode will have a voltage drop of approximately 0.7V across its leads.

this is infinitely worse...

Best to use a Relay that is switched with the Key, e.g., from the Accessory Terminal on the fuse block.

[Rambozo]

A typical Schottky diode has a voltage drop around .3 volt. Not enough to worry about if your charging system is within spec 13.8 - 14.2 volts. I mentioned it just as an option. For what he is doing I would just couple the batteries together with wires when riding, then disconnect when setting up camp.

[LAB3]

I'm using a jump start box as my camp power supply. It'll charge off a wall plug or via the 12v outlet and has two built in 5v USB outlets on it, this gives me 5v, 12v and the ability to jump start the bike if needed. For the price, it's a no brainer.