GPS current draw.

Just a quick question for anybody electrically minded out there.I have a Garmin Zumo 220 which is wired directly to the battery on my GSX1250FA.The unit is 5 volt and has a transformer built into the wiring.Will the wiring draw current from the battery even when the gps is not attached,because of the transformer? I think not,but a mate (ex electrician) says it will and I need to use a switched feed or I could get a flat battery.Thoughts?

Stromcat wrote:Just a quick question for anybody electrically minded out there.I have a Garmin Zumo 220 which is wired directly to the battery on my GSX1250FA.The unit is 5 volt and has a transformer built into the wiring.Will the wiring draw current from the battery even when the gps is not attached,because of the transformer? I think not,but a mate (ex electrician) says it will and I need to use a switched feed or I could get a flat battery.Thoughts?

I can't answer for the Garmin, but I have had a Tomtom Rider2 attached to my bike for 5 years. It to has a transformer built into the mount. Until recently it was wired direct to to the battery and I've never had a flat battery.

Sorry, I can't help you either, my Garmin plugs straight into a 12V power supply with no transformer

I'm no expert but I would doubt it very much if there was any leakage when it is unplugged. I have been told that the GPS"s do draw quite a bit so be sure to switch it off when you leave your bike.
I must say that I never thought that I would buy a GPS for a bike. But it definitely paid for itself on my recent trip. And it is fun to look back at the "history" of your rides. So much data.

These "transformers" are more than just the old primary and secondary windings, in the good brand name devices there is a fair bit of electronics that help stabilize the output 5v as well as reduce it down from 12v.  Actually I'd be surprised if there is even a transformer in the actual circuitry.  So even if there is no currect draw by the GPS, there are components that sit across the 12v if it is not switched off, these components will draw a minute amount of current that will eventually drain the battery, however the circuitry (in the brand name devices) is so good these days it could take a fair while for this to occur.  

However, if you have picked up a $5 special unit from fleabay or down at the markets, expect that to flatten your battery a lot sooner.

Getting to a switched source on the bike is realitive easy - just tap into your tail light circuit.  If you need a bit of heavier current than the tail light can supply, use a relay.  On some bikes with senative electronics you should use a relay that has a diode across the windings to stop the reverse voltage spike produced by the collapsing field windings, i,e, look for a relay with this symbol across 85 and 86:

That's good info Barry_mcki

I always get a little flummoxed by the diagrams - let me run my interpretation past you, see if my understanding is right.  

Please, correct me if I am wrong. 

Pin 30 - Power from the battery (Heavier Wire)

Pin 85 - Common earth 

Pin 87 - Relay switched power - to the appliance being powered (Heavier wire)

Pin 86 - Activating power - connects to a powered switch 

The circuit involving pins 85 and 86 is the low current circuit - this operates the relay 

The circuit involving 30 and 87 provides power to the appliance being powered when the above circuit is on.  

I need a cretin's guide, and I don't like figuring this out each time (maybe once every couple of years when I do this) If this is right, I'll file it away and keep it, along with your pic and diagram.

jstava wrote:That's good info Barry_mcki

I always get a little flummoxed by the diagrams - let me run my interpretation past you, see if my understanding is right.  

Please, correct me if I am wrong. 

Pin 30 - Power from the battery (Heavier Wire)

Pin 85 - Common earth 

Pin 87 - Relay switched power - to the appliance being powered (Heavier wire)

Pin 86 - Activating power - connects to a powered switch 

The circuit involving pins 85 and 86 is the low current circuit - this operates the relay 

The circuit involving 30 and 87 provides power to the appliance being powered when the above circuit is on.  

I need a cretin's guide, and I don't like figuring this out each time (maybe once every couple of years when I do this) If this is right, I'll file it away and keep it, along with your pic and diagram.

You are spot on

Also there are 2 main types of 5pin relays on the market. One has Pins 87 & 87a with this type the current is switched between the two ( one is on the other is off)
The other one will have 2 x 87 pins that work together, (both on with relay) these are good for twin aux lighting etc.

Check the diagram on the relay when buying

barry_mcki wrote:TActually I'd be surprised if there is even a transformer in the actual circuitry.

You are right, as I have had my dock apart there is no "traditional" transformer inside, just a very small circuit board.

Yep - thats a good summary JS.  Always use the heavier gauge wire on the 30/87 type contacts as this is what is feeding the load (lights, horn, gps etc), the heavier gauge and good terminals will mean less voltage drop - this is one of the reasons I believe our headlights have such a bad reputation (i.e. Suzuki don't follow this principle hence it is not unusualy to see a significant lower voltage at the bulb than expected).  

The current draw of the relay winding (85/86) is very low and even suzuki grade wire is good enough for that.

If using the diode protected relay that I mentioned earlier then pin 86 must be the positive lead for the relay winding.  The diode is usually reverse biased (i.e. turned off) when hooked up, it only comes into play when the main 12v is removed from the circuit and the energy stored in the windings (due to the collapsing magnetic field) produces a negative spike.  Instead of this spike being "released" into the rest of the bikes wiring, it is shorted by the now forward biased diode.  You'll probably find that if you try to install these type of relays with positive on 85 that it would not work.  Some manufactures use a resistor instead of the diode (in fact to be 100% accurate my initial drawing would be a resistor), however the same principle exists for the collapsing negative spike.



These would be the more common bases you'd come across, 85/86 is always the relay windings, 30 always the input heavy duty load source voltage, and 87/87a the relay-switched wire that goes to the load.  As there is no current direction devices in the 30/87/87a connectors there is no absolute way to wire positive, however rule of thumb has 30 normally being the lead off to the positive:

Thanks for all the replies.Looks like there are some real electronics wizards on this forum! So,if I read these replies correctly,although there will be some current draw even when my GPS is not attached to the charge wire,it will be so small as to not make much difference.A bit like the clock on the GSX1250 ? So providing the bike is run every few weeks I should be ok,longer than that put it on the Optimate?

Correct, just keep an eye on the voltage level of the battery if you are going to leave the bike for long periods.

A good trickle charger should have a "maintain" cycle so it doesn't over charge the battery. A few of us have different versions of the CTEK chargers and are pretty happy with them.

Just to build on the info Barry has provided and to tell of an relay experience I had yesterday.

A friend of mine acquired a BMW K100 1986 which was not running.

A few "experts" have had a look and all walked away.

The BMW K100 is an electronic minefield with a fuel injection control unit, an ignition control unit and lots of other goodies including several relays.

It is also fairly hard to get a test probe in to most parts of the circuitry.

Anyway, turn on the ignition key and the fuel pump runs.
Push start button and engine turns over but does not fire.
Removes spark plugs and confirmed spark.
Fuel present on injector fuel rail.

Located a fuel injector relay which was not operating when ignition key was turned on.
This 5 pin relay has pins 85 and 86 for the coil, pin 30 to the battery and pins 87 to feed the fuel injectors and 87b to feed the fuel pump.

I ultimately discovered that the BMW K100 uses a Type A relay and not a Type B relay which we are all familiar with. I have been playing with this stuff for decades and did not know there were two different types.

Here is a diagram of the two types



The conclusion is that the previous owner had swapped from a type A relay to a type B relay not realising the differences.
Also, the correct relay has pins 87 and 87b which are both make contacts. The replacement relay had pins 87 and 87a which is a changeover type.

Thanks Bandit Dave.

There must be an interesting, probably historical reason, for the pin numbering in relays.

Looks like it was formalised as a DIN stadard (DIN 72552) in 1971 with an update in July 2014 (DIN 72552-2 2014-07).  For the cheap price of $139 you can get a copy of the 14 pages from SAI Global or for the majority of the terminal codes look at this reference.

This standard is almost obsolete with the advent of computer controlled processors, CAN-BUS and multipin connectors, a lot of manufacturers now have their own alpha-numeric code, but you will still see it used especially with relays.

Here is the source of information from my previous post.

http://www.12voltplanet.co.uk/relay-guide.html

There is a tab in the top menu "knowledge centre" which I found quite useful