Charging System Leakage Current

I'm asked fairly often if the battery should be disconnected when a bike will sit for a while or while the battery is being charged or trickle charged. I always answer that I remove the fuse. This is because with standard wiring there is a direct connection to the rectifier/regulator whether it is the OEM bridge rectifier/Zener, a PODtronics, a Tri-Spark MOSFET, or any other I know about. This means that there is a very slight risk of something going bad and since there's a power source, a fire starting. Also, the battery is continuously being discharged by the charging system. Today, I measured the leakage current with a fully charged AGM battery:

• A bike with the OEM system, 0.2ma - pretty much negligible
• A bike with a PODtronics POD-1-HP, 0.66ma - not a lot, but way more than the others tested
• The same bike as the POD-1-HP but with a Tri-Spark MOSFET unit - my needle didn't move on the 2.5ma range. On a 50 micro amp scale, it showed 5 micro amps - definitely negligible. Note: the Tri-Spark unit has a small capacitor across the output so you have to wait a few seconds for that to charge before the leakage current is accurate. BTW, AN lists the device as "with capacitor". That's very misleading - it is not the same as the PODtronics regulator that has a capacitor that is large enough to run the bike without a battery and it cannot replace the standard capacitor - info direct from Tri-Spark.

In all cases, the standard capacitor was disconnected and the ignition was off.

Note that when charging with the OEM system and with the fuse in, the charger is trying to raise the voltage and the Zener is capping it - probably true with PODtronics and I don't know about Tri-Spark. In most cases, probably hurts nothing, but since I use a cheap 55 year old charger that is capable of 10 amps, I never leave it alone and never use it with the fuse in.

I always disconnect the battery on any vehicle that I am storing for say, over the winter, whatever. I do not use a charger on an unattended vehicle - that is, a vehicle that is not in my garage. I have stored cars and motos for as long as 7 months with the batteries disconnected and, when re connected, they spin the starters as if they had been running yesterday. This includes standard flooded batts as well as Li (Shorai) batts. I have had two instances of batteries being destroyed by allegedly 'smart' chargers that ran amuck so I do not trust them if I can't routinely check.

As far as charging while connected, I have never worried about that as far as leakage current is concerned. I'm not disagreeing with your conclusion, I'm just saying that I don't consider the 'risk' to be "on my radar." Of course, my view might be different had I experienced a problem - as I have with unattended chargers!

As Greg points out, the regulator be that the zener or the aftermarket reg/rec is constantly connected - it’s not switched on and off at the ignition.

If you have a ‘smart’ charger that conditions and desulfates your battery, the regulator can cause havoc with this charge cycle, resulting in an incorrectly charged battery or damage to the charger.
That’s because the regulator starts shunting at around 12.75 volts.

Definitely best to disconnect the battery for charging, or remove the fuse.


It makes me smile, as the text in the Factory Workshop Manual describes the power socket as ‘Power Take-Off Socket’ and only discusses powering accessories.
However, the original wiring diagrams in the same Manual incorrectly describe it as ‘Power Charging Point or Power Point’ - clearly the wiring draftsman didn’t get the memo on that one!!!

marshg246 said:

• A bike with the OEM system, 0.2ma - pretty much negligible
• A bike with a PODtronics POD-1-HP, 0.66ma - not a lot, but way more than the others tested
• The same bike as the POD-1-HP but with a Tri-Spark MOSFET unit - my needle didn't move on the 2.5ma range. On a 50 micro amp scale, it showed 5 micro amps - definitely negligible. Note: the Tri-Spark unit has a small capacitor across the output so you have to wait a few seconds for that to charge before the leakage current is accurate. BTW, AN lists the device as "with capacitor". That's very misleading - it is not the same as the PODtronics regulator that has a capacitor that is large enough to run the bike without a battery and it cannot replace the standard capacitor - info direct from Tri-Spark.

Click to expand...

I'll add another data point to that tomorrow. I'm using a Shindengen FH020AA and Shorai battery. One of the claimed benefits of the LiFePO4 batteries is that they can go long periods without a charger if you're drawing no current. I take mine off the bike and keep it on the special Shorai battery tender over the winter, but I'll be curious to see how much leakage there is while installed on the bike.

gtiller said:

It makes me smile, as the text in the Factory Workshop Manual describes the power socket as ‘Power Take-Off Socket’ and only discusses powering accessories.
However, the original wiring diagrams in the same Manual incorrectly describe it as ‘Power Charging Point or Power Point’ - clearly the wiring draftsman didn’t get the memo on that one!!!

Click to expand...

When I wire a bike I generally leave that out unless it's a customer bike and they insist.

For a long time finding a plug to match was hard. AN now sells new plugs and sockets as a set but as with the originals, they are not polarized. When using standard wiring, that socket is directly connected to the battery through the fuse. Connecting a charger to it backward could be bad for the charger or bike. Connecting a device to it for power backward could be bad for the device. In either case, the fuse (hopefully) would blow - better have spares!

marshg246 said:

AN now sells new plugs and sockets as a set but as with the originals, they are not polarized.

Click to expand...

On my bike one pin is fatter than the other. My plug only goes in one way.

maylar said:

On my bike one pin is fatter than the other. My plug only goes in one way.

Click to expand...

Even so, you can still try to plug it in the wrong way and make contact.

I haven't actually bought the one AN sells so hopefully I'm not wrong about what they offer but they do have a clear picture and the OEM ones I've had go either way.

marshg246 said:

Even so, you can still try to plug it in the wrong way and make contact.

I haven't actually bought the one AN sells so hopefully I'm not wrong about what they offer but they do have a clear picture and the OEM ones I've had go either way.

Click to expand...

+1 Greg very easy to mess that up even if it’s just a quick touch.
I guess if you plug an electric razor in there wrong it will run backwards and put hair back on your face?
Pete