Using a battery tender - disconnect battery first?

 I've been using a battery tender on my 2015 WR250F for about six months now. I have a pigtail wired into the main battery so I can quickly and easily plug it in when I'm done riding.   Was chatting with a buddy about using a battery tender and he said he had read many times that you should disconnect your battery from the rest of the bike before using a battery tender (specifically just the negative cable).  "They" say  to do this to protect the ECU and other expensive electrical components should the battery tender malfunction or short out and damage them.  

 I had never heard this and have never had a problem with simply plugging in the battery tender. But if it's best practice to disconnect the battery to protect the bike, I will. 

What say you, experts?

I'm not an expert but I've used trickle chargers on cars and bikes since the 1980's and have never heard of this nor had a problem.

My 09 wr250f has a switch that kills all power does your 15?.  I use one on my ktm for years and never a problem. 

My 2015 does not have a 'master switch' like that. I get the feeling the people that suggest this are running fuel injected / computer controlled bikes.

read the charger manual but i never unwire terminals when charging.

No need to disconnect when on a tender. The only time you want to disconnect and remove a battery is when it is a large battery (car/truck) and you are 'fast charging' it. Not a situation with a bike battery.

Some modern computer controlled autos have voltage/current sensors in the battery terminals and it can 'confuse' the computer if the voltage is high (over 13V) at the battery as the battery voltage is expected to be less. To get around this you charge these in place by connecting to the terminal that the alternator feeds. But again, a non-issue on a bike.

I have to disconnect the battery on my '16 KTM 4-stroke.  If you don't the fuel pump cycles about every minute which is a very well known issue.  That was with the stock ECU.  Last fall I bought a Vortex ECU and the manual explicitly says to disconnect the battery or risk damaging the ECU.  I think that comes down to Vortex not being able to guarantee that every charger ever made won't push a damaging voltage.

I've seen several chargers put out 16.5+ volts.  Depending on the charger's design it might spike even higher.   Depending on the bike's design certain components will see that voltage.  So it probably all depends on the charger and the bike.  

If you've already been doing it for some time and have had no issues, I'd be confident that your bike and your charger are OK to continue doing it.  If I just bought a new expensive fuel injected bike and was using an off brand charger I'd probably disconnect the battery.

Doc

Edited by Doc_d

I have had many things on tenders for years without messing with disconnection the batteries. No problems.

2014 690 Enduro R

2 2008 KLX450Rs

1993 XR650L

1991 Chevy Pickup

1951 Farmall C

1947 Farmall H

 

The one thing I did do wrong one time was started the bike with the tender connected. The little series 1amp fuse in the tender pigtail blew.

Thank you all for the help and insight on this. As I haven't had any issues, I'll probably not worry about it (and I am using a 'name brand' battery tender).
The folks suggesting to disconnect the battery are of the orange variety - KTM riders. Maybe that explains some things if it's a known issue for those bikes.

I've been hooking the battery tender (mines a battery tender junior) up to my 2013 wr250r without disconnecting the battery from the bike for 5 years now.

I also start the bike every couple of weeks without unhooking the battery tender without issue, I wouldn't worry about doing this on a Yamaha, other bikes maybe different.

Never have done this and never will. Solution looking for a problem IMHO. I'm of the Orange variety. ;)

KTM+Super+Fan+a.JPG

You can screw up the speedo if you run the bike without a battery. 

My WR now tops out at 140mph.  

47 minutes ago, Bryan Bosch said:

Never have done this and never will. Solution looking for a problem IMHO. I'm of the Orange variety. ;)

 

Bryan - what KTMs do you have?  You don't have the issue where the fuel pump runs if you don't disconnect the battery?  It doesn't run constantly it turns on the  off every minute or so.

Doc

Just now, Doc_d said:

Bryan - what KTMs do you have?  You don't have the issue where the fuel pump runs if you don't disconnect the battery?  It doesn't run constantly it turns on the  off every minute or so.

Doc

KTM 690 Enduro R. Not that I've noticed. But, I also have a key switch.

The ECU is a potential issue, probably with misbehaving chargers that output too much voltage or have a lot of electrical noise.

I store several vehicles for 6 months at a time, all with ECUs,  and use trickle chargers and have never had a problem.
One solution is to use a LiFe battery because they don't self discharge like lead acid batteries so you don't need a trickle charger. I put Shorai Li battery in my CRF250X and it starts right up after being in storage for six months wo a trickle charger.

People that live by the equator(ie Florida) might not need a tender,  but when you live where temperatures get real cold, putting tenders on the things that don't get run very often will extend battery life. Deep cycle a lead-acid battery a couple times and it is shot.

I think of trickle chargers as a different animal than a tender, but some may use the terms interchangeably. I see the tender as a battery monitor that only charges when needed, it may be connect 6 months and never charge once..  I think of a trickle charger as always charging.

 

34 minutes ago, Chuck. said:

.. I put Shorai Li battery in my CRF250X and it starts right up after being in storage for six months wo a trickle charger.

I have a Shorai in one bike and it seems to struggle when it is below freezing. (I ride all winter). The Shorai battery management system has an awesome monitor built in that inspects the voltage over all 4 cells and balances them. I keep mine on the shorai tender all winter in the "store" mode.

The folks suggesting to disconnect the battery are of the orange variety - KTM riders. Maybe that explains some things if it's a known issue for those bikes.

The Sherco Riders forum has a small handful of damaged regulator stories that some link to trickle chargers and/or tenders. Clay, the importer, warns against using them. The Sherco has a 220 watt system, so he wonders why folks would use it, but he lives in the warm climes of Tennessee. ;)

He advises not to let the battery sit on a tender  Instead, charge it the night before a ride. If long-term and/or winter storage is the need, remove the battery and take it inside and snuggle with it as you dream of Spring.

 

I use a “Battery Tender” on my 15 KTM 450 SXF, no problems, no fuel pump running issues.

I use it on Mama’s Yamaha TTR 230, no problems. 

I use it on my 13 Polaris RZR 1000, no problems. 

I use it on my 15 HD FLTRXS, no problems.

I use it on my 64 John Deere 650 tractor, no problems.

I don’t disconnect the negative from the terminals. Don’t stress on it Dude 😀

No stress here, just making sure I'm not overlooking something simple that "everyone knows you should do XYZ when ABC".
Seems there's some truth to the consideration of this with some bikes but no known issues with Yamaha's. I'll still continue to use the tender but perhaps on a less frequent basis.
I appreciate all the responses thus far.

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