Do Not Connect Battery Charger Directly to Battery ?!?

My new to me F700GS came with an sae 12V plug attached directly to the battery, for connecting to a trickle charger that was also included. Great!

Or not?

Reading through the owner’s manual, it clearly states to only attach a trickle charger via the on board 12V Hella style plug in the dash. It says NOT to connect a charger directly to the battery, due to risk of possible electrical damage.

I am a believer in following the owners manual, barring convincing evidence to the contrary. What is the collective wisdom on this topic?

I have connected directly to the battery on 26 different BMWs which we have owned over the years. On Oilhead motorcycles BMW even provided a convenient post/lug connected directly to the starter hot lead for the purpose of either charging or jump starting. If BMW is now constructing the electronics on the F700 so fragile that connecting to the battery would be a worry I would run from the model and brand as fast as I can.

I am sure there is some disaster scenario where applying improper voltage, or creating some type of short circuit might damage something. That said, I believe that in applying a 12v (nominal) charger to a 12v battery, for most people the human brain is as good as some shutoff gizmo BMW has installed.

However, if you have a charger with the correct DIN plug, then there is really no downside to doing it their way even if it is a crock of male bovine excrement.

vark said:

My new to me F700GS came with an sae 12V plug attached directly to the battery, for connecting to a trickle charger that was also included. Great!

Or not?

Reading through the owner’s manual, it clearly states to only attach a trickle charger via the on board 12V Hella style plug in the dash. It says NOT to connect a charger directly to the battery, due to risk of possible electrical damage.

I am a believer in following the owners manual, barring convincing evidence to the contrary. What is the collective wisdom on this topic?

Click to expand...

That increases sales of that Hella plug!

My guess is that particular instruction is to-
1) Keep non-factory wiring from being installed on the bike..... possibly causing a warranty issue.
2) Easier for BMW to explain that when using a battery tender, make sure connections are good, solid and correct.
OM

Actually BMW'S caution has to do with the advent of "smart" chargers that have a desulphation mode. If the charger decides the battery is sulphated it tries to recondion it by hitting it with a series of high voltage pulses. Herein lies the risk to the bike's electronics. Any modern BMW would have such electronics. Out of an abundance of caution BMW tells you to remove the battery from the bike to charge it with other than its charger. BMW cannot rely on bike owners to make such distinctions. Most riders these days are "appliance riders".

That being said the likelihood of damage may be low but the safe thing to do is either don't use a charger that has a desulphation mode or disable desulphation. I charge through Powerlet receptacles wired direct to the battery with desulphation disabled.

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PGlaves said:

.... If BMW is now constructing the electronics on the F700 so fragile that connecting to the battery would be a worry I would run from the model and brand as fast as I can...

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What does the Owner’s manual for your pair of G310GS bikes say on this subject?

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RadioFlyer said:

Actually BMW'S caution has to do with the advent of "smart" chargers that have a desulphation mode. If the charger decides the battery is sulphated it tries to recondion it by hitting it with a series of high voltage pulses. Herein lies the risk to the bike's electronics. Any modern BMW would have such electronics. Out of an abundance of caution BMW tells you to remove the battery from the bike to charge it with other than its charger. BMW cannot rely on bike owners to make such distinctions. Most riders these days are "appliance riders".

That being said the likelihood of damage may be low but the safe thing to do is either don't use a charger that has a desulphation mode or disable desulphation. I charge through Powerlet receptacles wired direct to the battery with desulphation disabled.

Click to expand...

That’s what my manual says to do, i.e. remove battery from bike when connecting chargers directly to it. But that would be a major hassle for anyone just wanting to trickle charge.

Near as I can tell this bike has been hard-wire trickle charged for a long time, and may even have come pre-wired that way from the dealership.

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vark said:

Near as I can tell this bike has been hard-wire trickle charged for a long time, and may even have come pre-wired that way from the dealership.

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My 2015 RT had an SAE plug installed by the BMW dealer from which I bought the bike. The dealer used it when it was in their demo inventory, and I've been using it ever since. Whenever I'm not on a trip, or riding locally it's connected to an Optimate-4 via the SAE plug.

ExGMan said:

My 2015 RT had an SAE plug installed by the BMW dealer from which I bought the bike. The dealer used it when it was in their demo inventory, and I've been using it ever since. Whenever I'm not on a trip, or riding locally it's connected to an Optimate-4 via the SAE plug.

Click to expand...

I’m also curious, what does the owner’s manual for your 2015RT say on this subject?

Interesting discussion. Following

At least my last five BMW models have come from three different dealers and they've all come with pigtail already attached by dealer. If prior one haven't I've added it. Never a problem. VARK, if you go to BMW's site, you can review just about every owners manual.

https://www.bmw-motorrad.com/en/service/manuals/rider-manual.html

I've had a pigtail on every bike I've owned, regardless of brand. Never an issue.

RadioFlyer's explanation seems the most plausible. It's probably a BMW CYA.

But, if you use the wrong charger and fry something, you have been warned. Like he said, all chargers are not alike. Should not be a problem with basic chargers or BatteryTenders.

I've used a BatteryTender float charger on my wife's F700GS, through a SAE pigtail direct to the battery, for 6 years now (she doesn't ride much any more).

The BEST charger is frequent long rides!

vark said:

I’m also curious, what does the owner’s manual for your 2015RT say on this subject?

Click to expand...

Here is what the manual for my RT says:

Battery
Maintenance instructions
Correct battery maintenance
combined with proper charging
and storage procedures extends
the battery's service life, and is
also required for warranty claims.
Compliance with the points below
is important in order to maximize
battery life:

Keep the surface of the battery
clean and dry
Do not open the battery
Do not top up with water
Be sure to read and comply
with the instructions for charging
the battery on the following
pages
Do not turn the battery upside
down.
If the battery is not disconnected,
the onboard electronics
(clock etc.) will drain the
battery. This can cause the battery
to run flat. If this happens,
warranty claims will not be accepted.
During driving breaks of more
than 4 weeks, a trickle-charger
should be connected to the
battery.

BMW Motorrad has developed
a trickle-charger specially
designed for compatibility
with the electronics of your motorcycle.
Using this charger, you
can keep the battery charged
during long periods when the
motorcycle is not being used
without having to disconnect the
battery from the motorcycle's
onboard systems. Additional information
is available at your authorized
BMW Motorrad retailer.

Charge connected battery

Charging the connected
battery directly at the battery
terminals can damage the
motorcycle electronics.
To charge the battery via the
battery terminals, disconnect the
battery first.
If the multifunction display
and indicator lamps fail to
light up when you switch on the
ignition, the battery is completely
discharged (battery voltage below
9 V). Attempts to recharge
a completely discharged battery
through the onboard power
socket can damage the motorcycle's
electronic systems.

Always charge a completely
drained battery directly at the
terminals of the disconnected
battery.

Charging the battery via
the onboard socket is only
possible with suitable chargers.
Unsuitable chargers can result in
damage to the motorcycle electronics.
Use suitable BMW chargers.
The correct charger is available
through your authorized
BMW Motorrad retailer.

Charge disconnected battery
via onboard socket.

The motorcycle's onboard
electronics know when the
battery is fully charged. The
onboard socket is switched off
when this happens.
Comply with operating instructions
of charger.
If you are unable to
charge the battery via
the onboard socket, you
may be using a charger that
is not compatible with your
motorcycle's electronics. In
this case, charge the battery
directly at the terminals of the
disconnected battery.


Here is what my dealer said: "Attach the battery maintainer to the SAE plug when you're not riding."

My experience: Two RTs, a 2008 and a 2015...total riding 10 years, about 100K miles both with batteries maintained by Optimate-4s. No problems with batteries or bike electronics.

vark said:

What does the Owner’s manual for your pair of G310GS bikes say on this subject?

.

Click to expand...

It just says disconnect the battery before charging. It doesn't have any special electronic port. So did the manual for my K75 in 1986. BMW has said this for a very long time with absolutely no explanation as to why. They have also urged owners to buy their very own super duper BMW Roundel emblazoned chargers too, ever since they installed Gel batteries in Oilheads. Those old originals are going for north of $150 now on ebay.

The caution about de-sulfating chargers is excellent advice. Wouldn't it be nice if instead of telling me I should remove the fuel tank to access and disconnect the battery to auto maintain the battery on my R1150R (it doesn't have a whizbang electronic body guard either) they just in big bold letters said Do not use a de-sulphating charger if the battery is installed in the bike.

When it comes to technical things I admire honest explanations and not chicanery. Others, I am sure, don't care, but I do.

ExGMan said:

Here is what the manual for my RT says:....


Here is what my dealer said: "Attach the battery maintainer to the SAE plug when you're not riding."

My experience: Two RTs, a 2008 and a 2015...total riding 10 years, about 100K miles both with batteries maintained by Optimate-4s. No problems with batteries or bike electronics.

Click to expand...

Thanks for the info. So your manual essentially says same as mine - - do not hook charger directly to battery unless battery is "disconnected" from bike.

I wouldn't be surprised if pretty much all relatively recent BMW owners manuals have same language.

I am just going to keep using the sae plug and the trickle charger.

Thanks everybody.

ExGMan said:

Here is what the manual for my RT says:

.
.
.
Charge disconnected battery
via onboard socket.
.
.
.

Click to expand...

You'll be waiting a long time for that charging cycle to complete.

lkraus said:

You'll be waiting a long time for that charging cycle to complete.

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"Disconnected battery". Maybe they mean frame ground disconnected? That's the way I charge my /7 battery.

Ride more. Worry less.

om

20774 said:

"Disconnected battery". Maybe they mean frame ground disconnected? That's the way I charge my /7 battery.

Click to expand...

If only, but not on an Oilhead, for example. The battery negative cable connects to the engine case beneath the battery box which holds the battery as well as the ABS module on several models.

Which brings to mind a story. We were at the Nebraska Rally a number of years ago. There was a rider there with a fairly new R1100GS. The electrical system was "flakey" (tech term). After a couple of hours of troubleshooting I concluded the bike had a bad ground connection. Not wishing to dig all the way under the battery box, he borrowed a bike and headed off to the nearest auto parts store and returned with a three foot or so long automotive battery cable with ring terminals on both ends. We disconnected the factory ground wire at the battery and substituted the new cable attached to a convenient fastener on the engine case or frame, I forget which. That solved the ground issue and the bike performed fine.

I ran into the same rider a couple of years later. He was still riding that R1100GS and it still had the substitute ground cable. He hadn't "gotten around" to digging beneath the battery box to fix the OEM ground issue.