Disconnecting the battery. ..what (if anything ) will it affect?

[alhendo1 3,062]

Evenings folks. Scenario....I want to hook up my Ctek battery conditioner to the bikes terminals so I can just plug it straight in....as per the title...what would be affected disconnecting the battery for a few minutes to screw the terminals home....would this affect the immobiliser? (never had a bike with one before)...sorry if this topic has been covered before. Thanks in advance. Alan.

[pjm 6,041]

Just make sure you remove the earth first, carefully isolate it and make sure it does not touch anything until you have the positive fitted and then refit the earth. You will then simply have to reset the clock. Not a big deal.

[trisaki 2,029]

When you  undo the bolt leave  the battery  terminal on the battery spare finger pressed against it then  put charger lead in situ and do up bolt repeat tother side

[wendeg 95]

So, it s not as simple as a carb fuelled bike?

[pjm 6,041]

I must confess to doing that on my Integra but If giving advice I thought give the correct way and not the slightly risky cheat. Albeit the cheat does work.

[Tonyj 6,907]

That's what I did , easy really

[pjm 6,041]

What difference to a carb fuelled bike? The basics of removing battery terminals are the same on anything from a moped to a Bentley.

[alhendo1 3,062]

Thanks for the quick replies folks. Appreciated. 

[alhendo1 3,062]

Job done. Thanks again.

[SteveThackery 3,090]

2 hours ago, pjm said:

What difference to a carb fuelled bike? The basics of removing battery terminals are the same on anything from a moped to a Bentley.

 

Well, the "theory" goes that FI bikes have an electronic control unit (ECU), which could be susceptible to mysterious voltage or current spikes if you get it wrong.

 

The theory is wrong, though.  Removing or replacing the leads can't harm the ECU no matter which way you do it (unless you connect them reversed, of course).  Neither can accidentally shorting the battery leads.  If anyone wishes to challenge that, they are welcome to come and mess about disconnecting and reconnecting the leads on any or all of my three bikes.  If they succeed in blowing up an ECU I will cover the cost myself and issue public mea culpas.

 

The only thing that might harm the ECU is connecting one of those smart desulphating chargers, which send current spikes into a flat battery to break down the sulphation.  It is definitely feasible for those spikes to damage an ECU, and when using one of those you really should disconnect one of the battery leads.

 

Here's a little test: who knows why you should disconnect the earth lead from the battery first?

[Callisidrin 447]

 

1 hour ago, SteveThackery said:

 

Here's a little test: who knows why you should disconnect the earth lead from the battery first?

 

If you disconnect the positive first and slip there is a possibility of the tool you happen to be using touching the chassis while still touching the positive producing a dead short, not a good idea, so always remove the negative first.

Also, it is not unknown to get sparks when disconnecting or connecting leads (more common when attaching jump leads), by disconnecting the negative terminal first you have the whole chassis for this to dissipate through so are less likely to damage things like the ECU, which doesn't like arcing, do the positive terminal and you.re more likely to cause damage if ithis does occur.

some vehicles actually used positive to chassis, had a car once that was wired like that, so in that case the opposite is applicable.

[Graham NZ 1,186]

And the negative must be re-fitted after the positive.

[wendeg 95]

5 hours ago, SteveThackery said:

 

Well, the "theory" goes that FI bikes have an electronic control unit (ECU), which could be susceptible to mysterious voltage or current spikes if you get it wrong.

 

The theory is wrong, though.  Removing or replacing the leads can't harm the ECU no matter which way you do it (unless you connect them reversed, of course).  Neither can accidentally shorting the battery leads.  If anyone wishes to challenge that, they are welcome to come and mess about disconnecting and reconnecting the leads on any or all of my three bikes.  If they succeed in blowing up an ECU I will cover the cost myself and issue public mea culpas.

 

The only thing that might harm the ECU is connecting one of those smart desulphating chargers, which send current spikes into a flat battery to break down the sulphation.  It is definitely feasible for those spikes to damage an ECU, and when using one of those you really should disconnect one of the battery leads.

 

Here's a little test: who knows why you should disconnect the earth lead from the battery first?

Thanks Steve. Very helpful. Much appreciated.

[Jeffprince 4,947]

7 hours ago, SteveThackery said:

 

 

The only thing that might harm the ECU is connecting one of those smart desulphating chargers, which send current spikes into a flat battery to break down the sulphation.  It is definitely feasible for those spikes to damage an ECU, and when using one of those you really should disconnect one of the battery leads.

 

Does that include the Optimate range? I use one for winter topping-up, without disconnecting the battery. Been doing it for years....

[Andy m 23,666]

Who knows. I meet the same sort of chargers and some cause damage and some don't. I think they are unpredictable as they are basically disposable and made in relatively small numbers. I would always undo the battery leads.

 

Andy

[Rocker66 34,498]

Like Jeff we have been using optimates on our bikes for years with no problems

 

[SteveThackery 3,090]

8 hours ago, Callisidrin said:

 

 

If you disconnect the positive first and slip there is a possibility of the tool you happen to be using touching the chassis while still touching the positive producing a dead short, not a good idea, so always remove the negative first.

 

Spot on.  If the tool touches the chassis when you are removing the earth lead, nothing happens and no harm is done.  Once that lead is removed, accidentally connecting the positive terminal to earth does nothing.

[SteveThackery 3,090]

9 hours ago, SteveThackery said:

The only thing that might harm the ECU is connecting one of those smart desulphating chargers, which send current spikes into a flat battery to break down the sulphation.  It is definitely feasible for those spikes to damage an ECU, and when using one of those you really should disconnect one of the battery leads.

 

 

Incidentally, I would add that the live feed to the ECU is disconnected anyway when the ignition is switched off, which further reduces the chances of damage from a desulphating charger.  Nevertheless, capacitive coupling just might (might) allow enough pulse energy through to damage the ECU, but I would say it's a theoretical risk rather than an actual one.

 

The internet is full of stories of ECUs being blown up in this way (including by connecting/disconnecting the leads wrongly), but I haven't yet seen any hard evidence.  It's always something that happens to someone else.

[embee 7,288]

I think some of this is probably historical. Modern auto electronics and ECUs in particular would usually have spike protection and reverse voltage protection, 20 or 30yrs ago this was probably not always the case.

[Andy m 23,666]

A lot of ECU'S have a permanent feed. It helps with data storage for diagnostics and clocks. The spike protection is usually diodes so not infinite.  A diode above its rating is just an expensive Fuse!

 

Andy

[SteveThackery 3,090]

28 minutes ago, Andy m said:

A lot of ECU'S have a permanent feed. It helps with data storage for diagnostics and clocks. The spike protection is usually diodes so not infinite.  A diode above its rating is just an expensive Fuse!

 

Andy

 

I agree.  However, I've yet to see an convincing explanation of how these voltage spikes actually arise, nor have I ever seen any solid evidence of an ECU damaged in this way.

 

Every internet user "knows" it to be true, even though it happened to someone else......

By the way, I've gotta say that auto electronics are incredibly reliable these days.  Thirty years ago, aftermarket electronic ignitions were sometimes questionable, but I can truly say the last time I had an ECU fail on a car or motorcycle in my ownership was back in 1986 on a Saab 900 Turbo.

[ste7ios 469]

Optimates will detect the vehicle circuitry and will skip the desulfation function. Always read your battery charger / maintainer user manual. It may contain important information. Not all chargers can do that, and not all apply the same (high) voltage. Some are conservative, some not and may also harm an AGM battery by drying it. 

 

It's always a good idea to remove the battery, or just disconnect the negative connector to avoid any voltage drop that may cause overcharging...

 

 

The connection / disconnection order is clearly a matter of our safety. To minimize the potential of a spark and the risk of explosion because the battery may gassing.

 

It's not unlikely to happen... It has happened to me with a large boat deep cycle AGM battery. It was gassing (no way to tell) because of overcharging and a spark in their storage area caused an explosion. The caps launched near my eyes... Thankfully nothing else happened, no acid spilled...

[SteveThackery 3,090]

1 minute ago, ste7ios said:

Optimates will detect the vehicle circuitry and will skip the desulfation function. Always read your battery charger / maintainer user manual. It may contain important information. Not all chargers can do that, and not all apply the same (high) voltage. Some are conservative, some not and may also harm an AGM battery by drying it. 

 

It's always a good idea to remove the battery, or just disconnect the negative connector to avoid any voltage drop that may cause overcharging...

 

 

The connection / disconnection order is clearly a matter of our safety. To minimize the potential of a spark and the risk of explosion because the battery may gassing.

 

It's not unlikely to happen... It has happened to me with a large boat deep cycle AGM battery. It was gassing (no way to tell) because of overcharging and a spark in their storage area caused an explosion. The caps launched near my eyes... Thankfully nothing else happened, no acid spilled...

 

Yep - sparks from accidentally connecting the spanner to the chassis is why you remove the earth side first.  And I agree - hydrogen explosions are rare (it has a surprisingly limited mixture range of flammability in air) but they definitely do happen.

[ste7ios 469]

13 minutes ago, SteveThackery said:

 

I agree.  However, I've yet to see an convincing explanation of how these voltage spikes actually arise, nor have I ever seen any solid evidence of an ECU damaged in this way.

 

Every internet user "knows" it to be true, even though it happened to someone else......

By the way, I've gotta say that auto electronics are incredibly reliable these days.  Thirty years ago, aftermarket electronic ignitions were sometimes questionable, but I can truly say the last time I had an ECU fail on a car or motorcycle in my ownership was back in 1986 on a Saab 900 Turbo.

As usual some things of the very distant past still remain alive... Now they're myths about batteries (e.g. the concrete floor discharge... The cases are not wooden anymore!), oil, etc... it will never change!

[SteveThackery 3,090]

8 minutes ago, ste7ios said:

As usual some things of the very distant past still remain alive... Now they're myths about batteries (e.g. the concrete floor discharge... The cases are not wooden anymore!), oil, etc... it will never change!

 

Indeed.  A lot of this comes from the fact that many people find electrickery and electronics sort of mysterious and "magic".  Knowledge of the mysteries is limited to an "elite", who can do magical things with multimeters and smouldering sticks to make the magic do their bidding.  

 

As with all magical things, superstitions rapidly arise.  If you don't do the rain dance every Spring the rains won't come and you will starve.  If you don't remove the battery leads in the way described in sacred ritual, the electricity will be angry and destroy your ECU.