Help. How to check if current is drawn from battery

Spaceman Spiff · May 1, 2021

Hi

Please forgive my inexperience.
My 1200 GS LC’s battery is not retaining its voltage. After a day in the garage it is at 11.5-11.6v. Ashy longer and it drops to 11.2v. Mean I need to keep the bmw battery charger plugged into the aux socket and make sure before a ride that it has been running and charging the battery.

After using the charger, voltage is at 12.1-12.4v and starts fine. But if battery is below 11.8v can’t start it. Once on a ride it charges fine and I can be the whole day out with it starting every time.

So I’m assuming it is drawing current from somewhere. The gps is removed when in the garage and the alarm is off.

So having borrowed a multimeter, could someone please advice how I check, incl if I need to connect the leads in parallel or serial and please what to look for.

Thanks for the help.

JJH · May 1, 2021

Simple way to check. Disconnect battery and see what it’s like to start the next day. JJH

AberdeenAngus · May 1, 2021

Disconnect one of the battery leads and attach the meter in series. Set the meter to current range.
With the ignition off, tells us what current is being drawn.

mikeyboy · May 1, 2021

Disconnect battery,
Put meter in ampere.
Put meter leads between batt cable and terminal so meter is in series with the two.
If it’s more than a few amps it will blow the fuse in the meter.
I doubt it will be tho as the battery would be flat in a couple of hours if it’s more than an amp
Modern battery’s aren’t up to much,
I was changing them every year on my old 1200 till I started buying proper ones.

tanneman · May 1, 2021

And from here you can unplug each system or farkle in turn and to determine where the fault is.

Apex · May 1, 2021

If I were you I'd pop the battery out. Pop to a bike shed. Get them to pop a battery tester on it. If it's poop, pop to a shop, buy one and pop it in your bike.

Sent from my iPhone using Tapatalk

Alan R · May 1, 2021

Apex said:
If I were you I'd pop the battery out. Pop to a bike shed. Get them to pop a battery tester on it. If it's poop, pop to a shop, buy one and pop it in your bike.

Sent from my iPhone using Tapatalk

You are a Poppet!

Alan R

Spaceman Spiff · May 1, 2021

Apex said:
If I were you I'd pop the battery out. Pop to a bike shed. Get them to pop a battery tester on it. If it's poop, pop to a shop, buy one and pop it in your bike.

Sent from my iPhone using Tapatalk

Thx. I did that about 10months ago and having the same issues. Thus why trying to find what is causing it.

Spaceman Spiff · May 1, 2021

Thanks all. I’ll see what it reads tomorrow and then start looking to see if anything specific is causing it.

Santa-2512 · May 2, 2021

Spaceman Spiff said:
Thx. I did that about 10months ago and having the same issues. Thus why trying to find what is causing it.

Cheap battery?

Mottobat - very much better £60 - £80 or Odyssey - dogs danglies £120

Rockred · May 3, 2021

Have a look at this, it gives you some interesting information. I would put the probe on the negative terminal first though, probably me being over careful.

https://www.bing.com/videos/search?...663B1099FD0D80C5F6E3663&view=detail&FORM=VIRE

Spaceman Spiff · May 3, 2021

Hi

An update.

So checked the voltage midday and it was 12.1v.
When I turned the ignition it drops to 11.6v, but when turned off and left for about 5min it is back at 12.1v

Connected bmw charger through the aux port and charged the battery. When came back a few hrs later voltage read 12.8v and the bike started fine. After starting voltage went up to 13.1v idling, but climbed to 14.1v when opened throttle. When bike was switched off voltage after set at 12.8v.

Came back next morning and tested voltage and it was 12.1v again.

Disconnected the negative terminal and checked the current. Initially could get no ampere reading, but briefly went to 9mA, before going to 0 again.

The battery I have is a replacement yusa. For interest I tested the old bmw battery I still have that I have not used for about 6 months and it read 12.4v.

mikeyboy · May 3, 2021

Battery is fucked
Most of your voltage readings are irrelevant,full load current is the thing here.
Put the batt on a load test.

Edit.
Either the above or the main batt leads cannot carry current.
Poor earth,
Corroded starter cable

tanneman · May 4, 2021

Volt (V), the potential difference describes the ability for electrons to flow.
Ampere (A), current describes the ability to do work.
Power which is calculated VxA.

To turn a motor you need a strong current flow, like water turning a waterwheel. A weak stream will turn it just so so, but in a flood it will spin much faster as more water flows past.

It is exactly the same concept with a battery. It can have a potential difference between positive (+) and negative (-) of 12V but if the current that it will transmit is low it won't turn the starter. These 2 are also related to each other in the inverse ie the higher the voltage the lower the current will be. Remember the calculation for Power, VxA? To produce the same power if the current drops low the voltage has to increase and vice versa.

You can measure volt all day long but it will give you no idea of the state of the battery.
The reason for a poor flow of electrons can be;

low current ie spent battery.
poor connections ie high resistance.

Help. How to check if current is drawn from battery

Spaceman Spiff

Registered user

JJH

Well-known member

AberdeenAngus

Registered user

mikeyboy

Well-known member

tanneman

Incomplete Arse

Apex

Well-known member

Alan R

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Spaceman Spiff

Registered user

Spaceman Spiff

Registered user

Santa-2512

Omnipotent one

Rockred

Well-known member

Spaceman Spiff

Registered user

mikeyboy

Well-known member

tanneman

Incomplete Arse

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