Batteries & Charging

Shep

Shep

Shep of the Dessert
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The new bike has a 30amp battery and appears to charge OK on the bikes voltmeter, it starts OK when left for short periods but leave it for a week or so and it starts to struggle.

I've not charged the battery up fully yet (i'd rather sort the bike out, rather than mask the problem) & i'm not sure the bikes system appears capable of charging such a big battery in my current 80 (ish) miles per week (I probably start the engine only twice a week and at the moment dont use any lights during daylight) on recent trips I try and keep the revs up to ensure better charging (the poor battery performance appeared first when the clutch started slipping when I was keeping the revs down)

What do you reckon, is the standard charging system capable of charging a flat battery in 40 miles after a sluggish start?

Shep
 
From this:

http://bmwmotorcycletech.info/AftrMrktAlt.htm

I'd guess not. From memory a car needs 15 mins of running (with an alternator) to replace the charge taking when starting the engine first turn of the key. The voltmeter only shows what the regulator is supplying, you really need an ammeter to show what charge the battery is taking / the generator is providing. Something like this:

https://www.kisantech.com/index.php?cat_id=5

PS could just put it on a charger once a week.
 
Last edited:
Shep said:
I've not charged the battery up fully yet
Click to expand...


Therein lies a problem before you find anything else.

Charge it fully off the bike.

As was said in the previous post,it takes a fair while to restore what was used simply by starting the bike...then add in the useage while running.

I`m not sure what your bike`s charging circuit output amperage is,but just apply the simple fact that if it puts out one Amp,it would take 30 hours to fully charge your 30Ah battery.
If two Amps output,it would take 15 hours,etc etc.
Then equate that to how long the bike is running for.

So,best fully charge the battery with an off bike charger then see how things are.
As it is,you`re possible looking for a problem that doesn`t really exist while potentially developing a problem of your own through using a not fully charged battery. :thumb2
 
I agree with old fish breath, charge the battery up properly you idle old git :)
 
Alright, I admit defeat i'll put it on charge:blast

Reading the article John posted its very possible it will never recover a charge in the 40-45 mins of varied riding, hopefully the ride to Skye next week will enable it to remain charged, but i'll put some jump leads in just in case:augie

Now where's that RAC card

Shep
 
On my 100GS when in Germany and Italy in June I wondered if the battery would be ok with having to run the headlight all the time. Never had a problem, but then it did have some fairly long runs which hopefully your bike will get.
 
Shep said:
Alright, I admit defeat i'll put it on charge:blast
Click to expand...

:D :thumb2


Shep said:
Reading the article John posted its very possible it will never recover a charge in the 40-45 mins of varied riding
Click to expand...

I`ve never encountered a stock charging system that couldn`t keep a bike`s (previously fully charged....ahem ) battery charged during normal use.
Even if a battery of greater Ah rating than stock is fitted.

However,if you ride at low speeds a lot with added electrical accessories on most of the time (heated grips,heated clothing,extra lamps,other gadgets,etc)...plus lights on in daytime..then you`re approaching troublesome times.
That`s why the Police bikes had high output alternators which gave the full monty at low revs.
 
Hi

1. You should always start diagnosing an electrical problem with a fully charged battery

2. If the battery is going flat when the bike is just sitting there for a week there is definitely a problem. Are you leaving some electrical accessory switched on? Have you got a clock fitted?

3. If you have a multimeter, with the ignition switched off, disconnect the earth connection from the battery and measure the current between the battery and the earth lead.

4. The amount you have to charge the battery doesnt have anything to do with the size of the battery - you are replacing the energy taken by the starter motor in starting the bike. If the bike starts almost instantly, as it should, this energy is small and will be replaced after a few miles.

5. Try leaving the earth lead off the fully charged battery for a week, then reconnecting it and starting the bike. If the bike doesnt start exactly as it does with a fully charged battery - the battery is faulty.

6. The R100GS is fitted with a 240W Alternator. That means at full output the alternator is providing nearly 20A. That is far more than the battery can accept, so as Tarka says, unless you have loads of electrical accessories the standard alternator is perfectly adequate.



Steve
 
SJRoome said:
Hi


6. The R100GS is fitted with a 240W Alternator. That means at full output the alternator is providing nearly 20A.


Steve
Click to expand...

ah but it only gets up to that if all the diodes are working and the system is perfect iirc they dont produce that unless they are revving at 5000 rpm or more
 
SJRoome said:
Hi

1. You should always start diagnosing an electrical problem with a fully charged battery

2. If the battery is going flat when the bike is just sitting there for a week there is definitely a problem. Are you leaving some electrical accessory switched on? Have you got a clock fitted?

3. If you have a multimeter, with the ignition switched off, disconnect the earth connection from the battery and measure the current between the battery and the earth lead.

4. The amount you have to charge the battery doesnt have anything to do with the size of the battery - you are replacing the energy taken by the starter motor in starting the bike. If the bike starts almost instantly, as it should, this energy is small and will be replaced after a few miles.

5. Try leaving the earth lead off the fully charged battery for a week, then reconnecting it and starting the bike. If the bike doesnt start exactly as it does with a fully charged battery - the battery is faulty.

6. The R100GS is fitted with a 240W Alternator. That means at full output the alternator is providing nearly 20A. That is far more than the battery can accept, so as Tarka says, unless you have loads of electrical accessories the standard alternator is perfectly adequate.



Steve
Click to expand...

Excellent advice.

Can I add:

  • With the battery connected, test the resistance between the earth terminal of the battery and the frame

The resistance should be zero. If there is any significant resistance, you have a poor earth lead connection which may inhibit charging.

Greg
 
1. You should always start diagnosing an electrical problem with a fully charged battery - being charged as we type
#
2. If the battery is going flat when the bike is just sitting there for a week there is definitely a problem. Are you leaving some electrical accessory switched on? Have you got a clock fitted? - It has an alarm, but i've disabled that, and i'm not so sure its loosing its charge over the week more like its never really got charged in the first place

3. If you have a multimeter, with the ignition switched off, disconnect the earth connection from the battery and measure the current between the battery and the earth lead. - Will do

4. The amount you have to charge the battery doesnt have anything to do with the size of the battery - you are replacing the energy taken by the starter motor in starting the bike. If the bike starts almost instantly, as it should, this energy is small and will be replaced after a few miles. - I was assuming that a bigger battery needs a bigger charger if it is flat? If the battery is fully charged then it won't allow high amps to flow into it so any size charger will work, hence the use of optimates trickle chargers etc.

5. Try leaving the earth lead off the fully charged battery for a week, then reconnecting it and starting the bike. If the bike doesnt start exactly as it does with a fully charged battery - the battery is faulty. - i'll try that once I get a fully charged battery fitted (i have an isolator fitted to the positive side i've used that with some success but it's not conclusive)

6. The R100GS is fitted with a 240W Alternator. That means at full output the alternator is providing nearly 20A. That is far more than the battery can accept, so as Tarka says, unless you have loads of electrical accessories the standard alternator is perfectly adequate. - Adequate to charge a flat battery in 40miles?


Cheers for the replys

Shep
 
Hi

The battery is 30Ahr. That is a measure of the total charge it can hold. As a rule of thumb a battery can only be safely charged at about a tenth of its capacity, i.e in this case 3A so whatever the size of the Alternator its going to take over 10hours riding to fully charge it from flat.

Steve
 
SJRoome said:
Hi

The battery is 30Ahr. That is a measure of the total charge it can hold. As a rule of thumb a battery can only be safely charged at about a tenth of its capacity, i.e in this case 3A so whatever the size of the Alternator its going to take over 10hours riding to fully charge it from flat.

Steve
Click to expand...

Cheers:clap I'll set off now:thumb2:D

Shep
 
Shep said:
4. The amount you have to charge the battery doesnt have anything to do with the size of the battery - you are replacing the energy taken by the starter motor in starting the bike. If the bike starts almost instantly, as it should, this energy is small and will be replaced after a few miles. - I was assuming that a bigger battery needs a bigger charger if it is flat? If the battery is fully charged then it won't allow high amps to flow into it so any size charger will work, hence the use of optimates trickle chargers etc.
Click to expand...

you only need a bigger charger if you want it to charge in the same amout of time. so in other words it will take a bit longer to charge
Shep said:
6. The R100GS is fitted with a 240W Alternator. That means at full output the alternator is providing nearly 20A. That is far more than the battery can accept, so as Tarka says, unless you have loads of electrical accessories the standard alternator is perfectly adequate. - Adequate to charge a flat battery in 40miles?
Click to expand...
No. it will take about 1.5hours at 70mph/ 5000rpm to charge a totaly flat 30ah battery
 
SJRoome said:
The battery is 30Ahr. That is a measure of the total charge it can hold. As a rule of thumb a battery can only be safely charged at about a tenth of its capacity, i.e in this case 3A so whatever the size of the Alternator its going to take over 10hours riding to fully charge it from flat.
Click to expand...

Best not have a look a third of the way down here then:

http://bmwmotorcycletech.info/AftrMrktAlt.htm

20 amps at 2850 rpm, but that might not be what is charging the battery :eek:

How long does the 40 miles take, and is there much low speed stuff, ie below 1500 rpm?

Another link of interest: http://www.gunsmoke.com/motorcycling/r100gs/charge_diagnostics/index.html and

http://www.gunsmoke.com/motorcycling/r100gs/charge_guard/index.html
 
Last edited:
Hi

The 20A is the maximum amount the alternator can provide. The actual amount it will be providing is equal to the amount being used by all the other electrical equipment on the bike (ignition, lights etc) plus any that it is putting into the battery. The battery will only be charged if the alternator is putting out more than the bikes electrical equpment is using (and as the link John is pointing to says) this occurs above about 1550 rpm if you have your lights on and everything is in perfect condition.

The amount of current being used to charge the battery is set by the regulator. This will depend on how charged the battery is, its temperature, how the regulator is set etc but in practice will not go much above the capacity of the battery divided by 10.

So a bigger alternator, diode board etc will let you fit more electrical accessories but it wont make a flat battery charge quicker. A better alternator will also let you spend more time at low engine revs without losing charge. A regulator set to a higher voltage will also let you spend a little more time at lower revs and will slightly reduce the time taken to fully charge the battery at the expense of a reduced battery life.

Steve
 
Nippy Normans supply Touratech, Wunderlich, Desert Fox and many other makes of accessories.
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