Best Battery To Use

if your bike calls for battery abc, then use abc.
using a different battery, like replacing a yuasa 5xxx with a 7xxx is wrong.
in this example the 7 puts out a higher amp rating. so guess what happens?
the motor tries to spin too fast and the the sprague disconnects.
it goes crank, crank, disconnect.
i have seen this first hand, several times.
the 5 series will crank over continuously till the battery goes dead.
the 7 series spins the motor twice and disconnects.

also, using a heavier weight oil will do the same thing. it adds to much drag and causes the starter to prematurely disconnect.[something i have never done].

tuts
:devil:

Interesting perspective !

A chain isn't stronger than the weakest link, correct ??

Anders, DK

Unfortunately the standard 5xxx doesn't turn over an 02 650, certainly not mine and that is with all the de-comp mods in the docs, correct oil etc. etc.

If the 5's were ok then why do they use 7's as standard now? Evolution.

Carl

tuts said:

...the motor tries to spin too fast and the the sprague disconnects.

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This is the first time I have heard someone say the starter motor is putting out too much torque! To me it would seem to indicate a problem with the torque limiter clutch on the starter rather than the output of the motor.

Are you sure about your logic with the larger battery size thing? I would certainly agree that fitting a smaller battery is asking for trouble. The starter systems seem to be marginal at the best of times.

RE: Re: Best Battery To Use

a battery only provides as much amperage as the device being powered wants. limits are due to the resistance (both mechanical and electrical) of the load.

RE: Re: Best Battery To Use

Torque in a DC motor is proportional to current. If a battery cannot provide the amount of current necessary to achieve the rated torque of the motor then by default it has limited the motor torque.

i.e. a starter motor could require 100A during starting but connected to a battery only delivering 25A

Re: RE: Re: Best Battery To Use

kzoo said:

Torque in a DC motor is proportional to current. If a battery cannot provide the amount of current necessary to achieve the rated torque of the motor then by default it has limited the motor torque.

i.e. a starter motor could require 100A during starting but connected to a battery only delivering 25A

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Yes but, if the starter requires 100A putting a battery that is bigger won't force more amps to the starter.

In fact when comparing a 5Ah and a 7.5Ah battery (same type,manufacturer and state of charge) during starting the 7.5Ah will push less amps but will have a higher voltage when compared to the 5Ah. This is the main reason that bigger batteries last longer, they don't have to work as hard.

RE: Re: RE: Re: Best Battery To Use

I did a test or sorta of. My bike wasnt not turn over the engine fast enough or sometimes at all. I put it on a battery tender device 1amp hour 12 volt deally for about 2 - 3 hours and now it starts rate up.

Re: RE: Re: Best Battery To Use

JoeT said:

Yes but, if the starter requires 100A putting a battery that is bigger won't force more amps to the starter.

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That part is obvious, a load will draw what it can. My point was that if the source can't provide it, you will have diminished performance.

RE: Re: RE: Re: Best Battery To Use

E
--------
I x R

E = Electromotive force (potential difference / voltage)
I = Intensity (Amperage)
R = Resistance in Ohms

did we forget Ohms law? potential difference of the battery is always gonna be 12.xx VDC no matter the storage (Ampere-Hour Capacity) you could hook up a car battery if you wanted. it just doesnt have to work as hard.

simple math here. plug in the numbers, play with higher or lower resistances and see what happens to the current....
lower resistance = higher current and vice versa.

You can always apply ohms law, but not quite as simply as that. Every power source can be thought of as a pure voltage source in series with a resistance - the internal resistance of the battery in this case.

If a 12V battery drops to 9V (3V drop) when supplying 200A its internal resistance must be R=V/I=3/200=15milliohms.

For any given load resistance, the battery internal resistance must be added to it to calculate the total circuit resistance and hence the current flowing through it.

If the load resistance is much larger than the battery resistance then reducing the battery resistance (bigger or smaller battery) has bugger all effect. If they are of similar magnitude it matters heaps.

Assuming the locked resistance of the starter is of the order of R=9V/200A= 45milliohms, the 15milliohms of the battery is significant in determining the final current through the starter.

A larger battery should have a lower internal resistance (but not always - eg flat or sulfated). The lower resulting total circuit resistance means more current does flow. This is in a round-about way how they come up with the CCA guide, but it has to be referenced against some standard load - not the actual starter on the bike.

To further complicate it, once the starter begins spinning, it generates a voltage in the opposite direction to the battery that subtracts from its voltage. The starter resistance remains roughtly constant. As a result the net voltage and hence current drops as it speeds up.

Also, as the battery starts delivering power when cranking it goes flat, increasing its resistance and reducing its voltage a tiny bit. It also warms up which decreases its resistance. Somewhere in there are the actual conditions the starter is working under at any instant.

BundyBear said:

If a 12V battery drops to 9V (3V drop) when supplying 200A its internal resistance must be R=V/I=3/200=15milliohms.

To further complicate it, once the starter begins spinning, it generates a voltage in the opposite direction to the battery that subtracts from its voltage. The starter resistance remains roughtly constant. As a result the net voltage and hence current drops as it speeds up.

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mmm, counter electromotive force. took me a bit to wrap my head aroud that in school.
also, you use the 3V drop rather than the 9V source voltage for the equation?


what i was getting at is that the resistance in the circuit directly relates to amperage draw.
a higher A-H capacity wont make your re-starter "not work" unless their is another problem.

I guess the idea of internal resistance is trying to explain why and by how much the voltage at a battery's terminals will reduce for a certain current drain. I suppose that is why the drop is used to calculate it.

Yeah yeah, sods law divided by the rate of inflation is fine but for us simple fen folk, which is best...the Ctz 7s which championed by some due to its glass fibre internals or the more expensive gel Ytz 7s which I believe is recommended by Husaberg ??

varta i use,

Yeah yeah, sods law divided by the rate of inflation is fine but for us simple fen folk, which is best...the Ctz 7s which championed by some due to its glass fibre internals or the more expensive gel Ytz 7s which I believe is recommended by Husaberg ??

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Neither are Gel, both are AGM. They may be of differing quality, but the same technology. Yuasa does not make Gel powersports batteries, nor any other major manufacturer of powersports batteries(there is no advantage over AGM).

In my opinion Yuasa and Yuasa variants( Yuasa has several differnet labels that are in fact the same battery) are one of the best but given the premium Yuasa gets for their batteries, not always worth the price difference.

BRN2RDE

The CTZ's and YTZ's are the same batteries (Absorbent Gel Matting) just different manufacturers, you should be able to find Yuasa YTZ for around £45 from Barden Batteries.

Carl

(Absorbent Gel Matting)

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That's actually Absorbed GLASS Matt.

That is where alot of the Gel/AGM confusion lies. Gel's are great for extreme discharge situations, such as electric wheelchairs, no advantage in a starting type application

BRN2RDE

Cheers BRN2RDE

Sooooo...the ctz£45.00 is actually a ytz £80.00 under a different branding buuuuuuut....it would be better to get a ytz at £45.00..........I think I'm missing something here chaps..doh

James