Topic: Battery Voltage vs. Cranking Power?

[Popwood]

So today my 750 started right up, rode to work. At lunch, made a short trip and started right up on the outbound trip part. Coming back, just clickclickclick solenoid noise and no electric starter. Kick started fine. Checked battery voltage level at work, 12.25. But still, clickclickclick. Kick started to ride home. Very slight lift in battery voltage reading after six mile ride where I purposefully kept the rpms high. At home, slight increase in battery voltage reading, say 12.31.

Put battery on charger until charger read "full." Battery voltage reading 12.41. Tried to start with electric starter, clickclickclick.

Now my 550 battery voltage reading is 12.18 and the starter will crank and crank. So, with the 750 reading a higher voltage, why won't it turn the electric start?

The 550 battery is a year old. The 750 battery, who knows? I just bought the bike a couple months ago.

So is it the battery or should I be checking for another problem???

[mlinder]

What does the battery read when you are pressing the start button?

[Bob Wessner]

Perhaps a long shot, but my 750 developed this same condition this year on an intermittent basis. Electrics good, starter switch good, crossed the posts on the starter solenoid with a screwdriver and the starter turned over fine. I ended up taking the heavy leads off the solenoid and giving them and the posts a good cleaning. This took care of my problem. I'm assuming I wasn't getting a good clean contact on one or both posts. Worth a try anyway.

[BlackMax]

So today my 750 started right up, rode to work. At lunch, made a short trip and started right up on the outbound trip part. Coming back, just clickclickclick solenoid noise and no electric starter. Kick started fine. Checked battery voltage level at work, 12.25. But still, clickclickclick. Kick started to ride home. Very slight lift in battery voltage reading after six mile ride where I purposefully kept the rpms high. At home, slight increase in battery voltage reading, say 12.31.

Put battery on charger until charger read "full." Battery voltage reading 12.41. Tried to start with electric starter, clickclickclick.

Now my 550 battery voltage reading is 12.18 and the starter will crank and crank. So, with the 750 reading a higher voltage, why won't it turn the electric start?

The 550 battery is a year old. The 750 battery, who knows? I just bought the bike a couple months ago.

So is it the battery or should I be checking for another problem???

Volts don't turn the engine over.  Amps do. Amps x Volts = the amount of work that can be done.    A damaged battery can read 12v, but not have enough actual energy to turn the engine.  However, this also may not be your problem.  Check voltage with the starter button down.

First, I'd doubt and triple check the connection to the + terminal.  Then, after that, I'd think about the connection to the starter.  A bad connection can't flow enough to start the motor either.    

If that's not it, you can test the battery with a load tester.  They're pretty cheap.  Come to think of it, just attach the tester to the battery.  Then, as mentioned before, crank the motor (or try to).  The volts should not drop by more than 1 or maybe 2 volts.  If they do, the battery failed the load test.  Mine reads 13.6.  When I crank the motor, it'll drop to 12.4....no less.

[Popwood]

WOW, HUGE drop off in voltage when engaging starter, like 7.6 volts average. Should I assume the battery is toast?

[mlinder]

Battery is, in fact, toast.

[Popwood]

Thanks mlinder and others. I suspected as much. At least it's an easy fix. And have you ever bought a bike that didn't need a new battery? Almost a given in my experience.

[BlackMax]

Also, consider spending the extra bucks and get a deep cycle type battery.  They can handle discharges and re-charges.  Regular batteries are about 30% in the grave, the first time you run it down to 0.  It will cost you a little more.....but you won't buy another battery.   On my KLR650, I keep buying the cheap ones and telling myslef that I won't let it run down.  Well, I'm on my 5th battery in 2 1/2 yeas!!  

[TwoTired]

Deep cycle batteries do not make good starting batteries, and starting batteries don't take well the deep cycling.  It has to do with how the paates are made and the plate separator technology.

Stating batteries had a lot of plate area and the plates are porous to maximize this.  In this way they can deliver high starting currents.  However, recharging them frequently fills the pores and reduces their capacity.  Plus the plate separators don't help guide the redepositing of metal back where it came from, so you can get holes in the plates over many recharge cycles.

The same technology that allows the deep cycle batteries to accept frequent recharge also limits the high currents needed by starting motors under load.

A starting battery is not supposed to be drained frequently, as it shortens it's life.
A deep cycle battery is not supposed to have super high loads placed on it, as that shortens its life.

FWIW

[BlackMax]

Deep cycle batteries do not make good starting batteries, and starting batteries don't take well the deep cycling.  It has to do with how the paates are made and the plate separator technology.

Stating batteries had a lot of plate area and the plates are porous to maximize this.  In this way they can deliver high starting currents.  However, recharging them frequently fills the pores and reduces their capacity.  Plus the plate separators don't help guide the redepositing of metal back where it came from, so you can get holes in the plates over many recharge cycles.

The same technology that allows the deep cycle batteries to accept frequent recharge also limits the high currents needed by starting motors under load.

A starting battery is not supposed to be drained frequently, as it shortens it's life.
A deep cycle battery is not supposed to have super high loads placed on it, as that shortens its life.

FWIW

True, but if it flows 120 cca's......it matters not.   I have a deep cycle in my vintage bronco that flows 650 cca's.   I'll take a deep cycle / solid lead plate battery any day.  It's just more money.

[TwoTired]

True, but if it flows 120 cca's......it matters not.   

A lot depends on the plate area of each.  Size matters. A deep cycle battery that fits into the same space as a starting battery will have less plate area.  It may flow 120A when new, but it won't remain "new" as long as a starting battery that is routinely kept near full charge.

I have a deep cycle in my vintage bronco that flows 650 cca's.   I'll take a deep cycle / solid lead plate battery any day.  It's just more money.

Again, it's about plate area in contact with electrolyte.  If you oversize a deep cycle battery to give it the same plate area as a starting battery, then you keep the starting current after the switch over.  But, the deep cycle battery (in order to maintain a decent life cycle) is a bigger/ heavier battery.  More lead and physical size is one reason why the deep cycle battery costs more money.  You also have to lug that extra weight and size around with the vehicle, which also has costs.

What's the age of the battery in your Bronco?  Does the bronco get regular use?

[BlackMax]

maybe 5 years on the battery.  I drive the Bronco maybe 4x a year. 

One other factor, at least for me, is that I tend to hook up a charger to my battery; maybe on 2 amps, and forget I did it.  I come back the next morning and the battery is shot.     Another reason why I like solid plate battery. 

The newer Absorbed Glass Matt batteries seem pretty nice.  I will likely get one for my KLR650 (killed it with the charger this month) and also replace what I have in this CB. 

[Gordon]

One other factor, at least for me, is that I tend to hook up a charger to my battery; maybe on 2 amps, and forget I did it.  I come back the next morning and the battery is shot.     

Get yourself a Battery Tender.  If it saves you from killing one battery it will have paid for itself.