Battery problem, maybe

[allanb]

This is not about driving cars, but it is about a 12v battery.  The "vehicle" is a 3-year-old ride-on mower, and the problem is that it won't start.  (It's out of guarantee, of course.)  The engine is a 4-stroke Briggs & Stratton.  The battery tries to turn the engine, but can't manage more than about a quarter of a turn.

I have succeeded a couple of times using cables from a car battery, but even that sometimes doesn't make any difference, and when it does work it's still very sluggish.  I have cleaned and tightened all the connections, more than once.  The

mower has been back to the dealer's workshop to see whether he can find

anything wrong, but he can't.  When it came back from the dealer it started perfectly for a couple of days; then it wasn't used for 4 or 5 days, and now the problem has returned.

The battery shows about 14v on a voltmeter.  The dealer could probably have persuaded me to buy a new battery, but he didn't try; he says the voltage reading shows it's in good condition.

The only question I can think of asking is: is it possible for a battery to show a good reading on a voltmeter but still to be incapable of starting the engine? 

[Bugsy]

Allan, The answer to your last question is yes. If your battery is three years old, you,ve done very well.

From the symptoms described the  first thing I would check is the earth connection to the chassis.

Then,

To test your battery under load, connect a multimeter to the battery (note the voltage), crank the starter and watch the reading. If it drops dramatically, below 9v, the battery is suspect.

Good luck

Gary

[Anton Redman]

If and only if you : Know the radio codes for your other vechiles. You have more than one other vechile. Try bolting the connections from to you car batttery ( you may also need to depress the safety cut out under the seat ) and see if it starts / turns over well.

These days I would expect a battery to live longer than three years. Diesel Peugeot now at 6.5 years and 182,000 miles on original battery 

[Ford Anglia]

This happened to us recently with an oldish Xantia. Wife swore me down it was the battery as it was sooooooooo sluggish and sometimes refused to start/trun over at all.

Then it would be OK.

Grammar school physics says a battery CAN'T behave like this, so I suspected the starter.

Sure enough, a check found the starter commutator badly burnt from a previous diesel leak.[Www]

One new starter, and no more problems.

[allanb]

Bugbear: thanks for the advice.  I have checked the earth connection.[quote]To test your battery under load, connect a multimeter to the battery (note the voltage), crank the starter and watch the reading. If it drops dramatically, below 9v, the battery is suspect.[/quote]I've tried this, and the voltage did indeed drop, to around 9.  So I lashed out and bought a new one (especially since it seems to be the general view that two or three years is a reasonable life for these small batteries).

However, the new battery won't turn the engine either, and when I checked the voltmeter readings they were actually a bit lower than with the old one (12.8v with no load, 8.8v while cranking the engine).

Does this voltage drop necessarily indicate a battery in bad condition, or could it simply mean that the battery isn't fully charged?  I haven't yet tried putting it on a charger.  If I have to take it back to the shop for exchange, it will probably be better if I've done nothing to it. 

[Nick Trollope]

Given your description oft he fault, I can't conclude that it is the battery - especially as you have changed it! Although the hint is in the fact that you can't jump start it. I would expect a good battery under too great a load to drop to about 8V - the point at which the internal resistance of the battery means that no more current can be extracted. I doubt if it is a bad connection as this would tend to increase resistance and hence reduce current & voltage drop.

Is there something stopping the engine turning, such as a jammed cutter deck or drive belt. When it starts, does it run OK or is there any unexpected noise?

It could, of course be a faulty starter motor, or a partially siezed engine. Remove the starter motor & see if it turns freely by hand and when powered, etc etc..

Thought - they are dynostarters on the B&S motors (they are both motors to start the engine and dynamos to charge the battery), so there are plenty of other failure modes.

 

[Bugsy]

[quote user="allanb"] 
  When it came back from the dealer it started perfectly for a couple of days; then it wasn't used for 4 or 5 days, and now the problem has returned.

[/quote]

That is the confusing bit about this problem and suggests that the problem is electrical rather than mechanical.

The question now, as Nick says, is does it run OK when started ?

a couple of checks...................but it really is difficult trying to do a 'virtual diagnosis'

Flip off the drive-belt at the bottom of the engine and try it.

 

[Gluestick]

Pretty obviously, if a new "known good" battery fails to crank the engine effectively, then there is in all probability an electrical problem.

Of course, if the relevant safety interlock switch is working properly, it is impossible to crank the engine when it is (a) driving the cutter deck and (b) in gear, thus the engine should be in a no load condition.

Worth remembering that the safety/interlock switches normally operate in the following areas:

1.    Seat in case the driver falls off; in order that the machine does not mow the driver!

2.    Gears; should only start in neutral:

3.    Cutter Deck: should only start when this is disengaged:

4.    Handbrake: should only start when brake safely engaged.

These interlock switches only cut the feed to the solenoid.They can easily be checked using a simple meter.

My Rally which uses a B & S engine, has given trouble with the adjustment of these switches.

Anyway, assuming they are all OK. Check out the battery wires, earth and feed. It is possible that the feed wire has gradually frayed, internally with no visual sign. The only way this can usually be traced is by removing it and connecting to a multimeter using the resistance function in series and physically bending the wire along its whole length. The problem is this is a No Load test and might not work.

The problem with starter motors is that the initial surge current is in the hundreds of amps, as the starter motor overcomes the friction resistance of the engine. And it is this huge current load which will show up a partially frayed cable.

Substitution is probably the correct approach.

The starter motor should reveal much from a physical inspection: burnt and badly pitted commutator etc. burnt out segments, burnt out field coils; all will produce the effect you are suffering.

The best way is to take the whole starter-charger unit to a dealer and have them test it: must be one with the correct rig though!

As always with electrical faults, it is a logic process, not a process of substitution beloved by garages! With the customer paying for all the parts and labour! You know, "Well we've changed the starter motor, fitted a new battery and a new alternator (??? Huh?), fitted a new solenoid and changed all the cables, replaced the igntion switch and the ECU and it seems to start OK now!"

 

[allanb]

I'm almost afraid to post this, in view of all the time and effort that's gone into advising me.  But I was talking about the problem to a mechanic in the depths of the dealer's workshop, and he said: "Ah yes, the problem is that these batteries are just too small.  In the good old days they would put a man-sized battery on a machine like this, but now they're all obsessed with saving weight, so they fit a tiny battery and give you a free battery charger with the machine."  (He's right, they did.) "They don't tell you this, but you should simply keep it on the charger 100% of the time when you're not using it."

But, I said, they told me the new battery was fully charged.  "Yes," he said, "they always say that."

So I've put it on the charger and I'll try again after 24 hours.  If it starts, and keeps working, I'll apologize to all of you for wasting time.

[Gluestick]

If the battery was discharged it would never show 14 volts!

The nominal voltage of a lead acid cell array (I assume 12 volts since mine are and both are Briggs and Stratton engines) is 12.6 -12.8 volts, open circuit and 10.5 volts fully loaded both when completely charged.

Of course, the best way to test the charge is with an hygrometer, which measure the Specific Gravity of the electrolyte in each cell. (Interestingly my original Rallye batteries were both sealed cells; but my new replacement  - made in Korea, natch! -  battery make Oregon, is open cell which is 'andy 'arry!).

A smaller battery just simply means that it cannot deliver a higher surge current and its Amp Hour capacity (i.e. the rate in Amperes per Hour it can be discharged from fully charged to flat), will be smaller.

Both a function of the plate area.

Please let us know how the mower performs once you have charged the battery.

BTW: the time it takes to charge the battery is the amp/hour capacity (probably something like 30 it should be on the battery) and the charge rate of your charger in amps, probably 2. Thus if the battery is 30 Amphours and the charge rate 2 amps, then from flat to fully charged is 15 hours.

Don't overcharge it as it will bubble the electrolyte, overheat and start to dump the essential paste in the plates (if this method) or sulphate the plate surfaces and thus increase the internal resistance and lower the capacity. Enough is enough!

Lead Acid batteries are best charged very slowly (typically .25 Amp) for a long time: i.e. Trickle Charged.

 

 

[Bugsy]

Get yourself one of these. They are designed to be left on all the time and work brilliantly.

[allanb]

[quote user="Gluestick"]The nominal voltage of a lead acid cell array (I assume 12 volts since mine are and both are Briggs and Stratton engines) is 12.6 -12.8 volts, open circuit and 10.5 volts fully loaded both when completely charged. [/quote]

Does this mean that if the battery is in good condition and fully charged, a meter should show around 10.5v even while the starter is cranking the engine?

(I'm neither an electrician nor a mechanic, in case you hadn't guessed.)

By the way, my battery is completely sealed and is described as a 'gel' battery, which reduces my options, I think.

[allanb]

Sorry, removing duplicate post.

[Gluestick]

Nominal voltage. It could go as low as 7 volts in practice, If  you had another problem (in the starter motor e.g.), or the leads.

The old rule of thumb quick test with a car was to turn on the headlights and crank the engine. If they died, you knew you had a problem! Unfortunately that doesn't neccessarily work these days, as most cars ignition switches de-load everything when cranking!

I suggest you charge tonight, as per plan and post the answer in the morning!

Meanwhile I will check the nominal voltages of gel type Lead Acid batteries: although I can't see they  would be much different. Same principle.

 

[Nick Trollope]

Sorry GS, but this can't be an electrical problem - it is mechanical. The interlocks are not in the high-current circuit (they just disable the ignition or the starter relay), so they can't be at fault.

The battery capacity is the one designed for the machine (mine is fine after 2 years and is about the size of a fag packet!) but as you say, the limiting factor is the cranking time and current, but this is a function of the design, not the battery capacity.

I'd still plump for a knackered dynostarter - has the machine got lights? - usually a good indicator of the type of starter. All the B&S mower engines I have seen have got them (dynostarters, I mean).

 

 

[Gluestick]

Nick, I always but always bow to your superior knowledge on electricals and electronics!

[IMG]http://i74.photobucket.com/albums/i278/Michaeleff/kneelsuckers.gif[/IMG]

However, in this case after your earlier post, I was thinking, logically through this conundrum, as I do [blink] and considering n years spent diagnosing misfunctioning motor cars and their electrical systems and then thinking about my own mowers.

You earlier suggested that if the mower had a jammed cutter deck or drive belt.................., but of course, if the interlocks are all working it would be impossible to actually crank the engine, as the solenoid would not engage; this was the point I was making. Badly it seems!  [:$]

In point of fact I tend to agree with you: it must be either a dyno/starter problem, or it could be a frayed feed cable (under the insulation). These of course are pigs to find!

My batteries are tiny too: doesn't stop 'em costing an arm and a leg though, does it! € 50 last year for one of the Rallyes! [:@]

Both of mine have the exterior light moulding in place on the bonnet (hood?) but no light in situ.

Am I bovered?

 

 

 

 

[tracteurtom]

Goodness me, what a load of drivel !

Does it crank  with the spark plug removed ?  Is the engine free to turn by hand with the plug removed (it should be)?

Does one cable or connection get hotter than the rest (indicating a duff joint ?) or do they all get hot indicating an overloaded motor ? Dont crank or try to crank for long periods without a rest as you will damage the starter motor, they dont have a long duty cycle.

What is the starter solenoid on these motors ? that could be the problem - does it get hot ?  Measure the volt drop across it.

Another possibility is that there is way too much oil in the engine, causing too much drag.

Another load of drivel - sorry  ! 

[Sunday Driver]

Has anyone tried kicking the tyres.....?

[:D]

 

[Gluestick]

[quote user="pcwhizz"]
What is the starter solenoid on these motors ? that could be the problem - does it get hot ?  Measure the volt drop across it.
[/quote]

Cor! What a load of drivel!

It's a sort of switch, which has big fat contacts to switch the surge current of approx >500 amperes, and uses an electromagnet to close the heavy duty contacts.

BTW: With the size of the tiny battery, and the thinness of most ride on mower battery cables, they will all become hot with extended cranking. [:D]

 

 

[Gluestick]

Well, put us out of our misery, AllanB.

Did the overnight re-charge work?

All now sweetness and light? Grass manicured?

Or is it continuing rude words?

 

[tracteurtom]

GS, Any auto lecky will tell you that when trying to fault find starter motor problems, to feel the cables and connectors for hot spots.  This is a sure sign of a poor resistive connection that is stopping the motor from drawing the current it needs.  Yes things will get warm, but should not get too hot to touch.  You must not try to crank for too long as I pointed out before, the duty cycle of these starter motors (and indeed those on many cars of today) is very short (5 secs in 60 secs) and they are easily damaged though over use and the resulting overheating.

So thats a bit more drivel then  !  Bet the problem  is no more than  a flat battery   [:D]

[Gluestick]

As an ex sort of adopted automotive electrician (with the burns and the scars to prove it!), in one part of my life, it depends whether the starter motor (or Dynostart) has gone high resistance or open circuit.

If say part of the field coils or commutator have gone OS, then there will not be a contact resistance (comm) problem or too few coils in circuit (field coils) problem to create the sort of high current problem which will cause heating of the cables. Ergo no heat.

Local heat is normally in my experience a bad connection (high point contact resistance), or - agreed - a burnt out comm which has shorted between segments etc.

Or, as I pointed out before, partially frayed cable inside the insulation.

Having struggled with the weird logic of my Rallyes, until I doped it out, I agree highly unlikely to be a duff battery. That said, however, I could recharge mine, start cutting; stall it, listen to it do the urgh, urgh, urgh groans; and leave for fifteen minutes (beer and a disgusted rest!) and it would whiz over and start like a good 'un! [8-)]

My new battery seems to have solved most of the problems: except of course the "wet grass jamming the cutters and burning nice flatspots on the main drive belt which costs € 40 a pop and means grovelling around on my bum, taking out the whole cutter deck to change it!", problem!

Sigh......................[blink]

 

 

[allanb]

Sorry to keep you all in suspense, but a minor crisis distracted my attention and my new battery got 48 hours on the charger, not just 24, before I tried it.  And now it's working!

It's a pity to come to such a boring ending, but it really looks as though my problem was just a bad battery.  Unfortunately the first person I spoke to in the dealer's shop didn't know enough to test it properly, and I didn't know enough to question him about it.  Unfortunately also, the second person I spoke to in the dealer's shop told me that the new battery would be fully charged, and I didn't know enough to challenge that either.

So we had incompetent advice being given to an ignorant customer: it's an unbeatable combination.

However, because of this thread, I now have a list of thirty-eight things to check if I ever have a starting problem in the future.  My thanks to you all.

[Gluestick]

Glad it's all worked out, AllanB.

Now take Bugbear's advice and treat yourself to a "Smart" charger.

These are used on collector's cars, mowers, invalid buggies whatever. They keep the battery always topped right to the top. The battery will last much longer also.

 

[allanb]

So far as the mower is concerned, isn't it likely that the charger that came "free" with the machine is the same thing that you describe?  The instructions say that it can be left connected all the time with no risk of overcharging.

But in any case I might invest in one that can be used with a car, if it can safely be left connected - e.g. while we are out of the country for a month.  Is "Smart" a brand name, or just a description?