Topic: Use a 2 amp "smart" battery charger?

[Magpie]

I have a weak 12 volt battery and the Battery Tender I'm using on it doesn't seem to give it full charge, at least not enought to turn the bike over. The bike will start with another battery in it. Can I use a 2 amp "smart" charger on it or will the 2 amps be too much for it? The battery is 2 years old but the bike has hardly been ridden unfortunately. It may be that this battery has just not had enough use and given up trying too.
Thanks,
Cliff.

[Accolay]

Charging the battery at more than 1/10th of the amp hour rating of the battery might cook it, speed up corrosion of the plates, bubble out all the water.

Maybe just closely monitor the battery while it's on the 2amp charger, and see how it goes?

[TwoTired]

The battery is probably sulfated.

If so, it won't matter how many amp charger you put on it, it still won't charge.

Sometimes, if the plates aren't completely sulfated, a high charge rate can get more sulfate off the plates and partially recover the battery to some useful state.  Then keeping it at full charge can mostly un-sulfate the battery.  Occasionally, the battery becomes useful agin.

I have a 6 amp charger with a current meter on it (purchased in 1964, HA!).  A good but depleted battery will show an initial charge rate of 6 amps.  A sulfated one won't accept much, if any, current even through there is plenty of voltage to offer a charge.

High currents should only be applied to known depleted batteries, and then monitored closely for voltage level at the battery, never letting the voltage go over 14.5 volts and watching for out gassing.  When parts of the internal battery have achieved full charge, the electrolyte starts separating the hydrogen and oxygen out of it.  This looks like boiling, but is actually making the electrolyte acid much stronger.  This eats away plate material faster.  If the electrolyte level gets too low, the plates can overheat and warp, shorting some of the cells together.

It is best to note the voltage level of the charged battery.  After a rest, the Voltage should settle to about 12.6-12.7 volts.
I use an old headlight to place a load on the battery, which draws 5 amps.  A good battery won't allow the voltage to drop during load below 10-10.5 volts with such a load.  Bad batteries won't even have 9v under such a light loading.  A bike and starter load of 30 amps, will take these bad batteries below 7v, which won't work the starter, and make spark unreliable.

There are many variations and characteristics of batteries in the range between good/new, and damaged/abused/bad.  The above are some general guidelines.

Cheers,

[Magpie]

Thanks guys!
So, TwoTired, if I hook up a headlight to this weak battery to do a load test, I can use a multimeter across the battery terminals to watch the voltage drop? I'll do that and report back.
Cheers,
Cliff.

[Magpie]

Tested the battery. First I tried to start the bike. The battery was at about 12.5V, then hit the starter and it ran out of gas very quickly, maybe a dozen revolutions of the motor. Took it out and did the bench test with the headlight connected to it. After between 5 and 10 minutes with the light on, the voltage dropped to about 11.2V. I've connected the battery to my battery tender to bring it up to max. charge. The tender will stop charging at 14.5V.
I thought it might be the bike at first because it's a rebuilt motor and quite tight. I took the battery out of my other bike and it started this bike right away. With the kill switch in the off position, it turned the motor over many times without seeming to slow down- so it's not the bike.
Strange.
Cliff.

[TwoTired]

If it sat a long while, it could be partially sulfated.  The sulfate coating reduces the effective plate area which reduces it's storage capacity.
Repeated discharge/charge cycles may bring it back to better storage capacity. (Leave it on the tender a week or two to recombine the sulfate coating.)

Alternately, the discharge cycles move metal from plate to plate.  There are two kinds inside.  A charging cycle moves them back.  But the metal doesn't move back exactly where it cam from.  Further, the plates are porous when new which give greater chemical access (more area) and more abundant conversion to amps via the electrolyte.  Recharging reduces the pore size (as does sulfate coating) and eventually reduces the output current capability.  Batteries that have many many charge cycles may have big holes in the plate.  The metal is still there it has just been redistributed in layers, reducing the plate area.

This is why starting batteries should never be allowed to deeply discharge, as doing so shortens their useful life.

Cheers,

[Magpie]

Thanks!
Cliff.

[dave500]

lead acid batteries are a use it or lose it thing,as two tired said about sulfation,, on a two year old battery it will be worse if it hasnt been used much,,also leaving otherwise good but flat batteries flat will cause irreperable damage.

[gnarlycharlie4u]

http://www.instructables.com/id/Desulfator-for-12V-Car-Batteries-in-an-Altoids-Ti/
boom.
I saw it on Hack-a-day

This too

[TwoTired]

http://www.instructables.com/id/Desulfator-for-12V-Car-Batteries-in-an-Altoids-Ti/
boom.
I saw it on Hack-a-day

This too

I've heard the claims.  I've not seen any proof.
The battery presents a huge impedance to high frequencies, essentially blocking them at the battery terminals.
How the "high frequencies reach the sulfate crystals to break them up" is something I'd like to see proven.

From the first article:
step 8  Update:
It's been over a month now and I'm happy to report that my desulfator circuit is working well! My battery now charges to over 13.4 volts after a full charge. Before desulfator treatment it would not rise beyond 12.7 volts.


13.4 is NOT fully charged.  14.5v is.  This after a month on the charger? 
Further, static voltage is of little value if the battery can't take a load.
I can stack AA batteries together to get 15V.  Even brand new, they still won't start your bike let alone a car.

From the HACK-A-DAY
It instead, reverses the process of sulfation returning the lead sulphate to the electrolyte, from whence it came.
This person doesn't know his chemistry.  The acid is H2SO4.  The is no Pb in that formula and putting lead into it instead of on the plates where it came from is NOT resurrecting a battery.

Please post some long term test results that show a sulfated battery being returned to normal service for a year.

Cheers,