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Undercharging lead acid starter batteries

Undercharging lead acid starter batteries

Undercharging lead acid starter batteries

(OP)
Hi,

I have three vehicles that very rarely are used for long runs. This means that in general the batteries are under-charged.
I would expect 12.8v at rest from a fully charged battery in good condition. Mine are more like 12.2v. What I have noticed is that when the vehicle is started up and the alternator supplies current to the battery, the voltage rises very rapidly to 14.4v, so presumably there's little point at this stage of giving the batteries a long charge via the alternator. Unfortunately I don't have a good battery to use for comparison - would a good battery take time to gradually rise to 14.4v when the alternator is supplying current?

At the moment I am experimenting with applying a re-conditioning charge to one of the batteries to see if it will result in removing some of the sulfation and hopefully increase the resting voltage / capacity. I'm using a smart charger, and the rising voltage from 14.4 - 15.5v seemed to take a little while so am hoping it's having some effect. The resting voltage several hours after reconditioning charge was 12.5v as opposed to less than 12v, which it was after cranking the engine and failing to start (didn't take a reading before). How many reconditioning charges can I apply without risking damage to the battery?

RE: Undercharging lead acid starter batteries

What is the age of these batteries? It doesn't sound like your batteries are in good condition.

RE: Undercharging lead acid starter batteries

(OP)
Oldest (the one I'm trying to recondition) is 3 years. Other two are two years and one year - and yes, the performance in each case is worse with age, so the newest one takes more of a charge and is more likely to have enough voltage to start the vehicle.

RE: Undercharging lead acid starter batteries

Have you checked the electrolyte? Both level and S.G.?
After a re-cond charge you may need to re-freshen the acid.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Undercharging lead acid starter batteries

(OP)
Electrolyte levels are fine. When you say re-freshen the acid, I presume you mean top up with distilled water to compensate for evaporation due to the high charge? Haven't checked the SG as yet...

RE: Undercharging lead acid starter batteries

3 years is a very short life expectancy unless they are stored in a very hot region. It's certainly not outside of reason to have that short of a life, though. We get 2 years on our generator starting batteries because they alternator keeps them juiced at 14.5 volts for thousands of hours every year.

On the opposite end of the spectrum, if the batteries are left without charger and voltage drops then the sulfation begins.

How short are these runs and how often are the vehicles used? A single start of an engine in good condition that doesn't require preheat hardly puts a dent in the state of charge. It should only take a few minutes to bring the battery up to charge.

RE: Undercharging lead acid starter batteries

Yes I was referring to the acid concentration.
While voltage will be lower in a cold battery it is heat that causes damage.
I would expect something closer to 5yr with reasonable care.
Sounds like a place for battery tenders.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Undercharging lead acid starter batteries

...speaking of battery tenders, not knowing any better I've been using the sub $20 "float chargers" you get on Amazon or anywhere, for many years, with apparently good results. I.e. not only my lawnmower battery is on its 4th or 5th year I believe, and while I don't know the age of the batteries of two of my cars acquired secondhand, one is over 7 years old and another at least 3, and both are going strong. I should mention that these vehicles are used seasonally, then parked 3-6 months at a time, with the cheapo float charger connected.
So, what's the downside of these el-cheapo float chargers?

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

RE: Undercharging lead acid starter batteries

Well, the cheap ones have been known to either die or over charge unexpectedly. But this is fairly rare.
If they work keep it up.
They are low enough current that they should not cause damage to the batteries.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Undercharging lead acid starter batteries

(OP)
Hey all...

I think I may have discovered the root cause of my problem. There is a draw of 0.2A on the battery even when the ignition is turned off. I've read online briefly that this may be caused by a defective alternator diode, which apparently means that the battery is left trying to charge itself... electrically speaking this would be a partial short circuit I suppose.

For now, I'm just disconnecting the battery while not in use, but unfortunately the battery itself is in its last days as extended periods in a discharged or partially discharged state over its three year life have done the damage.

RE: Undercharging lead acid starter batteries

Regarding recharging auto batteries: When the voltage rises to 14.4v right after the engine starts, it's the alternator doing that. The alternator can produce a tremendous amount of electrical potential - way more than the 12 or so volts in the battery. That's so the battery charges.

As the battery charges up, the voltage output of the alternator also rises - according to Ohm's law: V = IR

If the system isn't doing that, there's something wrong - and that can be used to diagnose a bad battery.

RE: Undercharging lead acid starter batteries

Quote (CapriRacer)

As the battery charges up, the voltage output of the alternator also rises - according to Ohm's law: V = IR
Not Ohm's law. The alternator has a regulator that is the primary controller of voltage.

je suis charlie

RE: Undercharging lead acid starter batteries

If I measure "battery voltage" at the cigarette lighter the results are almost always .1 - .4 below what I'd measure directly on the bat terminals. The worst were my old Renault 16s.

RE: Undercharging lead acid starter batteries

You didn't say what year the vehicles are. ALL modern vehicle have horrendous ignition-off loads constantly stripping off the full charge from the alternator and then dragging the voltage down over time. You will be lucky to have a new car start after a month sitting. I've seen many that have problems after two weeks.

Normally I'd say put in a Perko switch and turn off the battery entirely if you know you aren't going to use the vehicle in a week or so. Unfortunately, the scummy car makers are too cheap to put non-volatile memory into the vehicle's ECM units and if you disconnect the battery the ECM forgets all of its self tuning and the engine will run poorly for about three cold starting cycles.

The easiest solution that avoids the ECM memory issue is to get a solar-cigarette-lighter type charger and toss the panel on the dash so every time the sun's out your battery is charging.

Allowing batteries to drop below 12.8V is definitely allowing the sulfination process to gain more ground on stealing away the battery's capacity. Kept at 12.2V I'd expect an LA battery to easily lose two or three years a year.

Way back the insidious vampire was the TICK TICK TICKing dash clock. It would kill the battery in a month or so. We'd always unplug the clock then we'd only have the 6% / month LA self discharge to worry about.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Undercharging lead acid starter batteries

Talking about battery's how often should a low use electric forklift be charged? Month and a half? I have not seen such thing as a trickle charger for forklifts, only high amp fast chargers.

RE: Undercharging lead acid starter batteries

The dedicated forklift chargers should have a charge controller. They charge at a high rate and then float the battery. Any decent quality charger should have that capability.

RE: Undercharging lead acid starter batteries

I'd plug the charger to the forklift and run it every two weeks. If you truly don't drive it for lonnnng periods and your charger automatically charges without button pushing I'd think about installing a time clock and have the charger go on once a week for whatever time is enough to get the charger into the float state.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Undercharging lead acid starter batteries

Quote (enginesrus)

Talking about battery's how often should a low use electric forklift be charged? Month and a half? I have not seen such thing as a trickle charger for forklifts, only high amp fast chargers.

Flooded cell battery of the type used in forklift batteries can suffer from acid stratification where the acid / water concentration is not the same throughout the battery's height. The accepted method to deal with this is to belt it with a charger, as the overcharging and gas production effectively remixes the electrolyte, at the penalty of some gas emission and water loss. For this reason equipment that uses traction batteries often also provides a water top up facility.

RE: Undercharging lead acid starter batteries

They have battery chargers that 'rejuvinate' undercharged batteries and if they are in reasonable condition they can be brought back up to slightly less than new condition.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

RE: Undercharging lead acid starter batteries

That might work for heavy duty batteries but my experience with automotive batteries is that the damage done is quite mechanical. The corrosion causes the plates to disintegrate and sulfation causes the case to bulge.

RE: Undercharging lead acid starter batteries

Modern mass production automotive batteries are designed very exactly to their designed use cases. So the basic assumption is they'll never go flat, not be needed to churn the engine over for half a minute, will get charged up immediately after starting, etc. That's why they cost so little, but also why they are not robust once you mistreat them, and don't last forever.

Cheers

Greg Locock


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