Long-term battery charging

[Tim StevensParticipant @timstevens64731]

Advice needed about lead-acid accumulators

[Tim StevensParticipant @timstevens64731]

Is there a battery expert out there?

I am trying to keep my old-car batteries charged over the winter using 'trickle chargers' sold for this specific purpose, but I find in spring that they have let me down. The voltage shown is about 13.5V, and the green light is on, but there is only a 'flash charge' stored, not enough to start an engine. One try on the starter gives a clonk and the volts drop to 9. The battery was new in August.

So, is there a device out there that works properly? Or should I set up a conventional charger on a timer and set it to give, say, an hour at 2A every day? Or what other timing?

Any other advice?

Regards, Tim

PS, perhaps out of scope for some of you, but how about those with battery powered locomotives (etc)?

Edited By Tim Stevens on 12/03/2016 11:19:20

[Harry WilkesParticipant @harrywilkes58467]

The best way i have been told and now use is to very slowly discharge the battery then recharge, I find this works well I connect a small LED light to the battery which takes over 3 months to discharge the battery then recharge. I was told of this many years back by a old timer who looked after the 'battery' dept for a company that had around 120 vehicles, he also told me that you should never leave a battery just standing idle.

H

[korbyParticipant @korby]

If the batt was new last August take it back and claim a new one under guarantee.

[Gordon WParticipant @gordonw]

Not an expert but have been messing for years. You say the battery was new in August, it should have no problem holding a charge, there must be something else wrong, or the battery is dud. Have you checked for leakage ,a light left on or the ignition switch on? Disconnect the charger when not in use in case of faults there. If the battery is old or has been standing unused a long time the best thing is to flatten it , connect a headlight bulb or similar. Then recharge, repeat if required. For interest my tractor battery, now 4 years old, has no problem standing for 6 months and starting a diesel.

[Les Jones 1Participant @lesjones1]

Hi Tim,
As they are old batteries they have probably lost most of their capacity or developed higher than normal internal resistance. You did not say if the 13,5 volt reading was while the battery was on charge or after being disconnected from the charger. If it was after disconnecting it from the charger then the charger is doing its job. If it was while it was still connected to the charger then I think it is slightly low. (I would think 13.8 volts to be a better float charge voltage.) A GOOD battery with a voltage of 13.5 volts while on charge should still start the car easily.

Les.

[Nick WheelerParticipant @nickwheeler]

the basic CTek charger  **LINK**     is what you want. Buy hard-wire kits for each vehicle, charge occasionally and you're done. This is the same charger that Bentley, Ferrari Porsche etc sell with their own badge for people whose toys don't get used enough.

Edited By Nicholas Wheeler 1 on 12/03/2016 11:43:30 bloody smilies!

Edited By Nicholas Wheeler 1 on 12/03/2016 11:43:59

[Stuart BridgerParticipant @stuartbridger82290]

Optimate chargers are great. http://accumate.co.uk/cg020001.htm They are designed both for long term trickle and will recover sulphated batteries. We have one we use for charging 12V batteries for clay pigeon traps. It has recovered batteries that fail to charge on conventional chargers.

[John ShepherdParticipant @johnshepherd38883]

Tim

A 12v lead acid battery needs a charging voltage of at least 13.8v before it starts to charge. If your battery only shows 13.5 v either with the charger connected or soon after it is disconnected, I would suspect your charger is not suitable or is faulty.

Are you able to test the voltage with a separate meter with the charger connected?

Are you able to charge the battery with a high current charger?

If the charging voltage is OK then perhaps the battery is faulty. Lead acid batteries designed for cars thrive on heavy charge and discharge and don't like being trickle charged. One of the chargers mentioned might save the day though and keep your battery in good condition in the future.

Hope that helps

[peak4Participant @peak4]

I know folks who use Optimate chargers for their motorbike batteries and highly recommend them.

I just picked up a couple from Lidl, (though Aldi also have a similar one sometimes) which so a similar job for a fraction of the price.

They seem to do the business for me and go under the name of Ultimate Speed Car battery Charger ULGD 3.8A1

Several different programs depending on the battery type

uTube link HERE, but there's several others on the net

Edited By peak4 on 12/03/2016 13:36:24

[martin perman 1Participant @martinperman1]

Tim,

I tend to agree that there maybe something wrong with your charger, I have two batteries currently on charge with chargers that go to trickle mode when the battery is fully charged and they have been like that since October last year, one has been used on my winch over the winter occasionally but has not suffered.

Martin P

[BazyleParticipant @bazyle]

If it goes clunk it sounds more like a bad battery connection especially earth not the battery. Try measuring the voltage on the battery terminals, not the connectors but the actual lead bits, with the sidelights, then headlights on. It could have been overcharging if the charger is a bit high and with sealed batteries you can't put more electrolyte in.

My spare battery sinks to 12.5 from the alarm drain then I run it up again each week and start the engine, run for a while, which runs the charge at about 14.5, then maybe leave the charger on again for a while.

[Neil WyattModerator @neilwyatt]

I've had two cheap chargers over the years that didn't have enough volts open circuit to fully charge a car battery!

Neil

[Tim StevensParticipant @timstevens64731]

A few added facts:

The battery is not a sealed version, as I know I am going to need to top it up with my three brush dynamo.

The charger is an Accumate 'battery conditioner', not a simple charger. 'Perfect for older vehicles, not used on a daily basis …'

The connections are sound, and after about 15 minutes on traditional charge it turned the starter smartly and started immediately.

The voltage quoted was after disconnecting the Accumate – with it in circuit it read about 13.9V

The voltage was measured at the terminals using copper leads.

I wonder if the 'drop to tick-over' setting within the electronics of the charger is set too low. But my concern is not to spend another £50 or so only to repeat the problem. I am sure that if I send my charger back they will plug it in and say 'It works OK for us' – when it seems to work for me, except after a few months the charge just ain't there. Or if it is, it is hiding …

Cheers, Tim

[jason udallParticipant @jasonudall57142]

My “experience”.
Lead acid batteries don’t seem to like holding a charge when sat on concrete.
Wood.
Plastic
Even the tray in a car.
But floor of the garage..nope

Temperature during charge ..well the terminal voltage falls with temp. Thus the charger if final voltage type will under estimate state of charge.

Fiw..alarm batteries were ( might still be) sla..and these used floatcharge of 13.8 nominal.
…
Float charge should work for you
Btw float charge is defined as C/ 100 in most cases for cars about 0.4A.

[Steven VineParticipant @stevenvine79904]

Over the long years, I've tried many bog standard chargers on car batteries. Often I've ended up killing the battery due to overcharging. Often I have let the battery voltage drop below 12.5v which is a long way to a full discharge (which is around about 10v I think).

I recently bought the CTek MXS 5.0 via Amazon for about £60. It is an intelligent charger and will resurrect a deeply discharged battery. It recovered one of mine from 10v, and the battery is good again.

If the battery plates are 'sulphated' then you won't have enough capacity in there to crank over for long. The Ctek has a Desulphation phase, where it 'Detects sulphated batteries. Pulsing current and voltage, removes sulphate from lead plates of the battery, retsoring the battery capacity.'

I keep 2 car batteries constantly topped up. The Ctek is on continuously providing a floating charge. I swap from one car to the other every week or so. All looks good so far. I'm more confident about this 'intelligent charger' than the standard chargers because it does not wreck the battery.

It charged my deeply discharged 60Ah battery in about 12 hours. It does a SOFT START 5A until 12.6v is reached, then a BULK CHARGE increasing the voltage to 14.4v, then an ABSORPTION phase declining the current at 14.4v, then ANALYSIS phase to check if voltage drops below 12v, then it FLOATS a charge at 13.6v, then PULSES a charge to keep the battery topped up and conditioned. 

 

 

Steve

 

 

 

Edited By Steven Vine on 12/03/2016 16:17:54

[OuBallieParticipant @ouballie]

Just had to replace the battery in my diesel Dobby.

When I mentioned to the AA man, who jumped started me, car that is (to thwart the smart arses ), that the battery indicator was green, he said they are a con as it only meeds one cell to be charged for it to show green, all the others can be dead.

Harry,

Thanks for the hint about discharging via an LED.

Geoff – Progress with the BH600G, but not with the video

[John FieldingParticipant @johnfielding34086]

I am a battery expert and most of the things some people know about batteries is dangerous!

A standard lead-acid battery terminal voltage is nominally 2V per cell. A 12V car battery consists of 6 cells connected in series and hence is nominally 12V. But when fully charged each cell rises to about2.5V maximum. Measuring the open circuit (no load voltage) tells you almost nothing about the battery condition or state of charge. A 12V battery when taken off charge might read 14.0V but after it has stood un connected overnight it will read as little as 12.5V. That is perfectly normal.

In my experience most (not all) of trickle chargers on the market can do more harm than good. In the battery world there are two distinct different types of chargers, cyclic chargers and standby chargers. A car battery is classed as a SLI battery (Starting-Lighting_Ignition) and is designed and made to be float charged by the alternator with a well controlled cut-off voltage. Batteries for caravans which are not charged from the vehicle but charged at home and then used later, are classed as cyclic use batteries, same as fork lift truck batteries. When they are discharged they get put back on charge. It is the same as petrol in your car. When the tank gets low you stick some more in it!

Another type of battery is the traction battery used in golf carts and fork lift trucks, these are also classed as cyclic battery use. They get charged, used to discharge them and put back on charge. Each type of battery uses similar construction and sulphuric acid. They look identical but the subtle difference is the way the plates are made.

In a SLI battery the plates are paper thin, this is to maximise the plate area as thin plates allow more plates to be stacked to give greater area. The next battery is the traction battery which has thicker plates and so less area for the same volume and finally the so-called Deep Cycle batteries which have the thickest plates and so the less area.

The ability to supply high peak currents for short periods is a function of the plate area. SLI batteries have the ability to give high current for short time period. The problem is the thin plates although they allow short bursts of high current, for starting, they cannot give the current for an extended period as the plates overheat and buckle. In automotive applications you only use the top 20 or 30% of the total capacity of the battery during starting and as the engines runs the alternator immediately bangs the charging current back into the battery to top up the tank.

Traction batteries have less ability to give high peak currents but can deliver a moderate current for long periods before they become discharged.

Deep Cycle, or whatever fancy name you choose to call them, have the lowest ability to give high currents. They are designed to give a medium to low current for extended periods, they are not designed to be used as a SLI application.

Now each of these types of battery require slightly different charging methods and cut-off voltages. A typical manufacturers will give details in the data sheet. For example, National Panasonic who supply batteries for just about any application and size or capacity, recommend cyclic use batteries to be charged to 14.0 to 15.0V, whereas for Standby Applications they recommend 13.5 to 13.8V. Standby is also known as float charging and is what car batteries used designed for. The majority of the vehicle current is supplied by the alternator and the battery only has to get involved if the current demand is more than the alternator can handle.

Generally there is no harm in leaving a SLI battery on permanent trickle charge provided the charger is the correct type. One of the other little quirks of lead-acid batteries is the operating temperature. When the battery is very low in temperature its ability to do the chemical reaction is slowed down. It sis the reversible chemical reaction which allws us to discharge a battery and then by putting it on charge to make the chemicals go back to their original state, we call fully charged. Unfortunately the terminal voltage tells us very little of any use. A battery when it is discharged will have a slightly lower voltage than a fully charged – under identical temperature conditions- but that is almost impossible to arrange in simple tests. The one thing we do know is the amount of charge current gives some indication of the state of charge, that is how much of the total capacity we need to replenish to get the battery to 100% charge state. A fully discharged battery if you measure the voltage might be 11V and when you connect the charger you would expect it to draw maximum current. But it doesn't do this for a very simple reason.

Edited By John Fielding on 13/03/2016 08:03:40

[John FieldingParticipant @johnfielding34086]

Seems my post was too long!

The voltaic cell, to give it the correct name, consists of two separate items. They don’t actually exist in a real battery but the standard cell model consists of a voltaic source which can provide current into an external load. In the model this is a constant voltage source that can give infinite current with no drop in the voltage. The theoretical perfect cell. However, the losses incorporated have to be described and the normal method is to include a series resistor that changes its value with the state of charge. We call it an ESR, equivalent series resistance. When the cell is fully charged the ESR is in an ideal cell zero, but as the capacity is depleted the ESR increases, at some point the ESR is too large to allow sufficient current to flow and the output voltage decreases. This explains why the battery voltage drops when a heavy current is drawn.

The lead-acid cell has a reversible chemical reaction. When the cell is fully charged at about 2.5V per cell the chemicals have all been forced into one mode. But as current is drawn off the reaction begins to reverse and as the capacity decreases more of the chemical revert back to the discharged state. We can get a fairly accurate indication of the state of charge by measuring the density of the electrolyte with a hydrometer. A fully charged cell has denser liquid than a discharged cell. Sadly today car batteries are no longer open, so using a hydrometer is no longer possible.

Because the ESR varies with the state of charge then when the battery is fully discharged the ESR is maximum. So when the battery is placed on charge it is difficult to push current into it unless you increase the charger voltage. Batteries when very cold have very high ESR values and when very hot it is much lower. So the charging voltage is very dependent on the battery temperature. So when the charger is first connected the current is quite low. As some of the capacity is gradually replaced the ESR begins to fall and the charging current climbs to some maximum, and at the same time the battery voltages also rises towards the fully charged state. As the battery voltage approaches the charger voltage the ability to push current into the battery gets less and less. When the battery voltage and the charger voltage are the same the charge current is zero. But all lead-acid batteries have an internal loss mechanism and that is why if they are left unused but charged, they slowly lose capacity. So when the battery is nominally fully charged a small “trickle charge” current flows to make up the continual internal loss. Hence, why it is called a trickle charge. So when charging a battery in order to supply the correct charge voltage you have to know the battery temperature and what voltage to apply for that particular battery. There is no “one size fits all” with batteries!

If the charger cut-off voltage is set too high you overcharge the battery and boil off all the electrolyte and the battery is scrap. Again it is very fine line between just the right voltage for those conditions and one that is too high or too low. Chrysler in the 1980s went through a horrible period with "clever battery charging" technology" where they attempted to measure the battery temperature under the hood. Although in principle it was a good move the way they went about it was flawed. The battery sat directly in front of the SBEC computer near the radiator grille. SBEC is short for Single Board Engine Computer and for the first time it integrated all the engine and peripheral electronics onto a single printed circuit board. On the SBEC was a temperature sensor to measure the air temperature flowing into the engine inlet manifold. The SBEC was a box with rubber air hoses at the two ends, the air for the combustion flowed through it after the air filter, so by measuring the air temperature the fuel and ignition could be computed to get the lowest emissions, a good plan but it failed terribly. The whizz-kids at Chrysler tried to make the SBEC do everything that normally individual electronic boxes where dedicated to do.

[John FieldingParticipant @johnfielding34086]

Final part:

One thing was that now they could sort of measure the battery temperature with some degree of accuracy, they could adjust the battery cut-off voltage the alternator supplied to suit the conditions. In North America it gets very cold in winter and batteries when very cold need a much higher charging voltage, similar in blistering hot places like Phoenix, Arizona you need to reduce the charging voltage to prevent overcharging. The Achilles Heel was the tiny temperature sensor was an el cheapo part and they failed by the thousand after a couple of years. A classic case of the bean counters stuffing up an otherwise good design. They replaced a $5 component with a 50c component and in the end lost tens of millions of dollars in warranty claims!

This failure of the sensor meant the engine computer went berserk and buggered up the fuel and ignition timing, so the car ran like a sick dog. That wasn't too serious as the computer had a backup mode called "Limp Home" where the engine was provided with some very basic setting so you could drive it, but not very far!

The biggest problems was the bit of the computer code that did the alternator control, it thought that the car was sitting in an environment of -100C. So it looked up the values you would need to charge the battery at that temperature and discovered it would need 22V and set the alternator to give that output voltage. Of course the batteries either exploded or split the casings and acid corroded everything in the engine compartment and in a few cases the car caught fire. Chrysler had to ditch the SBEC as it lost sales big time with its reliability issues.

[martin perman 1Participant @martinperman1]

John,

That was a very interesting read, thank you.

Martin P

[John FieldingParticipant @johnfielding34086]

Hi Martin,

You're welcome. I was involved with the Chrysler SBEC some years back and it also has some other funny quirks.

In North America in winter cars spend a large portion of the day in traffic queues and when the air temperature is around freezing with an engine warming up you get condensation on the radiator core which turns into a mist. Seems Chrysler got complaints from owners that when waiting at an intersection the steam rising off the radiator had some drivers convinced a hose had a leak. It was normal physical thing like sea fog. So to stop worrying the drivers Chrysler programmed the SBEC to turn on the radiator cooling fan at max rpm to blow the mist away under car. This was despite the fact that engine wasn't anywhere near operating temperature. The end result was increased cylinder wear as the engine never reached its correct temperature. Everyone in ivolved with the SBEC heaved a big sigh of relief when it was finally canned.

[John FieldingParticipant @johnfielding34086]

Another factoid about lead-acid batteries that may interest the readers is the way professional large battery bank chargers are designed. I have been involved in several designs over the years. These batteries are monsters, the smallest bank was 100,000 Ah for a small exchange.

To reach the absolute maximum state of charge requires the final cell voltage to reach about 2.6V. For a 12V battery that is about 15.6V. The charger has several settings, the initial trickle charge to bring the voltage into the range where normal charging can safely take place. This is a current limited supply which raises the battery voltage to around 11V. Thereafter the main charger circuit is enabled and it has the current limited to 1/10 of the battery capacity, so for a 40Ah battery it is programmed to only allow a maximum of 4A to flow. When the battery voltage rises to near the nominal fully charged condition the charger switches to a sort of trickle charge rate of 1/20 of the capacity, so 2A maximum is used for a 40Ah battery. When the battery hits 14.5V the trickle charger voltage is raised to 15.6V and held there for about 30 minutes. This is called the Conditioning Charge Phase. The earlier phases are Trickle, Bulk Charge and Cut-Off Charge.

This last little bit of charge puts the final 5 to 10% capacity into the battery. Then after the timer has elapsed the charger voltage is set to just below the first cut-off voltage at about 13.8V and the trickle current is limited to 1/50 of the capacity.

Charging with this method gets as close to 100% as it is possible to get. So if you examine this method and compare it to the standard alternator system used on cars you can see that you can never get to 100% capacity. The best you can achieve is about 90%, but that is OK for most cars.

In large battery bank installations I have been involved with the design we always had temperature sensor inputs to modify the charging voltages. But these battery banks were designed for a minimum life of 15 years for telephone exchanges where if the mains fails they must continue to run for at least 8 hours. So no expense is spared to maximise the capacity and life of the cells.

[OuBallieParticipant @ouballie]

Oops, double post.

Contents deleted.

Geoff – Sorry.

Edited By OuBallie on 13/03/2016 10:09:13

[John FieldingParticipant @johnfielding34086]

Forgot to mention another pointer.

If you google a US company called Deltran they have some very comprehensive papers and other facts about battery charging. I have used their products and they are, in my opinion, one of the top companies in this market. The engineers there are real experts in their subject.

[Author]

Posts