Lead acid battery charging
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Lead acid battery charging
Could someone explain to me why do lead acid batteries as used on cars and aeroplanes need to be charged at certain current values and say fixed voltage 14.1V, and you have to be careful not to overcharge, yet when connected to a vehicle there is no charge regulation?
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Hello BigEndBob
High charging currents or cell voltages (higher 2.4 V) cause gassing. The distilled water splits into hydrogen and oxygen. This oxy-hydrogen is, of course, highly explosive.
As far as I know, this effect applies to all lead-acid accumulators including those in cars.
Best regards
hvogt
High charging currents or cell voltages (higher 2.4 V) cause gassing. The distilled water splits into hydrogen and oxygen. This oxy-hydrogen is, of course, highly explosive.
As far as I know, this effect applies to all lead-acid accumulators including those in cars.
Best regards
hvogt
Last edited by hvogt; 15th May 2008 at 16:12.
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Lead Acid batteries are usually charged at a constant voltage but generally there is no need to control the current. The current during the charge is typically controlled by the charge state of the battery. It starts off high and falls as the battery charges. So there is a form of regulation.
Having said that.. It is normal for the charger to have a current limit which comes into play at the start of the charge cycle when the battery is flat. The current at the end of the charge is controlled by the voltage which needs to be quite accurate. If the voltage and consequently the current is too high at the end then gassing occurs for the reason hvogt gives.
With certain conditions Lead Acid batteries can actually be left on charge permanantly. This is called float charging and is usually done at a slightly lower voltage than normal to ensure the final current is quite low and minimise gassing that would dry out the cell. Typically on float the current will fall to close to zero - just balancing the self discharge losses. In fact wet Lead acid batteries seem to last longer if kept permanantly on a correctly set up float charger. They typically hate being deep discharged, allowed to self discharge or allowed to stand flat for even quite short periods. This applies even to wet cells designed for deep discharge.
I've flown electric powered model planes for 20 years and in my first few seasons I managed to kill three lead acid batteries a year by allowing them to stand party discharged for too long. Now as soon as I get back from a days flying the battery is put on float charge immediatly and is left like that 24/7. Now the battery lasts several years.
I highly recommend using a charger with a float setting if you have a battery powered lawn mower that uses wet lead acid batteries. Keep it on float over winter. Sometimes the float voltage can be adjusted to match that recommended by the battery manufacturer.
Having said that.. It is normal for the charger to have a current limit which comes into play at the start of the charge cycle when the battery is flat. The current at the end of the charge is controlled by the voltage which needs to be quite accurate. If the voltage and consequently the current is too high at the end then gassing occurs for the reason hvogt gives.
With certain conditions Lead Acid batteries can actually be left on charge permanantly. This is called float charging and is usually done at a slightly lower voltage than normal to ensure the final current is quite low and minimise gassing that would dry out the cell. Typically on float the current will fall to close to zero - just balancing the self discharge losses. In fact wet Lead acid batteries seem to last longer if kept permanantly on a correctly set up float charger. They typically hate being deep discharged, allowed to self discharge or allowed to stand flat for even quite short periods. This applies even to wet cells designed for deep discharge.
I've flown electric powered model planes for 20 years and in my first few seasons I managed to kill three lead acid batteries a year by allowing them to stand party discharged for too long. Now as soon as I get back from a days flying the battery is put on float charge immediatly and is left like that 24/7. Now the battery lasts several years.
I highly recommend using a charger with a float setting if you have a battery powered lawn mower that uses wet lead acid batteries. Keep it on float over winter. Sometimes the float voltage can be adjusted to match that recommended by the battery manufacturer.
Could someone explain to me why do lead acid batteries as used on cars and aeroplanes need to be charged at certain current values and say fixed voltage 14.1V, and you have to be careful not to overcharge, yet when connected to a vehicle there is no charge regulation?
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In addition...
The lead acid batteries used in aeroplanes are not as robustly constructed as those used in motor cars, so the charging circuit in airplanes account for this by tightly regulating the charge current.
Too much is....not good.
As pointed out, these batteries do not like being deeply discharged, and if this is allowed to happen, the battery life can (and will) be severely compromised.
The lead acid batteries used in aeroplanes are not as robustly constructed as those used in motor cars, so the charging circuit in airplanes account for this by tightly regulating the charge current.
Too much is....not good.
As pointed out, these batteries do not like being deeply discharged, and if this is allowed to happen, the battery life can (and will) be severely compromised.
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Originally Posted by me
the charging system is a one-size-fits-all-climates solution
"Smart Charging, a battery current control feature driven by the engine electronic control module monitors the charge state of the battery, and can adjust or interrupt current flow into the battery. By keeping the charge of the battery within an optimal range, Smart Charging reduces the average battery temperature and contributes greatly to the battery's life span. The system also facilitates precise idle control, and even raises the idle speed to prevent battery drain in winter conditions and in other instances of high current demand."
Yay for clever use of the ECM. This was from a paper describing the Duratec HE which also has such neat features as an electronic thermostat.
Last edited by skiingman; 12th Jul 2007 at 20:11.
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Thanks for the information.
Just looking into batteries and charging for use in Motorhomes.
Lots of info. on the net, but nothing like practical experience.
Doing a few experiments with a Concorde battery given to me from work.
I know its not a 'Leisure' battery but just seeing what happens.
At moment using it to drive a Philips 20W (100W equivilent) low energy bulb through a 150w inverter. According to a plug in meter its drawing 16W at 2Amp. Its a 25a/hr battery. Just want to see how long it lasts.
If such a battery was connected in parallel to car battery would it charge ok.
As i suspect a car alternator only ok for replacing whats used by starting.
But if i alternated between two batteries long before they became significantly discharged then they could be used, just a thought.
Just looking into batteries and charging for use in Motorhomes.
Lots of info. on the net, but nothing like practical experience.
Doing a few experiments with a Concorde battery given to me from work.
I know its not a 'Leisure' battery but just seeing what happens.
At moment using it to drive a Philips 20W (100W equivilent) low energy bulb through a 150w inverter. According to a plug in meter its drawing 16W at 2Amp. Its a 25a/hr battery. Just want to see how long it lasts.
If such a battery was connected in parallel to car battery would it charge ok.
As i suspect a car alternator only ok for replacing whats used by starting.
But if i alternated between two batteries long before they became significantly discharged then they could be used, just a thought.
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Just looking into batteries and charging for use in Motorhomes
Leisure batteries are slight different design to car battery to allow for deeper discharge/recovery when using lower currents for appliances.
AustralianMade
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Hi BEB,
If you fit a proper dual battery management system, that includes an automatic battery charge switching devise, your cars alternator is more than capable of charging an extra battery or even batteries. My car has a dual battery system installed and I normally charge the main (starting) battery and the second battery and occasionally, on trips, charge a third as well, all automatically and all without hassle.
A dual battery management system generally works like this:
After starting your car the system will automatically charge your main battery - the battery that started the car - until its voltage is around 13.6 volts (mine is a 12V system, 24V systems are available), then the system will charge the secondary battery until it is also at 13.6V at which point the system will maintain charge in both batteries until the engine is switched off.
The system, if installed properly, will always separate the main battery from the secondary battery during the discharge phase. The main will be left undischarged and ready to do its only job - start your car - the secondary will be discharged by the accessory loads that you place on it, such as the light you mentioned, or in the case of one large motor home I fitted out in 2003, the secondaries will power your laptop, fridge, microwave, lights, fans and air conditioning system!
To achieve this, make sure that when you install the secondary battery, the wiring for the starter motor remains on the main battery and the rest of the wiring and subsequent wiring goes on the secondary.
This will prevent you being stuck in a lonely place with a discharged main, as well as a discharged secondary.
All this is from my own experience as manager of Battery World here in my home town. (Mods, this is not an advert, as the business was sold after my departure and closed down sometime later.)
SLI batteries (Starting, Lighting & Ignition) do not like to be discharged to below about 80% of their full charge, roughly equivalent to the drain caused by starting the car two or three times in quick succession. If they are drained below this their useful service life is diminished dramatically, every time this happens, firstly, following a deep discharge of an SLI battery, you will never get it fully charged to 100% of the charge state before the discharge, secondly, SLI batteries suffer dramatically from sulphation when discharged. Simply put sulphation causes the lead to flake off the plates and collect in the mud racks in the bottom of the battery where it does more harm than good.
For a camping application you need a Deep Cycle battery. Deep cycle batteries have thicker plates and slightly different internal wiring, the thicker plates give the battery more 'voltage holding power' and resist sulphation much longer than SLI batteries.
The best type of deep cycle battery has only ONE plate per cell, this plate is about 6 feet long and rolled into a spiral, with fiberglass between the roll to prevent shorting but allow electrolyte flow. Spiral batteries resist vibration extremely well and have more lead for a given volume that plate rack batteries.
We never had a single battery present for a warranty claim with Optima batteries.
Just another disclaimer for the mods, I no longer have anything to sell, I left the industry in November 2006 and am now labouring for a mate of mine who owns a landscaping company while I get through my ab initio flying training.
This started out as quick reply and turned into an essay, but I hope it helps.
Cheers,
ABX
As i suspect a car alternator only ok for replacing whats used by starting.
A dual battery management system generally works like this:
After starting your car the system will automatically charge your main battery - the battery that started the car - until its voltage is around 13.6 volts (mine is a 12V system, 24V systems are available), then the system will charge the secondary battery until it is also at 13.6V at which point the system will maintain charge in both batteries until the engine is switched off.
The system, if installed properly, will always separate the main battery from the secondary battery during the discharge phase. The main will be left undischarged and ready to do its only job - start your car - the secondary will be discharged by the accessory loads that you place on it, such as the light you mentioned, or in the case of one large motor home I fitted out in 2003, the secondaries will power your laptop, fridge, microwave, lights, fans and air conditioning system!
To achieve this, make sure that when you install the secondary battery, the wiring for the starter motor remains on the main battery and the rest of the wiring and subsequent wiring goes on the secondary.
This will prevent you being stuck in a lonely place with a discharged main, as well as a discharged secondary.
All this is from my own experience as manager of Battery World here in my home town. (Mods, this is not an advert, as the business was sold after my departure and closed down sometime later.)
SLI batteries (Starting, Lighting & Ignition) do not like to be discharged to below about 80% of their full charge, roughly equivalent to the drain caused by starting the car two or three times in quick succession. If they are drained below this their useful service life is diminished dramatically, every time this happens, firstly, following a deep discharge of an SLI battery, you will never get it fully charged to 100% of the charge state before the discharge, secondly, SLI batteries suffer dramatically from sulphation when discharged. Simply put sulphation causes the lead to flake off the plates and collect in the mud racks in the bottom of the battery where it does more harm than good.
For a camping application you need a Deep Cycle battery. Deep cycle batteries have thicker plates and slightly different internal wiring, the thicker plates give the battery more 'voltage holding power' and resist sulphation much longer than SLI batteries.
The best type of deep cycle battery has only ONE plate per cell, this plate is about 6 feet long and rolled into a spiral, with fiberglass between the roll to prevent shorting but allow electrolyte flow. Spiral batteries resist vibration extremely well and have more lead for a given volume that plate rack batteries.
We never had a single battery present for a warranty claim with Optima batteries.
Just another disclaimer for the mods, I no longer have anything to sell, I left the industry in November 2006 and am now labouring for a mate of mine who owns a landscaping company while I get through my ab initio flying training.
This started out as quick reply and turned into an essay, but I hope it helps.
Cheers,
ABX
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ABX. Please don't apologise for your comprehensive answer. Arguably, you have created a Forum standard reference work to everyone's benefit. An additional question from myself, if I may: are there any special care points in relation to gel batteries?
AustralianMade
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Thanks GBZ, although I'm not sure about the forum reference stuff.
Gel batteries mainly differ in one key point, but before I get to that, I'll cap the standard care:
1) All batteries like to maintain a high state of charge, no battery benefits by being discharged, especially for prolonged periods of time.
2) Keep the terminals clean to prevent corrosion. (much less of a problem with gel).
3) Take care not to overcharge your battery. All batteries have an inbuilt upper limit for both charge voltage and charge amperage, exceeding either may heat up the battery and cause a loss of water from the electrolyte. In this example 'over charging' does not refer to the length of time a battery is charged as the battery will self regulate its own charging - if the charging system is within manufacturers specifications - simply by accepting less and less charge as it nears its charge capacity.
This is the area where gel batteries differ from standard lead acid batteries. Most gel batteries are sealed, given that they are designed to fit into places and positions that cannot tolerate acid spillage, one good example is the gel (or Sealed Lead Acid <SLA>) batteries commonly found in those electric shopping carts that the elderly use to terrorize the rest of us pedestrians. When over charged gel batteries, along with any type of sealed battery, will heat up and cause high internal pressure, due to heat and vaporisation of electrolyte - be it gel or not - which often causes either the hard outer case of the battery to soften and expand or simply burst.
When I was manager of Battery World I always kept just such an example on my counter top as a visual reminder to customers not to over charge, one of my counter top batteries had, due to the conditions described above, expanded to roughly basketball size and shape, having started out half the size and square, another example on my counter top was two batteries installed in a uninterrupted power supply (UPS) that provided power to a business computer system, due to a charger malfunction these two batteries had been over charged, distorted considerably and fused together.
Needless to say the batteries on my counter top generated much discussion with our customers!
Short answer to your question GBZ, use them in the manner they were designed for and be particular that you don't over charge and it should be fine.
Cheers mate.
Gel batteries mainly differ in one key point, but before I get to that, I'll cap the standard care:
1) All batteries like to maintain a high state of charge, no battery benefits by being discharged, especially for prolonged periods of time.
2) Keep the terminals clean to prevent corrosion. (much less of a problem with gel).
3) Take care not to overcharge your battery. All batteries have an inbuilt upper limit for both charge voltage and charge amperage, exceeding either may heat up the battery and cause a loss of water from the electrolyte. In this example 'over charging' does not refer to the length of time a battery is charged as the battery will self regulate its own charging - if the charging system is within manufacturers specifications - simply by accepting less and less charge as it nears its charge capacity.
This is the area where gel batteries differ from standard lead acid batteries. Most gel batteries are sealed, given that they are designed to fit into places and positions that cannot tolerate acid spillage, one good example is the gel (or Sealed Lead Acid <SLA>) batteries commonly found in those electric shopping carts that the elderly use to terrorize the rest of us pedestrians. When over charged gel batteries, along with any type of sealed battery, will heat up and cause high internal pressure, due to heat and vaporisation of electrolyte - be it gel or not - which often causes either the hard outer case of the battery to soften and expand or simply burst.
When I was manager of Battery World I always kept just such an example on my counter top as a visual reminder to customers not to over charge, one of my counter top batteries had, due to the conditions described above, expanded to roughly basketball size and shape, having started out half the size and square, another example on my counter top was two batteries installed in a uninterrupted power supply (UPS) that provided power to a business computer system, due to a charger malfunction these two batteries had been over charged, distorted considerably and fused together.
Needless to say the batteries on my counter top generated much discussion with our customers!
Short answer to your question GBZ, use them in the manner they were designed for and be particular that you don't over charge and it should be fine.
Cheers mate.
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ABX - Just slightly off topic...... As I recall NiCad batteries in aircraft (AS350 for one), as part of their maintenance, require discharging to 0 volts and then are left for some period with a shorting strip across the terminals. What is the science/reason behind that?
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Warm Ballast, I like that name mate "warm ballast". I'm guessing that's another name for SLF?
Nickle Cadmium (NCD or NiCad) batteries are different to all other battery types, including others that appear similar such as Nickle Metal Hydride (NMH) and Lithium Ion (LI or L-Ion).
I am a bit thin in regards to the actual science behind the reason, however:
The reason that NiCad batteries need to be discharged fully and then recharged fully is because the battery has a tendency to 'remember' its most recent state of charge. This state of 'memory' reduces the batteries capacity to hold charge, a condition that gets worse every time the battery is cycled (charged - discharged - charged) without being fully discharged. I have often witnessed this cumulative effect halving a NiCad batteries holding capacity even though the battery charger indicates it is fully charged.
There are special machines that will cycle NiCad batteries from fully charged to deeply discharged over and over again - over a two or three day period for example - which has the effect of 'breaking down or breaking through' this memory effect and restoring all but a fraction of the original capacity.
As for the actual science, I believe that it is something to do with an incomplete chemical reaction within the battery that accumulates over time, but all of my reading/learning/research on the topic was to do with the effect, its causes and its cures, not the actual science.
NiCad batteries shouldn't be charged if only half discharged, whereas NMH & L-Ion batteries can be 'topped up' when only partially discharged without a problem.
Cheers,
ABX
Nickle Cadmium (NCD or NiCad) batteries are different to all other battery types, including others that appear similar such as Nickle Metal Hydride (NMH) and Lithium Ion (LI or L-Ion).
I am a bit thin in regards to the actual science behind the reason, however:
The reason that NiCad batteries need to be discharged fully and then recharged fully is because the battery has a tendency to 'remember' its most recent state of charge. This state of 'memory' reduces the batteries capacity to hold charge, a condition that gets worse every time the battery is cycled (charged - discharged - charged) without being fully discharged. I have often witnessed this cumulative effect halving a NiCad batteries holding capacity even though the battery charger indicates it is fully charged.
There are special machines that will cycle NiCad batteries from fully charged to deeply discharged over and over again - over a two or three day period for example - which has the effect of 'breaking down or breaking through' this memory effect and restoring all but a fraction of the original capacity.
As for the actual science, I believe that it is something to do with an incomplete chemical reaction within the battery that accumulates over time, but all of my reading/learning/research on the topic was to do with the effect, its causes and its cures, not the actual science.
NiCad batteries shouldn't be charged if only half discharged, whereas NMH & L-Ion batteries can be 'topped up' when only partially discharged without a problem.
Cheers,
ABX
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ABX - Thanks for that. I understood - to a point - NiCad's 'memory' problems, but to totally short a battery for ages seemed weird.
WB name? Well I do self load and kind of move around, hang out of and around lots of different Aircraft...... and no I don't jump out of them .....
WB name? Well I do self load and kind of move around, hang out of and around lots of different Aircraft...... and no I don't jump out of them .....