12V leisure battery help

[choochoo_baloo]

I bought a 12V dc leisure battery last summer for running astronomy gear. It was used a few times in the autumn, not at all over the winter (busy with another project), then a number of times during this month. Between September last year and May this year, it has been sat on the concrete floor of the (uninsulated) garage.

I'd like to ask for some accurate advice on proper care of & recharging of this type of battery. I've attached photos of the front and back of it if that helps. The retailer (a local battery supplier for automotive, leisure batteries etc.) wasn't very clear on what to do. So I'd like to ask people who know what they're talking about! My questions:

• How do I calculate the % charge remaining using a multimeter?
• As the rear photo shows, a recharge is due 06.2015 ie now. Is this date stated with reference to when the battery was fully charged upon leaving the factory? How can a fixed recharge date be stated - surely this will depend solely on the amount of usage?!
• The shopkeeper did say that the battery should be fully drained ie used, before a full recharge. Is this correct - is this how to look after this type of battery?
• What mains charger do I need to charge it (the battery didn't come with any instructions)?

Thanks for any help in advance. Apologies also for what are probably quite basic questions! 

[Physopto]

It is simple really!

A lead acid battery is best charged with a multi stage intelligent charger. You can do it anytime, say once a month or every two weeks. The battery is fully charged at 14.4 volts whilst connected to the active charger. Once disconnected from the charger, it will dissipate its surface charge over a 24 hour period and the voltage will drop to about 12.8 volts. It is still fully charged at that voltage. Over a period of time if left without touching its voltage will drop due to internal discharge (internal resistance). So fully charged is 12.8 volts, half charge is 12.4 volts and fully discharged is 10.6 volts. This is because the charge/discharge graph is a shape like you holding a water hose horizontally, the water drops off in a curve to the ground, so does a lead acid batteries discharge. It is never advisable to let any lead acid battery discharge more than a small amount but obviously you need to use it. Try to let it go no further than say half (12.4 volts) before recharging. A lead acid battery depending upon make will usually loose about 2 to 3% of its charge per month whilst not being used, some even more. As the battery gets older the lead plates start to loose their active paste filling and it drops down to the bottom of the battery. Eventually it starts to short out the cells and the battery is then at the end of its life. No amount of charging will bring it back.

It is very important to know that as a battery is charged and the voltage rises it out gases Hydrogen gas. It depends upon charge rate and voltage. If the battery is at a low (discharged state) it voltage will increase up to a point where out gassing starts. This happens at about 13.5/6 volts (not written in stone remember charge rate). After that it will release Hydrogen. No naked lights near the battery whilst charging!!!!!! This includes not switching on or off any electrical gear or lights in the vicinity. The battery should be only charged in a well, ----well ventilated space!

An intelligent type charger is the best way of looking after a battery, there are several makes, but I use CTEK. They are shower proof to some extent and if used properly can be left connected to the battery all the time. Almost any size battery charger will charge a battery. You do not need a large capacity charger. A 5A hour charger will charge up a 110 AH battery just as well as a 10 AH charger. It will just take longer. But it is good practice to at least try to match up the charging rates. So a rule of thumb is to rate your charger at about 10% of the battery at the most. I.e. 5A hour charger for a 50 AH battery, no more. Overcharging or too fast charging will damage the plates inside the battery. They heat up and become distorted causing the paste filling to dislodge.

The recharge date you mention is of little use. It is only there for guidance. Remember the self discharge, it can vary. Always check the voltage with a multi meter, before connecting to a charger. Always use the battery terminal post covers whilst in storage to prevent accidental shorts. Never lay tools on top of a battery whilst working. Keep wires away from the terminals unless connecting up. Never short out the battery connection leads, I.e. Connect to the battery after all else is ready. Fit a fuse of the correct rating to protect your equipment. Lastly NEVER lean over a battery when connecting to it for any reason. If it does explode the top comes off first!!

Use common sense and it should last you well.

Derek

[Dave grim]

When I was looking at leisure batteries for the same reason as you I seem to remember that dc or deep cycle leisure batteries are supposed to be fully discharged before charging again otherwise their lives are considerably shortened , hope that helps

Dave

[Scott]

I use one of these and leave it on charge when not in use. I'm told it won't harm the battery and it's working fine 2 yrs down the track

[choochoo_baloo]

Thanks all for the information.

[choochoo_baloo]

It is simple really!

A lead acid battery is best charged with a multi stage intelligent charger. You can do it anytime, say once a month or every two weeks. The battery is fully charged at 14.4 volts whilst connected to the active charger. Once disconnected from the charger, it will dissipate its surface charge over a 24 hour period and the voltage will drop to about 12.8 volts. It is still fully charged at that voltage. Over a period of time if left without touching its voltage will drop due to internal discharge (internal resistance). So fully charged is 12.8 volts, half charge is 12.4 volts and fully discharged is 10.6 volts. This is because the charge/discharge graph is a shape like you holding a water hose horizontally, the water drops off in a curve to the ground, so does a lead acid batteries discharge. It is never advisable to let any lead acid battery discharge more than a small amount but obviously you need to use it. Try to let it go no further than say half (12.4 volts) before recharging. A lead acid battery depending upon make will usually loose about 2 to 3% of its charge per month whilst not being used, some even more. As the battery gets older the lead plates start to loose their active paste filling and it drops down to the bottom of the battery. Eventually it starts to short out the cells and the battery is then at the end of its life. No amount of charging will bring it back.

It is very important to know that as a battery is charged and the voltage rises it out gases Hydrogen gas. It depends upon charge rate and voltage. If the battery is at a low (discharged state) it voltage will increase up to a point where out gassing starts. This happens at about 13.5/6 volts (not written in stone remember charge rate). After that it will release Hydrogen. No naked lights near the battery whilst charging!!!!!! This includes not switching on or off any electrical gear or lights in the vicinity. The battery should be only charged in a well, ----well ventilated space!

An intelligent type charger is the best way of looking after a battery, there are several makes, but I use CTEK. They are shower proof to some extent and if used properly can be left connected to the battery all the time. Almost any size battery charger will charge a battery. You do not need a large capacity charger. A 5A hour charger will charge up a 110 AH battery just as well as a 10 AH charger. It will just take longer. But it is good practice to at least try to match up the charging rates. So a rule of thumb is to rate your charger at about 10% of the battery at the most. I.e. 5A hour charger for a 50 AH battery, no more. Overcharging or too fast charging will damage the plates inside the battery. They heat up and become distorted causing the paste filling to dislodge.

The recharge date you mention is of little use. It is only there for guidance. Remember the self discharge, it can vary. Always check the voltage with a multi meter, before connecting to a charger. Always use the battery terminal post covers whilst in storage to prevent accidental shorts. Never lay tools on top of a battery whilst working. Keep wires away from the terminals unless connecting up. Never short out the battery connection leads, I.e. Connect to the battery after all else is ready. Fit a fuse of the correct rating to protect your equipment. Lastly NEVER lean over a battery when connecting to it for any reason. If it does explode the top comes off first!!

Use common sense and it should last you well.

Derek

Very informative, and exactly the detail I was hoping for. Thanks for taking the time to write this.

[rob0971]

I use one of these and leave it on charge when not in use. I'm told it won't harm the battery and it's working fine 2 yrs down the track

Thats the same  one i use on my leisure battery. I also leave it attached when not in use. Not sure about the full discharge, I always charge up after use whether its discharged or not. its been fine.

[Physopto]

When I was looking at leisure batteries for the same reason as you I seem to remember that dc or deep cycle leisure batteries are supposed to be fully discharged before charging again otherwise their lives are considerably shortened , hope that helps

Dave

Hi Dave,

Who ever told you that you could do that is sadly mistaken. Any lead acid battery is only at its best when fully charged.  Car batteries are made specifically to give out high amperage  for a short period and then immediately be recharged by the car / vehicle alternator. If not they will very soon be irreversibly damaged. Leisure batteries on the other hand are engineered top tolerate partial discharge and some times a bit more. They will recover better than a standard starter battery, but will still be damaged if left partially discharged or even worse fully discharged. Every discharge cycle will reduce the lifetime of the battery. It is far better and certainly more economical to keep the battery fully charged at all times.  I know that for us especially this is not always possible, in the field etc.,

But the sooner it is recharged the better. There are many charts showing  number of discharge cycles for batteries on the WEB and expected life times. All show the same thing the deeper the discharge the shorter the lifetime of the battery.

The only batteries that will tolerate these very low discharge cycles and recover are the LiFePo type and are extremely expensive. Their discharge graph is almost flat until the battery is nearly empty when there is a sudden voltage drop. They can tolerate  anything from 1500 up to 2000 recharge cycles, before they are useless for further service.  They also require a specialized charger.  They require a constant current charge until about 80/90% charged then they switch over to constant voltage to finish, otherwise they will be damaged.

Some years ago laptop Lithium batteries (Not LiFePo) were introduced. These were at that time fully charged, when connected to the mains via their chargers. Most companies soon realised that this was detrimental to the Lithium batteries. They then started charging the batteries to only 80%. this then gave a longer life time expectancy to the laptop batteries. This depends upon the exact battery make, by that I mean its exact chemical composition. There are several types of Lithium battery.

Hope this clears up any misunderstandings.

Finally temperature plays a major role in battery charging. Too cold is not good and too hot is also not good.

A very cold lead acid battery will produce a heck of a lot less current. A very hot battery will be damaged under high discharge rates if for more than a very short burst, (its internal temperature rises and the plates are easily distorted/buckled causing paste dropout.).

So to reiterate please ensure a lead acid type battery is kept charged to close to 100% as much of the time as possible and it will last you far longer.

Derek