What voltage should I recharge my battery at

[muckington]

13.8v to maintain it in a charged state, 14.4v to charge it. Don't discharge it more than 50% of it's capacity, it will quickly ruin it, and never leave it in a discharged condition, ever - recharge, as soon as it has been used.

Some one said about that 50% would be about 12.8V

 

[ebee]

With Burglar Alarm Systems etc the SLA battery is usually recommended on constant float charge of 13.6 Volts to 13.8 Volts if that helps, one common very simple way is to use a 12V Reg IC and three forward biased diodes on the -ve leg and one of those diodes has a shorting link soldered across it there as it comes two diodes drop around 0.6 to 07 volts each but if the installer snips the link then all three diodes are dropping so the installer measure the voltage and decides to snip or not to snip.
Other designs actually have a preset resistor to trim it (theoretically a little bit more accurate).
The battery manufacturer usually guarantees them for 12 months and advises renewal after 5 years max (if charged "properly"), Ive seen quite a few still seem healthy after 7 years, much longer than that and you would be very lucky.
Of course it all depends on the ambient temperature range it sits in throughut its life and its charge/discharge cycles too!
SLA by the way.

 

[Rodders53]

I checked the battery yesterday and it was 14.65V
So do you think I should charge it at say 12.5V?

That's rather high and suggests it's been on a charger of some sort --- smart, vehicle alternator?

How are you using this Leisure battery and in / on what?

Some one said about that 50% would be about 12.8V

They were wrong.

That's 100% soc at 26.7 Celsius when measured with no load (open circuit) and any surface charge higher Voltage from being on charge has been dissipated (via time or a load for a short time).

50% is around 12.3 V at the same temperature. 12.5 would be around 70% state of charge.

 

[ericmark]

With Burglar Alarm Systems etc the SLA battery is usually recommended on constant float charge of 13.6 Volts to 13.8 Volts

Yes, seen too many VRLA (valve regulated lead acid) overcharged, specially with stair lifts, 13.6 is ample when no load in fact more like 13.4 volt, for something like emergency lights and alarm systems, where the battery is only a back-up. With the stair lift, every time it is used it discharges the battery, so if used around 6 times a day, around 14 volts will recharge the battery giving a reasonable recharge time, but if the stair lift is not used, it will wreck the battery, as being overcharged.

So we tend to use stage chargers, these often measure current as well, but not always, so we likely would have a range of charge rates, starting at say 5 amp until voltage hits 14.4 volts, then drop to 3 amps, until 14.4 volts again, then 0.8 amps until 14.4 volts again, then 0.1 amps until 14.4 volts again, also the reverse, this time 12.8 volts, so when it drops to 12.8 volts it steps up a stage.

There is a problem, if the leakage means the battery never hits the 14.4 volts, but hovers at 14.2 volts, then the battery could overcharge, so better units also have a timer built in, so if charging for 4 or 8 hours, it will auto drop a stage.

As said, some measure current, and will drop a stage when current hit say 3 amps, problem is where battery being used while charged, so current does not drop below 3 amps, so yet another method is pulse charging, it is charged for set time, then the charger measures the time it takes the voltage to decay, and set charge rate based on this, Sterling make chargers, mainly for boats, with some very clever charge systems, but looking at maybe 4 x 120 Ah batteries and two 60 amp alternators, 3 batteries pulse charged, and one battery float charged to start the engine.

Lucas had an alternator with a temperture sender, mainly used with tractors where the battery was on top of the engine.

The idea is with a 13.6 volt float charge, the cells can become uneven, but charging to 14.4 then allowing to drop to 12.8 is less likely to let the cells become uneven.

In the old days of the dynamo batteies would remain part discharged for longer, and the cells could be topped up, so we would once a month give the battery an equalizing charge. This stopped when we got alternators. The open circuit voltage for a C40 dynamo with a RB108 reguator was 16 volts, but I have never found a battery actually reach that voltage. In the main once we got alternators we stopped using current control, but CAV 208 had current control, so not all alternators had no current control.

 

[muckington]

I have just checked it now and its down to 14 volts (down from 14.6V 2 days ago)

 

[Rodders53]

I have just checked it now and its down to 14 volts (down from 14.6V 2 days ago)

How are you using this Leisure battery and in / on what?

Is it connected to anything or not?

 

[muckington]

How are you using this Leisure battery and in / on what?

Is it connected to anything or not?

it runs 3 motion detection cameras only, and a wifi dongle