Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[6705russell]

Can anyone tell me what it is the optimum voltage and charge rate/time for a 12v-24ah lead acid battery please?

Thanks

Russ

[tjones27]

Hi,
at a guess it would be 12V and 2.4Amps

a trickle charger would be best with anything upto a current of 2.4Amps. someone with greater knowledge might adivse you something else, but that what i would use 

[Roadrunner]

I use a 6-12v multi charger, charges battery's at 300MA i charger the battery's for 12 hours ( over night)  biggest 12v I have is 7ah and that takes about 15 hours.
I sure some one will come up with a smart answer in regards to MA charge rates per AH I've always just put them on over night between 10-12 hours and that is enough to run my models for the time I'm at the lake without failure .

For 24v battery's i suggest a car battery charger and follow its charging instructions/guidelines. 

[roycv]

Hi all, I believe that purpose built L/A chargers, 'Taper' charge until the full charge voltage is reached.
The maximum current may be limited at the beginning but a fixed voltage is applied and as the battery charges up and the battery voltage increases towards the expected final voltage of the battery, the voltage difference (and current) get less until it tapers out.

So it might be more exact to measure the open circuit battery voltage to check charge state of battery.  A L/A cell is at 2.4 volts when fully charged, so 6 times that = 14.4 volts.

But commercial chargers are not dear and that is what I use.

Hope that helps,
regards Roy

[nick_75au]

The best  chargers for Pb batteries are 3 stage chargers. Stages are bulk, absorbtion and float.

Most battery manufacturers reccomend a 1/10 C rate for 15 hours, which in your case is 2.4 amps, there are certain batteries that can handle higher charge rates.

The 3 stage chargers can be left on the battery all the time, as the float current is very low.
.
For a dumb charger 13.8 volts at 2.4 amps  for 15 hours and make sure the battery is dissconnected afterwards. ( I would get a 3 stage charger over this method though)

Here is more information than you would ever need

http://batteryuniversity.com/learn/article/charging_the_lead_acid_battery

Nick

[ACTion]

Russ
I use one of these and can recommend it for batteries up to 15AH. http://www.maplin.co.uk/two-stage-12v-sealed-lead-acid-battery-charger-15ah-12204
For larger ones I would probably contact Component Shop and have a word with Iain about using one of their 5000mA SLA chargers.
Dave M

[DickyD]

I beat the boss to it this time, I have already been to The Component Shop and bought one of these,

http://www.component-shop.co.uk/html/body_mw126c50.html

Should fully charge your battery in 5-6 hours.

[6705russell]

Thanks lads, plenty of assistance there, the Componenet Shop one looks like a winner...

Russ

[Rottweiler]

Hi Russ, put your query to an electronic engineer pal of mine and herewith his reply......Lead acid batteries should be charged with what is known as a Constant Voltage Charger, and as such, the charge voltage remains constant throughout the charge and the charge current starts off at a fairly high value, slowly dropping back until it becomes a virtual trickle charge as the battery nears full charge.  Consequently it can be difficult to quote a charge rate and time, and it is usually much easier to use an automatic charger, or monitor the electrolyte specific gravity during charging.
 
The nominal voltages for lead acid cells are: 2.2V fully charged and 1.8V (minimum) fully discharged.
So, a 12V battery (6 cells) should give 13.2V fully charged, and not be discharged below 10.8V.
 
In order to avoid excessively slow charge rates towards the end of a charge cycle, the battery charger might have an output voltage equivalent to 2.5V per cell (15V for a 6 cell battery).  Seem to recall car alternator systems are set for about 13.8V to maintain the battery in a fully charged condition once recharged.
 
Having said that, as a rule of thumb, a battery should be recharged for about 120% of the ampere-hour capacity that has been used.  So, in your friends case, he has a 24AH battery, and lets assume it is fully discharged and showing 10.8V.
 
Nominal "capacity" is 24AH, full recharge "capacity" would be 24AH x 120% = 28.8AH.
If we were using a constant current charger (unlikely) this equates to 28.8Amps for 1 hour, or 2.88Amps for 10 hours or 0.288Amps (288mA) for 100 hours.  Alternatively, you could achieve the same result with 500mA for 57.6Hours, or 1A for 28.8hours, 2A for 14.4hours, etc.
 
Unfortunately, there are lots of variables to take into account so it is very difficult to quote a charge rate and time.
 
Ideally, a longer and slower charge would be better for the battery as this helps prevent sulphation.  Also, Lead acid batteries should be regularly "exercised", ie: discharged and recharged every few months, to keep them in peak condition.
                                                                                                               
 
If he has a reasonable DC Volt Meter, he could try monitoring the voltage output of the charger during recharging.  This could confirm whether or not his charger is a constant voltage one.