Charging x2 12volt battery’s 7.2Ah in parallel 24v

[markymark2406]

I need to know what a good Ah is to charge:
x2 12volt battery’s 7.2Ah in parallel 24v

??

Thank you

 

[ericmark]

2 x 12 volt in parallel is 12 volt, in series it is 24 volt, and commercial chargers for that size are normally around 0.8 amp auto dropping to 0.1 amp and zero when recharging but when in stand-by often fixed voltage from 26.8 to 30 volt depending on the battery use, for example a flood lamp which only lights on a power cut 26.8 and a stair lift which is used daily 30 volt.

It also depends on battery type, even just lead acid with out considering other types, we have flooded, gel, and VRLA/AGM (valve regulated lead acid or absorbed glass mat) when you go to others there are all sorts of methods used like detecting peak voltages as constant current to turn off charge and having heat sensitive switches strapped to battery. Also computer controlled where it remembers how much charge is in battery.

Because it is so complex to work out charging rates, the norm is to buy ready made chargers.

 

[big-all]

delete

 

[davelx]

I need to know what a good Ah is to charge:
x2 12volt battery’s 7.2Ah in parallel 24v

??

Thank you

It might be worth you taking 5-10 minutes to read this:

https://learn.sparkfun.com/tutorials/series-and-parallel-circuits/all

 

[markymark2406]

2 x 12 volt in parallel is 12 volt, in series it is 24 volt, and commercial chargers for that size are normally around 0.8 amp auto dropping to 0.1 amp and zero when recharging but when in stand-by often fixed voltage from 26.8 to 30 volt depending on the battery use, for example a flood lamp which only lights on a power cut 26.8 and a stair lift which is used daily 30 volt.

It also depends on battery type, even just lead acid with out considering other types, we have flooded, gel, and VRLA/AGM (valve regulated lead acid or absorbed glass mat) when you go to others there are all sorts of methods used like detecting peak voltages as constant current to turn off charge and having heat sensitive switches strapped to battery. Also computer controlled where it remembers how much charge is in battery.

Because it is so complex to work out charging rates, the norm is to buy ready made chargers.

Yes sorry in series to make 24volt. So 0.8amp to start dropping

 

[ericmark]

With old motorcycle batteries over charging with reason just mean you need to top up more frequent, but with a VRLA it will destroy it.

Often a compromise is used, using stage charging or pulse charging we can recharge reasonably fast, but with fixed voltage 13.2 volt on a 12 volt battery will in a few days charge the battery, and 14.4 volt for an hour will not do much harm and mean it will charge in the limited time.

So for a cheap charger the designer has to consider time discharged, and time charged, and a compromise used.

The 7812 regulator chip was often used with a red LED between common and negative, this lifted the voltage to around 13.2 volt, with either a large capacitor or battery to power CB radios, the armature radios were more expensive so crow bar protection etc was used, but today switch mode power supplies are so cheap just not worth making your own any more.