3 Series Li-Ion Battery Cell gives 11,1 V nominally and 12,6V when fully charged and 9,9V when discharged. Since lithium batteries require special charging circuit, you can go with 3S charger. If 9,9 - 12,6 V range is okay, you can go with 3 series or 4 series for higher voltage then use voltage regulator to step down to 12V.

You always need lithium battery charger no matter what your configuration is. Search for 3S 4S Lithium Charger.

Charging parallel lithium batteries is not recommended.

Your arrangement is crazy and potentially dangerous. The system voltage will be 18.5volts and the system capacity will remain at 1.02Ah. There is real danger of overcharging the single batteries (with possible fire potential) as you try and force enough current down the chain to ensure the top 6 are adequately charged.

If you have 10 batteries and you want 12 volts then either arrange the batteries into parallel pairs then join 4 pairs in series. This means you end up with a couple of unused spares. 4 x 3.7 = 14.8v

Alternatively you could arrange the batteries into parallel triples (3 in parallel) then join three of these packs in series. This will give you 1 unused spare. 3 x 3.7 = 11.1

If you use the first arrangement the pack capacity will be 2.04Ah
If you use the second arrangement the pack capacity will be 3.06Ah

Whichever arrangement you use you will need an 'intelligent' charger that monitors each series pack and provides balanced charging.

Using the 4 x 2 arrangement means your discharge rate might give you about 40 minutes of run time
Using the 3 x 3 arrangement means your discharge rate might give you about 1 hour of run time

Clearly your batteries are undersized for the application if you want extended run times.

Whatever your discharge requirements you have complicated the charging.
Lipos require balance charging(lithium iron phosphate should be also but are more forgiving).
The parallel cells in series with the series ones will mean that the series ones will need balance discharging much more which will increase charge time and possibly impact battery life.

Some moddelers do employ parallel charging but it is not recommended especially if you do not understand how these batteries work.

12 V at 3 A .
You have purchased the wrong batteries i suspect.
What capacity do you require.?

If this is not for a flying model i would suggest a LA battery would be more appropriate.

How about a link to the EXACT cells you have to save so much guessing.

Your odd combination of parallel and series connections is not going to do anything useful. If they're Lipos they're dangerous when abused and if you try charging Lipos in that configuration you're likely to set your house on fire.

There is no combination of 10 lipo/li-ion cells that can produce 12V. You can have 11.1V (12.6V fully charged) with 3 cells in series. You could then connect 3 sets of those in parallel using 9 cells for 11.V 3060mAh. Then save the odd cell in case to need to replace one. But if you wanted an 11.1V 3000mAh battery it would probably have been easier to just buy one. They're readily available.

BTW most 1000mAh lipo cells can easily provide 3A on their own. It's really only a question of how long you expect them to run between charges.

If you want a constant 12volt, then use five pairs in series (5*4.2volt=21volt).
And a 12volt/5Amp buck converter.
Charge with a 5-cell balance charger.
Leo..

I recently bought 10 3.7V 1020mAh Rechargeable Li-ion Batteries to power my circuit which needs 12V and draws 3A of current.

I have arranged the batteries as shown in the Attachment.

What would be the Voltage of this Battery…??

What would be the Capacity of this Battery…??

How do I charge this battery safely…??

What would be the Voltage of this Battery…??
What would be the Capacity of this Battery…??
How do I charge this battery safely…??

Battery Voltage = 4x3.70V + 3.70V = 18.50V.

Capacity of your battery Pack = (6x1020) || 1020) <= 1020 mAh.

To preserve the normal life of re-chargeable batteries, we must stop drawing power from
Battery Pack when it reaches to final voltage of: (18.7V - (4x3x0.2+3x0.2)) = 15.5V.

jackrae:
Your arrangement is crazy and potentially dangerous. The system voltage will be 18.5volts and the system capacity will remain at 1.02Ah. There is real danger of overcharging the single batteries (with possible fire potential) as you try and force enough current down the chain to ensure the top 6 are adequately charged.

If you have 10 batteries and you want 12 volts then either arrange the batteries into parallel pairs then join 4 pairs in series. This means you end up with a couple of unused spares. 4 x 3.7 = 14.8v

Alternatively you could arrange the batteries into parallel triples (3 in parallel) then join three of these packs in series. This will give you 1 unused spare. 3 x 3.7 = 11.1

If you use the first arrangement the pack capacity will be 2.04Ah
If you use the second arrangement the pack capacity will be 3.06Ah

Whichever arrangement you use you will need an 'intelligent' charger that monitors each series pack and provides balanced charging.

Using the 4 x 2 arrangement means your discharge rate might give you about 40 minutes of run time
Using the 3 x 3 arrangement means your discharge rate might give you about 1 hour of run time

Clearly your batteries are undersized for the application if you want extended run times.

jackrae:
Your arrangement is crazy and potentially dangerous. The system voltage will be 18.5volts and the system capacity will remain at 1.02Ah. There is real danger of overcharging the single batteries (with possible fire potential) as you try and force enough current down the chain to ensure the top 6 are adequately charged.

If you have 10 batteries and you want 12 volts then either arrange the batteries into parallel pairs then join 4 pairs in series. This means you end up with a couple of unused spares. 4 x 3.7 = 14.8v

Alternatively you could arrange the batteries into parallel triples (3 in parallel) then join three of these packs in series. This will give you 1 unused spare. 3 x 3.7 = 11.1

If you use the first arrangement the pack capacity will be 2.04Ah
If you use the second arrangement the pack capacity will be 3.06Ah

Whichever arrangement you use you will need an 'intelligent' charger that monitors each series pack and provides balanced charging.

Using the 4 x 2 arrangement means your discharge rate might give you about 40 minutes of run time
Using the 3 x 3 arrangement means your discharge rate might give you about 1 hour of run time

Clearly your batteries are undersized for the application if you want extended run times.

Using the 4 x 2 arrangement means your discharge rate might give you about 40 minutes of run time

Capacity = 2.04 Ah

Load Current = 2 A

According to definition : The Power Source must be able to supply energy
for 2.04/2 = 1 hr (60 minutes) up to reaching at the final voltage.

In the ideal world where manufacturer actually tell the truth and batteries haven't changed with use or age and are perfectly charged then they might deliver what's expected of them at the specified Ah rate; but only if they are discharged in accordance with the manufacturers design criteria.

Without the manufacturer's specification and discharge curves of the subject batteries, it is impossible to determine whether the manufacturer specifies capacity at 1C, 0.5C, 0.1C or 0.05C etc.. 1C means discharged in 1 hour, 0.05C means discharged in 20 hours.

Since the OP hasn't enlightened us with the battery details, other than a figure of Ah capacity, which might be a figment of the seller's imagination, a best guess is anybody's guess.

The OP did state a discharge of 3 amps, or did you choose to ignore that fact.

Hence my guess at 40 minutes based on a 1C discharge rate.

jackrae:
In the ideal world where manufacturer actually tell the truth and batteries haven't changed with use or age and are perfectly charged then they might deliver what's expected of them at the specified Ah rate; but only if they are discharged in accordance with the manufacturers design criteria.

Without the manufacturer's specification and discharge curves of the subject batteries, it is impossible to determine whether the manufacturer specifies capacity at 1C, 0.5C, 0.1C or 0.05C etc.. 1C means discharged in 1 hour, 0.05C means discharged in 20 hours.

Since the OP hasn't enlightened us with the battery details, other than a figure of Ah capacity, which might be a figment of the seller's imagination, a best guess is anybody's guess.

The OP did state a discharge of 3 amps, or did you choose to ignore that fact.

Hence my guess at 40 minutes based on a 1C discharge rate.

Hence my guess at 40 minutes based on a 1C discharge rate.

That's fine; thanks.

jackrae:
In the ideal world where manufacturer actually tell the truth and batteries haven't changed with use or age and are perfectly charged then they might deliver what's expected of them at the specified Ah rate; but only if they are discharged in accordance with the manufacturers design criteria.

Without the manufacturer's specification and discharge curves of the subject batteries, it is impossible to determine whether the manufacturer specifies capacity at 1C, 0.5C, 0.1C or 0.05C etc.. 1C means discharged in 1 hour, 0.05C means discharged in 20 hours.

Since the OP hasn't enlightened us with the battery details, other than a figure of Ah capacity, which might be a figment of the seller's imagination, a best guess is anybody's guess.

The OP did state a discharge of 3 amps, or did you choose to ignore that fact.

Hence my guess at 40 minutes based on a 1C discharge rate.