OK, so 4.2 x 7 = 29.4. Suddenly I remember someone saying that. So I reiterate, how do you fully charge 29.4 volt batteries with 24 volts ? ? ? If you've figured that one out then you're a genius and potentially a billionaire.

Fine, now that you understand my battery system well.

The reason I started this thread is not to charge my 29.4v battery with 24v, I only asked "if connecting the two 12v PS in series would be work fine to make 24v..."

Then I later asked somewhere, if it's possible to boost the 24v into 29.4v using a circuit I can build.

Though I know this is possible with a regular DC-DC Boost converter but ones I found has got a low total power output.

 

I know this is possible with a regular DC-DC Boost converter but ones I found has got a low total power output.

The reason why they have lower output is because you can not get more power out than you put in. Power is the key word. Power is defined by wattage. 10 volts times 2 amps is 20 watts. 2 volts times 10 amps is still 20 watts. In a perfect world you can get out exactly what you put in. But we don't live in a perfect world. There's inefficiencies everywhere in nature. In electronics, some power is converted into heat energy. Some cases such as a motor, power is also converted into wind energy since air has to be moved around inside the motor.

If you have 24 volts and as you say, 32 amps - that's 768 watts. Assuming 90% efficiency, which is on the high side, 768 watts becomes about 690 watts. That's 690 at 24 volts. Boost that voltage to 29.4 volts and you lose amperage. 690 ÷ 29.4 = 23.5 amps. Lets take this into an absurd realm; say you want 40 volts. 690 ÷ 40 = 17.25 amps. The wattage can not change without putting more power into it. Since your power supply is capable of a finite amperage at a given voltage, you can not get more out of it than you put in.

So yes, you CAN bridge two power supplies - as others have already said, provided they're not internally grounded. And as others have already said, you can not get more amperage than the weakest link in that combination. The picture showed a smaller PS, which you explained you were only using for the photo. Boosting the voltage means dropping amperage. That's the law. It can be done. But you have to understand the engineering behind it. It's like a seesaw. One side goes up the other side must go down. Nobody has ever invented a seesaw that both sides can go up at the same time. You can elevate the fulcrum, but you can not make both sides go up at the same time.

 

Two power supplies in series still do not make a 7s balanced Lithium battery charger.
Each group of parallel cells must have its voltage sensed and prevented from exceeding 4.20V (the balancing part).
The total current of the series groups must be limited, then sensed so that when it drops fairly low, the charging must stop (because then the battery is fully charged and must not have a trickle charge).
At first, the charger circuit must detect the total voltage because if it is lower than normal, the charger must attempt charging at a low current, and if the voltage does not normally rise then it must stop the charging of a defective battery that might catch on fire if faulty charging continues.
A battery charger IC does all these things, a power supply does not.

 

Seems like a lot of conversions to get to your final power. It would make more sense to design from scratch which would be more efficient.

 

Merry Christmas to you'all.

@Tonyr1084 has cleared it think. Thank you all for the support.