lithium ion
I connected 10x Lithium Ion batteries in series (3.7V, 2100mAh), I looked into the datasheet and the charging voltage is 4.2V with a current of 1A.
Can I simply solder this battery management system to the battery string and connect it to a 42V 2A charger to safely charge it or will it blow up?
The circuit you show is effectively a resistive limiter, which you say you do not want.
You need a switching charger like the LTC1513 which will do what you want:
This won't quite meet you 2.4 A charge current requirement in the form shown above, but you could boost the current capability of the switch to meet the need.
The pulse current from your supercaps will go up as the voltage drops of course, so you may end up needing 10-15 A switch capability.
I understand your question. I did something similar in one of my projects some years ago. I wanted to prioritize cell life over runtime, so I just charged the cell to 4.1V and then disconnect the charger. The constant voltage charging phase is what makes you able to have the maximum runtime, so in this case my opinion is that you can go without it.
I actually don't know where the 3.92V come from, but it is not uncommon to use Li-ion cells in a narrower voltage range in order to improve battery life. Some EV manufacturers, for example, start with a narrower voltage range which guarantees the declared vehicle range. Then, as battery ages and loses capacity, the voltage range is progressively extended to compensate and to maintain the original range.
Best Answer
Generally when dealing with lithium based batteries you need to be extra careful and you have to know exactly what are you doing, because there is a great risk of fire or explosion when you handle them unproperly (overcharging, short circuit, overtemperature etc.).
If you want to charge multiple cells in series, you should always use balancing circuit that takes care of charging all cells to the exactly same voltage. When you do not use a balancer, the cells will eventually get charged to different voltages after few cycles. The difference in voltages between each cell will get bigger over time and if you are lucky, you will only end up with a dead cell in a battery pack; if you are unlucky, it may catch fire.
Also, discharging an unbalanced pack will lower it's overall capacity and may even lead to negative voltage on some of the cells.
It is OK to charge the cells with lower current than their maximum rating, but you should never exceed the maximum charging current, that they are specified at. (Charging them with lower currents will actually prolong their life)
There are many articles on battery balancing on the internet, you should go through them first.