Now you will see how to make a battery for electric vehicles ( similar to this one , but higher in voltage). Many people are afraid to assemble Li-Ion 18650 cells on their own, but as it turned out, you can make such a battery yourself, thereby saving several hundred dollars. And before proceeding with the assembly, it is necessary to consider several aspects:

1. What kind of battery pack do you need. In this case, we are talking about powering the engine with a nominal voltage of 48 V, this voltage will give 13 cells connected in series, that is, 13S (13 x 3.7 = 48.1 V). Unfortunately, this assembly will not last long, because the motor has a power of 500 W, which gives approximately 10.5 A of current consumption, and the largest elements currently on the market have a capacity of 3.6 Ah, that is, for starting the engine and driving for some time one would have to connect 3 packs of 13S in parallel (39 cells) this would give 48V 10.8Ah, which would probably be enough for about 30 minutes. But at higher loads on the motor, for example when driving uphill, the current consumption increases, in an electric car it can even increase up to three times. Therefore, a much larger supply of energy is needed.
2. How much space for the battery and what shape should it be. Each electric car may have a different location of the battery, in one it will be installed under the frame, in the other it will be in the trunk. That’s why it’s important to check how much space and whether the assembly we want to use will fit in the planned installation location before assembling the battery.

Next, we take the necessary materials for assembling the battery: insulating gaskets, holders, nickel tape for connecting cells and a BMS (battery management system) necessary for proper operation. And of course, the 18650 cells themselves.

Before assembling the battery, it is worth charging each can to 3.7 V. To charge individual cells, a conventional phone charger and a module for charging lithium-ion cells are enough – but this will take a lot of time, so it is worth negotiating with the seller to deliver the cells fully charged.

When the cells are already charged, prepare them properly. To protect the cells from short circuits, a washer of insulating material should be applied to each of them. Of course, you can make such washers with your own hands, but it is better to buy a kit, especially since its cost is small.

When all the cells are ready, they should be placed in holders, special plastic baskets for arranging the cells. Someone will think: what are the holders for, you can glue it with double-sided tape or hot glue and it will also be fine. However, this method should not be used to build packages due to the fact that intensively used batteries get very hot, and the use of holders allows them to cool more efficiently.

n this case, the shape of the battery has a cuboid body. The car was originally powered by four gel batteries, so the new battery had to be designed to fit these gel batteries combined. The battery consists of 130 cells, and it is impossible to split it in half, so one assembly of 10 x 7 cells is made.

On the other hand, the second 10 x 6 cells, but in order to keep the correct shape, filled the last row with appropriately cut pieces of the RL-18 mounting tube, thus creating a place for installing the BMS balancer module.

Having prepared the packages in this way, it is necessary to weld them. You may ask: why not just solder? Such a connection is much more reliable than a soldered one, and it should be remembered that the battery will often be subjected to strong shocks during operation.

Of course, even the simplest welding machine is needed to make welds. You can make something similar from an old microwave, or rather its transformer.

A special nickel tape was used to connect the cells to each other, usually a tape 8 mm wide. When buying tape, you should pay attention to whether they are really nickel. Nickel-plated steel bands are also on the market, they have much poorer conductive properties and are a little more difficult to weld.

In order not to make a mistake when welding and not cause a short circuit, during operation we connected both packages with masking tape. The welding process takes quite a long time and requires patience.

Having made the welds and checked them for correctness, they folded both packages, inserting a 3 mm polycarbonate gasket between them.

The necessary cables for connecting the BMS, as well as cables for charging and powering the electric vehicle, were soldered to the battery prepared in this way. These cables must be properly sized because they will carry quite large currents. Here, wires with a cross section of 2.5 mm2 were used, and their ends ended with an XT60 connector.

After connecting the BMS, they covered it all with appropriately cut pieces of plexiglass and wrapped it with a wide PVC tape. An inspection hole is cut into one of the walls to facilitate access to the BMS module and diagnose the condition of the battery. After disconnecting the plug from the module, measurements of individual cells can be carried out.

And here is a finished automotive lithium battery of 13 series-connected cans, each consisting of 10 pieces of 18650 connected in parallel – 13S10P comes out, the whole package is controlled by one BMS.