The wires that connect the four batteries together are called the wiring harness. The wiring harness is attached to the batteries with nuts and bolts which can be disassembled to remove the harness and get the old batteries out. The new batteries should be installed in the exact same positions as the old batteries and the wiring harness attached to the new batteries exactly the same way that it was attached to the old batteries. I always recommend taking a picture of the old batteries and wiring harness before installing the new batteries so you know how it goes back together, which you have already done and posted right here on this forum.
Please feel free to let me know if you have any questions.
12 Volt 18Ah Battery
This connector requires soldering to install.
We can solder wires onto the connector for an extra $5.00 service fee. Just let me know how long the wires need to be, and what gauge they need to be, and I can make a listing for the connector with wires soldered onto it.
Item # CNX-620, 2V1H (2 vertical 1 horizontal) connector.
The red and black wires may be different lengths.
If you can not find the wire gauge printed on the wire then we could use 12 gauge wire which is a heavy enough for all 48 Volt electric bikes that are 1000 Watts or less.
We can also install the connectors on the opposite end of the wires from the 2V1H connector so you do not have to cut and splice the wires together. This is what I recommend. If you could take a picture of the entire wire harness, and also a picture of the connectors on the opposite end of the wires from the 2V1H connector then I can determine what they are and make a plug-and-play replacement harness for your electric bike.