Difference between pages "Tools needed" and "Parallel Batteries"
Black Moons (talk | contribs) (Created page with "Converting an e-bike is a simple task that only requires a few basic tools. Here is a quick list of what you should expect to need to convert a bike to e-bike. ==Metric Allen keys== Many bike parts are held together by SHCS (Socket head cap screws) that require Allen keys to undo. Metric Allen keys are used on bikes, but you might encounter some e-bike kit that uses imperial somewhere. ==Metric Wrenches== While there are not many bolts on bikes these days, e-bike kit...") |
Black Moons (talk | contribs) (Created page with "There are two methods you can use to safely parallel batteries. ==Direct connection== To safely parallel batteries directly for more capacity, you must first ensure they are the same chemistry (lipo, li-ion, lifepo4, lead acid, etc) and the same voltage. Never attempt to directly connect batteries in parallel of different chemistries. It is also best if they have a 2 wire BMS (Charge and discharge through the same wires), since otherwise directly cross connecting th...") |
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There are two methods you can use to safely parallel batteries. | |||
== | ==Direct connection== | ||
To safely parallel batteries directly for more capacity, you must first ensure they are the same chemistry (lipo, li-ion, lifepo4, lead acid, etc) and the same voltage. | |||
Never attempt to directly connect batteries in parallel of different chemistries. | |||
It is also best if they have a 2 wire BMS (Charge and discharge through the same wires), since otherwise directly cross connecting them may defeat the overcharge protection. | |||
By directly connecting the positive wires to each other and the negative wires of a 2 wire BMS, you can charge both batteries and discharge them through the same wires at the same time. | |||
You must first however charge both batteries to the exact same voltage (fully charged is recommended as its easiest to reach) as directly connecting batteries of different charge states can cause huge currents to flow. Its best to verify with a DMM that they are the same voltage before connecting. | |||
It is recommended to have an individual fuse or breaker for each battery, but not strictly required as the BMS should be able to disconnect the battery in event of over-current. | |||
This means you can not directly connect a second battery in parallel as a backup unless its going to stay attached or only be attached when both batteries are fully charged. Use an A or B battery switch instead if you need to switch to a backup battery. | |||
== | ==Diode connection== | ||
By using high power diodes, you can ensure your one battery won't discharge into the other and can even connect different chemistries of battery or even different voltages, although they won't share the load if you do mix voltage/chemistries and you will need separate chargers. | |||
The diodes need to be rated for higher then your max battery voltage and the full current you expect to draw, ideally much higher. This will make them rather large and likely require heat sinks. The diodes only need to be on the positive wires, directly connect the negatives. | |||
You also need to use additional diode or separate connectors for charging. If you use diodes they will need to be rated for the full current of your charger and batteries. | |||
Note that if you use diodes, your controller will no longer be able to recharge your battery and regen braking must be disabled. | |||
Latest revision as of 08:26, 15 January 2022
There are two methods you can use to safely parallel batteries.
Direct connection
To safely parallel batteries directly for more capacity, you must first ensure they are the same chemistry (lipo, li-ion, lifepo4, lead acid, etc) and the same voltage.
Never attempt to directly connect batteries in parallel of different chemistries.
It is also best if they have a 2 wire BMS (Charge and discharge through the same wires), since otherwise directly cross connecting them may defeat the overcharge protection.
By directly connecting the positive wires to each other and the negative wires of a 2 wire BMS, you can charge both batteries and discharge them through the same wires at the same time.
You must first however charge both batteries to the exact same voltage (fully charged is recommended as its easiest to reach) as directly connecting batteries of different charge states can cause huge currents to flow. Its best to verify with a DMM that they are the same voltage before connecting.
It is recommended to have an individual fuse or breaker for each battery, but not strictly required as the BMS should be able to disconnect the battery in event of over-current.
This means you can not directly connect a second battery in parallel as a backup unless its going to stay attached or only be attached when both batteries are fully charged. Use an A or B battery switch instead if you need to switch to a backup battery.
Diode connection
By using high power diodes, you can ensure your one battery won't discharge into the other and can even connect different chemistries of battery or even different voltages, although they won't share the load if you do mix voltage/chemistries and you will need separate chargers.
The diodes need to be rated for higher then your max battery voltage and the full current you expect to draw, ideally much higher. This will make them rather large and likely require heat sinks. The diodes only need to be on the positive wires, directly connect the negatives.
You also need to use additional diode or separate connectors for charging. If you use diodes they will need to be rated for the full current of your charger and batteries.
Note that if you use diodes, your controller will no longer be able to recharge your battery and regen braking must be disabled.