Using High Capacity Cordless Tool Batteries in Ebikes

[6zfshdb]

With all the "hate" being heaped on e-bike batteries lately, I've been experimenting with using the new high capacity cordless tool batteries as replacements:

The Lithium types, which replaced the old Ni Cad's, have been around for a decade or so with very few reported incidents. This is likely due to the fact that they are designed for job site use and are very rugged. Many of us, including myself, already have several of these cordless tool batteries lying around so why not put them to use on your bike?

As newer, higher capacity models become available, they are becoming more attractive for e-bike use. Most have fast charge capabilities using a number of different chargers, including 12V vehicle units, designed specifically for this type battery.

The idea is to use several wired in parallel using battery isolators. That way, the weight can be distributed more evenly on the bike frame. I usually carry one in my rear rack bag, one in each pannier and sometimes a fourth in a handlebar bag.

Depending on capacity, they are also allowed on airplanes and can be useful for those who travel with their bikes. They can also be replaced if necessary at most home improvement stores.

There are some disadvantages however. Cordless tool batteries are more expensive per A/H than most designed for ebikes. The 15AH (5AH at 52V) model shown above cost a bit over $300. I have a couple of contractor friends who have used these lithium tool batteries for many years with little loss of capacity. It is possible they will have a longer lifespan which may improve their overall economy.

 

[Bob.A]

I've thought about using powertool batteries as well. I have a bunch of Bosch 18v including two 8 amp versions. What I'm not so sure about is how well they would work paired up and how well the battery electronics would play with a load not designed with that battery in mind. From what I understand, each manufacturer does things differently with how they manage battery output vs load. Some makes put most of the BMS electronics in the batteries while some put it in the tool. The whole point of the BMS is to control how fast the batteries are drawn down to a certain charge and how fast and how much they are charged back up. This keeps the battery from overheating and prolongs the life of the cells.

 

[6zfshdb]

I've thought about using powertool batteries as well. I have a bunch of Bosch 18v including two 8 amp versions. What I'm not so sure about is how well they would work paired up and how well the battery electronics would play with a load not designed with that battery in mind. From what I understand, each manufacturer does things differently with how they manage battery output vs load. Some makes put most of the BMS electronics in the batteries while some put it in the tool. The whole point of the BMS is to control how fast the batteries are drawn down to a certain charge and how fast and how much they are charged back up. This keeps the battery from overheating and prolongs the life of the cells.

This is very true and, for the reasons you mention, some research is needed to find suitable batteries. Those with a built in BMS are the best choice but some bike controllers have a low voltage cutoff as well. As long as the controller cuts out above the low voltage rating of the battery, it should work. Again, research is important.

The newer high capacity, higher voltage cordless tool batteries are designed for use in lawn mowers, chainsaws and other high drain equipment. The voltage used is also critical. Two 18V or 20V batteries can be wired in series for 36V e-bikes and 60V batteries work well in 52V bikes. 48V bikes can be more difficult to power with these batteries though.

I've been using DeWalt 60V batteries on my 52V bike for several years now and notice no difference in motor performance. Measurements indicate I can draw 30+amps intermittently with no issues using 2 batteries in parallel with an isolator.

Unfortunately, I doubt bike makers will ever change their designs and adopt this concept. For now, using power tool batteries on an e-bike definitely requires DIY skills and a basic knowledge of electricity.

 

[Zen Support]

With all the "hate" being heaped on e-bike batteries lately, I've been experimenting with using the new high capacity cordless tool batteries as replacements:

View attachment 145826 View attachment 145827

The Lithium types, which replaced the old Ni Cad's, have been around for a decade or so with very few reported incidents. This is likely due to the fact that they are designed for job site use and are very rugged. Many of us, including myself, already have several of these cordless tool batteries lying around so why not put them to use on your bike?

As newer, higher capacity models become available, they are becoming more attractive for e-bike use. Most have fast charge capabilities using a number of different chargers, including 12V vehicle units, designed specifically for this type battery.

The idea is to use several wired in parallel using battery isolators. That way, the weight can be distributed more evenly on the bike frame. I usually carry one in my rear rack bag, one in each pannier and sometimes a fourth in a handlebar bag.

Depending on capacity, they are also allowed on airplanes and can be useful for those who travel with their bikes. They can also be replaced if necessary at most home improvement stores.

There are some disadvantages however. Cordless tool batteries are more expensive per A/H than most designed for ebikes. The 15AH (5AH at 52V) model shown above cost a bit over $300. I have a couple of contractor friends who have used these lithium tool batteries for many years with little loss of capacity. It is possible they will have a longer lifespan which may improve their overall economy.

That's quite an innovative approach to e-bike batteries, using high-capacity cordless tool batteries. Their ruggedness and availability indeed make them an interesting option. However, it's crucial to consider cost-efficiency and safety aspects.

At Zen Ebikes, we're aware of the cost and warranty disparities in the e-bike industry. We're working on engineering solutions, like wire-bonded, long-lasting battery packs. Our prototypes for mopeds and 3-wheelers are promising. We aim to offer 2 kWh packs at competitive prices and launch e-bike-specific batteries at Eurobike 2024.

Appreciate your insights and support in advancing battery technology for e-bikes!