How to convert a bicycle to an e-bike

Many e-bike riders have tried cleanrepublic.com products for many years. There are also other sellers out there who can offer alternative products.

Low-cost conversion of any ordinary bicycle to an electric bicycle varies depending on the amount of money and effort you are willing to invest.

Option 1. Ready made conversion kits (at least USD 499) from U.S. resellers.

• http://www.electric-bike-kit.com. USD 499 excluding shipping from U.S., taxes and duties. Range: 6-8 kilometers per charge. Charging time: 1-2 hours per charge. 24v, 250 watts
• http://e-bikerig.com. USD 529 excluding shipping from U.S., taxes and duties. Range: 7-10 kilometers per charge. Charging time: 1-2 hours per charge. 24v, 250 watts

Option 2. Assemble your own (at least USD 418)
http://www.electric-bike-kit.com/propacklithium.aspx. USD 418 excluding shipping from U.S., taxes and duties. Range: 7-10 kilometers per charge. Charging time: 1-2 hours per charge. 24v, 250 watts

Option 3. Buy from manufacturers (at least USD 90 excluding shipping from China)
Look for sellers that accept 1 unit orders. Most accept 10 units minimum.
http://www.alibaba.com/countrysearch/CN/e-bike-conversion-kit.html

If you have tried cleanrepublic.com or other sellers, please post your experiences here.

NOTE: More posts on e-bike conversion projects are available here.

Where do 24v battery packs come from?

As a long-time user of of the 24v 250 watts 8Fun motor electric bike kit, I know that dealers (from where I bought my battery packs) purchase these from suppliers in China. I am not entirely sure if these dealers are merely resellers or if they design the packs and have them manufactured in China.

Comparing the pictures from Alibaba.com and my pack, one can see similarities.

My 24v 10.4 Ah pack

The one on Alibaba ad

If you search google for "24v 10.4 Ah battery pack" you will get the following search results here and here.

The price offered on Alibaba.com for each of these 24v 10.4 Ah packs are USD 99 and USD 101 but you have to buy them in bulk.

I also checked for "24v 5.2 Ah battery pack" and I got the following search results here and here.




My 24v 5.2 Ah pack looks similar to the ones on Alibaba.com. For example:

The price offered on Alibaba.com for each of these 24v 5.2 Ah packs are USD 70 and USD 85. But again, you have to buy them in bulk to get that price.

How about the battery management system (BMS) module inside the packs?

The BMS inside the 30K battery packs from LEED looks like this:

Back side of BMS board inside LEED 30K pack

Front view of BMS board inside LEED 30K pack

As you can see from the markings, the BMS is made by fcybattery.com. If you check their company website (FCY Technology) you will see that the 24v battery packs they sell look the same as the ones sold by LEED so maybe FCY is the supplier. FCY also has Alibaba ads on their site and the picture of the battery pack looks exactly like the picture of the pack on the Alibaba ad mentioned earlier.

The FCY website does not quote their price for the 24v battery packs but if these are the same as the ones on the Alibaba ad then the retail price must be the same or lower if you are buying in bulk.

LEED packs contain 2600 mAH Samsung cells but the pack themselves contained in a hard plastic box which offer good protection from accidental collision with other objects. Bothe the 30K pack and the 10K are contained in plastic boxes. The plastic boxes probably costs about 8 USD.

The 10K Sprinter pack sold by Clean Republic does not come with plastic box, only heat shrink wrap and some kind of insulation cover. The BMS board, however, show that Clean Republic may have designed it and only had it manufactured in China. The reason I say this is because the board has a different model number (LT-P721 v1.1, 2012.06.19 ROHS) unlike most BMS boards that include the website of the manufacturer. Clean Republic Sprinter BMS board also uses a prototyping circuit board and white JST female plugs for the balancing wire connections.

Clean Republic Sprinter BMS LT-P721 v1.1

If you have one of these 24v battery packs yourself, you can take them out of their nylon bag and compare if they look the same as the ones pictured above.

If you have old packs that are dead and are beyond the warranty period, you can also try opening the pack itself by removing the cells from the heat shrink wrap and/or the plastic box. CAUTION: be careful in opening these packs. They contain lithium ion cells that are prone to catching fire when shorted. I cover the exposed nickel plates with insulating tape whenever I open them for testing and fixing.

My next project it to add battery holders to my 10K 7s2p Sprinter pack from Clean Republic so that it will be possible to replace single failing cells instead of throwing away all 14 cells. According to batteryuniversity.com, doing so is possible. It is unlikely that all the 14 cells will fail at the same time so having battery holders instead of spot welding the 18650 cells will allow removal and testing of individual cells for replacement with new similar cells. If this can be done safely, it is better for the pocket and for the environment. Amazon sells Samsung 2900 mAH cells for 12.50 USD each (175 USD for 14 cells). Clean Republic sells new Sprinter packs for 269 USD. Amazon sells Samsung 2600 mAH cells for 5 USD each (70 USD for 14 cells). LEED sells new 10K packs for 199 USD.

NOTE: More posts on e-bike conversion projects are available here.

How far can you go with each battery pack?

Comparison between products I tested

Leed 30K 10.4 Ah Samsung Li-ion battery pack 

(349 USD plus shipping 26 USD shipping = 375 USD total)

Specs: 24 volts multiplied by 10.4 Ah equals 250 watt hours (uses pink ICR18650-26F SAMSUNG SDI 2600 mAh cells). If each mile (1.6 km) requires 20 watt hours then this pack will give you 12.5 miles or 20 kilometers. My own test confirms this calculation.

Ideally, the pack should last 600 charge cycles. If it does (I have no user confirmation of this yet), then the pack should give you 12,000 kilometers of electric-powered rides. That is 3 cents per kilometer (electric charging costs, motor kit and accessories not included).

If you calculate the costs of a complete kit (700 USD), then the cost per km is 6 cents.

Left: Clean Republic 10K 6.6 Ah Sprinter with 29.2V/2.0A charger. Right: Leed 30K 10.4 Ah with 29.4V/3.0A charger. 

Leed 10K 5.2 Ah Samsung Li-ion battery pack 

(199 USD plus shipping 25 USD = 224 USD total)

Specs: 24 volts multiplied by 5.2 Ah equals 125 watt hours (uses pink ICR18650-26F SAMSUNG SDI 2600 mAh cells). If each mile (1.6 km) requires 20 watt hours then this pack will give you 6.25 miles or 10 kilometers. I am still in the process of testing to confirms this calculation.

If the pack lasts for 600 charge cycles, then the cost per kilometer is 4 cents (6,000 kilometers/229 USD). If it lasts only 100 cycles then the cost is 24 cents per kilometer.

Clean Republic 10K 6.6 Ah Samsung Li-ion battery pack 

(269 USD plus UPS shipping 36.64 USD)

Specs: 24 volts multiplied by 6.6 Ah equals 158 watt hours (uses blue ICR18650-26E SAMSUNG SDI 2900 mAh cells). If each mile (1.6 km) requires 20 watt hours then this pack will give you 8 miles or 12.6 kilometers. My own test confirms this calculation.

No charge cycles are available on the Clean Republic site for their packs anymore. So assuming 100 charge cycles, the pack will cost 21 cents per kilometer (1,260 kilometers/269 USD).

Cost per day and maximizing the warranty

If the above calculations are correct and you want to maximize the 1-year warranty, you must use the pack, say, the 30K pack, and charge it at least two times a day for 300 days. Why? Because it is likely, based on my experience, that the pack will only last 100 charge cycles. I have tried it and I am still waiting for other users to confirm if the same thing happened to their battery pack.

If you do not use the pack everyday of the year and only use it 100 times a year (2 times a week for 50 weeks), like I did, the 365-day warranty will expire without using up all the 600 cycles at 100% capacity it is guaranteed for. Using it 100 times will only use up 100 charge cycles.

If the pack lasts only 100 charge cycles, then the cost per kilometer for the 30K battery pack becomes 18 cents. For the complete kit, it is 36 cents.

Compared to taking the bus to cover the same distance per ride, a bus ride of 17 kilometers will cost me 2 USD per ride, which is 12 cents per kilometer. Does this mean that taking the bus is 12 cents cheaper than the cost of a 100 charge cycle battery pack? My 17 kilometer bicycle ride costs me 3 USD, that means I spend 2 USD more per ride on my electric bike. The 379 USD battery pack costs 3.79 USD per 20 kilometers of riding.

I still prefer cycling than taking the bus, so the extra 12 cents I pay per kilometer or 2 USD per ride is actually worth it.

NOTE: More posts on e-bike conversion projects are available here.