How to fix a broken 30K lithium-ion battery

Last time I posted about my broken 30K lithium-ion battery pack from LEED. Years ago, I also posted about my broken SLA battery pack from Clean Republic. Both packs are actually easy to fix if you know how the parts work.

It turns out that in both cases, the problem tends to be the connectors. The DIN connectors of the SLA battery pack gets so overheated that the solders melt. The controller sometimes burn out because of the heat as well.

The most recent connector problem with my 30K lithium-ion battery pack, as it turns out, is due to the Dean T connector (female plug connecting the battery and the controller) burning out. I never heard of this but I discovered that this was the problem why my battery pack is fully charged and yet no power comes out of the pack. The positive plug of the female Dean connector show signs of burned surface.

close-up view of the burnt female plug positive hole

multitester reading zero on the positive hole of the Deans T connector plug

I simply replaced the Dean T connector and it fixed the problem. My 30K lithium-ion cells are still alive. They should since these are Samsung cells that are rated 1500 charge cycles. They still have about 1150 cycles left so they should last for years to come.

Building a better pack with serviceable parts

Imagine a broken 40 cent Deans T connector causing you to buy a new 30K battery pack that costs at least 400 dollars? If users know how to fix their own pack they could save time, shipping money and effort.

I suggested to dealers that they provide the option to service parts but they don't see that such an option is profitable. Users are therefore left to DIY this option. Like this new DIY built 10K pack with removable 18650 Li-ion cells.

To the right is my DIY pack with removable cells that are 26,000 mAH each (Samsung ICR18650 26F). The device on the left is an inverter that converts the 24V DC given out by the pack to 110V AC that powers the computer I use to write this blog.  The pack can power my 45W computer for 5 extra hours. The pack can also power my e-bike motor kit. 

Why make the 18650 cells removable?

1. Commercially available battery packs have the battery cells parallel connected, thus, these cells  cannot be truly balanced. By making the cells removable, it is possible to check each cell using a balance changer.
2. It makes it easier to replace the broken connectors and failing cells instead of replacing the whole pack (when cells are soldered together).
3. Users learn how to make their own pack by being familiar with the parts and their function.
4. It is fun to make.  

Here is what is inside the DIY pack:

The schematic diagram for the balancing wires are shown below. This is based on the reverse-engineered connections of my old Sprinter battery pack assembly from Clean Republic.

The next time my battery pack breaks down, I know how to fix it. It is possible to get BMS board replacements from dealers. Controllers are available for 50 dollars each if these break down. The 18650 cells can be easily replaced by hand instead of having them permanently soldered to nickel plates.

This is a 7s2p battery pack configuration that the Clean Republic 10K Sprinter BMS supports. Note that the balancing wires are color-coded to make it easier to make sure the right wires are connected to the right plug. The positive and negative points of the 7 series (2 parallel) battery cells are connected to the BMS board which then balance outputs 25.9 V to the controller. The BMS also balance inputs charge to the battery cells in the series through 7 balancing wires. The BMS is like a mini balance charger for each of the parallel cell-couple in the series. The BMS board costs 25 dollars. The balancing wire white wire to board connector plugs are about 1 dollar per 10 pack set.

Remember: Before you declare your pack dead check the connectors first!

Word of advice that will save you hundreds of dollars and the trouble of sending back lithium-ion battery pack though the mail: test the connectors for burnt or melted points first before you declare your pack dead.

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. 

Inside a 30K Li-ion Battery Pack

So I opened my 15-month old 24V 10Ah Lithium-ion battery pack from LEED (e-bikerig.com). Here is what's inside!

1. LSW153-45-6 controller
2. Cream-colored plastic enclosure wrapped in black rubber heat barrier
3. A 7S4P (7 series 4 parallel connected) 28 pcs. of Samsung ICR18650-26F 2600 mAh cells wrapped in black plastic shrink wrap
4. Battery Management System (BMS)* attached to battery cell pack

*The BMS controls the input-output to ensure that each cell gets enough charge and are all balanced. When one cell gets below the charge threshold it shuts down the pack. No output. When charging, once each cell reaches its full charge, either the BMS, or more likely the smart charger sold separately, shuts off the charging.

Why I opened it? The pack failed after 1.3 years of ownership

This old battery pack was delivered to me back in January 23, 2014. I paid 314 USD for the battery and shipping costs to Norway. I paid an extra 46 USD for custom duties. All in all it cost me 360 USD.

On April 23, 2014 (3 months later), the battery pack stopped working after a long uphill climb of about 1 km. The two kits I have been using tend to die out in long climbs so I had to be cautious the next time I used them. However, since this 30k pack stopped working, I sent it back to LEED on June 20, 2014 (about 2 months later). The battery is still under warranty.

However, it took about 4 months before I got the replacement since the retailer had to send the defective battery back to the supplier in China which sent a replacement to my retailer, then to me. So I got the replacement October 8, 2014 and started using it October 16, 2014. I used the battery pack from then on until it stopped working on January 16, 2016 (1 year and 3 months). Not bad for a 360 USD battery pack that lasted 15 months (3 months beyond its 1 year warranty). Note, however, that I did not use the pack everyday so I am sure I have not LITERALLY used it for 1 year. I am also certain that I did not charge it more than 600 times nor more than 1,500 times.

My 30K battery lasted about 100 charge cycles only

The 30K battery itself is advertised as good for 600 charge cycles at 100% capacity. But since I only charged it for a maximum of 100 times (I log my charges) the advertised maximum life in terms of life cycles has not yet been fully exhausted, only the maximum time of ownership guaranteed has passed.

Does anyone use and charge their battery 2 times a day for 300 days in a year? 

Unless the battery pack is used 2 times a day and charged 2 times for 300 days, the 600 charge cycles at 100% capacity advertised specification will not be used up during the 1 year warranty period.

To actually use up the 600 cycles and 1,500 cycles in a more realistic sense, 1 year and 8 months is needed which is equivalent to 600 days of daily charging. Therefore, to really guarantee the 600 cycles, the warranty should be at least 20 months, since 1 year is too short to test it.

Use your battery 2 times a day for 365 days to maximize warranty

Only if the battery is used 2 times a day for 365 days can the 600 charge cycles advertised be used up. Even if that can be done (which I was not able to do), that is only 730 charge cycles for the whole 365-day year. If that is done, only use 600 charge cycles at 100% capacity can be used plus 130 charge cycles at 80% capacity. Given that, the battery pack is supposed to have 770 charge cycles left at 80%.

Are there any users out there who have actually used their battery beyond 600 charge cycles (i.e. 20 months of daily charging)? Let me know if there are any.

BMS shutting down discharge due to failing cells

I suspected that it is either the controller that is busted or probably the Battery Management System (BMS). Using a multitester revealed that the battery is still charged (the charger indicates it is) but I do not know why the pack stops discharging when I connect it to the motor or my inverter. My new battery pack powered my inverter just fine.

The BMS seems to be shutting down the output from the pack (probably because one of the cells is below the charge threshold or is failing). According batteryuniversity.com repair is possible. You just need to replace the failing cells if the other cells are still good. I have not done that for now because I do not have the equipment and the know-how yet. Maybe in a later project I will try doing this. In the meantime, I have one controller to spare in case the controller of my other battery pack breaks down. I also have some spare cells to use (if they still work).

Opening the pack

Here is how I opened the battery pack.

I removed the black plastic wrap using a cutter, detached the controller, removed the 4 screws from the plastic case, removed the black plastic wrap from the battery cells and pulled out the cells attached to the BMS. I did it carefully to avoid short-circuiting the Li-ion cells.

I used a multitester to see if the battery is still charged.

The tester is set to 250V, hence the low meter which is about 26V. But later testings show that the charge is falling rapidly from 10v down to 5v etc.

So aside from the controller module outside the black rubber wrapped cream plastic casing, there is a BMS attached to the side of 28 bundled Samsung cells.

The cells are labelled ICR18650-26F (SAMSUNG SDI 2E54). It is 2600mAh 3.7 volts each. Amazon sells these 18650 cells for 5.18 USD each (so 145 USD just for the 28 cells). LEED sells the pack for 349 USD. So the mark-up and the plastic casing, wiring, connectors, and the BMS probably costs about 155 USD since the controller costs 49 USD.




Here are the components of the attached BMS:




Here is the schematic diagram of the wires connecting the pack and the BMS:



The chips on the BMS board include the following:

C404BA 525



P75NF75& CZONG 5 MAR 308



Several of these smaller components: 331, 102, 305, 0, 105, 089, 103, 101, and RD10.

What is inside other battery packs?

I wonder what is inside other packs? If you have tried opening your own pack, please share. For example, I am interested in seeing what is inside Clean Republic and ALLCELL packs.

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