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52 Volt Battery Proceed With Caution

52 volt batteries have become popular, but are they really living up to the hype? Are they safe? We sold 52 volt batteries for about 1 year because of the constant customer requests, this is what we learned and why we no longer advise using them.

1- 60% of 52 volt packs we sold had failures within 1 year! 

2-  Squeezing in the extra 4 cells for a 13.5 Ah or 5 cells for the 17.5 Ah packs means you can no longer use the frame that mechanically holds all the cells together, resulting in broken spot welds and nickel strip. Cells would literally fall out when opening the case. All the cases on the market were designed for 48/36 volt packs, 52 18650 cells for 13.5 Ah, and 65 18650 cells for 17.5 Ah, with 48 volts being the largest pack size available not 56 or 70 cells. Because the cell frame holder cannot be used, the packs are built by hand and not by CNC spot welding robots, resulting in varying levels of quality. The nickel strip which is meant to be an electrical connection only, ends up being most of the mechanical strength of the pack. Some packs have hot glue or heat shrink to try and mechanically hold the cells together, but it's a hack and over time and vibration they fail. You can even verify no manufacturers make a 52 volt case. Go to Hailong's website also known as ShanShan Plastic Company linked here: http://en.kssssj.cn/products_detail/productId=50.html  you will notice it states maximum cell capacity of 65 cells for a 48 volt 17.5 Ah pack. They do not make or sell a pack that can hold 70 cells. Here is a link to their cell holder for reference as well, again not able to hold the extra cells:  http://en.kssssj.cn/products_detail/productId=105.html

3- The BMS is not popular anywhere else in the world except for US and as a result there is low demand, low production, little to no quality improvements and the failure rate is higher for 52 volt BMS vs 48 volt BMS which are widely used and constantly improving.

4- Bafang and many other motor mfgr's do not want 52 volt packs used on their 48 volt motor systems and firmware has been updated to inhibit their use. For example, new motors from Bafang will fail for error code 7 when the 52 volt battery is fully charged at 58.8 volts. Dealers revert back to older versions of firmware to get around this, but is rolling back firmware a good solution? We don't think so. Any vendor selling you a bafang mid drive that works with 52 volts is installing years old firmware to make it work.

5- Higher voltage from 54.6v to 58.8v may give you a 1 mph speed increase because higher DC voltages make the DC motors spin faster, but it comes at a cost. The electrical components are not rated for these higher voltages which can push the spec tolerance too high resulting in controller failures. The speed increase is barely noticeable and really not worth the trade off of in quality pack construction.

6- Worst of all.... we had a Hailong 52 volt pack catch fire! It wasn't locked properly and came off the bike hitting the ground. It cracked the case but still worked so all appeared fine, but hours later it went into thermal runaway. 

The battery is the heart of the system. It is critical that your investment last and not have failures. Many of our customers use their bikes to commute to work daily. Imagine your daily commuter breaking down on your way to work. The  cool, new, better 52 volt battery upgrade that has been hyped up leaves you stranded. Unless you have a warranty, or know how to repair a battery yourself, proceed with caution.

We are constantly being asked to fix these failing 52 volt batteries for people who have them. It could actually be a full time job position just repairing these 52 volt packs being pushed onto unwitting customers. Many vendors have terrible to no support at all after the sale, we hear it regularly. 

Below are images of a 52 volt Hailong branded pack brought to us from a guy who bought if from Amazon. Notice there is no frame holder to keep cells together properly. Nothing is holding the pack together so after re-balancing the cells and repairing the broken nickel It was wrapped with tape to give it some type of stability. Nothing much more we could do with this pack. Do you want to spend your hard earned money on something like this? It had broken nickel in 4 places and was only a few months old.

52 volt pack without cell holding frame

It's hard to tell, but this was a broken spot weld below. This pack was assembled by hand and you can see how poorly the nickel lines up with the center of the cells. Poor build quality!

broken spot weld from vibration over time

This little piggy... hangs out there all by itself. It's been crammed into the case smashed up against the lock mechanism when the case is assembled and will just keep on breaking off. Nice huh?

Broken nickel strip 52 volt battery

Here you can see the broken spot weld and a dented cell from improper fitment into the case by cramming in extra cells it was never designed for.

52 volt battery broken nickel strip

To help those out there with this issue the only "quick fix" is to ditch the nickel strip and use stranded copper wire that can flex when the cell moves around. You can try this if you are unlucky enough to have one of these 52 volt packs. Almost everyone we open up is broken right here. It's the most common failure. Make sure to bring that cell to the same voltage potential as the other cells before connecting it with the stranded wire.

52 volt battery broken nickel repair with stranded copper wire

Below is an example of the frame holder that holds the pack together. The black frame that holds all the cells together into a single unit. Notice above on the green cells, nothing is holding it together, but below the purple cells are all nicely held together inside that black frame holder. It's a properly designed and constructed pack. Most 52 volt packs are made like the above images. There is no cases and cell holders designed by these manufactures designed for 52 volts, so they cut corners to bring one to market. I challenge all 52 volt pack owners to look inside their packs and show a picture of how its made. This article is on endless sphere so you can share your pics and discuss it there where it can reach more people.

 48 volt pack with cell holder

So what's the point?

The point is, if you are looking for what battery to get, 48 vs 52 volt.
Understand that the Hailong branded 52 volt packs on the market are not being built correctly.
Ask sellers to send pictures of the inside of their pack, ask what is holding the cells together. Make sure it isn't a pic of a 48 volt version ; ) The 48 volt versions will always include the frame and be of solid construction, the 52 volt versions won't.
48 volt packs, because of the frame and jigs provided by case mfgr, have CNC spot welded pre-died and cut nickel strip.
52 volt packs are hand assembled, and hand welded with hand cut strips. The workers actually hate making them, isn't that a warm fuzzy knowing the pack maker is cursing this thing they are making you, not good!
48 volts is plenty, you will have a blast, you will never notice the difference.
Just get a 48 volt pack because it will be built the way it was designed, by somebody not hating building it.
Go for the build quality, not the extra 4 volts.



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