Thread: bosch driver - dying power packs

The old do I replace the battery or replace the tool dilemma.

If the batteries are Ni-Cad, I would upgrade to a tool with a Li-Ion battery.
If however it is already Li-Ion then it is a hard choice. If you feel tool does all you want then it could be worth just replacing the battery. Also does the battery fit any other tools in the makers line the you may purchase over the life of the battery?

Lots to consider with no right or wrong answer, we will all have different views.

Originally Posted by old_picker

replacements are around $75 ea would need 2 - $40 - $50 extra gets me a new replacement driver with 2 batteries

i hate this - a perfectly good drill headed for the rubbish bin
any way of saving it ????

You can rebuild battery packs. Some battery distributors also offer the service. In the US the retailer Interstate Battery will do the job for about $40. If it uses NiCad you can purchase replacement cells. Most tools use a size called 'sub-c'. If you have a significant number of similar tools investing in an appropriate battery tab spot welder and a box of replacement cells can be worth the expense. Lithium cells are also available New 6pcs Ultra Fire 18650 3 7V 5000mAh Lithium Rechargeable Battery Yellow E556 | eBay.

Cheers,
Rob

If taking the DIY approach to rebuilding your battery packs, please note that there are different types of 18650 cells. Shooting for 3000mAh cells designed for laptop packs is not what you want, they will not be able to supply enough current for power tools applications.

Current 3000mAh cells from Panasonic and Samsung are built for high capacity, low to medium drain applications for eg, 3-10 hours runtime. If these cells suits power tools we would be seeing 6.0Ah packs on the market but no, not at this time yet. The latest 5.0Ah/5.2Ah packs consists of 10x 18650 cells in a string of 5 series and 2 parallel configuration. Yes 5.xAh not 4.0, Australia is behind again.

Search for "18650 high current" and they come in 1300, 1500, 2000mAh or 2500mAh. These cells are specially designed for high discharge applications and will do so cycles after cycles. Unfortunately due to the design of todays high current Lithium 18650s and super quick chargers they cut short the cell life.

I would not be bothered rebuilding NiCd packs. If you have one of the earlier packs with USA made cells such as Energizer, good for you, they are very tough and can withstand abuse. Chinese made NiCd cells today are planned for the recycle bin as soon as they are packed for sale. Most has internal resistance shoot up the roof as quickly as 20 cycles. Worst is the 18V packs you get 15 cells in series if one of them fail you are toast.

I rebuild my packs with hobby helicopter lithium packs, they deliver the current easily as they are designed for and they are cheap and easy to get. They are also lightweight.

There are many risk of mishandling Lithium cells and the risk is usually when charging. If you are modifying your tools please don't ignore the warnings. I have plenty of parts from my radio control heli so its no brainer for me to rebuild all the cheap NiCd with LiPo. I also use hobby chargers they help you keep track of your battery health.

Below is a cheap 18V power tool fitted with high current connector. I dislike the original slide/clip clamp on spring connectors I think they create a resistance. It's a hassle to unplug the battery for charging but it's worth it in my opinion.
P1100231.JPG

Below is the inside of the 18V battery pack, it looks like one of those terrorist job I admit but it works fine for the pass 3 years. I toss the cheap drill whenever I can
P1100239.JPG

I choose LiPoFe4 chemistry similar to the A123 Nanophosphate technology due to safety, it's less fire risk than regular Lithium cells. Second, it's higher life cycles and takes a lot of abuse. However, they are lower capacity compared to Lithium Polymer pouch cells.

They have a nominal voltage of 3.3V per cell is much suitable for NiCd repack.
Four cells makes great replacement for 12V NiCd battery pack.

A freshly charged 12v NiCd pack is around 14V. Then drops to 12V at 80% capacity, if you are lucky. Underload, it will hold it's voltage if it's quality cells.

For LiPoFe4 cells(4 in series).
Freshly charged they are 3.6 x 4 = 14.4V. Then drops to 13.2V. Underload it will be slightly more than 12V.

Below is a 12V repack in cylindrical cell A123 18650
P1100238.JPG

I charge them with hobby chargers, and the white tabs are balancing plugs. This will help to keep each cells in balanced. If there is a significant weaker cell, it will be over-discharged before the others. This is not a problem if they are matched. The Samsung cells in Bosch battery pack are factory matched and they are fast charged without balancing modules. I'll show you a picture when I have time to crack one open.

Another reason for this is that you can never have enough drill drivers. I use these cheap lightweight drills a lot. They are at least 200 grams lighter great for overhead work. Much more power compared to 10.8v drills and longer runtime. For masonry and deep hole drilling I break out the Bosch hammer.

There are plenty of sources for Lithium cells. If repacking, please avoid 'protected' lithium cells. These cells are (3rd party)fitted with a BMS(battery management system) or a simple thin circuit board consist of a IC manager chip and a mosfet which protects the cell against over discharge, over current and over charging. An example is the ebay one linked above posts. Most of these IC management chips are designed for mobile phones cells and have a limit current of 2A. Power tools need a lot more than that, think 40 amps at highest load. Anyway protected cells are useless you will end up ripping them apart.

You will need to look for high current cells with tabs for easy soldering. If you have access to a spot welder then better. I get my cells from online hobby stores. As economical as possible.

Here's what Samsung have to say about their power tool 18650 cells, scroll down to the end of page to view the part numbers. I am particularly interested in the new 2500mAh cells which makes the new 5.0Ah cells from various manufacturers.
Power Tool | Application

Notice that the 1.3Ah and 1.5Ah cells have a higher discharge current of 23A, which makes 2.6Ah(1.3Ah x2) and 3.0Ah(1.5Ah x2) packs more punch than 4.0Ah packs. Also notice that the new 2500mAh cells can only do 20A discharge current. So cell discharge current was sacrifice for higher capacity. Still, a 5.0Ah pack, it will be able to do 40A max discharge, similar to performance to quality NiCd.

Metabo claim that the new 5.2Ah battery pack is made of Sanyo/Panasonic(own Sanyo batteries now) new UR18650NSX. So far datasheet is not available on the website.

Up-To-Date Information - Press Metabo International - Metabo worldwide

Cylindrical type | Lithium Ion Batteries | Batteries & Energy Products | Industrial Devices | Panasonic Global

Currently the power tool 18650 market is dominated by Samsung, with Sony pushed out due to cost. Panasonic makes more 18650 low discharge for laptops but not for long. Sony Energytec used to the main player but failed to reduce manufacturing cost.

Great information. Can you give us a tutorial on conversion from Ni Cad to Li packs? Is it necessary to change chargers and etc.

Cheers,
Rob

Originally Posted by rob streeper

Great information. Can you give us a tutorial on conversion from Ni Cad to Li packs? Is it necessary to change chargers and etc.

Cheers,
Rob

Hi Rob,

Like I said, I used a hobby charger to charge my repacked batteries. On top of that, I have a smoke alarm installed on the shelf, where all the charging activities are done. Lithium chemistry cells cannot be safely charged with a Nickel Cadmium charger.

If repacking 18V NiCd packs, you need 3.6V Lithium cells in 5S(5 serially connected) configuration.

For 14/14.4V NiCd packs, you need Lithium cells in 4S configuration.

I start off by measuring the dimension of the battery case, then look for batteries that will fit. It's just a matter of space and fitting when it comes to selecting cell types. I would choose 18650 form factor over hobby rectangular Lithium Polymer pouch cells.

These pouch cells are made for high current drain but they don't have a strong metal shell like the 18650. The weak body pouch cells can be punctured by sharp objects and cheaper cells puff up like a blowfish sometimes for no reasons. The advantage of these pouch cells are lightweight, higher capacity, cheaper, prebuilt with balancing connectors.

This is an example of some prebuilt pouch cells
Batteries & Accessories>Li-Poly (All brands)

Like I said, if you sourced 18650, you will need to find them with tabs if you are soldering them. You will also need to add a wire to every connection where a cell joins electrically with another. These are balancing wires that goes into balancing socket of any hobby charger. I'll post some pictures tonight when I get home.