36v Drill Project

Hi All

I am trying to do one of those drill conversions after all the nickel batteries died on my 36v Drill.

I know that strictly speaking I should get some high stength 18650's but to begin with I want to prove I can make it work.

I plan to use 18 or 20 18650's for the project. (9x3.7=33.3 or 10x will be 37v but not sure if this will damage the drill)

I have bought a few bits and pieces off ebay for the project but I think my biggest problem is going to be finding a charger that is practical to use and that can charge 36v.

The battery housing in the Drill is removable and plugs into a custom charger that came with the drill.

It will not be practical to remove the batteries from the Drill Housing for charging.

My first thought was to cut hole in the battery housing and charge it via the IMAX but the IMAX can't do 36v

I have collected all the 18650's I need from old and newer Laptop batteries for the trial, if it all works

I also bought a 36v BMS board on eBay so that the batteries are charged properly


My problem is the charger, then I saw this video and thought how it would be good if I could do a conversion of the old charger to make it support 18650's


Currently it does provide 36v but I gather it does this for NM batteries that were previously fitted.

Can someone tell me if this type of conversion is practical and what components I would need, it would be ideal if I could get that to work.

If it provides the correct input voltage to the BMS you are all set.

A lot of people use printer power supplies

You can search ebay for such having the required input voltage for BMS

So are you saying that I can use the existing power supply which does produce 36v but I imagine has a different charging profile?

I was thinking to put the BMS in the battery pack,

I am using one that people seen to use for electric bikes, 36v seems to be popular for that too.

I like the simplicity of using the same power supply but I need to know it is safe, I have heard all sorts of comments saying you must not use a power supply for NMH or Ni-Cad for L-Ion project,

The video seems to suggest that one can rip out the parts and replace them with cheap components BUT he does not put a BMS on all the time,

DC powered motors can handle a wide range of voltages. The drill may be "rated" at 36V, but it can safely run up to 40V, maybe even 48V without issue. The higher the voltage, the lower the amp draw. But also increases heat generation. But for a drill that's used intermittently this shouldn't be an issue.

You use nominal voltage to calculate wattage/power of the packs. But for voltage ranges, you need to use top/bottom voltages.

So, with standard 18650's, we'll use 4.1V - 3.2V
10s:
4.1V = 41V top end
3.2V = 32V bottom end

9s:
4.1V = 36.9V top end
3.2V = 28.8V bottom end

You should go with 10s in this case. Otherwise, you'll have a "weak" drill all the time.

Going with 11s would yield:
45.1V - 35.2V
This will make the drill more powerful. It'll have more torque and faster drill speeds

You "can" use the same charger. The problem is there is a difference in the charge profile, as you mentioned. Also, the 36V "NMH/Ni-Cad" charger will not charge to the full voltage of lithium ions. It'll only charge up to about 38V. I'm assuming 25s on the current battery pack. But your packs might have multiple cells in series in a mini-pack so that you may only have like 5s (5s * 5 = 25s)

Getting a charger that can actually charge lithiums at 36V would be better as it'll give not only range, but also the charge curve. Or, you could use a buck converter to drop a 48V-ish supply down to 38V and charge at full current. Then drop the current down by 50% for the final charge to make sure the packs are full.

For any 36-Volt tool, you need to use 10 cells in series (20 in total for 2 pairs).
The reference for high power cells is 3.6 not 3.7.

Overpowering it with an additional pair may cause over-drain of cells and I don't know of any 11S BMS.

Laptop cells will NOT work for a powerful drill because they cannot provide sufficient sustained current. You need to use cells recovered from power tool li-ion batteries.

A measured 36V for a charger is not sufficient.
In theory, you charge cells up to 4.2V and that would mean 42V++ charger (45, 48 or even 50+ measured while not connected).

I am having trouble understanding one aspect of the BMS

I totally understand the thin wires

It is the solder points that are confusing me because unlike say an eBike or Skateboard on a drill you remove the battery from the drill where it is discharging and plug it in using the same connectors to a charger.

On my BMS there are three connectors and on the battery there are two, so do I join these and will they still work or do I create some elaborate switch that move it from discharge mode to charge mode. if so why was this not required on the lawn mower I took the battery pack from?

Here is my BMS with a crude drawing of the battery





So which wires go to B- P- and C-

Here are a collection of suggested ways to wire the BMS, what is confusing me is that on a Drill battery Charge and Discharge are the same wire, but I am concerned that it would not perform as expected if these were not separated somehow..

The battery pack Positive connector goes directly to load. This is also the connected to the charger Positive as well. So, common Positive

C- connects to the Charger's Negative
P- connects to the Load Negative
B- connects to the Battery Negative


This is the closest of the above that I think is the most accurate and understandable:

Hi & thanks for your reply

I think I must be a bit blonde because I am stil confused.

As far as I can see the positive side is pretty easy, according to that diagram they both go to what is described as "Main Terminal B+" or the positive end of the battery.

B- is also easy because it connects to what is described as "Main Terminal B-" or the Negative end of the battery

The issue is

C- connects to the Charger's Negative
P- connects to the Load Negative

Because if you look at my crude drawing of the battery and connector for the drill there are only two wires, negative and positive, because the connector

Does that mean that C- connects to P- because if it did I can't imagine that the BMS would work or maybe it would?

If you look at how most of these batteries work it is the same

The battery comes out of the tool and plugs into a charger as shown in this image





So there is never anything taking the load when plugged into the charger except the charger negative itself, so maybe they DO connect together?

It is quite possible the C- and P- are combined externally from the BMS. They have some pretty beefy FETs on the circuitry which keep current flowing the wrong way through the gate. So charging while connected to the P- won't be forced in through the P- but will be readily accepted through the C- connection.

But before connecting anything like that, pop that cover off and look at the traces. Could even be surprised that the traces are connected together internally.
If you pop the cover off, please post a few pics of the circuitry so we can better see what's going on.

I've done something like this... here is my project link in case you wanted to check it out.
https://secondlifestorage.com/showthread.php?tid=4670

Personally I would build the packs, but use a RC / balance charger to charge / maintain the batteries. I don't use a BMS because the currently handling and performance (or lack of it) , just a cell monitor that will alarm.

I do agree with the comment about not using laptop packs. For projects like these, high drain cells all the way. I bought new, but things like those used hoverboard packs would be ideal.

Korishan said:

The battery pack Positive connector goes directly to load. This is also the connected to the charger Positive as well. So, common Positive

C- connects to the Charger's Negative
P- connects to the Load Negative
B- connects to the Battery Negative


This is the closest of the above that I think is the most accurate and understandable:

Click to expand...

Korishan said:

It is quite possible the C- and P- are combined externally from the BMS. They have some pretty beefy FETs on the circuitry which keep current flowing the wrong way through the gate. So charging while connected to the P- won't be forced in through the P- but will be readily accepted through the C- connection.

But before connecting anything like that, pop that cover off and look at the traces. Could even be surprised that the traces are connected together internally.
If you pop the cover off, please post a few pics of the circuitry so we can better see what's going on.

Click to expand...

Thanks for your considered reply, the more I think about it the more I think they both connected to the outgoing line, what I do not know is how it determines what is Charge Load and what is Power Load. As I understand it, the power load is an output of what goes into B-

When it is powering the drill it will only be getting the Power Load Discharging the battery, but will the circuitry get confused by seeing anything on what is labelled as a Chargers Negative or is it just neutral. I guess the question is why have it separate, is it to make it easier for builders or is their some function therein?

I have seen videos on building your own BMS what I would like to understand is how the BMS works, I get that those thin wires are sense wires that flip gates in the BMS so that current bypasses cells, but I can't say I have grasped the soldering points.

I found this DIY BMS project quite good at explaining the BMS function but no clear on my questions above about the solder points.


I bought my BMS just on the Amps and Voltage capabilities, I figured for a 36v drill I did not need it to be the dogs b.

I have seen some with just two connectors, so I think I might order one of those and comply with your request to take mine apart and upload photos.

Sorry to waffle on but I think it might help others who are in same position as myself gain understanding.

Basically it's up to the FETs that determine which is which. A FET has a diode of sorts built in. The FETs are usually back-to-back (instead of parallel) in this configuration, this allows the power to flow a certain way based on the direction of the FET arrangement and whether charge/discharge mode is active. There's other details on the design, but that's the basics right now.

CrimpDaddy said:

I've done something like this... here is my project link in case you wanted to check it out.
https://secondlifestorage.com/showthread.php?tid=4670

Personally I would build the packs, but use a RC / balance charger to charge / maintain the batteries. I don't use a BMS because the currently handling and performance (or lack of it) , just a cell monitor that will alarm.

I do agree with the comment about not using laptop packs. For projects like these, high drain cells all the way. I bought new, but things like those used hoverboard packs would be ideal.

Click to expand...

Thanks Crimp Daddy

I originally was going to use my hobby charger but I then discovered they do not support 36v or 10s.

I also wanted to make the drill self sufficient with charger that it came with, I had planned to get into the power supply to see how it different it is but it has a wierd non torx screw, so need to find a tool for that.

10s support on hobby chargers is available if you were interested in purchasing another, if you are not, I understand as its an added cost. It is how I ended up with a couple different models myself. Initially I never thought I would need more than 6s.

The iCharger 1010b+ or the 3010b are nice options to consider. The 1010 is pretty inexpensive and nice to have around for the types of things you are doing. Even if it was for the occasional pack maintenance / balance charge which is often times how I use mine for projects like this where I would consider using a "regular charger"

Keep us updated, these types of projects are fun.

Korishan said:

Basically it's up to the FETs that determine which is which. A FET has a diode of sorts built in. The FETs are usually back-to-back (instead of parallel) in this configuration, this allows the power to flow a certain way based on the direction of the FET arrangement and whether charge/discharge mode is active. There's other details on the design, but that's the basics right now.

Click to expand...

So I did a bit of searching on eBay, I was considering getting a better BMS as I need one for a 4 cell project for my Pure Radio and maybe 5 cell project for a mini vacuum cleaner.

I came across this which seems to be the one I ordered, according to the diagram from the ad (below) you do not connect the P- at all. Any thoughts on this?

It describes it as 16amp 36v 37v and 42v 10 cell








https://www.ebay.co.uk/itm/263164589688

So just to add a twist I was testing the charger that came with the Drill today, it is clearly marked 36v but I measured the output to find it is only shows 18v.

I do not want to spend mney on a separate charger so I am going to rip out the guts of the existing charger as per the video on page one.

I would still appreciate any thoughts on not connecting as shown in image.

Did you test the charger with or without a battery connected? What's the model # of the charger?

It's possible it starts at 18V and then ramps up once a battery is connected. That could be its communication voltage. Or, it's dual function charger that can do both 18V and 36V batteries.

Schoolboy error on my part, I plugged in the connector which is off the battery at the moment.



It is an unbranded NiCd charger, label is below








Drill is same as this one

Delete

Re-Posting this to correct spacing and imaging.

I was considering changing the original power supply, then I thought it was not working (schoolboy error above), but while looking for new 36v power supplies I came across this 2a one on eBay:

https://www.ebay.co.uk/itm/352679199302

At this price and weight it seems like a no brainer, can anyone see anything wrong with this charger?

Delivery is forever, so is it worth paying for 3A one, is it safe?

https://www.ebay.co.uk/itm/383114371013

It means I can separate the Charger wiring on the BMS to what appears to be industry standard.

I have decided I want to put some sort of meter on it to show battery level, I have a push button press and hold switches I can use.

Has anyone had any experience of the following

1. Blue Red Amp meter
[img=400x400]
I have a few of these already although some warn the voltage to power them should be no more than 40v, I figured I could connect to the wiring points where I joined the two batteries where voltage is 20v

The wiring of these and using shunts makes it more complicated, they say if over 10A then should use a Shunt, but I plan to have the meter only display when I push a button, I am not sure if 2p 10s battery is 10A when not actually drilling, to to shunt or not to shunt?

I have found the following diagrams of how to wire it, I do find these confusing,

Independent Screen supply wiring
[img=400x400]
Shunt wiring 1 (if over 10A)
[img=400x400]
Another vendor Shunt wiring (looks more complicated
[img=400x400] 2. Circle simply Meter
[img=400x400] 3. Square Simple Meter
[img=400x400]https://i.imgur.com/C9Nkn0v.jpg[/img]
4. Display bars only
[img=400x400]https://i.imgur.com/8jxM4gB.jpg[/img]
5. Amp Volts Ohms Bar - I like this but only measures up to 30v
[img=400x400]https://i.imgur.com/dyLWPhi.jpg[/img]
Any thoughts welcome....