Makita 18V vs 36V battery same Connector?

[YoshiMoshi3]

Are the connectors on the Makita 18V batteries the same as their 36 V batteries?

I know the 18 V and 40 V are different connectors. Is 18 V connector used on any of their other batteries?

Yes I know the voltage is different, I'm asking only about the connector here. Can anyone confirm?

Was thinking of the connector is the same I could take a 36V plastic battery case and connector and put the 18 V BMS in there, wire it up for 18 V and used it on my 18 V tools. Thanks.

 

[engineer2]

The Makita 36V system I know is just two 18V LXT batteries on the same tool, so the connector is the same. You just use two 18V batteries.
Am I understanding your question?

 

[KnurledNut]

They are not interchangeable.
The only crossover I know of is the factory adaptor that lets you use two 18v on the old 36v tools. (BCV03)
Been a long time since I messed with any of the 36v tools! Last one was the SDS rotary hammer.

@engineer2 @mike93lx
Now discontinued, but Makita had a proprietary 36v LXT line.
I believe this is what Yoshi is referencing.

 

[YoshiMoshi3]

They are not interchangeable.
The only crossover I know of is the factory adaptor that lets you use two 18v on the old 36v tools. (BCV03)
Been a long time since I messed with any of the 36v tools! Last one was the SDS rotary hammer.

@engineer2 @mike93lx
Now discontinued, but Makita had a proprietary 36v LXT line.
I believe this is what Yoshi is referencing.

Thanks and yes that's what I'm referring to. The connectors do look the same. Are any of the other battery lines use the same connector? I was thinking of building an 18v battery within the 36V shell.

 

[mike93lx]

I was thinking of building an 18v battery within the 36V shell.

Why? Are the 36's larger? I would have assumed not and that they are just wired differently

 

[YoshiMoshi3]

Why? Are the 36's larger? I would have assumed not and that they are just wired differently

Right they are a 10S2P pack, that hold 20x18650 cells. So if it's backwards compatible connector with 18 V, you can hook it up in a 5S4P configuration. I can't find higher capacity plastic shells in the 36V line that had like 30 cells for example. But there are already 18V shells that hold 20 cells. They are rather tall and even hold 15 cells of 21700s vertically (based on dimensions, have not tried if yet) that might give us more capacity

My Makita lawn mower, if the grass is a little long and I go about 2 weeks in cuts, I go through about three full charges. It has 2 sets of two 18 V batteries to get 36 V. It came with four 5 Ah batteries. Its annoying to have to wait to charge. And the only higher capacity battery is 6 Ah. So I was thinking of making my own higher capacity battery.

It looks like highest capacity 18650 cells are 3.5 Ah. So a 5S4P or 20 celld would give me 14 Ah. 21700 cells high capacity is 5 Ah. So stuffing 15 cells of 21700 in a 5S3P configuration in a plastic box that is meant to hold 20 18650 cells would give me a 15 Ah capacity.

 

[Rabid Badger]

I posted about solving this exact issue (with great success) right here:

Making the battery Makita won't.

This is long-winded. For the payoff, scroll down to the red arrow. I like my Makita tools. They're dead reliable, have excellent ergonomics and build quality and are consistently the best of the big brands when it comes to NVH. Unfortunately, I also like watching Torque Test Channel...

www.garagejournal.com

I ended up building 9Ah batteries with extremely high current output. I would be willing to bet, between the higher capacity and lower losses due to internal resistance, 4-6 of them would get you through your yard.

There's a link to the battery kits I used in the thread. I don't recommend using any other kit. As of right now, I haven't found another option that I would consider safe.

 

[YoshiMoshi3]

I posted about solving this exact issue (with great success) right here:

Making the battery Makita won't.

This is long-winded. For the payoff, scroll down to the red arrow. I like my Makita tools. They're dead reliable, have excellent ergonomics and build quality and are consistently the best of the big brands when it comes to NVH. Unfortunately, I also like watching Torque Test Channel...

www.garagejournal.com

I ended up building 9Ah batteries with extremely high current output. I would be willing to bet, between the higher capacity and lower losses due to internal resistance, 4-6 of them would get you through your yard.

There's a link to the battery kits I used in the thread. I don't recommend using any other kit. As of right now, I haven't found another option that I would consider safe.

Excellent! Which Makita lawnmower do you have?



I have the XML08 lawn mower which came with four 18 V batteries that are 5.0 Ah BL1850B 90 Wh.

There's maybe 5/8 of an inch of space between the two 18 V battery packs when installed into the lawn mower. I'm wondering if I have enough room to get the 21700 cell battery cases? Would you be able to tell me the dimensions of the 21700 cases? The dimensions I find online seem wrong.

 

[Rabid Badger]

Battery dimensions are 134mm L x 82mm W x 70mm H (5.28in L x 3.23in W x 2.76in H).

My mower is an XML08 as well. The 21700 batteries slot in, but I just discovered the lid won't latch with a pair in bank 2.

3D printing a latch with a second, longer catch shouldn't be too difficult. If you don't have a printer, you could bend a small piece of sheet metal into the necessary shape and screw it to the existing latch.

 

[mike93lx]

Battery dimensions are 134mm L x 82mm W x 70mm H (5.28in L x 3.23in W x 2.76in H).

My mower is an XML08 as well. The 21700 batteries slot in, but I just discovered the lid won't latch with a pair in bank 2.

3D printing a latch with a second, longer catch shouldn't be too difficult. If you don't have a printer, you could bend a small piece of sheet metal into the necessary shape and screw it to the existing latch.

So close. I wonder if you could soften the lid with a heat gun and stretch the plastic a bit while closing it?

 

[YoshiMoshi3]

Excellent! Someone that has gone through this exercise before I will be doing so! Hope to learn a lot here. How do you like the lawnmower? I have about 3/4 Acers. When I first got the lawn mower, I was able to do my whole lawn in just over one set of two batteries. Then slowly it just got worse and worse. Just over one set of two batteries, became almost two full sets of two batteries. Now, I'm down to about 2 complete sets of two batteries plus a little bit of a third set. I brought my batteries in to a repair shop, they said they were fine, but replaced them with new ones. The new ones have the same performance. I'm wondering if you noticed the same issue?

The stock 5.0 Ah battery uses either 10 cells of Samsung 25Rs or 10 cells of Sony Murata VTC5 in a 5S2P configuration. It looks like the battery pack can output a maximum 0f 40 A.



I have no desire in getting more "performance" out of my lawn mower. I'm not even sure if it's capable of accepting more current, but it doesn't really matter to me. I have no need for the engine to spin faster or for the self propulsion to rotate the wheels faster. I would just like a longer run time. So when designing the pack, I'm going to stay close to 40 A.

The aftermarket has some casings that accept 15 21700 cells. There's also the 5S2P cases that I think you used.




A 5S3P configuration, I would need to get 40/3 A from each cell, which is 13 and 1/3 A. I will just call it 15 A. I know that will give me slightly more current than desired of 45 A. But seeing that the LXT 4.0 Ah battery from Makita delivers up to 60 A, I think I should be ok.
Looking at the table from Mooch... he didn't really test 15 A draws. Likely because it's not a common output current draw for 21700s. I guess I could look at 10 A tests, the LXT 6.0 Ah only outputs 30 A, so maybe I'll be ok. Samsung 50S would be best for me, and give me an E-score of 13.7*3 or 41.1. They also have the highest rating at 20 A of 11.4

There are some cases that accept 20 18650 cells.

So looking at 18650 cells

In a 5S4P configuration, if my goal is 40 A, 40/4 is 10 A. The highest rated 10 A cell is
Molicell P28B, Molicell P30B OR Murata VTC6. Of these cells Murata VTC6 would likely be the best. Giving me an E score of 8.0*4 or 32.

So it looks like 15 21700 cells is the winner and Samsung 50S. I'm not sure if I did this right?

It looks like you used Molicel P45B in a 5S2P configuration. How's that performance compared to the stock 5.0 Ah battery? Wow! Those cells can output 45A, so you could get out 90A. Obviously there's some braking point, where the lawn mower isn't going to asking for more current. Does your lawn mower spin really fast, or the wheels in self propulsion compared to the stock 5.0 Ah battery that could only output 40 A? I assume it's pretty much maxed out and is drawing all the current it can ask for. Those are some high output current cells!

Thanks!

 

[Rabid Badger]

So close. I wonder if you could soften the lid with a heat gun and stretch the plastic a bit while closing it?

The gap is about 8mm, while the lip the lid closes around is 10mm tall. Extending the latch would provide almost essentially the same level of protection to the battery compartment without requiring any risky, permanent alteration of any part of the mower. I'm designing one now.

 

[Rabid Badger]

Excellent! Someone that has gone through this exercise before I will be doing so! Hope to learn a lot here. How do you like the lawnmower? I have about 3/4 Acers. When I first got the lawn mower, I was able to do my whole lawn in just over one set of two batteries. Then slowly it just got worse and worse. Just over one set of two batteries, became almost two full sets of two batteries. Now, I'm down to about 2 complete sets of two batteries plus a little bit of a third set. I brought my batteries in to a repair shop, they said they were fine, but replaced them with new ones. The new ones have the same performance. I'm wondering if you noticed the same issue?

I have 14 5Ah Makita batteries that I rotated through mower duty, so I didn't see the degradation you experienced.

I haven't noticed any increased energy consumption by the mower. Have you checked the condition of your blade and made sure the underside of your deck is clean?

The stock 5.0 Ah battery uses either 10 cells of Samsung 25Rs or 10 cells of Sony Murata VTC5 in a 5S2P configuration. It looks like the battery pack can output a maximum 0f 40 A.

I have no desire in getting more "performance" out of my lawn mower. I'm not even sure if it's capable of accepting more current, but it doesn't really matter to me. I have no need for the engine to spin faster or for the self propulsion to rotate the wheels faster. I would just like a longer run time. So when designing the pack, I'm going to stay close to 40 A.

Batteries with higher current output don't just increase the performance of your mower. They have lower internal resistance, which allows them to stay cooler under load compared to other cells. Less heat and less stress = longer service life.

The aftermarket has some casings that accept 15 21700 cells. There's also the 5S2P cases that I think you used.

A 5S3P configuration, I would need to get 40/3 A from each cell, which is 13 and 1/3 A. I will just call it 15 A. I know that will give me slightly more current than desired of 45 A. But seeing that the LXT 4.0 Ah battery from Makita delivers up to 60 A, I think I should be ok.
Looking at the table from Mooch... he didn't really test 15 A draws. Likely because it's not a common output current draw for 21700s. I guess I could look at 10 A tests, the LXT 6.0 Ah only outputs 30 A, so maybe I'll be ok. Samsung 50S would be best for me, and give me an E-score of 13.7*3 or 41.1. They also have the highest rating at 20 A of 11.4

I strongly recommend sticking with the kits I linked in the other thread. I haven't found another product that comes close to the quality of the housing or BMS board. That one you linked appears to have a housing made from ABS, and the board has numerous deficiencies. A cursory look shows poorly chosen mosfets and a complete lack of high-current traces on the PCB.

When I received the first battery I ordered from Amazon based on these kits I opened it up, examined each component under a microscope and looked up their datasheets to verify their specs. Then I reverse-engineered some of the more vital areas to make sure they would function as intended. I did all of this before attaching the battery to a tool or putting it on a charger.

Modern lithium cells can be incredibly dangerous if mistreated. You do not want to find out what happens if you connect them to a faulty or substandard BMS board.

Also, I don't think a 5S3P case will fit in the mower, at least not in bank 1. You'll definitely have to remove the lid.

There are some cases that accept 20 18650 cells.

Those definitely won't fit in the mower.

So it looks like 15 21700 cells is the winner and Samsung 50S. I'm not sure if I did this right?

Samsung 50S cells aren't bad, but they will be more stressed than the P45B cells I used. I personally don't think the extra 10% capacity up front is worth the accelerated degradation.

It looks like you used Molicel P45B in a 5S2P configuration. How's that performance compared to the stock 5.0 Ah battery? Wow! Those cells can output 45A, so you could get out 90A. Obviously there's some braking point, where the lawn mower isn't going to asking for more current. Does your lawn mower spin really fast, or the wheels in self propulsion compared to the stock 5.0 Ah battery that could only output 40 A? I assume it's pretty much maxed out and is drawing all the current it can ask for. Those are some high output current cells!

The mower doesn't spin faster, since the speed controlled by a computer. What the higher current batteries do is allow it to maintain a higher blade speed under heavier loads. It is FAR more resistant to bogging down and/or stalling out, even more so than my old Honda gas mower.

 

[YoshiMoshi3]

That's a lot of batteries. How did you manage to collect 15 of them?

Yea I think that's right. Higher continuous discharge current cells, tend to have lower internal resistance and can run cooler at lower resistances.

I think this is the original BMS board from a genuine Makita battery.. They seem to cover the whole board in some sort of epoxy resin.

The BMS board from the Amazon knock off from your project.

The ones from Ali knockoff for 5S3P. They do look a bit different!

I can't find the case only with the BMS you have in your battery that you got off Amazon.

Yea I would imagine if your 5S2P battery won't fit in the lawn mower, 5S3P wouldn't fit, the lid would need to come off.

I wonder what the maximum current draw of the lawn mower is, I guess we will never know.

When you hooked it up, did you assume worse case that all 90A would be consumed, and picked sufficiently thick nickel strips? I highly doubt that 90 A would be drawn, but without knowing the maximum current, don't know how thick they need to be.

Thanks!

 

[Rabid Badger]

That's a lot of batteries. How did you manage to collect 15 of them?

I got them in bundle deals with tools. 2 came with my drill and impact driver, 4 with one of my circular saws, 4 with my mower, 4 with my leaf blower.

I think this is the original BMS board from a genuine Makita battery.. They seem to cover the whole board in some sort of epoxy resin.

That's conformal coating, it's there to protect the board from corrosion, but Makita lays it on extra thick. If you look at the board from the battery I built, it has some as well. The board from the kit you were looking at doesn't have any at all.

I can't find the case only with the BMS you have in your battery that you got off Amazon.

Copy and paste this link into your browser:

https://www.aliexpress.us/item/3256806803364276.html

Clicking won't work, the forum breaks the link.

Yea I would imagine if your 5S2P battery won't fit in the lawn mower, 5S3P wouldn't fit, the lid would need to come off.

Even with the lid off, you couldn't put them in bank 1. They'd hit the front wall of the battery compartment before they locked in.

I wonder what the maximum current draw of the lawn mower is, I guess we will never know.

The new batteries definitely aren't working hard to keep it going, so I'd guess somewhere between 40-50 amps under heavy load. More than the factory batteries can deliver, but not enough to make the P45B's sweat.

When you hooked it up, did you assume worse case that all 90A would be consumed, and picked sufficiently thick nickel strips? I highly doubt that 90 A would be drawn, but without knowing the maximum current, don't know how thick they need to be.

I used the tabs that came with the kit. Then I overlaid them with some 0.15mm pure nickel strips I had on hand, just to be safe.

If you do this to your batteries, be careful. I recommend putting some tape over the contacts you aren't currently welding, because if you accidentally drop a strip in the wrong place it will cause a short circuit and weld itself in place before you even realize what's going on. The welds will vaporize almost immediately, but you will burn the **** out of your fingers when you grab what's left of the strip to get it off the battery. Ask me how I know.

 

[engineer2]

DOH! I didn't know Makita had a 36V system.

 

[Rabid Badger]

DOH! I didn't know Makita had a 36V system.

Me either!

 

[Rabid Badger]

Alright, I've designed a 3D printable latch that will allow the battery door to lock closed over a full complement of 5S2P 21700 batteries.



The model can be downloaded here:

Printables

www.printables.com

If you don't have a printer...get one. A machine that would have cost $800 2 years ago can be had for $159:

https://www.bhphotovideo.com/c/product/1778934-REG/creality_ender3v3se_ender_3_v3_se_printer.html

 

[duneslider]

Curious but what spot welder do you have for welding tabs to the batteries? Been looking at them but there are a lot of options out there and I am still a bit gun shy on the Chinese stuff.

 

[Rabid Badger]

Curious but what spot welder do you have for welding tabs to the batteries? Been looking at them but there are a lot of options out there and I am still a bit gun shy on the Chinese stuff.

I built my own back before they were a commodity.



These days you can get a perfectly functional welder for less than I spent on the chromium copper rod I used for my stinger tips.

https://www.amazon.com/Seesii-11000mA-h-Upgraded-Enhanced-Adjustable/dp/B0BJ6FRPKR?tag=atomicindus08-20

https://www.amazon.com/WESTOBiG-Combination-Adjustable-0-1MM-0-25MM-Stainless/dp/B0D49F7LKH?tag=atomicindus08-20

Either of those would get the job done. I'd probably go for the Seesii. It has a bigger battery and a simpler UI.

 

[YoshiMoshi3]

@Rabid Badger I found the dimensions of the 15 21700 case on Ali. I'll go take a measurement and see how close it is in slot 1.

Also did you evaluate use the "pouch" cells? I don't think they are necessarily better, as the lithium phosphate cells have a lower energy density I believe.

Looks like 3 and 3/4 inch, so yea likely won't fit.

 

[Rabid Badger]

@Rabid BadgerAlso did you evaluate use the "pouch" cells?

Pouch cells don't really offer any advantage over high capacity tabless/multi-tab 21700s. All the next gen batteries are based on tabless cylindrical cells.

 

[YoshiMoshi3]

Pouch cells don't really offer any advantage over high capacity tabless/multi-tab 21700s. All the next gen batteries are based on tabless cylindrical cells.

Ah have you thought about measuring the thickness of the wires coming from the battery connector from within the mower, to see how much current can safely be consumed by the mower?

 

[Rabid Badger]

Ah have you thought about measuring the thickness of the wires coming from the battery connector from within the mower, to see how much current can safely be consumed by the mower?

Nah. Makita over-engineers and underrates their tools. I also firmly believe these mowers were designed with 21700 batteries in mind. They could have made it smaller and lighter, otherwise.

 

[YoshiMoshi3]

@Rabid Badger

I took a sneak peak underneath the battery panel.

The negative wire measured 2.5 mm. The two red wires were 3.2 mm and 2.3 mm.

Very interesting. So one power wire appears to be 11 AWG wire at the maximum, when taking the insulation into consideration.
The other power wires appear to be 9 AWG and 12 AWG.

It looks like the maximum current through 11 gauage wire is somewhere between 20-30 A. So I suspect the lawner mower draws a maximum of 30 A.

 

[Rabid Badger]

@Rabid Badger

I took a sneak peak underneath the battery panel.

The negative wire measured 2.5 mm. The two red wires were 3.2 mm and 2.3 mm.

Very interesting. So one power wire appears to be 11 AWG wire at the maximum, when taking the insulation into consideration.
The other power wires appear to be 9 AWG and 12 AWG.

It looks like the maximum current through 11 gauage wire is somewhere between 20-30 A. So I suspect the lawner mower draws a maximum of 30 A.

10AWG with 105C insulation is good for 60 amps, especially on a short run like that.

 

[YoshiMoshi3]

10AWG with 105C insulation is good for 60 amps, especially on a short run like that.

how do you know it's 105C insulation

 

[Rabid Badger]

how do you know it's 105C insulation

Because that's what a responsible engineer would use. But since I don't like having egg on my face, I looked and the wiring in my mower and it's actually 125C insulation.

 

[YoshiMoshi3]

Because that's what a responsible engineer would use. But since I don't like having egg on my face, I looked and the wiring in my mower and it's actually 125C insulation.

The batteries are in series?

 

[Rabid Badger]

The batteries are in series?

Yes.