Wiring 2 m18 batteries in series…

[allinon72]

Got my son a ride on toy for Christmas, 24v, of course a very cheap 7ah battery. I want to make it slightly faster with changeable batteries

On his last 12v Peg Perego, it was as simple as adding a Milwaukee m18 battery with a voltage regulator and dialing the voltage down to a manageable 14-15 volts. That protected the motors from damage and still provided a much faster speed and longer run times.

Question on a 24v system - is it as simple as adding 2 m18 batteries wired in series with the same voltage regulator, dialed down to 28-30v? I would probably get a pair of 6ah m18 batteries.

Or, would I be better off just getting a bigger lithium 24v battery in the 10ah range?

 

[RegeSullivan]

If you already have the charger I'd bet the 24v lithium would be the less expensive way to go per AH. Plenty of choices today in the 24v range but most are higher AH than 10. Might need to use 2 12v in series to keep the cost down. Some of the odd size batteries are stupid expensive.

 

[CraigStu]

Two garden tractor 12V batteries in series so no need for a regulator?

 

[PoorUB]

Question on a 24v system - is it as simple as adding 2 m18 batteries wired in series with the same voltage regulator, dialed down to 28-30v? I would probably get a pair of 6ah m18 batteries.

I question if two 18v Milwaukee batteries on series would even work with the electronics inside the battery.

A couple 12v batteries in series seems like the best idea to me.

 

[whateg01]

Two garden tractor 12V batteries in series so no need for a regulator?

Lawn and garden batteries are usually bigger than the batteries that come in the ride on toys, and op would have to for 2 of them in that space. Whereas a couple tool batteries will easily fit in the original battery compartment.

 

[Mandres]

I question if two 18v Milwaukee batteries on series would even work with the electronics inside the battery.

That's the big question mark. The BMS inside the Milwaukee packs might freak out if they see a 24v load. I don't know enough about them. I have seen projects where people are running ebikes off of tool batteries but I don't know at what voltage or if modifications were required

 

[whateg01]

Iirc, recent discussion about the bms determined that the bms is in the tool. DeWalt has a charge indicator in the battery but it's not a bms.

 

[johnnn]

Makita batteries bms will brick themselves under certain situations.

 

[CraigStu]

Lawn and garden batteries are usually bigger than the batteries that come in the ride on toys, and op would have to for 2 of them in that space. Whereas a couple tool batteries will easily fit in the original battery compartment.

Good point but dang the system would be simple if it could fit. BTW what is BMS

 

[Firebrick43]

That's the big question mark. The BMS inside the Milwaukee packs might freak out if they see a 24v load. I don't know enough about them. I have seen projects where people are running ebikes off of tool batteries but I don't know at what voltage or if modifications were required

Milwaukees M18 don't work that way. There are two dumb power terminals that you can pull out of off of a tool and it won’t stop you, even from pulling down the cells to the point you are damaging them.

The tool itself on the m18 system is what shuts down, cutting off based on the voltages the other terminals and that’s it. Most of the BMS and it’s circuitry is used for charging

 

[rslaback]

Two garden tractor 12V batteries in series so no need for a regulator?

The issue with using garden tractor batteries in these applications is that they leak acid if a kid flips the toy. That is why they have always been traditionally sealed lead acid and now are moving to lithium.

 

[rslaback]

Good point but dang the system would be simple if it could fit. BTW what is BMS

A BMS is the battery management system. It is the circuit board that monitors the charge and discharge for a lithium system. In order to not explode and catch on fire a lithium system needs to charge evenly and discharge evenly. A BMS monitors each cell as well as the entire battery and if it sees a discrepancy from a bad cell or cells it shuts down the battery. It also functions as the battery cut out making sure to not discharge any cells to the point where they cause damage.

 

[JasonMcElroy]

The issue with using garden tractor batteries in these applications is that they leak acid if a kid flips the toy. That is why they have always been traditionally sealed lead acid and now are moving to lithium.

Sounds like getting the AGM or even gel version of a 12V tractor battery might solve this.

I haven't used a flooded battery with fill caps in years.

jason

 

[ArcReactorKC]

I can confirm that I have used M18 batteries in series to get 36v without an issue. I HIGHLY suggest some kind of BMS to make sure you don't pull them too low and damage the cells though.

For reference M12 will do this also.