Lawnmower batteries for ebikes?

AstroKat · Jan 10, 2017

Starting a new topic... so as not to hijack others too much... :oops:

I'm wondering if Li-Ion replacement batteries for consumer mowers, blowers, trimmers, et al, are suitable for low-end ebikes? It seems that 48v 4ah Li-Ion batteries can be purchased for around $100, or less, from large hardware outlets like Home Depot.

Ykick · Jan 10, 2017

I've got one of the 4Ah EGO packs. The stock charger is HUGE but they can be charged through the output port using other chargers. Connections can be kinda skanky since it's all proprietary plastic hardware. Search in my posts "lawn" "tool" "packs" and there's probably more detail that I'm unable to dig into right now.

I pulled about 3.7Ah from the pack. Pretty decent C Rate. They're 14S voltage so 58.8 is the top charge.

AstroKat · Jan 10, 2017

Yeah, it could be more work to access the connectors than to build a new battery... :roll:

Where I'm going with this is that I have just received my replacement ebike kit from Amazon (48v 1000w, supplied by AW). It's almost exactly the same as the first one, except that the supplied bungee cord is red with green stripes and the original was green with red stripes. They must not waste any yarn in that manufacturing facility!

The entire kit was just over $200, so it's hard to justify several hundreds of dollars for a compatible battery. If the kit included a battery and was $1,000 then I would not be trying to build it, nor posting here...

mark5 · Jan 10, 2017

AstroKat · Jan 10, 2017

Thank you! Was this a list from another post or a sticky? If so, sorry to make you post it again...

mark5 · Jan 10, 2017

They're just bookmarked links, that I collect, to other people's work.

AstroKat · Jan 10, 2017

Got it!

I try to look for relevant posts on forums before asking what might be a really stupid question but it doesn't always work out that way...

spinningmagnets · Jan 10, 2017

I also have an EGO 56V (labeled) string trimmer/weed wacker (verified 14S). Very happy with it. The Echo brand 58V cordless power tools are also verified to be 14S.

The Snapper brand 60V tools are 15S.

The DeWalt 20V/60V "Flexvolt" packs have 15 cells. Depending on the DeWalt interface that you plug it into, it auto-configures as either 5S/3P (typically called 18V), or 15S/1P to run the more powerful tools in their lineup.

15S voltage is 3.6V X 15S = 54V nominal, and when fully charged it is 4.2V X 15S = 63V

AstroKat · Jan 10, 2017

Thank you @spinningmagnets! I read some of your articles on other sites before I landed here.

I only just unboxed the replacement motor and mounted it. I'll try it with the SLA batteries and report back...

Sunder · Jan 10, 2017

spinningmagnets said:
The DeWalt 20V/60V "Flexvolt" packs have 15 cells. Depending on the DeWalt interface that you plug it into, it auto-configures as either 5S/3P (typically called 18V), or 15S/1P to run the more powerful tools in their lineup.

If someone can please make one of these with a large number of cells that has a high number of factors (say 144) So that I can have anything from driving my car (72S2P) motorcycle (36S4P) eBike (12S12P) to my dad's farm inverter (6S24P), I will seriously be like:

amberwolf · Jan 11, 2017

spinningmagnets said:
The DeWalt 20V/60V "Flexvolt" packs have 15 cells. Depending on the DeWalt interface that you plug it into, it auto-configures as either 5S/3P (typically called 18V), or 15S/1P to run the more powerful tools in their lineup.

I expect this is done in the connector itself, as a set of interconnecting blades, kinda like how people have used plug sets on their RC packs for charge (parallel) or discharge (series/parallel) configurations. (I wonder if that's where DeWalt might've gotten the idea?)

Not completely relevant to the thread :oops:

but sometimes we also use our ebike batteries to run our tools/mowers/etc.

(I have an experiment planned to happen next week to see if my B&D corded mower will run off my seriesed ebike packs, and for how long; I don't know if it's even a motor type that will run on DC, but we'll find out then.

)

craiggor · Jan 11, 2017

Here's my connector I made for my 36v4ah lawn mower battery using plastic kitchen choping board.

wooden prototype

they just push on and lock in place like you would attach a battery to a tool.here is a simple one that has rubber bands to hold it in place

more info on the pedelecs fourum small battery bargain thread.here is one made on a 3d printer

dogman dan · Jan 11, 2017

That's a cool home made plug.

Back to the 1000w kit. I would suggest that 4 ah is not big enough to run a larger more powerful controller that comes with the 1000w kits,, It's likely 25 amps,, possibly even 30amps.

The mower battery,, at least in the form of one of them, more suitable for a tiny motor and controller,, under 15 amps.

Three in parallel would be 12 ah,, and should more able to run a larger motor/controller. But then it's 300 bucks.

AstroKat · Jan 11, 2017

Very cool but wouldn't it have been easier to take the battery apart?

craiggor · Jan 11, 2017

Didn't want to void the 2 year guarantee. If they died I was going to take them back and say I only trimmed my neighbours bush a few times lol

AstroKat · Jan 11, 2017

:lol:

999zip999 · Jan 11, 2017

Batteries are the expensive part of the build. Cheap dont last as money down the drain

AstroKat · Jan 11, 2017

Sorry if this is a stupid question but what if the battery is a lower voltage (e.g. a 40v lawn mower battery with a 48v controller)? I know brushless motors will take a wide range of voltages but obviously you can't put a 48v battery on a 24v controller.

Will a 48v controller function at a lower voltage (even 36v or 24v) and what does it do? Does it supply the same amps at the lower voltage?

Voltron · Jan 11, 2017

Usually the controller will cut out from the lower voltage, thinking its protecting a 48v battery from getting drained too far. It might work with the right 36v controller ( most, but not all, 36v controllers will handle up to 60ish volts), esp if the battery has an internal BMS to cut it off at a safe discharge point so you don't kill the battery by accidentally running it down too far.

spinningmagnets · Jan 11, 2017

Most electrical devices have a Low Voltage Cutoff (LVC), and that protects the battery pack from being drained down so low that it is damaged. A fully charged 48V battery has enough voltage that it can likely run a 52V component, but it will only run a short time. Once it drains down just a little, it will hit the 52V LVC, even though it still has plenty of 48V range left in it.

ha ha, we were both typing the same answer at the same time.

AstroKat · Jan 11, 2017

Yep, you guys are right. I just tested it by taking one of my 12v batteries out of series to drop our 48v kit down to 36v and nothing. I even reprogrammed the LCD to tell it the battery was 36v and still nothing.

AstroKat · Jan 11, 2017

I see 36v/48v controllers that look VERY similar to what came in the kit: https://smile.amazon.com/Brushless-Controller-Regenerative-Function-Electric/dp/B01N955I2G

I wonder if the controller is switchable inside? How would it know, otherwise?

Voltron · Jan 11, 2017

On some of the newer ones it can sense the input voltage and self adjust, and some have an external switch. Older ones required resoldering a jumper inside, or weren't switchable at all. That one requires the optional display to do the regen, might be worth checking if its required for switching the voltage too or if it auto selects.

AstroKat · Jan 11, 2017

OK, good to know, thanks! This is an experiment and all good fun (until someone loses an eye, as my mother would say)... :roll:

There are no external switches but I''ll take it apart and check for jumpers, etc. Although, the supplied LCD didn't even come with a manual so I'm not confident of finding the correct jumper.

AstroKat · Jan 11, 2017

Here's a pic from my phone of the controller's board. No obvious switches or jumpers...

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