How to charge 40v lawn mower

[Bryan C]

Hey everyone!

I’m brand new so please take it easy. I have a 40v electric lawn mower that I’d like to charge with solar. Every time I search this it’s a standard 12v battery that people hook up straight to a panel. I’d like to keep the charger that came with this.
I’d also prefer to not use a battery bank but I’m open.
The way I THINK it should go is
Solar panel
Charge controller
Inverter
Battery charger
Battery

I realize that’s not efficient but it will have a week to charge and it charges in the house in under an hour.

My question/concern is what happens when there isn’t enough power coming in from the solar panel? Will it be safe and shut down?

Thanks!

 

[A.Justice]

It would be way easier to add a small battery as a buffer, a brief cloud or shade could completely screw up your charging.

A small sealed lead acid battery would probably be your cheapest option.

 

[Bryan C]

So like this but my load would be an inverter that I plug my 120v charger into?
Excuse my ignorance here as I’m new to all of this but is it the charge controller that shuts down if it’s not putting out a pre-set amount of power?

 

[A.Justice]

So like this but my load would be an inverter that I plug my 120v charger into?
Excuse my ignorance here as I’m new to all of this but is it the charge controller that shuts down if it’s not putting out a pre-set amount of power? View attachment 92841

The load would come directly off the battery rather than out of the SCC, but yes, that's the general idea.

The charge controller will put as much current as the panels are producing into your batteries (within spec, obviously). The issue with running no battery would be that if a cloud passed over, the controller wouldn't put out the required amperage for the inverter, and that can cause all kinds of problems. Plus, controllers like that are designed to be used with a battery, you could pretty easily fry an SCC without a battery, unless it's specifically designed for that purpose.

 

[DThames]

The load would come directly off the battery rather than out of the SCC, but yes, that's the general idea.

The charge controller will put as much current as the panels are producing into your batteries (within spec, obviously). The issue with running no battery would be that if a cloud passed over, the controller wouldn't put out the required amperage for the inverter, and that can cause all kinds of problems. Plus, controllers like that are designed to be used with a battery, you could pretty easily fry an SCC without a battery, unless it's specifically designed for that purpose.

Yes (to the O.P) you should have a battery to power the inverter. If you get a battery with about twice the watt hours as your mower battery, you solar charged battery should be able at any time of the day to charge your mower battery. Then when you have the sun, the inverter battery will recover for the next mower charge.

 

[gdawg]

Thanks for starting this thread as I am wanting to do the same thing. I have an EGO 56V mower with 7.5ah battery. Also, I have a bunch of other outdoor cordless tools like a trimmer, blower, hedger, etc. My thought was to mount a solar panel on my shed, and then add in the charge controller, a 12V lead acid battery (AGM style which I have just sitting around), and then an inverter to plug the EGO charger into. Hopefully I could add some LED lights out there, kind of making the shed into a small workshop.

What are the best options to get started? Is a kit the best way to go? Or buy individual parts? I think being able to just charge the mower up from the solar panel would be very cool and a great first project. Thoughts?

 

[Substrate]

I'll let you do your homework on what you eventually up with, but will emphasize this:

Those tool chargers may be very simple or very smart. In either case, what they are expecting to see on their AC input, is a PSW or pure-sine-wave. So make sure that if you use a system that incorporates an inverter, make sure it is PSW and NOT a "mod-sine" or modified sine-wave.

Some tool chargers use the pure sine wave as a clock reference, timer, or other internal function to figure out if the tool batteries are fully charged, damaged, need diagnosis, etc. Using a cheap mod-sine inverter can fool these capabilities, and you end up hurting the tool batteries.

Do NOT be misled by cheapskates, salesman, or others with shade-tree advice to buy some puky little inverter off the shelf from your local auto-parts store.

 

[gdawg]

@Solar addict, thanks for your reply. Yes, I was looking at going with a PSW inverter for sure since I don't want to damage any of the electronics I might plug into it. Overall, do you think that a single solar panel and 12V AGM battery should be sufficient for a beginner system? I have a couple 100 ah AGM type sealed batteries that I'm not using, so I can use one of those.

 

[Substrate]

Sure, but what worries me is that as a beginner - especially using agm lead-acid laying around, you may not have the skills to recognize if you are shooting yourself in the foot with a poor old battery. Nor what it takes to maintain them properly and the required solar power / insolation to do so - and that's starting from *new*.

In other words, you could be lead down a path of spending a lot of good money after bad - and worse yet, not learning anything due to faulty battery(s).

But, to help alleviate this, and at this skill level, if you actually felt inclined to determine if what you have is even viable for learning from, I recommend this charger to do so - because it uses a lot of tricks to try and save batteries - but most importantly - will give up and notify you faster than others if you are wasting your time!

Tecmate / Optimate 7

TecMate – OptiMATE 7 AmpMatic

tecmate.com

You can nerd out like I do and interpret the blinky-lights. Or walk away and come back later and see if it has signalled that your battery is trash, and tell you so. From nerds like myself to Grandpa, it's a time-saver for sure so you simply recycle junk, rather than play with it.

But here's the problem: $$ If your time is valuable, and you want to make sure what you have is even remotely workable, you might learn something from your batts.

Tip: screenshots from these to vendors rarely get questioned if there is a claim. Shots from a 1970's Sears charger - not so much.

Overall, yes a single panel, controller, and agm is fine. But too often the beginner doesn't know his battery is already toast, learns nothing from damaged goods, and gets led down an expensive path from schysters.

This would be my very first step with that charger, so you don't waste time, energy, or even more money down the drain from the start.

 

[Bryan C]

Hey guys, checking back in. The new shed is on the way which will house the mower and solar kit.
Mower battery is 40v 5ah battery which is 200w right?
Charger input is 120v 1.3amps so 156w right?

I want to make sure I’m understanding this as I build it. But technically a 200w inverter would be good enough? Though I’m looking at a 1,000W pure sign wave inverter incase I want to add lights or anything.

https://www.amazon.com/dp/B07JMQ27WJ/ref=cm_sw_r_cp_api_i_PWSRN2ZB9FQDFKWRRQBM?_encoding=UTF8&psc=1

And how should I size the battery? 5x bigger than my total draw? So as to never use more than 20% of the battery? Now I don’t even use half my mower battery so not even 100w of power but I’m looking at this battery from Walmart which is LiFe PO4 12v 100ah deep cycle. So that’s obviously 1,200w of power and way more than enough.

https://www.walmart.com/ip/386084520

And finally this panel and charge controller:

https://www.amazon.com/dp/B00BFCNFRM/ref=cm_sw_r_cp_api_i_5CH4T4VYMG8MP1SJZ1GH

Thanks for your help guys!

 

[Bryan C]

Yes (to the O.P) you should have a battery to power the inverter. If you get a battery with about twice the watt hours as your mower battery, you solar charged battery should be able at any time of the day to charge your mower battery. Then when you have the sun, the inverter battery will recover for the next mower charge.

Could you help me understand, for general knowledge, what happens when power is low. This could be from panel to SCC or low power from battery to inverter.
If the panel is not producing enough meaningful power does the SCC just not push anything at all out?
And more importantly, will the inverter shit down if the battery gets too low?
What I’m really asking is, will the product being charged ever see a voltage or amps that it doesn’t like? What are the protections against this?
Thank you very much!