neuton mower batteries charged with solar panels

solarmower

i would like to buy the neuton c36 battery operated mower seen here:

http://www.neutonpower.com/TwoStepModelDetail.aspx?Name=CEM6-2Model&p1Name=cemnewmodel&Page=CEM6Models

and i would like to charge the batteries via solar power. i don't want to charge the batteries while i'm using the mower. i want to have a charging station set up in my yard where the batteries are charged and i just disconnect them to use in the mower.

can anyone help me with how to do this? i have no idea where to start and have no understanding about solar panels or electricity in general.

i would like to set my 11yo son up with a solar lawn mowing business using this set up so it would have to be fairly robust and reliable.

thank you for your help.

Cariboocoot

Re: neuton mower batteries charged with solar panels

Welcome to the forum.

There are a couple of problems with this project, although not insurmountable.

First is that it is rather impractical. The cost of producing the energy to charge the mower from solar will be significantly higher than buying it from your utility.

Second is that charging the battery directly presents some technical difficulty in getting the solar charge controller specifications to meet the needs of the battery. For one thing it is 36 Volt, and that is a non-standard Voltage for renewable energy use. This means you end up having to use a more expensive programmable charge controller. And then you have to deal with analyzing the charge profile to get proper charging Voltage/current/time.

A much easier way of doing this would be to use the charger that comes with the mower and plug it in to an inexpensive 12 Volt inverter that has its own battery/controller/panels. More expensive and less efficient than trying to charge the mower battery directly, but far easier to achieve. It will also avoid the problem of not being able to recharge the mower after using it during the day due to a lack of sunlight to power the charger.

And you could use the set-up for other solar experiments as well.

solarmower

Re: neuton mower batteries charged with solar panels

thank you for your reply. i am a complete newby to all of this and i have no idea what/where to purchase the pieces of equipment you suggest. could you help me in sourcing the 12v inverter and the solar panels needed to supply the power? and a source of how to hook it all up? is there an off the shelf product that i can buy that will achieve what i am looking to do?

thanks again

Cariboocoot

Re: neuton mower batteries charged with solar panels

What you will need to do is look at the power requirements for the mower's charger. You have to be able to supply its peak current demand and the Watt hours it would take for a full charge.

So to recharge the mower requires 'X' Watts (@ 120 Volts) and 'Y' Watt hours. The inverter has to be able to supply the 'X' Watts (probably not too difficult) and the battery has to be able to supply the 'Y' Watt hours (including the inverter demand).

We get some idea of this from the mower's specifications: 36 Volt 10 Amp hour battery and requires 12 hours for a full charge. We do not know the Watt demand of the charger, but it probably is not very large as the battery is only 10 Amp hours and therefor probably would not take more than 2 Amps @ 44 Volts (charging) or 88 Watts. So based on that the inverter would need to be 100 Watts minimum.

Assuming 50% depth of discharge that 10 Amp hour battery would be 180 Watt hours. This should be adjusted to supply the inverter and for conversion efficiency too. A small inverter like the Samlex PST-15S-12A uses about 6 Watts and has 85% efficiency. So the 180 Watt hours becomes 212 Watt hours plus (6 Watts * 12 hours) 72 Watt hours for the inverter. Total 284 Watt hours, or approximately 24 Amp hours used. At 50% DOD that's 48 Amp hour 12 Volt battery to run the inverter. You may find it easier/cheaper to get a 100-ish Amp hour 12 Volt battery.

Normally we recommend against buying the RV/Marine type battery, but for a first foray it may be the least expensive option.

You would then want to recharge the inverter's battery from solar. To do this it's a good idea to have at least 5% of the Amp hours available as a peak current. So the solar needs to put out at least 5 Amps for the 100 Amp hour battery. That is not difficult to achieve. A standard "12 Volt" (Vmp 17-18 ) solar panel of at least 90 Watts will do it; check the Imp rating of the panel. You will probably find something like a 130 Watt Solartech panel that provides 7 Amps would be a good value for this.

You would also need a simple PWM type charge controller capable of handling at least the current of the panel. About a 10 Amp Morninstar Sunsaver for example.

Is this helping?

solarmower

Re: neuton mower batteries charged with solar panels

thank you for your beautiful post cariboocoot. i am going to study it this week to really try to understand everything that is involved.

so what you're saying is that if i were to plug in the battery charger that comes with the mower into the Samlex 150 Watt 12 Volt Sine Wave Inverter, then hook up that up to the SunSaver 10 amp 12 volt solar charge controller which then would hook up to the Solartech SPM130P-S-N 130 Watt Multicrystalline Module 12 Volts i could charge my battery via the sun?

as i am a total newbie (and i thank you for your patience, here), how would i hook up the inverter to the charge controller and how would i hook the charge controller up to the panels? what kind of connections would i need to make and would i have to buy wires and if so what would they be? i'm happy to buy it from the store attached to the forum.

a couple of quick questions: when the battery is charged will the system stop charging it automatically? would it be possible to charge more than one battery (up to 3) at a time? for instance if i put a power strip on the inverter what would i need to change to scale it up for 3 36v batteries? i know that question involves the math but it is beyond me. also, any rule about placing the panels? angle? etc?

i am so passionate about doing this! thank you for your help. (ps i am in north carolina so we get a lot of direct sun)

br

Cariboocoot

Re: neuton mower batteries charged with solar panels

What you would be doing is powering the mower's battery charger with the inverter which runs from the 12 Volt battery, and that in turn is recharged by the sun via the solar panel & controller.

It seems round-about, but you have a case where the mower may take 12 hours to charge but the sun does not shine for 12 hours. So you have to gather all the energy needed to charge the mower during the time the sun does shine and store it in the 12 Volt battery for use as needed.

So you have three separate but interacting circuits: the solar panel & controller charging the 12 Volt battery when the sun is available; the 12 Volt battery powering the inverter when it is needed to run the mower charger; and the mower charger recharging the mower battery. Since both battery charging sections are regulated there is no danger of overcharging either one.

If you were to scale up to handle more mower batteries or additional lawn equipment (battery powered trimmer for example) you would need to figure out the Watt hours for each, use the conversion factor for the inverter (85% for the one I mentioned) and add that to the 12 Volt battery capacity. If the combined draw is larger than the inverter can handle it would have to be increased and any differences in efficiency and self-consumption included. Once the final 12 Volt battery size is determined the solar panel & controller need to be sized to meet the needs of the battery.

Angle of the panel(s) is important: they produce maximum power when pointed directly at the sun. As such with a fixed mount the output looks like a bell curve as the sun angle becomes more direct in relation to the panel and its output goes up, then down as the sun declines in the West. This is why we look at 'average' output from a panel over "hours of equivalent good sun". As such a 130 Watt panel may peak at 130 Watts but on average it will produce 100 Watts for about four or five hours per day. Often people think they get "10 hours" of sun, but even with the panels on a tracker this will not provide consistent output as the atmosphere is denser in the morning and evening so you still get a bell curve of power output. With panels so cheap these days trackers are rarely worth the investment.

solarmower

Re: neuton mower batteries charged with solar panels

cairboocoot

thank you again for such a clear and readable answer. a couple of questions: does the Samlex PST Series Pure Sine Wave Inverters: Samlex 150 Watt 12 Volt Sine Wave Inverter that you mentioned include the 12v battery? (i'm assuming it does) or do i buy that separately?

the connection between the mower charger and the inverter is clear to me (just an electrical plug) but how does the inverter connect to the charge controller and the charge controller connect to the solar panels? do i need to buy wires or are they included in the items you mentioned?

i was hoping you could help me with the math for scaling this up to use with 3 of the 36v mower batteries. i've contacted the company and here are the specs for the batteries: here is what they say

"The battery is made up of three 12V 10AH batteries wired together to make up the 36 volts. The output of the ASO (automatic shut off) charger is about 40V DC with .7 ah output. This would be about .028 kWh - with a 12 hour charge this would be about .336 kWh. Please be aware that leaving a charger on the battery after it has been fully charged could over charge the battery and shorten it's life. Also the amount of electricity needed to charge the battery could depend on how depleted the battery charge is. This is why we recommend the ASO charger as it checks the charge level and shuts off when charging is complete."

given the specs of the batteries above, how would i need to change the set up you suggested earlier to charge 3 of the 36v batteries simultaneously.

i'm hoping to make this project happen with a kickstarter grant to fund a green lawn mowing business for my 11yo son. our neighborhood has mostly 1/3 an acre lots or less which is perfect for this mower.

thank you again, for your help. i am motivated by the knowledge that for every hour my son mows lawns with the solar powered lawn mower he is effectively saving the environment the equivalent of the emissions output of 11 cars running for an hour (which is the estimated emissions of a standard gas powered lawn mower running for an hour).

Blackcherry04

Re: neuton mower batteries charged with solar panels

This is a good one, a Grant to prove you can spend $2000 dollars to save $.10 cents worth of electricity.

solarmower

Re: neuton mower batteries charged with solar panels

$.10 worth of electricity and 88 lbs. of the greenhouse gas CO2, and 34 lbs. of other pollutants into the air every year not to mention the over 17 million gallons of gas that is spilled each year refueling lawn and garden equipment – more oil than was spilled by the Exxon Valdez.

Blackcherry04

Re: neuton mower batteries charged with solar panels

solarmower wrote: »

$.10 worth of electricity and 88 lbs. of the greenhouse gas CO2, and 34 lbs. of other pollutants into the air every year not to mention the over 17 million gallons of gas that is spilled each year refueling lawn and garden equipment – more oil than was spilled by the Exxon Valdez.

Opp's you forgot the 1,800 lbs of Green House Gas and 900 lb of other pollutants it took to manufacture all the solar equipment mower and those batteries. Not to mention all the Oil. You end up with a net loss, look it up.

solarmower

Re: neuton mower batteries charged with solar panels

but we will never achieve the ability to one day manufacture the equipment cleanly if nobody takes the initial steps to embrace and develop solar energy!

Cariboocoot

Re: neuton mower batteries charged with solar panels

Okay let's just avoid the philosophical debate. Obviously this is not being done to save money nor is it going to save the world. But if some of us hadn't spent $10 per Watt on solar panels years ago no one would be buying them for $1 per Watt now.

Back to tech.

The small Samlex inverters (and many others of the type) have built-in electrical outlets the same as any wall plug. The DC side is hard-wired to the 12 Volt battery (not included - you need to get the size that suits for your use) through a fuse. The charge controller is also hard-wired to the battery (through a fuse - overcurrent protection is cheap insurance) and the panels are connected to the input of the charge controller.

The ideal way to check that mower charger would be to run the mower down, then plug it in for charging through a Kill-A-Watt meter. That will show not only the current being drawn @ Voltage but also the accumulated Watt hours. You can't do any better than measuring the device in question; manufacturer's information is sometimes inaccurate.