Solar Charging a 48V go kart

Functional_Artist · July 2018

Hello all,

I build electric go karts. Here is one of them. https://www.youtube.com/watch?v=uBMA10WYGsI

I am interested in setting up a solar battery charger for them.

The batteries I am using are (4) 12V 12AH SLA's. I would like info on how to properly set up a 48V solar battery charger.

I have looked @ these "cheap" 100W panels from Harbor Freighthttps://www.harborfreight.com/100-watt-solar-panel-kit-63585.html but, as I understand they are for or to charge @ 12V.

Would I need (4) of them ($600.00-$800.00), wired in series, to charge my 48V battery packs?

Any suggestions on "better" alternatives?

Location: Toledo, Ohio USA

Thanks in advance

BB. · July 2018

Don't get those Harbor Freight panels... They are not very good.

The only off the shelf 48 volt battery "boost" controller that I know of is this guy "GVB-8" 8 amp charger:

https://genasun.com/all-products/solar-charge-controllers/for-lead/gvb-8a-pb-solar-boost-controller/

You will probably have to contact Genasun directly to confirm what the input voltage range is... I believe it can take Vmp~30-36 volt panels... I am not sure it can take a 12 volt panel for 48 volt battery charging directly.

One charge controller and one ~200-350 watt panel and it could give you an alternative to 4x 140 Watt "12 volt" (Vmp~18 volts) set of panels.

Normally, >200 Watt Vmp>=30 volt panels are 1/2 the cost ($$$/Watt) of 140 Watt Vmp=18 volt panels.

The other question is how much current do you need to recharge your batteries... Normally, 10% to 13% rate of charge would be the nominal charging current (1.2 amps to 1.6 amps for a 12 AH battery bank). Higher than that could start to give you battery bank overheating issues. For example:

12 AH battery * 58 volts charging * 1/0.77 panel+controller derating * 0.10 rate of charge = 90 Watt nominal solar array

I don't know if the GVB-8 can recharge a 48 volt battery bank from a single ~90-140 Watt Vmp~18 volt panel.

-Bill

Functional_Artist · July 2018

Thanks for the reply & the link to the "boost" controller.

I mentioned the Harbor Freight panels, just as an example, to help begin the conversation.

The battery chargers that I, usually, use to charge these 48V battery packs (4-12V 12AH batteries) have an output current of 1.5A - 2.5A

The Genasun specs says

...that it should work with almost any panel that is below your battery's voltage

…& that it puts out 8A @ 12V so, would that be ~2A @ 48V?

So, it looks like it would cost

…~$100.00 for boost controller + ~$300.00 (+) for solar panels & mounting, cables etc.

Total ~$500.00

Man, that kinda blows this DIY solar charging of small Ev's idea "out of the water"

(go karts, golf carts, boats, jet skis, snowmobiles ect.)

How can I employ/promote, solar charging of go karts, if a standard (plug in) 48V 2A battery charger costs ~$20.00

...& if (lets say) it costs $1.00 per charge cycle

It would take like ~500 charge cycles just to "break even"

...if the system gets set it up right, no complications arise & the components perform/last as long as their advertised too

What is the average life of solar panels? 5 years? 500 cycles?

BB. · July 2018

Fun_Artist,

You got it... 4x higher voltage, 1/4 current equals the same amount of power... (Power=Voltage*Current)--Ignoring losses for the moment.

In general, the least expensive (in volume) is to have a solar panel whose output voltage is appropreate for charging the attached battery bank (for a 48 volt lead acid battery, that is around Vmp-panel/array ~ 70-76 volts--Or 140 to 152 solar cells in series). Then you can use a simple PWM charge controller to charge the device(s) in question.

Vmp~70-76 volts are not a common value these days--But given enough demand, I am sure you can find multiple solar panel vendors willing to build something like this for you.

There are downsides with "high(er)" voltage DC systems... Basically they make great arc welders. If you have a failed connection or short somewhere, there will be a very nice arc (aka fire starter):

https://www.youtube.com/watch?v=Zez2r1RPpWY

These days, it it getting pretty cheap to do things in electronics... An MPPT boost controller is not that difficult or expensive these days--You are looking at $100 retail, or probably $40 or so wholesale.

In general, good quality glass + crystalline panels should last 20-40 years--Assuming nothing damages the glass (hail, rocks, dropped, etc.) or rips the rear membrane. And for panels over ~200 watts, you can get them at $0.50 a Watt--A steal compared to 20 years ago when panels cost ~$10 a Watt.

Another issue that we have seen here is that many people want to run the carts/etc. during the day, and recharge at night... Now you are looking at another battery (or set of batteries) that charge during the day and are used to charge the cart battery set at night--Another expense (or have 2 battery banks for the cart, one in cart, second in charging station).

Add that solar charging is dependent on weather/seasonal sun/shade (solar electric panels do not work in full or partial shade).

-Bill

Estragon · July 2018

I'm assuming the carts are individually owned (not part of a track/park multi-cart type of thing)? You want a sort of individual "docking station" so an individual owner can dock the cart and have it charged with solar?

cow_rancher · July 2018

You need a speed control on that go-cart... Also if you have access to an electrical outlet, then Solar is going to be way more expensive to charge your batteries. Now if you are out in the Sand Dunes of Ohio, then it might make sense to use Solar.

Rancher

Functional_Artist · July 2018

Thanks for NOT taking (the end) of my last post, the wrong way ...sometimes I'm way too blunt.

300W x $0.50 = $150.00 for panels plus $50.00 - $100.00 for controller & accessories

...plus a 10 - 20 yr. panel life is "more doable".

Yes, exactly a "Solar Docking Station" (I like that term, sounds kool)

The solar charging go kart idea (I have in mind) is for individuals, who mostly work all day. (the kids are in school)

Here is an example:

a100 lb. kart with a 100 - 150 lb. rider & a 48V 1,000W propulsion system with a 48V 12AH (SLA) battery pack

The battery pack (in this situation) usually lasts ~30 - 60 min (depending on driving style & terrain)

You come home, have supper, get their kart (snowmobile, jet ski etc.) out, have some fun

...then put 'er away (plug it in to the (solar) charger/maintainer) till next time. ...Clean & Green

Yes, I use speed controllers, that was a "Hold on to your Hat" test (part of a series of tests)

I was testing to see if there were any performance differences in a couple different speed controllers

...& also without a speed controller (off of the line was a "hoot" but, in the end the top speed was the exact same)

https://www.youtube.com/watch?v=uG3dvgL_C8M

https://www.youtube.com/watch?v=o4_QJK4mwgw

https://www.youtube.com/watch?v=OAJCPw6KS7g

Estragon · July 2018

Have you considered a lithium based battery? They have the advantage of being able to use more of the overall capacity, have a better power to weight ratio, and are happy sitting partially charged.

If a lead acid battery is run down to a low state of charge and left sitting for long it can permanently impair capacity. This seems likely with a solar docking station if there was a run of gloomy weather. A 48v nominal 12ah battery has about 500 watt-hours of total capacity. With 1000w motor load varying with terrain etc for 30-60 mins, I assume the battery would be at a pretty low state of charge. Being cycled that deeply will be hard on a lead acid battery, and left in that state until solar is available to recharge even more so.

Lithium would be more expensive, but longevity may more than make up for this. Safety could be a concern, with some lithium chemistries more so than others.

Maybe some of those with more lithium knowledge could chime in.

Functional_Artist · July 2018

Very good points, I hadn't thought about the SLA's sitting partially charged overnight. (over & over again)

I'm glad you brought Lithium up. Yes, I have done tons of research on Lithium batteries.

I have just purchased a 2kWh section of a 2015 Chevrolet Volt battery pack for a motorcycle that I converted over to an 8 kW electric motor.

https://www.youtube.com/watch?v=ePoG8xfocEY

https://www.youtube.com/watch?v=nBU6qdzbzdc

but, it's nominal voltage is ~45V not 48V so it needs a "special" charger.

From what I understand,

These 2kWh sections are 45V with a capacity of ~47AH

...they were made by LG Chemical

...chemistry is Lithium Maganese Oxide (LiMg204)

...they have 3 pouches in parallel & then 12 cells in series (3P12S)

...basically, 12 cells in series

Special requirements

Since these battery packs nominal voltage is 45V (3.75V per cell nominal)

The "safe" voltage range of this battery pack is 3.0V per cell (low) to 4.1V (36V low & 49.2 high)

It can only be "safely" charged to ~49V NOT 51V+ like most common 48V chargers will do.

So, it needs to have the top charge (cut-off) set at ~49V

Any info or help on "safely" charging this battery pack will be greatly appreciated

Estragon · July 2018

A solar charge controller (eg Midnight "Kid") should be settable to a 49v limit. Not sure about AC options. Does the pack include a BMS?

Functional_Artist · July 2018

Kool, I'll do some research on the "Kid", thanks

As far as a BMS, the Chevy Volt uses an entire 370V pack BMS & their very proprietary & not really hackable (to use on individual sections)

There are many kinds of "aftermarket" BMS's available with many different features.

But, many of them are kinda "experimental" or cost "way more" than the battery pack their protecting is worth

...& their are a lot of other variables too (# of cells, chemistry, configuration, installation etc.)

After ~6-8 months of research on lithium batteries/BMS's/monitoring & charging, I have found that their seem to be about just as many situations/stories where a BMS was overly relied upon

...or failed (component failure or just failed to do its job) & "actually" killed the battery pack instead of protecting it.

Another reason that I went with the "Volt battery" was, I wanted to stay away from trying to build DIY (home made) battery packs

...again, because their are so many variables from different cell, material & connection resistances, amperage discharge rates etc.

From all of my research, these "Volt batteries" are professionally designed & manufactured & the quality control was set at a such high standard, that could never be duplicated in a home workshop (probably, due to a Zillion dollar contract with GM)

From what I've read, that these batteries are & stay so "balanced" that there are many folks using them on golf carts, motorcycles & lawn mowers (without a BMS) & having great success.

The (2) main parameters are

1.) don't discharge them below ~3.2V per cell (36V)

2.) don't charge them up beyond ~4.0V per cell (48V)

Some have instead used a "Batt-Bridge" to monitor cell balance within the battery

...but, I have not had any success with it

I am instead plan to monitor the battery pack using digital monitors (1) that monitors/displays the entire pack voltage

...& (2) others that will monitor/display each 1/2 of the packs voltage (to monitor balance)

So, to answer your question, no it does not include a BMS

Estragon · July 2018

With the displays, I guess that makes you the BMS

Functional_Artist · August 2018

Yup, I guess your right. (manual BMS)

This isn't really a "solar" question but, just a "charging" question

I ordered a 600W/10A lithium battery charger & asked for it to be "preset" to a 49V top charge.

(for use on my 45V Volt battery)

I ran my motorcycle until the battery was discharged down to ~43V

When I connected the battery charger the voltage level of the battery pack does not increase or change.

I have checked all of the connections & even double checked the (2) fuses in the charger itself.

Any idea why, is it not charging the battery pack back up to ~49V?

Here is a video of my first ride with the "new" lithium battery.

https://www.youtube.com/watch?v=5vRUdxZ334g

Estragon · August 2018

Have you checked the open circuit voltage on the charger output?

Functional_Artist · August 2018

Yes,

While checking the polarity, to connect the charge port, the meter showed 47.6V

...which I thought was odd

Estragon · August 2018

Seems a bit odd to me as well. I know you said you checked all the connections, but problems can be really frustrating to find, and may only appear under load (bigger than the tiny current a multimeter uses). Do you have anything (eg 4 x 12v filament light bulbs in series) other than the battery that could be used as a load?

Functional_Artist · August 2018

Yes,

I can rig up (4) small incandescent, 12V light bulbs in series or I even have a small 48V 1,000W motor available too.

What do you have in mind?

The connections:

I have a female XLR connector "charge port" mounted on the bike. The charge ports positive (+) 10g. wire, connects to the Batt side of the circuit breaker (& then the energy goes via a 4g. cable that's connected to the same terminal, straight to the battery pack positive (+) terminal)

The charge port negative (-) 10g. wire, goes straight to the battery pack negative (-) terminal

Checking the connection:

I get the same voltage reading from the charge port connector, (where the charger plugs in) as I do straight from the battery packs positive (+) & negative (-) terminals.

Estragon · August 2018

I may be confused. Was the 47.6v read at the connector to the battery, or to the charger?

Presumably, the charger should be at 49v. Seeing 47.6v open circuit seemed odd to me, and worth checking connections under some load.

Reading subsequent info, maybe it's the battery voltage at 47.6 (vs 43v after the ride) that seems odd?

mcgivor · August 2018

The voltage is mentioned but no current value or time, the voltage 47.6V may be correct depending upon state of charge, which may remain that way, on a plateau, until the voltage nears full charge value, which can happen rapidly and why a BMS is typically used. Assuming the charger is designed to charge the particular cell type, it should have intrinsic safety built in to prevent over voltage, again it's in the details.

Functional_Artist · August 2018

The battery pack started off at ~49V. While riding, I discharged the battery pack down to ~43V.

To connect the charge port properly, I needed to check the polarity of the charger, find out which pin was positive (+) & which one was negative (-) that's when I got the 47.6V reading (right from the charger output plug)

I assumed the charger output plug would show ~49V but, I'm not sure how this charging stuff works because I've read something about needing to apply a "higher" voltage to get the battery pack accept a charge.

When I attached the charger & turn it on, (1) red light comes on & (1) green light comes on. (like charging is complete)

But, I know charging isn't complete because the voltage meter, on the bike, reads ~43V

...& my multimeter also show that the battery pack has ~43V too

According to the manual, when charging there should be (2) red lights on

...& when charging is complete there will be (1) red light & (1) green light.

I am not sure about current value or time but, I left the charger connected for ~2hrs.

I thought maybe, it takes a minute to kick in or something

...but, after ~2hrs, I checked & the battery pack voltage was still right at the same ~43V

mcgivor · August 2018

What input voltage are you using, the image shows 200-240V

Functional_Artist · August 2018

Hmmmmm, that's wierd

The charger is only a 48V 10A & has a standard looking (3) prong wall AC input plug

I had it plugged it into a regular household wall outlet.

It should be 110V, It doesn't have a big 220V type of AC input plug. (like a clothes dryer or stove)

mcgivor · August 2018

In Asia the same plug is sometimes used as in the one in the US for 120V, but the voltage is 230V , the unit clearly indicates the supply voltage, powered with 120V, the leds may light but have no output. I would suggest using 240V.

Functional_Artist · August 2018

If the charger was set up to run at ~220V AC input & set for a 49V DC top charge

...but, it's only connected to 110V

Wouldn't the charger DC output be reduced to ~1/2 too (like ~24.5V)

Any idea as to why I got the 47.6V reading from the charger DC output plug? (while connected to 110V)

In the USA, how does one connect a 110V plug (on the charger) to a 220V receptacle (on the wall)?

mcgivor · August 2018

It's hard to give a definitive answer to why it was giving an output voltage, electronic circuitry can act in various ways, but what you do know it that it wasn't working. For the receptacle you would need one of these http://internationalconfig.com/icc6.asp?item=5642-I
wired to a 2 pole 15A circuit breaker in the main panel, if unsure or unqualified, I would suggest consulting an electrican.
The plug would need to be replaced as well to match the receptacle, don't use a 120V receptacle, the different pin orientation is to prevent someone plugging a 120V device into a 240v source.

Functional_Artist · August 2018

Ok thanks for ALL of the very useful info.

I ordered/purchased this charger right from the Yewi factory so, I am going to contact them first.

(before I go calling electricians & cutting plugs off of a brand new battery charger)

This should have been a simple plug-n-play situation.

I'll let you guys know how it turns out (I got more questions too)

mcgivor · August 2018

You need the 90-130v version, perhaps they'll exchange it, who knows.

Functional_Artist · August 2018

Hey mcgivor, you nailed it!

I sent them a message about the 200-240V being marked on the charger but, it having a 110V AC input plug.

This was their response:

Dear Kevin,

Sorry for the troubles, the chargers are 220v ac input, we made a mistake on input voltage, and caused the problem.

Do you have electronics engineers which can solder the PCB? It is very easy to change the 220vac to 110vac, just solder a jump wire.

I am very sorry for the mistake, we would like to replace but the freight is too high, can you do the changes? We can provide a discount for next order as compensation.

Best regards,

So, I sent them another message,

I don't feel comfortable with "fixing" my new chargers.

What if I don't do it right? & even if I am successful, I am still relying on a brand new "fixed" battery charger.

Not to be rude but, can you please send me the "right" battery chargers, the ones I "actually" special ordered?

https://gdyunyang.en.alibaba.com/product/60554515544-802552500/CE_ROHS_48_Volt_15A_Fast_Smart_48v_Lithium_battery_charger.html?spm=a2700.details.pronpeci14.9.4a603beeCbFYSo

Yewi UY600

10A lithium battery charger

Top charge preset to 49V

AC input plug- #9 (3-prong USA)

Dc output plug- #E (3-pin XLR)

I shouldn't but, I'll even offer to pay for shipping, me the "right" chargers

Their response:

Hi Kevin,

Sorry for the troubles, we would like to ask you to send the chargers to our business partner in USA, they will help to change the chargers, i will send you the address later.

Best regards,

What should I do?, any ideas?

BB. · August 2018

The 120/240 vac jumper is an easy configuration change. Just need to know the gauge of the jumper wire to use.

Sending the unit to one of their USA partners is fine... This is an issue with buying direct from overseas.

But i understand your concern with the configuration issues and extra time and costs... Hope the rest of the be build process was done correctly.

Bill

cow_rancher · August 2018

Yeah, I would fix it myself, you already have their authorization, I understand the shipping cost problem, you can either work with them or don't ever buy from them again. But then I've been taking apart electronics boxes all my life, just to see what makes them work, sometimes they don't work when I get them back together. But one jumper shouldn't be hard to accomplish.

Rancher

Functional_Artist · August 2018

Here is a pics of the factories suggested repairs

"The instruction is attached, use 17awb wires to connect the two places, for the NTC points, the green NTC can be removed out."

So, I need to add a jumper wire connecting A & B

…& simply remove the green NTC, just clip it out?

...or is a second jumper needed?

What size wire = 17AWG (American wire gauge?)

Solar Charging a 48V go kart

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