Finally Going Green

[Leslie]

I woke up this morning not keen to ride as it was raining.  The solar charge station kept the LiFePo4 balanced and 36v SLA pack on the smaller bike balanced over night.  Didn't test the voltage as a quick glance at the analogue volt meter showed it was above 12v.

I did a 20km run today, maybe used about 4.2 ah.  I finished charging a few hours ago on the solar charged batteries.  It was cloudy all day and the 7 old 24ah SLA batts are still a healthy 12.4v.  Even being cloudy all day for 2 days would allow me to do 20+ kms per day from this charging station.

[MonkeyMagic]

Hey Les make sure you save some of that love for your wife !!



I'm jealous.... again..... hehe there's not enough sun in Melbourne but plenty of wind !!

[GM Canada]

Once again, another very impressive thread. I would love to do something like this, but I really don't understand what is required. Maybe someday when you get some free time (if you ever do) maybe you can make up one of those "new fangled wiring diagrams" showing what components are required between the sun and the bike for us laymen to understand.

I am also wordering Peters question, "Why two throttles"

Is one a spare in case of failure or are they both wired and you can use either?

Gary
 

[MonkeyMagic]

Hey Gary, I'm sure you are being modest! I can draw it here for you champ
Solar panel----> Regulator controller ----> Batteries ----->  Inverter -----> Charger ------> eBike, other stuff -----> Smile

If you just want to charge bikes in the sun then you are best to go this way:
Solar panel (x amount in series for voltage/parallel for current) ----> Regulator controller ----> eBike Battery

So you are not converting DC to AC then back to DC again...arggh dizzy! (+heat,loss,inefficiency issues)

Maybe after your next order to GM, you will find one of those folding direct plug-ins in that pocket of yours....

MM

[GM Canada]

Hey Gary, I'm sure you are being modest! I can draw it here for you champ
Solar panel----> Regulator controller ----> Batteries ----->  Inverter -----> Charger ------> eBike, other stuff -----> Smile

If you just want to charge bikes in the sun then you are best to go this way:
Solar panel (x amount in series for voltage/parallel for current) ----> Regulator controller ----> eBike Battery

So you are not converting DC to AC then back to DC again...arggh dizzy! (+heat,loss,inefficiency issues)

Sounds like the first option would be better as you can charge or run several things.

Maybe after your next order to GM, you will find one of those folding direct plug-ins in that pocket of yours....

MM

Why did you say that? Now the wheels are turning in my head (squeak, squeak, squeak), I hear a voice saying "how can you possibly sell items you haven’t even tried yourself? You should at least order some for inventory!!!"

Gary

[Leslie]

Ok cloudy rainy again.  Haaa Im lucky to be getting 1 amp from the panels its so dark, the needle amp meter isnt that accurate to read,  But after A WHOLE NIGHT of leaving the lights on the 12V sla's have regained .2v (12.6v) but still giving us lights inside during the dank dark morning.

I left the chargers on the packs for a few hours and switch them off the system before I went to bed.  If I suspected the weather was going to be fine I would some nights just leave them on.

I have a number of small lights scattered about the home.  Im thinking of setting the eldest children up with a small solar system for themselves.

This one is getting kinda too big to manage so instead of having one huge bank I can make a few systems to do.  The amps this slab can push are pretty significant so I will stop while its still functional.  I saw a fast short when installing SLA batt 8 and fried the post.

[Leslie]

The up converters in these types of 12v dc  to 220v ac converters work most efficiently when they are run over 80% to maximum capacity and under 95%.

So to be brief if you want a similar setup its good to pick an inverter that can just manage the watts needed to run your charger by 15%.

Often like my inverter the 300 watt label is underrated to spec so it is safe to stick by it.

Always consider down conversions to an 80~85% efficiency loss and high load up conversions efficiency can reach up to 95%..

So a GM battery charger charger may well lose 15% of the power through the switcher that actually makes it into you pack.

Your typical 2 amp charger may do 60v @ 2 amps,  This is around 120 watts.  

How to calculate the right size inverter.


Add for the loss of 5% up conversion of the inverter to charger input voltage 110v~220v.

120 watts/100=1.2

1.2X105= 126 watts

Now add for a loss of 15% to down conversion charger input to output losses.

126 watts/100=1.26

1.26*125%=157 watts.

On paper one would be prompted to order something that could do double this.  In fact my 300 watt does doube the abobe figure very comfortably and would do up to a 5 amp 48v charger if it wasnt for the protection.


So using a 150 watt power inverter should be very nice for a single bike.  The Watt rating makes it easy to chose the right size.

You should not overload the inverter,

So if you need 12VDC to 110VAC~220V inverter to power a 5 lithium ebike battery charger amps charger.

60v*5A= 300 watts.
 
300/100x105/100*125= 393 watts.

So any inverter above 400 watt rating for a 5 amp ebike charger will do fine.


If it works you will have a device already running at the max rating which is what these inveters just love, as long as the inverter is not flaming hot the device is working very well.

The good thing about the sun being out while charging you can avoid much of the chemical transformation process losses in the SLA's and the panels go straight to the converter charger to the  pack.

Losses may equate to about 35% with the ebike battery charger being the most inefficient of the two conversions.  But if one can avoid the inefficiency of charging another battery the better.  The buck conversion inside our ebike battery chargers are inefficient than boost converters by nature anyway

If I get charging by mid day this thin really works well and I never see the SLAs drop below 12.9v and they stay flaot the rest of the day at 14v..


  

[Leslie]

The above post could be easily summarized by a single rule of thumb.

For every 1 amp 48v ebike charge amp you would require 100 of watt rating 12v battery inverter.


like

2 amp charger would a 200 watt inverter
3 amps charger uses a 300 watt inverter.

The 36v chargers uses less watts too so you can do down to 90 watts per charger amp.

The equation above is,   Required inverter rated watts (157watt) = (60v) max charge pack voltage * (2a) charger amps/100_%*105_%/100_%*125_%

[Leslie]

Logged.
Bike
17.6km
287wh

Pretty windy, 35km average wind gusts

Cloudy until noon.

The panels needs a CA on it.  But I was getting anywhere between 1 amp and 8 amps after noon. Sitting just over 13v with 3.5 amps solar panel current going to the whole string.

Ok its 3:10pm start two amp charge to 15 ah pack at 52.9v

SLA solar storage bank @ 12.7v

[Leslie]

If I need to put in 25% more power than I have used.

287 wh *125% = 356 Watts,

At an average of 55v* 2amps charger = 110wh

356watt/110wh= 3.2 hours.  IF It takes this long this shows me the CA is not badly calibrated.

Well im not even half charged and the old SLA bank has taken a beating down to 11.97v  Once this bulk charge is finished I suspect the SLa volts will go back up,

My original multimeter I tested the 12.7 had a flat battery I fixed it now but to a lesser degree this log was unsuccessful.  So the original volts for the first reading was too high.  More like 12.5v was its starting voltage.

edit.

The 15ah ebike pack is hanging around at 53.9v this is normal behavior for LI packs to stay charging within a narrow voltage range for over an hour then start to race to a good balance voltage.

[Cornelius]

Here's a table that I find practical to determine approximate State of Charge (SoC):

% of Charge - - - - - - - Charging - - - -- - - At Rest - - - - - Discharging
100  - - - - - - - - - - - - 14.75 - - - - - - - - 12.70 - - - - - - 12.50
90 - - - - - - - - - - - - - 13.75 - - - - - - - - 12.58 - - - - - - 12.40
80 - - - - - - - - - - - - - 13.45 - - - - - - - - 12.46 - - - - - - 12.30
70 - - - - - - - - - - - - - 13.30 - - - - - - - - 12.36 - - - - - - 12.25
60 - - - - - - - - - - - - - 13.20 - - - - - - - - 12.28 - - - - - - 12.15
50 - - - - - - - - - - - - - 13.10 - - - - - - - - 12.20 - - - - - - 12.00
40 - - - - - - - - - - - - - 12.95 - - - - - - - - 12.12 - - - - - - 11.90
30 - - - - - - - - - - - - - 12.75 - - - - - - - - 12.02 - - - - - - 11.70
20 - - - - - - - - - - - - - 12.55 - - - - - - - - 11.88 - - - - - - 11.50
10 - - - - - - - - - - - - - 12.25 - - - - - - - - 11.72 - - - - - - 11.25

The voltages under charging and discharging should be measured with at least C/20 current in/out, and the figures are @ around 26.7deg. C. at 0deg. C, one should add around 0.6-0,8v for charging, and subtract around 0.6v for discharging...

Ofcourse, this is only approximate, but gives one a good idea of the state of the battery when one are not able to measure the Specific Gravity (SG).).

Edit:
These figures are valid for Lead Acid batteries; the Lithium based batteries are a whole another matter when it comes to determine SoC...

[Leslie]

Mine is an SLA controller that goes no higher than 14v.  This is because 100% SOC can be achieved with constant current at voltages as low as 13.85v.  If it were practical even as low as 12.9 if it were possible to achieve an good current feed at this charge voltage.

However it finished.

LI batt @ 60:05v 6>05pm.  Completed bulk charging in 2 hours and 55 mins (175mins).  Estimated watts that charged pack @ 54v 2 amps = 315watts

Watts consumed 285wh by previous ride on  eBike.

315 watt -  285watts = 30 watts overhead.
 
315/100=3.15
285/3.15=90.47%

Check figures.

315 watts/100*90.476= 284.9994 watts


Estimated efficiency if full balance were to be achieved at bulk charge, 90.47% take another 10% for balance closer to 80% efficiency..

Haa! and this is just for the LI charger.  Doh!


SLA batt @ 11.73v and recovering  I am still running one 5 watt light off the SLA's and balancing the 48v ebike pack.  SLa has risen to 11.77 since typing this.

[Leslie]

Well its official I cant get much further than 2 days in the clouds.  I might be able to push another charge in this muggy weather by the end of tomorrow other iwse Im back on the wall outlet.

The inverter powering a single 48v two amp charger draws between 10 and 12 amps so we average this to 11 amps from the SLA pack.

We took approx 30 amps out of the SLAb today and about the same yesterday.  I think I will be able to estimate the old SLA slabs remaining capacity soon enough.

Works much better when the suns out and volts are higher on the SLAb though.

[Leslie]

Here's a table that I find practical to determine approximate State of Charge (SoC):

% of Charge - - - - - - - Charging - - - -- - - At Rest - - - - - Discharging
100  - - - - - - - - - - - - 14.75 - - - - - - - - 12.70 - - - - - - 12.50
90 - - - - - - - - - - - - - 13.75 - - - - - - - - 12.58 - - - - - - 12.40
80 - - - - - - - - - - - - - 13.45 - - - - - - - - 12.46 - - - - - - 12.30
70 - - - - - - - - - - - - - 13.30 - - - - - - - - 12.36 - - - - - - 12.25
60 - - - - - - - - - - - - - 13.20 - - - - - - - - 12.28 - - - - - - 12.15
50 - - - - - - - - - - - - - 13.10 - - - - - - - - 12.20 - - - - - - 12.00
40 - - - - - - - - - - - - - 12.95 - - - - - - - - 12.12 - - - - - - 11.90
30 - - - - - - - - - - - - - 12.75 - - - - - - - - 12.02 - - - - - - 11.70
20 - - - - - - - - - - - - - 12.55 - - - - - - - - 11.88 - - - - - - 11.50
10 - - - - - - - - - - - - - 12.25 - - - - - - - - 11.72 - - - - - - 11.25

The voltages under charging and discharging should be measured with at least C/20 current in/out, and the figures are @ around 26.7deg. C. at 0deg. C, one should add around 0.6-0,8v for charging, and subtract around 0.6v for discharging...

Ofcourse, this is only approximate, but gives one a good idea of the state of the battery when one are not able to measure the Specific Gravity (SG).).

Edit:
These figures are valid for Lead Acid batteries; the Lithium based batteries are a whole another matter when it comes to determine SoC...

The discharge volts are handy.  You know the sun can be bad for the whole day and the batt sits at 13.5v and if the sun pops out it can be fully charged.  Solar charging with no CV and CC makes the % of charge table not so usefull.

[Leslie]

Wow Im getting up to 9 amps at 12.76v and rising.  The sun is in and out of the clouds now.  It was a little better in the morning.

I think 130 watt worth of panels is plenty enough to keep an Ebike running.  I think a 120 ah battery is more important.

I suspect I am running about 90ah with the old batts.


Like I use about 400 watts a day if the bank is charged by the time I do my daily ride all the power from the panel goes into the ebike pack.  If I do it before 2pm on a sunny day I only have to use 3 amps on the fly 12ah in total from the battery.  Which 12ah only tickles the 90ah SLAb. And by afternoon bike is often charged and my SLA pack has only 12ah which is just attainable from the afterrnoon sun at my location.

A guide to pick a battery for a panel.

10 watts per 10ah is a comfortable minimum SLA's will get up to SOC in a day

15 watts per 10ah is perfect for sunny locations.  

20 watts per 10ah is better in cloudy weather or less sunny locations.

40 watts per 10ah for people who live in areas that don't get much sun.

It depends on your solar controller too,  If you like to charge your packs really fast before miday with lots of current you would want one of a lower voltage.

Where as something slower with smaller panels and lower current would be better with a higher voltage bulk charge and low float.  My sun saver charges 9 amps to 14v off my panels and this is almost spot on with my panels output ratings.