Solar charging of my e-battery

[covehithe]

I am in process of revamping my solar system in my shed which I have been running successfully for past 2 years.
I now want to be able to charge the battery from my Kalkoff C11 using my solar system. I have a modified
sine wave inverter which is fine for charging sanders, drills & lights.
Some battery chargers only work correctly when using Pure sine wave inverters as do some laptops etc.

Question: Are the electronics in my e-battery and charger up to being used through my Modified sine wave inverter - if try it and get it wrong there goes £500 for new battery!!

Any one tried or using solar charging?

 

[peerjay56]

I would be wary. Similar technology but not ebike - I know someone who tried recharging Segways (plural) from a generator with sine wave inverter, as opposed to pure sine wave, and the charging circuitry got fried. HTH

Edit: Thinking about it, the issue is the dirty nature of the power supplied by the generator. Presumably solar panels will provide a much smoother supply anyway.

 

[twinkle]

Been running a laptop and tv on a 500w Msw inverter for a couple of years now without a hitch in the caravan . We are using a 12v 80 ah battery as a dump for the 120 watt solar panel .
At home we have 140 watts of solar panels dumped into 160 ah of battery and using 2 off 300 watt MSW inverters to drive the main lights , laptop and Flat screen TV .

emma

 

[Deleted member 4366]

Don't forget that you need a lot of 12V battery to charge a 36v 10aH one through an inverter.

26v 10aH = 12V 30aH

With losses through the inverter and charging, you'd need 40aH.

You shouldn't take a lead battery past half-way, so you'd need a minimum of 80aH from a battery in tip-top condition, which means about 120aH for one in normal condition.

Any deep discharge damages a lead-acid battery, so ideally, you need a pair of 100aH ones or something similar.

 

[twinkle]

Forgot to mention mine are deep cycle wheel chair batteries ( 4 x 40 ah )


12x 160 ah = 1920 wh /2 ( 50% ) still gives 960 wh or just under 1 KWh

I think I am safe

 

[covehithe]

I'm using a 140W panel and a 120w/h battery. I've tested my lights, chargers and connected my old Macbook - no problem. I'm am going to try out some other "appliances" - fan, slow cooker and my Dremel.
I have chickened out and decided not to risk my bike battery - too much to lose!!!

 

[Cottonpickers]

I'm in the process of putting together a 'micro' solar solution for my eBike. I make various solar panel setups - for iPads, Raspberry Pis and other 5v or 12v applications. You can see some pictures of these over at http://twitter.com/cottonpickers

Typically I make my solar stuff in the 5w - 25w range -so it certainly won't be a 'fast charge' solution ;-) but will be modular - so you can use the panel to charge your iPad with one lead, and then plug in the charger lead for the eBike. Or you can plug the charger into your car socket or laptop to trickle charge. The voltage is adjustable for Li-ion and LiFePO4 cells - with the aim of it being very 'pocketable' I've gotten a bit sidetracked but when its finished I'll share more info here. A 400Wh battery would obviously take a LONG time to charge but I still like the idea. The pic shows the charger with the car adapter. More updates shortly..

 

[oigoi]

Live off grid with a solar photovoltaic power supply. I have been charging my cyclone 24v lifepo4 battery through a quasi sine wave inverter and 90w charger without a problem for a few years now. I'm not 100% that all chargers would be okay with quasi sine wave, but my understanding is that any that work on the SMPS (Switched Mode Power Supply) principle would be fine, because they convert the quasi ac input to dc so don't mind if the ac is not pure sine wave. Most laptop chargers work on the same SMPS principle I have yet to find a laptop charger that would not work on my quasi sine wave inverter

 

[SAD12]

I've got a campervan with two 12v 100a batteries in parallel. Last year was the first year with the e bike so I used the standard charger plugged into a 1200w inverter. It charged the bike with no difficulty but did sap the power from the batteries if we didn't move the van for a few days. I reckoned no more than three charges (variable distances covered) was allowed before we got into trouble with the van's power supply, but that was pushing it. Now I've installed a TV as well so I've been thinking about a solar panel to supplement the batteries. In addition I've been experimenting with a step up converter I bought off ebay for about £12. I reckon the inverters have large losses and would like to cut this down. Below is a picture of the experiment on the workbench. The converter can be adjusted for volts and amps so it's set up to 41.7v output and 3.2 amps in which roughly equates to a 1 amp charge at 41.7v. It was increasing the voltage in the battery at 0.1v every 4 mins 20secs, so roughly 1v increase every 50 mins or so. I'm thinking that while I'm away the battery on the bike will never get fully charged this way but when I get home that can be sorted by putting the regular charger into the mains again. Incidentally, the step up converter only got slightly warm (hardly noticeable) using it this way so it might be the way to go?

 

[SAD12]

I've just done a little experiment to see how much of a loss there is with a 41.7v, 1.8a bike battery charger plugged into an inverter and running off a 12v battery. With just the inverter connected it was pulling half an amp at 12v. Plugging the charger into the bike battery and the current went up to 8.8amps from the 12v source. By my reckoning there's about a 3amp loss in there somewhere so I'm definitely going to use the step up charger when away from the grid.

 

[Cottonpickers]

This is the step up converter I used. It is good for a couple amps and has a built in voltmeter. You can adjust the output voltage all the way from 7v to 60v. I made up the case on my 3d printer and added connectors for USB and 12v input with a standard 2.1/5.5 output which fits my bike battery. Only snag is the voltmeter reads perfectly when the source is a laptop / car but reads high when source is solar. Not sure if it's because the solar voltage saga on the input. If anyone is interestedin one if these kits let me know and I'd be happy to send it over for £19 inc postage

 

[oliverjp81]

I’m waiting for the day that everything goes USB-C. Solar panels with USB-C direct into a power bank. Then out into a USB-C port on the battery.
Have you cycled to work and your battery is low? Plug it into your laptop’s USB-C power supply. And vice versa.
I’m surprised no manufacturers have done this yet and would welcome being told I’m wrong.

 

[cyclebuddy]

I can't see that working at all. A 42v e-bike charger at 2A is drawing 84 watts (ignoring conversion losses). 84 watts from a 5v USB supply would need a massive 16.8A current... but the limit over USB-C is 5A maximum. You could use a lithium battery as a buffer, but it'd need to be at least as meaty as the e-bike battery (i.e. expensive). That's why a 80-100Ah car/leisure battery provides an ideal low-cost buffer/storage medium between solar panels and an inverter (or direct 12v e-bike charger) - because most already have one with them in their car/caravan/mobile home.

That's forgetting of course that a 2A charger is quite leisurely by todays standards - especially as many nowadays opt for much larger e-bike batteries, ideally needing 3A to 4A chargers.

 

[oliverjp81]

The wattage on USB-C chargers is there (at least 96W) but they typically have a maximum of around 20V. An electric bike could use a 20V battery or better it could use a pair of 20V batteries or a single battery that is internally two 20V batteries that get connected in series when in use, either physically or electronically and that could be internal or external to the battery. The batteries would need to be balanced but that’s not difficult to do.
Call that 100W and it’s 5A, not 3A.
Of course, none of today’s batteries would work, they would need a USB-C port for one thing. It’s a bit like the old mobile phones, all having their own proprietary charger, eventually, hopefully we’ll have a standard.

 

[cyclebuddy]

An electric bike could use a 20V battery

Yes, earlier e-bikes were 24v, but by todays standard of 36v, trending towards 48v/52v, a 24v e-bike wouldn't pull the skin off a custard.

...and it’s 5A, not 3A

That is what I said - USB-C is max 5A. But that seems to me to be the problem with the theory - you can't get away from W = V x A. With "normal" e-bike batteries now leaning towards 17Ah/625W nowadays for torque/power/range, anything using USB of any standard to charge is going to take an eternity however you cook it.

I would welcome being told I’m wrong.

 

[oliverjp81]

Take the Brompton Electric. It has a 300Wh battery. I think the rule of thumb is that it takes 1.5x the capacity to charge a battery to full, not sure if that rule is appropriate for lithium chemistry but let's go with it. So call the 300Wh 450Wh and let's say we have a 100W charger. That would take 4.5hours to charge. That doesn't seem too bad to me. Now let's assume charging two batteries takes twice as long (just to err on the worst case): 9 hours. Both of those seem perfectly reasonable to me if you're going to charge a battery overnight. Of course there are different capacities but in my experience (commuting) my battery lasts all week, so I certainly don't need to charge it to capacity every night.

I'm sure that if we can charge a battery on a helicopter on another planet using the voltage from a solar panel, then we can charge an electric bike battery with a 100W 20V power supply.

 

[cyclebuddy]

So call the 300Wh 450Wh and let's say we have a 100W charger. That would take 4.5hours to charge.

You're proposing a 300Wh 36 volt Brompton battery that needs to charge to 42 volts, but being charged from a 20 volt charger at 100 watts through a USB-C cable whose accepted universal standard voltage is 5 volts? Even using a buck converter, I'll be dead by time that gets done! I'll be dead even quicker if I make the mistake of plugging my USB-C Xiaomi 'phone into your 20-volt USB-C charger by mistake (assuming it doesn't have a marker chip)!

 

[oliverjp81]

No I'm proposing that manufacturers make batteries that are capable of being charged by USB-C. All I'm hearing from you is it's not possible without actually thinking how it could be possible. In RC, it's frequent to use multiple batteries to push up the voltage, there are also electric lawnmowers and other tools that use multiple batteries.

So I didn't know that USB-C cable maximum voltage is 5V. I was purely looking at the power supplies which seem to be able to supply 20V at 5A, otherwise how else do they get to 100W? Anyway, say the max voltage is 5V and to bring things into the realm of reasonable, Brompton were proposing a flight safe battery of 100Wh. Also assuming there is some electronics in the battery that allows a 36V battery to be charged by a 5V supply. So let's call it 5A * 5V = 25W. 100Wh would take 4 hours, plus the 1.5x takes it to 6 hours. That is still in the realms of useful. Imagine being able to travel with a single charger that could charge your phone, laptop and bike.

By the way, when I said I welcome being told I'm wrong, I meant being told that such a thing does already exist but fair dos.

And you won't fry your phone because USB-C supplies switch.

I don't claim to know the intricacies of charging etc, I'm just saying a battery that can be charged by USB-C would be really nice. Whether it's safe, possible or financially viable is another question.

 

[cyclebuddy]

All I'm hearing from you is it's not possible without actually thinking how it could be possible.

That's because you're theorising. I have a VW Transporter Touring van, with a 52" flat-TV-sized 100 watt solar panel, and two inverters for charging my 3 e-bike batteries. I'm also a qualified electrician. How I hate wasting mobile power through conversion losses.

The Solar is useless in anything less than when facing direct sunlight (rare in our climate). Most of the charging in reality comes from the van's alternator or campsite/pub/cafe power. Other members here too use similar "mobile" arrangements. We've all thought of more efficient/easier ways of charging our batteries. Your Brompton 300Wh is on the small side comparatively to what most seem to be using here.

Really, I am on your side - I love the "one charger" idea in principle. But I can't see any practical way of doing it. If such a thing did/does/could exist, somebody here would already have found, invented and/or shouted about it.

Yes, USB-C can be used to deliver 20 volts... with marker chips. But if you then need a "special" USB-C 20v charger, why not just use the one designed for purpose as we currently do - a balance between cell chemistry, cell capacity, speed of charge, and safety given the latter (some use comms between battery and charger to avert dangers). Yes, you could step-up voltage, or use combined cell-packs, but there's no free lunch: W = V x A, and most e-bike batteries need a shed-load of energy to fully charge (typically half a large 100Ah car battery).

IMHO, your aim simply seems to dovetail an inappropriate standard to serve a purpose for which it's not best suited. IMHO it's a nice idea, but no cigar.

PS: Trade member Woosh designed a Brompton kit that can be powered from a 36v Drill battery... you can take that on a plane. There're pics elsewhere on the forum.

 

[WheezyRider]

Yes it can be done. You need a USB-C handshake board to tell the port to supply 20V, not 5V, then you need a voltage converter to step up the 20V to 42V.