eBike charging questions from complete newbie

[eTouringOldie]

I'm looking for a 200W charging system for my 48volt ebike battery. I want it to be portable (foldable enough to store in a bike trailer when not in use) so I can do some touring without worrying about finding outlets every day. I presume that I'll ride mornings and/or evenings and charge in the middle of the day. A more ambitious version of this story would be to figure out a way to mount the solar panels to allow charging while I ride, but that's probably a pipe dream.

Question: pre-packaged systems which directly charge the ebike battery seem to have a 'step-up MPPT charging controller' which accepts the PV, which can be anywhere from 12V to around 30V and steps the voltage up to 48V (or even as high as 72V in some cases). Seems like the inverter option means carrying more gear (AC charger, inverter, solar panels and whatever hardware is included to output to the inverter) vs a 'direct connect approach, although I imagine I'll carry the AC charger in any case.

As you can probably tell, I barely know what I'm talking about. Key point here is that I'm looking for a system to be used for one purpose only (charge the ebike battery).

Here are some examples of the pre-packaged system I've considered:

Solar 200 Watt Ebike Battery Charger - Sun200

Electrify Bike Sun200 - 200 Watt Solar Solar Ebike Battery Charger Charges 36v, 48v, 52v, 60v, and 72v batteries.

www.electrifybike.com

200 Watt Solar Panel - Bakcou

Discover our powerful 200-watt solar panel for efficient, eco-friendly energy generation. Go solar with Bakcou today!

bakcou.com

Portable Ebike Solar Charging Station

Take your adventures to the next level with QuietKat's new Portable Solar Charging Station. Charge on the go at an incredible 150w of power! Similar charge time to the standard wall outlet, in ideal conditions!

quietkat.com

Maybe there's no better/cheaper DIY option?

Thanks for any assistance!

 

[HRTKD]

For any portable panel, I would look at lots of independent reviews first. Most of those kits don't put out what they're rated for.

 

[dcg9381]

I'm looking for a 200W charging system for my 48volt ebike battery.

How big (amp hours) is your 48V battery? We'll give you some ideas about how realistic is it is to charge off 200W.

What "also" is critical is the charge controller type..

 

[eTouringOldie]

How big (amp hours) is your 48V battery? We'll give you some ideas about how realistic is it is to charge off 200W.

What "also" is critical is the charge controller type..

Battery is 22 AH. That's why I'm looking at 200W systems. I get that charging it will still take several hours. My vision is that I sometimes get places and lay up for a day to recharge, sometimes don't go 'that far' so a partial charge is good enough, and sometimes have access to AC.

Using 200W and 48V, I figure the battery will see about 4 Amps, so theoretically 5.5 hours to charge. Obviously those are ideal numbers and the real world is different, so maybe 8 hours to full charge?

Clearly this whole scheme is a work in progress.

When you say 'charge controller type' do you mean the my AC-powered charger which plugs into the wall, implying that the charging controller in the system I put together or buy has to mirror its functionality?

 

[dcg9381]

48V * 22AH = 1056 Wh, so yes, 200W, 5.5 hours - your math is about right.
Thing is, solar production is on a bell curve (assuming you don't adjust direction and tilt). So yes, 8 hours could be realistic on a day with full sun and no clouds.

Can you leave this setup outside somewhere for 8 hours day?

I assumed you'd be charging the battery directly from solar through a charge controller. Yes, that mirrors the function of the AC-charger you have. DC to DC charge will be more efficient. If you're trying to power the AC charger, that's a little more problematic.

 

[eTouringOldie]

For any portable panel, I would look at lots of independent reviews first. Most of those kits don't put out what they're rated for.

I hear you, but there seem to be relatively few reviews of these products. One very favorable review of the QuietKat, but the reviewer never gets to the technical performance details.

 

[dcg9381]

One very favorable review of the QuietKat, but the reviewer never gets to the technical performance details.

I don't think that the solar guys reviewing 200watt panels are probably going to do a lot of technical testing.

What's the charge controller here? That's the critical piece. I'm not terribly concerned about choosing the right "portable panel".

 

[eTouringOldie]

48V * 22AH = 1056 Wh, so yes, 200W, 5.5 hours - your math is about right.
Thing is, solar production is on a bell curve (assuming you don't adjust direction and tilt). So yes, 8 hours could be realistic on a day with full sun and no clouds.

Can you leave this setup outside somewhere for 8 hours day?

I assumed you'd be charging the battery directly from solar through a charge controller. Yes, that mirrors the function of the AC-charger you have. DC to DC charge will be more efficient. If you're trying to power the AC charger, that's a little more problematic.

Thank you -- nice to know I'm not completely insane.

Funny, when you mentioned angle and tilt, I immediately thought of telescope setups which automatically track a spot in the sky to focus on an object as the earth rotates under it.

As for 'leave it for 8 hours', hard to say. As I mentioned, this is a work in process, so I'm not sure of those operational details. I'm still feeling out what the limits are, and where my comfort zone might end up. Just recently got the bike, and as soon as I realized it could get my old tired body to places pedal power couldn't, I started dreaming. For example, I'd love to take 2 - 3 weeks touring the Yellowstone figure 8. I know there will be AC power available sometimes, but not necessarily at every stop.

Baby steps are going to be taken here on the coast of Oregon. I'm planning some expeditions into the Coast Range on logging roads, fishing in remote streams and ponds and ironing out the right gear for warm summer weather and rain.

Insane ambition would be the Baja Divide Trail, but that's way down the road after I'm very comfortable with my system, with lots of experience as well as a few Tragedies Narrowly Averted.

 

[eTouringOldie]

I don't think that the solar guys reviewing 200watt panels are probably going to do a lot of technical testing.

What's the charge controller here? That's the critical piece. I'm not terribly concerned about choosing the right "portable panel".

That's the actual question I'm trying to figure out. I mean once I nail the charge controller, it shouldn't be too hard to find compatible panel.

I just notice that many/most of the charge controllers I see can't step-up the voltage, only down, and none of the panels I see produce 48V. And I have no plans to connect several panels in series to increase voltage.

But the controllers included with the systems I linked in my first post all seem to step-up. Perhaps that's not a standard feature of such devices, and only purpose-built ones built for/by the companies putting those systems are available.

As I've mentioned (several times) I'm a complete rookie at this, so I may be making stupid assumptions or asking dumb questions.

 

[45North]

A couple of comments from using ebikes for 4 years fwiw:

• While nominal v is 48v they actually charge to more like 54v when new and only 53 v after a few years.
• According to my kill a watt they initially draw 300 w from the standard Ac charger that comes with them, gradually decreasing to 0 when full.
• I haven't done the math but they seem to charge for a little longer than I ride. So, they would charge for about 3 hr after a leisurely 2 hr ride around town at 20 kph.
• Riding fast (32kph) into a headwind greatly reduces range.

 

[dcg9381]

That's the actual question I'm trying to figure out. I mean once I nail the charge controller, it shouldn't be too hard to find compatible panel.

You need a 48V "charger" that's compatible with PV panels and your battery type.. We don't know the specifics of your battery - and likely you don't either - but we can guess from battery chemistry if you know the battery type. Most lithium batteries are going to charge at 53+ volts.

Surprisingly, Renology seems to make one at a reasonable price that indicates it will work with Lithium batteries and 12 or 24V panels. The others you've listed should work also, but they are oddball. Where I see you going sideways is paying $700 for a 200 watt solar panel (or series of smaller panels).

 

[eTouringOldie]

A couple of comments from using ebikes for 4 years fwiw:

• While nominal v is 48v they actually charge to more like 54v when new and only 53 v after a few years.
• According to my kill a watt they initially draw 300 w from the standard Ac charger that comes with them, gradually decreasing to 0 when full.
• I haven't done the math but they seem to charge for a little longer than I ride. So, they would charge for about 3 hr after a leisurely 2 hr ride around town at 20 kph.
• Riding fast (32kph) into a headwind greatly reduces range.

Thank you for that info.

I guess you're saying that, given your riding habits, the battery discharges faster under real-world conditions than it charges from your AC charger. And you're also saying that charging is non-linear.

If your battery is drawing 300 watts, then that's about 6 amps, right (300W ÷ ~50V)? Given that I'm talking about using a 200W system, the best I could hope for would be 4 amps, and that's with ideal solar conditions and no significant loss in the charging system.

< aside > your comment about headwind made me think of fairings < /aside >

 

[eTouringOldie]

You need a 48V "charger" that's compatible with PV panels and your battery type.. We don't know the specifics of your battery - and likely you don't either - but we can guess from battery chemistry if you know the battery type. Most lithium batteries are going to charge at 53+ volts.

Surprisingly, Renology seems to make one at a reasonable price that indicates it will work with Lithium batteries and 12 or 24V panels. The others you've listed should work also, but they are oddball. Where I see you going sideways is paying $700 for a 200 watt solar panel (or series of smaller panels).

Yep, the cost certainly got me over here when I saw that the panels are worth between $200 and $300 (ish), but I had no idea what a charge controller might cost. But if the panels are close to (or more than) $300 and the controller is another $200, then DIYing isn't going to help me that much, and the convenience of the 'bunch of small panels connected but foldable' idea begins to seem pretty attractive. But I'm not in a hurry, so I'll figure it out, one way or the other, eventually

 

[dcg9381]

Thank you for that info.

I guess you're saying that, given your riding habits, the battery discharges faster under real-world conditions than it charges from your AC charger. And you're also saying that charging is non-linear.

The thing with lithium batteries... They have tremendous discharge capability. I have batteries that fit in my hand that can discharge (easily) 1000 watts sustained. Do not assume that time on the charger = riding time. Not even close.


Yes, lithium battery charging is non-linear (assuming there is additional charge capacity). In your case (limited power source) you really can't fast charge.

If your battery is drawing 300 watts, then that's about 6 amps, right (300W ÷ ~50V)? Given that I'm talking about using a 200W system, the best I could hope for would be 4 amps, and that's with ideal solar conditions and no significant loss in the charging system.

No, the best you could hope for is under 4 amps. Charge voltage will be in the 53-54 V range (likely higher). You're looking at <4 amps from a 200 watt source after losses.

 

[JWLV]

Is light weight, foldable, and small size part of your requirements? If so, then the three choices you posted seem to fit the bill. They are more expensive, but you get the benefits of light weight, foldable, and small size. Those things you really can't do yourself with readily available parts. Yes, there are flex panels readily available, but I haven't seen any that are 200W and can fold up like the ones you chose.
If you wanted to go the DIY route, 200W panels are about $150, a simple MPPT controller is about $100. Add a few bucks for cables and connectors.

 

[eTouringOldie]

The battery is a case with a bunch of small lithium cells inside.

 

[eTouringOldie]

Is light weight, foldable, and small size part of your requirements? If so, then the three choices you posted seem to fit the bill. They are more expensive, but you get the benefits of light weight, foldable, and small size. Those things you really can't do yourself with readily available parts. Yes, there are flex panels readily available, but I haven't seen any that are 200W and can fold up like the ones you chose.
If you wanted to go the DIY route, 200W panels are about $150, a simple MPPT controller is about $100. Add a few bucks for cables and connectors.

Foldable seems like a requirement given that I’ll be transporting it on the bike or trailer. A 2 * 5 ft sheet is gonna act like a sail and really affect my ride. Plus, it makes the rig wider and if it’s not in some rigid frame (more weight) it’s gonna get flexed which can’t be good, and probably gets broken when I crash.

Of course lightweight is nice, but probably less important than foldable and efficient, as long as we’re not talking 30+ lbs.

In any case, I’m struggling to find an MPPT controller I could use w/ a 12 or 18V panel and my 48V battery. Maybe I’m not understanding what I’m reading, but it seems like the controllers I see around that price aren’t going to step up the voltage that much.

Speaking of ‘not understanding’, I’m seeing panels advertised as 200 watt, but with specs saying a max voltage of 18V and a max current of 3 or 4 amps. That seems like 54 watts or 72 watts, not 200. Am I missing something, or is it just advertising BS?

 

[zanydroid]

I found an “MPPT boost charge controller” on Amazon the other day designed for 48v (while looking for a listed one for residential install). Search that exact string in Google.

You can also use a regular buck charge controller as long as you put enough cells in series to get the necessary voltage headroom for 48V. I think you need something like minimum 120 cells in series. And then the panels need to support that system voltage (though I would imagine they need to really be… special… to not be able to handle ~60v)

 

[zanydroid]

Also keep in mind the most honest solar panel wattage numbers will be in STC (standard test conditions), which are already optimistic (power company here takes the lower PTC rating when sizing your system).

Since you are buying stuff of dubious regulatory oversight, they’ll probably stretch the specs more than even than STC.

Proper STC/PTC wattage numbers will agree with Vmpp and Impp on the rating sticker

Potentially for portable applications they will skimp on the reinforcement to allow for some weight reduction. In the panels we put on houses the weight is generally directly proportional to wattage, but those have to withstand windstorms.

 

[zanydroid]

Post #11 already has a boost MPPT from a reputable tier 2 seller (renogy). Not sure why the research needed to proceed past that point, unless it can’t actually go to 48v? That is what you need for a single panel setup.