Solar battery charging for ebikes.

[Nealh]

If you have only a single battery then that could be an issue.

If you have two batteries, then you can readily alternate them, perhaps charging only on 1 Amp for long cycle life.

Even using two batteries, I wouldn't sacrifice one just for the sake of it.
The sums have to match up for the cell spec chargerate other wise a fairly costly solar set up will also become a costly battery replacement issue.
For offgrid or touring charging it has to make sense to do it vs the cost of a few pennies to plug in the wall and tbh the latter is likely going to be cheaper once one thinks about it properly.

 

[WheezyRider]

This is about where I'm coming to.
Having let my brain roam around the elegance of Ohm's law overnight, I'm now seeing this.

A 100Wp panel ( assuming a 12v ouput)is capable of delivering 100/12=8.3A
Assuming no losses in th Elejoy (ridiculous I know) then this becomes 100/42=2.38A. A much more acceptable charge current. Of course this would only happen in full bright sunlight, so averagely would be less.
Considering that this would be for the occaisional van camping trip I think it would be more cost effective to pay the £5/night hook up fee, sting though it does.

I have looked at some combined battery/inverter combo's (they seem to be mislabelled as generators) and they are too expensive just for camping/bike use.
However, in consideration of the growing possibility of scheduled power cuts (think 1970's all over again), I may consider one. I have domestic P.V.'s which, in a power cut, will not generate as they receive no A.C. signal. With the installation of a suitable isolation switch to isolate from the grid, it may be possible to trick the solar controller into thinking it has mains by back feeding from a battery inverter, so allowing the panels to generate. Thus keeping freezers ,full of my veg garden produce, going, at least in daylight.
Control and safety implications need carefully thinking through here.

If you have a grid tie inverter, it will sense the mains going down, then shut off power to the grid. This is a safety feature, so you do not electrocute someone working to fix the faulty mains connection, by feeding back into the grid, so not good to play with this.

You'd be best to have a UPS connected to your mains, that only accepts charge in the daytime, when you are producing. Then if the grid goes down you can get mains from that.

 

[Nealh]

Cells in P esp decent 10a ones will be fine at 3a but one wuld have to limit solar wattage to 100/120w panels, somethin like Matts set up that uses 300w + @ 36v is going to be pushing 8a or so. What one has to be careful with is the charge connector type and rating. A generic commonly used one is the 5.5 x 2.1 connector, these are typically only approx.80w capable, my one gets warm with my new 44v 3a charger and is pushing a bit more then the 80w.

 

[WheezyRider]

Cells in P esp decent 10a ones will be fine at 3a but one wuld have to limit solar wattage to 100/120w panels, somethin like Matts set up that uses 300w + @ 36v is going to be pushing 8a or so. What one has to be careful with is the charge connector type and rating. A generic commonly used one is the 5.5 x 2.1 connector, these are typically only approx.80w capable, my one gets warm with my new 44v 3a charger and is pushing a bit more then the 80w.

Yes, that's something I take for granted. People with proprietary kit with low connector ratings may have issues above a couple of amps. I cut all the plugs off of my packs and went to XT60 as a minimum. I'm surprised Matt's MPPT Booster doesn't have a current limit setting. I'm sure the 7210 module does.

 

[matthewslack]

I have a new bike shed going in down my garden, could someone give a 'shopping list' with ballpark costs if I wanted a solar setup on the roof to charge my 52V 17.5ah battery? Happy for it to take as long as it takes to charge.

100W panel, a nice round number to work with, Renogy on eBay £83. Triplesolar I have used, seem to be on holiday at present.

For direct charging, which assumes a generic battery, a boost MPPT charge controller, Elejoy MU400SP is what I am using, $25 on AliExpress but long wait, or from Grin ebikes.ca with Anderson connectors fitted, via FedEx, in about a week, but more like £55, maybe a bit more, I bought 3 so spread the shipping costs.

Solar cables with MC4 connectors to get from panel to charge controller. A few quid.

Fuse holders in both solar input and battery cables. Very few quid.

Connector to suit battery.

Connectors to suit charge controller, I use Anderson powerpole 30A. A few quid.

Cable with Anderson PP one end, and battery connector the other. I solder up my own, using 2.5mm2 cable. A very few quid or from spares bin.

It is very simple: plus and minus cables from panel to charge controller with a fuse in the positive, ditto from charge controller to battery. That's it.

And multimeter for checking everything.

 

[matthewslack]

If you have a grid tie inverter, it will sense the mains going down, then shut off power to the grid. This is a safety feature, so you do not electrocute someone working to fix the faulty mains connection, by feeding back into the grid, so not good to play with this.

You'd be best to have a UPS connected to your mains, that only accepts charge in the daytime, when you are producing. Then if the grid goes down you can get mains from that.

Batteries and a Victron Multiplus would be one way to give you grid failure resilience.

 

[Nealh]

Renogy 175w.
Renogy 175W Solar Panel 12V Mono Off Grid Power RV Motorhome Camper Marine Van | eBay

Renogy 30W 50W 80W 100W 175W 200W Mono Solar Panel 12V Off Grid Power RV | eBay

200W 300W 400W MPPT Step up Solar Charge Controller Regulator 24 85V Voltage Adjustable For Lead acid Lithium Battery| | - AliExpress

 

[mr_ed]

So I can just pump 58v into the charge port continuously and the BMS will sort out the shut-off when fully charged?

 

[matthewslack]

So I can just pump 58v into the charge port continuously and the BMS will sort out the shut-off when fully charged?

It should do.

The charge controller will not push the voltage any higher, it will sit at the set voltage, reducing current as necessary.

 

[Nealh]

Set the voltage as per the max the battery expects to see.

 

[Nealh]

In #8 I mentioned lifpo4/prismatic cells for a static/storage battery, the example I gave was quite extreme at 280ah and £149 each module. For 12 v storage battery one would need 4 x 3.2 lifepo4 module connected in series for a nominal 12.8v battery.

If one wants to build their own storage battery then these look the buisness & one can soon get grade A Eve 105ah 3.2v modules via back order for less then £60 so a £280 for 105ah in lifepo4 is very good value, the cells are supplied with the appropriate buss bars and connecting bolts.
If one adheres to the 0.5c charge /discharge rate per module (which won't be hard to do/0.5c = 52.5a ) then they are rated for 3500 cycles. 2.5v - 3.65v typicall volatage range min/max.

One is still looking at £280 for four modules and a lifepo4 bms on top for balancing.

One moment, please...

www.fogstar-wholesale.co.uk

 

[Nealh]

Reasonably priced 300w sinewave step up inverters for storage batteries.

Pardon our interruption...

www.ebay.co.uk

Pardon our interruption...

www.ebay.co.uk

3DITM%26aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D1%26asc%3D240037%26meid%3D7eae0b80389d4d09a63a73c1cfda6acb%26pid%3D101195%26rk%3D2%26rkt%3D12%26sd%3D334335715420%26itm%3D334335714561%26pmt%3D1%26noa%3D0%26pg%3D2047675%26algv%3DSimplAMLv9PairwiseWebMskuAspectsV202110NoVariantSeedWithRevOpt90NoRelevanceKnnRecallV1%26brand%3DMercury&_trksid=p2047675.c101195

 

[WheezyRider]

In #8 I mentioned lifpo4/prismatic cells for a static/storage battery, the example I gave was quite extreme at 280ah and £149 each module. For 12 v storage battery one would need 4 x 3.2 lifepo4 module connected in series for a nominal 12.8v battery.

If one wants to build their own storage battery then these look the buisness & one can soon get grade A Eve 105ah 3.2v modules via back order for less then £60 so a £280 for 105ah in lifepo4 is very good value, the cells are supplied with the appropriate buss bars and connecting bolts.
If one adheres to the 0.5c charge /discharge rate per module (which won't be hard to do/0.5c = 52.5a ) then they are rated for 3500 cycles. 2.5v - 3.65v typicall volatage range min/max.

One is still looking at £280 for four modules and a lifepo4 bms on top for balancing.

One moment, please...

www.fogstar-wholesale.co.uk

The best prices there seem to be for "wholesalers" on their sites, how easy is it to qualify as being a wholesaler to buy from them?

 

[Nealh]

One doesn't have to be wholesaler to buy from them, all that is required is one meets the £75 minimum spend for delivery, under this amount one is directed to the dearer retail option.
I bought two weeks ago 24 x 21700 cells no issue with buying and before that the last buy was 24 x 18650 cells.

 

[Solarbake]

I have solar set up on my shed ,it powers most of the devices in the shed.
I have two 100 watt panels connected in parallel,they give out about 18v and nearly 9 Amps through a 10 amp photonic mppt solar charger on a really sunny day and only 2 amps in the winter months.
They keep two leisure batterys 12 v 130 amp hour each charged pretty much all the time.They then run a 2kw inverter which powers up to about 1500 watt devices without too much trouble.
My inverter is modified sine wave but I will upgrade to pure sine wave this year as some devices like my air compressor ,fridge will only run on mains.

 

[ErikaFrancis]

I know some folks might use a PWM controller, but I prefer the MPPT for its ability to convert voltage and current more effectively. Plus, it's super user-friendly and easy to install. In terms of components, you'll need a solar panel, battery bank, and charge controller. I like to use Renogy solar panels because they're reliable and high quality. For the battery bank, you can use a deep-cycle marine battery or lithium-ion battery for a lighter load. Just make sure your charge controller is compatible with whichever type of battery you choose. If you're not super handy, there are websites you can visit to buy that have all the components you need. Just make sure to get one that fits your bike and battery size.

 

[Oldie]

Last year I bought a Dokio 100w solar panel for £110 which charges my Yuasa leisure battery (used in winter for my diesel heater). Have subsequently paid £53 for a 300w Bestek pure sine wave inverter to plug my ebike charger into. Just all for fun really.