Green recharging

[scobo]

I have a couple of solar panels on my garage roof putting putting out 70 watts and use them to charge two laptops . I use a 20ah SLA as a buffer connected to a 75 watt inverter. The laptops chargers both draw around 30-40 watts so on a day of decent sunlight they charge no problem with this set-up.
I just bought an ebike recently and tried charging the battery (24v 8ah nimh) last night when the SLA wasn't charging from solar and got about 2 hours from it which is around half a charge (the SLA wasn't fully charged).
My ebike's charger draws 40 watts so on a sunny day it should charge fully no problem.
Unfortunately, the forecast here for the next few days is cloud and rain but I'll try it when the sun puts in an appearance again.
The solar panels cost £200 for the pair (ebay), the SLA was £50, charge controller £20 and the inverter £20.

 

[Carol]

Now being a woman do not understand all the technical things, and wont even if you explain it all to me but these are facts as I know them.

We had our Giant La Free Bikes for 5 years and always charged them up from the Solar Panel (85watt) with our inverter (700watt) always got them both fully charged no trouble. We always did them one at a time not together.

Now we have changed to Shwinn Electric bikes we charge their batteries up the same and have no trouble. Carol.

 

[Chris_Bike]

Now being a woman do not understand all the technical things. Carol.

Now I think it's clear from the rest of your post that you are fibbing (about not understanding, not about being a woman!)

 

[Terrytraveller]

Oh...rrrr !

Now being a woman do not understand all the technical things..... Carol.

I get caught on that one every meal time in the motorhome, I really don't see the difference in the motorhome oven/cooker and the electric one we have at home.

Regards Terry

 

[Chris_Bike]

Green re-charging - a postscript

Jeremy and I have both posted on the issue of re-charging from off-grid renewables and expressed the view that the output from a modified sine wave inverter should work fine with modern switch mode chargers.

Well, I have discovered that they don't - at least not with the Cytronex one!

I don't know why but there must be some quite sensitive electronics on the input side - it buzzed for a bit and then the lights went out. The fuses appear to be intact but I haven't had a chance to have a proper look yet.

Since green re-charging is an essential part of my plan (I am off-grid in Wales), I have bought a small sine wane inverter to run alongside the Xantrex monster that supplies the domestic 230v.

I just thought I would post this cautionary note in case others were about to go green!

 

[Terrytraveller]

Oops a daisy

Hi Chris,

Sorry to read your charger has failed will be very interested in what failed in your switched mode charger or inverter to cause it to give up the ghost. As you did advise me it would be in order to use a modified square wave inverter to charge the bike battery - I wonder if I will need to have your address just incase my charger fails so I can bill you

The Maplins modified square wave inverter I bought is recommended for use with a laptop, and these use the small switched mode multivoltage charger just like the ebike charger, i.e. 100vac to 240vac. so I don't see that the inverter could have pulled your ebike charger down - perhaps your chargers time was up and had to go to the other side whatever mains AC you had fed it

Perhaps the frequency of the inverter started to gallop away or perhaps thermal runaway on charger or ..........

I will keep charging mine in the motorhome every day whilst it is under guarantee, just to see what happens and report any problems back to the forum.

Regards Terry

 

[Chris_Bike]

Hi Terry,

I'm glad yours works OK and I'm sure it will continue to do so. Mine failed on the first try (I had been using the mains up till last weekend). My other Cytronex charger works fine on the diesel generator - but you would expect that and it rather defeats the object of green recharging!) I'm hoping Jeremy may have an idea since he knows a lot more about electronics then do I.

 

[Terrytraveller]

Testing the Inverter

Hi Chris,

I wonder how you propose to test the inverter if you don't have a scope? I have just made some tests on my inverter to maybe produce some benchmark data, as follows;-

I powered up the inverter with and without a 60 watt incandescent light bulb, and put a battery operated radio near by (six inches away from the inverter), I was able to get clear FM stations but a little interference on AM & LW.

Using the inverter to drive the radio instead of the internal radio batteries, I found I would get interference free FM on a strong station and a little mains hum between stations, but always have loudish interference on a strong station using AM & LW, between stations the mains hum was extremely loud.

With the input source showing 12.9vdc from the two 110amp leisure batteries and solar panel at 1900hrs this evening, the inverter output was 187vac, with and without a 60 watt incandescent 240vac bulb.

I was suprised that the Maplins 240vac 300watt inverter was only outputting 187vac (must be something to do with the meter looking for a nice pure sine wave and calculating the wrong RMS value on the modified square wave), just as well the switched mode charger works on voltages betwen 100vac and 240vac, most LCD TV adaptors work on the same wide vac converting the mains voltage to 12vdc.

If you are interested I will scope the inverter output waveform, mind you I haven't used the scope in 5yrs since I retired... I'm still in working condition but.........

Regards Terry

 

[Chris_Bike]

To be honest Terry, I'm taking the new inverter on trust. It's claimed to be "pure sine wave" and should be OK. My workhorse inverter is a Xantrex and produces a clipped square wave that works everything else I have ever thrown at it!

I am interested in trying to fix the charger, but my quick look didn't show up anything fried!

 

[Chris_Bike]

New inverter's fine

Just to close the story, I bought a 24v 600w (continuous) inverter from this guy (eBay UK Shop - Power Inverter systems: Inverters Pure Sine 12V, Accessories, Battery Chargers. It's great. I can charge 2 Cytronex batteries simultaneously with the inverter drawing about 11A from the DC side. The inverter was advertised £130 buy it now, but he took £105 as a best offer and delivered within 2 days. If anyone else is after a sine wave inverter, this guy is worth a look.

As an aside, the first inverter I ever bought was a 600W Ex-army, thyristor-driven sine wave job with massive transformers and capacitors. It weighed about 60 Kg. This one weighs 3.5 Kg - there's progress!