Electric bike charging

[hallii]

I am thinking of buying a couple of folding electric bikes.

 

I rarely use a hook up, but do have two 80w solar panels and about 200 amp hours of batteries.

 

How would I go on for charging the electric bike batteries?

 

hallii

[Guest JudgeMental]

may be worth asking over on e bike forum as well.....

 

http://www.pedelecs.co.uk/forum/electric-bicycles/

[Brian Kirby]

You'll need to know the capacities of the bike batteries.  I suspect you'll also need an inverter, to convert your 12V to 230V AC, so that the bike chargers can convert it back to (maybe 36V?) DC, so you will have some conversion losses.  So, assuming both bikes are used together, but are run reasonably, you'll need to take about the full capacity of one bike battery, plus conversion losses, from your leisure batteries in addition to your normal draw-off.  I think what you may really need is solar panels that work best at night!  :-)

[hallii]

OK Brian, I am waiting for the introduction of the Lunar Photovoltaic Panel!

 

As regards battery capacity it is around 9 ah at 36V Li-ion . I say around because there are are many variations.

 

After a bit of question asking I managed to speak with someone who knew some answers and he reckoned that the 12v to 36v inverter draws about 2A at 12v. (I didn't know a 12v to 36v inverter/charger existed!).

 

So charging two batteries would pull about 4 amps, the solar panels might just do it in bright Spanish sun , if not I suppose a slight draw on the two 80Ah leisure batteries would be OK.

 

So it seems I have answered my own question.

 

Now, all I have to do is choose which model.

 

Hallii

 

 

 

 

 

[w1ntersun]

What you really need is twp pedals on your bike so as you ride the bikes you could pedal and charge the batteries :->

[Brian Kirby]

Don't think I'd bother with a 12V - 36V inverter.  I assume the bikes come with a standard 230V charger unit?  I'd just fit a 12V - 230V inverter, and plug the standard 230V charger into that.  Then you can use the same inverter to charge/run laptop, phones, cameras etc etc.  Probably cheaper than a 12V - 36V jobby as well, but even if not, far more versatile.

[hallii]

I have resurrected this one, I am still on the hunt for electric bikes.

 

The figures given below are based on what I was told by a technical man at a suppliers.

 

It seems it is all wrong, a 230v charger running off an inverter draws 1.8 amps or around 400 watts at 230v.

 

That's 34 amps draw on the 12v batteries/solar panels, for two bike batteries that's 68 amps !! for 4 hours!!

 

With that sort of load it is out of the question, we rarely have hook ups and I would rather give up motorhoming than use a generator.

 

Now I know that in all probability that 1.8 amps is the maximum load at 230v and will depend on the state of charge of the bike batteries.

 

Now to my question, does anyone charge bike batteries in similar circumstances to mine? How do YOU get on?

 

H

 

 

 

 

 

 

 

 

hallii - 2010-08-02 1:40 PM

 

OK Brian, I am waiting for the introduction of the Lunar Photovoltaic Panel!

 

As regards battery capacity it is around 9 ah at 36V Li-ion . I say around because there are are many variations.

 

After a bit of question asking I managed to speak with someone who knew some answers and he reckoned that the 12v to 36v inverter draws about 2A at 12v. (I didn't know a 12v to 36v inverter/charger existed!).

 

So charging two batteries would pull about 4 amps, the solar panels might just do it in bright Spanish sun , if not I suppose a slight draw on the two 80Ah leisure batteries would be OK.

 

So it seems I have answered my own question.

 

Now, all I have to do is choose which model.

 

Hallii

 

 

 

 

[Guest JudgeMental]

I think you are probably wrong re current draw

 

if it helps our wisper chargers are input 230v 1.5 amp - output 42 V 3 amp

 

we have e bikes and charge on route via an inverter and via 230v on site. they have a range of approx 50 miles so a mains charge every 3-4 days does us......

 

why dont you ask over on pedelec e bike forum like I suggested? Lots of expert opinion....... and they are a friendly bunch *-)

[hallii]

I have been on Pedelec but so far no useful answer to my queries, your charger is a bit less than the one I am considering but nontheless yours is 345 watts or 28 amps at 12v ignoring conversion losses.

 

As mentioned we rarely have hook up so it's all down to the solar panels and van alternater.

 

H

 

 

JudgeMental - 2011-05-07 9:52 AM

 

I think you are probably wrong re current draw

 

if it helps our wisper chargers are input 230v 1.5 amp - output 42 V 3 amp

 

we have e bikes and charge on route via an inverter and via 230v on site. they have a range of approx 50 miles so a mains charge every 3-4 days does us......

 

why dont you ask over on pedelec e bike forum like I suggested? Lots of expert opinion....... and they are a friendly bunch *-)

[Guest JudgeMental]

your choices are probably to stick to non elecric bikes or change your style of camping......Many Aires have 230v these days? and cheap municipals or CL's for a night now and again hardly breaks the bank *-)

 

My batteries are large at 14Ah.wisper sell a 12v charger as well but we manage OK with inverter......... what bikes are you thinking of getting?

[Brambles]

Halli, no no no, you are getting comfused. The 1.5 Amps at 240 volts is a rating not the curent it actually draws. It wil be a max peak or spike of 1.5 Amps and all that figure tells you is teh suply must be capabable of supplying 1.5 Amps. In othe wards do not fot a 1 Amp fuse.

 

Same with ou put. Say ot is rated at 3 Amps 36 volts, it is cabable of suplying up to 3 Amps and this wil fall off as teh battrey charges.

 

 

So assume 9 Ah at 36 volts charges at lets say 1 Amp.

That is 9 hours at 1 Amp. I am going to totally ignore lossed and innefficiencies to keep this simple so you inderstand the basics. Then we can inmtroduce efficiencies and adjust accordingly

 

 

So, lets say 1 amps charg rate at 36 volts.

Using an invertor on a 12 volt supply the invertor has to supply the same power.

P = Volts x Amps = 36 x 1 = 36 watta

at 12 volts power required = same = 36 watts.

36 = 12 x Amps, therefore Amps at 12 volts = 3 amps.

 

At 240 volts, igboring losses etc, then again power = 36 watts.

so works out at 0.15 Amps. (240volts/36watts)

 

Just to clarify. Power = Volts x Amps. Or transposing then Amps = power/volts

 

Now we know maximum you need to put in batteries is 9 Ah, even allowing for inefficiences of charging as they will never be completly flat. So thats 9 Ah to be taken from your 12 volts batteries/solar panels.

Allowing for a 20% loss in yoru invertotrs or chargers then lets make it 11 Ah

 

...sorry going to have to stop here, I have a very painful right arm/hand just now with a trapped nerve and typing is really hard for me and need a break...will finish later or someone else can carry it on...sorry. must stop typing.

Jon

[Brambles]

Apolgies re above post....wil try again....

 

Halli, no, you are getting confused. The 1.5 Amps at 240 volts is a rating not the current it actually draws. It wil be a max peak or surge below 1.5 Amps and all that figure tells you is the supply must be capabable of supplying 1.5 Amps. In otherwards do not fit a only a 1 Amp fuse.

 

Same with output. Say it is rated at 3 Amps 36 volts, it is cabable of supplying up to 3 Amps and this wil fall off as the battery charges or be dependant on the charge charecteristics. So basically means it can supply up to 3 Amps.

 

 

So assume 9 Ah at 36 volts charges at lets say 1 Amp.

That is 9 hours at 1 Amp . I am going to totally ignore losses and inefficiencies to keep this simple so you understand the basics. Then we can introduce efficiencies and adjust accordingly . Gosh that sounds patronising!! I don't mean it to sound that way.

 

 

So, lets say 1 amps charge rate at 36 volts.

Using an invertor on a 12 volt supply the invertor has to supply the same power.

P = Volts x Amps = 36 x 1 = 36 watts

at 12 volts power required = the same = 36 watts.

36 = 12 x Amps, hence Amps at 12 volts = 3 amps.

 

At 240 volts, ignoring losses etc, then again power = 36 watts.

so works out at 0.15 Amps. (240volts/36watts)

 

Just to clarify. Power = Volts x Amps. Or transposing then Amps = power/volts

 

Now we know maximum you need to put in batteries is 9 Ah at 36 volts, even allowing for inefficiences of charging as they will never be completely flat. So thats 9 Ah to be taken from your 12 volts batteries/solar panels per 12 volts of your 36 volt battery. So you actually need 3 times the 9 Ah. Making it 27 Ah from your 12 volt battrey to charge

 

Looking at it another way, you need 1 amp at 36 volts. Thats means you need 3 Amps at 12 volts to achieve the same power transfer. So as you have 3 times the amps you have 3 times the amperehours, making it 27 Ah you need to take out of your leisure batteries to charge a 36 volt 9 Ah battey.

 

Allowing for a 20% loss in your invertors or chargers then lets make it 33 Ah. Thats like one third of your capacity of a 100 Ah battery. Sorry going to have to stop again as hand is getting really sore again. Oh hum, such is life, but hopefully you are getting a clearer pictire now.

 

Jumping way ahead, you don't actually have much of a problem if at all if your solar panels are producing over 5 amps and pint you back to your earlitr post where you mentioned you had answered your own question...... which indeed you had...

[hallii]

Brambles, well done!

 

You are right I was assuming the 1.8 amp at 230v was the actual current drawn, which of course it is not, if it was the bike battery would be well overcharged!

 

Happy with the knowledge that I will be able to charge the batteries I am off to have a look at these next week

 

http://folding-bikes.net/asbikes/electrobike-mk2-mk3-p-41.html?osCsid=23ae7e1074841fe6664010deda587f3e

 

Probably the MK 3 version.

 

H

[alan]

Hi All

We are definitely in the Judge's chambers on this one! We have a 300watt 12-volt inverter which we connect our bicycle batteries to whilst we're travelling. I'm very untechnically minded, particularly so far as electricity is concerned; however, this useage does not drain my leisure batteries and I have yet to be short of electricity. I can't see any problem with charging bike batteries - if they get too low, you can always go onto a site, do the washing and charge batteries!

Alan

[Guest JudgeMental]

alan - 2011-05-07 2:15 PM

 

Hi All

We are definitely in the Judge's chambers on this one! We have a 300watt 12-volt inverter which we connect our bicycle batteries to whilst we're travelling. I'm very untechnically minded, particularly so far as electricity is concerned; however, this useage does not drain my leisure batteries and I have yet to be short of electricity. I can't see any problem with charging bike batteries - if they get too low, you can always go onto a site, do the washing and charge batteries!

Alan

 

Yes indeed...... thats what normal people would do lol but not many normal people on here :-D

 

cheap folding bikes tend to be horribily under geared...I sugest you try them before buying.

[tomag]

Hi Judgemental do your wisper fit folded but upright under the bed in your Adria twin sp

[Guest JudgeMental]

tomag - 2011-05-08 8:00 AM

 

Hi Judgemental do your wisper fit folded but upright under the bed in your Adria twin sp

 

we have full size 905 and 705 bikes?. Having omnibike Sport 2 door fitted next Friday? this has a 50kg capacity. but will need to use a trailer lighting board as extra length of E Bikes obstruct rear lights a bit. will remove batteries when carrying (safer anyway) so weight about 40kg combined

[hallii]

My bike rack will take 60 Kg , so I could put full size e-bikes on the rack (minus batteries), but I would prefer them in the garage, that's why I am looking at folders. I am going to test ride one so I will check the gearing carefully, if it's to low geared maybe the crank sprocket can be changed?

 

The ones I am looking at are 18.5 kg each plus batteries.

 

H

[bolero boy]

Sorry to bring this old thread up again but i found it on a search and Bramble has given a lot of good answers to questions i had re charging via an inverter.

I am confident that with 2x90ah batteries i will be able to charge my electric bike batteries (one 11ah 36v and the other 12ah 26v) bit having tried my 36 v charger, the charger shut down....tested inverter on my tv all ok. Tested charger on mains, all ok.

I dont really know much about the inverted thats fitted except its probably cheap, low powered and modified sine wave...

Is the charger likely to only accept a pure sine wave current

I can easily fit a different/second inverter if this is likely to be the issue.

I will try the other charger tomorrow.

Thanks.

[Brambles]

The problem is likely to be the bike battery chargers are switch mode. Now were the problem lies is the peak current it draws during the output wave form, be it psuodo sine wave or true sign wave.

The battery charger may just be drawing a narrow spike of high current repeatedly. These spikes of current is more than the invertor is able to supply. As an average current over time it is fine but the peak loading is too high. It is often difficult to get switch mode chargers to work correctly on inverters

A different brand of bike charger may work fine, or a larger inverter. Another posiibility is the peak currents drawn by the switch mode supply/charger and then in turn by the invetror from the batteries is high enough to cause volt drops in the 12 volt supply leads to the inverter, Keep them short and connected directly to the liesure batteries,

[bolero boy]

Thanks, Jon.

I was thinking of getting a larger (300w/500w) pure sine wave inverter which would fit in a seat box very close to the batteries. The trouble is, i wont know if it will carry out this specific task until i buy it, tho, i suspect i could rigg it up 'on spec' sale or return if i explain the task....

Thanks again.

[bolero boy]

JudgeMental - 2011-05-07 10:15 AM

 

your choices are probably to stick to non elecric bikes or change your style of camping......Many Aires have 230v these days? and cheap municipals or CL's for a night now and again hardly breaks the bank *-)

 

My batteries are large at 14Ah.wisper sell a 12v charger as well but we manage OK with inverter......... what bikes are you thinking of getting?

Eddie, does your inverter work with your latest Bosch charger...Is it a pure sinewave inverter, is it rated at 300w?

Cheers.

[gocro]

My Giant bike charger is rated at 1.2 amps my Kalkhoff's charger is 0.6 amps your set up has loads of spare capacity to cope with either of these or even both together.

Fast chargers may use a higher current, but for a shorter time but with 160 watt panel and 120 amps of useable battery I can't envisage any problems.

[bolero boy]

Thanks Groco, we have an 80w solar panel to replenish the twin batteries.

[bolero boy]

Ok, tried the Panasonic charger on the inverter today, worked with no problems.

Panasonic rated at input 50/60 hz 62w, output dc 29.3v 1.8 amp

Bosch rated at input 50hz 1.5 amp, output 36v 4 amp

Is the larger output of the bosch unit likely to be the problem, do i need a bigger inverter for this one?