Charging an electric bike when off grid

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bobnwend

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I’m a newbie and I apologise if this has been asked before but can you charge two electric bikes when you are off grid or should we always plan to be on hookup to charge them? I have a 150 W solar panel, one leisure battery and no inverter at the moment.

As far as I can understand from my research a 4amp bike charger would drain a 100Ah leisure battery with a 1kw inverter in an hour and the Bosch battery in the bike requires 4.5 hours to charge fully, so can you help me with this please?
 
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Well yes, it has been asked many times. If you put e bike charging into the Search box (top right of this page) you'll get many threads and chapter and verse on solar, inverters, battery capacity.........but if you can't I'm sure folk will reply all over again to your post.
(My reply is purely intended to be helpful to you now and maybe as somewhere to start for answers to your future questions).

Here's just one of the many threads...........

www.motorhomefun.co.uk

Inverter/ebike battery charging

We have two Kalkhof ebikes, one charger is Input 230v50Hz 2.0A max Output 42v 4.0A and the other Input115/230v50/60Hz 3A/1.5A Output 36v 4A/1A What minimum size pure sine wave inverter should I use when not on hook up? Also when is it best to charge, whilst driving, sun shining and powering...
www.motorhomefun.co.uk www.motorhomefun.co.uk
 
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We charged our ebikes off grid without any issues. Our set up was a 1000w inverter, 215w solar panel, and 160ah of battery power. We only did it on sunny days to ensure we could easily top back up, and had enough power for everything else
 
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I keep our two ebike 36v 17ah batteries charged with a 12v-36v, 2amp charger, (no inverter).

100w solar, 100ah leisure battery.

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bobnwend said:
As far as I can understand from my research a 4amp bike charger would drain a 100Ah leisure battery with a 1kw inverter in an hour and the Bosch battery in the bike requires 4.5 hours to charge fully, so can you help me with this please?
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When doing energy calculations, you have to keep the amps together with its volts to get a sensible answer. I suspect the 4 amp figure was for the output of the 36V charger. The mains input of that charger would be considerably lower, because the voltage is higher (240V).

For power calculations, watts = volts x amps. In this case, if the charger output is 4 amps at 36V, the power output is 36 x 4 = 144 watts.

The mains input to the charger will be about the same watts, plus a bit extra to make up the efficiency losses. So let's say it's 160 watts. The mains voltage is 240V, so to find the amps, amps = watts/volts = 160/240 = 2/3 of an amp.

If that 160 watts is supplied by a 12V inverter, then the input on the leisure battery 12V side will be 160 watts plus a bit extra for efficiency losses, so call it 180 watts. The battery voltage is 12V, so the leisure battery amps is 180/12 = 15 amps.

If it takes 4.5 hours to charge the bike battery, then the inverter is taking 15 amps for 4.5 hours from the 12V leisure battery. That's 15 x 4.5 = 67.5 amp-hours. From a 100Ah leisure battery that's quite a lot, but not impossible, especially if the solar is contributing.
 
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I've gone down a different route....whilst travelling between locations, our eBike batteries are connected to the vehicle charging system via my 1000w inverter....the most efficient system for us....however....as we ride most days and perhaps not move we have other ways.
We often park-up at remote locations, during this time we have a small Honda generator, this is super efficient, quiet and charges up 2 batteries in about 3 hours...
Our latest system has been to add a 150w flat folding Solar Panel to compliment our 120w roof panel...this using our leisure battery as a buffer is charging our batteries very efficiently, still trialing this, but so far it works well while the rooftop panel has virtually gone for a Siesta, we have lots of sun here in Spain, so why not use it.
One final point is make sure your vehicle batteries are fully charged before starving them of power, my only leisure battery has suffered a little for not doing this.....enjoy your eBiking, we do, off today to ride the forest trails, sample the wine and enjoy the sun here in Murcia.
 
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irnbru said:
We used to charge ours through an inverter but now use a 12v charging lead instead and always try to charge the batteries as we are driving.
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Interesting...could you expand on your charging method please, what cable, and goes where?
 
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I charge both our e bikes during the day when the sun is shining. 185w solar and inverter.
I will also charge batteries on the move with inverter and B2B
I like the idea of an additional flat folding panel.
We are lucky as plenty of sun here in south France😎

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autorouter said:
When doing energy calculations, you have to keep the amps together with its volts to get a sensible answer. I suspect the 4 amp figure was for the output of the 36V charger. The mains input of that charger would be considerably lower, because the voltage is higher (240V).

For power calculations, watts = volts x amps. In this case, if the charger output is 4 amps at 36V, the power output is 36 x 4 = 144 watts.

The mains input to the charger will be about the same watts, plus a bit extra to make up the efficiency losses. So let's say it's 160 watts. The mains voltage is 240V, so to find the amps, amps = watts/volts = 160/240 = 2/3 of an amp.

If that 160 watts is supplied by a 12V inverter, then the input on the leisure battery 12V side will be 160 watts plus a bit extra for efficiency losses, so call it 180 watts. The battery voltage is 12V, so the leisure battery amps is 180/12 = 15 amps.

If it takes 4.5 hours to charge the bike battery, then the inverter is taking 15 amps for 4.5 hours from the 12V leisure battery. That's 15 x 4.5 = 67.5 amp-hours. From a 100Ah leisure battery that's quite a lot, but not impossible, especially if the solar is contributing.
Click to expand...
Nice one! This explanation should be put in the resources section. It could be used by anyone needing to size an inverter or work out the battery drain from an appliance.
 
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We always ensure we fully charge the batteries on our bikes on ehu where possible. When off grid and travelling we charge one battery at a time through an inverter. When static we charge each battery up in the mornings via leisure batteries/ inverter from 200watt solar on alternate days provided it's sunny.,usually a battery is recharged fully by the time we have had breakfast and ready to go out.
 
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Thank you all so much for your responses - so much information - and so fast! This is my first time asking for help and I am very grateful. I am afraid that I am going to demonstrate just how early we are on the learning curve with my follow up questions - so please be kind!!

Does it make sense to have a 12v charging lead as well as an inverter for when we are driving or can I carry on charging through the inverter whilst on the move?
What is a B2B?
How do I actually connect the inverter - do I need additional leads or does it just plug in?
Thanks again.
 
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Bosch used to sell a 12v charger for their ebike batteries but discontinued it - maybe 5 or 6 years ago - perhaps because it didnt work very well?

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I'm sure someone will correct me if I am wrong but here's my take .....

A 12v charging lead will be more efficient than going through an inverter - if you can get a 12v charger for your make / model of bike.

B2B is a back-to-back charging system and is said to charge the hab battery from the alternator more efficiently than a standard split charge system (when on the move / engine running of course). You may already have one.

Our inverter came with all leads for connecting to the 12 v supply and the 240 v output is a standard socket so we just plug in the appliance - in our case usually a slow cooker :)
 
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Hagstrom said:
Bosch used to sell a 12v charger for their ebike batteries but discontinued it - maybe 5 or 6 years ago - perhaps because it didnt work very well?
Click to expand...
Exactly....our Gravel bikes have Fazua motor/Battery system....as an additional extra they offer for 99€ a 12 v charger.....just in case you were having difficulties in deciding a Christmas present...if not my inverter cost about the same....works just as well...
 
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Hagstrom said:
Bosch used to sell a 12v charger for their ebike batteries but discontinued it - maybe 5 or 6 years ago - perhaps because it didnt work very well?
Click to expand...
I use a 12v charger for two 36v batteries (as stated above) it works very well albeit a bit slow.

I can never see the logic of fitting an inverter to a 12v supply to convert it to 240v, then convert it back to a much lower voltage, some even use this method to charge 5v phone batteries.

As well as charging 36v ebike batteries, I also charge a 19v laptop with a separate charger, (though not at the same time), inverters are fine if you want to run all your household appliances.

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After visiting Vanbitz, I use the van as I would my home for electrics.

Wake up in the morning, turn coffee machine on.

Charge up electrical appliances when needed and keep the boss happy….hairdryer.

Each to their own but embrace new technology as it comes along I say. I have an all singing all dancing satellite system on roof (fitted by previous owner) but I use mi-fi.
 
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jumar said:
Interesting...could you expand on your charging method please, what cable, and goes where?
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It’s a 12v charger, just plug into 12v source and other side into battery. Hope you can see in photos.<Broken link removed><Broken link removed>
 
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We recently took our 2 bosch batteries for ebikes to france
Set up is 120 watts solar, about 180 amps in battery and 1000 watt inverter
Because it was so hot we parked under a tree and the lack of electricity fill up was noticeable.
We then had less than enough bosch battery forcing us to battery management.
First thing to do was move the solar back into the sun then we charged one used it, charged the next, used it etc so we were going out with one battery on half charge each day.
Not content with this I started looking at other options and found that Bosch offer places in the Vaucluse (where we were) to charge your battery up for free.
So we tried it once, twice three times. Great system. Ride your bike to where youre going to and drop it off whilst you walk round town and come back and its charged. hotels, bike shops and tourist offices mainly. Quick google will find you places or search for "Bosch" written by me for link on here. I will add a screesnshot from my phone in a mo
Then we are hopefully going off to holland and Belgium next month so looked to see what is available to charge your bikes there. As expected they are all over the place. Holland has changed all ash trays in railway stations to e bike charging points ! Again info is readily available on google.

We will now try another holiday with bikes and this time charging not from our van but from resources around that are readily available. I am still trying to find a decent app for these locations but have saved the few thousand places available in Holland somewhere in a safe place on either my hone or computer and when I find that safe place I ll let you know !
Screenshot_2021-10-12-17-48-38-45_40deb401b9ffe8e1df2f1cc5ba480b12.jpg
 
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suavecarve said:
We recently took our 2 bosch batteries for ebikes to france
Set up is 120 watts solar, about 180 amps in battery and 1000 watt inverter
Because it was so hot we parked under a tree and the lack of electricity fill up was noticeable.
We then had less than enough bosch battery forcing us to battery management.
First thing to do was move the solar back into the sun then we charged one used it, charged the next, used it etc so we were going out with one battery on half charge each day.
Not content with this I started looking at other options and found that Bosch offer places in the Vaucluse (where we were) to charge your battery up for free.
So we tried it once, twice three times. Great system. Ride your bike to where youre going to and drop it off whilst you walk round town and come back and its charged. hotels, bike shops and tourist offices mainly. Quick google will find you places or search for "Bosch" written by me for link on here. I will add a screesnshot from my phone in a mo
Then we are hopefully going off to holland and Belgium next month so looked to see what is available to charge your bikes there. As expected they are all over the place. Holland has changed all ash trays in railway stations to e bike charging points ! Again info is readily available on google.

We will now try another holiday with bikes and this time charging not from our van but from resources around that are readily available. I am still trying to find a decent app for these locations but have saved the few thousand places available in Holland somewhere in a safe place on either my hone or computer and when I find that safe place I ll let you know !
View attachment 547402
Click to expand...
Totally brilliant...the way forward....of course not all batteries are Bosch....we have eMTB running Shimano and Gravel bikes using Fazua....however just how cool is this....😀🇪🇦👍
 
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And the link to the physical maps
www.motorhomefun.co.uk

Bosch free recharge points in Vaucluse

Does what it says in the headline. 60 recharging points at shops museums hotels tourist information gaffes where you turn up on your Bosch propelled cycle and hand over the battery while you go for a beer or sightseeing and come back and it's fully charged. Cracking system if you have a Bosch...
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Just to add the excellent advice above regarding charging regimes, it is unlikely you will need a full 4.5 hour charge most of the time, just top up what you use regularly. You never usually flatten the battery completely after all?

As for charging using a 12v (nominal) cigar socket. A cable with a cheapish boost converter and a suitable plug/socket for the bike battery is simple enough to make up. It will use far less battery charge to achieve what you need
 
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Welcome to the forum.
It's difficult to answer your question easily because there are so many variables.
One will depend on how fast your charger is. A lower wattage one will be kinder to your batteries, which don't enjoy a rapid discharge. A 2A mains charger (500W) will better than a 4A one (1kW), if you can find one. Charging with one of these will, of course, take longer.
Next, is how flat your e-bike battery will be when you charge it and what its capacity is. Some are becoming so large that their capacity is similar or even greater than that of a modest habitation battery.
The life of a battery is measured in cycles, but not all cycles are the same: a few deep cycles can age a battery much more than lots of light cycles which provide the same amount of power.
The best ploy is to charge whilst travelling. The engine's alternator will provide extra power and reduce the stress on the battery, but remember that it's going to take plenty of time and the cost of that power is not cheap (Diesel consumed).
There are e-bikes with as much as 1.5kWh battery capacity, now, but most tend to be 500Wh or less. The capacity of an 85Ah Gel battery could be considered to provide about 750Wh of power and you will need that for more than just charging the e-bike.
I have only charged when on hook-up, but would charge "on-the-run" if the need arose.
 
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TheBig1 said:
Just to add the excellent advice above regarding charging regimes, it is unlikely you will need a full 4.5 hour charge most of the time, just top up what you use regularly. You never usually flatten the battery completely after all?

As for charging using a 12v (nominal) cigar socket. A cable with a cheapish boost converter and a suitable plug/socket for the bike battery is simple enough to make up. It will use far less battery charge to achieve what you need
Click to expand...
Looks interesting...how about sharing your ideas here with what we might need to use this type of charging successful..I for one are open to anything that makes eBike charging more user friendly...
 
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