Charging ebike batteries using solar panels? (1 Viewer)

[The Nomad]

Hi guys - we are in the early days of considering getting two ebikes.

They'd likely be 16 or 20 inch wheel folders, as they'd have to be stored in the overcab part of our motorhome.
We wouldn't need massive distance-munching capacity; perhaps 30 or 40 miles maximum per day, and mostly less than that.

But there's one issue that might be a deal breaker for us...... Ebike battery recharging without mains hookup.

We live here in the very sunny Costa Blanca region of Spain and go away for quite long periods....normally to other, similarly sunny mainland European countries. But we almost never use full facility campsites, but instead prefer Aires or simply wild camping. Thus we almost never use mains electric hookup when touring.
We rely on our 3 roof mounted solar panels. They total a notional 220 watts.
We are very low users of 12volt DC electrics in the MH, all lights are leds, we rarely watch any tv and if we do it's watching preloaded films/series on a portable laptop not a big "proper" tv.
The laptop take 19 volts, so we recharge it via a 12volt DC socket in the MH through a universal 12volt-to-19volt transformer.

We've got two, matched, really good quality leisure batteries (120 amp each from memory), which we hardly ever dip into much though the hours of darkness, before the next mornings sun tops them back up.
We can go indefinitely, parked up week after week after week without any electric hookup.

We've also got a little plug-in-to-12-volt socket 150watt mains inverter which I use for my mains razor,, and also a hard-wired-in whopping 2,000 watt mains inverter too (for running wife's hairdryer and hair crimper thingies 2 or 3 times a week).



So, to the questions:

1.If we had 2 pedal-assist ebikes, how much juice does it take to recharge their batteries if we did (say) 10 to 20 miles per day?
2. Would 3 or 4 hours of our solar panels output provide enough for them?
3. Could we use a simple dc step transformer to get us from the notional 12volt dc of the van to the "X" volts that their charger needs?

Many thanks for any help or advice on this!

 

[Alistair33]

I'm interested in the answer too. If it helps anyone answer the question a quick look and ebike batteries appear to be 36v and anywhere between 7 - 10ah

 

[Camping Gaza]

If you are in the dark about charging, up down/ dc to dc, don't know or can't work out your ebikes battery voltage/amp hour rates etc, I would charge the ebikes using the supplied charger and an inverter. Your 2K watt one would be all ok for that. Then once charged you need to work out how much has gone from your battery bank. You will need to measure that in amps to work out how much you need to put back.

not easy is it! too many variables in the equation.

I would check the voltage of the battery bank before charging, charge bike, then check voltage. Let solar do its magic and see how long (time it) before you get the voltage back in the bank. If its around a few hours I would be a happy camper. If not I would get more solar or a B2B charger if its not too far off.

PS why the heck do you use a 150 watt as well as a 2K inverter for a shave? use the main hard wired one and ditch the 150 watt death trap.

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[funflair]

Well a 36 volt by 10 ah battery would need about 30 ah from your 12 volt batteries, add a bit for losses through the inverter if you like and call it 40 ah, this should not worry a decent battery bank with 2x120 ah batteries and 220 watt of panels in the sun should put this back in 4 or 5 hours so I wouldn't worry.

Martin

EDIT should add that these back of fag packet calc's are for one 36 volt 10ah battery from flat but you said two bikes so charge from 50% would be the same or charge them alternate days

 

[cookie]

we have 2 36v ebikes which we charge either while driving via the inverter, or inverter while stationary, never been a problem in summer, as solar panels keep up nearly with output to inverter

 

[The Nomad]

If you are in the dark about charging, up down/ dc to dc, don't know or can't work out your ebikes battery voltage/amp hour rates etc, I would charge the ebikes using the supplied charger and an inverter. Your 2K watt one would be all ok for that. Then once charged you need to work out how much has gone from your battery bank. You will need to measure that in amps to work out how much you need to put back.

not easy is it! too many variables in the equation.

I would check the voltage of the battery bank before charging, charge bike, then check voltage. Let solar do its magic and see how long (time it) before you get the voltage back in the bank. If its around a few hours I would be a happy camper. If not I would get more solar or a B2B charger if its not too far off.

PS why the heck do you use a 150 watt as well as a 2K inverter for a shave? use the main hard wired one and ditch the 150 watt death trap.

Inverters - why two? Accident of history.
We already had the little 150 watt one before I bought and fitted the biggie.
The big one when switched on feeds one mains plug socket ...which is in the kitchen area, and not in the bathroom where I shave.
But there is a 12 volt dc socket in the bathroom, so it's easier just to plug my mains razor into the little inverter which I keep in there and then plug that inverters 12 volt plug into the bathroom socket.
I could spend ages running a cable and installing a second mains socket from the big inverter into the bathroom, but to to be honest I can't be arsed, as the present setup works fine.

On ebike battery charging - I thought as they are DC batteries that it would be more efficient to charge them via a dc step transformer connected into my 12 volt DC, rather than via an inverter. Is that not the case?
(I assumed there'd be quite a bit of loss in the several stages of using an inverter which would take 12 volt DC from my leisure batteries, convert that to 220 volt ac, then pass that to ebike charger, which then would change it to dc once again and supply "X" (36?) volts of charge to the actual ebike battery.)

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[Camping Gaza]

rather than via an inverter. Is that not the case?

You don't get that much loss through an inverter, sure the bigger they are the more you loose but it's not worth worrying about. Its a few amps/watts not like you are driving the heating or air con off it.

I have a similar set up to you, 300w on the roof, 3x 120ah batteries and low draw, all led no tv. I charge everything through it, Laptop, torch batteries, radio batteries, the lot and loose very little voltage so a couple of e bikes will be fine if you have all that sun hours too.

I was going to get an ebike, but have re furbed my 20 year old mountain bike which I will try until it kills me then I'll convert it to electric myself and charge it off the inverter.

 

[Jimbohorlicks]

we have 2 36v ebikes which we charge either while driving via the inverter, or inverter while stationary, never been a problem in summer, as solar panels keep up nearly with output to inverter

What kind of inverter have you got -is it a pure sine wave , modified etc.? Thanks

 

[Camping Gaza]

But there is a 12 volt dc socket in the bathroom, so it's easier just to plug my mains razor into the little inverter which I keep in there and then plug that inverters 12 volt plug into the bathroom socket.

I would strongly suggest you don't get that 150 watt inverter anywhere near you bathroom or anywhere where there is water. You are converting 12v in 240v remember!

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[Arewethereyet]

Hi Nomad, aside from the charging issues you are inquiring about have you actually borrowed or tried lifting a folding electric bike up into the overhead locker, the reason I ask is we have a couple of Batribike Dash models and these are made mostly out of aluminium and with the batteries removed I would say they still weigh a good 19kg each, now I'm in my mid fifties and would say I'm reasonably fit and healthy but I tell you I wouldn't want to go lifting them up to somewhere like that, when they are folded they have got to be the most awkwardest things to handle when on their sides.

 

[cookie]

What kind of inverter have you got -is it a pure sine wave , modified etc.? Thanks

modified , 4000 w peak power, bit big but it came with the van, last van had 700w modified

 

[Floydster]

You'll be fine, we've got 2 bikes 36v batteries, if the weather looks a bit iffy regards solar input I charge on alternate days, 100w tracker panel 360 Ah batts.

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[Robert Clark]

We charge our batteries when we're driving along

 

[laird of Dunstan]

We have a couple of hefty ebike batterys for our Haibikes,we charge them off of our 600w inverter,that inturn is backed up by two solar panels and 2 x 85 Ah batterys ,im thinking of adding two more batterys and a larger inverter ,so far the panels and batterys allow us to charge the Haibaikes each day.

 

[Electraglide]

These are a lot of money, are they worth it?

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[tonyidle]

I would strongly suggest you don't get that 150 watt inverter anywhere near you bathroom or anywhere where there is water. You are converting 12v in 240v remember!

Bathroom razor sockets are fitted to some MHs and comprise an inverter with a shaver socket - albeit in one box that hides the inverter part. Water and electricity are no more or less dangerous than metal and electricity. Water is a bit sneaky but if it enters mains-powered equipment it will normally kill it long before it might become a hazard to a human. Water in MH bathrooms is unlikely to be connected to earth so even that is no more dangerous than touching the kitchen sink.

 

[Reallyretired]

Two inverters Tush. I have three which came about more or less accidentally.

I originally fitted a 500w Mod square wave for the sole purpose of running a small twin tub washing machine. This drives one double socket conveniently sited for said washing machine though is also used to run the electric blanket when needed. Then SWMBO wanted to use a hairdrier so got a 2000w Mod square wave to power the rest of the sockets. I then found that our toothbrush chargers were burning out on the Mod Sq Wave so got a small PSW inverter (300w) to run the shaver socket in the washroom.
It is my intention when (if) funds admit, to replace the whole lot with a largish PSW inverter, however there are always more urgent, or more interesting things to spend money on.

Also have observed that PSW inverters are much larger and twice the weight of modified square wave ones so wouldn't be a straight swap.

 

[Camping Gaza]

Yeah unlikely to kill but would I trust it? hell no

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[Camping Gaza]

inverter with a shaver socket

I would hope that any shaver socket would have an isolating transformer built in before it's attached to the inverter. I'm not a fan of bathrooms and 240v, or even fans in bathrooms and 240v

 

[Camping Gaza]

"It is my intention when (if) funds admit, to replace the whole lot with a largish PSW inverter, however there are always more urgent, or more interesting things to spend money on."

Yeah funeral plans are a good investment for motorhomers by the sounds of some of the posts regarding 240 volts, hookups and the like on here lately!

 

[DBK]

I would hope that any shaver socket would have an isolating transformer built in before it's attached to the inverter. I'm not a fan of bathrooms and 240v, or even fans in bathrooms and 240v

An inverter is effectively an isolating transformer so you won't get a shock just touching one wire. You would need to touch both the 240v terminals to complete a circuit. Which of course could happen so it is potentially dangerous*.

*Pun unintentional.

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[Camping Gaza]

You would need to touch both the 240v terminals to complete a circuit.

Hey, I can do that! and several children I know.

 

[Lenny HB]

We use a 1000 watt pure sinewave inverter to charge our Bosch powered e bikes, went for a pure sine as didn't want to take a risk it with the price of Bosch chargers and a 1000watt so we could charge both batteries at the same time.
Recharging after 20 miles or so of use is sensible, we found when we charged both of them from flat it took 80a/h out the batteries which took several days with 200 watts of solar to recharge in northern France in June but did have crap AGM batteries at the time.

 

[Lenny HB]

These are a lot of money, are they worth it?

No, if you want to charge two bikes at the same time you would have spend 300 quid and they take twice as long to charge compared to the standard mains charger.

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[Lenny HB]

I would hope that any shaver socket would have an isolating transformer built in before it's attached to the inverter. I'm not a fan of bathrooms and 240v, or even fans in bathrooms and 240v

All the Motorhomes we have had have a standard 230v socket in the bathroom doesn't bother us using it as the van electrics are fed via an RCD.

 

[Bailey58]

Plenty of answers on the charging issue but I wouldn't fancy lifting two ebikes into the overhead cab even without the batteries.

 

[The Nomad]

Hi Nomad, aside from the charging issues you are inquiring about have you actually borrowed or tried lifting a folding electric bike up into the overhead locker, the reason I ask is we have a couple of Batribike Dash models and these are made mostly out of aluminium and with the batteries removed I would say they still weigh a good 19kg each, now I'm in my mid fifties and would say I'm reasonably fit and healthy but I tell you I wouldn't want to go lifting them up to somewhere like that, when they are folded they have got to be the most awkwardest things to handle when on their sides.

Thanks for that. But as luck ..or a lot of weight training... would have it although mid 50's, lifting those sort of weights into isn't

I would strongly suggest you don't get that 150 watt inverter anywhere near you bathroom or anywhere where there is water. You are converting 12v in 240v remember!

Why not use it in bathroom?
The inverter is itself fuse protected. The whole circuit is also trip protected at the MH control panel.
Standing on lino in the bathroom on top of a ply floor with inverter sat on plastic shelf isn't a route to earth.
(I think it's 220 volts AC not 240 volts?)

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