Charging e-bikes – a question.

[Wilf]

Calling all e-bike owners. Can you answer a simple question please?

 

How do you charge the battery when you are not on EHU, or do you have to stay on sites with an EHU so you can use your e-bikes?

 

[gocro]

It is perfectly feasible to charge using an inverter, providing you've got a large panel and sunlight. Our Giant bikes charger uses 1 amp whilst the Kalkhoff uses 330mA but takes a longer time to charge.

[Guest JudgeMental]

Nothing's ever simple

 

Its best not to deplete a battery as it can damage them, short top up charges best practice. this can be done on the move via a decent inverter. or as Gordon says solar panel if static and no ehu. the better batteries like Bosch, fully charge from empty (not good idea!) in 2.5 hrs, and 80% charge in 1.5 hrs. but cheaper batteries can need up to 8 hrs to charge.

 

it really all depends on what bikes and style of travel to be honest. Batteries need careful maintenance if they are going to last! you cant just leave them in the shed over winter and expect them to behave when you get them out in the spring! should be stored at approx 60% full (not full!) and a brief top up charge every month or two. this is the problem with buying used bikes, you really don't know if they have been maintained, and the battery usually the most expensive component 8-)

[Wilf]

I would agree ….. “Nothing's ever simple”.

 

I was hoping that someone had found a 12volt in-car charger?

 

Already have two e-bikes and we charge the batteries up after the e-bikes have been used. Normally 30 to 40 minutes on charge.

 

We have had the e-bikes for 10 months but we miss aires and wild camping.

 

The battery chargers show an input of 100 – 240 VAC 50/60Hz 90W with a DC Output of 36V 2A.

What would be a decent inverter: something that could handle 90W, but is it that simple?

 

[Guest JudgeMental]

the only firm that I know of the that do a 12v car charger for e bike batteries is Wisper, but that will have connections for their batteries I would think. But you honestly don't need one, just use an inverter. How long are you going to stay on an Aire for anyway, just charge as you drive...Or fit a solar panel if camping off grid for any length of time, but if you have 2 leisure batteries that may well do anyway

[mikejkay]

I've been trying to get reliable information on this problem since I started looking into getting an ebike.

 

I have seen references to using a solar panel and I assume that this would be via an inverter. A small solar panel would, I think, provide insufficient voltage to charge a 24v or 37v battery.

 

As far as inverters are concerned I would buy a larger capacity one so that it does not have to run at "full throttle". My main concern with an inverter is that the non pure sine wave variety might damage a sensitive intelligent charger.

[Guest JudgeMental]

You can buy Chinese pure sine wave inverters for approx £60-70.

 

[gocro]

There's no need to break the bank you only need a 300 watt inverter to charge the battery at 1 amp using the dedicated charger.

[Mel B]

I have been looking into this very matter as we are now the owners of 2 new electric bikes! How to charge there was a consideration and until we could find a way to do so we did not purchase, any.

 

We bought a Chinese "500W / 1200W Pure Sine Wave Power Inverter" off Ebay for £33 delivered.

:-D I was advised from 'someone in the know' that a pure sine wave was best. We'll use this to charge up the batteries on the run. I haven't decided yet whether to just wire in a single trailing socket (fused again) which can be left dangling under the bed (safely), or to put in a 13amp type (fused) socket and wire it directly to the leisure batteries - the latter will be neater and as I have already moved the heater/boiler controls from under the bed to the side of the wardrobe I already have a suitable 'hole' in the bed base to use for another socket (currently blocked with a socket surround and blanking plate).

 

We already have a solar panel so may be able to use the inverter when we're static if really needed but I'd rather not.

 

We will still use aires but as they have bornes if we really need to, we could pay for the electric hook-up for a while and use that to charge the batteries up.

 

We may also use a campsite once a week/fortnight, not only to charge up the batteries, but also to do washing, have showers etc (we prefer to have strip-washes in the PVC).

 

So, it's not impossible and as I understand it, it is better to keep the batteries topped up, rather than let them get low (as you would for a leisure battery), as not only is this better for them, but you could also ensure that they give a better 'distance' and last longer (age-wise) than recharging from less than 50% each time.

[mikejkay]

Mel - you need to be carefull about wiring an invertert directly to a 12v battery and then wiring the inverter a.c. output to a fixed 13a 240v socket. The temptation will be to plug in a high wattage 240v device which would cause undersized connections between the inverter and the battery to overheat and, possibly, cause a fire. Also, as I understand it, a permanently wired inverter will cause a current drain even if there is nothing plugged in.

 

I have looked into doing just this in order to run the lowest wattage microwave that I can find (a 700w output power micowave requires about 1000w input power). The 12v DC wiring needs to have an in-line battery isolating switch. The 12v DC wiring needs to be capable of about 100amps in order to keep the voltage drop due to the resistance of the cables to acceptable levels.

 

I sense the beating of wings, perhaps our resident expert and prolific poster will enlighten us.

 

Your 500W / 1200W Pure Sine Wave Power Inverter is, I suspect a 500w model that can cope with a 1200w short term spike. If you run anything that requires more than 500w for more than a short period the chances are that it will fail. Personally, I would limit the power of any appliance to 400w. When any electrical device is switched on there is, to a greater or lesser extent, a power surge. This is why most light bulbs fail when they are switched on.

 

 

 

 

[tonyishuk]

Slightly o/Topic, but my Ebike manufacturers recommend charging the battery after use and once every two weeks when not in use,

 

Rgds

[Mel B]

mikejkay - 2014-04-19 7:53 PM

 

Mel - you need to be carefull about wiring an invertert directly to a 12v battery and then wiring the inverter a.c. output to a fixed 13a 240v socket. The temptation will be to plug in a high wattage 240v device which would cause undersized connections between the inverter and the battery to overheat and, possibly, cause a fire. Also, as I understand it, a permanently wired inverter will cause a current drain even if there is nothing plugged in.

 

I have looked into doing just this in order to run the lowest wattage microwave that I can find (a 700w output power micowave requires about 1000w input power). The 12v DC wiring needs to have an in-line battery isolating switch. The 12v DC wiring needs to be capable of about 100amps in order to keep the voltage drop due to the resistance of the cables to acceptable levels.

 

I sense the beating of wings, perhaps our resident expert and prolific poster will enlighten us.

 

Your 500W / 1200W Pure Sine Wave Power Inverter is, I suspect a 500w model that can cope with a 1200w short term spike. If you run anything that requires more than 500w for more than a short period the chances are that it will fail. Personally, I would limit the power of any appliance to 400w. When any electrical device is switched on there is, to a greater or lesser extent, a power surge. This is why most light bulbs fail when they are switched on.

Mike, totally understand your concerns - I've wired an inverter before without a problem so know how to do it safely - I did it that time by putting an in-line switch and fuse between the inverter and the battery which was always turned off when the inverter wasn't in use to ensure no power drain and for safety (bit like turning a TV off at the wall socket rather than having it just turned off on the set itself), and also made sure that the cabling was more than sufficient too (from memory I think I used some jump cables!). The inverter is a bigger size than really needed but, as you correctly state, it is the initial draw that can cause a spike, so getting something with spare capacity seemed to make sense, hence what we have bought. I've already put in an extra 12v socket to power the TV which is directly linked to the leisure batteries, again with an in-line fuse and switch, so the socket is only live when we want it to be.

 

I was proposing to only wire a socket to the battery, NOT the inverter itself which would just be plugged into the socket when needed therefore no problem with power drain/safety and as it wouldn't be 'enclosed' it would be able to dissipate any heat it produced. The socket would be clearly marked and I can assure you I wouldn't be tempted to use it for any high-draw equipment, also in the future when we came to sell I'd remove the inverter and any trace of it so a new owner wouldn't have a problem either.

[mikejkay]

Mel - sorry to try and teach my grandmother to suck eggs! If you are going to run heavy cables to a dedicated socket what socket do you propose to use? Even the continental "cigarette lighter" sockets can't cope with high currents.

[Mel B]

mikejkay - 2014-04-21 12:54 AM

 

Mel - sorry to try and teach my grandmother to suck eggs! If you are going to run heavy cables to a dedicated socket what socket do you propose to use? Even the continental "cigarette lighter" sockets can't cope with high currents.

I was planning on utilising a mains type socket which would be wired to the batteries (suitably labelled of course), we'd then plug the inverter into that as/when needed, however we're not going to bother now as the draw for the charger is going to be no more than 6 amps based on the below equation:

 

Maximum output from charger: 42.7v @ 1.4 amps

Rounded up to: 48v @ 1.4 amps (to allow for inefficiency/losses)

48v ÷ 12v = 4

1.4 amps x 4 = 5.6 amps

5.6 amps x 12v = 67.2 watts

 

So, as we have a dash socket rated at 180w with a 15 amp fuse, we'll use that instead and save having to do any wiring at all. :-D

[mikejkay]

My charger output is 42v at 1.8a so I need about 76 watts. If I allow for 80% efficiency the power required increases to 95 watts, still less than the 180 watts supplied by the dash socket on a 130 multijet.

 

I'm still mulling over getting a low power microwave but even a 700w watt output microwave needs about 1000w input power. I like the idea of running the 12v to a socket but I'm having difficulty finding a suitable socket. I,m not keen on using a standard 13 amp domestic socket as someone might decide to try and use it. for a mains device. As I write this I have just had a (brilliant?!) idea. I could wire up connecting cables using the old round pin plug/socket. Even the 5a socket should be able to cope with 1200 watts and there would be no possibility of an incorrect connection. Any electricians out there who can tell me why this would be a bad idea?

[Mel B]

Mike, great minds think alike, I too was considering a 'non-standard' type of mains socket for the direct link to the leisure batteries to avoid any confusion, but don't need to bother now.

 

Screwfix do them:

 

http://www.screwfix.com/p/round-pin-socket-5a-white/92273

 

As do others, as well as plugs to go with them:

 

amazon

 

There's a download on the MH Fun forum which might prove useful to you - if you can't get it yourself PM me with your email and I'll send it on to you:

 

http://www.motorhomefun.co.uk/tech-mech-general/83796-new-12v-socket.html

[mikejkay]

Thanks for the links. I went to my local junk store, otherwise known as my basement, where 30+ years of bits and bobs have accumulated and found the necessary without too much trouble! Before I start hacking the van about to fit a socket I'll try setting it up with 2x4mm sq wires (also from the basement) and see what I can run without things getting too hot.