Electrical Advice Required

[GypsyTom]

Can I appeal to anyone who knows more about electrics than I do, which is 99% of the known world.

I want to charge my electric bike's battery whilst driving. The simplest method is to plug a small inverter into my cab's 12v cigarette lighter socket.

The info on the battery charger is:

Input: 115/230 VAC, 60/50Hz 1.5/0.9A.

Output: 42v DC/2A

How big an inverter will I need and is there a chance of frying my Transit's wiring?

Thank you.

[spospe]

GypsyTom

 

The power output for the inverter is given by the input figures of your battery charger, so in your case ......

 

230 volts x 0.9 amps = 207 watts

 

This is a very simplified view, but will give a good margin of safety.

 

Given that most small inverters run at about 90% efficiency, this translates into a power input to the inverter of about 230 watts, or at a nominal 12 volts, about 19 amps. This is beyond the capacity of cigarette lighter sockets, which are usually rated at 10 amps (the MK7 Transit socket is fused at 20 amps, which is too close for comfort).

 

I would wire a 300 watt inverter directly to the leisure battery (via a 50 amp fuse) and thus permanently install it, perhaps with a dedicated output socket for the battery charger and anything else you might want to charge, such as camera batteries, mobile phone, shaver etc. You will need to be aware that such a high use will run your leisure battery down quite quickly when stopped.

 

 

 

[GypsyTom]

Thank you for that. Not the news I wanted but that's life!

Wiring up an inverter directly to the battery is a logistical nightmare. I was hoping that I could solve it by just plugging in to my 12v socket but as you say, it's a bit close for comfort.

Thanks again for the swift response.

[Brian Kirby]

You'll need to get the inverter as close as possible to the battery, with fat wiring, and make the 220V wiring the longest run.  You could possibly install a relay, so that the 12V power to the inverter is cut when the engine is not running.

As the current draw with the engine running will be high, allowing for the need to re-charge the starter battery, the habitation battery, run the fridge, and possibly vehicle lights and wipers, as well as re-charge the bike, I wonder if the existing alternator and associated wiring will be adequate.

I also wonder if you may have to get any wiring alterations done by a Ford main dealer, as I believe the on board electronics continually monitor power consumption.  Dealers have to "tell" the Ford CANBUS about additional loads, to prevent interventions by the computer to restrict engine power, or giving spurious emergency warnings, as they are programmed to interpret unexpected power consumption as indicative of electrical faults.

If it isn't done right, you may find you need the bike to get home!  :-)

[GypsyTom]

Thanks, but I've decided that the simplest option is to book in to a site for a day and plug in!

[Guest Tracker]

GypsyTom - 2010-03-22 6:49 PMThank you for that. Not the news I wanted but that's life!

Wiring up an inverter directly to the battery is a logistical nightmare. I was hoping that I could solve it by just plugging in to my 12v socket but as you say, it's a bit close for comfort.

Thanks again for the swift response.

Why should wiring an inverter direct to the leisure battery be a problem Tom - unless it/they are hard to get at it is the simplest thing in the world to affix cables to a battery - depending on posts and clamp styles?I am by no means an expert on this subject but I have wired my own 650w inverter to my leisure batteries OK.Tell us what the problem is and what type of battery posts and clamps you have and I hope that an intelligent answer would be forthcoming from one of us.Bear in mind that most van alternators do not charge the leisure battery at much above 10 amps on the road so you might need to ensure that the engine is running for twice as long as it is charging the bike batteries to fully maintain the van's leisure batteries? How long does it take to charge the bike batteries fully?

[lennyhb]

Appears to be a bit of controversy with your figures the input figure is 207 watts but dc output is 84 watts I would expect the charger to at least 90% efficient probably much better. If the output is correct you would only require a 6-7 amp supply.

 

As you say you are not very good with electrics could you get a friend to check the mains current drawn, you need to check if with the battery flat so it is taking a full charge. Also the full current will probably only be taken during the first stage of charging probably only for the first 15-30 mins.

 

Have you asked the manufacture if they have a 12 volt charger that would be the most efficient option.

 

 

 

 

 

 

 

[Guest Tracker]

lennyhb - 2010-03-22 8:31 PM

Appears to be a bit of controversy with your figures the input figure is 207 watts but dc output is 84 watts I would expect the charger to at least 90% efficient probably much better. If the output is correct you would only require a 6-7 amp supply.

 

Beg to differ Lenny?

 

Surely the needs of the charger are dictated by its input wattage/amperage not it's output?

 

If so the inverter needs to supply a minimum of 207 watts at 230v for which the inverter will need a 207 watt input at 12v = at least 17.25 amps?

 

I am not that sure myself so apologies if my 'logic' is flawed?

[GypsyTom]

I took my new 'van into my supplier who looked at the set up and the batteries are extremely hard to access as they're cramped under a seat. The seat would have to be removed I think to access them.

The main problem however is the location of the inverter. The best place is in the garage but the cost of the several metres of very thick cable and the labour charges would be much more than the cost of the inverter itself.

I had the ideal set up in my last 'van but the batteries were in a bed locker, the inverter right next to them and a 13 amp socket was fitted on the front of the locker.

When we drove I could charge up a battery whilst driving without any ill effects. The battery isn't always flat and often just needs a top up but I would think that a full charge would take about four hours.

I'll have to give some thought about wiring an inverter in the garage, which is the ideal place but the thought of all that very thick cable running the length of the 'van is a bit off-putting.

Thanks to all who've helped anyway.

[lennyhb]

Tracker - 2010-03-22 8:44 PM

 

lennyhb - 2010-03-22 8:31 PM

Appears to be a bit of controversy with your figures the input figure is 207 watts but dc output is 84 watts I would expect the charger to at least 90% efficient probably much better. If the output is correct you would only require a 6-7 amp supply.

 

Beg to differ Lenny?

 

Surely the needs of the charger are dictated by its input wattage/amperage not it's output?

 

 

If so the inverter needs to supply a minimum of 207 watts at 230v for which the inverter will need a 207 watt input at 12v = at least 17.25 amps?

 

I am not that sure myself so apologies if my 'logic' is flawed?

 

If that is the case it must be the most inefficient charger in the world.

I would expect a modern charger with a switch mode power supply to be at least 90% efficient, if it's an old fashioned type with a transformer I would still expect better than 80%.

 

By your logic Rich it would be 40% efficient that would make it an heater rather than a charger, the energy has to go somewhere!

 

 

[Brambles]

Bike Charger output 42 volts 2 Amps max = 84 watts.

Divide by 0.85 (playing save) for efficency of battery charger = 99 watts.

Divide again by 0.85 for invertor efficiency = 117 Watts.

A lot will depend on how the charger switch mode input works but a 150 watt invertor should work.

The calculations are using peak max power, and will not be 2 Amps, more likely to be 20% under which gives a factor of 1.5 for the invertor.

 

The max mean current drawn will be around 9 Amps, which is not excessive from the leisure battery whilst being charged from the alternator. Makes life a lot easier to connect the Invertor to the leisure batteries. (edit - Tom, just read your post about difficulty accessing batteries)

So in theory should work. In practice...well , I shall leave that to further debate as to what might go wrong. Basically you are adding an extra 9 Amps max to the alternator to leisure battery charging circuit. This will reduce as the batteries get charged.

 

As Harry Hill would say on TV Burp, who is correct? "FIGHT".

[GypsyTom]

Oh dear! It would appear that our experts vary enormously. One tells me that I'll be consuming 19 amps, another only 9 amps.

One tells me that I should get Ford to do the wiring and another tells me that I'll be OK plugging into my cigarette lighter socket.

I would have thought that we are dealing here with something that is not a matter of opinion, but a simple mathematical calculation based on a formula that will be known to someone who understands these things properly.

Who is right? I'm hoping that it's Brambles because this will mean that I can simply plug in a 250 watt inverter and charge my bike battery as I drive.

The fact that it's plugged into the lighter socket means that it will only be drawing current when the engine is running, so there's no worry about it draining the battery when I'm stopped.

Help!

[Guest Tracker]

GypsyTom - 2010-03-23 9:53 AM

I would have thought that we are dealing here with something that is not a matter of opinion, but a simple mathematical calculation based on a formula that will be known to someone who understands these things properly.

 

Absolutely Tom - which is why I tries to avoid getting involved in the techy theory bit - cos I don't quite fully understand it all either!

[Brian Kirby]

I think, Tom, we are all trying to help to answer your initial question.  The problem is that the information you provided for the charger does not stack up.  It seems to require approximately 200 Watts of power in at 230V, but only produces about 90 Watts of power at 12V.  As Lenny has said, that makes it more of a heater than a battery charger, since the power lost (110 Watts) has to go somewhere, so will merely generate heat.  In short, it would be the world's most inefficient battery charger! 

But, in reality, that cannot be the case, so either the input figure at 230V covers a surge while the unit "reads" the battery state, and later reduces to a much lower consumption figure of around 0.5 Amp (which would approximate to the stated 42V output of around 2 Amps) leaving the stated output as representing a constant charge state, or one, or other, if those quoted figures is wrong.

My caution regarding connecting a 20A load to the battery is based on information I have had from my local Ford commercial workshop, on the assumption that if you are indeed taking 20A out, you will, in effect, be asking the alternator to replace those 20A.  If the 230V load is not, actually, the 0.9 Amp you quote, but only 0.5A (which would more nearly match the 2.0A output at 42V), then the problem should not arise, but it would still be wise to check.  What I was told is that if the on-board computer sees a current being drawn in excess of its default settings it registers this as a possible short-circuit and shuts down certain other functions, possibly putting the van into "limp-home" mode.  To avoid this, it is necessary to "tell" the computer to pass higher than default loads.  Make of that as you will.

[Brambles]

Please Brian, stop making a mountain out of a molehill. The figures are above. Just because my house fuse board is rated at 100 Amps 250 volts does not mean I use 25Kwatts of power, even at peak times.

[747]

Tom,

 

The first thing you should do is test the cigar socket with a meter when the ignition is off. It may still be live, which will mean your inverter is draining the engine battery. If that is the case, you will need to turn the inverter off when you switch the engine off.

[GypsyTom]

I'm tempted to give it a try. It worked on my previous set up with a 250 watt inverter connected right next to my two leisure batteries.

I only charge a bike battery when we're on a long run as I assume that there will still be sufficient output from the alternator to charge the other batteries as well.

My main concern is blowing up my Transit's electronics but, if the 12v socket is rated at 20 amp as has been said and my battery charger will only use 9 amps maximum, then shouldn't I be OK?

I have correctly transcribed the information printed on the battery charger. 

The information on the battery itself is: Phylion battery, DC 37v.

Thanks again for your collective advice.

[Brambles]

747 - 2010-03-23 2:03 PM

 

Tom,

 

The first thing you should do is test the cigar socket with a meter when the ignition is off. It may still be live, which will mean your inverter is draining the engine battery. If that is the case, you will need to turn the inverter off when you switch the engine off.

 

I don't think it really matters, if per chance it is live all the time then you just unplug when you stop the engine.

 

[Brian Kirby]

Brambles - 2010-03-23 1:42 PM Please Brian, stop making a mountain out of a molehill. The figures are above. Just because my house fuse board is rated at 100 Amps 250 volts does not mean I use 25Kwatts of power, even at peak times.

Sorry Jon, not my intention at all.  With my apologies to Tom for the OT, I understand that your fuseboard will have a higher rating than your actual peak consumption (and that the total of all the connected circuits will exceed the said 100Amps), but is not an appliance rating plate intended to state its actual requirements in terms of power?  I have always believed that was the case.  What am I misunderstanding: I am now seriously puzzled?

[AliB]

Brambles is on the ball here, the maximum rating of an electrical system does not mean it will run at this rating when an appliance is connected.

What 's the rating of the alternator, 80A plus? Probably way more, so why the worry about adding an appliance to draw less than 9A.

Canbus - nothing to do with it. Canbus is a network system to exchange information, mainly used in lights, handbrake, reverse and ignition circuits.

 

Have a look at some of the 12V electric kettles on the market. They are typically rated at 8A 100Watts. Or what about the ceramic car heaters/windscreen demisters you see advertised in the Sunday papers, over 15A.

[Brambles]

The information on the battery itself is: Phylion battery, DC 37v.

 

Sounds like you have a Li-Ion battery, does it state the capacity?

 

[GypsyTom]

Brambles - 2010-03-23 2:55 PMThe information on the battery itself is: Phylion battery, DC 37v.Sounds like you have a Li-Ion battery, does it state the capacity?

Yes that's right, it's lithium-ion. There's nothing on the battery but I found this on the web:

eZee bike now uses a Li Ion Polymer battery with a rating of 37V 10Ah or 370 Wh. It is intrinsically safe and there is all the protection that is required from an excellent Battery Management Circuit. The lightness at 3.1 kgs for the entire battery with casing and circuit. 1 year warranty with 70% retention of original capacity.

[Brambles]

Brian Kirby - 2010-03-23 2:50 PM

 

Sorry Jon, not my intention at all.  With my apologies to Tom for the OT, I understand that your fuseboard will have a higher rating than your actual peak consumption (and that the total of all the connected circuits will exceed the said 100Amps), but is not an appliance rating plate intended to state its actual requirements in terms of power?  I have always believed that was the case.  What am I misunderstanding: I am now seriously puzzled?

 

Because it is probably peak current not average.

If it was average or mean current then the power supply would be dissipating 120 ish watts. It would get very very hot, so straight away we can see it clearly is not so.

 

Your LCD tv probbaly has a rating of 5 Amps at 12 volts, thid does not mean it requires 5 Amps. An electric drill has a rating of say 350 watts, it does not draw 350 watts of power when not loaded. It is its capability under load, so clearly the rating plate again is not the whole story. A heater however would have a rating plate which matches the power consumption.

[spospe]

One of the problems with this thread is that it is difficult to give a comprehensive reply that covers all the points and is under about 3000 words length. Here is my attempt at summary (criticise it if you wish and I am sure that some will).

 

1) GypsyTom's cycle battery charger has two sets of rating figures, one for the input, which will allow for the initial switch-on surge and one for the output, which will allow for the initial surge when the connection is made to the cycle battery.

 

2) The input figures for the cycle battery charger mean that a 12-volt supply of about 19 amps is required for reliable start-up of the inverter with the charger connected to both the inverter and the cycle battery.

 

3) There is often a considerable difference between start-up surge and steady-state figures. As an example of this, our domestic freezer has a compressor rated at 180 watts, which at 230 volts equates to about 0.8 amps, yet the installation instructions specify a 13-amp fuse in the plug.

 

4) Very probably GypsyTom's inverter / cycle battery charger set-up will work perfectly OK when plugged into the cigarette lighter socket, but this is a potentially hazardous procedure. The only safe way to connect such apparatus is by following the data on all the rating stickers, it may be over the top, but it will be safe.

 

Proceed with caution ;-)

 

[Brian Kirby]

Brambles - 2010-03-23 3:22 PM

Brian Kirby - 2010-03-23 2:50 PM Sorry Jon, not my intention at all.  With my apologies to Tom for the OT, I understand that your fuseboard will have a higher rating than your actual peak consumption (and that the total of all the connected circuits will exceed the said 100Amps), but is not an appliance rating plate intended to state its actual requirements in terms of power?  I have always believed that was the case.  What am I misunderstanding: I am now seriously puzzled?

Because it is probably peak current not average. If it was average or mean current then the power supply would be dissipating 120 ish watts. It would get very very hot, so straight away we can see it clearly is not so. Your LCD tv probbaly has a rating of 5 Amps at 12 volts, thid does not mean it requires 5 Amps. An electric drill has a rating of say 350 watts, it does not draw 350 watts of power when not loaded. It is its capability under load, so clearly the rating plate again is not the whole story. A heater however would have a rating plate which matches the power consumption.

Good, thanks for that Jon, it is about what I had always understood, and what I thought I had said.  My point, however, was that surely even that peak current has to be supplied.  As that peak is high relative to my understanding of the Transit's default settings, drawing that much power, presumably immediately after starting when both starter and habitation batteries are also looking for charge, might cause the on-board computer to shut off other functions.  I'd hate Tom to have his nice new van to go badly wrong, so am repeating what Ford have told me.  He can check it out with Ford.