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Hi,

Apologies if repeated or noob question! I'm planning on buying the new Zoe later in the year. I currently have an old diesel yaris and regularly use is to run electrical equipment via an oscillator. Can happily draw 2kw from it for a little while with engine off, if more then 10mins I run the engine and it ticks over in tiny-diesel happiness. Have been on same battery since new (13 years), not least because I run the car every day, a lot (240,000 miles so far!) so the battery is never allowed to get discharged and has lasted very well.

Anyway, on to my actual question: If I were to say want to run a 1kw lawn mower from the 12v in the Zoe, assumed I engaged any and all appropriate modes, e.g. 'turning it on', in order to allow the lithium ion cells to charge/supply the 12v battery, would this be possible? If it is just a lead acid, low impedance, battery which is designed to run lots of on board systems, is there any reason I can't hook up external loads to it?

Very happy to be told "No, that's silly! You're an idiot!" I won't be hurt, but technical reasons would be good :) Perhaps it is known that the main battery can only supply 14v to charge the 12v at 5A and it trying to kick in while a large drain was still attached would cause the electronics stepping down the main battery to 14v to overheat. I can imagine some restraint like that. Nice thing about big car alternators is they can really kick out a lot of of power, but battery - to - battery voltage regulators are unlikely to be overspeced enough to handle a hedge trimmer! I just figured there was a small chance someone might be running a 4kw speaker system off theirs already and having no issues :)

Thanks,
Danny
 

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The Zoe manual specifies that the 'accessories' (aka cigarette lighter) socket can supply 120W at 12V - i.e. 10 amps nominal.

I don't know how the peak current from the DC/DC converter (400V down to 12/14V) to charge the 12V battery compares to an alternator. Quite possibly less, but I wouldn't try to take more than about 10A from the 12V battery on an ICE in any case.

On the Zoe, the DC/DC converter is switched on if you do almost anything - open a door ... And it times out after a few minutes if you then do nothing. So the 12V battery is receiving charge more of the time that one on an ICE does.

I believe the DC/DC converter is active all the time once you have STARTED the car (pressed the START button so that the accelerator pedal does something), just like the alternator on an ICE.

Putting the key card in a slot in the car simply connects 12V to the accessory socket (and radio etc), much like the first click of key on an ICE. I don't think that this guarantees that the DC/DC converter will stay active (just that you have 12V available) but it will be some of the time.
 

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Discussion Starter #3
Thanks for all the detail and the speedy response!

I'd be wiring the oscilator straight to the terminals of the battery so in theory one could ignore the manufacturer's limits from the CigSocket. However, I think, per your details on when the DC/DC regulator might be switched on (a lot by the sounds of things), I think it would be too risky to try to draw more than the 10A you mention even straight from the battery. If I understand correctly, the incredibly low impance of lead acid batteries would mean that most current would come from there, but if the DC/DC was enabled and it was some snazzy new electronics beyond the comprehension of my 20 year old physics degree (so basically ANYTHING at all), then a lot of current may be forced from that and hence blow me and my new car up.

120w is sadly a bit low for gardening equipment.

Never mind, it was an idea. Perhaps a little generator will need to be purchased :)

Thanks again cDy
 

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I’m interested in this too as planning some audio upgrades which would be fused at 80amp from the battery (to match the cables and amp fusing) but will only draw 20amp max when in use.


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Thanks for all the detail and the speedy response!

I'd be wiring the oscilator straight to the terminals of the battery so in theory one could ignore the manufacturer's limits from the CigSocket.
I presume you mean an inverter ? 12v to mains power ???

I'm not sure what the output of the DC-DC converter is rated at for the 12v charge side of things but as it has to run things like the heat pump and rear window demister and all the ECU's etc I suspect its going to be rated fairly high as it can draw upwards of 1kw from the 400v pack.
Yo-there might be able to tell us its rating ?

If you really are drawing 2kw @ 230v from a 12v inverter then thats a best part of 200amps you'll be chewing through on the 12v side :eek:
 

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Co-author of CanZE. Q210 nov 2013
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The output of the DCDC converter in a Q model is about 80 amps ;-) There are three things that I can see that go against your plan.

- there is a lot of measurements going on. Taking power straight from the poles could confuse the "system" and throw some errors like "replace 12 V battery!!" if it sees a lot less electrons going out then going in;

- a flat 12 volt battery in the ZOE (any BEV) is no fun. No way of "pushing it to life". Ignore the next sentence, I didn't write it. You can however bootstrap it to life with starter cables.

- 2 kW I'd say is pushing it like Chris says.

@EV Chris: the heat pump runs on the 400 volt bus.
 

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So should we run connections from the fuses on the positive terminal or fuse board under the dash?

I didn’t think Zoe counted electrons so you could just connect straight to the battery terminals like in an ICE.


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Co-author of CanZE. Q210 nov 2013
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Sure, and I am not saying it WILL throw a tantrum, just that it does measure a lot. However, as the OP is thinking of drawing 200 amps, using a cutting splitter under the dash was not something I would recommend :D
 

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Sure, and I am not saying it WILL throw a tantrum, just that it does measure a lot. However, as the OP is thinking of drawing 200 amps, using a cutting splitter under the dash was not something I would recommend :D
So true!

Is there a way to use the 400v feed instead and connect directly to that?


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Co-author of CanZE. Q210 nov 2013
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Yes. Cut the orange cable from the battery to the BCB/ PEC and solder on some extra wires :D
 

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I think he wanted the "on top of the 12 V battery" one.

The battery is 55 Ah and is a standard starter type battery, as in, not a traction or semi-traction type.
 

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There's a warning in the manual not to jump start other cars and a starter motor is usually around 1kW. It's not something that I would recommend doing.
 

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Not seen the Zoe but If connecting direct to the battery, bear in mind there may be a battery current sensor close to one terminal, so make sure any load is connected before this to avoid it panicking due to seeing excessive current.
Something else to consider is that an EV doesn't have to supply the huge load of a starter motor, so the battery may well not be designed to supply such high currents - e.g. internal connections and/or electrodes may be thinner to save weight. Check the battery manufacturer's data or labelling on the battery.
As others have said, the supply capability of the DC/DC will be a limiting factor for running with the car "on" and I'd be surprised if it didn't complain.. The noise from a load like lawnmower may also make the car's systems rather unhappy.
 

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Co-author of CanZE. Q210 nov 2013
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As I mentioned, the 12 volt battery is a totally standard run of the mill starter battery. I have speculated often that it has everything to do with price and availability and nothing with not needing the ICE starter motor profile.
 
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