Using 14 x PP3 (9V) Batteries in Series to Test Apparently Dead Vectrix

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martinwinlow
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Using 14 x PP3 (9V) Batteries in Series to Test Apparently Dead Vectrix

Hi All,

The thought occurs… for a very cheap way of testing an otherwise apparently dead Vectrix to check at least the motor controller (MC), motor and instrumentation (i.e. every thing except the charger and battery) works, would it not be feasible to connect 14 x PP3 (9V) batteries in series to the MC (USING A SUITABLE IN-RUSH CURRENT LIMITER, of course) connections?

You'd have to raise the rear wheel off the ground… and maybe disconnect the head light or immediately switch it off using the correct magic sequence otherwise they would go flat too quickly… perhaps. £20 max….!

Archi13
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Re: Using 14 x PP3 (9V) Batteries in Series to Test ...

Hello Martin,
this is a good joke, I thinks that in the USA with a 127V power you can use just for try one of this GBPC2506 - PONT REDRESSEUR 25A 600V and perhaps adjunct two big capacitors for 200V.
http://fr.farnell.com/multicomp/gbpc2506/pont-redresseur-25a-600v/dp/4084713
And don't forget a bulb lampe in serial with jour install,
but be carefull, you play with your life, if you don't know what, it's better to don't try.
Best regards.

spoonman
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Re: Using 14 x PP3 (9V) Batteries in Series to Test ...

ROFL - "inrush current" from PP3's!

You'd be lucky if they have enough in them to finish the precharge cycle let alone do any damage.
PP3's are only about 750mAh, I'd be very surprised if you could run the system from them for any length of time even if you were only out to test the administrative end.

spoonman
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double post

*double post

martinwinlow
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Re: Using 14 x PP3 (9V) Batteries in Series to Test ...

I think you'd be surprised and anyway, 126V x 0.75Ah = 95Wh which is a good mile's worth of riding! I can tell you're not convinced. MW

Regards, Martin Winlow
Isle of Colonsay, Scotland
evalbum.com/2092

Archi13
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Re: Using 14 x PP3 (9V) Batteries in Series to Test ...

I think that the good count is 0,75 AH because for 126 volts you must have your battery in serial and not //

But you can try, I'm not sure that you can only switch on the bike.

Drew
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Re: Using 14 x PP3 (9V) Batteries in Series to Test ...

Martin,

Actually, I think this would work - even though the cells will have a greater internal resistance when loaded, this will have an 'auto-cut out' effect; the voltage will drop if you try and draw too much current from the bank of cells and the system will simply shut down or go into a restart loop. I don't think you could do much damage but would still adopt the ICL method when connecting them to start with as it's good practice.

Have a look at https://www.youtube.com/watch?v=8hwLHdBTQ7s

Ok, in this instance, there are rather more cells than you intend to use but it's still quite remarkable that you can strike a large DC arc from a series of PP3s! I wouldn't want to be holding that insulation with bare hands like this chap did...

If you try it, it would be interesting for you to report your findings here.

Best wishes,

Drew

Drew

spoonman
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Re: Using 14 x PP3 (9V) Batteries in Series to Test ...

lol - not quite convinced no.

As to the arc mentioned above, you don't need any significant current for an arc either - a simple cockroft-walton multiplier will pull tiny voltages up to kV and produce a spectacular arc - but that doesn't mean it'll necessarily go anywhere near powering a circuit.

Drew is correct though in so far as that such a pack may well be sufficient to power the onboard electronics through the DC-DC converter *IF* it survives initial connection to the main power bus - and by 'survives' I mean if it isn't significantly depleted by the current drawn from it during the process - and I would be very surprised if it did I'm afraid.

Regardless, it's definitely highly unlikely to do any damage, so if you fancy trying it then I'd have no reservations in that regard.

PJD
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Re: Using 14 x PP3 (9V) Batteries in Series to Test ...

It might work, but you won't need an inrush protector. I just checked 9V battery with an ammeter. Upon immediately applying a short to the battery, it produced 1.3 amps, tapering down to about 0.6 amps after 20 seconds or so.

martinwinlow
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Re: Using 14 x PP3 (9V) Batteries in Series to Test ...

Hi PJD,

How does 1.3A compare with the currant flow using a 60W 240V filament light bulb as an ICL?

Wouldn't different types of PP3 behave differently? A modern rechargeable one for example? MW

Regards, Martin Winlow
Isle of Colonsay, Scotland
evalbum.com/2092

antiscab
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Re: Using 14 x PP3 (9V) Batteries in Series to Test ...

Hi PJD,

How does 1.3A compare with the currant flow using a 60W 240V filament light bulb as an ICL?

Wouldn't different types of PP3 behave differently? A modern rechargeable one for example? MW

a 60W light bulb wouldn't put much more than 0.5A momentarily, probably much less

the important thing is to keep the current under 50A or so - so with cells that small I wouldn't worry

Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km

spoonman
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Re: Using 14 x PP3 (9V) Batteries in Series to Test ...

Martin, you'll get variation between different grades and qualities of PP3 of course, but those variations are never going to deviate much from the above stated.

The bottom line is that the PP3 *isn't* a 'power' cell in any configuration. It's designed to run low power applications for extended durations of time - that's it.
It simply isn't designed to charge big-ass capacitors.

You could bolster the power available by combining parallels but at that stage the expense is just going to make the whole thing entirely rediculous given that it's NEVER going to drive the power stage of the motor controller anyway. I'd be amazed if that does anything at all with any less than a few hundred Watts, and according to the experiment conducted above, the most you're going to get from a single series of PP3's is ~150W and probably not for very long at that.

Drew
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Re: Using 14 x PP3 (9V) Batteries in Series to Test ...

Spoonman, I agree with your comments on current required to sustain an arc - the only reason I put the link to the youtube video is because it looked very impressive and was a bit of fun! I also thought that the fellow must have been collecting the PP3s for ages and ages - what a hobby!

As for the Vectrix, let's assume that a 60W incandescent lamp running on UK mains (240V) has a steady state on-resistance of about 960 Ohms. (P = V^2/R) I'd expect this to be about 15x lower when cold, as that is the nature of a filament lamp... 68 Ohms (just measured one!).

With 14 x 9V alkaline (new they are ~9.7V ) batteries (so ~135V), if we assume a Vectrix controller has exceptionally low turn on resistance, I now agree that with the alkaline PP3s, you won't need to use and ICL to protect the capacitors and control gear from sudden charging.

If you did choose to put the 68 Ohm lamp in series with the bike (as an ICL) then the initial current would be something akin to;

I = V/R

I = 135/68

I = ~2 Amps

This is greater current than the short-circuited alkaline cells can develop - I think PJD said they can deliver a short circuit current rating (SCCR) of 1.3A so in my opinion, it's safe to connect the PP3s directly.

I would expect rechargeable cells to have a proportionally higher SCCR but still within the limits of what the bike electronics can handle. If you're in any doubt, you can still use an ICL (It costs you nothing to do so!). For all other Vectrix traction battery reconnections, an ICL is definitely required.

If I had that many PP3s, I'd happily give it a go!

Drew

Drew

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