Dustbuster voltage change

Hi,

It is exam season, so to avoid work, I am experimenting with a dustbuster. I want to change a 7.2v to a 9.6v (the 7.2 batteries dont work) - I have been using a model car NiCad pack and the suction is fantastic and the motor still remains cool. The only problem is the battery pack get very hot! How can I prevent this? Ideas I had:

1) a resistor to limit current flow - loath to do this as it will reduce motor speed 2) 2 9.6 packs in parellel to share the load between them and so keep them cooler. 3) A different type of battery - NiMH/Lead acid

I know that buying anew one is easier, but it is the experimenting that I want to do! :)

Thanks squelch41

The batteries get hot because you're drawing a lot of power from them, what you need is higher capacity (A-Hr) cells or put multiple battery packs in parallel.

Not a good idea to parallel Ni-Cads - etc. They tend to self discharge even quicker. Use larger capacity cells in series.

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Well I have a Makita vac that's 7.2V and have been running it on 9.6V going on 7 years now. It rocks. The end of the pack is identical and the salesman that sold it to me showed me the battery switch. The only thing that has happened is that the impeller needed replacement last year. That cost about $7. The Makita batteries have built in thermal protection. Richard

I put 2 sets in parellel but it ended up drawing 10A as opposed to the

5A it was drawing from the single pack. The original batts are sub-c cells - presumably their additional amp-hour rating would enable them to run cool enough? Also, I suppose as it was a 7.2V, less current was drawn?

Yes as you increase the voltage the motor will draw more current as well, and in return you get a dramatic increase in horsepower.

So what sort of battery would be most suitable to cope with this? I would imagine lead acid?

Actually, having just looked, lead acid batteries seem to be in multiples of 6v which isnt really suitable.

Would NiMH batteries be more suitable as they can provide more mAhs but I'd imagine they'd get just as hot especially as they have a higher internal resistance dont they?

Thanks

Yes, usually these things use NiCd's, I would think NiMH would be fine with intermittant use though.

Are they likely to suffer from the same level of heat generation?

... and a dramatic increase in smoke output (but only temporarily).

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