# Using a commercial grinder with a battery?



## ObsidianSage (Jan 30, 2012)

Hi

I wondered if anyone on here has experience of powering a commercial grade grinder (mines a Santos no. 4) using a car battery with an inverter to ramp up the voltage?

Seems theoretically possible, but I wonder can a battery deliver enough grunt to power such a thing and for how long?

Love to hear from who's done it.

Dan


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## Glenn (Jun 14, 2008)

A car battery will not last as long as a leisure battery (the type used in Caravans)

You can run a grinder for a quite a while on a fully charged battery as it is not continuous power

You need to ensure the battery and inverter are well paired and can handle the loads required.

Have a chat to Bella Barista whose Towability division customises carts and hopefully can assist.


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## Dylan (Dec 5, 2011)

Whats the grinder Obsidian? The sums are pretty easy, and the equipment not too expensive, I can probably help you put together what you would need.

Edit: nevermind on what grinder, just saw it in your post.


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## Dylan (Dec 5, 2011)

Ok, so its only 600W so thats no problem.

You need:

A naval battery like This one, Numax are the leading brand, and for £70 you can't go wrong, you can plump for a bit cheaper if you like. The important figure here is the "110ah", the bigger this number, the longer the battery lasts. Oh it does need a CCA (cold cranking amperage) of at least the wattage of your grinder. This particular Numax has a CCA of 1000w, so will work just fine (unless it gets below freezing, which lead acids dont like).

A pure sine wave inverter like this one from maplin, you can get simmilar ones on amazon for a simmilar price, this is rated at 1000w so will have no problem running your grinder.

A charger for car batteries like this one from Halfords 

And your good to go, you will get just under an hour of continuous grinding from one charge on the battery. Be aware that lead acid takes an age to charge, around 10hours with this battery and charger.

I use this basic system as backup battery power for a computer rig when I'm on location.


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## aaronb (Nov 16, 2012)

I'd imagine there are solutions, as mobile coffee carts must be without 240v AC at times?


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## ObsidianSage (Jan 30, 2012)

Wow! Thanks everyone. Especially D_Evans for that very comprehensive answer. I will check it all out.


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## ObsidianSage (Jan 30, 2012)

What is the significance / importance of buying a PURE SINEWAVE inverter as opposed to an impure? one?


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## Dylan (Dec 5, 2011)

Basically a 'modified sine wave' does not output a smooth or 'perfect' electrical current, this will lead to more noise on an old TV set or a humm from some electrical components, or in the case of an AC motor (where you need to worry) up to a 20% drop in efficiency.

Personally I would never run anything but the most basic electrical equipment off a modified sine wave inverter, as I would be worried for the life span of the components within that are tested on the basis of 'normal' (as in pure sine wave) electrical current would not fare well under a modified sine wave. I cant base that off any particular electrical understanding, but its never nice to hear an electrical humm from something, which is common when running from a modified sine wave.


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## ObsidianSage (Jan 30, 2012)

Ah. Got it. Thanks.


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## kateandersonjack (Jan 22, 2014)

Hi, I'm wondering how you got on with this ?

We've been trading with our mobile Piaggio set up for about 9 months now, but having some issues with inverter / grinder.

About to buy our third inverter and want to try and get it right this time, (I suspect our mistake was using too cheap manufacturers perviously, and them not being able to cope with initial power draw of the grinder motor) did you get one that works well?


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## grumpydaddy (Oct 20, 2014)

You need to think about the current that a motor draws on startup when it comes to buying an inverter for a grinder. An on demand grinder in particular will be drawing this momentary but very high current more often than a dosered grinder.

It may be politic to either discuss the figures with the grinder manufacturer in the hope you can present your requirements to the seller of the inverter or run the test yourself (perhaps have it done). If you can lock the rotating parts of the grinder then momentarily turn on the power and with the aid of a heavy duty ammeter get a current reading you can then spec an inverter to suit.

The inrush current can be 8 times the running current in some instances depending on the design of the motor.

I accept that this is just seen by the inverter for some milliseconds at a time but it must be designed to cope nonetheless.

The use of AGM batteries capable of both deep discharge and "starting" currents is recommended. Do not heavily discharge any battery if you want it to last longer.


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