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converting 12v dc into 12v ac

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gonadgranny

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Hi all.
Ive just bought a pcb heatbed, the kind used for 3d printers. i want to try and power it with a few lithium batteries. to do this i need to convert the dc from the batteries in to ac. you can purchase power inverters but they step the voltage up to 220. this heatbed only requires 12v.id imagine that its probably quite energy inefficient to step up to 220 then transform it down to 12. so my question is: is it possible to convert 12v dc into 12v ac?
thanks very much for any possible reply's,
Dan
 

Resistive heaters can be powered with DC as well as AC. There's no need to convert 12V DC to AC.
 
oh really? well that certainly simplifies things! thanks!
 

well it works! but the thing is, the negative battery terminal gets ridiculously hot. ive just used electrical tape to connect them for the time being and it melts through. any ideas why this might be happening and even better, a possible solution?
 

If you stay using that battery then there's no way to solve that problem, because if you want x watts from a 12v battery, then your battery has to ship x/12 amps....and that current , as you say, is heating it up to that extent...no solution, other than get a different battery...unless you find a way to get rid of the heat from the terminal...be careful because lithiums catch fire
 

Maybe you could make a few banks of 12v and put them in parallel, use parallel wires to connect them to the load - that way the current and heat will be shared. It may be cheaper or easier to find a good 12v power tool battery and charger - use appropriate gauge wire to connect it. Get two and just keep swapping them out as you charge them.
 

thanks c1500. i actually did try putting the batteries in parallel because i thought that as you say, if the current is shared then the heat will be distributed too. the batteries being 3.7v meant that i had to use a boost converter to get the voltage i required.. i used a voltmeter to test the output and got it to 12v. but the thing is, as soon as i switched on the heatmat the voltage dropped to about 3.8v. any idea why this might be? im thinking of maybe connecting it to an arduino via a mosfet and pwm the power output to50% or something if i cant find another solution.
 

you boosted to 12v and then it just became the input voltage at the output...sounds like the boost got disabled, or its inductor saturated, or the diode went short circuit
 

Your best bet is to put 3-4 lithium batteries in SERIES and run directly the load without the booster. Next step is to get an idea of the current and voltage the load takes. If the -ve terminal gets hot but the +ve terminal stays cool, then it is very likely a 'loose' connection...
 

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