multiple inverters

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rigpigpaul

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Hi all. I have just been to Costco and they are selling 300 watt inverters for £26-00 inc.vat. Would I be able to connect four of these in parallel to give me a very cheap 1200 watt unit. I know I would have to use heavy cable from the battery.

Thanks in anticipation
Paul
ps King size memory foam mattresses 70mm £140-00
 
4 x £26 = £104 which will buy you a good secondhand inverter!
I found a 1.5kw item for a hundred quid in the For Sale lists.
 
I have had real problems with square wave inverters - blew up one ac adaptor and maybe contributed to the demise of another. I have spoken to other liveaboards who have had similar experiences. I bought a 600W sine wave inverter from RS Components which has been fine but as Tome said, you mustn't parallel the outputs of these things, it isn't like dc.
 
If you want lots of watts you really nead to spend lots of money! I've just installed a 2Kw Victron sinewave inverter which CAN be paralled together with 4 others. It also synchronises itself with the AC shorepower to give you extra power - so if your marina is limited to 6 amps at 230 volts it will give you another 8 amps or more. All this AC power needs a large battery bank so I've gone for 1000Ah with a DC generator that charges at 290 amps. It's been a huge re-engineering of the boat - but I've saved over £2000 just on labour charges by installing it all myself.
 
I've gone for 12 volts to interface easily with all existing systems. It means drawing twice the current from each battery, but with large (2/0AWG) cables I'm only loosing 0.1 volts on the cable run when drawing 150 amps (30 amps per battery)
 
I think there is a good case for doing it this way as long as you don't run the inverter at high loads for more than the occasional 5 or 10 mins but start the generator to ensure that the dc required by the inverter is being provided from the generator, not chemically-stored energy from the batteries.

I presume that your normal procedure will be to run the generator whenever you want to draw serious power from the inverter? Otherwise, at 2kW, you are discharging your batteries at approx the 5 or 6 hour rate and the total capacity will fall by around 50%. Add to this the need not to discharge much below 50% capacity to avoid battery damage and that gives you an effective 250Ah, i.e. around an hour and a half at 2kW (all rounded figures as there is nothing precise about battery supplies!) What sort of batteries have you installed? Flooded lead acid?
 
I've got five 210 Ah LIFELINE AGM batteries - with a 5 year guarantee!!! They charge 30% faster than other batteries and can be mounted upside down if necessary. The generator can be set to come on automatically - and is much much quieter than a conventional AC generator which is always running at the same speed whether you're drawing 4 KW or 100W. The DC genny simply runs at the speed needed to deliver the required charging current.

This a new system that I haven't had a chance to evaluate fully yet - but in the long run the running costs should be cheaper and much quieter than an AC option.
 
I believe you need to oversize inverters.

We have a charger/inverter that produces sine wave at (from memory) 1500W. But it doesn't like the microwave running at full power, rated at only 600W, because that has an electronic power supply and limited efficiency. However, it handles computers, etc. with no problem.

Talking about blowing things up.... I wired the inverter originally so that it still powered the old battery charger.... which being electronic.... required power, to supply the inverter, to power the battery charger. I switched off as things got louder and louder and threatened to blow.
 
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