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Open Roads Forum  >  Tech Issues

 > How long will this battery inverter run

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time2roll

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Posted: 10/12/17 10:45am Link  |  Quote  |  Print  |  Notify Moderator

Bring the Honda or 3 additional batteries.


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pianotuna

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Posted: 10/12/17 12:36pm Link  |  Quote  |  Print  |  Notify Moderator

700 watts =~ 70 amps

170 watts =~ 17 amps

A 59 amp hour battery has about 29 amp-hours usable.

A peukert calculation suggests that at 70 amps the battery would be dead in about 33 minutes and 14 minutes to 50%.

At 17 amps that goes up to about 2 hours and about 51 minutes to 50%.

That said, the Peukert adjusted load for a 59 amp hour battery at 17 amps jumps up to about 29 amps. No battery is going to like that much load.

I would suggest at least a 100 amp-hour battery for the 17 amp load, and 400 amp-hours for the 70 amp load.


Regards, Don
Full Time in a 28 foot Class C, 256 watts solar, 556 amp hours of AGM in two battery banks 12 volt batteries, 3000 watt Magnum hybrid inverter, Sola Basic Autoformer, Microair Easy Start.

MrWizard

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Posted: 10/12/17 05:14pm Link  |  Quote  |  Print  |  Notify Moderator

the short version of all this
your battery can't make it for a 6hr duration
and all you will be is frustrated with a dead battery
after a few times trying this you will need a new battery


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pianotuna

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Posted: 10/12/17 05:37pm Link  |  Quote  |  Print  |  Notify Moderator

Well said, Mr. Wizard.

BFL13

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Posted: 10/12/17 06:47pm Link  |  Quote  |  Print  |  Notify Moderator

I don't know how we can guess about the voltage drop with 17 amps on the 59 AH battery without knowing the gauge and length of the wires between inverter and battery.

17 out of 59 is like 126 amps draw on a 440 AH bank. That can be near a 1 volt drop even with decent wiring inverter-battery (It can be less of a drop than that with really good wiring gauge and length of course)

If the OP is using the issue wires that came with his 700w inverter, I can imagine the voltage drop will be huge at 17 amps from the 59AH batt. I was thinking he could even get a low voltage shut off at the start and not be able to run things at all. But I don't know.


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time2roll

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Posted: 10/12/17 06:57pm Link  |  Quote  |  Print  |  Notify Moderator

Guess? 15 amps x 6 hours = 75 amp hours. So you need 150 amp hours minimum. So 3 batteries should be enough. I throw in one more for good measure and unknown conditions.

Or bring the Honda.

BFL13

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Posted: 10/12/17 07:09pm Link  |  Quote  |  Print  |  Notify Moderator

time2roll wrote:

Guess? 15 amps x 6 hours = 75 amp hours. So you need 150 amp hours minimum. So 3 batteries should be enough. I throw in one more for good measure and unknown conditions.

Or bring the Honda.


Yes, but people seem to be assuming the battery will run down to 50% before the inverter shuts down, when I am wondering if the inverter will shut down right off because the inverter-battery wiring is not good enough. Or it might shut down real soon after it does run for a short time.

I am questioning how people can be assuming that without knowing the actual wiring.

marcsbigfoot20b27

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Posted: 10/12/17 07:45pm Link  |  Quote  |  Print  |  Notify Moderator

Then we have more bad news......its more than likely a modified sine wave inverter which makes it even more inefficient.
The fan motor will start getting hot, hopefully the tv power supply will be ok.

I dont see any 700 watt unit, there is a 750 Schumacher .

pianotuna

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Posted: 10/12/17 07:52pm Link  |  Quote  |  Print  |  Notify Moderator

Hi marcsbigfoot,

I owned a 700 watt motormaster inverter.

time2roll

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Posted: 10/12/17 07:53pm Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:

time2roll wrote:

Guess? 15 amps x 6 hours = 75 amp hours. So you need 150 amp hours minimum. So 3 batteries should be enough. I throw in one more for good measure and unknown conditions.

Or bring the Honda.


Yes, but people seem to be assuming the battery will run down to 50% before the inverter shuts down, when I am wondering if the inverter will shut down right off because the inverter-battery wiring is not good enough. Or it might shut down real soon after it does run for a short time.

I am questioning how people can be assuming that without knowing the actual wiring.
I try to assume OP can follow the install instructions. Or he can ask.
Part of the reason I throw in one more for unknown conditions.

Also good chance the batteries show up only 85 percent charged.

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