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pianotuna

Regina, SK, Canada

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Posted: 04/27/20 12:47pm Link  |  Quote  |  Print  |  Notify Moderator

Plug in what you want to run and put a kill-a-watt meter in series with the shore power cord. Measure the total consumption for 3 days. Double that number and add 10% for inverter inefficiency to calculate battery capacity.


Regards, Don
My ride is 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.

vermilye

Oswego, NY, USA

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Posted: 04/27/20 01:45pm Link  |  Quote  |  Print  |  Notify Moderator

Just a quick note - be sure to use a pure sine wave inverter. Most electric blanket controls will not work on a MSW inverter.


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theoldwizard1

SE MI

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Posted: 04/27/20 02:38pm Link  |  Quote  |  Print  |  Notify Moderator

DrewE wrote:

... so I'd say a minimum of 500 Ah if you aren't talking about lithium batteries. Six GC2 golf cart batteries would be one reasonable setup (with a bit of margin).

I concur ! (Very reasonable "back of the envelope calculation" with cushion !) Skip the electric blanket and you can by with 4 (electric heating pads work better).

S Davis wrote:

Ok so the batteries will be Lifeline AGMs probably the GPL-31XT, I was thinking of starting with two.

That is about 250 Ah. 24 hours, probably less.

Six flooded (non-AGM) golf cart batteries will give you 600-650 Ah and will save you over $300 and give your 48 hours. Four AGM golf cart batteries will be in the same price range as your two GPL-31XT but will give you 400-450 Ah.

theoldwizard1

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Posted: 04/27/20 02:40pm Link  |  Quote  |  Print  |  Notify Moderator

vermilye wrote:

Just a quick note - be sure to use a pure sine wave inverter. Most electric blanket controls will not work on a MSW inverter.

Residential refrigerators like PSW better also !

theoldwizard1

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Posted: 04/27/20 02:46pm Link  |  Quote  |  Print  |  Notify Moderator

wa8yxm wrote:

That's three pair of GC-2 ...

Flood GC2 are about $100 each.

AGM-GC2 (Trojan T105-AGM) are about $250 each

Lifeline are about $475 each

wa8yxm

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Posted: 04/27/20 04:34pm Link  |  Quote  |  Print  |  Notify Moderator

The 10x estimate for converting AC amps to DC is yes a "Back of the enevelope" but I've found it to be amazingly close so long as you do not go over 100 Amps DC with it (And we are only doing 13 here) also the fridge is designed for a 50% duty cycle. How hot it is around it will adjust this so when I gave my estimate I did a divide by two

But since DEEP CYCLE batteries need to be kept at least half full.. I doubled back after adding in the hot pad.. (By the way if you can get by without it it may help)

I've done a lot of relative current measurements between Inverter in and out.

Also you can greatly reduce battery need with something like a Honda or Yahama inverter Generator.. A pair of GC2 can be charged by a progressive Dynmics converter say a 9245 or 9260 The Honda EU100i should be able to handle those the Yahama EF1200i will HOWEVER you are running full bore when the converter is doing likewise.. A 2000 or 2400 would be much quieter and run the larger 60 amp converter.. Use the generator during the day shut down long about sundown or 7pm you should be good and not garner complaints.


Home is where I park it.
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S Davis

Western WA

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Posted: 04/27/20 07:19pm Link  |  Quote  |  Print  |  Notify Moderator

Ok so I am thinking going for 250Ah to start and see if I can get 24 hours between charges, I plan on adding two more batteries at a later date. The electric blanket is 200 watts on high so I know I will not use that much wattage. Probably use med setting so maybe 100 watts, the fridge I don’t have yet but it is energy star rated so I am hoping for a 30% cycle rate. I do have a Honda 2200 to charge with, I need to get good charger.

pianotuna

Regina, SK, Canada

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Posted: 04/27/20 10:15pm Link  |  Quote  |  Print  |  Notify Moderator

S Davis,

Be aware that Lead acid chemistries work best if all jars are the same age.

Note the Peukert effect which results in much longer life span if loads are spread over a larger number of amp-hours. For example a 250 amp-hour battery bank with a 10 amp load would be at 50% state of charge in about 13 hours. Whereas a 500 amp-hour bank with the same 10 amp load would hit 50% in about 29.9 hours. At 750 amp-hours 50% comes after 48 hours.

The good charger you speak of may be best with a top of the line converter, or else an inverter/charger.

My own choice was an inverter/charger with temperature compensated charging. I do have a modest solar charging system as well.

A 200 watt load @ 120 volts represents 20 amps @ 12 volts.

My first battery bank was 875 amp-hours.

MEXICOWANDERER

las peñas, michoacan, mexico

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Posted: 04/28/20 01:30am Link  |  Quote  |  Print  |  Notify Moderator

S Davis wrote:

Ok so the batteries will be Lifeline AGMs probably the GPL-31XT, I was thinking of starting with two. The fridge is energy star rated so maybe figure a 50% cycle rate? Sounds like I better figure for 24 hours between charges.



You will pull the 31 Xt too low. You have other hotel loads. Three 31 Xts would be closer to base reality. The beauty of a Lifeline is that a single 31 will accept an enormous amount of amperage. A 100 amp charger would be a good fit. Set to 14.4 volts. Estimating battery and charger sizes is an artform and is almost impossible to do without amp hour METER kWh data gathered over a month's time. Pencil estimation at it's best averages minus thirty percent or greater.

Even with my 3300 amp hour 24 volt array I ended up with 700 amperes of recharge running two diesel engines to conserve engine run time. To stumble badly during calculations is a humbling experience

RJsfishin

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Posted: 04/28/20 08:32am Link  |  Quote  |  Print  |  Notify Moderator

A couple 8 D's ought to do it [emoticon]


Rich

'01 31' Rexall Vision, Generac 5.5k, 1000 watt Honda, PD 9245 conv, 300 watts Solar, 150 watt inv, 2 Cos 6v batts, ammeters, led voltmeters all over the place, KD/sat, 2 Oly Cat heaters w/ ox, and towing a 2012 Liberty, Lowe bass boat, or a Kawi Mule.


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