Charging and inverters

Capt_Kirk

I charge at 14.8 volts temperature compensated that goes over 15 volts
Who makes a good inverter that does not shut off at 15 volts? I can not find one. I have to wait till sun set to make dinner in the microwave 
if i sleep late the coffee maker wont run. 

BB.

What Wattage of Inverter are you looking for?

-Bill

Capt_Kirk

If I got a 1500-1750 then I can make coffee and the wife could use the blow dryer
But just enough to make coffee and charge a laptop on long trips

mryimmers

Exeltech XP inverters are 16.5 volts shut off on a 12volt system, and very good inverters, our host sells them, or watch on ebay. (the XP1100 is fairly common)
I had this same issue using a SureSine 300, in the winter, if the batteries were below about -13C the inverter would shut down as max input voltage is only 15.5V.
Did some research and got an Exeltech on ebay (2 actually), and switched to 24V just because I can't leave well enough alone, haha.

BB.

Besides Exeltech (and you can order "custom" voltage specifications too from our host NAWS):

http://www.solar-electric.com/exeltech-xp2000-12-volt-2000-watt-sine-wave-inverter.html (note, website typo--this is a 2,000 watt, not 1,100 Watt inverter--I think)

Samulex has the SA series that will run to 16 volts (Cotex is a co-mfg inverter with Samlex--Same/similar models/different markings/sales channel?):

http://www.solar-electric.com/samlex-sa-1500-112-sine-wave-inverter.html

And PST series will run to 16.5 volts:

http://www.solar-electric.com/samlex-pure-sine-wave-inverter-pst-2000-12.html
http://www.solar-electric.com/samlex-pure-sine-wave-inverter-pst-1000-12.html

Outback will run to 17.0 volts:

http://www.solar-electric.com/outback-power-vfxr2812a-hybrid-inverter.html

Xantrex to 16 volts:

http://www.xantrex.com/power-products/power-inverters/prosine.aspx

Magnum runs to 17 volts:

http://www.solar-electric.com/maenms2020wa.html

Now back to system design... I would suggest that the maximum inverter size for a 12 volt system should be around 1,200 Watts maximum. However, some folks have been very happy with the Xantrex Pro 1,800 Watt inverter...

With 12 volt / 2 kWatt inverters, you are talking about huge amounts of current:

• 2,000 Watts * 1/0.85 inverter eff * 1/10.5 volts battery cut off = 224 Amps continuous (surge to 448 amps) @ 12 volts

And for a flooded cell lead acid battery, a 2 kWatt 12 volt battery bank should be at a minimum of 800 Amp*Hours (to support continuous load/surge load ratings).

Note that a 10% rate of charge for an 800 AH battery bank is 80 Amps--Just about the maximum for a typical "full size" solar charge controller. For an RV (weekend/seasonal use, you may get away with 5% rate of charge).

Note that a 24 volt system will cut DC battery bus (and charging current) by 1/2 -- You still would want a minimum of 400 AH @ 24 volt battery bank (basically the same "weight" of batteries--Just re-arranged to higher battery bus voltage).

As increase your voltage, you can reduce the number of parallel strings (and/or reduce the AH per battery rating). For example, an 800 AH @ 12 volt battery bank would require 2x 6 volt @ 200 AH "golf cart" batteries in series x 4 parallel strings (8 batteries total).

A 400 AH @ 24 volt battery bank would require 4x 6 volt @ 200 AH batteries * 2 parallel strings (8 batteries total).

Of course, lead acid batteries are heavy/expensive... If your "high power loads" are relatively short usage--AGM batteries will give higher discharge current (use a smaller battery bank for high power discharge). And, LiFePO4 batteries are getting close to being popular in RV's these days--Much lighter, much higher surge/charging current, no issues with sulfation (can store partially charged). AGMs and LiFePO4 batteries are more expensive and have different "issues" (monitoring state of charge, cell balance, etc.)... But they can be a solution if you have needs that map well to their strong points.

Or--Just fire up the genset when running the hair drier for 20 minutes. And keep the battery/solar/inverter/etc. on the smaller size to run the 'quite time loads".

-Bill

Capt_Kirk

Bill, 
Thank you for the information.  
The cost of the big inverters and battery bank needed to run them and that we are weekend boon dockers will keep us on 12v and the occasional generator use. 

Thanks to everyone who chimed in.  This information is much appreciated. 
11 years till retirement might be enough planning....