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Old 08-10-2020, 05:53 PM   #1
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235 amp Hour enough ?

I am looking to add a 3000 wat power inverter as well as 2 6v batteries totaling 235 amp-hours. Now I realize that means only 50% roughly usable or 167 amp hours. with the batteries and will install 200 watts of solar panels as well as a 40 amp mppt controller. for the occasional weekend boon docker does this seem doable . will be for my cpap, tv for the wife with the dvd player, charge cell phones, wife's curling iron and 2 cups a coffee with the Keurig Thanks for anyone's experience
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Old 08-10-2020, 06:28 PM   #2
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50% of 235ah Is Roughly a 117ah's. I'm guessing you're amp hours should be OK. I have a similar set up However I run a 340 W solar panel and 50 amp MPPT controller. Depending on where you mount your panels or place them will determine whether it's enough power to recharge your batteries each day. Also if you plan on building this system and running your Keurig coffee Maker. I would go with 0/0 wire from your battery to your inverter And make the run as short as possible. When I Run of my Keurig coffee maker according to my MT50 read out the batteries are on the verge of being unhappy. As that is a lot of power at leaving the battery at 1 time. With my set up I can boondock indefinitely... As long as I have water. I only carry a generator if I want air conditioning. Everything else works off of my inverter and solar.
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Old 08-10-2020, 06:50 PM   #3
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Thanks for catching my error in the usable hours. Maybe I will have to revert back to the percolator on the propane stove and put it in a thermos. I just like the simplicity of the Keurig since I'm the only coffee drinker in the house.
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Old 08-10-2020, 07:12 PM   #4
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For estimating use 10A of 12VDC current draw for each 1A 120VAC draw.
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Old 08-10-2020, 07:22 PM   #5
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Thanks for catching my error in the usable hours. Maybe I will have to revert back to the percolator on the propane stove and put it in a thermos. I just like the simplicity of the Keurig since I'm the only coffee drinker in the house.
No need to give up your keurig Just understand how much energy you are using Versus how much you're able to replace on an average day With 200 W of solar. I built my system bigger knowing there would be days during our trips that I would put 16 cups of coffee through my keurig. I camp with a lot of Coffee Drinkers sometimes, It's not all for me. Lol
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Old 08-10-2020, 07:27 PM   #6
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Im wondering if I should just go with 400 watts solar and next time around I will go with 4 6volt batteries for more amp hours. Trying to watch my initial costs
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Old 08-10-2020, 08:15 PM   #7
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Thanks for catching my error in the usable hours. Maybe I will have to revert back to the percolator on the propane stove and put it in a thermos. I just like the simplicity of the Keurig since I'm the only coffee drinker in the house.
Stay with the Keurig pods and get a Presto MyJoe coffee maker.

Heat the water on the stove for one cup. Pour into reservoir, attach reservoir to base that has Keuring pod installed. Place top on reservoir and press. Hold until hot water has been pushed through K-pod. Coffee's ready.
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Old 08-10-2020, 09:23 PM   #8
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Im wondering if I should just go with 400 watts solar and next time around I will go with 4 6volt batteries for more amp hours. Trying to watch my initial costs
Also for the record, My system has 2 6v batteries, a 3000 W inverter, 50amp.MPPT, 340w panel and I watch everything with a 50MT monitor. More battery power is not needed in my case I just needed to be able to replenish Most of my amp hours each day. Typically we use between 40 to 80AH A day.
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Old 08-11-2020, 12:27 PM   #9
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Battery/Solar

If you run your furnace it will exceed your available battery/solar. The fan tends to be a power eater.
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Old 08-11-2020, 12:38 PM   #10
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Just so you know, if you use an inverter and draw very large current, the amount of capacity yu are drawing is lower because of Peukerts constant. For example, if you pulled 100A and Peukert's constant of 1.25, your 235AH battery capacity is really only 74AH.


Out of curiosity, why 3000W? 2000W is plenty for an inverter running a coffee maker or a microwave.


Your biggest problem is hitting the 11.5V cutout voltage with only 2 6v golf cart batteries. Use VERY large cables.



Peukert Number Battery Life Calculator
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Old 08-11-2020, 12:41 PM   #11
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If you run your furnace it will exceed your available battery/solar. The fan tends to be a power eater.

It can if it's a large furnace. My furnace only draws ~3 amps and only runs intermittently. If the overnight temp is set lower and an extra blanket is used (even a sleeping bag and a real low temp) furnaces don't always have to drain batteries.

Yes, it is the largest single draw (other than an inverter of course) but only when actually running.

FWIW, I camp in cold weather and set my night temp for 60 degrees. I sleep nice and comfy with an opened sleeping bag over my bed.
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Old 08-11-2020, 12:54 PM   #12
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My heater fan draws 5A. If I have it running overnight set to 60 and it runs 50% of the time over 8 hours, that is 20AH.
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Old 08-11-2020, 01:20 PM   #13
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Battery/Solar

On my 27.5' trailer my furnace fan pulls 6.5 amps. On my Kill-A-Watt meter pulls 30 amps over night (8 hrs) w/ temp set @ 60 on a 45 degree night. I have found the Kill-A-Watt meter to be a cheap-$20 tool that can give start up draw or accumulative usage over a period of time. Not perfect, but good start for establishing needs for solar/battery set-up.
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Old 08-11-2020, 03:35 PM   #14
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From Keurig Support:
Keurig® home brewers use the most power during their initial startup. When heating for the first time after being off, peak usage is 1,500 watts. If the power is kept on, the brewer will keep the internal tank up to temperature using between 200 – 400 watts when heating.
1500 watts is 12.5 AC amps OR 125 DC amps which is FAR too much to get out of a 12V (combined 6v) battery which is capable of a MAX of less than half that current surge...and of course there are other constant loads and at least 10% inefficiency in the inversion process.
Furthermore...Solar 200W will average giving you just 50 amp hours a day of recharging...so far less than the 115 or so you will use daily.
My suggestion would be to buy a gas generator for use when you are brewing coffee or using curling irons and for making up the recharging of your battery at the same time.

I would definitely keep the Keurig unplugged until you need to brew and remember the CURRENT draw I mentioned is a limitation on maximum current you can take in any moment from your battery bank. If you draw 60 amps of current for 5 minutes you only use 1/2 of those 60 in AMPHOUR reserves.
125 amps drawn by a Keurig in 5 minute brew cycle would be about 10 amp hours of battery reserve drawn down...but you cant DRAW that kind of AMPS current from your existing battery bank.
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Old 08-11-2020, 03:59 PM   #15
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Originally Posted by MedicJim View Post
Thanks for catching my error in the usable hours. Maybe I will have to revert back to the percolator on the propane stove and put it in a thermos. I just like the simplicity of the Keurig since I'm the only coffee drinker in the house.
Echoing TitanMike's post, i too am the only coffee drinker and love my Keurig. BUT there's no need to do all this, to power a coffeemaker.
As Mike said, the MyJo works quite simply. Been using mine for years.

https://www.amazon.com/dp/B00HIXSAXQ..._vxWmFbP722YE7
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Old 08-11-2020, 04:05 PM   #16
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Originally Posted by Tundra 2014 View Post
On my 27.5' trailer my furnace fan pulls 6.5 amps. On my Kill-A-Watt meter pulls 30 amps over night (8 hrs) w/ temp set @ 60 on a 45 degree night. I have found the Kill-A-Watt meter to be a cheap-$20 tool that can give start up draw or accumulative usage over a period of time. Not perfect, but good start for establishing needs for solar/battery set-up.
How are you measuring current with a Kill-A-Watt meter on 12VDC?
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Old 08-11-2020, 04:08 PM   #17
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You had me at 3000 watt inverter.
At max power, that inverter will draw roughly 250 amps.
Your battery bank can deliver USABLE 117 AH.
You get to run that inverter, fully loaded, for all of about 25 minutes before your batteries need charging.
250 amps requires 2.0 or 3.0 cable...depending on the length of wire...like welding cable. This is a bad idea.

Learn the sad facts of life here: https://www.rapidtables.com/calc/ele...alculator.html
Always use 12 volts for power consumed from the batteries...even 120 volt loads thru the inverter. The ultimate power source is a 12 volt battery bank.

Under good conditions, each 100 watt solar panel will deliver about 5 amps of charge per hour for about 3 hours a day. 2 panels will deliver about 30 AH during peak sun, then perhaps another 30 AH throughout the rest of the day. So you are running a 50% deficit with just two. 4 x 100 watt panels can just about keep up with charging 2 x 6 volt golf cart batteries under good sun conditions.

If you need 120 volt power, get a generator. You may use it a couple times a day to deliver 120 volt power to coffee makers, and such. While running, the genny will deliver about 30 amps of charge to a depleted battery in the morning. Run it for 20 minutes in the morning and you add about 10 AH. In the evening, after the solar has done its job, the charge rate from the genny will be much less...but still another 5 AH or so.
Believe it or not, Harbor Freight's Predator generator is highly regarded by Consumer Reports, and it's inexpensive: https://www.harborfreight.com/2000-W...gaAhRnEALw_wcB

Install a smaller inverter for your CPAP overnight. My stepson uses one drawing from my 500 watt inverter, and the battery bank has PLENTY of power since the solar recharges next day.

My recipe:
1) 400 watts of solar
2) 2 x 6 volt golf cart batteries (Duracells from Batteries Plus)
3) 500 watt inverter for CPAP or to use an electric blanket to take the chill off the bed for about 20 minutes (360 watt blanket for 1/3 hour = 10 AH)
4) 2000 watt inverter generator for 120 volt loads like the microwave, coffee makers, and so on...and for emergency/rain-day charging. In crappy weather, we fire up the generator, play cards, and everything is hunky dory. Nobody around us cares, because they are inside, too...even tenters.

If you undersize the solar and plan on big 120 volt draws such as a coffee maker and curling iron, and if you run the stereo, lights, furnace and so on, you'll wreck your batteries. The solar should match the battery bank...or exceed. And if you're going to boondock, you NEED a generator or you NEED to give up on your 120 volt loads. And solar doesn't do much when it's raining like hell.
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Old 08-11-2020, 04:15 PM   #18
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You had me at 3000 watt inverter.
At max power, that inverter will draw roughly 250 amps.
Your battery bank can deliver USABLE 117 AH.
Actually even less than that cause of Peukerts constant. Around 7 minutes at 250A would bring you down to 50% SOC. Of course the battery internal voltage drop would be below 1.5V almost immediately and the inverter will shut down.


This is where an AGM battery would work way better and especially a lithium. I actually would never run a large inverter on only 2 6V flooded golf cart batteries.
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Old 08-11-2020, 04:19 PM   #19
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wife's curling iron and 2 cups a coffee with the Keurig Thanks for anyone's experience

Leave these 2 devices home and you will be OK based on my experience of camping in North Carolina latitude during summer with no shade or rain.


Or 300w if its fall. Or 400w if its winter.
that is based on having panels mounted flat on roof and not pointed at sun.
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Old 08-11-2020, 05:01 PM   #20
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I am looking to add a 3000 wat power inverter as well as 2 6v batteries totaling 235 amp-hours. Now I realize that means only 50% roughly usable or 167 amp hours. with the batteries and will install 200 watts of solar panels as well as a 40 amp mppt controller. for the occasional weekend boon docker does this seem doable . will be for my cpap, tv for the wife with the dvd player, charge cell phones, wife's curling iron and 2 cups a coffee with the Keurig Thanks for anyone's experience
I ran a 2000 watt pure sine wave inverter with that battery Bank and 200 watts of solar. What I found is I couldn't keep it on all the time because the ambient load of an inverter that large is 1 to 2 amps continuous.

Also check your math 50% of a 235 amp battery bank is 117 amps. With two golf cart batteries you double the voltage but you do not double the amperage.

I think a 3000 watt inverter is too much temptation to kill your batteries. that said, we installed a 3000 watt pure sine wave inverter in a motorhome this week. He had 6 225 AMP golf cart batteries and by the time coffee was done the first overcast morning the text was my batteries are only 11.9 what should I do? The answer of course+-- stop using things with heating elements in them because those things eat your batteries rapidly.

Short answer+- yes it's doable. Real answer is you'll be sadly disappointed because you'll find yourself running your batteries dead every morning unless you develope a lot of self discipline. I went to direct current televisions . And a really nice stove top percolator. Stovetop cooking doesn't hurt the batteries. Coffee makers, blow dryers and to a lesser degree curling irons kill batteries.
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