so i can use a microwave but not brew coffee?

[caretaker]

melita funnel no.2 propane stove.

 

[SternWake]

6 gauge to a 1000 watt inverter powering a 600 watt load is undersized, even if the run was very short.

Keep in mind that while one usually simply divides wattage by 12 to come up with amperage draw on a battery, one is really drawing 15 to 20% more than this due to inverter inefficiency, and the voltage under higher loads is likely in the low 11's, which means significantly more amperage is being drawn than the divide by 12.0 math would indicate. Add in the voltage drop from undersized wiring............lower voltage means higher amps which means more voltage drop. Vicious circle that can be mitigated to some degree with shorter fatter copper.



If using 6v GC-2 batteries, well they do not hold high voltages under larger loads. Their strength is repeated deep cycling ability. Those thicker denser plates of a GC2, are not designed for lots of instant high amp grunt like a high CCA starting battery.

Those wanting to power high loads from little battery capacity should go 12v AGM from Odyssey or Northstar. My Northstar, especially when new, was mind boggling in its ability to hold high voltages under high loads, like staying well above 12 volts under my 1.4 KW starter motor load.

AGM batteries have lower resistance and can support higher voltages for longer. I've never been a fan of Optima batteries as the spiral cell design knocks off ~25% of their total capacity compared to a rectangular battery, but they are pretty low resistance and can retain higher voltage when supporting high loads when still 50% or more charged. This high voltage retainment under load also translates into being able to accept higher amperages when depleted before absorption voltage is attained, at which point amps begine to taper.

A single pair of 6v GC-2 batteries are great for deep cycling under relatively light loads, but when large loads are needed to be powered, one needs them to be more than 85% charged, or needs 4 of them.

Inverters should always have short thick wiring from battery to inverter and thus be mounted nearby the batteries, but not in same compartemnt or above them.
USe AC extension cords to power distant appliances as voltage drop at 120vAC is not much of a factor, but at 11vDC certainly is.

 

[wagoneer]

Yah been married long enough to know how to pick my battles

The goal here John was to use what we have to reduce overhead. If we have enough stored electricity then i would rather use it than propane which we have to buy and haul.

Coffee is something we enjoy and don't plan to give up. Some "wants" are just like that. We continue to try to find ways to streamline our setup while maintaining quality and enjoyment. When the gas fridge craps out, i will be going to electric and adding two more batteries. Not only because it's cost effective, but also because that power storage can supply many different things.

I could be happy with doing what Adrian does and use a rocket stove to brew fresh ground and roasted coffee in a eapresso pot, but i'm not alone in this journey. I've been at this long enough to know which areas there are compromise and which there aren't, if you get my drift.

Thanks for your input[TEACUP WITHOUT HANDLE]

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[Sabatical]

@SternWake
All that makes perfect sense. I've got the perfect storm for inability to power the load. It also sounds like i lucked my way into a really good setup when i built the work vam several years ago. In that scenario i used 2/0 from the under hood isolator to the batteries, which were married and then wired to the inverter with the same size. All connections were hyd pressed lugs. The inverter, initially was a 5kw aims, but i shorted it when i changed the van battery and touched a wrench to the wrong spot. I tried replacing it with the same style but Aims had cheapened them by then and it wouldn't handle the start up loads. I ended up with a 3800w industrial grade from Aims that had a nine second surge capacity. That thing was amazing. Alas, i sold the whole wiring/inverter setup to a good buddy fellow traveller for $200.

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[John61CT]

The inverter, initially was a 5kw aims, but i shorted it when i changed the van battery and touched a wrench to the wrong spot.

Why a good 300+A rated battery disconnect switch, just outside the fuse off main bank positive, is a good idea. $25-30, Blue Sea, Perko and BEP/Marinco make good ones.

e.g. http://www.ebay.com/itm/253007488182

 

[akrvbob]

Stay on topic.

This is an electrical thread, not a coffee thread, too many more coffee posts and they all get deleted.

He didn't write asking for propane advice, he asked for electrical advice on a specific problem. Let's answer his question please by staying on topic.

 

[akrvbob]

I do have 4 batteries and I do recommend that to run a microwave. Have you put a Kill-a-Watt on it? That eliminates guess work.

It sounds like your system should run it, my first thought is it wants at least a 1000 watt pure sine inverter.

 

[Gary68]

beyond what stern said about cleaning up your connections have you investigated other coffee makers to see if there is an more energy efficient model out there?

 

[Sabatical]

I do have 4 batteries and I do recommend that to run a microwave. Have you put a Kill-a-Watt on it? That eliminates guess work.

It sounds like your system should run it, my first thought is it wants at least a 1000 watt pure sine inverter.

I don't have a kill-a-watt but i did put an amp probe on a short section of a/c cord that is split for that purpose. It was reading 5.6 amps until the brewing finished and then it dropped to zero. By my math that is 672 watts at max draw. Well under the 1000 watt inverters threshold. Somebody (not on here) tried to tell me that it had to do with it being a resistive load. Electrical theory is a bit of a mystery to me, which is why i posted here. I knew that i'd likely get some good info.

I would likely follow the advice given to increase wire size.

We discovered today that i hadn't done as good a job as i had thought with battery maintenance and now i'm trying to correct those issues. The biggest lesson for me is to set reminders to do the maintenance.

These batteries are three years old and our first set. Some have said the first set is the practice set. I imagine when i run them into the ground, i will replace them with agm's. Hopefully with a bit of work, i'll be able to get the specific gravity back up where it should be, replace some wiring, and then try the experiment again.

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[akrvbob]

I think it wants a Pure Sine Wave inverter. Is there anyone around with one you could try it on.

 

[WalkaboutTed]

We've been using a 320 watt rice maker to boil our water for coffee, early in the morning, before the solar kicks in. It barely affects the voltage in our system. It's pretty fast, though I haven't timed it. I don't want to use open fire in the van unless we have no choice as I'm a klutz and have a great fear of fire (I have 3 fire extinguishers in our 20 foot van). Even at 8000ft, the cooker is more than adequate. We have the 3x100ah of el cheapo Chinese UPG AGM battery with 2 gauge wire and an 1100 watt modified sine wave inverter.

I've been looking at an 800 watt induction burner for use when the sun is a'crankin (445 watts solar, 545 if we're using the portable panels).
Ted

 

[Sabatical]

The pure sine is a good idea and i probably should've gone that way when i put it together. Ah, hindsight.

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[Weight]

My Mr Coffee 4 cup is a resistive unit only. No timer, no smart stuff, just a thermal switch that opens when water is finished. I have a PSW but can't see any reason why the pot will not run with a MSW of at least the quality of Bestek. That Bestek tests at over 85%, but at 13 volts at terminals. You may need more battery. When running coffee pot, test the 12v dc voltage at the terminals. 3 feet 6AWG charts at less than 2% voltage drop at 70-75 amps. That assumes you have quality cables, not the ones that were packed with the unit.

 

[jonyjoe303]

600 watts is nothing for a new battery to handle. But even new batteries will drop in voltage when you put a large load on them, but 3 year old batteries well definitely not perform that well. 

When the voltage drops, the inverter will well want more amps from the battery, which in turn will reduce the voltage even lower and trip the device to turn off. 

There's a video I watched on youtube "lithium battery test versus gel" that shows what happens when you connect a large load to a 100 ah lead acid, 220 ah lead acid and 100 ah lithium. What it shows is voltage drop even on the 220 ah lead acid which I wasn't expecting. I was expecting the 220 ah lead acid to be comparable to the lithium, but voltage drop was a problem for it.

In your case, 3 feet (voltage drop) is a long distance for the inverter, if you can get it closer it might help.

 

[Sabatical]

Thanks jonyjoe. I'll look for the video.

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[user 37446]

Are you operating your vehicle on a "fast idle" while you are brewing?  That might help you (as long as you have done the thickly wired and fused continuous duty solenoid to batteries).
Also, there's a YT video on using a microwave on a MSW vs a PSW, the PSW was about 15% more efficient. The microwave still worked on MSW though. A coffeemaker shouldn't care.

 

[John61CT]

Some may care more than others, electronics may be involved.

 

[Sabatical]

The system is in a small travel trailer. No vehicle attached.

I'll try again tomorrow now that i have our batteries back in fighting shape. These Trojan t105 are so stinkin resilient. The sun is supposed to shine so we'll see what happens.


Thanks to all who've taken the time to leave input!

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[Sabatical]

Off topic...i discovered today that an old dorm fridge that we have in storage only requires 1.25 amps @ 120ac. It has a samsung compressor unit. I don't know if they are any good but samsung typically makes good quality stuff. The duty cycle is stated to be 20% @ 70 degree ambient temp and 35% @ 90 degree ambient temp. That's like 100 amp hours a day for a cheapo dorm fridge. Can't wait to try this...with more battery bank of course.

Sorry Bob, couldn't resist sharing.

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[highdesertranger]

100ah a day is a huge number. highdesertranger