BajaNomad

Portable Power Station?

bajaric - 3-27-2019 at 08:40 AM

Question for the solar power / off grid folks:

I would like to buy (or build) a portable power station that contains a rechargeable battery. It would need to store enough power to run high demand items in short bursts (Power tools, jump starter, vacuum cleaner) and also run low demand items (lights, TV) for longer periods. It could be recharged with a wall outlet or a solar panel. I guess first question is what kind of battery. Lead acid or Lithium? For lead acid what kind? Golf cart batteries, regular car battery, deep cycle? What wall charger is best, trickle charger or deep cycle. Cost is a big factor, weight not so much. Are lithium batteries any good for this kind of system? I have searched and not found much that is within a reasonable price range, Home Depot sells a Dewalt Power station for $250 but it has no solar recharge and also lousy reviews.

I guess the simplest way would be to get a car battery with a wall trickle charger and a solar panel/controller and connect a 1000(?) watt inverter to it but you are looking at several hundred dollars right there just wondering if there is something like this you can buy off the shelf without costing an arm and a leg.

John Harper - 3-27-2019 at 09:40 AM

I think power tools and vacuum cleaners need quite a few amps to operate. Not an expert, but you should probably calculate your potential load, add a decent amount of cushion, and calculate backward from there. I've got a lithium battery on my Sportster for the last five years, never used a tender, and it holds power for months, if not years. Lithium batteries are also ridiculously light compared to lead acid, but charging may require a specialized controller.

John

Russ - 3-27-2019 at 11:46 AM

bajaric, My thought is for you to ask the folks in your area and find the best in your size and price range. Unfortunately there is nothing portable about a home solar system. good luck in your search and making a choice with what will work for you. There are a lot of systems out now and none are inexpensive.

bajagregg - 3-27-2019 at 02:23 PM

You will need plenty of watts to get power tools like a small compressor or even a Skillsaw going. I have a 1500 w inverter that works fine for a drill motor or grinder but won't run anything with a high starting load like a compressor or circular saw. A 3000 w unit might do that job.

Like John said, Lithium Ion batteries excel in every way except for one thing - cost. They run about 2 to 3 times the cost of a comparable lead acid battery. A single 12v deep cycle or, for more run time, two 6v golf cart batteries wired in series could be the way to go.

daveB - 3-27-2019 at 05:50 PM

My motorhome has solar panels that, together, are rated as producing 235 watts. The power is stored in 4 - 6 volt golf cart batteries wired to give 12 volts. A charge controller sends the power to the batteries through a Xantrex 2,000 watt Inverter/Charger. There are 2 inside panel mounted items, one controls the Inverter use, the other gives readings as to how much solar power is coming in, given in Amps, and then will switch to what voltage the batteries have (this is not a true reading, as that will be possible only after rest - so check what it is the next morning.) I have ten outlets, 9 inside and one outside the motorhome. We have used this system on extended trips where we often camp for months at a time, away from electricity. We have an inside vacume cleaner, a microwave, and watch satellite TV. Our refrigerator uses a small amount of 12 volt power to run its circuit board, and the propane forced air furnace also uses some for that purpose if we use it. We carry a drip coffee maker, but use it only when plugged in to "shore power," using propane to run a perculator coffee maker, when inside, on the propane stove or outside, with a portable propane tank in warm weather situations. For seven winters we camped on a Mainland Pacific Mexico coral beach with this motohome. There was no electricity to that beach. We cannot run an air conditioner with this set up unless we get to shore power.

PabloT - 3-29-2019 at 12:00 AM

https://www.solarpaneltalk.com/

I am not an expert by any means, but this forum is 1 of the best I have come across. I have been studying on rolling my own power station for a while. I don't know how far down the rabbit hole you want to go, but there is a lot of good info here. There are some good stickies here with the basics. The moderators are active and have convinced me they know what they are talking about.

larryC - 3-29-2019 at 07:25 AM

For what you want to do I think I would look into a small Honda generator like the EU 1000 or even the EU 2000, less hassle than batteries. If you do go the battery and inverter route then stick with deep cycle AGM batteries and a good charge controller. If you don't over charge the batteries they won't ever need water and will last longer that an automotive battery. Either way you go it is going to cost you more than a couple hundred bucks.
I don't understand your statement " It could be recharged with a wall outlet or a solar panel." If you have a wall outlet and electricity then why are you putting together a semi solar system?

Whale-ista - 3-29-2019 at 08:01 AM

Have you checked out GoalZero products? Www.goalzero.com

Costco sells their largest “house power” model- the 1400 KWH Yeti. I have a smaller version about the size of a car battery for emergencies and camping trips. 400 kwh.

Both are designed for plug-in solar charging. They also sell the solar panels.

But as others noted: not sufficient for big energy draws like power tools.



[Edited on 3-29-2019 by Whale-ista]

daveB - 3-29-2019 at 09:44 AM

Solar panels have really come down in price. By looking after the storage batteries by not running them down past 50%, you can get six or eight years from a good quality six volt system running them as 12 volts with an inverter/charger. If you want a portable power source, though, and can't used a solar array, then yes, a gas generator could meet your needs better. A simple way to use power tools when shore power is too far away. The Honda 2000 line is one of the quieter ones, and can recharge a battery bank for you, as well.

Alm - 3-29-2019 at 01:41 PM

Quote: Originally posted by bajaric  

I guess the simplest way would be to get a car battery with a wall trickle charger and a solar panel/controller and connect a 1000(?) watt inverter to it but you are looking at several hundred dollars right there just wondering if there is something like this you can buy off the shelf without costing an arm and a leg.


Don't know why portability is important for what looks like shore home use (or semi-permanent RV) .

So, foregoing the portability...
I would get a deep cycle battery, not car battery. 200-300 AH total bank @12V.

Li batteries deteriorate with time, whether you use it or not. 2*6V golf cart batteries will likely beat Li in $ per cycle life, given occasional use. But, if you must have Li, you need 150-200 AH bank (they have ~1.5 times more usable energy per nominal capacity). Li batteries don't like being charged and discharged in Baja summer temps. Baja winter is no problem.

I would use grid power to run 12V DC power supply unit that would in turn power solar controller (when there is no sun). $100 solar controller with $60 DC supply will result in better and more adjustable charging algorithm than off the shelf car chargers in this price range.

You would need 300-500W solar array. Small panels cost ~$1/watt, big panels over 180W - about $0.40 per watt but they need more expensive MPPT type controller. 2*300W panels with 40A controller will cost under $500.

Inverter is a separate story. I would get 600-1000W if microwave is not planned. With microwave you need at least 2,000W and very desirably - battery bank more than 2 golf-cart units. But 2 GC would work.

PaulW - 3-30-2019 at 07:58 AM

Search for the latest Lithium/iron batteries for vehicle use. For your application you need a very large and expensive one. Whether on not your application would be applicable for any battery would be questionable. If you do a proper load analysis you would find out. The lithium mentioned would surely handle the amps, but the real question is how long.
Then for these new technology lithium batteries a special charger designed for the battery.
One thing for sure a small generator will be much less expensive.
Good luck on your search.
=======
Quote: Originally posted by bajaric  
Question for the solar power / off grid folks:

I would like to buy (or build) a portable power station that contains a rechargeable battery. It would need to store enough power to run high demand items in short bursts (Power tools, jump starter, vacuum cleaner) and also run low demand items (lights, TV) for longer periods. It could be recharged with a wall outlet or a solar panel. I guess first question is what kind of battery. Lead acid or Lithium? For lead acid what kind? Golf cart batteries, regular car battery, deep cycle? What wall charger is best, trickle charger or deep cycle. Cost is a big factor, weight not so much. Are lithium batteries any good for this kind of system? I have searched and not found much that is within a reasonable price range, Home Depot sells a Dewalt Power station for $250 but it has no solar recharge and also lousy reviews.

I guess the simplest way would be to get a car battery with a wall trickle charger and a solar panel/controller and connect a 1000(?) watt inverter to it but you are looking at several hundred dollars right there just wondering if there is something like this you can buy off the shelf without costing an arm and a leg.

bajaric - 3-30-2019 at 10:52 AM

Thank you all for your input. My basic goal is something portable enough to be placed in a vehicle. The battery will be charged at home from a wall outlet, then used in the field to run small electronics. The solar charger will be used to extend the battery life when away from a wall outlet. I have been doing some research and tried a couple things out. Talk about a learning curve, amp hours, ohms law, pure sine waves, etc.
I ended up just connecting an 800 watt inverter to a 12 volt truck battery and it works fine. I did learn a lot, though.

A couple of general observations: First, many batteries need a long time on a charger to fully charge them. Many issues can be solved just by leaving the battery on the charger for 6-8 hours. Also, if you are messing around with 12 volt batteries get a device that has a reverse polarity alarm. I have jump started dozens of vehicles, I guess it was inevitable that one day I hooked up the cables backwards and fried a rather expensive Truck Pac jump starter that did not have a reverse polarity alarm. Fuses, automatic shutoffs, etc. are your friend, especially if you are like me and just touch wires together to see if they spark rather than actually doing mind numbing mathematical calculations.

Also, it is apparent to me now that a generator and a couple gallons of gasoline will provide a lot more power for a lot longer than any battery, lithium or otherwise, at least in my price range. Guess I won't be selling my shares in COP any time soon lol. However, I do not much like generators. I do not like the noise and fumes and do not want to subject others to it so am trying to go the electric route.

Anyhow so I tried connecting a 800 watt Cobra CPI890 inverter to a Interstate lithium battery jump starter to supply power to the inverter. Turns out the jump starter puts out 16 volts and the Cobra shuts off at 15 volts. The Interstate does have two DC outlets that are supposed to supply 12 and 16 volts (through a very small diameter wire) but they BOTH put out 16 volts. Factory defect. I might return it, justifiably, or maybe just keep it for a jump starter. Anyhow, using a lithium jump starter to power an 800 watt inverter did not work out so well.

The next thing I did was hook up a 12 volt truck battery to the Cobra. Just a plain old Wal Mart cheapo battery that was in my old truck. This was newer battery that had been fried by the aforementioned jump start mishap and the battery was almost dead then I charged it up with a wall-outlet Schauer 10 deep cycle charger (for 8 hours) and it charged up fine and holds a charge. And, it worked great! The 12 volt battery and the Cobra inverter will run a 32 inch flat screen TV, or a small shop vac, or a large power drill. All I need. However, I would like to be able to recharge the battery in the field and that is where the solar battery charger comes in and I am trying to decide what will work.

Any good or bad experiences to share re: solar battery chargers?


[Edited on 3-30-2019 by bajaric]

AKgringo - 3-30-2019 at 11:32 AM

I know very little about solar, ohm's law, or the other concerns you discussed, but have some experience with 12v batteries. I think a deep cycle RV, or even a marine battery would hold up to your intended use longer than a standard truck battery. That is, assuming that the battery was capable of providing the amperage you require.

Alm - 3-30-2019 at 12:27 PM

Bajaric - you've already come a long way using trials and errors approach.

Read up on 3-stage charging. The last stage from 80 to 100% is the slowest, takes several hours. Generator will bring the battery quickly from to 80%, and then will be wasting fuel and making your neighbors miserable by running for several hours to pump the last 20% in. Charger voltage should be lowered a bit on this stage.

This is the problem with generators, they either leave battery undercharged or you have to run it all day long. Batteries like being charged fully once a day (not Li batteries, those are different and actually last longer when they are not charged over 80%).

Solar panels are perfect for this last slow stage. It silently provides low current for the rest of the day. In Baja small cabins or RV often use solar for all 3 stages, keeping generator for emergencies only. Check Renogy 100W solar suitcase: https://www.amazon.com/HQST-Polycrystalline-Portable-Foldabl...

This suitcase is an easy way in for people not familiar with solar and electricity. For a shore home or a big RV this would be a poor choice, a big solar array on the roof is more cost-efficient.

You might get away with a 100AH deep cycle or "Marine" battery (the latter one is "sort of" a deep cycle, you can get them for cheap in Walmart). I prefer re-chargeable power tools, charging them in daytime so that solar panel would take some of the load off the battery. I have 400W solar array on the roof, small by today's standards, and yet, on most days my batteries are full before noon and I can use the "leftover" energy from the sun to charge power tools or laptop.

100AH led acid battery still weighs 70 lbs, better mount it permanently in the truck.

[Edited on 3-30-2019 by Alm]

Alm - 3-30-2019 at 09:10 PM

... Also:
have just noticed this: "The 12 volt battery and the Cobra inverter will run a 32 inch flat screen TV, or a small shop vac, or a large power drill."

Did you try running vacuum on a single 12 battery? Small shop vac could be 60A @12V, including inverter losses.

Several people here warned on dangers of high currents in small battery. Single 100AH led acid battery won't like 60A current. It will drop from 100% to 50-60% in 15 minutes, due to certain non-linear effects in battery chemistry. 60A will also shorten the battery life. Get a small cordless vacuum.

About drills and other tools - better get a cordless too. Local contractors run generators for large power tools, though still use small cordless tools - more convenient.

[Edited on 3-31-2019 by Alm]