Help a confused guy put a power bank together (on a shoestring budget)?

[Clawhammer]

I've been thinking about cobbling together some sort of a power bank, possibly solar powered or possibly not, to take camping and to take to music festival (assuming those ever happen again). All I really want to do with it is run some lights at night, charge cell phones and laptops, and maybe run a fan or a radio.

Currently I'm thinking about just picking up a cheaper deep-cycle battery (like from a golf cart or a trolling motor), and housing it in a tool box with a Harbor Freight inverter like this one: Cheap Inverter Depending on how fast it would drain, I could just charge it up at home off an outlet, take it camping, then bring it home to recharge. If I could snag one cheap enough, I'd think about picking up a solar panel to keep the battery topped up. My longest trips are usually a week to two weeks, so I'm not sure it would be necessary though.

I guess that brings me to my questions. There's just sooooooo much info online that it gets overwhelming and the next thing you know, you've tallied up several hundred if not thousands of dollars worth of stuff you "need." Since I don't plan on running a fridge or anything major, and only plan to use this a few weeks here and there, I want to have as little invested in a power bank as possible (but still have it be, at least somewhat, reliable).

So basically, if you were setting out with the needs I've listed above in mind, what would you buy? How big of battery and how big of an inverter? Would it be worth investing in a solar panel too, or is my home charging plan enough juice? Harbor Freight also has a cheap solar regulator I was looking at it. Obviously, the panel would have to be sized right for the battery which is whole 'nother ball of confusion... Anyway, if any of you could steer me in the right direction, I'd sure appreciate it!

 

[Martinjmpr]

IMO if you're going to be outside in nice weather, solar is a no-brainer. You can get a decent 100W solar panel kit for under $200 that will put ~ 5ah into your battery for 8 - 10 hours a day.

That's free power from the sky. It's like the old saying "it's raining soup, grab a bucket."

As far as the inverter goes, I would try and see if you absolutely need it. On a laptop computer, for instance, the power supply that you plug into the wall is usually an AC/DC converter: IOW, what is going to the laptop is actually DC power (I think mine is 19v.)

So when you run an inverter, what are you doing? You're taking DC power from a battery, converting it to AC (and you will lose energy doing this) and then you are taking that AC power and - converting it back to DC (again causing a loss of energy)? Seems pretty wasteful and inefficient.

If possible, I'd try to avoid the use of any AC appliance that you can. Find a DC charger for your laptop and get a 12v DC fan and 12v DC lights (yes they make them, for cars and RVs.) If you can eliminate the need for an inverter all you need is a big battery and a way to charge it (and the solar panel should be more than adequate for that.)

If you can source DC components for what you need, then a battery + battery box + solar panel altogether shouldn't run you more than $350 and will be super-simple to set up.

As far as golf cart batteries go, yes they pack a lot of power but they are crazy heavy! We have 2 x 6v GC batteries on our travel trailer but I would estimate the weight around 160 lbs! Fortunately for us this sits on the tongue of the trailer so we don't have to move it around. My little 12v trolling-motor power box uses a 90AH FLA battery from Costco and weighs ~ 70lbs. It's heavy but manageable.

A simple setup like that would probably work fine for you, no need to overcomplicate it.

 

[Martinjmpr]

As far as charging goes, carry a set of jumper cables in your vehicle (which really you should have anyway ) If you're out for a long period of time and your battery starts to get discharged (maybe it's been cloudy or rainy so the solar isn't helping) connect the jumper cables from your vehicle to the battery pack and run your engine for an hour or so. That should put enough juice back into the battery to keep it running for a few more days. Easier and less expensive than setting up a charging system with a dual battery or a DC-DC charger (which is what I have.)

 

[Buddha.]

Is this something that’s going to stay in a vehicle? What vehicle?

 

[rruff]

-All I really want to do with it is run some lights at night, charge cell phones and laptops, and maybe run a fan or a radio.
-My longest trips are usually a week to two weeks, so I'm not sure it would be necessary though.
-I want to have as little invested in a power bank as possible (but still have it be, at least somewhat, reliable).
-So basically, if you were setting out with the needs I've listed above in mind, what would you buy? How big of battery and how big of an inverter?

1st step: You need a realistic estimate of your power/energy needs. Add up the power draw of all the devices, and how much time they will be on. No way to size the system til you get that. If you use LED lights, the laptops will be the biggest draw. It can vary a lot. An efficient laptop just doing word processing or similar may only use 10-15W while a high powered gaming laptop playing games would draw >200W.

 

[Clawhammer]

IMO if you're going to be outside in nice weather, solar is a no-brainer. You can get a decent 100W solar panel kit for under $200 that will put ~ 5ah into your battery for 8 - 10 hours a day.

That's free power from the sky. It's like the old saying "it's raining soup, grab a bucket."

As far as the inverter goes, I would try and see if you absolutely need it. On a laptop computer, for instance, the power supply that you plug into the wall is usually an AC/DC converter: IOW, what is going to the laptop is actually DC power (I think mine is 19v.)

So when you run an inverter, what are you doing? You're taking DC power from a battery, converting it to AC (and you will lose energy doing this) and then you are taking that AC power and - converting it back to DC (again causing a loss of energy)? Seems pretty wasteful and inefficient.

If possible, I'd try to avoid the use of any AC appliance that you can. Find a DC charger for your laptop and get a 12v DC fan and 12v DC lights (yes they make them, for cars and RVs.) If you can eliminate the need for an inverter all you need is a big battery and a way to charge it (and the solar panel should be more than adequate for that.)

If you can source DC components for what you need, then a battery + battery box + solar panel altogether shouldn't run you more than $350 and will be super-simple to set up.

As far as golf cart batteries go, yes they pack a lot of power but they are crazy heavy! We have 2 x 6v GC batteries on our travel trailer but I would estimate the weight around 160 lbs! Fortunately for us this sits on the tongue of the trailer so we don't have to move it around. My little 12v trolling-motor power box uses a 90AH FLA battery from Costco and weighs ~ 70lbs. It's heavy but manageable.

A simple setup like that would probably work fine for you, no need to overcomplicate it.

DC lights/chargers were something I hadn't considered, so that's definitely worth looking into. I would probably still like to have an inverter around "just in case" should there be something I'd want to power that's AC. Why not have the option handy. I hadn't realized golf cart batteries were that heavy, so yeah, probably won't go that route. 70lbs is doable though. Obviously, lighter would be better, but whatever works.

I was looking at your power bank build thread and was thinking of doing something similar, just simpler. The main reason for not going solar out of the gate is just cost. If a charged battery would last enough time, why spend the extra money. I could always charge it off the engine like you said too. I could always add one on down the line if I needed it too. I'm not opposed to attaching a panel, but do like the idea of just have a box to carry around and nothing else.

Is this something that’s going to stay in a vehicle? What vehicle?

Probably will mostly stay in my Tacoma (second gen, access cab), but I want it to be small and mobile enough that I could take it to, say an EZ up, or a ground tent up and run things there from it. Depending on how big of a group I'm camping with, I'll sometimes set up a social area with a canopy or whatever, and then park the truck further off since I sleep in it and like some privacy/peace and quiet. That's why I'm looking into power packs and not dual battery setups or anything like that.

1st step: You need a realistic estimate of your power/energy needs. Add up the power draw of all the devices, and how much time they will be on. No way to size the system til you get that. If you use LED lights, the laptops will be the biggest draw. It can vary a lot. An efficient laptop just doing word processing or similar may only use 10-15W while a high powered gaming laptop playing games would draw >200W.

I was planning on using LED lights for sure. The laptop I'd be using is a MacBook Pro which I think peaks around 100W. Probably wouldn't be using the computer any more than a couple hours every couple of days. Phone would be charged more often, probably once or even twice a day, as would my partner's phone. Lights might end up being on 4 to... 8, even 10 hours? (I'm a musician and when camping with other musical buddies, it's not unusual for us to stay up stupidly late. I've seen the sun come up a few times on a great jam session). 4 to 6 hours is probably a safer guess though. So, yeah, not sure what all that adds up to. That's actually one of reasons I'm asking you all. I'm just not knowledgeable enough to make an accurate estimate.

You guys are really helping me put a plan together here, so thanks!

 

[jonyjoe101]

A simple cheap powerbank is the mobius, each is 26ah and lightweight. I'm using one to power my laptop right now. 4 of these will be less then 30 pounds and provide you 100ah of total power. You can charge them at home take them with you and just plug in a new one as they get depleted, since they are lithium you don't have to charge them back up right away. Unlike lead acid, you can use all 26ah of the battery.

I use my laptop 3 to 4 hours a day with a 200 watt ac inverter, the mobius can power it for 4 to 5 days. The mobius will easily power all the devices you mentioned. I tested them with devices that use up to 12 amps, they got power to spare.

The mobius just needs a 4 pin connector (you can find on amazon) and then add your own plug (12 volt cigarette adapter, xt60 or whatever you use).
You will need a 12.6 volt cc/cv charger to charge these up. I charge them at up to 6 amps.

You can find the mobius on ebay for different prices, I bought 4 of them for 130 dollars.


Picture of 4x mobius connected in parallel

 

[Clawhammer]

Is there a good reason not to go with something like this: https://www.amazon.com/Jackery-Port...coding=UTF8&psc=1&refRID=SGF0C2XBN7JV94R8KA38
and a solar panel? Seems even easier than plug and play and seems like it would work for what I need...

 

[jonyjoe101]

the jackery on the link is only 15ah, they got jackerys in the 50ah range which would power your laptop for over a week. Its good to research all your options. By the description of the jackery it looks like the max charge rate is 3 amps. The 60 watt solar panel is another 180 dollars.

 

[Clawhammer]

the jackery on the link is only 15ah, they got jackerys in the 50ah range which would power your laptop for over a week. Its good to research all your options. By the description of the jackery it looks like the max charge rate is 3 amps. The 60 watt solar panel is another 180 dollars.

Hmm... gets pretty pricey pretty fast. Maybe a simple solution, but not a cost-effective one.

 

[rruff]

A simple cheap powerbank is the mobius, each is 26ah and lightweight. I'm using one to power my laptop right now.

Says they are 10.95V. No problem using them with any 12V devices and inverters? How does the charging work exactly?

A much more efficient way to run the laptop is to plug into DC directly. May not work, but usually does.

 

[Choff]

Nice setup advice

DIY Van Electrical Guide: Build Your Knowledge | FarOutRide

Complete guide on designing and installing your own DIY electrical system in a camper van conversion. Free wiring diagram and tutorial inside!

faroutride.com

 

[jonyjoe101]

Says they are 10.95V. No problem using them with any 12V devices and inverters? How does the charging work exactly?

These powerpacks are 3s packs, same as a goalzero. Full charge 12.6 volts, and 0 percent is about 10 volts(when the bms cutsoff). This will have no problem running most inverters/lights/fans etc. The only 12 volt device that I encountered that won't run at the lower voltage is a fridge

To run a fridge you will need a boost/buck converter to raise the voltage to 13.4 volts. I build my own boost/buck converter, its a boost converter to raise the voltage to 18 volts then connected directly to a buck converter that drops the voltage to 13.4 volts and 6 amps output. This will run the fridge even when the voltage drops into the low 10's. A boost or buck by itself won't work at input/output voltages so close to each other.

Make sure and add your own connector (xt60/cigarette plug/etc) to the 4 pin connector (yellow wires/plus and black/negative) and just charge with a 12.6 volt cc/cv charger. You can also use a laptop charger 18 volts and connect it to a buck converter set to 12.6 volts and charge at whatever amps you need (I use 6 amps). The mobius has a built-in bms to prevent overcharging.

If the bms activates you need to connect to a 12 volt power source to kickstart the bms to restart. If you recieve a mobius that has "0" power left (no light on display when pressed) and it won't kickstart, it means the battery level is too low, you need to open up the unit and charge directly back up to at least 10 volts, I had to solder a plus/negative wire to the battery and then charge it to 10 volts. After that it work fine. I bought 12 mobius, only 2 had "0" on the display.

You can run a laptop with a boost converter but you need the special plug for your laptop. I use the AC inverter since I can get 4 to 5 days of use with it.

There are videos on youtube that go more indepth in how to use these mobius powerpacks.

Boost buck converter internals



running a fridge with boost/buck converter, this keeps the voltage very stable only drops .2 volts from 13.4 volts while in use. The fridge compressor doesnt like low voltage or too much voltage drop.

 

[Martinjmpr]

Is there a good reason not to go with something like this: https://www.amazon.com/Jackery-Port...coding=UTF8&psc=1&refRID=SGF0C2XBN7JV94R8KA38
and a solar panel? Seems even easier than plug and play and seems like it would work for what I need...

As others have said, that's a lot of $$ to pay to get 15 AH of battery.

By way of comparison, you can get a "jump pack" at Harbor Freight for about $60 that has a 17AH battery.

Harbor Freight Tools – Quality Tools at Discount Prices Since 1977

Harbor Freight buys their top quality tools from the same factories that supply our competitors. We cut out the middleman and pass the savings to you!

www.harborfreight.com

I also got this a few years ago from Amazon:

Amazon.com: BEATIT G18 2000Amp Peak 12V Portable Jump Starter (Up to 8.0L Gas and Diesel Engine) 21000mAh Power Bank With Wireless Charger Smart Jumper Cables: Automotive

Buy BEATIT G18 2000Amp Peak 12V Portable Jump Starter (Up to 8.0L Gas and Diesel Engine) 21000mAh Power Bank With Wireless Charger Smart Jumper Cables: Jump Starters - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

Advertised as 21,000 mAH so 21 AH in theory. Not sure if I believe that but it does seem to be enough to jump start an engine and it can be recharged through a USB port.

 

[jonyjoe101]

The 3 in 1 jumpstarter has a 17ah agm on it you can only use 50 percent, so it drops usable ah to 8.5ah. The only agm's that you can use 100 percent of the ah are the oddesseys 16ah agm, but those cost 120 dollars and are in the 20 pound range. Very good batteries.

The beatit g18 uses a 3s 7ah lipo, they multiply the 3sx7mah to get 21000mah. But officially it maxes out at 7ah if you use it to power 12 volt devices. 7ah is what is found on an average laptop.