Solar for Battery Pack

Hi all  :heart:

I need some suggestions for what solar panel I should buy off Amazon for this little guy https://www.northerntool.com/shop/tools/product_200678034_200678034?adv=false

I met a girl who had one just like it in her van at a festival and she used it to charge a small fridge cooler.  I might do the same but also just need to charge it when boondocking because it's pretty useful if my battery dies as it has jumper cables.  I have no clue what solar panel I should get for it though.  Something flexible I can put across the front wind shield when parked would be nice.  I was dumb and didn't write down what solar panel it was the other girl had so now I have to figure it out....

Any solar panel + controller that is designed for charging 12V.

Key question is how many AH per day will you use?

A very efficient 12V compressor fridge can range from 20AH to 40AH depending on temp differentials, insulation etc.

The cheap little "12V coolers" are *****, very inefficient, don't work at all in hot weather.

That unit is a $150 box + gadgets around a $50 battery that only holds 17 usable AH.

Unless you know the included inverter matches some specific appliance you really need, you'll get much better value choosing your own components.

With our help of course, but you do need to learn a bit about the tech details.

How do I tell someone they bought the wrong thing for the job needed.

^^^ very gently and diplomatically.

Also helpful to provide information and links of what would be better suited to their use. Verifying that the product is returnable is helpful too!

I like to use the word 'one' rather than 'you' as well.

I did not get the impression OP has already purchased anything.

If so, can be adapted.

One nice thing about these old-school lead units is easy access to and replacement of the very standard battery included.

"Central hub" thread for a similar topic, powerpaks usually too small for full-fledged House banks, but fine for a small fan for a while and recharging electronic gadgets.

https://vanlivingforum.com/showthread.php?tid=23546

Like John61CT already said; any solar panel + a 12V solar charge controller will be able to charge a box/battery like that.

So any of these solar panels will be able to give it a charge (the big question is however how long will it take), but they will all work towards the goal; to push some energy into the battery:

An Amazon search on 12V foldable solar panels
The higher watt rated the solar panels are, the faster they are likely to accomplish a full charge. 


The box you linked to has a 33Ah (ampere hour) sealed lead acid battery, it is advisabe to only use as much as 50% of that energy, or your battery will age very quickly. 
So in theory you are looking at how to charge as much as 33 / 2 = 16.5Ah


How many amp hours can come from one solar panel? 

A 21W solar panel (@12V) can give a maximum of 21W / 12V =  1.75A
and when that has happened for one hour, it has produced 1.75Ah 
So this would ideally only take a 21W solar panel only 16.5Ah / 1.75Ah = 9.42 hours to fully charge the battery in the battery power pack you linked to at northerntool.com

Ideally, because 9 perfect sun hours rarely comes in 9 consecutive hours. The car window will also cause a reduction in efficiency. And the battery panel is not likely to be at the optimal angle to the sun, to produce at the maximum rate efficiency of 21W. And the manufacturer might have given some theoretical ability for the panel, and the practical reality might easily be lower. 

So the reality of trying to charge a 33Ah battery, with a 21W solar panel might be more like; it will take days to do one full charge. Possibly 3 to 5 days. 


So will a 40-50W or even a 100W (foldable) solar panel be better? Yes it will  

Will the setup/concept of such a box improve if you also charge the battery, while driving your car? Yes it will. 

The type of box you linked to at  northerntool.com,  mainly has the advantage of ease of use and convenience. 
But it will be difficult for us DIY guys to give our highest praises for such combination packages. 


Those combination box systems also rarely have any over dis-charge protection, so it will be easy to draw more than 50% energy from the battery (especially if it is used to power a constant power use type of device, like a fridge), and thus it will age much faster.  In worst case, after only 10 deep discharges (this is however true for any cheap (sealed) lead acid battery) 


So you might also want to look at prices for other 33Ah batteries, that might fit into the box, as it is likely that you will need another battery after a year or so.
Amazon search for 33Ah 12V batteries.


Panel options
40W - 50W - 50W - 100W 
Please note that I do not know these panels, I simply picked them from the amazon list, as they seems nice and possibly usable for the type of use you have described. 



Did this answer (at least in part) your question of which front window solar panel might be useful with the box? 

And did you also hear the warnings about being too quickly be too enchanted by the convenience of those all-in-one boxes?   
But do I think such a combo-box is better that only having your car battery? Yes I do. 


Do I myself have such a combo-box? Yes, and I have both modified and enhanced it - and been let down by it.
So have I now built my own solution using some lithium (LiFePO4) motorcycle batteries? Yes I have, because I happened to stumble across an exchange-deal, so they cost me no money.

It's good to know that to use the box to run anything continuously, such as a mini fridge, would only wear it down. I'm thinking i just need to keep it on me in case i need a jump start, and if i'm boondocking and the thing is dead, it's not much use to me. So in order to keep it charged up will be a nice thought, in case i do need it.

I'll probably go with the higher watt solar panel. I still am not sure which wattage, exactly. Have to think about it

If you have not already purchased it, I would hold off for now.

I looked at the online manual and the DC input charging port calls for a 15 vdc, 800ma supply, and it will take "42 hours or more" to charge at that rate with a deeply discharged battery. I did not see any other input for solar or even 12 v input. And the FAQ says it is "only designed to be recharged with the AC adapter".

You could possibly use a small solar panel, but if it takes that long to charge the unit, you are looking at many days of solar recharging for just a small amount of use. 

If you are a VERY patient person, and you only need it for emergencies and such, then ok...it might do the job for you.

But at 800ma input, it would never be able to keep up with any normal constant load you might apply, other than maybe charging a phone, and you don't need this thing to do that.

Other, and much better, units are out there and more easily charged with solar panels.

tx2sturgis said:

If you have not already purchased it, I would hold off for now.

Click to expand...

I agree

tx2sturgis said:

a 15 vdc, 800ma supply, and it will take "42 hours or more" to charge at that rate with a deeply discharged battery. 

Click to expand...

That's the wall wart that comes with it, obviously useless for mobile use.

But any 10-20A charger will get it full overnight, maybe even 4-6 hours.

Just need a robust connection direct to the batt - not the ciggie port!

This unit

https://mobiledistributorsupply.com...jump-starter-and-power-bank-18000mah-oem.html

is much more convenient as a jumpstarter powerpack.

May not have quite as high AH storage capacity, but can recharge the biggest phone or tablet, even run alaptop a few hours, is very compact, and designed to charge off 12V (solar or car) as well as shore power in a few hours.

Can jumpstart even a large diesel engine, but yes do keep it topped up for that contingency.

But most important it's **small**, fit in a jacket pocket, purse, glovebox.

Just realize none of thos has anything to do with a proper House bank to power fans, fridge etc.

John61CT said:

That's the wall wart that comes with it,  obviously useless for mobile use.

But any 10-20A charger will get it full overnight,  maybe even 4-6 hours.

Just need a robust connection direct to the batt - not the ciggie port!

Click to expand...

I very much doubt we want to advise her to crack open the case on a brand new unit and attach some clamps or wires. The input port is (apparently) limited to 800 mils. I would never advise anyone to test that just for grins to see what happens.

The input port is probably regulated or at least limited on current due to small wiring or circuit traces, or it directly feeds a small on-board smart charger. 

Not practical or prudent to feed that little coaxial input port with 14-18 volts and 10-20 amps just to see what happens.

You know how a old-school radio has an easily opened compartment in the back holding the battery(ies)?

These units are designed so the user can easily swap it out. That's what's great about this old-school style, they're just too big a box for a tiny batt.

And overpriced for what they are, just like the whole product category.

In fact, getting five of the replacement batts and charging that 5p set as one 12V House bank, and then rotating one of them into the box as needed would work just fine.

I'm not suggesting that for this OP, just clarifying how basic these are.

tx2sturgis said:

I looked at the online manual and the DC input charging port calls for a 15 vdc, 800ma supply, and it will take "42 hours or more" to charge at that rate with a deeply discharged battery. I did not see any other input for solar or even 12 v input. And the FAQ says it is "only designed to be recharged with the AC adapter".

Click to expand...

Using the standard way to charge the battery (the DC port at 800mA) is indeed a very slow way to charge it.  And if one were to attach a solar panel to that plug, it would be wise to also limit the input to 800mA

What I did to the (smaller) "12V Portable Power Pack" that I had, was to attach a standard battery charger directly to the jumper cable grips. On my unit those cables were connected directly to the plus and minus of the battery (via that main, high power switch), so it was the same as connecting directly to the poles of the battery. 
I have no doubt, this Strongway Portable Power Pack is designed the same way. 
In the video about this unit, it also shows how the main high power switch is turned 90 degree, before the unit is being used to actually jumpstart a car. 

On my unit, the 12V cigarette plug was also connected directly to the batteries, but via a 15A automatic fuse. So if too much power was drawn (or pushed into the battery) through that 12V plug, the fuse would disconnect, cool down, and reconnect after some seconds (about 10-15 seconds). 

So there may be ways to connect solar (and/or) the cars alternator, to aid in charging the battery, at a reasonable pace.  That is, some way faster than the 20-40 hours. 


On a different note, I would also look into these lithium jumpstarter power-packs. 

John61CT said:

This unit
https://mobiledistributorsupply.com...jump-starter-and-power-bank-18000mah-oem.html
is much more convenient as a jumpstarter powerpack. 

Click to expand...

As they can indeed be used to jumpstart cars and vans. 


The total amount of power that they hold, is however less. And when they say, 18000mAh, it is likely NOT at 12V. 
For the lithium unit in the link (which I consider to be a very interesting candidate), I tried to figure out at what voltage it is likely to have the 18000mAh. 
In the manual it turns out to mention that the battery capacity is 66.6W, and at the nominal voltage of a lithium battery (3.6V) the 66.6W / 3.6V (turns out to be) = 18500mAh

I have however no doubt, that all other lithium power banks, are very likely to calculate their mAh capacity in pretty much the same way. 

So at 12V there is only 66.6W / 12V = 5.5Ah available. 

But even so, I would still consider a battery (Power Bank) like this, as a very viable backup plan, for jump starting a car, and charging cell-phones or laptops etc. 

The reason these lithium power banks can be used to jumpstart a car or van, is because it is possible to design lithium batteries so it is possible to draw out many, many times their Ah capacity, for just those 3-10 seconds it takes to start a car. 
The manual states that it is possible to pull between 300 amp and 600 amp peak, from this particular unit. 

So it can indeed be used to jumpstart a car or van.
In comparison, the Strongway Portable Power Pack, advertises an ability to deliver 1000 Amps for a short time, like the time it takes to start a car or a van. 


And looking at Amazon they have lithium power banks that can be used to jump start at 1000 amps or even 2000 amps or more. 


What I have yet to determine, is the best/fastest way to charge those lithium power banks. As they are typically meant to be charged using a 5V usb plug, or a 14V,1A, charging plug.
Charging them using the 14V plug, will mean that they take about 5 hours to fully recharge after a complete discharge. 
Though this is still much better than the (official) 20-42 hours of the other battery pack.

MrAlvinDude said:

What I did to the (smaller) "12V Portable Power Pack" that I had, was to attach a standard battery charger directly to the jumper cable grips. On my unit those cables were connected directly to the plus and minus of the battery (via that main, high power switch), so it was the same as connecting directly to the poles of the battery. 

Click to expand...

This would probably work, but it depends on the OP's tolerance for that approach.

Most of the time we find that the buyers of these units buy them because they want a plug-n-play solution. 

By default (and having read about similar situations) I tend to assume that they also want simple yes-no, this-or-that answers, and much less of the technical background information. 

But if she has already bought and intends to keep it, then, yes, we can assist the OP as best we can to make it more usable while 'off grid'.

I figured the jumper clamps aren't actually directly attached straight through to the battery, you get different units advertising different very high amperages for jumpstarting, but all based on the same type small AH battery, thought there's electronics in between there.

But on units where they are direct, obviously any robust enough connection, can be used for charging or discharging.

But I don't trust ciggie ports for more than 5 or 6 amps, and then only for short time uses, bothing critical.

MrAlvinDude said:

And when they say, 18000mAh, it is likely NOT at 12V. 
...
What I have yet to determine, is the best/fastest way to charge those lithium power banks. As they are typically meant to be charged using a 5V usb plug, or a 14V,1A, charging plug.
Charging them using the 14V plug, will mean that they take about 5 hours to fully recharge after a complete discharge. 
Though this is still much better than the (official) 20-42 hours of the other battery pack.

Click to expand...

First thing to understand, most vendors in this niche flat out lie.

Never are AH quoted at 12V. If there is any truth to ot, it is either at the internal cell voltage (sometimes 3.7V, but you meed to know what specific LI chemistry, LiPo different from NMC.

Or it's at the lowest voltage port, say 5V for USB.

Or a complete lie.

Only way to try to know is to get a link to the inside replacement battery, and assume that vendor is honest.

Or buy one and actually do a 20-hour rate load test at 12V.

Sometimes you can find a post from a guy who's deconstructed the batt pack and writes

> each string is 5 cells of NMC 18650 type @3.7V to get to 18.5V, this model contains 10, 2 strings at 2000 mAH each so 4AH total

> this season they're using Samsung INR18650-20Q , but last year's were Panasonics

Note this information is **never** available from the manufacturer, and their so-called tech support people have zero clues.

So basically you need to be willing to take the unit apart, risk destroying it in order to do things like find out how to charge it in an hour, which any LI chemistry can do no problem if you have the right volts and amps charger, and a DMM and ammeter to watch over the process.

Sounds like i should go a different route. I'm pretty uncertain about what to do, but for the battery pack, i can just charge it up using shore power to use in an emergency. Then to run my tiny coffee maker, phone charger and lap top, i have a power inverter that plugs into the cigarette outlet...

Solar makes my head spin.

Even the "tiny" coffee maker, anything using electricity for heating is a big load IMO wasteful.

Many super coffee making methods work just fine over a tiny propane flame.

Get a Watts Up meter, build up a list of any loads amps draw, AH per minute/hour, estimate how long you'll use it.

Make an energy budget, AH per day.

With your setup so far, avg 10-20AH / day might be fine with careful use of your vehicle battery on driving days.

Each 100W of panel might cover 20AH supply in good weather. So 2nd panel, consider another battery.