Tool Battery Inverter/Power Bank.

@fidodie Sorry, I have no idea what this is all about, especially this part

whenever I use the 115v, it most likely plugging in a wall bug.

@fidodie Also this part

I have a couple of the NiMH chargers around - so I already have a case for landing the battery and some useful parts inside.  Would need a 12v power plug (aka cigarette lighter), and maybe a couple of lugs?

landing?

lugs?

Does case mean a container or an instance of a particular situation?

Two conversions cost more in power loss than one. Some conversions are more expensive in terms of power loss. This is a somewhat technical and longish discussion if you really want to get into it.

As to the following

Is there any measurable battery savings if I created a 12V + USB version w/o the 115?

I assume you left out the words 'power supply' between version and w/o. In that case it all depends on how you create the 12V and the 5.1V. If you mean a 12V power pack with a 12V to 5.1V buck converter then there is a slight loss in the buck, but it's pretty much the only way we do that. I don't understand the w/o 115, you need to charge the battery from 115VAC before you can use the batteries.

You need to draw some diagrams that are well-labelled. You don't need fancy schematics, just the various pieces.

Is this any more than mains->charger->battery->12v load (and 5.1V USB?)

I assume then that your question is 'what do I need to convert the 12V to 5.1V and provide a USB A female connector?

BTW, I have two of the Makita power tool battery USB adapter for my astrophotography to power the camera, and a dew heater. LINK

@zander - could see that being confusing.

[strike]115v is the line voltage receptacle,[/strike]  ugh oh, it actually says 120V

This is a wall bug!  Well in the local slang.

What i'm look for is, "What would the gain in run time be if I go straight from 18v to 12v, rather than 18->120->12?"  What about others (dell is 19.5 I think)

another pic of the parts

This also could be me making something more complicated than it has to be

@zander  This is good - i'll clean up and draw;

I have all these rechargeable lithium batteries - they are the source in all cases.

I was going to use the old nimh chargers as a case for whatever is built since it can't charge the lithium batteries.  it will provide a solid connection to the battery.

lugs - slang for screw down terminals. 

@fidodie 120/115 I understand, some devices are even labelled 117. I honesty forget the official number but what you measure at the wall is a function of your distance from the power station.

I never heard of a wall bug, I have always heard wall wart.

Where do you go 18->120->12? Yes that is much less efficient then 18VDC->12VDC. Same for 19.5, the number isn't that important, it's the fact you are going DC to AC to DC. DC to AC is an inverter and anything approaching efficient will cost hundreds to thousands of dollars. My 3,000W inverter was a top brand name and cost a few thousand.

PLEASE reply yes or no, what you want is to use your ample supply of 18VDC Lithium batteries to power some 12VDC devices of some sort, and also some USB 5.1VDC devices?

You MUST use the RYOBI supplied Lithium charger, the charging parameters for Lithium is VERY different than NIMH.

Keep in mind I repowered my 42ft RV with 6 100AH LiFePO4 batteries, the 3,000W inverter and 6 190W solar panels plus the usual accessories like an MPPT charger, shunt, all marine grade fasteners (zinc over copper) and the main battery/inverter cables were 4/0, the biggest you can order. My cost was close to 5 figures, my background includes being an industrial electrician for a couple years. Everything other than the AC, electric heaters, and washer and dryer were Solar powered and that includes the residential fridge, not a propane fridge (fire hazard).

@fidodie Does the following

I was going to use the old nimh chargers as a case for whatever is built since it can't charge the lithium batteries.  it will provide a solid connection to the battery.

mean you think you can build your own Lithium charger?

Do you not have a charger or two for your 15 RYOBI Lithium batteries?

LIGHT BULB. Now I remember you did say inverter, so 18VDC to 120VAC. That is not a smart approach for what you need. 

What I now expect is Ryobi Charger->Ryobi Battery->Ryobi (12VDC or 5VDC) Converter.

I have a similar setup with Makita 18VDC batteries and Makita USB Adapters.

DO YOU ALSO NEED 12VDC, OR JUST 5VDC as in USB?

I do NOT see a Ryobi USB Adapter on Amazon.ca, but here is the first listing I see in the USA

https://amz.cx/3KUL so you are in luck.

Posted by: @zander

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PLEASE reply yes or no, what you want is to use your ample supply of 18VDC Lithium batteries to power some 12VDC devices of some sort, and also some USB 5.1VDC devices?

Yes -

I want to use the shell of the nimh charging case to  do the above project - as it provides the battery connections - physical and electrical. 

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Still, the goal of the project would be to double the run time of the clock on one battery.

Otherwise i'd just carry another battery, or make a tandem battery holder for the inverter.

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i've heard wall wart too - 

Is your project documented - would like to see some pics!  I live on top of a hill, and would like to try something with wind/solar.

@fidodie I doubt you will get double run time by eliminating the 120V conversion step, so just carry a 2nd battery. 

The RV has been sold.

Sorry, I almost never document my work, I do have pages of rough notes during the project that get replaced, thrown out etc, but most of it is in my head. What is it you want to know, the basic design of wind and solar hasn't changed in years. Wind is a very low power source but in the right location can provide a continuous 'trickle' charge.

I highly recommend Will Prowse's web site. I also recommend Victron products other than batteries which you should build yourself from prismatic cells. I used Battleborn 100AH 12.8V batteries same size as a car battery but 1/2 the weight and very safe as they were LiFePO4. Of course the downside of being safe is much less energy density.

We are about to find out!

it is, and will always be about asking the right question!

There are better ways to charge a phone - so USB really isn't needed.