Battery power for my GX CS2

JimD said:

A couple days ago I got a GX CS2. I bought it from GX and used their 10% off code to get it for about $250. I like filling from my bottle which I fill using my Yong Heng. But it won't last forever and isn't very portable. I've taken the bottle to the range but it's pretty big. Anyway, I am not sure exactly what I will do with this so I got the normal CS2 to have 120V and vehicle power to use it. But I also wanted to be able to power it with my 18V Milwaukee tool batteries. So I bought a 18 to 12 V 240W step down converter from Amazon with a Milwaukee battery dock. I was a little worried it was only 240W but I done a dead head test and filled a gun with it and it seems to work fine. I thought about integrating it with the CS2 but decided, at least for now, to just have this little power unit I can clip to and use without modifying the compressor.

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Does the battery adapter have a low voltage cutoff built in to protect your batteries? If it doesn't I highly recommend at least one of the watt meters for rc to monitor your overall battery voltage(it will also show you current draw and Ah used) you can even calculate how many fills per battery so you can plan to bring more batts if you have as many as i do.

The way the Milwaukee battery monitoring circuit works it will show a full charge being 3 bars when you over draw or hurt a cell (first and last cells in series get measured 2 times iirc there's a whole writeup about the design flaw online)

I built a 50ah lifepo4 battery in a 50 cal ammo can with xt60 connectors on the face to run my pellet grills, portable fridge or compressor and it's been pretty rad, also cost less than a 6.0 m18. The large capacity m12 and m18 have treated me so bad in daily use that I switched to yellow for 18v and retired an impact price tag worth of tools.

Tldr; watch your level of discharge to save money .

Nice to see a fellow traveler with "the knack" keep up the great work and I look forward to hearing how you like it!

After building an m18, and a 20v dewilt (18v) like yours I went a little harder. 13.6v charged 12.0 discharged

JimD said:

Thanks for the suggestions. I've been using a 6 ah battery and two gun fills only dropped it to three bars. But the battery level indicator started flashing so I'm not sure if it doesn't like this load or if it might not have been in great shape. I'll try a different battery, probably a 8 amp hour. I plan to recharge the battery well before it gets fully depleted - does that address your under voltage concern? The first battery was at 18.9 volts when it started flashing which seems to be about right for 3 bars. I charged it back up to full which is over 20V (which may be why DeWalt calls theirs 20V). The compressor seems to run fine on the battery. I did a dead head test with 120V and with the battery before charging a gun and they took the same amount of time (about 25 seconds).

I have a big Milwaukee battery pack that supplies 120V and will run the Yong Heng and all it's extras. But it weighs 50 lbs and would just further make transporting the YH a challenge. The little CS2 with even a big 18V battery would still be less than 20 lbs.

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The blinking usually means an over current situation which goes in a counter intuitive direction. My experiences have been that the highest capacity batteries don't like to be drawn too hard for current. The two near instant failures I had in factory tools was the 8.0 m18 and 6.0.m12. It gets into the nuance of lithium ion cells and how they like to be worked. Typically but not always, lower capacity batteries are more tolerant of regular high current draw.

A workaround for your current issue could be another battery adapter and feeding your voltage converter with 2 batts in parallel.

My next concern is the bms circuit and how it works, this I can't speak definitively on, but i think that the tool and battery "talk" back and forth on what the battery can deliver and what the tool can demand. I can't recall if it's red or yellow, high or low voltage that has the issue. Esc to bms talk COULD be the low voltage cuttof recipe that I was preaching an abundance of caution about.

Charging them straight away is a good idea, the lvc is just there to prevent you from bricking the battery and having to do a sketchy "bump charge" to bring it back up to a voltage that a normal charger will allow it to proceed as normal. I do, and will do these things but stressing lithium cells can lead to a very energetic failure and losing the money for those pricey batteries or burning down other things. I haven't seen lion outside of ev applications do it or lifepo4 yet, but I've burned down a handful of lipo batteries. (like what dewalt just put on their power stack batts).

I dig what you're doing here I just wanted to pass along some of the costly errors I've made over the years. Like jumping my truck with one and bricking a 4.0 battery.