Power Inverters For Cordless Tool Battery Chargers

Hello all, I have 12v pure sine wave, 1500 watt power inverter, I am enable to charge my 18 volt cordless batteries, the charger doesn't even light up as if it is not plugged but  works fine using wall socket, however I have problem charging 12 volts cordless batteries using their separate 12v charger.
I also tried a small wheel grinder and doesn't work either when plugged to the inverter but works normal using wall socket.
The power inverter is very reputable brand name and it is pure sine wave, do you think that I should of bought 24v inverter instead?


  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    Welcome to the forum Alternative,

    Can you tell us more about your AC inverter (brand/model) and or link to it? What type/size (voltage/AmpHour) batteries?

    Note that if this is a 12 VDC battery bank, a 1,500 Watt inverter will draw over 100 Amps @ 1,000 Watt output... So you need very heavy/short wiring if you are going to use a lot of power (and a pretty heafty battery bank too).

    Are your tool chargers two blade or two blade+ground plugs.

    There are several reasons why you can have issues with inverters... From DC bus problems (too small of batteries, too small of wiring, blown fuse, bad wiring) to AC output (if has GFI outlet, may need to reset).

    Your AC inverter is certainly large enough Wattage to charge most standard tool battery chargers. And PWM is usually much better for running battery chargers vs MSW (modified sine/square wave) inverter (some, especially older, tool battery chargers will overheat pretty quickly on MSW inverters).

    Do you have some sort of AC+DC voltmeter? Check what the DC bus voltage is (most inverters need >12.0 volts to start, and will shut down at 10.5 VDC or lower).

    If you are going to purchase a voltmeter--You may want to look at an AC+DC Current Clamp DMM (digital multimeter). Makes it really nice to be able to measure AC or DC (battery) current when debugging/understanding your system:

    https://www.amazon.com/gp/product/B00O1Q2HOQ (good enough for smaller systems)
    https://www.amazon.com/gp/product/B019CY4FB4 (mid priced meter)

    And, also very nice is to have a Kill-a-Watt type power meter. Helps you better understand your loads and how much "energy" you use (power is a rate like miles per hour, energy is an amount like miles driven in a day)... Helps you plan your battery bank charging/solar panel needs and debug your inverter/AC wiring issues.


    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Alternative
    Alternative Registered Users Posts: 7 ✭✭
    Thank you for the warmth welcome,
    The power inverter is Ramsond brand, here is the link to all specs https://www.ramsond.com/sun1500-12v/
    I have two 12v SLA batteries connected in parallels, each is 100 H/A and fully charged, the power inverter is about 4 feet from the batteries with large cables. the tool charger cable has two blades, there is no blown fuse because when I plug in different device it works perfect.
    I have voltmeter but never tried to take readings because the inverter has voltage and watts indicators. I am thinking that my power tool charger is not compatible with my power inverter but I don't know the reason why, when I plug it in there is no change on the inverter regarding the voltage and watts, also the power on indicator doesn't light up on the tool battery charger.

  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    From the manual, I don't see any reasons that the battery chargers should not work (no obvious compatibility issues)...

    On some inverters, they have a "search mode". Basically, the inverter sends out an 115 VAC pulse once every second or two (search mode), and then when >8 watt AC load is found, the inverter "Turns On" full time. The "search mode" is to save power when you don't have any active AC loads (inverter takes ~12 Watts or 1 amp when running without loads).

    This inverter does not appear to have a search mode (i.e., a small load may not turn the inverter on).

    You could try plugging in two loads--One your being your charger, and another second "working" AC load (get the inverter loaded). This is an old trick used with generators--Have an AC load (such as a small heater) to get the genset frequency and output voltage stable--Should not be needed for inverters--But at least it is a good test of your inverter (both loads work, don't work, etc.).

    Using your voltmeter, measure the DC input voltage at the inverter terminals. And measure the AC output voltage.

    The 115 VAC +/- 10% means the low voltage could be 103.5 VAC -- That is a bit on the low side and the tool charger many not operate at that low of input voltage (guess). Your AC voltage range should be 110-132 VAC.

    With a 12 volt @ 200 AH SLA battery bank... I would suggest that a maximum ~500 Watt load for that size battery bank. Anymore than that, the battery bank voltage could collapse down towards 10 volts--Especially if the bank is at less than 75% state of charge (just a rough guess).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    This sounds like a inverter that has gone into Sleep or Standby mode and the small load of a charger is not enough to wake it up. What if you plug a 50w light in, and when the light is on (incandescent light, not LED) , see if your charger works then,

    I saw nothing in your inverter spec that hinted at a low power sleep mode though.
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

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  • Alternative
    Alternative Registered Users Posts: 7 ✭✭
    I tried the tricks mentioned above but still it doesn't power up, I tried all the 3 outlets of the inverter as well.
    Voltage DC and A/C are within specs, I plugged the tool charger to another low watts ( ~ 200 watts ) power bank that has USB, DC volt as well as A/C outlet and it worked fine.
    The tool battery charger input: 120 A/C 60HZ ~ 85 watt.  output: 12v ~ 19.2v 
  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    The only things left... It is possible that that inverter either has an electrical problem or is in fact an MSW type inverter (would not be the first time that a product was "mislabeled").

    About the only way to confirm would to connect to an oscilloscope and see what the wave form is (you have to be careful here--Many O'scopes used for electronics, when connected to 120 VAC power, can short out through the grounded scope leads. Only connect to 120 VAC if you know what you are doing.

    I cannot think of anything else at the moment.

    There are other things you can check with a voltmeter (AC Hot to ground voltage, AC Neutral to ground voltage, using a Kill-a-Watt meter and a simple load like a small heater and check Power Factor)--But while these tests may indicate issues--They are not a hard and fast proof of one way or another regarding output issues.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Alternative
    Alternative Registered Users Posts: 7 ✭✭
    Can a small wheel grinder also not work with MSW inverters? unfortunately I don't have an oscilloscope so I cant confirm if it PSW or not.
    I just hate to buy another inverter for my power tools, I initially bought good brand name and was advertised as pure sine wave because I knew I will need to upgrade my tools. now I am stuck.
  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    Very roughly, something like 30% of the power drawn by a motor from a MSW power supply is wasted as heat.

    For a grinder which starts with low loads and random loads--Usually induction motors will run fine on an MSW inverter.

    Motors that run compressors (such as a refrigerator), they can have fairly high starting torque requirements are are designed to run near full rated load (i.e, designed to run the motor rating to the compressor loads)--So the motor has a lot more heat build up (because of MSW)... So those types of applications (compressors, water pumps, fans) can overheat--So you need to watch the temperature of the motor. May run fine for years, could run hot and fail in months--Or could overheat in 20 minutes--No way of predicting what will happen to a specific motor set.

    Not saying your inverter is MSW or is running "rough"--Just a possibility.

    Another check--If you can use a volt meter to measure the other end of the charger cord (unplug from charger, pop open the charger and check the terminals for 120 VAC). It is possible to have a failing connection somewhere--But given that it runs fine on utility power and not on your inverter--That is probably not the issue.

    MSW inverters have lower "peak voltage" (around 150 Volts peak) vs PSW (around 175 Volts peak). Some battery chargers will not work well with the "lower" peak input voltage.

    The other issue with MSW--The sharp rise and fall edges... That tends to "stress" some components in power supplies (input diodes and capacitors). And for induction motors, the the MSW wave form has energy outside of the 60 Hz fundamental. For an induction motor, only the 60 Hz component causes the motor to rotate. The other frequencies are just wasted as heat.

    Electric heaters, filament bulbs, etc. "don't care" about the MSW wave form and work just fine.

    A very nice and readable website about generators and movie lighting... The basis also apply to inverters and their AC loads. Lots of drawings/photos/information:


    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • Alternative
    Alternative Registered Users Posts: 7 ✭✭
    That is a great link with the lot of information.
    So today I plugged in another tool battery charger that is rated to charge 20 volts batteries and the inverter worked fine, so far I tried 12v, 18v, 19.2v and 20v tool battery chargers and the inverter only works with 12v and 20v chargers.
    I ended up ordering another power inverter, hopefully it can accept all type of tool battery chargers.