60 volt lithium battery to 240v AC as a portable power station.

[Waynemarlow]

Hi, I have a need regularly for 240AC of about 1000 - 1200W's ( large drills and cut off saws ) where AC is not normally available. I could run a small generator but I have about 1600Wh's of 60V ( 14S ) lithium Ebike batteries that would do the job nicely if I could find a suitable 60 volt input AC invertor. Finding that relaible invertor @ 60 volts input has been illusive to date with the 2 purchased invertors all claiming 4000W's but both only running around 500W's max continuous.

Can anyone point me in the direction of a suitable invertor or has anyone used say a PV Panel / house setup with say 3 of the 58 volt batteries in series. If so has anyone tried going down this route and it has succeeded.

Perhaps getting the 58V down to 24V's where it seems there are a wider selection of invertors. How would one do that at the amps I'm talking about without to much heat and loss.

Open to ideas but a small carry box with the invertor and batteries in does sound attractive.

Thanks

 

[beemac]

Hi, I have a need regularly for 240AC of about 1000 - 1200W's ( large drills and cut off saws ) where AC is not normally available. I could run a small generator but I have about 1600Wh's of 60V ( 14S ) lithium Ebike batteries that would do the job nicely if I could find a suitable 60 volt input AC invertor. Finding that relaible invertor @ 60 volts input has been illusive to date with the 2 purchased invertors all claiming 4000W's but both only running around 500W's max continuous.

Can anyone point me in the direction of a suitable invertor or has anyone used say a PV Panel / house setup with say 3 of the 58 volt batteries in series. If so has anyone tried going down this route and it has succeeded.

Perhaps getting the 58V down to 24V's where it seems there are a wider selection of invertors. How would one do that at the amps I'm talking about without to much heat and loss.

Open to ideas but a small carry box with the invertor and batteries in does sound attractive.

Thanks

48v is a pretty common voltage for inverters, those I just looked say they'll accept up to 60-66V.... Haven't tried any though!

 

[Waynemarlow]

The two I've tried both say they'll produce 2000W's and 4000 W's peak but both limit back to about 500W's in just a few seconds. Maybe just unlucky.

Any reliable invertors in that range can anyone recommend ?

 

[harrisonpatm]

The two I've tried both say they'll produce 2000W's and 4000 W's peak but both limit back to about 500W's in just a few seconds. Maybe just unlucky.

Any reliable invertors in that range can anyone recommend ?

Are you sure they're actually limiting at 500w? I ask because you mention your main use for this setup is large drills and cutoff saws. On large motors like that, even though they use 500w to run at medium duty, can often require a surge startup current for a few seconds to get running, or use surges of current when they encounter a tough load. How much more? As much at 10x more, for a second or two, in my experience. So it could be that the startup current requirement quickly exceeds even the 4000w surge current rating of your inverters.

I bring it up as a possibility because I ran into the same issue with my small solar setup, my older motors all had trouble running on my 2000w inverter. The other variable is that it is rather common for inverters to exaggerate both their running load and surge load capabilities.

Moving forward, you could consider even higher output inverters, like in the 4000-6000w constant load range. Also look for low-frequency inverters, rather than high frequency. Unfortunately by that point, you're looking at spending upwards of $1000, so it may not be worth it for you.

Open to ideas but a small carry box with the invertor and batteries in does sound attractive.

Also may not be worth it to you because a low-frequency 6000w inverter could weigh 100 pounds, not at all a small carry box. Perhaps a rolling dolly or cart, though?

Just two examples, there's plenty more out there.

 

[Waynemarlow]

Thanks, yes the 1000W drill will start no problem free load but as soon as you load it up both the inverters I tried stopped at about 500W's. One of them was supposedly an 8000W unit ( 4K constant ) but obviously not.

Looked at those conversions into a box and its the batteries that weigh. The Lithium batteries I have are in the 3kg range ( 800Wh's ) and the inverters are only 2 - 3Kg so all in all quite almost a small tool box type case. I only need the drills and breakers for such a limited time thats I would never need the 1600Wh's I have on hand.

I'm pretty sure that with the right inverter the whole idea would work but it would seem its the quality of the inverter thats giving me grief. I looked at some of the house PV inverters and they are ideal in some ways but are huge in size negating the small carry box.

 

[Papa]

".... I only need the drills and breakers for such a limited time thats I would never need the 1600Wh's I have on hand....."

Limited use?...
Some smaller 3-4kW generators are 240Vac capable. I know because I own one. Mine is an older Honda EG3500. I use it primarily for MIG welding. I have both the generator and the welder mounted on Harbor Freight's garden trailer for convenient portability....

 

[Waynemarlow]

Agreed but not too many people like to have gene's running in their lounge. Working in London and can be a pain sometimes

 

[amberwolf]

Thanks, yes the 1000W drill will start no problem free load but as soon as you load it up both the inverters I tried stopped at about 500W's. One of them was supposedly an 8000W unit ( 4K constant ) but obviously not.

Plenty of inverters don't seem to handle inductive loads (motors) very well. Especially brushed motors as are used in the typical power tool, which produce HUGE amounts of RF noise directly on the AC input line. The noise might mess with the power electronics in the inverter, causing it to either roll back power or shutdown, if it doesn't actually blow it up.



I'd recommend making sure the inverter is tested and rated to run large brushed motors--if it doesn't specify this in the factory ratings, and you don't see a review out there with a video showing it happen, skip that one.

I blew up a small Jensen inverter (about the size of a large battery charger) just trying to start a small powerchair motor with no load on the motor. (the inverter was rated higher than the motor load should have been, so the reason would probably be the inductive startup load spike and the RF noise from the brushes).


I have a 3kw harbor fright inverter that at least for those posting videos of it at the time does work for this purpose, but it's not 240v, and I can't imagine the same one is still made so many years later. It is the size of three or four thick encyclopedia volumes (or a bigger small bag of dog food), and definitely weighs more (at least as much as a small-medium ebike battery), and I don't think it could run my B&D mower.

 

[nicobie]

Power electronics is not my cup of tea, but can't you run brushed motors on DC?

 

[amberwolf]

Sure...if it's high enough voltage to spin them fast enough for your purpose.

And...if your power source is tolerant of the huge amount of RF noise the motors are going to crap all over it with. And the initial surge current (which can be VERY high).

(meaning, it won't kill the BMS in a battery if it's directly connected to it)

A potential (but not guaranteed) solution to those last two is to use a brushed motor controller (of the necessary power level) on the device, and use a switch or potentiometer instead of a throttle, so you turn the pot or switch to zero output, connect it all up, then turn up the pot or turn on the switch to full output, then go use your tool.

Doesn't fix the first problem, though. If you only have a say, 52v battery, the tool meant to run on 240vac is not going to run very well or have much torque or speed.

 

[nicobie]

I must have read it wrong but I thought he had 3 58V batteries (174V in series) and all he needed to run was a drill and chop saw which don't really care what speed they run at.

 

[amberwolf]

If they are typical batteries with a BMS, it's not safe to series them, becuase it is unlikely their FETs can handle the full voltage of the pack. If they cannot, and one of the packs turns off it's output for any reason, it's FETs will be damaged or destroyed. If they are destroyed it just opens the circuit and all you have to do is replace the BMS (or it's FETs).

But if they are damaged they usually fail shorted (stuck on), so the circuit doesn't open and you don't know that this problem has occured...and now your BMS cannot ever turn it's output off to prevent overdischarge, overcurrent, etc, and you won't know that there is a problem until the cells are damaged enough to cause some obvious problem you can see (severe voltage sag, loss of capacity, etc) or a fire.

There are things you can do to more safely series packs, putting diodes in parallel with the output FETs (see the posts in various threads by Fechter about this), but those diodes have to be able to handle the full current of the load (or they may fail and if they fail open then the FETs see the full voltage and....


And...the system (BMS) is still vulnerable to the RF from the brushes.

And...the tools will not be running at full speed (or torque), which could be important for a particular usage (mgiht not be, but could).

 

[Waynemarlow]

Thanks guys. I didn't know about the serial implications of the voltage across the FET's.

So that really only leaves a 60 volt inverter which it would seem is difficult to find ( thats reliable and not over enthusiastically rated by the seller ).

 

[beemac]

Thanks guys. I didn't know about the serial implications of the voltage across the FET's.

So that really only leaves a 60 volt inverter which it would seem is difficult to find ( thats reliable and not over enthusiastically rated by the seller ).

How much do you want to spend? At least with rs you can return pretty easily. TN-3000-248B | Mean Well Pure Sine Wave 3000W Power Inverter, 42 → 60V dc Input, 230V ac Output | RS

If the other inverters you tried had a higher nominal input voltage than 60v (even though they accept lower voltages) then the max power will be at the rated nominal voltage (and corresponding lower amps) so that might be the issue?

I've run 600w saws from a cheap 12v/1000w (might be 1500w it's not here atm) inverter just fine so you should be ok with yours and a bigger inverter

 

[Waynemarlow]

Thanks

Price is a tad high for that unit. For the same money you could buy a 54 volt core drill and a spare battery or two.

Seems a pity to throw the old favourite 240 volt tools away, I had hoped to avoid that but its looking to be the best option in some ways. But I'll still have the problem of moving away from gas cooking in my camper to induction hobs where that same inverter would be handy.

 

[Papa]

So that really only leaves a 60 volt inverter which it would seem is difficult to find ( thats reliable and not over enthusiastically rated by the seller ).

Many 48v rated inverters (here in the USA) accommodate well over 60v input. Why?... because when permanently connected to a decent solar controller, can frequently see 60-65Vdc during equalize (charging FLA's) . My 48-1200 Victron does exactly that. It also handles 1100w microwave or induction cooktops, or smaller 4.5" brushed grinders. You need the check to specs before you buy.

 

[floydr]

As Papa said Check the specs on 48V inverters many have a range that will work with 14s batteries. Your battery bank might be too small to support more than 500 watt output which if I calculated right is only around 33Ah. My 6kW 48V growatt LF inverter recommends a battery bank of 200Ah. Cutoff saws might only be 1200 watts when running but when starting they can draw 3-5 times that amount.
Later floyd

 

[Waynemarlow]

As Papa said Check the specs on 48V inverters many have a range that will work with 14s batteries. Your battery bank might be too small to support more than 500 watt output which if I calculated right is only around 33Ah. My 6kW 48V growatt LF inverter recommends a battery bank of 200Ah. Cutoff saws might only be 1200 watts when running but when starting they can draw 3-5 times that amount.
Later floyd

52 volt at 14S with 30A BMS's fitted batteries. Should give at 25A's ( 25A x 52V ) 1300W's fairly comfortably. On my EBike you can see 1200W's peak without a problem.

So what about fitting an inline soft start to try and ramp up the A's ? any quick solutions in this direction ?

 

[amberwolf]

If the devices are simple brushed motors, you could find a big brushed motor controller and use it's throttle to ramp up the output to full. Use a pot instead of an actual throttle for ease of use.

There are also devices made for RV's, etc, to keep the startup load of motored appliances from popping inverters, but I expect those will cost more than a brushed controller would.