Petrol generator damaging power tools?

[minilathe22]

Hi everyone

I am renovating a building that has no mains power connected at the moment, and I have a small petrol generator that I bought used. It can output mains 240v through a blue caravan style 16A connctor or via a switch 110v through a similar looking yellow connector.

Its almost identical to this model:
https://www.powertoolsdirect.com/clarke-pg3800a-3000w-max-petrol-generator

I have found two brand new power tools appear to have stopped working, having been used on "real" mains electricity without issue but after a few short uses on the generator they are now both dead. Fuse tested ok in the plug. Other devices still work on the generator so its not the output that has stopped. A Bosch angle grinder, and a Bosch chainsaw. Neither were the cheapest options.

When you start the power tool, you can hear the engine on the generator bog down briefly. I am wondering if some kind of power/voltage spike is being sent into the tools reducing their life? Is there any heavy duty filter I can plug inline to avoid this? Is it just a crappy generator?

 

[Katomi woodsmith]

I have the wolf version of your gen set, though mine is 3.5 kw
As others have said that the gen will dip in revs (bog down) until the tool is running at full speed. Mine has an auto throttle that cuts in and ups the revs when I start a tool.
The only probs I have had with gen set(s) is that when recharging cordless tool it’s so easy to overcharge and cook the battery as the cutout relies on an earth that gen sets don’t have
NB same problem happens on inverters sometimes.... I cooked an expensive Bosch battery by leaving it on overnight on my solar/batter/inverter system

 

[minilathe22]

I had not considered the earth connection. I have been lazy and not used it, the generator does have a mounting on the frame to attach an earth rod.

 

[macetownhouse]

Hello,
First l would find someone who knows how to read a multimeter, and check the output of generator. Some can fluctuate wildly. I have seen a few cheap one putting out huge differences.
In my option which is probably wrong a 6kv. generator is what is needed.
Power tools are two expensive to loss to a generator, maybe look at cordless.

 

[John Brown]

I have the wolf version of your gen set, though mine is 3.5 kw
As others have said that the gen will dip in revs (bog down) until the tool is running at full speed. Mine has an auto throttle that cuts in and ups the revs when I start a tool.
The only probs I have had with gen set(s) is that when recharging cordless tool it’s so easy to overcharge and cook the battery as the cutout relies on an earth that gen sets don’t have
NB same problem happens on inverters sometimes.... I cooked an expensive Bosch battery by leaving it on overnight on my solar/batter/inverter system

I've never heard of that - relying on an earth to terminate charge - as far as I knew, charge termination on Nickel cells is based on either temperature change or voltage change and on Lithium based on the current dropping below a specified level, in both cases there might also be a timer function as a belt and braces solution. I'd be intrigued to hear about the earth thing, especially as I'd swear that some of my chargers have plastic earth pins.

 

[Dabop]

I've never heard of that - relying on an earth to terminate charge - as far as I knew, charge termination on Nickel cells is based on either temperature change or voltage change and on Lithium based on the current dropping below a specified level, in both cases there might also be a timer function as a belt and braces solution. I'd be intrigued to hear about the earth thing, especially as I'd swear that some of my chargers have plastic earth pins.

That's because they don't....

In fact 99.99999% of chargers used for battery power tools use no earth at all (as they almost all use a switchmode power supply) and are in fact double insulated....

in fact switchmode PSU's are the safest option for use with inverters and generators, while mains powered motors can have some issues- predominantly involving those with variable speed controls, which are often relatively unprotected against voltage spikes- the older style single speed motor with a simple on/off switch are a better tool to use on most cheap genpacks, but really if you are using any genpack, spend the extra money and get an 'inverter generator'- they are far safer for any device....

Chargers for battery tools are almost invariably powered by a switchmode PSU (look for the 100-240v, 50/60hz label- if its got one of those, it's a switchmode) and these simply don't care how 'dirty' the power is- they can accept any voltage in their range (or even varying voltages like commonly found on smaller genpacks) of any frequency (or even straight DC!!!) or any waveform (pure sinewave, multistep modified squarewave, even a triangle wave or straight DC- a switchmode simply doesn't care lol)

As the input mains has literally no effect on the regulated voltage output being fed to the charge circuit, it has ZERO effect on the battery charging regime... so no- a generator will NOT' overcharge' your battery- it's an urban myth from 'ye olden days' of linear PSU's- which haven't been used in the last quarter of a century....

 

[woodieallen]

I've never heard of that - relying on an earth to terminate charge - as far as I knew, charge termination on Nickel cells is based on either temperature change or voltage change and on Lithium based on the current dropping below a specified level, in both cases there might also be a timer function as a belt and braces solution. I'd be intrigued to hear about the earth thing, especially as I'd swear that some of my chargers have plastic earth pins.

+1

 

[Katomi woodsmith]

Ok my tools are prob that old, I can here the gen kick now and then when tools are charged.
Yes it was on old Ni-cad battery drill that I cooked,
Ps sitting on a pontoon with a gen set using 240v drill is not safe apparently.... according to the chap who tore me a new one for being so stupid
He may of had a point the drill was starting to smoke.
Ah but there be the grace of God go I ___ saved from the stupidly of youth

 

[John Brown]

However old your cordless tools are, I'm struggling to envisage a mechanism for terminating the charge process that uses the earth connection. Using a 240v drill on a pontoon is, I would have thought, more dangerous to you than to the drill.

 

[Dabop]

However old your cordless tools are, I'm struggling to envisage a mechanism for terminating the charge process that uses the earth connection. Using a 240v drill on a pontoon is, I would have thought, more dangerous to you than to the drill.

IF they are 'REALLY' old- then it could be possible they still use a 'linear power supply'- in which case yes, they could damage the battery pack (and the charger)- but you are talking stuff thats probably 25 years or more old that has such a PSU- since the mid 1990's, switchmode PSU's have become almost everywhere- they are far lighter, run cooler, are smaller than linear PSU's, cheaper, and (for manufacturers)- you only need one PSU that works everywhere in the world, regardless of voltage or frequency- instead of one PSU model for 100v countries, another for 120v countries, another for 220v countries, another for 240v countries... with different models again for 50hz and 60hz countries...

A manufacturing nightmare lol

 

[minilathe22]

I am debating buying a decent inverter based generator, or a good quality inverter to connect to my small solar/battery system. I currently have a cheap "modified sine wave" inverter that I have found works ok with a water heater, but I suspect it could cause similar issues to electric motors.

 

[Chubber]

I had not considered the earth connection. I have been lazy and not used it, the generator does have a mounting on the frame to attach an earth rod.

Even when used to power double insulated tools a generator should be earthed, especially if like mine was, it's sitting on rubber-tyred wheels. You are unlikely to have earth leakage protection etc., and it's no big deal.

I simply used a car jump lead from the earth stud to a convenient nearby water pipe.

 

[Dabop]

I am debating buying a decent inverter based generator, or a good quality inverter to connect to my small solar/battery system. I currently have a cheap "modified sine wave" inverter that I have found works ok with a water heater, but I suspect it could cause similar issues to electric motors.

It really depends what you want to power with it...

'simple' tools without any speed control- just 'on/off' switch?
Doesn't really matter... fine on a 'cheap' non-inverter genny

'expensive' tools with variable speed controls?
Inverter genny...

With electronics...

Older electronics with linear transformers (usually marked as a 'single' voltage eg 240v/50hz)???
inverter genny or pure sine wave inverter...

Newer electronics with switchmode PSU (100-240vAc,50/60Hz label)- any genny, any inverter... (modified sinewave inverter is fine)

The main reasoning that the old 'generators are electronics killers' or that 'you need a pure sine wave inverter for electronics' no longer really applies is because almost all modern electronics has switchmode PSU's in them- and the very first thing they do to the incoming mains voltage is rectify it to DC!!!

The above circuit diagram, the incoming mains comes in the left, goes through the commonmode filter (which is often left out in 'cheap andnasty' switchmodes unfortunately- it supresses noise from the PSU from being injected back into the mains...)and is then rectified to high voltage DC (depending on the incoming mains voltage, could be from about 170v to up over 360v!!!) which is then regulated by the switching circuits to whatever voltage is needed (in this case 12v at 5A maximum- regardless of the mains voltage!!!)

This is 'ye old linear' switching power supply- really became obsolete in the 1990's, and very rarely seen these days... (this is the one that gave rise to 'generators are electronics killers')

That transformer at the beginning of the chain is the issue... the slightest variation in input voltage is reflected into the whole system (so hook a '110v' 12v PSU into the UK's '230v' mains,and you will effectively get 24v out instead of 12v!!!! (or more likely- bits blow up...)

 

[John Brown]

It really depends what you want to power with it...

'simple' tools without any speed control- just 'on/off' switch?
Doesn't really matter... fine on a 'cheap' non-inverter genny

'expensive' tools with variable speed controls?
Inverter genny...

With electronics...

Older electronics with linear transformers (usually marked as a 'single' voltage eg 240v/50hz)???
inverter genny or pure sine wave inverter...

Newer electronics with switchmode PSU (100-240vAc,50/60Hz label)- any genny, any inverter... (modified sinewave inverter is fine)

View attachment 194991

The main reasoning that the old 'generators are electronics killers' or that 'you need a pure sine wave inverter for electronics' no longer really applies is because almost all modern electronics has switchmode PSU's in them- and the very first thing they do to the incoming mains voltage is rectify it to DC!!!

View attachment 194992
The above circuit diagram, the incoming mains comes in the left, goes through the commonmode filter (which is often left out in 'cheap andnasty' switchmodes unfortunately- it supresses noise from the PSU from being injected back into the mains...)and is then rectified to high voltage DC (depending on the incoming mains voltage, could be from about 170v to up over 360v!!!) which is then regulated by the switching circuits to whatever voltage is needed (in this case 12v at 5A maximum- regardless of the mains voltage!!!)

This is 'ye old linear' switching power supply- really became obsolete in the 1990's, and very rarely seen these days... (this is the one that gave rise to 'generators are electronics killers')
View attachment 194993
That transformer at the beginning of the chain is the issue... the slightest variation in input voltage is reflected into the whole system (so hook a '110v' 12v PSU into the UK's '230v' mains,and you will effectively get 24v out instead of 12v!!!! (or more likely- bits blow up...)

Well yes, but also because the 7812 is being "assisted" by the two transistors for extra power. The 7812 by itself would cope with a fair variation in input voltage, although obviously at a lower current.

 

[Dabop]

With the transformer putting out a minimum of 30v, you are already pushing the 7812 right to its limits (not to mention the caps and transistors)- certainly it may work for a short period of time- but more likely it would fail almost immediately (the '15v' transformer is only rated at that at its loaded output current, unloaded it would rise higher), and with the 7812 having an absolute max voltage of 35v, it has precious little headroom left for any rise in voltage...

 

[Spectric]

However old your cordless tools are, I'm struggling to envisage a mechanism for terminating the charge process that uses the earth connection.

The "Earth" connection has only a single function and that is for safety and to allow protective devices to disconnect on a fault. I have not seen any chargers that are not class 2 rated, ie double insulated and without an earth connection. As for charging, you have a constant voltage stage and a constant current stage and sometimes a maintenance phase but without any reference to ground, just not required.