Converting cordless to corded

[leenowell]

Hi All

I have a Graco paint sprayer and cutting a long story short am thinking of converting it to corded.

I have looked online and it seems at least for drills this seems doable how ever the ones I have seen so far have the batteries which push on to the dr ill and have 2 connections. The paint sprayer has an 18v slide on type lith ium ion battery with many connections and the sprayer has 3 connectors to t he battery.

Anyone ever tried doing this before? A few initial questions spring to mind

1. I can clearly identify the + and - but what is the 3rd one for and what should I connect it to? I have temporarily wired the + & - to a DeWalt batt ery + & - and it seems to work.

1. The sprayer says it is 15 amp so assume I need a transformer whose outpu t power is at least 270 Watts ? I have seen these

BDX6I

As an example so assume something like this would work?

1. I was thinking of striping out the cells from the existing battery and w iring just the 3 connectors the sprayer uses to the transformer. I assume t he rest can be left disconnected?

1. Maybe a daft question but presumably any wire I use has to be able to ha ndle 15 amps (or if I go for the 360 watt one I might as well ensure 20 amp s)? Is the fact that it is 18v DC important when selecting the cable? Eg is normal cable design for 20 amps at 240 v AC correct?

2. Any suggestions on the connectors to use? Was going to do a split in the cable so that in the future I could add other battery types of needed to t he same rig. Was planning on soldering connectors in the battery itself (a ssume any electrical solder is ok?) And assume the transformer will come wi th connectors to connect to it.

Any top tips etc or bitter experience of doing this would be greatly apprec iated

Thanks

Lee.

[Harry Bloomfield]

It happens that [e-mail] formulated :

20amps DC requires the same cable as 20amp AC. 240v cable will need to be more robustly insulated than that for 18v.

Powering it from a power supply will possibly make it a bit unweildy to use. A 240v version will probably be better.

[Fredxx]

I might suggest volt-drop becomes the overriding consideration.

[Harry Bloomfield]

Fredxx formulated the question :

Yes, good point, if the cable between the two is going to be longer than a few feet.

[tabbypurr]

f converting it to corded.

owever the ones I have seen so far have the batteries which push on to the drill and have 2 connections. The paint sprayer has an 18v slide on type li thium ion battery with many connections and the sprayer has 3 connectors to the battery.

t should I connect it to? I have temporarily wired the + & - to a DeWalt ba ttery + & - and it seems to work.

2 connections are fine, the 3rd monitors battery temp.

put power is at least 270 Watts ? I have seen these

that's a gamble

another gamble. Many such can only sustain a quarter of rated output

wiring just the 3 connectors the sprayer uses to the transformer. I assume the rest can be left disconnected?

yes, they're for charging

handle 15 amps

yup

fact that it is 18v DC important when selecting the cable? Eg is normal cab le design for 20 amps at 240 v AC correct?

mains flex has 2 layers of thicker insulation. You don't need that

I thought you already had the battery casing

her battery types of needed to the same rig. Was planning on soldering con nectors in the battery itself (assume any electrical solder is ok?) And ass ume the transformer will come with connectors to connect to it.

? What you want's a power supply, not a transformer

12v tools are easier :)

NT

[leenowell]

Thanks all for you advice. Much appreciated. I didn't quite follow the com ments about insulation. Is normal 240v 20amp certified cable ok? In terms o f the voltage drop issue, is there a type of wire which would make a notice able difference? I would have thought I would need about 3 or 4m of cable t o enable ceilings to be sprayed etc.

Yes I plan to use the battery casing and solder the cable to the connectors inside (using normal electrical solder?). The connector I was referring to was to split the cable between power supply and battery casing to enable m e to use the supply for other battery types.

[Harry Bloomfield]

[e-mail] wrote on 07/10/2018 :

Without knowing the actual current it normally draws and the starting current, it is impossible the answer. 20amp rated cable for 15amp load, ought to take care of both load and volts drop.

A decent power supply rated for that, will be expensive. You need to be looking at what is called a 'switched mode power supply' - a normal transformer type will be quite a heavy lump to carry around.

The lower the voltage, the higher the current for the same wattage. The higher the current the more voltage is dropped due to cable resistance. The lower the voltage the more voltage drop becomes a factor.

[tabbypurr]

omments about insulation. Is normal 240v 20amp certified cable ok?

sure, it just has excess pvc

ake a noticeable difference? I would have thought I would need about 3 or 4 m of cable to enable ceilings to be sprayed etc.

1.5mm2 has 44mV drop /m /1.5A. At 20A that's 0.586V. No big deal for the sp rayer, but it's 10W for the cable. Pick something fatter.

rs inside (using normal electrical solder?). The connector I was referring to was to split the cable between power supply and battery casing to enable me to use the supply for other battery types.

anything rated for 20A and not in use for something else is good.

NT

[tabbypurr]

oops x4m = 2.34v & 40W, no good at all.

2.5mm^2 -> 1.4v no 4mm^2 -> 0.875v 17.5W no good...

NT

[alan_m]

With a supply as cumbersome as listed then it probably needs to be left on the ground when spraying. Also, the battery is a sealed power source whereas the power supply is only designed for a indoor and clean environment and it may react badly to being over-sprayed with whatever substance is in the gun.

[Harry Bloomfield]

[e-mail] formulated on Sunday :

You (and the OP) may be confusing start current, with the run current. It cannot be drawing anywhere near 15amps when running, or the batteries would obviously last no time at all. Call the battery

3amp/hour 15amp load = 12 minutes run time.

[Harry Bloomfield]

alan_m formulated the question :

The SMPSU need be no bigger, heavier, or cumbersome than a typical desktop PC PSU. About the size of a brick, weighing maybe 0.5 Kg.

[tabbypurr]

I hadn't calculated it. If the OP knows the run time & battery capacity he can calculate apx run current.

PSUs vary in their overcurrent ie start current behaviour. Many shut down, meaning the compressor would never get going. On old fashioned supplies that could be fixed with a sufficiently huge capacitor. What a random smps would make of that I don't know.

NT

[dr.s.lartius]

f converting it to corded.

handle 15 amps (or if I go for the 360 watt one I might as well ensure 20 a mps)? Is the fact that it is 18v DC important when selecting the cable? Eg is normal cable design for 20 amps at 240 v AC correct?

Electrically, and in the absence of faults, thinner insulation would suffic e. But the insulation must also defend the wire from the external environm ent, and for that one must consider that it might be crossing a gravel path and get trodden on by football boots, it might be considered food-like by the local rabbits and squirrels, etc.

If the sprayer has exposed or exposable metal parts, all such need to be ei ther double-insulated from 230-volt-land or reliably earthed.

Remember Lord Finchley.

[The Natural Philosopher]

No. To drop 5 v at 240v 20A is no big deal. To drop it at 18V is. Use car style wires or specalist wires made for model cars/planes etc.

[The Natural Philosopher]

[newshound]

Two-core silicone? this one only comes in a five foot length but 1) it's nice and flexible and 2) it will deal with the voltage drop problem.

Single core is readily available in various gauges and decent lengths. You could bind two together with that spiral polythene stuff but then you would lose much of the flexibility advantage.

[Dave Plowman (News)]

Not if run from a suitable low volts supply.

[tabbypurr]

no, it's the psu that those apply to

NT

[John Rumm]

The cable typically used on DC tools is a high flexibility rubber insulated flex, with quite substantial cross section - the cores usually

2.5mm^2 or in some cases 4.00mm^2.

On my Mirka sander, they have used a locking Neutrik connector like:

It works very well, easy to connect or disconnect, not too bulky, and locks in place when in use.