Puzzle?

[EFLImpudence]

I have an 18V cordless Sealey CP2518 car polisher.

I have only used it once and then charged the battery.
I left it on all night by mistake despite it saying 5 hours to charge.

The next morning the battery measured 20V - fair enough.


Then I noticed the charger label states - the exact formation:

CP 2518.V2-20
230V-240V AC 50-60Hz.
16W 15Vd.c 400mA

I thought the 15V odd and wondered how the battery got to 20V so measured the output and it is 29.77V.

What am I missing?

Any views?

 

[JohnW2]

I have an 18V cordless Sealey CP2518 car polisher.... The next morning the battery measured 20V - fair enough.
Then I noticed the charger label states - the exact formation: ... CP 2518.V2-20 .... 230V-240V AC 50-60Hz. ... 16W 15Vd.c 400mA
I thought the 15V odd and wondered how the battery got to 20V so measured the output and it is 29.77V. .... What am I missing?

Weird. One obviously is not going to charge an 18V battery with a 15V source! Whatever the writing says, your charger was clearly supplying at least 20V.

"CP 2518.V2-20" makes one wonder. Is it possibly (at least 'partially') a 400mA constant-current source (albeit that would seem rather odd for a battery charger) with an output of 2V - 20V (which would equate to 6W IF the voltage output were 15V) ??

29.77V completely off-load is probably not impossible for a ('cheap') device designed to charge an 18V battery. Have you measured the charger's output voltage with some sort of load (not the battery) connected?

Kind Regards, John

 

[EFLImpudence]

Thanks John.

No load output now reading 28.5V.

I connected it to -

a 240V 12W glue gun, then
a 240V 60W filament bulb.

In both cases it just went down to 26.5V.

 

[EFLImpudence]

I have another charger for a 12V drill.

That is similarly labelled 13W 15V 400mA.
The no load reading on that is 18V.

 

[JohnW2]

Thanks John. No load output now reading 28.5V.
I connected it to - .... a 240V 12W glue gun, then ... a 240V 60W filament bulb. ... In both cases it just went down to 26.5V.

Those loads aren't really high enough. If they had the same resistance with 26.5V as with 240V, they would only correspond to currents of about 5.5 mA and 27 mA respectively.

To get something like 400mA (at 26.5V), you would presumably need a resistance of about 66Ω - which would correspond to a (purely resistive) load of about 870W at 240V. Given that the voltage will presumably drop appreciably (below 26.5V) with such a load, then maybe an ~1kW largely-resistive load (at 240V) would be appropriate?

Maybe this is a situation in which you really need an oscilloscope - since goodness knows what is the waveform of this "DC" you are measuring!?

Kind Regards, John

 

[EFLImpudence]

Ah, forgot I had a radiator.

53.4Ω (991W @ 230V) reduces it to 20.7V.
27.6Ω (1920W @ 230V) reduces it to 17.2V.

 

[JohnW2]

Ah, forgot I had a radiator. 53.4Ω (991W @ 230V) reduces it to 20.7V.
27.6Ω (1920W @ 230V) reduces it to 17.2V.

OK. That's about 'right' (for something designed to charge an 18V battery at @~400mA), isn't it?

I think that leaves us with the conclusion that the only thing which is 'plain wrong' is the "15V" marking on the charger, doesn't it? I might have asked you to confirm that it wasn't an 'eyesight problem', but their "6W at 400mA" is certainly consistent with 15V.

Maybe they just put the wrong sticker on the charger, or something like that?

Kind Regards, John

 

[EFLImpudence]

OK. That's about 'right' (for something designed to charge an 18V battery at @~400mA), isn't it?

If you say so.

I think that leaves us with the conclusion that the only thing which is 'plain wrong' is the "15V" marking on the charger, doesn't it?

Yes.

I might have asked you to confirm that it wasn't an 'eyesight problem',

No. Magnifying glasses because that is what I thought at first.

but their "6W at 400mA" is certainly consistent with 15V.

It is - but it says 16W.

Also the drill charger stating "13W 15V 400mA".

Maybe they just put the wrong sticker on the charger, or something like that?

That is what I thought although it has the same number as the polisher.

 

[JohnW2]

If you say so.

It's not rocket science. You said that your battery got charge up to 20V. With your 991W (at 230V) radiator, the voltage from the charger was 20.7V (around 387 mA, therefore very close to 400mA) - so that all 'sounds right.

No. Magnifying glasses because that is what I thought at first.

Fair enough.

It is - but it says 16W.

So it does As you can see from my post#2, I read it as 6A (which worked out right). If it is really anything approaching 'DC', then "16W 15Vd.c 400mA" is just plain wrong - as I wrote (when I mis-read it!), 400mA at 15V is 6W (not 16W).

Also the drill charger stating "13W 15V 400mA".

Ditto. 'Plain wrong' (again, it should be 6W) if it is anything approaching 'DC'.

Kind Regards, John

 

[RandomGrinch]

I like puzzles!

From a copy of the manual:
https://manualzz.com/doc/19486587/cp2518

I get the feeling there has been a mix up with the manual, or the product was updated before it went to market.
There are several references to 15V and the product is is even called a CP2515 once - although I can't find any online source for a CP2515 existing!

...and the base is a non-intelligent NiCad charger, it's probably best not to overcharge the battery

EDIT:
20 to 21V is about right, for an 18V NiCad coming straight off charge.
NiCads are also usually charged from a constant current source at around 1/10 of their rated Ah - a voltage rating on the charger isn't completely relevant!

 

[JohnW2]

From a copy of the manual: ... I get the feeling there has been a mix up with the manual, or the product was updated before it went to market. .... There are several references to 15V and the product is is even called a CP2515 once - although I can't find any online source for a CP2515 existing!

I'm not sure what you are suggesting. If you were suggesting that it's actually a 15V battery (hence closer to being consistent with what is written on the charger), then how could/would you explain ...

20 to 21V is about right, for an 18V NiCad coming straight off charge.

(Which is something that I have also written/implied above, and also consistent with EFLI's measurements on his charger when loaded to ~400mA) ??

NiCads are also usually charged from a constant current source at around 1/10 of their rated Ah - a voltage rating on the charger isn't completely relevant!

Indeed. As I mentioned in my first response above, the "V2-20" part of the charger number might possibly relate to a 2-20V voltage range of a (400 mA) constant-current charger. EFLI has shown the the open-circuit output voltage is a lot higher than 20V, but maybe it cannot provide 400mA at voltages appreciably above 20V?

It still seems to me that it's most likely that the only think wrong is the labelling of the charger.

..and the base is a non-intelligent NiCad charger, it's probably best not to overcharge the battery

Indeed so.

Kind Regards, John

 

[RandomGrinch]

I'm not sure what you are suggesting. If you were suggesting that it's actually a 15V battery (hence closer to being consistent with what is written on the charger), then how could/would you explain

I'm suggesting that the inconsistencies in the manual and printing could suggest that the model was planned as a 15V model before a late change to 18V for manufacture.
Or, simply, there are a surprising amount of misprints!

Indeed. As I mentioned in my first response above, the "V2-20" part of the charger number might possibly relate to a 2-20V voltage range of a (400 mA) constant-current charger

Yes, you did mention it in your first post, but to clarify for any other readers, typical NiCad chargers are constant current and not at all odd!

"CP 2518.V2-20" makes one wonder. Is it possibly (at least 'partially') a 400mA constant-current source (albeit that would seem rather odd for a battery charger)

 

[ericmark]

Years ago in the days of NiCad I looked at the chargers. There were three types.
1) ΔV these used the fact a NiCad drops slightly on voltage when fully charged, and the charger looked for this slight drop, and then gave a fixed time after the drop. It used constant current.
2) Temperature these had a sensor in the battery, and used the fact electrical energy to chemical energy does not produce as much heat as electrical energy to heat so once fully charged the thermal temperature sensor would open and the charger would latch so stop charging until battery removed and refitted.
3) A instruction to user to remove after set time, common was 16 hours and it would in fullness of time over charge the battery but the battery could stand the over charge for a limited time.

As we went to NiMh the ΔV did not work as well as with the old NiCad and today we have so many types, Li-Ion often had electronics built in image from Wikipedia, and today it is near impossible to know how each type should be charged other than follow manufacturers instructions.

The charger for my e-bikes auto switch off, and monitoring the power used by the charger I can see when complete, but there is very little to tell one other wise when complete. However the instructions say "Batteries should be fully charged immediately when they are received and immediately after each use for the recommended charge times (see below). Li-lon (Lithium lon) batteries 4-6 hours (2-3 hours for Via brand)" this tells one how long it takes rather than a fixed time limit.

Even with the old flooded lead acid often the charger used the difference between RMS and peak to reduce charge rate as battery is recharged, with the AGM or VRLA over charging needs to be avoided, and today content current chargers are used which charge in stages dictated by the voltage. In the car the engine management notes when it was last fully charged, the same applies with lap top batteries.

Even a 2500 mAh Ni-Mh AA cell says 500 mA for 7 hours. Which is often a problem as early chargers were designed for 500 mAh and have a timer which turns them off before the larger battery is fully charged.

 

[JohnW2]

I'm suggesting that the inconsistencies in the manual and printing could suggest that the model was planned as a 15V model before a late change to 18V for manufacture.

Fair enough, but that, in itself, would not necessarily explain the labelling of the charger, would it (they presumably have chargers for both 15V and 18V products)? I'm perhaps more inclined to subscribe to ...

Or, simply, there are a surprising amount of misprints!

For a start, the labelling/marking of the charger is either very badly worded or 'misprinted' - since (once one reads them correctly ) the V, A & W they quote don't 'add up'.

Yes, you did mention it in your first post, but to clarify for any other readers, typical NiCad chargers are constant current and not at all odd!

Yes, my "odd" comment (which I only added as an {ill thought-out!} afterthought) was inappropriate and potentially confusing. I was probably thinking of Lithium batteries - for which 'protracted' (as EFLI did!) continuous constant-current charging (with no added bells and whistles) would presumably be 'bad news', wouldn't it?

Kind Regards, John

 

[EFLImpudence]

Thanks for all the comments.

There are pictures on the web where the chargers have specifications that do match so obviously something wrong on mine.