FLUKE 8050A searching adjusting tip to set DC at 0000

[Kiriakos GR]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

"Interesting amount of comments but with out value to me." We all know that your are an expert in batteries.

a) Oh thanks for pointing out the world We it translates that you are part of one imaginary army.
b) I am as person an more intelligent temperature monitor than a thermal sensor of 0.20 $.
c) I do not use luck in my life, this is why I do not even play the Lotto game.

Either way I do appreciate your contribution in this thread.

[budm]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

You are seeing the harmonics of the DC-DC converter.
"The 8050A with out batteries connected at those pins there is a voltage reading as 30V." You better check your way of measuring the circuit also, or read the diagram."

"Interesting amount of comments but with out value to me." We all know that your are an expert in batteries.
Yes you know so much that you kill the batteries:
"What looks interesting is the fact that even by using a lower rated 250 mA NiCD from a cordless phone, the overnight charging it killed it."
"Improvising about the use of materials made for some other use, it is safe only for the person who has the experience and knowledge to examine and test any parameter of danger up-front. "

"more opened views than the Google search engine" Any more open view than Ti documents?
By the way, that Nokia batteries has third pin for temp monitoring if the temp gets too high, the charging will be terminated, but you are not using that pin, so good luck.

[Kiriakos GR]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

Interesting amount of comments but with out value to me.

The 200Hz is printed on the PCB next to the pins for the battery, blame FLUKE that wrote something inappropriate on it.
Thankfully I do own an Oscilloscope those days and I did see this pulsing with my eyes.

Thin Li-ion batteries for cell phones, I am challenging any one about getting in to the process to dismantle one of them.
A strip of copper + a strip of aluminum + a bit of active chemistry in the form of dry paint, and all those elements packed up by a nylon heat-shrink ed bag.

My last word about those very small in power Li-ion batteries is that they look capable to tolerate some soft abuse which it can also caused even by a regular
mobile phone charger which has been out of the tight specifications since when was new.

Improvising about the use of materials made for some other use, it is safe only for the person who has the experience and knowledge to examine and test any parameter of danger up-front.

I am not seeking for any public approval from any one, but if there is any people out there with more opened views than the Google search engine, they might find my approach as interesting. :-)

[budm]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

Post 9:
"What looks interesting is the fact that even by using a lower rated 250 mA NiCD from a cordless phone, the overnight charging it killed it." Well it is being forced charge by 137mA of constant current non stop over night.

Post 14:
"The 8050A with out batteries connected at those pins there is a voltage reading as 30V.
The explanation is that the charging are made by pulses at 200Hz."
The filter cap (C23, 2200UF/16VDC) voltage rating for the power supply is only rated at 16Vdc, that 30V reading cannot not be right.
And no pulse charging either, just plain 137mA constant current source with not output voltage regulation.
If the charging is that simple, they will be selling simple power supply with LM317 setup as constant current source real cheap without any safety concern.

Learn more about charging Li-ion from Ti and what you can build:
https://cdn.badcaps-static.com/pdfs/...28646f4d3a.pdf
https://cdn.badcaps-static.com/pdfs/...db77cdc5e1.pdf
https://cdn.badcaps-static.com/pdfs/...713ab6a725.pdf

[budm]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

If you look at the charging circuit, it is real simple constant current source charging. The U26 (LM317?) voltage regulator is setup as constant current source, not PULSE CHARGING. The charging current is 1.25V/9.1 Ohms = 137mA (Power switch is off, but the power supply is still running to charge the batteries when the meter is OFF) output voltage will be the Vdc on the input of U26- Vdrop across the U26. When power switch is activated, the 12 Ohms resistor is in parallel with the 9.1 Ohm to increase the constant current.
The simple DC-DC converter is made to work on 4.8V, when you use 7.2V, the output from the converter will be higher than design, better verify.
Per post 10 "While the meter uses 130 - 140mA at normal operation, at charging is capable for 200 - 240mA ( measured by Fluke 28II). " that is not the charging current you are testing since the power switch is not in the OFF position, the total current is split into the batteries and the circuits' current draw. The constant current of 1.25V/5.1 Ohms (Notes: 9.1 Ohm in parallel with 12 Ohms = 5.1 Ohms) = 240mA when the power switch is on.
So after 20 Hours, you better remove the charge, since in 20 Hours the total current charge will be 2.74A (137mA x 20) that the batteries received.

[budm]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

http://www.edn.com/design/power-mana...ing-and-safety
"The main challenge in charging a Li-Ion battery is to realize the battery's full capacity without overcharging it, which could result in catastrophic failure. There is little room for error, only ±1%. Overcharging by more than +1% could result in battery failure, but undercharging by more than 1% results in reduced capacity. For example, undercharging a Li-Ion battery by only 100 mV (-2.4% for a 4.2-V Li-Ion cell) results in about a 10% loss in capacity. Since the room for error is so small, high accuracy is required of the charging-control circuitry. To achieve this accuracy, the controller must have a precision voltage reference, a low-offset high-gain feedback amplifier, and an accurately matched resistance divider. The combined errors of all these components must result in an overall error less than ±1%."
http://batteryuniversity.com/learn/a..._ion_batteries
So if you use simple constant current charging circuit to charge Li-ion and not terminate the charging, you will find out sooner or later what will happen. Proper charger for Li-ion is a must.

"Li-ion cannot absorb overcharge, and when fully charged the charge current must be cut off. A continuous trickle charge would cause plating of metallic lithium, and this could compromise safety. To minimize stress, keep the lithium-ion battery at the 4.20V/cell peak voltage as short a time as possible.
Once the charge is terminated, the battery voltage begins to drop, and this eases the voltage stress. Over time, the open-circuit voltage will settle to between 3.60 and 3.90V/cell. Note that a Li-ion battery that received a fully saturated charge will keep the higher voltage longer than one that was fast-charged and terminated at the voltage threshold without a saturation charge.
If a lithium-ion battery must be left in the charger for operational readiness, some chargers apply a brief topping charge to compensate for the small self-discharge the battery and its protective circuit consume. The charger may kick in when the open-circuit voltage drops to 4.05V/cell and turn off again at a high 4.20V/cell. Chargers made for operational readiness, or standby mode, often let the battery voltage drop to 4.00V/cell and recharge to only 4.05V/cell instead of the full 4.20V/cell. This reduces voltage-related stress and prolongs battery life."
"Overcharging Lithium-ion

Lithium-ion operates safely within the designated operating voltages; however, the battery becomes unstable if inadvertently charged to a higher than specified voltage. Prolonged charging above 4.30V forms plating of metallic lithium on the anode, while the cathode material becomes an oxidizing agent, loses stability and produces carbon dioxide (CO2). The cell pressure rises, and if charging is allowed to continue the current interrupt device (CID) responsible for cell safety disconnects the current at 1,380kPa (200psi).
Should the pressure rise further, a safety membrane bursts open at 3,450kPa (500psi) and the cell might eventually vent with flame. The thermal runaway moves lower when the battery is fully charged; for Li-cobalt this threshold is between 130–150C°C (266–302°F), nickel-manganese-cobalt (NMC) is 170–180°C (338–356°F), and manganese is 250°C (482°F). Li-phosphate enjoys similar and better temperature stabilities than manganese.
Lithium-ion is not the only battery that is a safety hazard if overcharged. Lead- and nickel-based batteries are also known to melt down and cause fire if improperly handled. Nickel-based batteries have also been recalled for safety concerns. Properly designed charging equipment is paramount for all battery systems"

No way I will put Li-ion in place of Ni-Cad and sign off the paper and give that equipment back to customer.
"I did test this setup for two days, I can almost sign an warranty paper that this setup is truly capable even for 9 hours operation." Safety, what safety! LOL.

[tom66]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

It's nothing to do with warmth! Well, not initially.

It's to do with the potential for the voltage to rise above rated limits, without a constant voltage limiter!

If this happens then the battery rapidly becomes warm, potentially starting a fire.

As much as you may think you know, you apparently do not know anything about battery safety.

[Kiriakos GR]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

Thanks for the multiple warnings, now pay the proper attention to the post #16.
And as last info I will add that this battery setup does not even get warm, and actually the batteries stays frozen all the time, something that does not happen when my mobile phone charges it 3.7V battery with 300mA or more.
That makes a 900mA battery to be ready in a hour time.

Back to class for a Math lesson: 300mA for a single cell VS 240mA for two Cells.
All the bets goes that my phone will explode first !! LOL

[modemhead]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

So it is safe to use 7.2V (3.6 x 2) from Li-ion?

The front end of the power supply in this meter is a constant-current source. Despite its simplicity, it is safe and effective for trickle charging NiCd cells in the 1200mAh to 1800mAh range. A healthy 4.8V pack will develop a voltage generally between 4.8 to 5.6V depending on its state of charge. This voltage is used as the sole means to regulate the difference between the meter's -5V DC rail and its -10V rail.

Operation outside these parameters is therefore, in a phrase, not recommended.

[tom66]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

A lithium ion cell has VERY low resistance. Measured in single or double digit milliohms. From a 1000mAh 3S battery, you can easily jump-start a decently sized car; that's more than 150A for half a second. (My dad always carries one around with him now in the car; a great jump-starter when you're in a pinch.)

You sound like you do not understand lithium ion cells, so I invite you to research before you either a) destroy a nice meter due to a battery fire, or b) destroy everything you might own due to a battery fire, or c) kill yourself in a battery fire.

Some popular results for "lipo fire" (on rcgroups, a popular forum using a lot of lipos.)
https://www.google.co.uk/search?q=li...K4bR0QW_64DQCg

[Kiriakos GR]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

In the specific charging circuitry the inner resistance of the batteries works as balancing point, lithium polymer does not have the same resistance with NiCD and this difference triggers the overcharge safety.

Regarding luck, three days now, no Boom. LOL

[tom66]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

Even 0.1C is too much to charge without a voltage limit!

Maybe it won't burn, maybe you'll be lucky (maybe not), but you REALLY need to be careful around them.

[Kiriakos GR]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

Even by considering the safeguard limits of 1C
the battery A=1200mA / 120mA & B=900mA / 90mA
A+B= 120 + 90 = 210mA the safe limits are reached and I will not see any explosion.

The lithium ion at fast charge they go up to 3C or 4C which this FLUKE charging circuitry is unable to deliver such current.

[tom66]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

A lithium ion battery (same for lithium polymer) is based on an extremely unstable chemistry. You must treat the battery -very- carefully. If you do not, the best case is you destroy it so it won't take a charge. Worst, sadly most common case is fire/smoke/explosion.

Essentially you must charge at a constant (or varying, but limited) current not exceeding 1C (for most cells) to about 4.2V. (If the battery starts below 2.7V, then charging at more than 0.05C is not recommended, until the 2.7V threshold is exceeded.) At the ~4.2V point (tolerance +/-0.025V), the charge circuit must switch to constant voltage with current limited to previous rate. When the current drops to around 1/5th to 1/20th the start current, the battery is fully charged. During discharge, the battery should not be continuously discharged below 2.7V for any extended period of time; doing so damages the battery.

The over-voltage circuit cuts off the charging typically above 4.4V for most batteries; however, this is merely the point of self-destruct of the battery. The under-voltage circuit will handle below about 2.2~2.5V. Going above 4.3V generally ruins a lithium ion battery, as does going below 2.7V for more than a few hours.

You can get ICs which do this charging all in one and require just 5V input and two ceramic capacitors for up to 500mA charge rate. If you want an easy to charge battery, you must use NiMH or NiCd. You cannot use lithium ion, or you will start a fire/explosion.

[Kiriakos GR]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

So it is safe to use 7.2V (3.6 x 2) from Li-ion?

Yes I believe that it is, the meter use to charge even NiCD up to 6.3V = Bat A+B
The Li-ion that I have are used ones, by pulling the AC cord, the battery voltage even as fully charged drops down to 6.66V with the load of 135mA.

The interesting part is the charging.
Those modern Li-ion are capable for slow and fast charge, and I am not worrying about the 240mA max as charging current.

Even so the 2.4V battery it can not get higher than 3.2V & the 3.6V battery is unable get higher than 4.5V.
When both batteries are close to be considered as fully charged the charging current is up to 200mA, suddenly the current drops down to zero, and the voltage of the A+B batteries reads as 15V.


The 8050A with out batteries connected at those pins there is a voltage reading as 30V.
The explanation is that the charging are made by pulses at 200Hz.

While this setup is safe but not easily replicable by others, at list I gained some time until to find a more suitable solution, that looks to be those 2400mA NiCD.

[tom66]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

Uhh... yeah. Don't charge lithium ion that way. The protection circuit is NOT to be relied upon. It is supposed to limit the chance of damage to the battery if the charger were to fail; it is supposed to be used once or twice maybe and not to be relied upon continuously. It will not necessary prevent thermal meltdown on every charge cycle.

You can buy li-ion charging kits based around MCP1630 or similar, which will happily charge single cells, for more cells, you can use advanced ICs or switch to NiMH which CAN be charged at a low current with only a resistor.

[budm]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

So it is safe to use 7.2V (3.6 x 2) from Li-ion?

[modemhead]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

Just for reference, here is how the original pair of 2.4V packs (4.8V total) are connected.

[Kiriakos GR]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

I made a step to the future regarding batteries type.

While the meter uses 130 - 140mA at normal operation, at charging is capable for 200 - 240mA ( measured by Fluke 28II).
Which is very acceptable for those lithium-ion which have also internal over voltage protection.
I added also a 500mA mini fuse just in case! ( multiple insurance against bad luck). LOL

I did test this setup for two days, I can almost sign an warranty paper that this setup is truly capable even for 9 hours operation.

[Kiriakos GR]

Re: FLUKE 8050A searching adjusting tip to set DC at 0000

Thanks for the info!

In my first quick test, just to see if it powers up I did use NiMH in the one pair of the two.
I am aware that the charging voltage in NiCD are higher, and this would kill any NiMH which are unable to reach more than 1.44V as topped up.

The NiCD can handle 1.5 to 1.6V per cell with out a problem.

What looks interesting is the fact that even by using a lower rated 250 mA NiCD from a cordless phone, the overnight charging it killed it.

I will totally agree with you about the use of NiCD as must do .. and I will add that it must be also at the specified mA rating, or else the charging process will kill them.

Regarding the cost of those batteries, I have many friends (carpenters) and I will salvage some good cells from their dead power packs of their cordless screwdrivers. ;-)