Question: Replacing Lithium-Ion battery pack with a lead acid battery?

[Bicurico]

Hi,

I have purchased yet another field meter (Emitor Megalook). Actually I purchased a pack of two.

One has a completely drained battery, the other's battery works for about half an hour when fully loaded, instead of the expected 3 hours.

I own a few other field meter from Emitor and the older ones like the Satlook Digital NIT (which uses the same main PCB's for CRT, frontend and SAT as the Megalook) use 12V lead acid batteries.

The Megalook has a Li-Ion pack composed of 3x4 cells, so I assume it is 12x 1.2V = 14.4V.

The included charger is rated 13.8V, but there is a simple cigarrete-style plug for in car charging included, which obviously only runs on 12V. Also, I tried the 12V charger from the Satlook Digital NIT and it worked just the same.

After all these considerations, how feasible would it be to replace the Li-Ion pack with a 12V lead acid battery?

The reasons are simple:

1) The field meter has enough space by design to host such a battery.
2) I can go to a closeby store and purchase a 12V lead acid battery for 10-20 Euro, which is MUCH cheaper than any Li-Ion battery pack, even self-made (if I had the machine for it).
3) The weight doesn't bother me - the device is bulky and heavy as it is, so even half a kg more doesn't make a difference.
4) A similar Li-Ion pack is hard to come by and the ones I have found wouldn't fit due to different arrangement of the cells.

My main concern is the charging cycle: is it the same for both Li-Ion and lead acid batteries? A quick Google search got me with the idea that lead acid batteries can just be replaced with Li-Ion ones, maintaining the charging cycles. Should work the other way around, I figure...

Before I spend money and potentially set anything on fire, I would like some opinions, first.

Regards,
Vitor

[Armadillo]

Just my 2 cents opinion;

The charging methods and the termination charge detection are different. Furthermore lead acid is not well suited to all directional portable. Acid mist invites corrosion to your precious circuit.

Buy branded li-ion battery with integral protection circuit would be the way to go. Buy OEM recommended battery.

If the OEM trusted it and passed through all kind of safety standard house testing, why would you doubt it.?

[vealmike]

Li-ion chargers and Lead acid chargers are different.

Li-ion chargers have three phases.
Stage 1. If terminal voltage below fully discharged level (typically 2.7V for Li-ion Cobalt) then charge at a reduced constant current rate to reduce outgassing during charging. Usually C/10 to c/4. This stage should have a safety timer.

Stage 2. If terminal voltage above fully discharged level, but below fully charged level, charge at a constant current. Usually C.
Stage 3. If terminal voltage equals fully charged voltage then charge at a constant voltage (equal to fully charged voltage). Terminate charge when charge current falls below a predetermined threshold, typically 1/10th of the stage 2 constant current.

Stages 2 & 3 share a safety timer.

Lead Acid batteries may be charged with a current limited constant voltage source, which is actually what you get from stages 2&3 of the Li-ion charger.

In conclusion, it should work, but with the following caveats:
  * Lead acid fully charged voltage must be equal to or greater than the Li-ion pack it replaces (or the lead acid will overcharge and gas).
  * If the lead acid pack takes too long to charge, then the Li-ion charger may timeout and have a hissy fit.
  * You shouldn't charge the Lead acid too fast, it will gas.

Don't lead your lead acid gas, especially in a confined enclosure. The gas is quite explosive!

[Bicurico]

Thanks for your reply.

I don't image that Emitor actually changed the charging circuit between their models. The main PCB looks far too similar. But then, I did not fully disassemble both devises for a 1:1 comparison.

Interestingly, even the older Emitor Satlook Digital NIT will display "STD" on the LCD screen during charging, but I have seen "FAST", too. Perhaps the circuit does detect stages based on the remaining battery voltage?

And yes, the Emitor devices do have a timer while charging. I think they measure time and voltage - at least they do display both on the LCD screen.

Not sure if I should try it out. Is there a way to see if gas is leaking? What would be the signs?

Regards,
Vitor

[Bicurico]

Just my 2 cents opinion;

The charging methods and the termination charge detection are different. Furthermore lead acid is not well suited to all directional portable. Acid mist invites corrosion to your precious circuit.

Buy branded li-ion battery with integral protection circuit would be the way to go. Buy OEM recommended battery.

If the OEM trusted it and passed through all kind of safety standard house testing, why would you doubt it.?

Sorry, I did not notice your reply before my last response.

I understand your questions, but the answer is simple:

1) The device is no longer supported by the manufacturer.
2) The battery is no longer being sold by the manufacturer's resellers.
3) Similar batteries for newer models of this manufacturer, with less capacity, are being sold at 169 Euro. This price is not compatible with my amateur usage.
4) The Megalook is an evolution of the Combolook and Satlook devices, which were using SLA batteries (12V). Most of the layout of the Megalook is exactly the same as the predecessors. I doubt that Emitor would have changed the whole charging circuit. I think they rather changed to Li-Ion because of the charging compatibility. Otherwise, why didn't they go for NiMH batteries, like all other field meter manufacturer have done?

But, no offense meant - I am the one with doubts!

Regards,
Vitor

[Gyro]

It really depends how 'primitive' the existing charger is. If it actually just puts out 13.8V (please verify!) with some degree of current limiting then it is the ideal voltage for float charging a 12V SLA (indefinitely) at room temperature or lower.

If the charger is more intelligent, with timeouts etc. then it won't work so well in fully charging the battery. If its maximum output voltage is 13.8V though, it's hard to see how it could damage a SLA, apart from long term undercharge.

[Armadillo]

Sorry, I did not notice your reply before my last response.

I understand your questions, but the answer is simple:

1) The device is no longer supported by the manufacturer.
2) The battery is no longer being sold by the manufacturer's resellers.
3) Similar batteries for newer models of this manufacturer, with less capacity, are being sold at 169 Euro. This price is not compatible with my amateur usage.
4) The Megalook is an evolution of the Combolook and Satlook devices, which were using SLA batteries (12V). Most of the layout of the Megalook is exactly the same as the predecessors. I doubt that Emitor would have changed the whole charging circuit. I think they rather changed to Li-Ion because of the charging compatibility. Otherwise, why didn't they go for NiMH batteries, like all other field meter manufacturer have done?

But, no offense meant - I am the one with doubts!

Regards,
Vitor

The charging and termination detection is definitely not compatible of the two types of battery, no need to doubt about it. It may seems to work for you, but either the performance or the life cycle will be affected by it definitely. Take a look at automobile lead acid battery at the terminals, you may see white powdery stuff.
The KVA rating of the Li-ion is better than NiMH. 169 Euro is way crazy price. Can you picture the OEM battery so that we understand how come is would cost so crazy LOL.
Some here may be able to recommend you the modern Li-ion that fits the board at down to earth price.

[Bicurico]

This one isn't even the right battery: http://emitor.de/akku/98/akku-fuer-satlook-und-combolook-messgeraete-2x6-6-14-8v-16-8v-6-6ah

It is in a 2x6 arrangement, the one I have is in a 3x4 arrangement.

My battery pack doesn't have ANY sticker on it, so no specs at all. The device it self has a serial number sticker where it says "LiPo battery".

From the manual:

"MEGALOOK is equipped with a rechargeable battery and it is important that the battery is maintained in a proper way.
Recharging should be done with the enclosed car-adaptor (12V) or the power supply (220V/13.5V, 1.7A)."

"If the battery needs recharging, use the enclosed power supply (220V/13.5V). When the recharging starts, a thermometerscale
indicating the capacity of the battery (0-100%) is shown on the LCD-display.

Note! The instrument shall be turned off when being recharged.

Recharging a fully discharged battery to about 98% of its capacity takes aproximately 30 hours."

I think the last line is bullshit and comes from copy&paste of manuals from devices using SLA batteries.

Interestingly, the manual says that the device was not build for permanent use with power adapter and that it should be used only for short periods like this. I think that this is because the charging circuit is not running while the field meter is being used.

I think that the Megalook doesn't have any sofisticated charging circuit, which is why the power adapter is 13.5V. If you connect it, it will start charging the battery, monitoring the voltage. My guess is that the charging ends when 16.6V are reached (from observing the cycle on the still usable battery). I wonder if it would be safer for the device, if I removed the battery at all and run in with a 12V power adapter.

None of this is critical to me, I just like to maintain all functionality in working order on my field meter collection.

Regards,
Vitor

[Armadillo]

It looks like 18650 binded together, man you can build it yourself.
Of course you cannot run it on adapter, because of the sudden current draw which will far exceed the adapter capacity which is supposed to be used for charging only. Which means if you didn't install any battery and just power it up from the adapter, I don't think the circuit will operate properly.
Lead acid battery terminal voltage is 13.6volts at max so it cannot be a lead acid battery at 16.6volts, never.
Since you observed higher than charger voltage, it means there are boost circuit inside the charger.
Its easy to build up using the 18650s.

Edit: check the sizes https://en.wikipedia.org/wiki/List_of_battery_sizes

[IanMacdonald]

Basically, a lithium charger will take the voltage to 4.2v per cell. Thus if the original is 3 in series  it will go to 12.6v, if 4 in series, 16.8v

For a 6-cell sealed lead acid, 12.6v is too low for adequate charging, but 16.8v is way too high and will damage it. It needs a regulated 13.8v charging supply.

Another difference is that a lead acid charger 'floats' the battery at constant voltage when fully charged, but a (decent) lithium charger cuts the current off when 4.2 per cell is reached. (Some of the cheap ones do not, though)  Floating for a reasonable time, say 24h, is good for lead acid but bad for lithium.

Thus I think you need to firstly determine whether it runs on 3-cell or 4-cell voltage.

On discharge, the output voltage will be nominally 3.7v per cell. or 11.1v for 3 cells, 14.2v for four.  A SLA gives 12.6v when fresh, down to around 11v when flat. Thus its output will be a tad low for the 4-cell setup, a tad high if it was 3-cell.

You could do some tests if you have a regulated variable PSU, to see what voltage range the instrument will operate satisfactorily from. If it will not operate satisfactorily from the lead acid output range of about 12.6v down to 11v, then it's a tougher proposition than if it will. If it will, then you only need to sort out a charging arrangement.

HTH.

[Bicurico]

Hi,

You guys convinced me and I gave up on the idea of using a SLA battery.

I will consider building a battery pack myself, however that requires a spot soldering machine, which I don't have at the moment. I need to work on the HWAF to be able to afford one...

I think indeed that the pack of the Emitor Megalook is a Lithium-Ion battery composed of 12 cells, almost certainly 18650 ones, in a 3x4 arrangement (4 cells in series, each series in parallel).

These cells are normally specified with 3.7V at 2x00mAh.

4 in series: 14.8V
3 times 4 in parallel: around 7000mAh

This makes sense, according to the manual.

Charging this pack should be done at 4.2V x 4 = 16.8V, which again is compatible with the LCD display of the Megalook.

Finally, the www.emitor.de site I linked above, selling a similar pack for 169 Euro, mentions a 20 Euro cash-back if you send in the old battery pack.

I believe they to that, because the pack has a protection circuit, which they recover.

So I guess I need:

1x spot solder machine = around 150 Euro
12x 18650 cell (saw some at 5 Euro a piece) = 60 Euro

Not cheap, but the machine would be used for other battery packs.

Any flaw in my reasoning? I did not open the battery pack of the Megalook to look inside, as this would deminuish the reselling value of the device - I will open it only when I am ready to replace the cells.

Regards,
Vitor

[Armadillo]

You will need "Nickel Strips" to join up the battery, and solder it will do. There are Youtube video on how to make the battery pack and soldering.
Don't need to invest on Spot Welding machine.
It will work just fine.
Also buy heat shrinkable tube wide enough for the pack otherwise tape it will do, but appearance wise, heat shrinkable looks more professional.
How come your 18650 so expensive. Buy from china, it will work just fine and since you are collector.
The seller will also sell those with integral protection but size is longer. Check it.
Personally I feel integral type has current limit, I don't like it but its fire protection safe.
you can communicate with Seller to bind up the pack for you and save the trouble [maybe]
Next is the connector which you will also need to define.

[Armadillo]

Charging this pack should be done at 4.2V x 4 = 16.8V, which again is compatible with the LCD display of the Megalook.

This statement is potentially not precise and may pose some form of risks, so I ought to correct it.

Li-ion is charged by using constant current so you cannot use a constant voltage of 16.8v and putting it across the battery to charge it.
After it's charged, the gang will exhibit 16.8V.

[Bicurico]

You are right. Thank you for your correction.

I am not in hurry, so I will study this subject a bit more.

Some tome ago I created this thread: https://www.eevblog.com/forum/beginners/how-to-build-a-battery-pack/msg1267999/#msg1267999

I am considering for a while to start building my own battery packs. In the past I tried to solder them, but without nickel strips. It was a big fail.

Getting a fully made pack from China seems an intersting option, but I don't have any contact. Do you have a seller that build custom battery packs?

I guess I would have to open the existing one to confirm the cell type and see if or what kind of protection PCB is present.

Regards,
Vitor

[SMdude]

Look for cells that come "with solder tabs"
Try and source from a reputable seller and don't bother with batteries that claim big capacity and have "fire" in the name.
About the largest reputable 18650 cells you will get are the panasonic ncr18650b.

As for getting packs made, most sellers don't want to know about it unless you are purchasing 500 cells or more, though you might be able to find someone to do one off's at an elevated price.

[Bicurico]

Hi,

Hopefully the last question. I now seem to understand how these packs are build and named.

What I seem to have is a 18650 4S3P pack with 14.8V and 6Ah, meaning that 12 cells are grouped as 4 in series and each of the 3 series are connected in parallel.

Looking at Alibaba/Aliexpress, I seem to find 4S2P packs at affordable prices. They are specified from 4Ah to 5.8Ah. My question is: does it make any difference, in terms of charging or usage, to have a 4S3P array or 4S2P? Of course, with less Ah, the device will operate less time - but that would not be an issue: 2.5h or 3h operation doesn't matter to me. It seems that the difference in the array would simply be less total capacity. Does having less cells (8 instead of 12) cause any issue with the charging circuit?

Regards,
Vitor

[Armadillo]

With that capacity of the power adapter, NO, it will not affect the charger or adapter.
I think you should follow the 4 series and 3 parallel bank, why save a few dollars, its already cheaper than your euro.
Don't go for cheap, go for reliable with alot people leaving good positive comments.

[Bicurico]

Again, the struggle is that it comes far more expensive that I had planned.

The prices for a single 18650 cell with tabs is around 5 Euro. I need 12 of then, so that alone is 60 Euro. Plus shipping. And then I am still lacking the heat shrink wrap, connector, etc.

For 50 Euro I get a fully assempled 4S2P pack with almost he same capacity, hence my question.

The issue with going cheap or expensive: these are collection devices. I may used them occasionally, but mainly I just want to preserve them in working condition. And spending a significant percentage of the device's purchase price on batteries, just doesn't equate. For my needs, I can just use the device plugged in with no battery at all. It is just that it bothers me, not having it in prestine state.

I saw some 18650 cells being sold at 2 Euro/each, but they don't have the solder tab and carry "fire" in the name... I now know I should avoid them.

This whole thread was started, because I had the hope that I could just go for a SLA battery which would cost me around 10 Euro - that would no doubt be a nice price! By the way: could it be that the charging circuit simply has like a potentiometer or so, where Emitor adjusts the charging current? Like 12V for SLA and 14V for Li-Ion? I am pretty sure that some Megalook devices were sold with SLA batteries.

Again, sorry to insist on this and thank you for all replies so far. I have learned a lot about batteries through this thread!

Regards,
Vitor

[Armadillo]

I think you should try power it up with a 12v battery first and if it operate properly with 12v then you decide.

[Armadillo]

If the size can fit, maybe this will meet your budget. [For collector purpose]

[SMdude]

Again, the struggle is that it comes far more expensive that I had planned.

The prices for a single 18650 cell with tabs is around 5 Euro. I need 12 of then, so that alone is 60 Euro. Plus shipping. And then I am still lacking the heat shrink wrap, connector, etc.

For 50 Euro I get a fully assempled 4S2P pack with almost he same capacity, hence my question.

The issue with going cheap or expensive: these are collection devices. I may used them occasionally, but mainly I just want to preserve them in working condition. And spending a significant percentage of the device's purchase price on batteries, just doesn't equate. For my needs, I can just use the device plugged in with no battery at all. It is just that it bothers me, not having it in prestine state.

I saw some 18650 cells being sold at 2 Euro/each, but they don't have the solder tab and carry "fire" in the name... I now know I should avoid them.

This whole thread was started, because I had the hope that I could just go for a SLA battery which would cost me around 10 Euro - that would no doubt be a nice price! By the way: could it be that the charging circuit simply has like a potentiometer or so, where Emitor adjusts the charging current? Like 12V for SLA and 14V for Li-Ion? I am pretty sure that some Megalook devices were sold with SLA batteries.

Again, sorry to insist on this and thank you for all replies so far. I have learned a lot about batteries through this thread!

Regards,
Vitor

If it bothers you not having it in pristine state, a lead acid battery just won't cut it!

The Aliexpress packs you mention, if they have less capacity, they will still work fine.
Whatever you use, make sure it has the protection circuit built into the pack otherwise it is too easy to over-discharge the pack and ruin it. Also if something else goes wrong, there will be smoke and fire, lots of it

If you don't want to spend the money, then just leave well enough alone, otherwise down the track you will regret it.
You can recycle 18650 cells from old laptop batteries, but buy the time you decommission them they are normally cactus anyway.
The blue shrink wrap can be purchased off ebay for next to nothing.

Cheers

[A@ron]

Do you have a picture of the current Li-ion battery. I'm wondering if it has an integrated BMS or if it has leads for pos, neg and also balance wires on a harness.