Li-ion batteries and electronics question.

[Marc N]

Some of you may remember, when I set up my Kayak, I was after the cheapest possible option for everything. This included buying my Yak, which I find, is just a little low in the water for my 112Kgs. So in an attempt to raise the water line I'm stripping weight from my setup.

I remember a question or post, from some time ago, about using Li-ion batteries from power tools etc, to power fish finders etc.

So I found a lot of these recycled 18650 Li-ion batteries on Trademe, that are the recycled good ones, from dead power tool battery packs, tested and working and - wait for it - cheap!

I've previously repacked two laptop battery packs, with these and they work just fine.

So I got some more, to solder together, to make a pack, for my fish finder. Using a weighing machine I found that I'd save about 2.5Kg if I used these, and not my current (geddit?) lead acid battery

I'd completed the soldering and then I put the battery charger on the pack and the needle shot off to the right, > 7 Amps, a dramatic orange glow started to come from the inside of the charger. I quickly disconnected everything to prevent fire, danger, or a fission event.

I am hesitant to plug in my expensive fish finder to see if it works.

Then I got to thinking.

When I repacked the laptop battery packs, there was a little circuit board in them, that I assumed, did a bunch of things including, perhaps - provide some resistance in the circuit.

My 12 V battery charger is one of the old ones - transformer, plug, clips, needle/meter, switch, nothing in the way of electronics. Do I need to provide some resistance in the circuit with these 18650 cells ?

It may be that my fish finder will have the necessaries to do this, if I connect it straight to the battery pack.

But then how to recharge? I am hoping that someone here will be able to give me advice on this.

Some specs ::

18650 Cell Features and Technical Specifications
Nominal Voltage: 3.6V.
Nominal Capacity: 2,850 mAh.
Minimum Discharge Voltage: 3V.
Maximum Discharge current: 1C.

Garmin Striker plus 7sv specifications
Transmission power: 500W (RMS)
Voltage range: 10 V to 28 V input voltage.

See diag. below for the arrangement I made.

batteries.jpg (73.24 KiB) Viewed 3432 times

Any and all advice appreciated

[Waylander]

https://www.jaycar.co.nz/spare-12v-3ah- ... 7/p/CS2498

Although I can appreciate the DIY....

Light, cheap, easy to charge and probably more than enough power- with out the risk of blowing things up.

Just a thought.

[Marc N]

Thanks Waylander, yes that's what I'm using now, only a 2.5Kg one.

Part of this is I need to know the answer to the resistance for the 18650 cells question, I'm a bit OCDC so the question is bugging me

I will be using my current - battery until I solve the 18650 question

[Marc N]

Belay that, I'm an idiot.

I put on two pairs of close-up reading glasses and re-examined my soldering work.

Underneath one of the connecting wires, on the +ive terminal of one of the cells, a stray piece of solder had melted through the cell's plastic covering and allowed the +ive terminal to be connected to the -ive metal casing of the cell, i.e. a short circuit.

After I remedied that, everything works as desired. Shit hot !

[Mac50L]

Usually with Lithium batteries the charger is critical. It certainly is with LiPo batteries and each cell is monitored while charging and each cell topped off so that the maximum voltage never exceeds the critical voltage (4.2 volts).

https://learn.adafruit.com/li-ion-and-l ... s/voltages

LiPo
Absolute maximum voltage 4.2 volts
Absolute minimum voltage 3.0 volts
Nominal voltage 3.7 volts

Li-Ion
Nominal voltage 3.6 volts

Battery types and voltages
https://batteryuniversity.com/learn/art ... h_voltages

[Marc N]

Thanks Mac - I'm test charging the pack now.

It showed 14.7 volts when 1st connected to the fish finder, I ran it on simulator for 3 hours and it got to down to 9 volts.

The charger is a dinosaur 12 volt one and the pack seems to be taking a charge, I'm monitoring it so see that it doesn't get hot, so I'm hopeful
It's taking 1.5 amps at the moment, similar to what I see in a Lead Acid battery.

[Mac50L]

the problem with a charger that is connected across the battery is that individual cells can be forced over their maximum critical voltage though the voltage across the whole pack might be OK. This is why a "proper" Li charge is so complicated. Despite this they can be relatively cheap. Note "relatively"....

Model aircraft suppliers handle such items. HobbyKing, possibly Banggood, AliExpress etc. if you want to import directly. One of mine was less than $30 and runs off a 12 volt supply and able to charge up to a 22 volt battery set, 6 cell LiPo. It will also charge NiMH/NiCad and lead acid.

More details if you want them.

[Marc N]

Thanks Mac.

I see the technical issues you note, re: the individual cells.

Some of the cells I am using are the 'good' ones from the Laptop battery packs I repacked. In the laptop batterie, I found that 2 of the 6 were defunct the other 4 were OK, so I've re-used them.

Well, I ran the fishyfinder on Simulator all day, connected to the Li-ion pack.

It started out at 16.8 V and after 10 hours it got down to 14.4 V, I expect it to keep going till <10 V

This has exceeded my expectations. It maybe a different story when the transducer is connected and it's pumping out watts, but I reckon it should go for a while, and I'm not likely to be running it for more than about 6 hours on the water.

If this solution turns bad, I may look into the model shop style battery packs you mentioned.

The main reason for all of this is to not load my kayak down too much and a 2.5 Kg battery is a start.

I even shortened my anchor chain by a metre.

And I'm only taking rods I'll actually use

[Mac50L]

Just to point it out? make you unhappy? with me at 70 kg and my kayak about 18 kg, I'm not much worried about weight - sorry (well maybe not

Used batteries and using until totally dud is at least one way of getting the maximum out of them before land-fill - or re-recycling.

[Marc N]

even when I was slim rugby playing and handsome young man, I was always, 90 Kg plus. I put that down to my Viking bloodlines , dense bones

Part of this is to minimise environmental waste, as you point out , but also it appeals to me in terms of not wasting money.

And lastly, I really did have a genuine concern that these might not work if there was no little circuit board or resistor ( like in the laptop battery packs ) so understanding these Li-ion battery packs is the key driver.

I now have two Lead Acid batteries and this new Li-ion pack I made, so I've got spares

I'm not a trained electric fellow, what I've learned about Ohms and Volts and transistors and resistors etc, has been accomplished pretty much by sticking my fingers in things. Over the years I've lost count of how many 240 V shocks I've had, including, across the chest from both arms... Don't like those ones, no. I more careful now

[Mac50L]

even when I was slim rugby playing and handsome young man, I was always, 90 Kg plus. I put that down to my Viking bloodlines , dense bones

I refused to play rugby, always played football. Stand sideways and you wouldn't see me. Scottish origin?

Part of this is to minimise environmental waste, as you point out , but also it appeals to me in terms of not wasting money.

Agreed about the money, Scottish origin.

I'm not a trained electric fellow, what I've learned about Ohms and Volts and transistors and resistors etc, has been accomplished pretty much by sticking my fingers in things. Over the years I've lost count of how many 240 V shocks I've had, including, across the chest from both arms... Don't like those ones, no. I more careful now

A lifetime of electronics and right at the start, "Keep one hand in your pocket." was the instruction. As most "stuff" now runs under 50 volts it is reasonably "safe". The only bite-ty bits are the supplies to provide the low voltage. And they so often need the fixing.

[TwoSpoons]

Your battery pack is a fire hazard. You have no protection circuitry, no cell balancing, mixed cells of unknown capacity ( being used ), you have the pack wired wrong and you tried to used a lead-acid charger.

Protection / balancing : requires a device called a BMS (Battery Management System). This will prevent over charging, over discharging , over current and extend the pack life.

Connection: Should be sets of four cells in parallel, with your four sets connected in series. This helps balance out the individual cell capacities, and you can use a single 4C BMS.

Charger: Must be a Li-Ion charger. The voltages, currents, charging profile and charge termination detection are quite different to lead-acid.

Before constructing your cell pack make sure all cells are fully charged - otherwise the full ones will try to charge the not full ones in an uncontrolled fashion.

It started out at 16.8 V and after 10 hours it got down to 14.4 V, I expect it to keep going till <10 V

Li-Ion cells are empty at ~3V , much below that and they suffer permanent damage, so don't let your pack go under 12V.

[Marc N]

Thanks Mac50.

Twospoons, I see, when this one bites the dust, I'll have a go at the 4 x parallel and then in 4 x series config and get a proper Li-ion battery charger.

[Marc N]

I promise this will be the last from me on this topic.

Yer haff ta larf!

So I went fishing yesterday, got two pannies, so dinner tonight will be good.

When I plugged in the fish finder and the new Li-ion battery pack, there was a faint 'tst!' sound, from somewhere.

No power to the fish finder then. 12 V fuse

This is my last question for those who know, can you get 16v 3A fuses? Or ?

And I won't hold you responsible for the fish finder, as it says it can handle:

Voltage range: 10 V to 28 V input voltage.

The fuse it comes with, is 3A fast blow, is it 12 V? or should I get a 4, 5, 6 A one?

fuse.jpg (1.97 KiB) Viewed 2836 times

The fish finder is running fine with the new battery pack and no fuse, on my desk and has been for a couple of hours.

Off to JayCar me....

[Caveman]

Hek! Been down this road with high output lighting for MTB night riding over the last 25 yrs. 12V gel cells and then Li-ion drill packs running 12V halogens....enter big LED emitters, went back to lead acid gel cells, to hek with the weight, they so simple to charge. Dabbled with LiPo packs from cellphones but needed to split packs back to the original cells to charge safely....balancing, temp monitoring etc.
Your pack is a roman candle waiting to happen. If you must, charge it on a metal shelf or concrete floor well away from anything inflamable (yak?) Certainly not inside your home. Good luck and be careful, there is a lot of chemical energy stored in a battery pack. AND ITS TRYING TO GET OUT, FAST IF IT CAN.
Cheers
B

Sent from my SM-P600 using Tapatalk

[Marc N]

Thanks, and even with my lead acid batteries for the Kayak I charge them when I'm doing something near them so I can watch them, they get hot too.

And hopefully the last update on all of this, I pulled the fuse out and it is testing OK,
so something in the - Ohms = (old man with cold fingers) * (wires n things) / no power - equation needs looking at.

[Mac50L]

This is my last question for those who know, can you get 16v 3A fuses? Or ?

And I won't hold you responsible for the fish finder, as it says it can handle:

Voltage range: 10 V to 28 V input voltage.

The fuse it comes with, is 3A fast blow, is it 12 V? or should I get a 4, 5, 6 A one?

A fuse's voltage rating is via the gap between the ends. If it can't arc over between the metal ends it will be OK over 230 volts.
It is the current rating that is the defining thing. You can't have a too high voltage rating.

[Marc N]

Thanks Mac, as I've said, I don't have much formal knowledge of 'lectrics so that's good to know.

And I've finally, got to the bottom of, the Battery Pack not working in the boat thing.

Using a technique I got from my computer days, a binary search. This or that, 1 or 0, and so on.

So after ascertaining that the battery works, and the F'finder works and the fuse works, I tried it with and without transducer, and it won't work with trandsducer. But it will if the lead acid battery is connected.

There must be something in the transducer that won't play nice, if there's more than 12 v in the circuit. So after all of this, it's back to the lead acid battery for me

So what to do with the Li-ion battery pack?, mmmm... navigation lights, radar...

[TwoSpoons]

Most likely you have a bad cell(s), and the pack can't supply the instantaneous current needed to drive the transducer. With sounders there is likely a large difference between the peak power draw and the average power draw. When the transducer is pinged the power needed could easily be several hundred watts, albeit very briefly. Lead acid can (generally) handle this peak power with no issues, but a weak cell in a Li-Ion pack will cause the output voltage to drop during the high power load, and will probably upset the sounder.

[Marc N]

Thanks TwoSpoons, that make sense.