When needing a battery pack to power my first QRP Radio I bought a “model aircraft” 11.1v battery pack, this one from amazon
As far as i can tell it is not fused internally or has any sort of protection circuit. Ive not taken it apart to check (maybe i should !) but does not mention it the amazon blurb.
I fused the plug lead from battery connectors to radio. But potentially I am carrying around an unfused LiPo in the damp, cold, wet, rocky mountains. aka… a potential explosion if i’m extremely unlucky…
I’ve built allot of lights for underground use in the past, using lithium Ion cells and i have always used cell level fusing, as well as protection circuits. Especially as these packs sit on the back of my head. I see BMS being used in other recent threads; wombling and here:
Maybe i should build a Li-ion battery pack with fused cells and a BMS. Am I overly concerned ? What does everyone else do to protect their radios and maybe their backs…
LiPO batteries are as you say, are generally supplied without a battery management system. You can add one of these externally, especially if you intend to use multiple packs. Adding a fuse in the circuit is certainly recommended as should the output be shorted by accident you will be looking at a VERY high current travelling through the circuit. Enough to melt the insulation on the wires and indeed start a fire. This is true of any Lithium battery technology. Consider what happens to a Lead Acid battery in a car if the terminals are shorted - it’s the same with the much physically smaller Lithium batteries.
The more modern LifePO4 packs, often come with BMS and fusing built inside. These are more suiatble for ham radio use both from a safety and a voltage output point of view. They used to be 3 or 4 times more expensive than LiPO for the same capacity but of late the prices have fallen considerably.
LiPOs in themselves are not dangerous unless they are abused in use. Over time the packs can expand with internal gasses and a battery in this state of any form (it can happen also to LiFePO4 batteries) should NOT be taken apart or punctured in any way as that is a VERY dangerous action.
The Li-Ion technology is what has been used for some time in Laptop batteries and again, if mistreated these can burst into flames.
In all cases if Lithium batteries are used with care. Not discharged at a higher rate than specified or charged too quickly.
I wouldn’t be concerned when carry it as you are there to take action if it does catch fire. It is unattended charging or storage where the risk is higher. I don’t think damp is an issue, the fire risk is from internal changes within the battery which can cause a short. Putting it securely in an external pocket would be safest with Lipo.
LiFePo4 batteries are much safer but sadly the 4S ones you need are unobtainium at the moment in the UK. However, I ordered two 2S Zippy ones from HobbyKing last week which I will run in series.
Agreeing with what John says above and adding to it - there are “fireproof” bags that can be bought to put Lithium batteries in during transport and indeed some people prefer to charge the battery inside such a bag.
LiPO batteries need to have each of the internal cells charged to the same level - hence the extra charging lead and the need for a special charger. LifePO4 batteries with a built in BMS usually only have the two power leads coming out of them and these can be used to charge the battery from a regulated power supply of the required voltage, however they can also be charged with a similar charger to the one needed for LiPO batteries and by doing this you gain an indication of state of charge and when the battery is fully charged.
Very useful. Thank you. Especially info on LifePO4, haven’t considered this. Essentially for Lipo what i understand from above is “look after them: store and charge correctly” and you should be fine.
And then you are left with the hopefully never to happen what ifs (or unintentional abuse). Like a cable gets yanked out of its connector and shorts.
Maybe I should be asking if anyone has had a lithium battery ‘incident’ on the hill or at home ? That would be interesting if anyone has ….
Lifepo4 are good, they will (or should!) last much longer than LiPo but you will probably need to buy a new charger as their voltages profiles for optimum charging are different. The larger batteries have internal BMS but the smaller batteries use chargers which connect to each cell individually.
LiPo cells are pretty safe in general : most problems occur from
Incorrect charging
Short circuiting
User modification or “repair” of packs by non-experts
Catastrophic crash damage to models (planes, drones or cars)
Over discharging kills the pack but isn’t a safety issue as far as I know.
Yes they should always be fused as near the pack as possible. I like to use a polyfuse, as they self reset.
However, and it’s a big however, the voltage profile doesn’t particularly suit radio needs. 3S go too low voltage as they discharge and 4S go too high when full. LiFePO4 are better in this respect (4S is ideal) but they are heavier.
I think my next heavy duty pack will be a LiFePO4 built from individual cells with a BMS. I fancy 32700 size 6AH cells, should come out about 600g weight.
I had a google on 32700’s and it looks a good option for an everyday go to battery pack. I may try put one together.
Maybe not the smallest, lightest or highest energy density you might want when its important, on a “need to be lightweight” trip such as Knoydart. Prehaps here i may have to opt for a protected lipo or lion with much lower capacity i guess.
I note some sellers on aliexpress claiming outrageous physics defying capacities of 32700…… 19.9ah cell in 140g …….
Li-Ion Technology is really dangerous if it is not threated properly.
Li-Ion batteries when overloaded will start developing heat (even if not connected any more). At about 70c they usually explode, generating fire…
So carefully with it.
LiFePo4 is probably a much better option from this perspective…
I’ve been using LiPO batteries since 2009 and have never had any issues with them. Three of the four original 3S 4AH batteries are still in use and will power my 817 for a couple of activations and more. I do ensure that the batteries are padded when carrying them in my backpack and each battery is fused about two inches from where the leads exit the pack. This allows some flexibility in the leads. I terminate the leads with powerpole connectors to ensure I don’t have polarity issues when connecting to the kit.
I also use 4S 4.2AH LiFePO4 batteries, occasionally to power a rig, but more often a small linear. I adopt the same principles of care as for my LiPO batteries, though these are potentially less dangerous.The big advantages of LiFePO4 cells are that they can’t go into thermal runaway…They typically can handle 3 times as many charge cycles. Their discharge voltage curve is very flat which allows them to keep supplying nearly the same voltage and power over most of their state of charge. In my opinion, this makes them ideal for powering a small linear, though.I still need to keep an eye on them to make sure they don’t go much beyond the flat section of the discharge curve.
Both types of battery are charged using an iMax B6AC charger (beware of fakes) which I use with an adaptor lead to convert from the 4mm sockets on the charger to the powerpoles on the batteries. I tend to charge both types of battery at no more than 1.5A which takes a while, but has proved to help with longevity. I did have one brain fade moment when I disconnected the battery from the charger by taking out the 4mm plugs from the charger. The plugs touched with a resulting spark and a surprisingly loud bang. I haven’t done that since, taking care to disconnect at the powerpoles.
I constructed a container to combine 4 of the 4.2AH LiFePO4 packs, primarily for use in the Trans-Atlantic S2S events, but have found it to be overkill. Having 16.8AH was useful when I ran a FT-857D, but now with the KX3 plus linear I now just take a couple of the LiFePO4s which last me 4 or 5 hours. The KX3 is run on a couple of LiPOs as I only need 3 watts out to drive the linear to around 30 watts output.
And to think… I used to carry a 12AH SLAB up the hills. And aluminium poles!
I’ve used LiPos for years and had no issues really. I generally try to run a fuse if I can, 1amp for my Morse code rigs and 3amp for the less efficient SSB rigs. Interestingly I was testing my home brew QRP amplifier a little while ago and I connected the leads with incorrect polarity to a LiFePO4 battery, oops! The fuse blew instantly. Guess what - my amplifier survived and works without issue after I replaced the fuse.
As an aside, I’ve had two batteries fail, and they were both LiFePO4 types. I managed to re-engineer one of the LiFePO4 by taking out the dead cells. It’s now a 4S3P instead of 4S4P!
Well this thread put the mockers on one of my LiFePO4 batteries yesterday. I was using it to power my IC-703 on the bench. It started off fully charged and was well within its capacity an hour or so later with just three quick SOTA chases in the log. I went out of the shack to get myself a bite to eat and when I came back an hour later, I found that the rig was off and giving an occasional click. I looked at the battery and noted it had swelled up.
Taking a reading of the cell voltages, I found both cells 2 and 4 to be well below the 2.5V cut-off voltage. Of course my charger wouldn’t touch it and so I had no method of recovering it. I did consider attempting to recover the two good cells, but decided against it. I’ve enough hassle going on in my life at the moment, one way or another and dissecting a lithium battery is something I don’t need. One for the recycle bin.
I’m also going with LiPo batteries, mainly because they are the lightest I found so far.
Those are the batteries I have around:
Brand
Type
Voltage
Capacity mAh
Capacity Wh
Weight
Ratio g/Wh
Turnigy
LiPo
14,8
1000
14,8
103
7,0
Turnigy
LiPo
11,1
1500
16,65
120
7,2
Zop
LiPo
11,1
4000
44,4
325
7,3
Eremit
LiFePo4
12,8
6000
76,8
630
8,2
I use the 120g 3S turnigy for my activations. Regarding safety, I don’t really see how a short could happen in my backpack since they are equiped with powerpole connectors …
I agree, Its confirms what i understood from using lights underground. Li-ion is the best choice for energy to weight, even after you have fused each cell and added a BMS.
