Dogging, Wombling and free SOTA batteries. (Part 1)

Hi Rick,
That’s a very neat setup for your FT817.
I have an FT818 and I’m interested in doing something similar with the vape batteries I have collected.
Is the voltage output from the battery pack enough for the FT817 to run at full power (5w) ?
The manual for the FT818 states that it will run 6w if the supply voltage is above 12v, I just wondered how long your FT817 runs at 5w before switching down to 2w ?
I currently use a 12v SLAB to power the radio but I’m keen to reduce the weight in my pack for some longer trips planned in the summer.
Andy
MM7MOX

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Hi Andy

The FT-817/818 power settings are much misunderstood, because they made it obscure. If you set the power setting to “blank” rather than any number of bars it will run 5W+ irrespective of the voltage, right down to around 9V where it starts to tail off. When the voltage get below around 11V, the indicator will start blinking, but it is still running 5W.

The behaviour on internal and external power is exactly the same, the indications are only voltage based. The manual assumes the only internal battery is the NiMH that makes 11V at best.

The FT-817 never switches power mode by itself, except on power-up with a low voltage, when it will default to 2.5W.

So in fact you can use the full capacity without the power falling significantly. I get about 1.5 hours activation time on HF SSB. FM uses much more of course.

I ran some tests into a dummy load with my FT-817 a while back to prove this to myself : this should explain :

Power Mode Voltage P-P output RMS PEP
blank 13.8 50 17.68 6.25
blank 12.7 50 17.68 6.25
blank 11.8 48 16.97 5.76
flashing 10.6 48 16.97 5.76
flashing 9.8 47 16.62 5.52
flashing 8.7 45 15.91 5.06
flashing 8.1 40 14.14 4.00

A footnote : the thin battery cables in my FT-817 and their tiny connectors had corroded and were dropping nearly 2V on transmit ! So I rewired with a new connector and thicker cable, soldered onto the main board.

Cheers
Rick

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Hi Rick,
Thank you for the information on the FT817.
I use the SLAB plugged in to the external connector of the FT818 at the moment and will probably do the same with experimental battery packs initially.
I have the FT818 set for 5w at the moment and had seen the display flash from three bars to 2 bars when the SLAB voltage was low on transmit.
I think the main gain will be weight saving, although I will have to invest in a proper charging system for this chemistry.
The extra weight of the SLAB has been useful though on the last two activations for anchoring my pack down in the strong winds !
Andy
MM7MOX

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And I always thought Dogging was the act of using the rope & placed gear to haul past the crux on a climb you were struggling to get up!!!

I’m not entirely sure I’d be happy having batteries of unknown quality in my rucksack or radio. They’ll be the cheapest quality the vape maker can get away with so it’ll be interesting to see how things go. It’s certainly the right approach, re-use before recycling etc.

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What makes you think that batteries you buy are any better quality?

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Either way they are over-designed. The vape fluid in the pad has been used up but the battery retains significant power in nearly every case.

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Nothing scientific or typically QA based with LoCs etc. The ones I use are from the local Radio Control supplier. In the RC cars where they are used they take a real hammering with multiple recharging every weekend. No fires, very occasionally a swelled cell. So it’s a fair extrapolation that they won’t do anything unwelcome powering my radio.

One-shot vape batteries? Different proposition, no rigorous multi-cycle field testing - yet. Though I would not be surprised to find they came from the same factory.

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I went into town the other day to catch up on some errands and made a stop at one of the Vape shops. After explaining to the man behind the counter he walked over to a vertical plastic tube about 6" in diameter and 3ft tall and said “how many do you want”. I got out the ziplock bag I’d cunningly brought with me and he put 22 of the small square ones (360mAh and 2 of the big round ones (1500mAh) in it then asked “is that enough?”

So far they have all tested okay.

I’ve also discovered that you can get 2 of the 360mAh ones side by side in a “Lost Mary” type vape and then use 2 of the bottom caps and you have a nice 8.4v battery pack for running low power accessories (external keyer).

So no Dogging required!

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Yes the fact vape shops take back used ones has reduced the number found. I picked up a bagful from a vape shop when on holiday down in Northumberland last month. I got 6x 13400, 2x 23350 and 2x 21350. I need to make a few packs now I have so many cells.

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Me too. I need some 8.4v packs for running my MTR at slightly lower power to drive my HF Packer and for accessories like the external memory keyer for my 817

Have you worked out if it’s better to put a balance lead on the pack or to use a BMS? Or both? Or neither?

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I have just completed a 6P3S pack of 500mAH cells. I found the balance lead usefull because my charger displays the voltage of each parallel group (eg during and after discharge) and its internal resistance. It also has a “discharge” facility in which I can set the current, and it stops at the safe low voltage point.

All of this together helped me to juggle the weaker / stronger cells between groups to get the best overall capacity.

This nominal 3AH battery delivers about 2.3AH at a steady 0.5A discharge, which is not bad from random wombled cells.

I had intended to go the BMS route, but as I haven’t purchased any yet, I probably won’t bother now.

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My Eremit LiFePO pack has a BMS built in so I don’t worry about over discharge… I run it till the BMS saves the cells or I remember to recharge it. My other LiFePO RC model packs have no BMS so I need to keep an eye on the terminal voltage more. (Can be displayed on both the KX2 and 705).

I do use a LiIon BMS with my “dogging” cells because they are more of an unknown quantity. They do seem to balance out nicely but I did find them laying on the ground so I think using a BMS makes sense. Again the QCX TRXs I use have battery voltage displays but using the BMS means I can forget about the cells.

I use this BMS 3S 20A Balance Li-ion Lithium LiPo BMS Protection Board 12.6V | eBay. My packs only have a balance connector, this is used to charge them and the same connector is used to connect up the cells to the BMS inputs and a flying lead with a 2.1mm coax power plug powers the QCXs.

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Nice implementation, I might just do that. Thanks for the link too…

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HI Andy, I have a balance connector at the moment and have ordered a BMS. I was going to have this as part of the battery pack (they are about 70p on aliexpress)

Have i understood this correctly that you wire a balance connector to the cells and then connect the BMS to the balance connector when charging? Why not permanently wire in the BMS straight to the cells and have this as an integral part of the battery pack, with just a connector to charge and use with rig ?

Tim

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No. My pack has 4 wires coming out of it, GND-----3.7V-----7.4V-----11.1V , and they terminate in a JST-XH connector. That plugs into small LiPo charger that does only 2S or 3S packs. That charger only uses what is normally the balance connector to charge the pack. This is different to many chargers which have a bulk connection to the main battery output and the balance connector.

I then mounted a JST-XH PCB socket onto a piece of Veroboard and glued that to the back of the BMS and wired the JST-XH socket to the corresponding terminals on the BMS. The main B+, B- BMS connections go to a 2.1mm coax power plug.

A picture shows it best… the pack is 3S1P 20400 1500mAh cells, the BMS now covered in heatshrink for use in the field. The connector on the pack plugs into the charger to charge up or the BMS to power something connected to the power connector.

AFAIU, the LiPO BMS you buy do not do anything to control the charge current… you could use it when charging but the charger would need to be a CC then CV system. LiFePO BMS have chargers. Or the LiPO and LiFePO BMS I’ve seen on eBay work like this.

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This one (which I’ve ordered) claims to:

One thing that concerns me is that the BMS modules don’t seem to have any way to control/monitor the individual cells in a parallel set of cells unless they are doingsomething clever by comparing the parallel sets.

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I feel that many of these BMS lack important info on how they should be used.

Mine does no charge current / balancing. It’s a set of over/under voltages switches per cell to stop the voltage applied to a cell exceeding 4.25V and it disconnects any cell if the voltage drops below 3.2V (I think). There’s a bulk discharge current limit of 20A where it disconnects the cells.

The one you link to has a balance function. Normally these work by detecting when the voltage difference between cells exceeds something like 0.2V. At that point the charging current is interrupted and the high voltage cell is connected to a low value resistor. This discharges the cell until the voltage is close to the other cells when the resistor is disconnected and the charging current is applied again. As the cells charge, this simple system keeps the cell voltages close.

LiIon/LiPO work best when charged from constant current and neither of them has anything to set the charge current though. So I believe you still need a constant current source to provide the charging current with either BMS. The advantage yours has is the cells will stay balanced. That’s why I charge mine using a separate balanced charger. I have a “bodging” cable that takes the balance connection and makes balance and bulk connection to use the iMax B6 with these packs.

Some LiFePO versions of these do have a constant current charger built in. Typically the charge current is 1A but you can program it by changing a resistor on the board.

As for parallel cells I think they just rely on Kirchoff’s law. If 2 cells are differing in voltage, 3.7 and 3.8, when you connect them in parallel current will flow from the 3.8V cell to the 3.7V until they are the same voltage. The BMS sees the combined terminal voltage.

One pack I have is 3S2P from 6x 13400 cells. I picked 6 cells which were close in voltage and wired them up. My thinking being take cells that after use are close in value and they are hopefully in the same physical condition.

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Thanks @MM0FMF and for the pictures. That explains it and I like your solution - essentially relying on a charger for a balanced charge across the cell groups. May try this same idea.

Had not really thought through how the BMS would work and that it regulates discharge, not necessarily charge of the batteries. So better to have a JST connected for each cell bank and let the charger deal with it.

My charger will bulk charge and balance charge via JST, just need to specify what I need when setting it up. It didn’t cost too much on Amazon FWIW.

I’ve been very impressed with what I have got from my Wombled batteries, 3ah from a 3s2p pack of the larger vapes. It’s decent and feels reliable even with my soldering abilities :slight_smile:

NOTE: I’ve had the aroma of whatever vape it was when putting on new wires :joy::joy::joy:

NOTE2: not sure I’d want to take it on a plane. Looks rather suss !!!

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Since a KX3 needs at least 12.8 v to run 15w, I have to skip all the wonderful 3s advice, sadly. Much of it can’t be scaled-up

Elliott, K6EL

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