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LiPO lover seeks friend


#1

I have a 7Ah Gel cell in excellent condition that is available free. Collection only; from Macclesfield.

I have finally succumbed to weight-loss by LiPO suction.

73

Richard
G3CWI


#2

In reply to G3CWI:
Hi there Richard, i too would like some LiPo, could you recommend a supplier?

Many Thanks

2M0ETR
Adrian


#3

In reply to MM6ADR:

Adrian

Mine came via e-bay. Look for LiPO on the reflector here and you will find all the info that you need.

73

Richard
G3CWI


#4

In reply to G3CWI:

You could sneak it into Tom’s bag next time you go out together. Make sure it’s fully discharged too so it’s of no benefit to Tom once he has lugged it to the top!

This course of action may affect Tom’s keeness to dole out the soup, bring a reserve flask in case.

:slight_smile:

Andy
MM0FMF


#5

In reply to MM6ADR:
Hello OM
I would recommand Hobbyking http://www.unitedhobbies.com/hobbycity/store/uh_index.asp
also look for the right balancer, these work realy great also for other type of battery’s. You’ll receive your order within 14 days

73’s PD2PC Patrick


#6

In reply to PD2PC:

I went for andy MM0FMF’s link for the cells

http://cgi.ebay.co.uk/2x-11-1v-4000mAh-15C-LiPo-3-Cell-RC-Battery-11-1-WF_W0QQitemZ270341183577QQcmdZViewItemQQptZUK_ToysGames_RadioControlled_JN?hash=item3ef1971859

Worked out at £11 each for 11.1v 4000mAh 15C

And this charger

http://cgi.ebay.co.uk/RC-BC6-6-Cell-Lipo-Pb-NiMh-NiCd-Akku-Battery-Charger_W0QQitemZ230375240808QQcmdZViewItemQQptZFR_YO_Jeux_RadioComRobots_VehiculesRadiocommandes?hash=item35a36f3468

73

2M0ETR

ADRIAN


#7

In reply to MM6ADR:

What the ads don’t tell you Adrian is that the cells come with lead weights to fit inside your backpack… all part of a special free offer instigated by the sealed lead acid manufacturers’ guild :wink:

73 and don’t float away!

Gerald


#8

In reply to MM6ADR:
Thanks Adrian for the very intersting link
73’s PD2PC Patrick


#9

In reply to MM6ADR:
I’ve used one of the batteries a few times now on activations- the one that came with 11.1V DC across the pins. Very good too. The second battery had 7.8VDC across the pins fron NEW as supplied from Hong Kong)and the simple balanced charger would not start charging it at all. John BVE mentioned a cure was possible but did not elaborate when I met him. Is there a remedy for this battery so it can go on the normal charge cycle?

73
David


#10

In reply to 2E0DAI:

Hi David

11.1V is the absolute minimum voltage for a 3 cell pack going below that voltage potentally damages at least one cell (each cell should never be taken below 3.7V) and it cannot be recovered. It is very important to be aware of the batteries state of charge especially towards the end of a lengthy activation.

Carolyn

Edited to add

the heli forums are full of people saying they’ve taken batteries far lower without problems… but also see the number of fliers who’ve had problems recharging potential bombs!


#11

In reply to G6WRW:

11.1V is the absolute minimum voltage for a 3 cell pack

Surely shome mishtake! (as they say in Private Eye)

For LiPOs

3.2V is the minimum when discharged
3.7V is the nominal cell volatge
4.2V is the voltage when fully charged.

For a 3 cell this gives 9.6V discharged and 12.6V fully charged.

Andy
MM0FMF


#12

In reply to MM0FMF:

I stand corrected… but why push them to their limits when we don’t need to?

Carolyn

I won’t be taking mine below 11.1V


#13

In reply to 2E0DAI:

Hi David,

I accidentally left one of mine on the operating bench powering the 817 and went off to do something else… The battery voltage went down until the 817 switched itself off. One cell was showing 1.9V when I checked them, the others being just below 3V. I can’t explain the disparity. Fortunately the battery charged up okay, though initially the charger cut off the charge cycle early. I put the battery on the 817 on receive for a couple of hours and then attempted a recharge and over three or four more cycles it came back to life and now holds a good 12.5V fully charged with no apparent loss of capacity.

As the charger dictated the charging when the cells were in poor shape, I wonder whether one cell on your battery has collapsed to a level where it cannot be recovered. Are you able to check the individual cell voltages? If so you will probably find that you have one cell well down with the other two at a reasonable voltage level. It might read 7.8V overall, but in the case of your battery this might indicate battery death, whereas with around the same voltage I got away with it.

Incidentally, I regularly take mine down to 3.5V per cell and they charge up okay without any problems. I suspect the commonly quoted 3.7V minimum voltage includes a safety margin. I have seen 3.3V quoted as an absolute minimum, but not by a manufacturer. Of course using LiPos for radio use is light work for them - even my 50W linear for 70cms only presents a 2.5C load to my 4AH 10C (15C max) batteries.

73, Gerald


#14

From what I understand regularly taking LiPos well below their nominal voltage severely reduces the number of times they can be recharged… but as with anything there will probably be exceptions.

Carolyn


#15

In reply to G6WRW:

There is also a school of thought that keeping the charge up rate to a low level (I use 0.2C) actually increases the number of times they can be recharged. So swings and roundabouts being the order of the day, I should get an average lifespan out of them.

73, Gerald

P.S. Just checked the 4 batteries after the last round of 4 summits in the LDs and the worst reading is 3.65V. Seems that I wasn’t shouting long and hard enough!


#16

In reply to G4OIG:

Hi Gerald

My comment wasn’t aimed directly at you :o)

but it does show how much confusion there is where LiPos are concerned in regard to using and charging.

The recommended charge rate for the batts I’ve just brought is 1C.

Carolyn


#17

In reply to G6WRW:

Hi Carolyn,

No, I didn’t see any arrows coming my way :slight_smile: - I was just demonstrating that there are two sides to every coin. I suppose it will be some years before anyone on this reflector can comment upon the lifespan of their batteries.

73, Gerald

P.S. No-one was interested in my 3.3AH SLABs when I offered them free some time ago. I wonder if Richard has given away his SLAB yet.


#18

In reply to G4OIG:

I also wonder how much quicker I’ll be at climbing without my ballast! as soon as I’ve cleared the nasty cough I have I’ll go and find out :o)

Carolyn

I’ll hold onto my SLABs… just in case I need the exersice!


#19

In reply to G6WRW:
I charge LiPo phone batterys everyday at work, Availability of universal chargers for mobile phones was poor until a couple of years ago.

I made 2 chargers using old phones that used LiPo’s, They produced a few good laughs amongst the testers until they realised they worked which in turn allowed them to reach there bonus easier!

We now use iwap chargers which are made for the job, they have automatic polarity detecting of the cell put on charge. If there is zero charge then it will not charge, To overcome this I use a charged cell which has 2 wires soldered on each post then jump the cell in the charger until its starts to accept charge.

I find some makes are better than others especially Li-ion, 90%+ of cells seem to work fine even after sitting around for months fully discharged. I have a 2m Hand Held i re-celled over 12 months ago with liPo cells and charges the same it did on the first day.

One day I will upgrade my FT-817 power supply and do away with the SLAB’s. Sean M0GIA


#20

In reply to G6WRW:

When it comes to real ballast, I have a 24 Ah SLAB…but being chicken, so far I’ve only used it in the tent!

73

Brian G8ADD