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Li-po Numpty Questions!


#1

Hi, Looking to power my FT-857 from a 4 pack 14.8v 30C li-po battery.
Have just got my hands on a KBPC3506 35A bridge rectifier.
I am now going to ask you a couple of silly questions.

  1. Li-po’s have a red and black lead. Fair enough, but they all have a connector block also wired to the cell. What is this connector block for?
  2. I take it that I feed the +ve of the battery to the -ve of the bridge rectifier, as I am trying to achieve a volts drop or have I gone round the bend. Any ideas on the rectifier woill be much appreciated, so I don’t over supply the radio on top of a summit.
    Cheers,
    John

#2

In reply to G1STQ:
Hi John i can only answer Q1 for you, i have 3S 11.1V lipos and this connector is required to be plugged in to your balance charger(for charging HI), its unused when connected to your radio.

Adrian

2M0ETR


#3
  1. I take it that I feed the +ve of the battery to the -ve of the
    bridge rectifier, as I am trying to achieve a volts drop or have I
    gone round the bend. Any ideas on the rectifier woill be much
    appreciated, so I don’t over supply the radio on top of a summit.

If you put the rectifier in the positive line then yes.

However depending on your construction it might be safer to put it in the negative line and reverse the rectifier direction.

Also connect the two AC connectors on the bridge rectifier together.

You can also have a jump lead between the three points to vary the voltage.

Nigel.


#4

In reply to G1STQ:

Just in case you were unaware John, you need a special charger for charging LiPo cells. You can’t use a NiMH or NiCd or SLAB charger. Also you can’t charge the cells in series as is often done with other types of cells. The extra connector is used for charging your cells.

Andy
M0FMF


#5

In reply to G1STQ:
Hi John,

you have to pay attention to full charged packs’ starting voltage.
A 3s pack starts from ca.12,3V and a 4s from ca.16,4V which is higher than 857’s suggested supply voltage (max. 15,9V).

Here can you see a discharge diagram of a 3s pack (4Ah, WinForce, made by china):
http://picasaweb.google.com/lh/photo/DhMvPsVLElcqXzn5BnzzIg?feat=directlink

Zsolt
HG4UK


#6

In reply to MM0FMF:
Andy,
While the “extra” connector is used on its own for balance charging 3S Lipos with the small Mystery charger described in one of your posts some time ago the process is different with BC6 or Accucel 6 chargers. With these both the “extra” connector and the power out cable must be connected for balance charging i.e. all cables from the Lipo must be connected. Having started with 3S Lipos and the small Mystery charger, when I recently bought some 4S and a BC6 charger, at first, based on previous experience, I only connected up the “extra” connector to the charger and every time I tried to charge I got a “Connection Break” error message. The answer came of course from Google where it is clear that a number of people have had the same issue. I don’t think that the BC6 manual explains this all that clearly although maybe I am just dumb.
Jim
G0CQK