A 3A power supply should be man enough to charge ant antweight battery! If you're trying to charge something a bit more serious for a feather or heavy it might suffer.
Sounds like the power supply voltage is dropping when the charger starts to charge the battery.
If the PSU/charger combo has charged these batteries before, I would suspect the charger.
If you've never attempted to charge these batteries before, they may be too much for the PSU.
Either way, it seems like you might need a new PSU...
They are two 3700mah, 7cell batteries connected in series for my feather, so in effect it is a 3700mah, 14cell battery. So yes, I may need some more oomph. What sort of power supply would cut the mustard do you think?
*Counts coppers left over from buying charger*
Jonathan Atkinson Before you criticize another person, first walk a mile in their shoes. Then, when you critisize them, you'll be a mile away and have their shoes.
14 cells will require a peak voltage of around 1.5V per cell, so a total of 21V.
Assuming you charge at 1C, that's 3.7A.
So you need 21 x 3.7 = 77.7 Watts.
Assuming your charger can generate 21V out from 12V in, and it does so at 90% efficiency,
the required input power will be 77.7 x (1/0.90) = 86.3 Watts
At 12V this equates to 7.2A, so it's no surprise a 3A PSU struggles!
If my assumptions are correct re: voltage etc, then there are a few things you can do to aviod buying a new PSU...
1) Limit the charging current to less than 1.5A, this will in turn limit the 12V current to less than 3A and you should be OK. Personally, I would set the current to about 1A and accept a 4-5 hour charge.
2) Do you need to charge both sets at the same time in series? If you can charge them separately you may still need to limit the charge current, so I'm not sure this really helps...
3) Find a new PSU, you probably need about 10A @ 12V
Jonathan Atkinson Before you criticize another person, first walk a mile in their shoes. Then, when you critisize them, you'll be a mile away and have their shoes.
I wouldn't recommend splitting the packs after they've been one, if the pack voltage varies more than 0.1v it can cause the packs to try and balance themselves out and the too-ing and Fro-ing of current has been known to cause burning packs (Scorpion at Aylsebury is a good example).
If you can get a good PSU for cheap then do, I pretty much always charge my batteries at their C rating or close because my FW takes a lot of power out of them and I have to charge them for the next fight. 4 hours is a long time between FW fights, especially when its a 2 hour show with 2 FW fights at least .
So I can charge them with a lower current but It will take forever. Hmmm, I'll have to think about this one.
EDIT: 3.7 Ah at a maximum of 25 A would give around 9 minutes of battle. Sounds OK, that'll last three fights at least.
Jonathan Atkinson Before you criticize another person, first walk a mile in their shoes. Then, when you critisize them, you'll be a mile away and have their shoes.
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