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elios

join:2005-11-15
Springfield, MO
reply to lutful

Re: PSU's and DC-DC convters or Is There An EE In The House!?

it pretty much is untill we get a new battery type any way
Expand your moderator at work


elios

join:2005-11-15
Springfield, MO

1 recommendation

reply to lutful

Re: PSU's and DC-DC convters or Is There An EE In The House!?

got my stuff in and setup
PSU is putting out 25.5v so should be good to go
only tested up to 30amps on the charger so far but looks good


SmokChsr
Who let the magic smoke out?
Premium
join:2006-03-17
Saint Augustine, FL
reply to lutful
said by lutful:

The exact time when charger needs to move a particular battery pack from constant current mode (CC) to constant voltage mode (CV) will gradually drift apart.

The packs I'm working with the protection circuit in the battery pack does all the decision making for the pack. All the pack wants from the charger is the proper voltage to charge with. After that the circuit will do all the cell balancing and even cut the charger off if it allows the voltage to get too high. Since my charger doesn't even approach 1C, I don't know if they will regulate the charging current to keep it from getting to high.

With a 40A charger that should put him a bit above a 2C charge with 6 packs connected. Even worse it could try to go above 10C if only one pack is connected.

PS I'm using 8cell 10AH packs for ENG lighting. Replacing the old standard 24 cell 4000mAh NiCad battery belt. Ahh so nice 3X the run time and half the weight.

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
said by SmokChsr:

The packs I'm working with the protection circuit in the battery pack does all the decision making for the pack ... don't know if they will regulate the charging current

Yes. Since I usually quote Linear Tech, let me try Texas Instruments this time ... bqSWITCHER™ series are highly integrated Li-ion and Li-polymer switch-mode charge management devices ... high-accuracy current and voltage regulation, charge preconditioning, charge status, and charge termination, in a small, thermally enhanced QFN package

»www.ti.com/product/bq24100

Of course, RC li-poly packs do not incorporate such ICs and brute-force parallel chargers can't adjust the charge current for each pack.


optionz

@tmodns.net
reply to elios
It sounds like you have solved your current problem. But might need more fyture power. So here are some other options. For big power chargers try golf cart 36 48 volts. Or telephone chargers 48 50 60 volts. Or electroplating supplies 10- 40 volts variable. All at high currents. If you dont need regulation you can use any old broken one as long as the transformer and diodes and filter are good.

With the simpler supplies you can also raise the voltage over spec with one of the variac powerstat models that has a winding tap giving 130 volts out with 115 volts in. Those are expensive but allow you to match your load. If you just need to reduce your voltage an ordinary cheaper 20 amp dimmer will work.

Even more basic you could gain voltage from a transformer by adding turns to its secondary or removing turns from its primary winding.

Or you could just use a bigger battery bank for your dc.

As mentioned your limit is the 20 amp 115 volt breaker that trips about 2300 watts.