Recharging Lead Acid Batteries.

I am interested in learning about recharging batteries. I've searched online, and find circuits, but very little information as to why they are constructed that way. My goal in this is simple. I do hobby photography, and have 2-3 flash units that I want to not have to keep changing rechargable AAs in. I know the Quantum battery packs are nothing more than a Lead Acid battery and some charging regulating circuitry. These things are expensive, for no good reason that I can see. I'd like to build my own, maybe even open source a PCB that could be used by other photographers to build their own. Can anyone point me to good references on charging batteries that have schematics that are explained, or you could explain it here?

http://www.electronics-lab.com/blog/?s=charger

"How a lead acid battery works" by Bill Hammock http://www.engineerguy.com/elements/videos/video-battery.htm

For 12v batteriesI use a lm317 as a constant current charge @ 1 or. 33 amps until its at 13v then set it as constant voltage @ 13.8v and let it trickle charge
takes forever for larger batteries, my brother killed his car battery down to 2v actually so im currently attempting to revive it with a regular charge, been set at 1amp for the past 5 hours and its only at 12.3v : \

These things are expensive, for no good reason that I can see.

Same issue wtth Lamborghinis. What gives?

zoomkat: Same issue wtth Lamborghinis. What gives?

There are plenty of affordable cars, Talk about taking an extreme case. I could build a car, actually let me rephrase that. I HAVE built a car, from remanents of other cars of the same year/model ((it was with a friend and it was his in the end). It was enjoyable and cost much less than him buying a new car, and it was very rewarding. That is how I attack this very problem. I want something, the costs are restrictive to me at the moment, and in the end learning how to build it myself is rewarding.

Thanks for the troll.

To everyone else thanks for the resources, I've looked through them and have to admit I still feel at a loss, but I'll spend some more time reading through them and see if the lightbulb turns on upstairs.

winner10920's suggestion of just charging it at a constant current to 13.8V using a 14.4V supply is all you need to do really.

The Texas Instruments BQ2031 datasheet shows the methods that chip implements to charge a battery on page 5 (notably figure 4). The only difference here is that they implement an additional trickle charging step for a highly depleted battery until it reaches a minimum "qualifying" voltage that demonstrates the battery is capable of being charged.

Don't forget the supply voltage is pretty important, if you want to get the full amp charge out of the lm317 the close supply voltage keeps the heat down, I was using a 16.5v supply and it got uncomfortably hot but unfortunetly that's what what I have, so I have to have a fan on it to keep it cool

I should probably mention since it seems people are assuming I am working with 12V batteries. I will actually be working with 6V Sealed Lead Acid batteries. I probably should have mentioned that earlier.

In that case float it to like 6.9volts

Thanks for the troll.

No problem! You might want to try some cheese with your whine.

I would not like to lug around lead acid batteries while taking photographs.

Why don’t you go for some Lithium Polymer batteries? They have as much energy but are lots lighter.

Check out: http://www.hobbyking.com/hobbyking/store/__317__85__LiPo_LiFe_NiMH_Battery-Turnigy_Lipoly.html
Look for “2S” type batteries as these have two cells and give you 7.4 volts (2 x 3.7 volts). If the voltage is too high, wire in a LDO regulator.

For a balancing charger look at:
http://www.hobbyking.com/hobbyking/store/_216__408__Battery_Chargers_Acc-Battery_Chargers.html

Its all cheap (but reasonable quality) and much lighter too.

Lithiums are also usually more efficient at charging, and better for size to power ratio which ,ay be useful in the photography field

I guess I had made my original choice based on what I had seen in existing power packs for camera flashes. I'll take that into consideration. Thanks.