Quick battery question (Series Vs. Parallel) + Voltage/MAH

I recently was given a set of six (6) of those halogen flashlights with the 6Volt SLA/AGM battery. Most of the flashlights were dropped and have a bad halogen lamp or a bad switch but all but one (1) of the batteries seems to be in great condition. The batteries are 6Volt 4.5AH
My question is I know I can use 2 of them to get a 12Volt source but I forgot how to do that (I know I have to wire them in series) but will the MAH increase or just the voltage. what about wiring them in parallel?
I only need one 12Volt battery
One last thing if I do wire them in series can I charge the batteries with a 12V charger

Thanks

 

Series gives you the voltage sum but the amperage will not change
Series and parallel circuits - Wikipedia, the free encyclopedia

 

If you put two in series, you will get 12v/4.5Ah. If you put two in parallel, you will get 6v/9Ah. If you put two batteries in series, and then put those in parallel with two more in series, you get 12v/9Ah.

Batteries in series you add the voltages, but Ah rating is of a single battery.
Batteries in parallel you add the Ah ratings but the voltage is of a single battery.
When you do series AND parallel you add the voltages, AND you add the Ah ratings.

Here's a couple diagrams to make it clearer..
http://www.batteriesinaflash.com/wir...eries-parallel

And yes, you can use the 12v charger on either a series or a series/parallel setup, because those are 12v . You would not use it on a parallel only setup because that needs 6v.

 

I think I was just given a box of junk (That I now have to recycle )
I hooked up two batteries (Following the series diagram correctly)
but I only get 5.5 Volts?
and I just noticed that someone already helped them self to 3 of the batteries so I only have three total (No wonder the box was so light )
Would it do any harm if I try to charge the two batteries that I connected in series? I don't want an exploding battery or anything dangerous like that just a charged battery
Thanks

 

You can try trickle charging them (they won't explode), but if you're only getting 5.5v out of two in series, it's a pretty good bet they've flatlined. What are the voltages individually (of all three)?

 

Those are probably gel-cells rather than AGM batteries. I just refurbished three Streamlight rechargeable lanterns and found each of them had a dried-out battery that rattled when shook.

Now for the bad news. Unless you have a constant voltage power supply it is probably not safe to attempt to charge those batteries. Most common battery chargers do not have a constant voltage output.

 

You don't need any special charger for them.. Any slow rate charger with a trickle function (like a 1.5A lawnmower/motorcycle charger-maintainer) will work. You just don't want to use a fast charger or an unregulated 'dumb' charger (one that doesn't shut off/float when it's done), because that will cook them.

 

OK Here are the voltages of the individual batteries
Battery 1 = 3.73 V
Battery 2= 1.75
Battery 3= ol (Which according to my DMM means open circuit)