Battery problems

[Toastedghost]

Hi
Can some one please help me.
I need a battery solution to power a DVD/TV 12V 5A 45W
I have tried 3 different types of batteries but only managed to power the set for 35 mins max.
Does any one know of a solution to this problem without using lead acid batteries?

many thanks

Colin

 

[Sceadwian]

Use bigger batteries.
Lithium's will work nicely, at that current you'll need really large ones though. Why are you avoiding lead acid cells?

 

[Toastedghost]

Hi Sceadwian

I avoid lead acid because of the weight problems
Lithium is good but even this 12v 8400mah Li-ion power pack lasted only 20 mins
any solutions
Thanks

 

[Sceadwian]

Use a bigger pack.

 

[Toastedghost]

Thanks do you know where I could obtain such a pack?
Thanks again

 

[Sceadwian]

You already bought one.. buy a second and put it in parallel. You really should be trying to decrease the power the system is using, you're talking some serious batteries already.

 

[Toastedghost]

Thanks
This is what I have a 12v 8400mah Li-ion power pack and a 12v Lithium Battery 6600mAh
they both have standard 2.5mm plugs. Being a complete newbie how do I wire them in series?
Once again a billion thanks for your help

 

[audioguru]

If you wire them in series then the resulting 24V will blow up your DVD/TV and the batteries might catch on fire.

Newbies should not connect things together.

 

[Toastedghost]

Sorry I just said series in parallel? Does that alter the voltage?
Thanks

 

[Toastedghost]

Yes I am a dummy Sceadwian did mean parallel!
So in effect that should make it easier for each of the batteries
and I should get a longer play time from this configuration

 

[audioguru]

If both batteries are not at the same charge level then when they are connected in parallel one battery will try to charge the other with a very high current that might cause a fire.

 

[Toastedghost]

Hi Audioguru

thanks for the warning
Would both these batteries work together in parallel?
12v 8400mah Li-ion power pack and a 12v Lithium Battery 6600mAh
Or is it essential they are both the exactly same mAh as each other

Thanks

 

[Birdman Adam]

Both of the batteries must have the same mAh capacity rating.
**broken link removed**
Maybe with this quick schematic you can see why. Imagine that battery 2 runs out of power since it has a lower mAh rating. Battery 1 it still pumping current, and to get to the players, it must go through Battery 2. What ends up happening is that Battery 2 will get reverse charged, causing a lot of stress on the battery and a probable fire... When creating battery banks in parallel, I always am sure to use the same battery brand and model.

 

[audioguru]

Birdman connected the batteries in series which makes 24V and would blow up your 12V product. The batteries would also probably blow up.

With two different batteries in parallel then the one with the lower capacity will be discharged first but discharged too low (and you will not know) which will destroy it since a lithium battery must never be completely discharged.

If 8400mAh gives only 20 minutes then 15000mAh will give only 36 minutes. You need a much bigger battery for a longer running time.

 

[k7elp60]

Connecting batteries of the same voltage with different capacities and state of charge is possible with isolation diodes. The problem is then some of the voltage is lost accross the diode, so the equipment may not work as long due to the reduced voltage.
Using the attached connection scheme is one way. The diodes have to be in this case at least rated at 5A. With normal silicon diodes the voltage loss will be very close to 1V, with schottky diodes the voltage loss can be about 0.5 volts.

 

[Sceadwian]

Of course the REAL problem here isn't the pack is too small, it's the devices he's using use too much power... The DVD player probably uses minimal power, I would recoommend shopping around for a lower power TV.

 

[Toastedghost]

Hmmm
Thanks for all the input guys!
The option of a lower power TV is not an option unfortunately
I am a Clown/performer and on a shoe string budget
The TV/DVD player would be used in a performance
I might have to use a lead acid battery but I do not want the extra weight or bulk
Hey ho!
Thanks again

 

[Toastedghost]

What is the lightest available lead acid battery 12V 5A?
Does anyone know

Thanks in advance

 

[audioguru]

A 5Ah battery will also go dead too soon.
We were talking about a 15Ah battery going dead too soon.

You need a monster battery or a gasoline powered generator.

 

[Sceadwian]

Like I said, your problem isn't the battery, it's the power usage of the display, if you don't want to pay for a new display then you WILL pay for much more battery capacity than you need if you had a low power display. Either way you will pay more than you want to.