The more I think about it, the more I can see that the capacitor is a really bad idea.

Blocco makes a good point about the un-flat discharge of the capcitor. The capacitor will trail its voltage off significantly as it discharges, so even the usable charge range is limited. I did a calculation based on a 500mA camera discharging the capacitor from 14.4V to 11V and got 17000 seconds (4.72 hours). That's the equivalent of 2 Amp-hours at 12V. A car battery has 45 Amp-hours. No comparison.

http://mustcalculate.com/electronics/capacitorchargeanddischarge.php

 

The more I think about it, the more I can see that the capacitor is a really bad idea.

Blocco makes a good point about the un-flat discharge of the capcitor. The capacitor will trail its voltage off significantly as it discharges, so even the usable charge range is limited. I did a calculation based on a 500mA camera discharging the capacitor from 14.4V to 11V and got 17000 seconds (4.72 hours). That's the equivalent of 2 Amp-hours at 12V. A car battery has 45 Amp-hours. No comparison.

http://mustcalculate.com/electronics/capacitorchargeanddischarge.php

That seems to be the general consensus online as well. My initial desire with the capacitor was to never have to replace it like a battery, but it does not seem that desire would outweigh all the downside like lower stored capacity and total cost. I am leaning towards a battery now, what do you think of the battery I linked to a few posts ago? I have never heard of a Lithium Iron Phosphate battery until researching this, everyone seems to agree it has a higher storage than an AGM, or other type of regular car/ motorcycle battery and last much longer.

I also found this other model but again I have never heard of these type before.
http://www.amazon.com/Shorai-423825...r=8-7&keywords=Lithium+Iron+Phosphate+Battery

Thanks

 

That seems to be the general consensus online as well. My initial desire with the capacitor was to never have to replace it like a battery, but it does not seem that desire would outweigh all the downside like lower stored capacity and total cost. I am leaning towards a battery now, what do you think of the battery I linked to a few posts ago? I have never heard of a Lithium Iron Phosphate battery until researching this, everyone seems to agree it has a higher storage than an AGM, or other type of regular car/ motorcycle battery and last much longer.

I also found this other model but again I have never heard of these type before.
http://www.amazon.com/Shorai-423825...r=8-7&keywords=Lithium+Iron+Phosphate+Battery

Thanks

Well, that one is 1/3 the capacity of a regular car battery so you'll get 1/3 the run time of the cameras until you run it down.

The other one is 50-65% of a regular car battery.

And these lithium batteries degrade significantly when exposed to high heat.

I would stick with lead-acid car batteries.

 

Well, that one is 1/3 the capacity of a regular car battery so you'll get 1/3 the run time of the cameras until you run it down.

The other one is 50-65% of a regular car battery.

And these lithium batteries degrade significantly when exposed to high heat.

I would stick with lead-acid car batteries.

Can I ask would you're only hangup with these be the high heat failure? I ask because if it's true they hold more charge for their size would this a better alternative if the heat isn't an issue? As I indicated before I don't have very much space so a full size battery is out and I would like to maximize whatever space I have. It will be inside the cargo area so it will never be exposed to high heat like under the hood would be. Or is in general a lead-acid battery still better?

 

Well, that one is 1/3 the capacity of a regular car battery so you'll get 1/3 the run time of the cameras until you run it down.

The other one is 50-65% of a regular car battery.

And these lithium batteries degrade significantly when exposed to high heat.

I would stick with lead-acid car batteries.

What about AGM vs lead-acid? I looked on Odyssey's site since they have an extremely good warranty, they have replaced both my batteries twice already at no charge without even asking why. This can also be mounted on it's side and holds 34 Ah vs the small deep cycle batteries available elsewhere. I could not find any lead acid batteries with a decent Ah rating that didn't cost close to the same as this one and I trust Odyssey's products.

http://shop.odysseybattery.com/p/pc950-p?pp=12

 

Can I ask would you're only hangup with these be the high heat failure? I ask because if it's true they hold more charge for their size would this a better alternative if the heat isn't an issue? As I indicated before I don't have very much space so a full size battery is out and I would like to maximize whatever space I have. It will be inside the cargo area so it will never be exposed to high heat like under the hood would be. Or is in general a lead-acid battery still better?

The Lithium batteries would be OK but I'm not sure the best way to charge them. Unless they have balanced charge input they won't last long under heavy charge/discharge swings.

Mainly they're expensive and not that necessary. If you were putting this on an aircraft or to be carried on a person I'd say go for the energy density but since it's in a massive vehicle the lead-acid have more capacity at less cost and the charging technology is endemic.

 

What about AGM vs lead-acid? I looked on Odyssey's site since they have an extremely good warranty, they have replaced both my batteries twice already at no charge without even asking why. This can also be mounted on it's side and holds 34 Ah vs the small deep cycle batteries available elsewhere. I could not find any lead acid batteries with a decent Ah rating that didn't cost close to the same as this one and I trust Odyssey's products.

http://shop.odysseybattery.com/p/pc950-p?pp=12

AGM: In a nutshell, Low water loss, lower self-discharge.

Here's a quote from an article about AGM:

AGM batteries are not the best choice for all applications - they are rather expensive compared to flooded batteries. However, their safety and design features make them the battery of choice for many applications, such as:

• Where you cannot have fumes or hydrogen, such as in poorly ventilated areas, or where fumes may cause corrosion to electronics, such as repeater and cell phone sites.

• Where resistance to shock and vibration is important.

• Where spilled acid from leaking, tipped, or broken batteries cannot be tolerated.

• When installed in a location where maintenance would be difficult or expensive, such as remote communications sites.

• Where the batteries may be subject to freezing (-40 degrees F or lower).

• Anyplace where you need a reliable totally sealed battery for safety or environmental reasons - wheelchairs, medical standby power, inside RV's, computer room UPS systems, or in enclosed spaces in boats.

http://www.solar-electric.com/agm-battery-technology.html/

None of those advantage situations apply to you, really, over the standard lead-acid batteries you already have. So you could certainly do it, but it just seems a waste of money.

 

AGM: In a nutshell, Low water loss, lower self-discharge.

Here's a quote from an article about AGM:



http://www.solar-electric.com/agm-battery-technology.html/

None of those advantage situations apply to you, really, over the standard lead-acid batteries you already have. So you could certainly do it, but it just seems a waste of money.

Did a lot of research myself last night as well. I went and purchased the odyssey I linked to. I already have two of those full size extreme series batteries and Odyssey's warranty is ridiculously good. Ironically it was the first three points about the advantages of AGM that made me decide to go that route. It's in the cab so I can't have the fumes and if you saw some of the terrain this Rubicon Jeep has been through you would agree the second two points are very important as well. Obviously thanks to everyone for all the help I think this will be a better solution for my issue after all. Thanks again