Elect. Guru help

[dra8642]

HI,
I use these for SLA replacements in UPS systems. The life is 5 times longer than the SLA and the temperature specs are very good for us that like to fish in the cold. They have build in protection circuitry and are meant to be charged by the same chargers that SLA's use. Just check the maximum discharge current if you want to use for starting an engine. Otherwise a deep discharge can over-discharge the battery and it won't recover. Almost all of the SLA replacements here have all of the over, under, excessive (late night, cold and stupid moves) specs taken care of. They are all half of the weight of the SLA's and are sealed. They are pricey, but over time it will be cheaper. Great for lighting, electronics and pumps.

http://www.batteryspace.com/Powerize...B-and-LED.aspx

I popped this guy in a Pelican box and added a waterproof connector so I could hook up a solar panel to charge it up in the car or home to get it ready for next time.
http://www.batteryspace.com/lifepo4b...erstorage.aspx

Look around the website and you will probably find something that will work well.

Dave

[GregAndrew]

Originally Posted by bubblehide

Greg, your right. LION batteries produce heat as they discharge. The faster the discharge rate, the greater the heat produced (enough to melt right through a plastic kayak (recall the airline issues not that long ago). However, for the most part, placing small batteries in series/parallel hasn't up-ed the discharge rate to a point that would create a problem.

Yeah, that is not where I was going with my question. Seems to me that any batteries that are charged or discharged too quickly beyond their ratings will have a tendency to generate heat. Although that is a risk that everyone should be aware of when making their wiring connections to avoid shorts.My concern was that some of the cells seem designed for rapid discharge and some for slower discharge. And I was wondering if that was going to effect performance (battery life or run time). Also, I am not looking at LION batteries, but Lithium Iron Phosphate batteries (LifePo).

[bus kid]

Originally Posted by bubblehide

Greg, your right. LION batteries produce heat as they discharge. The faster the discharge rate, the greater the heat produced (enough to melt right through a plastic kayak (recall the airline issues not that long ago)

bad example, heat was not the issue for the airline, the issue was the gases emitted by the batteries not being able to be vented properly as the box containing them was too small. which caused a small less then 1 inch blue flame to be produced.

[GregAndrew]

The battery that you have linked, as well as probably all LifePo4 batteries, requires a special charger (scroll down to charger). That would be a good alternative to a 12v 12a LifePo4 battery because it only requires the same space. Although neither will fit into the WalMart type battery cases, and both would have to be regulated to use with our small bait tanks. I am using a 12v 12a LifePo4 battery from Bioenno Power (for my FF) that I got shipped with charger for $150. I added a Square Trade warranty for $20 for 3 years of protection. I have not really tested it yet, but have run one for at least 16 hours over a weekend without my HDS5 shutting off.

Originally Posted by dra8642

HI,
I use these for SLA replacements in UPS systems. The life is 5 times longer than the SLA and the temperature specs are very good for us that like to fish in the cold. They have build in protection circuitry and are meant to be charged by the same chargers that SLA's use. Just check the maximum discharge current if you want to use for starting an engine. Otherwise a deep discharge can over-discharge the battery and it won't recover. Almost all of the SLA replacements here have all of the over, under, excessive (late night, cold and stupid moves) specs taken care of. They are all half of the weight of the SLA's and are sealed. They are pricey, but over time it will be cheaper. Great for lighting, electronics and pumps.

http://www.batteryspace.com/Powerize...B-and-LED.aspx

I popped this guy in a Pelican box and added a waterproof connector so I could hook up a solar panel to charge it up in the car or home to get it ready for next time.
http://www.batteryspace.com/lifepo4b...erstorage.aspx

Look around the website and you will probably find something that will work well.

Dave

[PescadorPete]

Greg, I didn't measure it with water but I will this weekend when I gear up for my weekend jaunt.

[jruiz]

Originally Posted by GregAndrew

Yeah, that is not where I was going with my question. Seems to me that any batteries that are charged or discharged too quickly beyond their ratings will have a tendency to generate heat. Although that is a risk that everyone should be aware of when making their wiring connections to avoid shorts.My concern was that some of the cells seem designed for rapid discharge and some for slower discharge. And I was wondering if that was going to effect performance (battery life or run time). Also, I am not looking at LION batteries, but Lithium Iron Phosphate batteries (LifePo).

Short answer to your question, no. Long answer is that cell designers adjust the rate capability of a component cell by varying the thickness of the electrodes which directly affect your effective current density. Thicker electrode cells have lower current capability but higher energy density and thinner electrode cells the opposite.

Pack designers on the other hand adjust the current capability by adjusting the number of cells in parallel. Energy density in this instance stays constant and capacity increases.

Heat, fast charge/discharge, and the state you leave your battery at have the most impact on cycle life and irreversible capacity loss. Most battery manufactures ship batteries between 25-50 percent state of charge to maximize battery life and safety.

[PescadorPete]

Here it is with a Hobie bait tank, full of water, pump under load:

12V --> 1.37A
11V --> 1.20A
10V --> 1.06A
9V --> 0.91A
8V --> 0.77A
7V --> 0.64A
6V --> 0.52A
5V --> 0.39A

Good thing I did this. When I had the tank full, I noticed the front seam is split and leaking . Not from abuse, maybe a manufacturing defect? Time to get out the 5200.