Elect. Guru help
 

I am talking with a company that assembles Lifepo4 batteries about making some 6v batteries for bait tanks. They need to know what continuous current will be required for the batteries. I have looked at the 5 or 6 pumps that I have and see 1.8 - 2.5a at 12v on them. I believe they will draw the same amps when stepped down to 6v, but wanted to double check. Anyone running a 500gph pump that draws more than 2.5a?
I am checking into both 12a and 20a versions with and without the sealed ABS housings depending on size.

Power = volts x amps = 24watts= 12v x 2amps
if you use 6v on the same device, the current (amps) will need to double to do the same work!

I did this test on my Rule 24(360GPH) at 6V and it drew less than half the current as compared with running it at 12V. So about 2.3A at 12V and <1A at 6V, so the relationship is not linear. Li-ion batteries go up in increments of 3.7V running voltage so you're probably going to dealing with 7.4V which would bump up the current draw a little bit.

20Ah would be nice for islander trips where you either have no access to power or just don't want to hassle with charging.

PM me whatever questions you have or you can put them right on this thread. I design/manufacture lithium batteries and am an EE.

Personal experience has led me to believe that the draw is 1/2 of what you see on the 12 volt pumps running 12 because the same Ah battery 6 volt seems to run twice as long. My 6 volt 12ah will easily run twice what my 12 v 10.5 will.

Don't worry about the C rating for your pump. The rating becomes critical when you are pulling high amps, such as electric RC brushless motors. I have some 400 sized brushless motors that can pull up to 40 amps with the right speedcontroller. The packs I've run for the FF and bilge were 20 C 11.4volt packs, I can't remember the Mili amp hours, but somewhere in the 4000 range. Expensive batteries. If I remember correctly, the C rating is applicable to the charge rate as well, so depending on how fast you want to charge the pack, get the proper C rating for a fast charge.

HOW do you keep them from randomly catching fire?:eek:

Don't charge them above the rated charge current and buy from a reputable manufacture.

Most companies nowadays incorporate safety features like shutdown separators, PTCs, and vents to minimize these occurrences. There are also safety standards they must meet before they can be shipped by air or ground. I personally wouldn't buy a large format lithium ion battery unless it has a UL, IEC, or ANSI marking on it.

LifePo4 battery's are not the same as LiPo which are what most people think of when they say battery's catching fire or exploding. LifePo4 batteries are very safe and if they are sealed in a plastic waterproof housing there as safe as sealed lead acid batteries. They are more expensive than lead but the big difference is out of a 10ah lead battery you get roughly 4-5ah of use able power before the voltage drops too low but with a LifePo4 10ah battery you get roughly 8ah of use without voltage drop! So you get almost double the use able life and depending on the battery you can jump start your car with it. I have a 100ah LifePo4 that I plan on using on a trolling motor setup whenever I get around to setting it up.

Depending on the size required, the larger capacity batteries would be for travel use. Mothership and trips to Mexico for me in particular. Thanks for all the timely info guys.

Greg,
I measured the Hobie bank tank pump (Tsuanmi 500) with no load (no water in the tank).

12V --> 0.32 amps 3.84 watts
6V --> 0.23 amps 1.38 watts

so roughly 40% of the power @6V vs. 12V.

I can measure it with a full tank of water this weekend if it helps, let me know.

BTW, Ohms law is not the way to look at this, its an inductive motor load, not a resistor.

Pete

interesting... Where is best place to buy batteries? Looking to get 2.. Are you all saying a 6 can last as long as a 12? Sorry not an ee so keep it simple for us non-mcgiver types:rolleyes:

Whatever it is you can add me to the list of potential buyers. So far I'm loving my Bioenno battery(thanks for recommendation Greg). Yes, it wasn't cheap but not having to worry about it going dead in 8hrs is worth every penny to me.

where did you get it from?

I used batteryspace for my battery they sell everything you need to make your own pack or buy a premade one. Honestly you could make a pack perfect for kayaking for around $100
I would use 2 or 4 of the 3.2v 16ah LifePo4 cells $39 each, pick up a pcm to monitor voltage and a charger. Assemble it in a pelican box and your good to go. Extremely small lightweight battery setup that's going to last a long time. For 12v they do have some nice premade setups like a 12v 20ah with led balancing for $179
Just my $0.02

Am I wrong, or is there something more to these cells than just placing the right combination of them in series and parallel in order to get your required voltage and Ahs? All the cells seem to have a different discharge rate. At our usage, does that even matter?

For the most part setting up these battery's are simple. Pretty much you use whatever combination you need to get the required volts and ah and what little power our fish finders and bait tanks use isn't enough to really matter since it really isn't much power.
From what I see others have posted a bait tank uses 0.25ah at 6v but if you use 2 cells like this http://www.batteryspace.com/LiFePO4-...3.4-screw.aspx
These are capable of 160ah discharge continuously so that bait tank pump pulling 0.25ah is nothing compared to what it can supply. Most high end brand LiFePo4 battery's are around 10C rating so they will supply more than enough current to run out stuff. And that is why my 100ah LifePo4 battery is so use full, I have used it to jump start cars twice since it has 1000ah discharge rate, I just need to make a waterproof case so when I finally put it on the yak I don't risk shocking myself with all that current...

ask Louie
 

I dont know if hes still around but I met a guy a long time ago when I worked in a hobby shop. He was building a full electric car before it was cool,and had a battery powered skateboard that did a easy 30 mph and knew all about batteries (lipos) before anyone was talking about them.

http://www.electriclouie.com/.

Hey Pete, how did you measure it, and did you happen to measure it with water? Looks like the batteries are going to be very affordable for LifePo4.

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.

Here are the specs on the same pump under load for 12V and 13.6V. 1.4A current draw at 12V. So it should be less than that for 6V

http://imageshack.us/a/img854/3778/sc20130510074134.png