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Lithium Iron Phosphate batteries for Ice Fishing

3/10/15 @ 7:46 PM
I recently ran across Ted Peck’s mention of using Lithium batteries on this website, and then I ran across some AA-sized LiFePo4 (Lithium Iron Phosphate) batteries for sale in of all places, Walmart. They were $9.99 for a pack of 4, 600mAh capacity.

As it turned out, I was in the market to replace my 12V AGM/Gel batteries for both my Vex and underwater camera, which were pretty much done.

I did a bit of research, then went back and bought 2 packs. Went to Radio Shack and got a couple 4 cell AA battery holders, about $5 for the pair. Taped the 2 battery holders together and wired the leads in parallel to make an 8-cell, 12V, 1.2Ah battery pack. Added shrouded male QD tabs, so that both my Aqua-vu and Vex would plug in, and I had a nice solution to my battery problem.

I had previously measured the current draw of my camera at 450mA, and the sonar at 210mA. I tried running the camera on a single 4-battery pack right out of the package, and it ran for 45 minutes; after recharging the batteries, it ran 50 minutes. In other words, the batteries were at about 90% charge even after sitting on the shelf at Walmart for however long. Pretty impressive, for a rechargeable battery.

The 8-battery pack runs the camera for 110 minutes (measured). It should run the sonar for about 4 hours.

The major advantage is that the battery pack I built weighs 7 ounces including the foam insulation; the battery it replaced weighs 5 lbs. Since I mostly only use the sonar and camera for locational purposes, the run times are plenty long for me.

It is handy that I can use the very same chargers that I used for the 12V 7Ah Gel/AGM batteries. These are “wall-wart” DC supplies that put out 400-600mA, and top out at about 14.5V. They were made for safely being connected to a Gel/Agm battery for indefinite periods, but they also work great for fast charging LiFePo4 battery packs, getting a full charge done in about 3 hours.

These lithium batteries are a different chemistry from the lithium-ion batteries in your phone, laptop, and car. They share a lot of the good characteristics – fast charge and recharge, low self-discharge. They are not quite as energy-dense, but they are also apparently extremely safe – they are not susceptible to the thermal runaway issues that plague lithium ion. Oh, and they are rated for 2000 cycles as well…….

I will add a post to provide more detailed information on these batteries, as it can be challenging to find. Please note you cannot use these to replace the AA batteries in your GPS or other product, as the cell voltage is over 2X, and you will fry your toy.


11/28/21 @ 2:45 PM
USER SINCE 6/26/01

Thank you for your replies.

11/28/21 @ 9:36 AM

The sonar i mentioned in the OP is a vexilar FL8, and it pulls 0.21A.  6Ah battery would give this sonar 6/0.21= 28 hours operation nominal, room temperature.  Check your manual or google to find your sonars draw, likely similar unless you have a large lcd display.

I would subtract 20% if the usage is well below 20F, like outdoors on the ice.

So as others said, i would go with the larger battery if you really want 2 full 12+ hour days.

11/28/21 @ 6:52 AM
Fish Hound
USER SINCE 1/29/02

Agreed, without asking a pile of questions I would say NO, go with the 10ah at minimum.

11/27/21 @ 10:12 PM

How many hours did you get from using the SLA battery that you presently use with the unit? Amp hours are amp hours. It all depends on the amp draw of your unit and how many hours each day that you want to fish. The quick answer would be no to the 6ah battery. 

11/27/21 @ 8:37 PM
USER SINCE 6/26/01

Are the 6ah lithium batteries big enough to power a LCD or flasher type of locator for two days without charging?  Would a 10ah be a better choice?

10/28/21 @ 8:17 AM
USER SINCE 1/10/12

Love my Lithium LifePo4 batteries.  Won't buy anything else

10/20/21 @ 5:26 AM
USER SINCE 9/24/03

The original post was made over 6 years ago so the use of lithium batteries and availability of them was not nearly as widespread as it is now. 

The first two power boxes I built used SLA and lithium batteries. No issues with either type of battery. More often than not “battery failure” is attributable to user error, specifically, not taking care of them.

I shifted away from the standard style of batteries and last year rigged up a couple of units utilizing buck converters and power tool batteries to run my stuff. I’m bringing a drill along anyway so why not use the same battery platform for everything? It offers a lot more flexibility in what I can use those batteries for than a dedicated lithium or SLA ”flasher” battery can. 

10/13/21 @ 12:00 PM
Fish Hound
USER SINCE 1/29/02

Neat project, but why not just get an Amped Outdoors 6AH Lithium battery for $50? That battery does weigh 20oz more, but still substantially lighter than the 5# battery it replaced.

I keep the the parts around to run a graph or camera of my M18 batteries if necessary too. Never have had to do it with my 12AH Amped Outdoors Lithium's but have had to borrow it to friends running old $19 sealed lead acid.

10/11/21 @ 4:21 PM

Those of you who are using lithium 12V batteries now instead of the lead acid batteries how do you like them?  My 18 year old Vexilar battery is finally getting retired this year and I upgraded to Vexilar's Lithium Ion battery.  I hope it lasts as long as the one that came with the unit did.

10/13/15 @ 10:59 AM
Very nice; I like the charge control chip mounted directly to the cell holder, slick idea, and should make charging idiot proof.

Yes, your Vex charger will probably work fine. The one caveat would be whether it can withstand the charge current that these 18650-sized cells will draw. It is possible that you might break the charger; you will find out when you try it.

I would not shy away from the higher capacity cells for this application. The cells you referenced are 1.5Ah, you can find 2.6Ah in the same size battery. The relatively low discharge currents needed by the Vex are ideal for those larger capacity cells. (But, the higher capacity cells will stress your charger more...)

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