Batteries to power flashers and portable graphs on the ice: the alternative to Sealed Lead Acid

Most people use Sealed Lead Acid (SLA) batteries to power their flashers or portable graphs on the ice. Ultimately, a 12 volt (V) Lithium iron phosphate (LiFePO4, hereafter referred to just as “Lithium”)  battery costs you more upfront than a 12 V SLA would. But for many of those who take ice fishing seriously, the investment is probably worth it. I requested data from one of the Lithium vendors to beef up this review, but I am not affiliated with anyone producing or selling Lithium batteries.

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In 2013, I had a bad experience where six snowmobiles got buried in deep slush at the same time. Getting them out took a long time, and the situation could have been quite dangerous under less favourable weather conditions.  Afterwards, I made up my mind that I needed to reduce weight in any way that I could for backcountry snowmobile trips. No more carrying a spare flyte for the auger, less tackle, one rod case instead of two, etc., on trips where slush was a possibility. I took it a step further a year later; I bit the bullet and purchased two 9 amp-hour (ah) Lithium 12 V batteries for my mechanical flashers. Lower weight was the primary reason for moving to Lithium, although I had read about several other advantages of this technology over SLA batteries.

Why Lithium?

After a year of use with my flashers, I was impressed by the performance of the 9 ah Lithiums. In spring 2016, I purchased two 20 ah Lithium 12 V batteries for my portable Lowrance graphs. I have used the four 12 V Lithium batteries extensively since. Here is what I have found:

Greater than 50% weight savings

A Lithium battery weighs less than half of a “comparably rated” SLA (more on this in a bit). A typical 9 ah SLA battery weighs about5.5 lbs; a 9 ah Lithium battery weighs about2.6 lbs – 53% weight savings! That difference is magnified for a 20 ah: about 13 lbs for SLA versus 5.7 lbs for a Lithium – 57% weight savings! In the context of weight reductions for backcountry trips, these differences are significant!

Run-time of comparably rated (ah) batteries is not comparable

I have been getting much better run-time from the Lithium batteries relative to “comparably rated” SLA using both my flashers in the winter and my Lowrance HDS 7Gen3 and Elite-7Ti year-round. I am confident in stating 50% greater run time can be achieved with the Lithiums. Trying to put it in real-world terms, at the end of most days on the ice/water (even very long ones) there is lots of juice left in my Lithiums. With a Lowrance Elite 7 Ti and a 20 ah SLA, after about 10 hours of run time with the screen on maximum brightness, the voltage is at 11.8 and the battery needed to be swapped out. After this point, voltage starts to drop rapidly, and over-discharging becomes a reality, which would reduce battery life going forward. This means that if I want to be on the water for more than 10 hours, I need a larger battery, or I need to carry a spare. Both of these alternatives are a pain. With the Lithium 20 ah powering an Elite 7Ti, 14 hours run time is no problem (and my days are seldom longer than 14 hours).

I am now so confident in the consistent performance of the Lithiums that I no longer bring a spare battery. Another great feature of the Lithium batteries I purchased is their built-in Battery Management System, which prevents over discharging and compromising the batteries capacity. So with these Lithiums, you can literally run your sonar until the batteries automatic shut-off kicks in, and not have to worry about compromising the battery going forward. Slick.

A 20 ah Lithium powers this Lowrance Elite-7Ti custom ice kit. With this setup, you will have plenty of juice to get you through a 14-hour day on the ice, switching between flasher mode, graph mode, and chart mode (maps), or endless split-screen combo options, with all settings maxed out. This 20 ah Lithium weighs 5.7 lbs, which makes it viable for hole hopping.  Not so much with a 20 ah SLA which weighs in at about 13 lbs.

Voltage properties are excellent

With Lithium, voltage is nearly constant as the battery is discharged, almost until the battery has no juice left. As a result, there is no need to adjust the gain in order to see the same strength of signal return while staring at your flasher. That might sound minor, but being a sonar nerd, I like this property a lot.

Discharge curve associated with a 20 ah Lithium battery (at room temperature, 20 °C). “C” = battery capacity.  Data provided by Bioenno Power.

Cold weather performance is better than lead acid

The performance of all batteries is influenced to some degree by temperature.  Lead acid performance declines in cold temperatures. So does Lithium iron phosphate, just not nearly as much.

Available capacity associated with Lithium iron phosphate versus lead acid (Absorbent Glass Mat [AGM], the “best” lead acid has to offer) across different temperatures. “C” = battery capacity. Data provided by Bioenno Power.

 Charging is fast and efficient

The 9 ah Lithiums I bought came with 2 amp chargers, and in less than 5 hours they are fully charged. The 20 ah Lithiums came with 4 amp chargers, so again in less than 5 hours they are fully charged. Energy efficiency associated with charging Lithium batteries is reported to be 97% (relative to about 70% for lead acid). This difference may be especially relevant if you plan to recharge off a generator or solar system (at the cabin for example).

Memory? What memory?    

Lithium batteries do not suffer from memory effects.  You can recharge them when they are at 97%, 83%, 62%, 50% or 21% of capacity, without any negative consequences.

Longevity is reputed to be great

Manufacturer specs for Lithium batteries indicate far superior longevity versus SLA. After 2,000 recharge cycles, useable capacity is expected to have declined to about 80% of rated capacity. Assuming that is true, reputed 10 year life spans certainly seem conceivable (and this blows SLA and even premium deep cycles out of the water). My 9 ah Lithiums purchased in 2013 seem to be as strong as they day I bought them, same with the 20 ah Lithiums purchased in spring 2016. And I consider myself a high-volume user.

Price = buy once, cry once

Lithium 12 V batteries cost 3 to 6 times more than a “comparably rated” SLA (last I checked), but I use the term “comparably rated” cautiously because SLA to Lithium is not apples to apples in terms of amp hours. And, you should get far superior longevity with Lithium if you treat the battery right. In the long run, going Lithium should save you money, it is just a question of how much. Last I checked, there was a big disparity in the pricing of Lithium batteries between vendors. I ended up ordering from Bioenno Power (California). They answered all my questions promptly, their prices were 50% lower than some of the other Lithium vendors I investigated, they offer a two year warranty on the batteries I purchased, and all of their batteries come with a built in Battery Management System (which prevents over discharging). That feature is huge. If you are going to drop considerable coin on a Lithium battery, make sure you get one that has a Battery Management System!

An unfortunate reality concerning over-discharging of lead acid batteries: One thing to keep in mind with SLA batteries is that you can only get about 50% of the batteries’ rated capacity out of it before you start to compromise the battery’s long-term capacity and longevity. You should not be draining a SLA battery until your sonar dies; permanent damage to the battery will have resulted by this point. The next time out, you will have less capacity than the time before, and the issue tends to snowball from there. Before you know it, you are replacing your SLA even though it is only a year old. Deep cycle batteries (i.e., in your boat or RV) are more forgiving in this regard, but for the SLA batteries typically used to power flashers and portable graphs, I would advocate never running your SLA battery down further than 11.5 V (11.8 V would be better). Of course this means you are not going to get 9 ah of juice out of your 9 ah rated SLA, but it will last longer and save you money over the long term.

Verdict?

In my opinion, Lithium batteries should be considered a great option for those who spend a lot of time on the ice. I will never go back to SLA.

Tight lines!