7ah at only around twice the size of a 1.3ah SLA is pretty impressive!
Kayak Batteries- SLA vs Lithium
One of the first accessories that many people get for their kayaks- and with good reason- is a fish finder. But what should you be using to power them? There are two main different types of batteries which suit the task, SLA and Lithium, so here’s a few positives and negatives (man would ya look at that pun) for each in the context of offshore kayaking!
It's also worth noting first up that I'm not an electrician, but this fairly basic list of pros, cons and safety should help you get started if you're unsure of what to do!
SLA (Sealed Lead Acid)
These are the perfect battery if your goal is to keep things simple. Their two main attributes are affordability and toughness which means that you don’t have to worry about them too much- a blessing indeed during a big day of fishing. Being sealed, they can handle a few splashes without any major immediate problems, but that’s not to say that it’s a good idea to splash them with saltwater- it will of course cause the terminals and connections to corrode over the course of a few trips. These batteries are usually wired up to the head unit using spade connectors which are very simple to install and if these connectors do corrode they are easy and cheap to replace. One tip when using spade connectors with these batteries is to always unplug them immediately after a paddle- leaving the battery plugged in, especially when wet, accelerates this corrosion.
The primary issue with SLAs is their weight. Especially once these batteries start getting bigger, they can be heavy enough to make moving your kayak around off the water that little bit more difficult.
In smaller sizes their weight won’t present any issues, but little SLAs are only appropriate for 4 inch sounders or less which they usually only power for 4-6 hours. This is all that most paddlers will need for a session but it can be frustrating if you do decide to stay out longer only to have your fishfinder die on you.
A small SLA Like this one, while fairly light and compact, won't power many sounders for long.
SLAs also eventually need replacing as they will lose their ability to hold charge slowly over time (don’t worry too much though- they should last for a good few years), but again, they’re inexpensive to replace which understandably outweighs this issue for many people.
Lithium Ion batteries on the other hand offer very different set of traits. They’re fantastically small and light for the amount of power they put out which makes keeping sounders ticking for ages a breeze. They have the added advantage of lasting a long time and have very little depreciation, but on the downside they can be fragile or even volatile if not looked after/used properly.
The good news is that when lithium batteries are sealed well they retain those advantages while minimising the risk of being damaged. One option here is to make up your own battery case and use separately sourced cells inside, or alternatively some options exist on the market such as FPV power batteries which work well and have a good system for sealing their connections. These come in either a 7ah or a 17.5ah for the bigger sounders and come with chargers as a bonus.
FPV power batteries are a good, easy to use lithium option
If lithium batteries come into contact with saltwater however, unlike SLAs they can short out quite violently- if this happens you’re not only likely to kill your battery but they can discharge all of their energy very quickly… sometimes in the form of heating up or catching fire. This certainly presents a safety risk and should factor into your decision.
Lithium batteries do require specific chargers which are generally more expensive, and (IMPORTANT) if any connections aren’t completely dry when charging then short circuiting can occur. It’s also extremely wise to not leave these batteries charging unattended in case their connections aren’t fully dry as they can catch fire if this happens.
To summarise, SLAs are highly dependable and simple to use, whereas Lithiums require a little bit more care and can be dangerous if used improperly but are light, small and will power your sounder for longer. Both have their advantages and disadvantages and each have their place- you just have to choose what’s right for you!