Solar Powered Battery Packs and Electric Bilge Pumps

The electric bilge pump and the solar-powered battery pack work together in tandem to solve two of the most irritating and potentially dangerous situations a person is likely to encounter on an expedition: a capsize-induced cockpit full of water and dead batteries. Let's look at these two problems a little more closely.

A Cockpit Full of Water — Is This a Kayak or a Swimming Pool?

kayak solar power and DC bilge pump

The first, and by far the most dangerous situation (a cockpit full of water) occurs during a capsize whenever the paddler "misses" his eskimo roll (assuming he can do one) and is forced to wet-exit. Obviously, the cockpit fills with a tremendous amount of water, and because water likes to slosh around, this renders the kayak extremely unstable until the water is pumped out. Normally, a paddler would carry a simple, hand-operated bilge pump for these situations. And I do. The problem is that, for a skilled paddler like myself, the only conditions likely to capsize me (and to foil my very reliable rolling skills) are conditions far too rough to make using a hand-operated pump practical. The hand-operated pumps require the paddler to take one or both hands off of the paddle, which means you end up trying to pump water with little or no ability to brace yourself against the same waves that tipped you in the first place. Under these circumstances, the odds are that you'll just keep on tipping.

The alternative, of course, is to paddle the water-logged boat as is, and worry about dumping it out later. The problem with this solution is that if you happen to be paddling on Lake Superior or some other cold body of water, you'll be sitting in icy water for at least several minutes—possibly hours—thoroughly promoting the onset of hypothermia. Obviously, this won't do either.

So what's the solution? Well, there are two fairly good answers. Solution One is to install a foot-operated bilge pump on the front bulkhead. This allows you to pump out the water with your foot while keeping your hands on the paddle. However, this also requires you to be paddling a custom-fitted kayak which has its front bulkhead positioned conveniently within reach of your foot. For many paddler's kayaks, this isn't the case, as commercial kayak-builders usually locate the front bulkhead far forward to accommodate taller-than-average paddlers. Alternatively, if you're paddling a fiberglass boat and possess the technical know-how, you could 'glass in some kind of pedestal on which to mount the pump. If done correctly, this would allow you to effectively "retrofit" just about any foot-operated pump on the market.

Despite its utility and refreshing simplicity, there are a few (albeit small) drawbacks to foot-operated pumps: When using the pump, one of your feet must be off of its usual footpeg, and for some paddlers, this undermines their sense of balance and control—at least in situations when one is being tossed about by violent waves. It sounds like a minor problem (and to some extent, it is), but if you should happen to tip over again while operating the pump, odds are you'll come tumbling right back out of the boat. For me, there is also the issue of added weight. While a foot-operated pump may be fairly light (and certainly not an issue on an expedition), its permanent installation means a few extra ounces to carry up and down the beach everytime I go for a day-paddle, as well as a semi-annoying intake tube mounted down the centerline of the hull.

Kayak bilge pump comparison

Of course, there is another way to solve the bilge-pump problem. Solution Two is to mount an electric bilge pump behind the seat of your kayak, where most of the water (even small puddles) are likely to run anyway. Properly installed, an electric-bilge pump can evacuate nearly all of the water out of the cockpit in a matter of minutes, at the flick of a switch, without any effort, concentration, or fatigue on your part. In fact, if you purchase an "automatic" model or install a float switch, the pump can even turn itself on and off as needed (a wonderful psychological comfort in rough conditions).

Of course, this approach has a few drawbacks as well. First, like all electronics, an electric bilge pump can fail: the pump can break, the wiring connections can corrode, or the battery can die. My design mitigates these factors by housing most or all of the critical system components inside a watertight Pelican case. Nonetheless, since nothing is infallible, a hand-operated bilge pump should always be carried as a back-up. (It's important to carry a hand-operated pump anyway, as someday it may be needed to help empty out another paddler's boat during a rescue.)

Secondly, unless you mount the switch somewhere on the deck (not recommended because switches are more likely to fail if repeatedly subjected to torrents of water), you will need to open your sprayskirt to activate the switch. Of course, this isn't exactly a problem because if you've capsized and wet-exited, your skirt is already open; and if you haven't, there shouldn't be water in the boat anyway!

Lastly, because of the need for a battery to power the bilge pump, this system is noticeably heavier than a permanently-mounted, foot-operated bilge pump; however, this drawback is offset somewhat by the fact that the battery pack is easy to remove, and therefore adds no weight to your boat except when you install it for expedition use. (Of course, once you experience the awesome convenience of an electric bilge pump, you will probably want to use it for day-trips as well.) If you should ever need to portage the kayak over a long distance, the battery pack can be removed and carried separately. Most importantly, the battery is not just dead weight. As we shall see in the next section, it can do far more than simply provide power to the bilge pump. It can transform your kayak into a self-sufficient mobile power station!

Dead Batteries — What Ever Happened to the Energizer Bunny?

The other potentially-dangerous problem which is likely to occur during an expedition is to run out of batteries. This may sound like a small issue, but what if those batteries were powering your flashlight, GPS, cell phone, satellite phone, and VHF radio? Suddenly, you're lost in the dark with no way to signal other boating traffic or contact the outside world for help. Okay, maybe not everything would fail at once, I admit. But once you find yourself just a few batteries short, you'll have to start juggling batteries from one device to another, draining them faster. If you're nowhere near civilization (or near a battery store in particular), this could be a real problem. At the very least, it would be a real annoyance.

So what's the solution? Well, there are two obvious choices. First, you could carry a plethora of spare batteries (which many paddlers do). The problem is that even for short trips (3-5 days) you ought to carry at least one spare for every battery being used in a device. In other words, if your GPS, VHF, and flashlight take a total of 15 batteries, carry an additional 15 replacements. As for your cell phone or other devices which take specialized batteries, you will either have to use power conservatively or spend some cash buying spares from the manufacturer. So far, this sounds manageable; however, if you're going to be out for longer than a week, the number of "replacement" batteries quickly increases to a load of several pounds. As your batteries die, you'll need to keep them carefully separated from the fresh replacements. Moreover, you'll have to keep carrying the weight of the dead batteries until a trash receptacle can be found. (Don't go polluting nature just because you're too lazy to hang onto them!)

On the other hand, you could carry 20 "AA" batteries, one "core" battery (conveniently, the same battery powering the bilge pump), a small solar panel, and a cigarette-lighter power socket. Assuming most of your gear runs off of "AA" batteries (as mine does), this would enable you to always have ten fresh "AA" batteries and ten replacements—as well as the capability to recharge specialized batteries for devices such as VHF radios or cell phones—all for a total weight of about ten pounds!

Ten pounds may sound a bit heavy. Indeed, if you think only in terms of batteries, it would take at least several dozen "AA" batteries to rack up that kind of weight. However, we're not just talking about replacing spare "AA" batteries here. Keep in mind that for just a few extra pounds, this system also gives you the benefits of an inexhaustible solar power supply, an electric bilge pump, and the ability to recharge specialized batteries in devices such as cell-phones, GPS units, and VHF radios (anything that can be recharged from an ordinary cigarette-lighter socket). If you're going to install an electric bilge pump, you'll have to install the "core" battery anyway (which is, by far, the heaviest component of the system, comprising about half the weight). But with a negligible increase in weight, you can add a solar panel trickle charger and 10 "AA" battery tray to transform your kayak into a low-maintenance, self-contained, mobile power station. Even better, thanks to the "core" battery which powers the bilge pump and comprises the main energy reserve of the system, you won't be dependent on the sun. By carrying a small cigarette-lighter socket with power leads (and the cigarette-lighter recharging cord for a specific device, such as your VHF radio) you will be able to hook up directly to the "core" battery and recharge your devices—even at night! Best of all, the entire system takes up almost as little space as the average hand-operated bilge pump, and can be removed instantly from the boat (for portages or for occasional maintenance) by undoing a simple set of velcro straps.

Solar and Bilge System Components — What's In The Box?

[Solar Panel Battery Pack]

Okay, so I've finally convinced you that this is the ultimate water-and-power-management system and now you want to build one. What do you need? Well, there is a fairly long list of mildly-pricey components (total cost: $160 - $190), but don't be deceived: The finished product will be compact, powerful, and cost-effective. Half the system will pay for itself just from money saved by using rechargeable batteries. The rest will pay for itself through astonishing convenience and utility.

To build the solar and bilge system, you will need the components listed below. Obviously, actual prices and availability may vary over time. I make no claims about the integrity of the website vendors listed here. I list them for reference purposes only, to aid you in tracking down particular components for the lowest prices I could find at the time this article was written.

  • Rule 500 gph non-automatic electric bilge pump ($20.49) West Marine, model # 375196
    An automatic version of this pump is also available ($47.99, model # 491928) which has an automatic-detect function that cycles the pump to check for water every 2.5 minutes or to turn it on manually for constant-on pumping. Since the automatic-detect function is not really very practical for kayakers, get the manual-only version of this pump for half the money. If, however, you're dead set on buying the higher-tech, automatic-capable pump, make sure you get a waterproof single-pole, double-throw (SPDT) switch with a center-off position instead of the single-pole, single-throw (SPST) switch listed immediately below; otherwise you will not be able to select between the automatic-detect and constant-on pumping modes.
  • waterproof single-pole, single-throw SPST switch (to turn the bilge pump on and off, $15.99) West Marine, model # 1945864
    If you use the manually-activated Rule pump, you'll need a single-pole, single-throw (SPST) toggle switch; if you use the automatically-enabled Rule pump (see above), you'll need a single-pole, double-throw (SPDT) toggle switch with a center-off position (basically, a three-position switch), which will enable you to turn the pump "on (manual)", "off", or "on (automatic)". Make sure these switches are waterproof, or else waterproof them yourself by coating them thoroughly in liquid rubber and screwing a rubber boot over the toggle. Also, it is not mandatory that the switch be a toggle switch, assuming you can find another type of waterproof switch (rocker, push-buttom, etc.) with similar wiring attachments and switch positions.
  • two rolls of Ancor 16-gauge marine-grade wire (one red, one black, $4.99 each) West Marine, model # 106179 (red, 25 feet) and 106187 (black, 25 feet)

  • Uni-Solar FLX-5 flexible 5-watt solar panel ($77.50) Northern Arizona Wind & Sun

  • SunGuard 4.5 amp charge controller (to regulate solar panel charging output, $28) Northern Arizona Wind & Sun

  • Pelican 1120 case (outer dimensions: 8 1/4" x 6 1/2" x 3 5/8", $18.85) All-Pelican-Cases-4-Less.com, model # 1120
    IMPORTANT: The Pelican 1120 case will only work if you can find the exact PowerPatrol battery I recommend below or smaller. Otherwise, the system will not fit inside this particular model Pelican case and will require a slightly larger model. If in doubt, collect all of the other system components first, then determine the size of the waterproof enclosure you will need.
  • Power Patrol 12V, 5Ah sealed lead acid (SLA) battery (dimensions: 4" x 3 1/2" x 2 5/8", $21.99), www.interstatebatteries.com, model # SLA1055

  • 10 "AA" battery tray ($2.30) www.thomas-distributing.com, order # MS-BH-10-AA

  • heavy-duty 9V snap connector ($2.49 for a pack of 5) www.radioshack.com catalog # 270-324

  • double-pole, double-throw (DPDT) heavy-duty toggle switch with center-off position ($2.99) www.radioshack.com catalog # 275-666

  • crimp-on wire butt connectors, crimp-on female disconnects, heat-shrink tubing, GOOP waterproof glue/sealant (as needed, check your local hardware store)

Check out the Wiring Diagram for a closer look at how to wire each component of the solar-powered battery pack and bilge pump system. By wiring the system in this manner, you can use the SunGuard charge controller to regulate the solar current to both the core battery and the 10 "AA" batteries. Flip the DPDT switch one way to charge the core battery, or flip it the other way to charge the "AA" batteries. The 2.5 amp fuse should be wired as closely as possible to the positive terminal of the core battery in order to protect the rest of the system (especially the bilge pump) from power surges. The weakest link in this system is the SPST or SPDT switch that turns the bilge pump on and off. Use a heavy-duty waterproof switch and position it somewhere that will minimize water contact and corrosion but still allow quick access for easy operation.

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© 2006, Wesley Kisting


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