Review By Dean Bielanowski  AmpTech Website -

AmpTech D87L 120Ah 12v Deep Cycle Battery

By Dean Bielanowski

Just recently I fitted a 12v electric trolling motor to my small open boat. I wanted it so I could sneak around more quietly in the hunt for estuary fish, but also for stocked impoundments (dams) in my area where normal combustion outboard motors are not permitted (for pollution reasons). Additionally, there are many other uses for 12v batteries, particularly if you have an inverter, which will convert 12v to 240v power to run a lot of smaller items like battery/phone chargers, small fridges, lights, the list goes on! But primarily, this battery would see most action in my small boat. I digress...

So I grabbed myself a decent transom mount 54lb electric outboard, but of course, you need a decent battery to power it. 12v batteries come in many different sizes and capacities, even many different shapes too! From small capacity 2Ah batteries up to 300Ah, and even more! But of course, the larger the battery, the larger the cost, and physical size and weight, so on most small boats you need to find a compromise between these factors. You must also consider the power of your outboard. A 54lb electric motor will consume more power than a 28lb motor. For the 54lb outboard I chose to review a 120Ah battery, and this battery is the subject of this review.

AmpTech D87L 120Ah Deep Cycle Battery

AmpTech D87L Battery
Now, some people say you can use a normal car battery to run your electric outboard or other 12v appliances or inverters etc, and of course, you can do this. However, there are several important issues to consider...

  • Car batteries are generally not deep cycle batteries, and they are designed mostly for motor starting, providing a lot of power in a short amount of time. An electric outboard requires a good amount of power over an extended amount of time.
  • Car batteries do not like being run down to low battery levels and then recharged on a regular basis. Doing so greatly reduces the battery's service life. Deep cycle batteries on the other hand are less prone to failure when being deeply discharged and recharged on regular occasions, and running an electric outboard for any extended length of time will draw a lot of power from your average sized 12v battery. At full speed, my 54lb thrust electric outboard can draw up to 57 Amps according to the outboard manual.

Given this, you will find most experienced boaties or those with extended use 12v power needs will advise to opt for a deep cycle battery. They may cost more in the first instance, but over time, they will definitely save you a lot of money.

Heavy Duty Battery Case

Workings of the Battery
Batteries are not all created equal. Indeed there are many types, from regular lead acid, to valve regulated lead acid (absorbed glass matt and Gel are common), and calcium. Each probably have their own pros and cons. The AmpTech D87L is a standard lead acid battery, but with new Expanded Grid Technology (EXG) incorporated. I'm not going to go into great detail of how batteries actually work, but I will mention the basics here.

Essentially, a battery is an power storage device which uses a reversible chemical reaction to store energy. It is called a lead-acid battery because it utilizes a number of lead plates surrounded by sulphuric acid (diluted). When electrical current is applied to the battery (via an electric charging device), the battery converts this into potential chemical energy for storage, the process of which is reversed to provide electrical current when needed.

A battery unit has multiple smaller cells containing the lead (or other) plate and acid solution and each cell generally holds a voltage of around 2.12 volts when fully charged, with a standard voltage of around 2 volts. Group six of these cells together in series, and you have a "12 volt battery" (even though when fully charged it puts out closer to 13 volts).

A deep cycle battery generally has thicker lead plates which allows it to be more tolerant to deep discharge cycles. While they can also be used to start automotive or marine engines, they typically do not provide the same level of power as quickly as a normal cranking starter battery. As a result of the thicker lead plates, deep cycle batteries generally weigh a lot more as well (lead is a heavy metal). Now, on the flip side, many new battery plates are now being created with different materials, and this battery under review is one of those. It features the Expanded Calcium Grid Technology...

Expanded Grid Technology (EXG)
EXG is a new way of making battery plates that offer more consistent power output, longer life and better performance in a wider range of use and climatic conditions. I don't manufacture batteries, nor do I claim to be a world expert on them, so here is a description of EXG taken from the battery manufacturer's website. It certainly explains it better than I could!

EXG Technology is an advanced, fully-automated process that uses continuous rolled strips which are then compacted under high pressure, sliced, expanded and cut into grid strips. Compared to ordinary gravity-casted grids, EXG Technology calcium grids have a more compact grain structure and are inherently stronger. This makes them less prone to heat and corrosion and ensures more efficient current conductivity and cranking power, as evidenced by the battery’s superior specification ratings. On top of that, the unique chemical composition of the EXG calcium plates extends both the battery’s useful life and shelf life and significantly reduces water loss. And because EXG plates are engineered to be shorter in height, the battery has more space for acid, thereby completely eliminating the need to top up.

In saying this, however, the D87L battery does have battery cell caps that can be removed to inspect acid levels if required.

Removable cell plugs for checking battery fluid levels

D87L Specifications and Use/Performance
Firstly the D87L features a 120 Amp Hour capacity measured at a 20 hour discharge rate. Typically, batteries are measured at a constant discharge rate Vs capacity. So if you place a higher drain on a battery that may consume total capacity in say 10 hours, the total Amp Hour capacity measure will be reduced. The D87L, for example, has a 96 amp hour capacity at a 5 hour discharge rate. Its a bit confusing, but really you should just consider it as a standard measure from which to compare similar batteries. In theory of course, the battery should be able to handle a 1 Amp load for 120 hours, a 2 Amp load for 60 hours (2A x 60h = 120Ah etc) but as mentioned above, high current loads reduces capacity faster, so total up your expected Ah rating of all your devices you plan to hook up to the battery and get a rough idea of how long the battery may run them for before you decide on a specific capacity.

Specification sticker. Note max recharging voltage of 14.8v

The D87L battery measures 333mm in length, 173mm in width and 241mm in total height (including terminals). It fits snugly but neatly into standard "large" plastic battery boxes, which is what I have this battery stored in, but be sure to check dimensions of battery boxes to ensure it will fit before purchasing. The battery box (which is not included of course) does provide a means of carrying the battery, however, the AmpTech D87L battery does have its own folding carry handles for moving the battery around. These come in handy if you regularly have a need to remove a battery from your boat/RV/caravan/car etc for recharging. They fold back down flat so as to not increase the total physical size of the battery too. A handy feature, and perhaps a necessary one given the battery weighs in at just over 30kg. It is a big battery, but a solid one also.

Standard top terminals. Each is color coded and also named with symbols

Carry handles allow easy transportation. They fold down flat onto the battery casing.

On top of the battery you will find standard tapered battery terminals found on most automotive units. You may or may not need to buy the various available terminal fittings for connection of your devices. For my electric outboard, I use 100 Amp plier-style clips as my electric can draw up to 70 Amps under load. These clips also allow quick hookup and removal of cables as required. Your needs will probably vary depending on use. The battery has a positive left terminal configuration if that makes any difference for your needs. For me it doesn't but retro-fitting a battery to an existing setup requirement may call for it. Additionally, and as mentioned above, the cell caps on top allow access to each battery cell to check fluid levels. While the EXG technology should greatly limit the need to check these, they are handy to be able to access to check the charge state of your battery with a hydrometer if required (generally the most accurate way to check battery charge). Also, ensuring the fluid levels are correct at least a couple times a year will ensure maximum battery life and performance.

When it comes to charging the D87L, you are going to need... well want... a decent multi-stage battery charger. Sure, you can charge manually with a single-stage charger as long as you are prepared to keep your eye on it all the time to ensure it doesn't overcharge, which can readily destroy a battery. A quality multi-stage charger is definitely easier to use and will prolong battery life if it includes a float charge setting (most do). The D87L has a maximum charging voltage of 14.8 volts, so check your charger does not exceed this figure when in bulk-charging mode for safety reasons. I have been using a 7-stage 12v charger with a maximum current capacity of 16 Amps with the D87L. You can use lower current chargers but I wouldn't want to go lower than 8 Amps. The lower the current, the longer the battery takes to fully charge and if you go too low, the battery may never really fully charge to maximum capacity, which too can affect service life. I'd recommend a 16 Amp 4-stage or better charger with float charge mode. Again, spending that little extra now will save you a lot more later. Keeping the battery on the charger in float mode while not in use will greatly extend a battery's service life, sometimes as much as 300% longer.

Ok, so with a fully charged battery, and bear in mind that it can take numerous charge/use cycles for the battery to reach full storage capacity, I placed the battery in my boat and headed out for some fishing action. Once I reached my favorite spot in the bay, I switched off the combustion engine and lowered the electric ready to hunt for some fish, with the aid of my sounder. While I have a separate, smaller battery for my sounder, it too can be hooked up to the deep cycle D87L if needed! After a bit of trolling with the electric outboard I came across some promising sounder readings. Dropped a line and shortly after bagged a nice sized bream. After not many more bites I searched around the nearby river mouth using the electric so as to not scare any fish away. After about 20 minutes of trolling at half speed, I came upon some more blips on the sounder. Dropped a line and another bream, slightly smaller this time. Got a touch on something else but I lost it early. The outboard has a 10-LED battery charge meter on top and it was showing full charge at this stage.

Onto the next spot a little further up the river and this time I switched rigs to try and bag some whiting. About another 30 mins of trolling at various speeds and I had some readings on the bottom. But to no avail this time. Up comes the electric, and off further up the river with the combustion engine on a flathead catching mission. I usually have several rods fited out for each different type of fish I am hunting for. I parked the boat around my favorite river flatty spot and dropped the electric and spent a good hour or two trolling around the vicinity, sometimes up at full speed to get to the other side of the river bank. About 35 minutes worth of trolling around here at a guess. Battery meter now showing 9 LEDs which is fine. One keeper flatty and back to the ramp to go home.

Put the battery on the charger and it indicated at 80% charge remaining after a good days fishing and probably about 1.5 hours of varying speed trolling motor use all up (my charger has a charge gauge). Can't complain! I verified the figure with a hydrometer on the cells which gave a similar reading). Overnight on the charger (mostly in float mode) and off I went for some freshwater action in the local impoundment. It's electric motors or oars only in this dam, so a good chance to test out the motor and battery. It took about 25 minutes to reach secret spot X on the dam at 3/4 speed on the electric and the charge meter had dropped a LED light from full. Fair enough. Probably a fair bit of battery use there. The next few hours involved quite a lot of trolling about over short and longer distances trying to find another secret spot X after the first secret spot didn't earn its title, it seems. Nothing secret about it this time out. Another LED down, and then another. The battery is starting to deplete now, but I have done quite a lot of running around and maneuvering at this point. Finally got onto an Aussie bass using a soft plastic. But soon back in and lures out again looking for another. My fishing buddy latched onto about 3 more in this one spot. He's probably a better fisherman than me, or maybe he just chose the right lures on the day. With sunlight diminishing, it was time to head back to the ramp, about a 30 min trip this time at half speed. Upon getting back tot he ramp I had dropped another 2 LED lights on the charge indicator of the electric motor, which indicates about 40% remaining. Back on the charger overnight and its 100% charged once more. I did quite a bit of trolling on the dam that day and the battery had enough capacity to handle it without too much drama.

The next outing I tended to use the electric for actual trolling of surface baits up and down the river. With some Halco Twistys and Pilchard lures, I managed to grab a couple tailor which was pretty exciting. I hadn't really done much trolling before because of my aging 2 stroke outboard doesn't seem to like trolling for any extended period of time. The electric however is made for this and pushed along at a nice steady pace, and with relatively no noise. Again, plenty of power available from the battery.

Outings since then have produced mixed results fishing-wise. Battery-wise, after about half a dozen more charge/use cycles, I am seeing slightly more capacity evident, as far as I can tell that is. I would explain those outings in more detail, but honestly, on most of those I didn't even get a nibble, let alone catch anything so I don't want to bore you!

Ultimately, it was all about testing this battery out, and I am happy to say that it did, and continues to fulfill my needs as a reliable deep cycle battery for powering my electric outboard motor. And given its retail price is lower than many of its competitors, it does seem to offer very good value for money. Of course, at this stage, having only owned and used the battery for about 6 weeks, I can't comment on long time durability, but I am sure that with my quality charger keeping the battery constantly topped up I should get many years use out of it, and for the retail price of around $250 for the D87L, I feel it offers great value for money.

On the flip side, and perhaps partly relevant, the battery I use to power my boat sounder/radio and nav lights is also an AmpTech battery (smaller 18Ah) and it has given me around 14 months of reliable use now and still going very strong.

The AmpTech D87L does come with a 12 month warranty and my dealings with the company (Supercharge batteries) have been very positive to date and they exhibit good customer service with an extended service and warranty network, so sourcing assistance or filling warranty claims should not be a problem in most areas of Australia if you happen to need it. The AmpTech deep cycle batteries also come in several other sizes/capacities from 40Ah up to 220Ah.

Overall the D87L performed very well and up to expectations. Definitely worth considering if you have a need for a deep cycle 12v battery, whether it be for fishing, camping, caravanning or any other battery use. I have also read many other posts from other owners of AmpTech batteries who are happy with their purchase, so for now, the outlook is looking positive!

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