Epoch Batteries, elegant drop-in LiFePO4

Good design matters, even for a product you probably won’t spend much time admiring. Epoch batteries’ line of LiFePO4 has design covered and an attractive list of features. But the big question is, are these batteries more than just a pretty face? I’ve been putting a couple of their 100 amp-hour, 12-volt batteries to the test, and it sure looks like they have the goods to back up the design.

Epoch Batteries is a division of RoyPow energy. I recently learned Eve, one of the largest manufacturers of LiFePO4 cells, owns RoyPow. So, it’s safe to say there’s plenty of LiFePO4 experience and expertise available for Epoch to draw on in designing their batteries.

Epoch offers a range of batteries in 12, 24, 36, and 48-volt options. Each voltage is available in 50 or 100-amp-hour capacity. The 12-volt batteries support up to four series and four parallel connections. The remainder of the voltages allow two series and four parallel connections. The four parallel limit for the 100 amp-hour, 12-volt battery may be an issue for larger installations. Epoch says they’re working on higher-capacity batteries. I, for one, would love to see a 400-amp-hour, 12-volt battery in the 48-volt, 100-amp-hour case.

The battery I’m testing currently sells directly from Epoch for $599.00. That makes the battery about $100 cheaper than the similar capacity battery from Kilovault and a few hundred cheaper than one from Battleborn. There are certainly cheaper batteries out there, but I don’t think you will find anywhere near the quality of Epoch’s batteries in those less expensive batteries.

Features

Epoch’s batteries come with a pretty complete range of features. The batteries’ BMS (battery management system) has a Bluetooth radio to easily see the batteries’ status, history, and any warnings or faults. Epoch’s batteries are heated, IP67 certified against dust and liquid ingress, and feature easy mounting feet with screw holes. IP67 means the batteries can be submerged to 1-meter for 30 minutes. Additionally, there is a CANBus external communication port on the side of the battery. The top of the battery includes a pressure relief valve to normalize pressure inside the sealed battery and a power button that puts the battery into a sleep state and wakes it up.

Epoch also includes a 10-segment LED battery gauge that plugs into the communication port and displays battery SOC (state of charge) in 10-percent increments. The gauge connects via the CANBus port, so if you’re using CANBus communications, you won’t be able to use the gauge. I tried connecting a test battery to the VE.Can port on a Victron GX system and wasn’t able to establish any communications between the battery’s BMS and the Victron system. Epoch reports they’re working on testing communications but didn’t have any information to provide yet.

Performance

The 12-volt, 100-amp-hour battery I’m testing is rated for 120 amp continuous discharge and 50 amp continuous charging. During my testing, I widely exceeded these values and eventually saw the BMS’ protection kick in, but not until I’d blown past those ratings by large margins.

Although my 12-volt battery is advertised with a 100-amp-hour capacity, it contains four 105-amp-hour cells in series. So, the actual capacity of the unit is 105 amp hours, as I’ve been able to confirm in multiple rundown tests. In fact, as the picture above shows, a 20-hour rundown test performed at 5-amps yielded just shy of 110 amp hours. Consider that many lead-acid batteries fail to meet their rated capacity, even when brand new. That makes these batteries, including a bonus 10-percent capacity, sound pretty darn good.

Consistent with the behavior we typically see with LiFePO4 batteries, these batteries show a very flat voltage discharge curve. The graph above shows the results of a 20-hour rundown test performed at five amps. That’s the 20-hour discharge rate for these batteries and we can see the typical nearly flat voltage line until we reach near zero-percent SOC. In fact, at just five-percent SOC, the battery still provided 12.6 volts.

Massive load handling

That stable voltage (and impressive load handling) continues as the loads increase. In the case of the chart above, the loads have gone way up. I’m using a 2,000VA inverter and a heat gun to generate over 150 amps of load. Consider that’s a more than 1.5C (1.5 times the battery’s rated capacity) load. If allowed to continue, the battery fully discharges in under 40 minutes.

You may have noticed that the voltage shown in the VRM graph above is pretty low, at about 11.5 volts. That’s a limitation of how I’d set up my test bench. I have the voltage probe of the SmartShunt on the bus bar rather than directly connected to the battery. The result is the SmartShunt sees the voltage drop across the wiring of my test bench from the 150+ amp load. The shot of my meter above shows the voltage at the battery terminals. Maintaining 12.5 volts under a 150 amp load is an impressive performance for a single battery, well over its ratings.

The app

In my review of the KiloVault HLX+ batteries, I liked nearly everything about the batteries, until I got to the app. I felt it left a lot to be desired and seemed like an afterthought. Not so with Epoch’s app. The app is attractive and functional. It also gives a lot of insight into the battery’s operations.

At a glance, one of my favorite pieces of information is the cell voltage difference or cell delta. Cell delta, especially over various states of charge and at differing loads, gives you insight into how well they matched the individual cells. The results from my testing indicate an excellent cell match. In fact, I don’t think I’ve seen more than 0.015 volts difference at any time.

Fault display is a weakness of the app. The faults are displayed without any information about the fault and often in difficult-to-decipher acronyms. Fortunately, the fix is pretty easy. Decoding acronyms and making the faults clickable to display more contextual information would be a nice improvement. I noticed another oddity: the battery app displays a fully charged fault when the battery reaches 100 percent SOC.

The app did show behavior I haven’t seen before from a drop-in battery. The last screenshot above shows a fully charged “fault.” In addition to showing the fully charged condition as a fault, the battery stops accepting charge when fully charged. Unfortunately, that’s not reflected by the charge and discharge MOS status indications. In fact, I never saw those change during my tests.

Tear down

Tearing down an Epoch battery only requires removing the 12 hex-head screws from the top of the case. With those screws removed, the case and top easily separate. The top has a rubber gasket that seals the battery from dust and water.

Upon unboxing the batteries, one of my first observations was that the case was larger than I expected for a 100-amp-hour battery. Removing the top shows there’s quite a bit of extra room around the battery. I’m not sure if there’s enough room to pack double the capacity in there, but I think something like 160 amp-hour cells would likely fit.

Aside from the extra space, I also noticed high-quality construction and impressive battery serviceability. The cells and BMS mount on a tray screwed to the case. With those screws removed, the tray removes and the battery is easily seen and explored.

I’ve disassembled several batteries, and so far, I haven’t encountered one that gives me pause. But I also haven’t encountered one put together this well. Nearly everything about the battery is top-notch and exceeded my expectations. I will detail several of the high-quality features I noticed, though I may not be able to capture all of the features.

Cell compression

Compressing cells keeps them from swelling under charge. Not too many batteries I’ve seen have robust cell compression. This may or may not be a problem, depending on the charge rate the battery experiences. But, allowing cells to swell during charging will damage them. That damage may result in reduced performance or even premature failure of the cells. Current Connected has a good explanation of cell compression. Epoch uses large aluminum braces on each end of the pack with robust strapping holding compression on the cells.

Temperature sensors

Each Epoch battery contains six temperature sensors: two on top of the battery pack, one on the underside of the positive and negative posts, one on the BMS’ FETs, and one to measure ambient temperature. The sensors under the terminals are especially useful as they will shut the battery down if a poor connection produces too much heat. Without those sensors, that poor connection can easily generate enough heat to damage the battery, if not cause a fire. Interestingly, the app only displays four of the temperature values. The terminal sensor values don’t display in the app. Additionally, I heated a terminal hot enough for the BMS to shut down discharge current, but that fault also didn’t show in the app.

Labeling and insulation

In another indication of the care taken with engineering and construction, each wire and connection is clearly labeled and all the wires are carefully insulated and protected. Wire protection extends to heat-resistant, color-coded, fabric tape applied outside the current carrying conductors. Those conductors use 200-degree celsius insulation and are all doubled-up 8 AWG wires.

Heat management

The BMS on my 100 amp-hour, 12-volt test battery carries a 120 amp discharge rating. To manage the heat generated by that relatively high discharge, the BMS has a standard heat sink on the front covering the area of the BMS with the balancing resistors.

But, on the back of the BMS, a large, fluted heat sink provides significant cooling to the BMS’ 24 FETs. In my testing, I saw this heatsink get quite warm, but it seemed it was doing its job of wicking heat away from the FETs.

Let’s also look at the Epoch’s BMS compared to units from Kilovault, Lithium Pros, and Overkill Solar. At 120 amps continuous, the Epoch BMS handles 20 more amps than the others. The Epoch BMS appears similar in size and construction to the Lithium Pros and Kilovault. Like those two, the design of the BMS better dissipates heat than the JBD/Overkill Solar BMS.

Thermal results

At the time the thermal image above was taken, the battery was being discharged at over 150 amps. As you can see in the images above and below, the BMS was certainly working and that generated significant heat from the FETs.

The battery ratings support a continuous discharge of 120 amps and 200 amps for up to 30 seconds. I subjected the battery to a continuous discharge of roughly 160 amps. That’s pretty obviously over what the battery’s ratings and yet, the battery never shut down. I used a heat gun to get the temps over 200 degrees to trigger a shutdown. I suspect my potentially abusive testing may have shortened this battery’s life. But, with my testing complete, I performed a 20-hour run-down test again. That yielded a capacity of 108 amp hours. Still in excess of the 100 amp-hour rating Epoch advertises and above the rated capacity of the cells.

Final thoughts

These are some of the nicest drop-in batteries I’ve tested. I’ve gotten my hands on some high-quality batteries and these rival the best of them. A few small issues in the app should be addressed, but none proved problematic to the battery’s operation. A review of ABYC’s E-13 lithium standard shows that Epoch is extremely well-positioned to meet not only the current requirements but also the notes and recommendations. I’m really hoping Epoch will expand their range with higher capacity units and increase the physical density of the batteries. But, all that said, I can recommend these batteries without any hesitation.