KiloVault HLX+ Batteries tested, power aplenty

Each of the last three summers my family and I have loaded ourselves into our RV, Harvey, and hit the road. It’s an opportunity to see friends and family and to escape some of the hottest months of south Florida’s summer. It’s also an opportunity for me to test new systems installed on the RV. Last summer, I installed an all Victron DC house power system. This summer, I installed and now tested two of KiloVault’s HLX+ 3,600 watt-hour batteries. I’m pleased to report the Victron system and the KiloVault batteries performed flawlessly this summer. The system served to show what’s possible in off-grid living on the water or on the road, including running one of our air conditioners via the inverter and batteries.

The plan

From the factory, Harvey came with four GC2 6-volt golf cart batteries in a two series by two parallel configuration. With each 6-volt battery rated at 230 amp hours this provided a total capacity of 480 amp hours at 12 volts. Because these batteries were flooded lead-acid, I didn’t run them down below 50 percent state-of-charge (SOC), meaning I had 230 amp hours of useable capacity at 12 volts.

I replaced the four GC2s with two KiloVault 3600 HLX+ LiFePO4 batteries. I’ve previously written up the HLX+ line of batteries and run down their features and impressive build quality. But, just as a reminder, HLX+ batteries are available in 100 amp hour ($699), 200 amp hour ($1,345), and the 300 amp hour ($1,895) size I’m installing. All sizes feature heating, Bluetooth communications, push-button charge level indicators, and communications ports for future enhancements.

These batteries will be installed in parallel for a total of 600 amp hours. Running them down to 20 percent SOC will give me a usable total of 480 amp hours. That’s more than double the capacity of the previous batteries. I’d already made significant changes to the DC system to get it ready for lithium batteries. I outlined those upgrades in my entry from last summer, but to summarize I already replaced the original Magnum inverter that lacked LiFePO4 charge profiles and replaced the relay connection between the chassis and house batteries with an Orion DC-DC converter. Mylast charge source is a Victron SmarSolar 100/50 which is also ready for LiFePO4 charge profiles. So, all my charge sources are easily reprogrammed for LiFePO4 profiles.

Physical install

The factory location for the batteries on Harvey is under the entry stairs, a location I’ve often found inconvenient. Well, as it turns out, one battery wouldn’t fit in the space, let alone two. At 20.5 inches long by 11 inches wide and 9.25 inches tall, two HLX+ batteries are a lot bigger than the four 10.25 x 7.125 x 10.875 inch tall GC2s they replace. On the one hand, I wish the batteries were a little smaller, but on the other hand, I think their size and weight come from their build quality. I had a chance to see that quality in the teardown battery KV provided.

At 88 pounds each I needed to find a location I could mount the batteries that would stand up to the weight of the batteries, offer sufficient vertical clearance and not subject the batteries to potential damage. The location I selected is in one of the under-body storage compartments. The batteries are located under the center of the RV in an area with reduced vertical clearance. There’s just enough room for the batteries and they’re still close to the original spot, so cable routing isn’t too different.

Making the connections

My original plan was to reuse the RV’s existing power distribution. That plan didn’t survive a careful inspection of the wiring. I realized the fuses wouldn’t be adequate for the energy potential of the new battery bank. I couldn’t find specific standards for installing lithium batteries on an RV. So, I decided to follow ABYC’s E-10, E-11, TE-13 (and now E-13). Based on the size of the battery bank ABYC’s standards require the primary battery fuses to have a 20,000 amp interrupt capability (AIC). Class T fuses are the only commonly available option to meet the requirements, so that’s you see in the picture above, with clear covers.

Interestingly, I think this might be the only install I’ve ever done where I’ve been able to get close to placing overcurrent within 7 inches of the battery. In addition to the class T fuses on each battery, I moved the primary fusing for each load to MRBF fuse holders and fuses hung off the positive bus bar. In the photo above, the cover is on the bus bar so you can just see the fuses poking out from under the cover.

Immediately below the positive bus bar, there’s a Blue Sea circuit breaker for the connection to the solar controller. Just below that breaker is the Victron SmartShunt battery monitor.

Putting the batteries to work

VRM’s battery history for the HLX+ batteries

Armed with new and improved batteries, my family and I hit the road. We travelled for a little over six weeks to locations with power availability ranging from 240 volt, 50 amp to absolutely none. In that time we consumed about 10,000 amp hours from the batteries. The lowest voltage the SmartShunt recorded from the batteries was 12.75 volts. As I’ll cover later, that’s despite some pretty massive loads on the batteries.

The screenshots showing the operation of the batteries all come from Victron’s VRM portal. I’m using a Raspberry Pi running Victron’s Venus OS to control the system.

I wish there’s more I could say about their general performance, but sometimes no news (or at least not much news) really is good news. The batteries have done what I hoped they would. When power is needed, they’ve provided it. When power is available to charge them, they accept it. Like every LiFePO4 battery I’ve tested, the batteries accept charging current as fast as it’s provided, right up until about 95-97 percent SOC.

I’ve found that LiFePO4 installations require significant design and planning to be properly and safely installed. But, with a successful design, operations of LiFePO4 batteries seem to fade into the background. The characteristics of the batteries mean they don’t need special care. The batteries go about their business happily and quietly.

Equipped with 700 watts of solar, Harvey can go for days without shore power. On sunny days, the batteries achieve full charge by about 3 pm. Cloudy days often mean dipping into the batteries a little further. With lead acid batteries, that’s something that I monitored carefully to avoid hurting the batteries with excessive partial state of charge (PSOC) cycling. PSOC cycling refers to discharging and charging the batteries without reaching a 100-percent state of charge. Fortunately, LiFePO4 batteries don’t have any trouble with PSOC cycling.

Turning up the load

After great success running the DC system of the RV and several AC loads through the inverter, I decided to turn up the load. The single largest loads on the RV are the two rooftop air conditioners. These are 13,500 BTU each and draw about 12 amps of AC power once they’re running. I don’t have soft-start kits on the air conditioners, so their inrush (startup) current demands are quite a bit higher. In fact, I measured inrush at about 24 amps. Those loads are right on the edge of what the 2,000-volt-amp MultiPlus I have can handle. At times, starting up the AC was enough to trip the overload protection on the inverter. But, more often than not, the inverter held up to the inrush load and the AC started and ran perfectly.

As you can see in the top left chart above, starting the inverter drew 184 amps as measured by the SmartShunt. Impressively, even under this sizeable load, the batteries were still pumping out 12.8+ volts. With 700 watts of solar and 480 useable amp hours of battery capacity, I found the load of one air conditioner, a household refrigerator and a few other small loads would deplete the batteries in about 6-7 hours. That time is highly variable depending on outside temperature and how often the air cycles on and off. If I were sizing the system to run the AC on a more permanent basis, I’d probably want more like 14,000 watt hours of capacity, or double my current capacity.

The future: communications, updated mobile app, and E-13

The communications ports on the HLX+ batteries allow them to link to the KiloVault bridge

KiloVault has been promising a communications bridge that leverages the communications ports on the batteries for some time. In my recent conversations with KiloVault, I learned they plan to launch the bridge at next week’s Solar Power International show. I’m also pleased to report that KiloVault says they’ll be updating the mobile app at the show as well. As I noted in my previous writeup, it’s the one aspect of the batteries I thought was underdeveloped.

ABYC ratified E-13, a standard for the installation of lithium-ion batteries on boats at the end of July. The standard doesn’t take effect in July of 2023, but I think it’s prudent to start looking at compliance now. From what I can see, the HLX+’s only potential E-13 compliance issues are in the documentation requirements. I certainly don’t expect they will have any troubles updating their documentation by next summer to meet the standard’s compliance date.

Final thoughts

I really don’t have anything negative to say about the HLX+ besides my gripes about the mobile app, and that will hopefully be remedied very soon. I think the price is fair and the performance is strong. However, the testing isn’t over. I’ve consumed 10,000 amp hours of power from the batteries. At 80 percent depth of discharge (DOD), the batteries are rated for 5,000 cycles. With two 300 amp hour batteries that means an 80 percent DOD cycle is 480 amp hours. Multiply that by 5,000 cycles and you realize these batteries should deliver 2.4 million amp hours. So, I’ve used 0.4 percent of their rated life. I’m here to tell you it’s been a very positive 0.4 percent. But, I’ll keep testing and report back if anything changes in the next 99.6 percent.

Ben Stein

Ben Stein

Publisher of, passionate marine electronics enthusiast, 100-ton USCG master.

6 Responses

  1. Grant Jenkins says:

    Thanks Ben, good write-up. Sounds pretty trouble free. Couple of things – You have a typo near the beginning – “this provided a total capacity of 430 amp hours at 12 volts….” I think you meant 460 amp hours.
    Also – is there a particular reason you used separate positive/negative cables from each battery to the bus, instead of cabling the two batteries together, positive-positive, negative-negative, and then run single cables from there? Just curious….

    • Grant, I don’t know Ben’s thoughts, but the usual reason for the arrangement he used is to equalize the resistance for each battery, so both will equally share the loads. Jumpering A to B then from B to the load buss means that A will have slightly higher resistance, and will contribute less to the load. Over time, this can be a serious issue, as the effect is cumulative.

      S/V Atsa

      • Grant Jenkins says:

        Thanks Hartley, I’m familiar with the concept, but I thought equal length jumpers in this configuration would nullify that. Perhaps not.

    • Ben Stein Ben Stein says:


      First, you’re right, that’s a typo, though I think at 80 percent of 600 it should be 480 amp hours. I’ll go fix that.

      With two batteries and short runs I think the way I did it is equally efficient to battery interconnect links and then coming off the positive of one battery and the negative of the other. Either way, I needed four cables. I was careful to keep cable lengths identical between the batteries and so far I’m seeing pretty equal rates of discharge. I believe it’s basically method 3 in the SmartGauge article on cabling banks (

      My understanding is that what you’re trying to accomplish is equal length cabling to each battery. As long as you can get that done, you’re in good shape.

      -Ben S.

      • Carl Nelson says:

        I installed five Kilovault 300AH batteries a year ago on my sailing cat. Couldn’t be happier with them. As Kilovault requires, I used equal length cables as you did. After a year of use the app shows each battery as still having more than the rated amp hours and the internal cells are so well balanced that they are within .01 volts of each other. So they are charging and discharging in perfect sync. I think equal length cables may be the key to lithium battery long life. If you are installing more than two batteries in parallel the old LA method of a positive cable at one end of the bank and negative at the other end causes LFPs to charge and discharge unequally due to their low internal resistance. Or so I’m told.

  2. Grant Jenkins says:

    Thanks Ben. I’m sure it’s fine – I was just thinking you could have saved a little cable and also eliminated one of those Class T fuses/holders, which aren’t exactly cheap…
    The Smartgauge link is great information, which I’d seen before – I do note, however, their statement near the end, “Finally, if you only have 2 batteries, then simply linking them together and taking the main feeds from diagonally opposite corners cannot be improved upon. ”

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