Upgrading the House Batteries

This post is a work in progress. I am updating as things move along.

Molly came with two 270 Ah AGM batteries from Mastervolt(1). These are located in the battery box which is low and in the center of the truck, literally between all four wheels. And although these batteries have served us well and generally g0t the job done, on a few emergency occasions we have had to start the engine and charge them from the alternator. This is typically when we are under trees for several days or when snow covers the solar panels.

So, we decided it was time to upgrade our house batteries to higher capacity and at the same time change the technology from AGM to Lithium Iron Phosphate (LiFePO4). We choose to install three 200 Ah Cold Rated HLX+ series batteries from Kilovault.

Based on the before and after specifications, the new batteries offer twice the capacity, operate in the same temperature range, take about the same space and are half the weight. The negatives of these lithium batteries is that they are about twice the cost of Mastervolt AGMs and the maximum current draw is less at 450 Amps vs 510 Amps for the AGMs.

Before

Total Capacity : 540 Ah with approximately 270 Ah usable. For AGMs, the recommended deep of discharge is 50% to maintain the life of the battery.

Operating Range: –20 to 55ºC / –4 to 131ºF(2)

Space Required: 522 mm x 536 mm x 226 mm (LxWxH)

Weight: 146 kgs (322 lbs)

Maximum Continuous Current Draw: 255 Amps

After

Total Capacity : 600 Ah

Operating Range: –20 to 55ºC / –4 to 131ºF

Space Required: 505 mm x 517.5 mm x 255 mm (LxWxH)

Weight: 71 kgs (178.5 lbs)

Maximum Continuous Current Draw: 150 Amps

Battery Box

There were two concerns driving our decision to choose the Kilovault batteries. And both of these concerns involved the battery box.

Our battery box is located on the outside of the truck, and when it gets cold outside, well, it also gets cold in the battery box. And typically lithium batteries do not like to be charged when their internal temperature is below freezing. The Kilovault batteries have an internal heater which automatically turns on to raise the temperature, and once a suitable internal temperature is achieved, the Battery Management System (BMS) then allows charging to occur. Other companies like Lithionics Battery, Battle Born and Relion all offer similar cold rated and self heated batteries, so this is not unique to Kilovault. It is also possible to heat the battery box independently, but this is more hassle and requires space in the battery box for the heating equipment.

The second challenge with of battery box is its compact size and sturdy construction. Whatever batteries we choose need to fit into the battery box, as the size of the box is not going to be changed as this would be a huge effort. The available space in the battery box is 560mm x 537mm x 270 mm (LxWxH).

After searching the internet for many hours and considering many options, the Kilovault product allowed us to fit 600 Ah into the available space. Our battery box is also not fully weather sealed, so dust and water can get in there. The Kilovault HLX+ series batteries have an IP55 rating, meaning that even as dust and water enters the battery box, it will not be a problem for the batteries as they are sufficiently sealed.

The Final Battery Choice

The original plan was to replace the two Mastervolt batteries with two similar sized lithium batteries. Batteries come in somewhat standard sizes, with our original batteries being Group Super 8D in size. And lithium battery manufacturers offer Super 8D sized batteries and market these as ‘drop-in replacements”. In the end, two of 300 Ah battery from Kilovault would not fit, but three 200 Ah batteries would. And hence this is the battery we choose. Having three batteries instead of two batteries also has some minor advantages in terms of maximum sustained current draw and resiliency should individual batteries fail.

The Kilovault batteries have some other interesting features like, internal BMS with overcharge, over discharge, temperature
and short circuit protection, integrated bluetooth for monitoring with the companion iphone application and a relativity good cycle life of 5000 (80% DoD); 2000 (100% DoD) with 80% or original capacity. Time will tell if these were a good choice.

Battery Capacity

Ideally we want enough battery capacity and solar generation to achieve

  • 3 days with no sun
  • 5 days on our portable solar panels and the roof top solar panels are in the shade and
  • at least a week on our roof-top solar panels, assuming they have a clear view of the sky

With 600 Ah capacity, and a daily power budget of 2,250 watts and our solar setup, the batteries should last a little more than 3 days when there is no sun, typically 5 days with just the portable solar panels and typically 9 days off just the roof top panels. See our post on Solar Generation for more details on how we calculate these estimates.

It should be noted, that Victron Energy makes a very compact 200 Ah battery, and we could fit 4 of these into our battery box, for a whopping 800 Ah. However, these batteries are not cold weather rated. If we installed these batteries, that would mean 4.5 days of no sun, 7 days on portable and 12 days on roof top. Clearly better, but the improvement is not worth the loss of cold weather rating.

Battery Commissioning

The batteries are shipped with a minimal charge, due to shipping regulations in the US. So, once received, we charged them up as per the manufacturers commissioning procedure. For this task we used an Iota Engineering DLS-45 battery charger, being the one recommended by Kilovault.

Adding a Fuse

The original battery setup did not include a fuse to protect the wiring. Since we are changing things anyway, we decided to add a protective fuse on the positive feed. The fuse selected is a 300 Amps ANL fuse from Blue Sea (part number 5133). And this goes into a ANL Fuse Block, also from Blue Sea (part number 5503). The recommended fuse rating for our Magnum Inverter is 300 Amps, this is why we chose this particular fuse rating.

However things get a little more complicated in the event that we need to use the winch, then we will replace the 300 Amp fuse with a 600 Amps fuse, as the winch can draw up to 507 Amps when operating at the full 16,500 lbs and on the first layer of the drum. While it might seem like a hassle to change fuses when we use the winch, the reality is that we will probably never use the winch. We will also run the engine while winching, so the alternator and truck batteries will also be contributing to the power draw. The Kilovault HLX+ series lithium batteries can operate over the 150 Amp rating, just not continuously. And the internal BMS has over current protection, just in case.

All of the existing wiring and isolators installed by Earthcruiser® will be retained. New colour-coded 8 inch connector 4/0 AWG connector cables where purchased to string the three batteries in parallel.

The Installation

The install took about 2 hours to complete. During the process I realized that

  • I need some more battery terminal shrouds. And need to match up the colours correctly.
  • I need a good way to secure the batteries better.
  • I need a good way to secure the fuse holder better.

These are all things that can be done in the next attempt.

Programming the Solar Charge Controller

The Kilovault battery manual recommends a 3 stage charging configuration of fast Bulk phase, followed by a very short Absorption (Acceptance) phase and then a float phase and with no equalization phase. After a quick call to Roy over at Kilovault technical support, confirmed that Bulk would be 14.1 volts and Float would be 13.6 volts.

However our Blue Sky Solar charger is not able to limit the Absorption phase to under 2 minutes, so instead we configured the solar charge controller to skip the Absorption phase altogether. More details on this below with the final configuration.

  • During the Bulk phase the solar charge controller will send as much current to the batteries as possible. In reality of size of our solar panels limits this to about 25 Amps maximum.
  • Once the voltage of the batteries reach the Absorption (Acceptance) Charge Voltage setpoint, current is reduced as necessary to control the Absorption (Acceptance) Voltage. We set the Acceptance Charge Volts setpoint 14.1 volts. Earlier versions of the Kilovault manual had recommended 14.0 volts.
  • Although having said this, the Kilovault batteries do not like being in the Absorption phase for more than 2 minutes. And our controller only allows the time to be set in increments of a tenth of an hour (or increments of 6 minutes), in the range of 0 to 10 hours. So, we set the Acceptance Hours for 0 minutes, instead of 6 minutes. What this means is once the Absorption phase is triggered at 14.1 volts the controller immediately transitions to the Float phase.
    • A short Absorption phase for lithium is useful to equalize the voltages across each cell. We will keep an eye on the cell voltages, as see if they equalize without an Absorption phase.
    • Ryan at Blue Sky technical support also suggested that a 6 minute equalization phase at 14.1 volts every 30 days might make sense to equalize the cells.
    • The Sets Float Transition Amps per 100 Amp-Hours is disabled by setting it to 0.0 Amps, with the transition from Bulk to Absorption/Float only controlled by the timer only.
  • Kilovault technical support recommended a float voltage of 13.6 volts, although the manual recommends 13.4 volts. Decided to go with 13.6 volts.
  • Temperature compensation had to be disabled, so Set T-Comp Slope mV/°C/Cell was set 0.0.

There is no re-bulk voltage setting on our solar charge controller to trigger transition from Float back to Bulk charging. However, because the sun goes down every night, the controller transitions to Off mode at night and then in the morning when the sun comes back up, the controller transitions from Off to Bulk charge mode. Switching off the controller is another way to manually force a transition from Float mode to Bulk charging mode.

Also we noticed that while the solar charge controller is in Float mode, occasionally the batteries can go into Standby mode. I believe this is because the solar panels can supply sufficient power for the background load, being typically 60 to 90 watts. When the drain on the three batteries is less than 600 to 750 mAmps, or about 9 Watts, then the batteries will go into standby. Only when the power demand exceeds what the solar panels can generate, will the batteries start discharging to make up the difference.

Programming the Inverter/Charger

Programming our Magnum inverter/charger was even more difficult to sort out than our solar charge controller. And not even sure it is setup in the best possible configuration. There is a software upgrade available for our Inverter to better support lithium batteries, but of course we do not have the upgrade. And this is probably the reason why there is not much useful information in the manuals for lithium batteries. The only good news is that we hardly ever use the Inverter/Charger as the goal is to “off-grid” and away from places that have power.

After talking to Kilovault, they advised that the settings in their manual is assuming the inverter/charger is wall mounted and constantly charging, which is the situation we have in Molly. And we also have a solar charge controller. So, it is best to use common sense based on the needs at the time, what the demand will be on the batteries in the coming days and what the current state is of the batteries. In the rare event we connect to shore-power, we will become human controllers and managed the batteries manually.

There are two modes at our disposal that can be used, CC/CV and Custom. CC/CV is Constant Current/Constant Voltage and is good for bulk recharging. While Custom can be configured to automatically keep the batteries topped up. Both modes can be initiated through the control panel. Here are the settings we have for the Custom mode.

  • Maximum Charge Amps = 200 ADC (01D)
  • Search Watts OFF (02A)
  • Low Battery Cutoff Setting = 12.3 volts (02B)
  • AC Input Amps = 15 A (03A)
  • VAC Dropout = 85 VDC (03B)
  • Battery Type = Custom (03C)
    • Set Absorb Volts = 14.1 Volts
    • Set Float Volts = 13.6 Volts
    • Set Equalization Volts = 14.0 Volts
    • Set Equalization Done Time = 0.1 Hours
  • Absorb Done Amps = 12 ADC (03D)
  • Max Charge Rate 100% (03E)
  • Set amax Charge Time = 12.0 Hrs (03F)
  • Final Charge Stage = Silent (03G)
  • Equalization Reminder Days = OFF (03H)
Alternator

An alternator can be used to charge these voltages as long the output power is below 450 Amps and voltage is below 14.1 volts. Not 100% sure, but believe Molly is fitted with a Bosch F000 BLO 622 alternator with regulator. And the output is 12 volts at 110 Amps. So, should have no trouble using the alternator to charge the batteries.

Retaining Bracket

The current thought is to use some 1/2 inch right angle steel to secure the batteries. This material is available from the local hardware store.

Commissioning of the batteries. All batteries to be fully charged before they are installed.
Installation of New Batteries
Step 1. Get a coffee while the batteries still work. Plan the install. Time 9:41am.
Step 2. Assemble tools while still drinking coffee. Time 9:53am.
Step 3: Open Battery box and remove terminal bolts. Time 9:57am
Step 4: Remove existing wiring and retaining bracket. Time 10:02am.
Step 5: Remove AGM batteries. They were very heavy and I had some trouble getting them out. Time 10:08am.
Step 6: Clean out the battery box. Time 10:16am.
Step 7: Drop in new lithium batteries and install wiring. Make sure it fits. Time 10:45am.
Step 8: Tied up wring and test. Need to get some move insulating terminal shrouds. Time 11:03am.
Step 9: Fix the wiring. I had the Smart Shunt wiring incorrectly going to negative. Should be positive. Time 11:53am.
Step 10: Setting up the Solar Charge Controller via the UCM. Dip Switch 5 also set to off.

Note 1 : The Product Code is 62002700

Note 2 : Capacity is reduced in cold weather.