How to charge and monitor lithium batteries?

Enhancing your caravan 12V system

With lithium batteries now the clear choice for the lovers of free camping, many caravan owners upgrade their 12V system to make it lithium compatible. But how do you charge your new batteries when on the road and how you monitor lithium batteries power usage when using high loads? A range of BMPRO products can enhance your RV 12V system, and one of our customers, John Hilton, shares his experience in installing these products.

John is a happy owner of 2020 Jayco Silverline 21.65-3 and have earlier upgraded to J35D power management system with 2 Invicta 125Ah Lithium batteries – perfect combination for free camping in comfort. That’s his story:

Installation of MiniBoostPRO, BC300 and Commlink

I have finally completed the rewiring of the batteries in my Silverline, including the install of the MiniBoostPRO, BC300 Shunt and CommLink I purchased from BMPRO at the Caravan Show in Melbourne in February.

The MiniBoostPRO now gives me a clean charge feed to my lithium batteries rather than relying on the feed from the car, and the BC300 reports all usage, even high current draw, rather than having things like inverters bypassing the current draw reporting.

Here are my installation steps and details:

  1. I have a separate 8B&S cable from drawbar to under the bed for power from the car.
  2. I moved the batteries from the left to the right side under the bed.
  3. I connected the Battery Negative Terminals using 2B&S Cable. Note the Negative is terminated on the Battery Post on top of the BC300 on Battery 2 as suggested by the BMPRO customer service team.
  4. I connected the Battery Positive Terminals using 2B&S cable with an inline 200A Mega Fuse.
  5. I made Positive and Negative BusBars using 100mm x 20mm x 8mm Copper Bars, shrink wrapped for some protection.
  6. I connected the BC300 to the Negative Terminal of Battery 2, and the Pos+ Flying Lead to the Positive BusBar on Battery 1.
  7. The CommLink is installed underneath the ControlNode103 and plugged into the spare port on the node as there are no spare ports on the J35D.
  8. The Kickass 2000W Inverter is wired using 3B&S Cable, with these cables connected on the Positive and Negative posts of Batteries 1 and 2 as was suggested.
  9. There is a 200A Circuit Breaker in the Inverter Pos+ line for obvious safety, but also so the inverter can be kept powered off when not in use.
  10. I made a frame to Install the MiniBoostPRO on, lifting it above the heater ducting, along with the required 40A fuses and a Common Earth post.
  11. The 8B&S Cable coming from the vehicle comes into the 40A fuse marked ‘Car 12v’ then is connected to the Orange cable on the MiniBoostPRO.
  12. For Portable Solar I have installed an Anderson plug externally on the van, with 8B&S cable coming into the 40A fuse marked ‘Solar’ then connected to the White cable from the MiniBoostPRO.
  13. The red cable from the MiniBoostPRO goes through the 40A fuse marked ‘Van 12v’ and then to the Batteries via 8B&S Cable. Aux in the J35D is being used so couldn’t terminate there.
  14. All Negatve Cables associated with the MiniBoostPRO are terminated on the Common Earth post at the rear of the MiniBoostPRO.
  15. Other cables attached to the BusBars are Pos and Neg cables from the MiniBoostPRO, the J35D and the Breakaway system.
  16. The Green Battery Chemistry wire passes through a 2A fuse and is connected to the Pos terminal on Battery 1.
  17. The Blue ignition trigger wire passes through a 2A fuse and is connected to the cable coming into the 40A fuse marked Car 12v as suggested (I have a 2nd battery and isolator in the vehicle).

I have included a picture showing how this change has made available at least half the under-bed area for further storage. There also was quite a lot of cable left over once I completed the rewiring – amazing!

I took a video of the JHub as my wife cranked up her hairdryer through the Inverter. The BC300 did its job and the JHub quickly reported 156 Amps being drawn from the batteries. BC300 helps monitor lithium batteries when using high current loads – super valuable.

BC300 and MiniBoostPRO install to charge and monitor lithium batteries
Two Invicta lithium batteries and a KickAss pure sine wave inverter with a DC-DC charger and a high current monitor
MiniBoostPRO installed
MiniBoostPRO installed
Inverter wiring
Extra storage as a result of a smart installation
Free space available after the installation

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3 thoughts on “How to charge and monitor lithium batteries?”

  1. Hi. I have 2017 Silverline OB. I upgraded to J35D, CN10 and BC300, 2x 120aH LFP that can rated output 150A each continually.
    Apart from the the old 2017 tablet no longer capable to communicate with the new Control node, everything works well. I moved the J35 from around the corner to the front of the panel.Batts on the LHS of the underbed cavity as that is more over the wheel
    Question for you , from your photo, why take the Neg Batt lead for the j35 through the shunt instead of directly from neg post? The j35 measures the current flowing through it from the house batt connections. If taken through the shunt might not the shunt be measuring the SAME current and reporting back to the J35? Double reporting? I have yet to ask bmpro about this.
    You also stated the Acc batt input on the j35d is taken. What 12V source is connected? Mine is not used as yet. I feed car power or portable 200W solar blanket through Anderson & 6AWG cable (via inline 50A fuse) to this area,to an Enerdrive dc-dc40+ then directly to the LFP batt’s via the bc300 shunt. 240V is via Enerdrive 2000W rcd invertor.
    I would like to show photo of my set up but can’t do that here

    1. Olga kustova

      Hi Ross,

      Please ensure the locations on the phone are turned on.

      Can you remove and refit all canbus cables in your system to ensure there is a good connection on each?
      Position of the ControlNode can also affect system performance – moving it higher up may resolve the issue.

  2. PS. John – to explain myself better, one of your photo’s show that both of your LFP Batteries Negative Terminals are connected only to your parallel 2B&S linking Cable – nothing else is connected directly to the Batt -ve posts. The black Neg cable going to the J35 Batt -ve connection, appears to come from via the Shunt & your Neg bus bar.
    As I said in my previous message I think you might find that the current supplied from the 35D outlet connections (for the van’s light and power) maybe being recorded twice (doubled up) – 1st via the Shunt and 2nd time via the J35D itself. I’m waiting for Steve’s response – from BMRPO Customer Service
    regards Ross

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