New Member
So after accidentally leaving my old AGM batteries connected after a trip, I found myself with two nuked 100ah batteries. Additionally, while away camping I found myself hawking the Volt and Amp readout on my trailer much like an old man monitoring the thermostat or Air Conditioning settings on a hot day. So I decided to take the opportunity to upgrade to Lithium.

Unfortunately for me, my DCDC charger was the old Projecta 25A that technically didn't have a lithium profile. (arguably the lithium profile isn't absolutely necessary). So I dove into the battery compartment of my trailer to see what work needed to be done to change to a 40A Redarc BCDC. To my disappointment, I found a messy network of cabling that was the minimum gauge (not optimum) for a 25A circuit, thus completely unsuitable for 40A. So I opted for the 25A BCDC that was lithium compatible. Excellent.

So began the task of working out which wire to connect as per the detailed instructions provided by Redarc. Unfortunately, nothing was labelled and worse all the wires were red despite being negative, but luckily I was able to reverse engineer the colour code of the Projecta (not too different from the Redarc). Whilst I was cutting and cabling I decided that, while I didn't have the emotional strength to navigate the circuit forward of the charger, I could navigate and upgrade the wiring after it i.e. the consumers. So, what did I find? I mess with oversubscribed battery terminals (not necessarily bad practice but certainly not the best way or neatest).
As a result, I decided to install a bus bar to clean things up. (I didn't know what accessories were what so I played it safe and found a bus bar that could go to 150A which is about the max output of my batteries).

The busbar created an unintentional opportunity to integrate a battery monitor (Victron 500A) so based on my guesstimated 150A load, I threw on a 2AWG cable between BM and Busbar to ensure absolute efficiency and heat protection.
Things just got better from there. I realised that the Victron not only provided me with battery monitoring, but it too could act as an opportune busbar for a 2000W to 3000W inverter (which I don't have.... yet) given its 500A rating. So I decided to install a terminating cable of 0AWG to allow me to plug and play an inverter with very little modification to the existing circuit and with the benefit of monitoring the consumption of the hypothetical inverter.

Would I recommend this job (as an unqualified fool)? Yes, but don't do it without buying yourself a good wire stripper, hydraulic or ratcheting crimper and lugs to match. Likewise, do the math correctly the first time, and if you have to guess go conservative. It's quite straightforward once you're happy with the math.

Am I happy with it? Meh. I don't think the cabling is tidy or untidy but somewhere in the middle. I might re-attack the cabling in the future. My next job is to get a busbar for the positive terminals and while im at it find a better-looking negative busbar. (im still waiting for the actual Lithium to arrive in the mail so I have a bit of time to kill. As an unqualified person, I think it's a good first crack given my level of competence.

Anyway, thanks for reading.


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Well-Known Member
Good on you for having a go.
Hint, if adding multiple cables to your battery terminal (always better to use a busbar), then arrange lugs on battery terminal in a “Christmas Tree” configuration, largest at bottom, smallest at top.