Our off-grid Power Upgrades

When we bought our first van, I upgraded the batteries from the stock 105AH AGM to twin 140AH AGM. Unfortunately that van was written off after 6 months (money refunded – floor was rotting due to water leaks, that’s a whole other story!). Fortunately I was able to salvage the batteries from the old van and transferred them to the new one.

I had a second battery box fitted to the chassis of our new-to-us Essential Exceed II (ours battery was chassis mounted to start with) by the wonderful team at Lawrence RV in Brendale (great bunch of guys there too) so I could swap the batteries in. All worked great, had a couple of sections of our trip free camping and everything worked perfectly. Until about a year into our trip…

Dual chassis mounted battery boxes

NOTE: Before we dive in too deeply, if you have not read my bio on the Who Are We page, my background is electronic engineering. So none of this was a gamble, confusing or difficult – for me. Before attacking something like this on your own, especially if you do not have much experience in working with power, please consult an expert. It may only be 12v, but 280AH batteries can cause electrical fires when short circuits occur.

Second Note: I am not saying this is the ideal solution, I am not saying these are the world’s best products, I am saying this is the best I could put together to suit my budget, my requirements, the timing needed, the situation I was in and research I had done. If I had to do over in the same circumstances would I change anything, probably not. If I had a do over from the beginning before we left for full time on the road would I do it differently, probably not as I didn’t have the funds to go Lithium then. If I had unlimited funds would I do it differently – hell yeah. I would be flying a light aircraft to each location, hiring a 4wd and hotel room!

OK, rant over, let’s get into it!

On a particularly cold night, we had the portable fridge running as usual (about 1.7amps) and the diesel heater running (about 1.5 amps) and all was great until about 3am when someone flushed the toilet and BEEP-BEEP-BEEP… I thought the fridge had been left open in my slumber induced haze. Nope, was the Victron Battery monitor beeping low battery. Both batteries had taken a turn for the worse and on testing a few weeks later one was at 19AH max capacity and the other 30AH max capacity. In hindsight, that was about the 4th night of -4° over a 2 week period of sub zero temps and may have (but should not have) had a negative effect. The test was done once we arrived at Katherine with low 30 degree days. With the batteries mounted externally they may not like those temps.. hmm. Lucky for us our plans now ‘should’ keep us away from winters, forever..

The supplier offers an 80% refund from 12 to 24 months old and these were close to 2 years, so I decided I should put that towards new Lithium Batteries. One thing I did have to be careful with was the depth of the batteries. The boxes are only 180mm deep and many newer batteries are 190mm deep. So this limited me to brand and size.

So I bought 2 Giant Power 140AH Lithium Iron Phosphate (LiFePo4) batteries, with a 100amp internal BMS (100amp continuous, 200amp for 5 seconds). Since I was getting an 80% refund on 2 year old batteries, the changeover was just over $1000 for both.

So why did I change over to Lithium? Much lighter (just saved over 40kg), better at handling high current loads, much better at handling low discharge state (these batteries are rated at 5000 cycles of 100% DOD (Depth of Discharge), so in other words can be run flat and recharged 5,000 times and still retain over 80% original capacity), safe (discussed below), and accept a charge faster than lead based – ideal for running free camp with solar.

Now lets jump sideways a little here and discuss safety – there is a lot of discussion on Social Media around Lithium based batteries being dangerous, that is they can explode, burst into flame etc. Yes, this is totally true for Lithium Polymer (and I have seen it and teach it in the Remote Aviation classes), and to a small extent Lithium Ion (regularly used in power tools), but LiFePo4 batteries do not burn, do not melt down, do not overheat, do not burst into flame even if punctured and to top it off contain no environmentally hazardous materials. They are in fact actually safer than a lead acid as there is no acid to spill and corrode.

140AH LiFePo4 Batteries

I removed the old 33kg each batteries and refitted with the new 12.5kg each batteries, so a net saving straight up of over 40kg!! That’s a huge bonus. Anyway, whilst i had them out I decided to see how long the cabling was and if it was possible to swap around the cabling. My original single battery of course had the positive and negative wiring connected directly to it, then the second battery was simply paralleled using 2B&S cables. This is fine for low to medium current applications as there is minimal voltage drop across the cables and both batteries will be always at the same voltage. However with large current draws there will be a small voltage drop across these cables so the primary battery will be loaded more than the secondary battery. How much this will affect the longevity of the batteries is honestly close to bugger all, despite the dire warnings you will se on the net (assuming adequate size link cabling is used). However, since I have a 3KW inverter drawing up to 200amps depending on load (that’s 200amps for a 2400w load) I wanted to try and balance the batteries properly (that install is covered on the Inverter blog post). To do this, you simply connect positive to one battery and negative to the other, still using the 2B&S cables to join them together in parallel. The 2B&S cables are rated at 188amps per metre, I am using 700mm cables so well capable of the maximum the battery’s BMS can provide.

To my delight, the negative cabling was more than ample to swing across from the original primary battery position to the new secondary battery position. This gave me the perfect balance solution. It did mean cutting all the cable ties off and relocating to make it neat again. In addition, the original Solar Controller and BMPro Battery charger both had 6B&S cable from the cabinet to the battery. At around 2.5m of cable this is more than adequate for over 60 amps. So.. I disconnected the battery cables from the Solar Controller to the battery at both ends, connected the Battery end to the Anderson Connector (that was originally connected to the battery directly), then at the controller end I relocated the cables to join in with the input wiring from the roof solar panels. So now I have the roof solar and the external solar both running through the same MPPT controller. I then ran the output from the Solar Controller directly to the Battery terminals on the BMPro Battery Management system. Now both the AC and Solar will charge through the same cables. It can never never see more than 60 amps and will most likely never as the AC charger is max 30amps and the solar max 30 amps (and I currently only have 300W of Solar for a max 12amps or thereabouts).

Now to the charging side. The claim is these can drop straight in and work with existing AGM chargers. Well.. yes and no. AGM Chargers do not fully charge due to the differences in final fully charged voltage comparing AGM to Lithium and also have different profiles for bulk, maintenance and storage etc. So not ideal in any way, but will work of sorts in an emergency. Unfortunately my Battery Management System in the van is 5 years old and does not have a Lithium charging profile. My Solar controller was also a cheapie ToPray 30amp PWM and I had been long wanting to upgrade that as well. With both the roof mounted and portable solar panels connected (150W + 160W) the max charging I could get was about 7 amps at midday.

So an upgrade was in order. I have now replaced the ToPray PWM Solar controller with a Victron Smart Solar 30amp MPPT controller and rewired the external auxiliary solar input to run through this controller as well so both the roof mounted and any portable panels will make the best of the MPPT controller (A quick test with ONLY the 160W portable panel at 4pm in Darwin with a smoke haze gave me 6.2 amps charge..) Yes I installed it upside down, this way the wiring input was on the top and reachable. As the old wiring was at the bottom, I cut out a hole behind it to allow access to the cabling to redirect it from the bottom holes to the top one. Not having a hole saw in my bag of tricks, I drew a circle (traced around a roll of electrical tape) then used a 5mm drill around the edge. Before drilling the last bit I pushed a metal skewer in from either side to stop it dropping in to the hole!

Next of course the BMPro is AGM only, but is also a battery management master switch and fuse box, and a grand or more to upgrade. So to fix this I invested in a Victron ACDC 30amp charger. This will get wired into the Battery terminals on the BMPro and the 240v power for the BMPro disconnected (the charger will use the original power point in the cupboard to the left where the BMPro is currently plugged in, so no problems with both ever being switched on together anyway.)

Victron Lithium Smart Charger

I already had a Victron BMV 712 battery monitor system that worked great, hence why I had no issues with using more Victron gear. The best part is they all have bluetooth monitoring from the same app as well, so I jump in and see what any of them are doing at any time. The Battery Monitor giving me the alarms for low battery as well.

If you have any questions or queries on any of the above don’t hesitate to leave a message below, happy to help where I can. I should add from a personal experience side, all the Victron gear above was purchased at full retail through Everything Caravans, again.. Yep, again they had the best prices on the web and their delivery is superb – solar controller sent to the caravan park at Coober Pedy in 3 days, the AC charger to the caravan park at Darwin in 4 days! Love those guys! The batteries were sourced from Aussie Batteries on the Sunshine coast QLD. The original AGM batteries failed prematurely, but that’s what warranties are for. Aussie Batteries were wonderful through the whole warranty process with my new batteries also travelling all the way to Darwin and now working great.

If you are interested, we also run a 3000w inverter (the main reason I wanted to ‘balance’ the battery wiring, a brief write up on that is on the Inverter blog post.

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2 Responses

  1. Karen says:

    Hi Dave, we have just ordered a new Red Centre Newell+ van (due for delivery April/May). We are having a compressor fridge so is coming with 2 AGM batteries. Would you recommend us going for Lithium now instead of AGM? Apparently, Lithium will just drop in if we want to change down the track. We don’t plan on doing a great deal of free camping – we have never done this before, always opting for CPs but now we are retired, we plan to “dip our toes in the water” with free camping. We are very clueless with all of this. Thankyou so much, Karen & Peter

    • Dave says:

      Hey Karen. I would consult the dealer and see what they would charge to upgrade to Lithium at the build phase. No double spending that way! For me the 2 Lithiums saved me 40kg, that’s a lot.. also with a compressor fridge it will run much better and much longer on the Lithiums. So yes, I would highly recommend upgrading at this stage. Be careful what they want to charge you for Lithiums though, often you will be much better sourcing your own and getting a small amount refunded for the non used AGM batteries. The only reason I did not go Lithium originally was they were double the prices they are now and my whole system had to be upgraded to suit. Cheers, Dave.

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