(battery management system)


This thing does it all.. the ideal setup to manage inputs, outputs, and provides data on exactly what’s happening. Lot of money, although value for money for what you get.. Australian designed and made, Redarc are superior quality products, with loads of features..
Basically the BMS 1230 does 6 things..

  1. manages inputs, whether solar, vehicle via Anderson plug, 240 lead or generator. Can work with a combination of these.. it also handles maintanence..
  2. Manages outputs, organises power leaving the battery, whether from one battery or two (or more). Can set min voltages cutoff etc.
  3. Battery charger, so comes with a 240 v lead, plug this into a power cord, and it will distribute the right amount of charge to the right batteries
  4. BC-DC charger.. so delivers the 14.5 volts, that the modern AGM style batteries need to be properly charged
  5. provides real time data on everything going on, in and out.. it does this by measuring current in both directions..
  6. solar regulator.. most solar panels these days come with a regulator, but you could buy unregulated solar panels, and connect to this system.

Many people, including myself a few months ago, will struggle to understand what this BMS is, and why do you need it…most things to do with second batteries, solar panels, etc, can be tricky to understand.. it sounds easy to put a fridge in a trailer.. but it is not so easy, and can get very expensive… I’ll try to explain a few things here, as I understand it now..

The DOT on it’s own, has minimal current draw.. 10 seconds of actuator use max once a day, and some led lights.. 125 amp hour battery has this covered 10 times over.. to charge this battery, you can connect a solar panel to the front Anderson plug (which attached to the vehicle while driving) provided it’s regulated solar panel, again which most are… or you can hook up a 240 lead, connect to the included and fitted projecta 240 v battery charger.. or while driving, charge thru the rear Anderson plug on your truck..

Now, this is where the BCDC or DCDC charger comes in.. all modern vehicles, don’t put out the 14.5 volts that AGM batteries need to be fully charged.. these batteries are expensive, and you can reduce their lifespan, and how much charge they hold, if not putting in a full 14.5 volts.. so if having a second battery in your truck, you need a bcdc charger.. this will also function as the solenoid, that switches the charge between batteries.. redarc do the BCDC1220, or C-tek the D250S .. so this needs to be fitted to the front of your vehicle, ideally, less than 1 meter from your batteries.. (they need to be kept as cool as possible, so must have airflow around them)

So this has the front batteries covered.. once that 14.5 volts gets to the rear of your truck, it’s more like 14 volts.. (just from voltage drop) .. once it gets to the battery in the toolbox, or some trailers have the battery at the rear, or say a caravan, could be many more meters back.. so the voltage is just dropping more and more the further it gets from the BCDC charger.. back to our original DOT, with minimal current draw, and a large battery.. if we don’t fully 100 % charge, and only 80 or 90 % charge, we still have over 100 amp hours.. which can be topped up with solar or 240 v, so this is fine…. BUT, if you are running a fridge, then that’s when you need a better setup.. this is where you have lots of options, and a lot depends on how you use your trailer.

If you are happy to run say a 80 or 120 watt solar panel when stationary, then the single battery should be sufficient. ie, keeping it topped up with solar, and then kept charged when driving.. But you don’t have much spare capacity, say if it’s wet for two/ three days, and you are stationary.. this is where a second battery comes in, but you still have to charge it.. once you put a second battery in, and say both are half flat, you won’t charge it in just a few hours driving.. so you need to make sure you are putting in the best charge possible, hence the BCDC charger, in the toolbox, next to the batteries.. so this will receive say 13.8, and deliver 14.5.. exactly what your battery needs (this is while driving) .. so if stationary for a couple days, then driving for a day, you should be ok.. if stationary for say 3-4 days, then you should start putting your solar panel out, or you maybe won’t drive long enough to bring them both back up… if you stay in caravan parks with 240 volts, then you really don’t need to worry about a second battery, or BCDC charger, or solar.. but the further you wander from a 240 plug, the more you need to keep the system running.. this would also apply to a generator.. if you have even a small generator, then again, no need for all this.. but not everywhere will allow generators, same with your camping neighbours.. you really need a few options for charging batteries..

So yeah even if you have a BCDC charger in your vehicle; with a second battery, and a fridge in your trailer, you really do need one also in the trailer toolbox (or next to the battery).. but , besides the voltmeter, which you can keep an eye on, it’s difficult to see, or know really what is happening (voltage is a difficult way to understand what the battery is doing. Current is the only true way to observe this) .. so this is where the BMS comes in.. it includes your 240 v charger, so don’t need to buy one of those.. it includes your BCDC charger, so don’t need one of those.. solar regulator also, so could use unregulated solar input.. (many fixed panels are unregulated, most folding, portable panels are already regulated.. the regulator prevents the battery from getting ‘cooked’ if already full, it stops or regulates the charge).. and then it tells you exactly what the fridge is drawing in amps, exactly what the solar panel is putting in, or any other inputs.. it’s a very good way of learning what does what.. ie how many amps does a 80 watt solar panel provide on a cloudy day.. the BMS will show you exactly.. how much is your fridge drawing.. BMS will tell you.. so yeah if you are interested in 12 v, want to understand or learn more about it, or want the ‘ducks guts’ best system available, then you should get the redarc BMS1230.. I don’t think there is much equivalent really that does what the redarc one does.. these are very clever people, building innovative products, all made in Australia.. we have a unique RV industry.. no where else in the world do you see fridges in vehicles or trailers like in Australia.. not in America, not in Europe, not in new Zealand. So Redarc have designed products that exactly suit our unique Australian market.. C tek is Swedish, and while very good quality products, they don’t offer the features the redarc does.. no where near it.. (just my opinion, some will disagree, that’s cool, I can buy and offer ctek if required)

So.. BMS by redarc, retail at $1900 .. yeah , ouch.. we can do a better price, if installed in a DOT.. evakool 47 ltr, $1400 installed in a DOT.. (we have to wire it in) solar panel about $600.. second battery $500 or so.. generator, min $1000 for a decent one, 1 kva… so this fridge in your trailer is costing some series $$.. it’s a very popular request now for campers, we build at drifta about 20 kitchens a week, and about 6-8 of them are fridge box kitchens.. you have to ask yourself , do you really need a fridge in the trailer.. personally, I’m fine with it in my truck… there are many advantages either way. But, yeah lot of people wanting it, and I think about half of our DOT’s from now on, will come with the fridge setup..

If you wanted to save some money, you could get the drifta fridge box kitchen (same price in the DOT) , leave the fridge out, use as storage space, get it later.. start with a solar panel, if needed, get a second battery later also.. then you can also get a cheaper BCDC charger (projecta do one that is fine), or if you save up enough, get the redarc BMS and really impress your mates… hope that helps clear up a few things, as always, any questions, send me an email, or give me a call.. we have an account direct with Redarc, so can also provide the extremely good ‘tow pro’ brake controller, by far the best on the market, (will put up more info on this later) and also any of the range of BCDC chargers.. ask me for a price if interested.. thanks, luke…
Ps, send me any questions, and I can put up a FAQ section on this subject… : )