Thread: Dual Battery Time Again

If your last battery set up worked than install the same.

Originally Posted by weeds

One would hope your winch would still work as its a general rule that your winch is wired to your start battery......if your winch ain't working than there is a good chance you engine isn't going to start...... Your fridge should be connected to your AUX battery which is separated from your start battery when you are at camp......this ensures you can still start you car. Babs, where bouts do you live.....might be easier if somebody shows you there install......

I think that's how all my last vehicles were set up, I'm just confusing myself.

I'm not using my old mechanic anymore so hence why I'm posting here.

I'll wait to see what Tim recommends

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Hi again Babs and my last post was part 1 of a 3 part reply to your questions.

The BCDC is just another name for a DC/DC device.

In Part 3 I will explain the best way to charge your batteries, all of them, and how the get the longest operating time for your fridge.

I will also give you details on the best way to setup for winching.

Sorry, I am a slow ( one finger ) keyboard typer so it takes me a while to get the replies typed and as posted, I am trying to get a lot of orders ready to go for Monday's mail.

All good Tim, I'll be patient

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I'll make it all simple

get a traxide from drive safe. prepare to hook it up.

fit the winch to the start battery with a good set of relays and a bypass solenoid for the traxide if you really think your going to torture it that much with the winch (you most likely wont).

get an auxiliary battery best suited for what you want to run off it,

• Pick something deep cycle if you only want to run a fridge and some low wattage lighting
• pick a dual purpose/hybrid if you're going to use inverters occasionally
• pick a cranking battery if your going to use inverters a lot or expect to parallel them for winching

Hook your compressor up to either battery and always have the engine running when you use it, same for the winch. This is as much for the benefit of the batteries as it is for the winch and the compressor.

Thats it, as shortly, simple and cost effectively as I can put it for you.

some extra information for you...

the key difference and the new scenario where I might recommend a BCDC charger over a drive safe unit is this...

BCDC charges usually incorporate a solar input and regulator and allow, in some circumstances a significant cost saving over purchasing both a dual battery controller AND a solar regulator combined with the cost saving of lighter cabling and in some cases installation costs. Typically, in a situation like this the normal method of operation includes longer driving times and extended stationary times relying on the solar to top up the batteries which moots the 2 key difference between a traxide and a DC/DC charger

me Personally I wouldnt buy a BCDC or DCDC charger outside of 2 very specific sets of circumstances Id run a setup simlilar to a traxide (or get a traxide) and fit a seperate solar system, primarily because I get to the the install work my self my way and I can get the component pieces at a good price.

Still waiting to find out about these Traxides ???

I'll wait for Tim's next part reply.

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traxides?

best dual battery manager for more than 90% of situations.

in a nutshell in most circumstances they will get you the longest draw duration out of a pair of batteries and give you the shortest possible recharge time off of running the engine.

They have a few configuration options that are dead simple and are compatible with pretty much every vehicle from the T ford through to next years whatever they come up with.

if you have nothing to start with get this kit

Def-USI-FPC Kit | TRAXIDE - RV | Traxide - RV

then its just a case of if desired adding aftermarket solar to the anderson plug or as I would recommend fitting the solar gear to your camper trailer and using that anderson plug to hook directly into the campers battery if fitted.

Just remember that for the very best results all your batteries should be the same technology or if your going to be using one in the camper that it should be the same type of battery as the aux battery in the vehicle.

about the only thing that drivesafe does different to me in his setups is his fusing and circuit breakers. I tend to use more of them and to use both fuses and circuit breakers. Double edged sword, My system is safer in a small percentage of worst case scenarios his system provides more flexability in about the same number of cases.

Everyone picks up on the fact that none of my vehicles have traxide units in them and thats because my battery system is setup to allow me to relatively easily provide 24v and his units cant handle what I have to do to achieve that.

heres how most dc/dc and BCDC chargers work.

you put it in wire it up and when the engine is running and the voltage is high enough it starts sucking down amps and doing white man magic to pump the voltage up to the charging voltage of for the aux battery at the limit of the unit, say 40A.

Remember entropy, it works for electricity every time you step it or conduct it you loose a little bit of the overall input.

at the end of the day with just a 10% loss you need 44A of draw to produce 40A of output (Its more complicated than that but that will do for here) and a little bit for the smarts.

a traxide doesnt do that fancy stuff and its also not limited to a paltry 40A it is for want of a simpler better explanation an exceptionally smart relay. what you put in on one side comes out the other. you still need a little bit for the smarts.

what a traxide does better than most DC/DC units is make use of the main battery. it leaves everything hooked up with essentially no losses and splits the load between the 2 batteries taking full advantage of peukurts rules on battery discharging. then it disconnects the main battery letting the aux battery take over. At this point compared to a DC/DC unit you're in front. not by much, maybe 10AH over a 24 hour period for me thats an extra 3 hours of cold beer potential. But Its still in front and at this point for the cost of a good 40A dc/DC you jsut bought the entire kit from my previous post. Thats Everything you need to install it to be able to run your frigde for an extra 3 hours.

so now lets get onto charging and here is where traxides shine.

your alternator can produce 100A and your 40A DCDC can push 40 to the aux battery, lets say its dead, and needs 100A to charge. the main battery is at 70% and needs 40Ah worth to charge it.

for the first 15 minutes the traxide will dump most of the charging current to the dead battery and some into the main battery this will taper across untill the charging current is equal to an even split and then it will stay evenly split but taper off. while the aux battery is flat the alternators output will be pegged at maximum wattage output and therefore maximum amps. lets say thats 100 amps and that your vehicle always draws 20 so you have 80 amps to charge with. To start with your charge might be 70A going to the aux and 10 going to the starting battery, they then balance down to 40A each and as the system voltage rises the amps drop off because thats how alternators charging batteries work. just to make up a time for the first hour your aux battery was getting more than 40 amps. a lot more to start with but then it tapers back.

lets look at DC/DC

you start up and the alternator starts to charge the main battery, its at 70% so its going to draw 40 Amps which is the same as the previous example, thats what it needed, thats what it took. Then after a minute or 2 the battery voltage comes up and the DC/DC kicks in (sometimes immediately so lets just say that it did that in this scenario) and begins to draw its 40 Amps from the main battery to put 40 amps into the aux battery (I'm being nice and ignoring entropy here in reality its drawing 44 to deliver 40 which means the main battery is now only getting 36A but I digress) 15 minutes later when the main battery is partially charged it doenst need 40A it wants 30, the DCDC is still working its guts out against the still nearly flat aux battery so is still pulling its 40Amps. the Main is pulling 30A, the aux 40. thats 70.

heres the stakes after 15ish minutes.. the traxide system still has the alternator pushing its limits 20amp to thevehicle and 80 to the batteries for charging. the DCDC has the same 20 amps going to the vehicle but only 70A going to the batteries. the bigger the alternator and the bigger the batteries the more pronounced the difference becomes.


Drivesafes goign to hate me for it but here it is..

these are the 3 circumstances when a DCDC or BCDC is better than a traxide.
1. when you need to shape or current limit the charge going to the aux batteries
2. when you need to step across voltages (12-24)
3. when you need to maintain a more stable voltage on the aux battery for sensitive equipment

if you're in one of those 3 catagories then you need a very specific DC DC charger and so far its been less than 10% of the cases ive ever had to do DBS installs in.

other than that... let your wallet make the decision for you.

from ebay for $460 + postage you can have just the charge unit and then you have to pay for all the cable, fittings and installation.
From traxide for $445 + postage you can have the whole kit and then only have to spring for the install.

you might notice that the unit in ebay is also a solar capable unit. thats ok for the cost of the cabling, and the $15 difference you can buy a reasonable 10A solar regulator. which when plugged into the traxide system charges ALL of your batteries as opposed to only the aux battery. Before you note that you want more than 10A worth of panels, A, for just a car fridge no you dont and b, if your getting bigger panels than that most bigger panel setups you can get bundled with a regulator.