DB Isolators?

[ThorneGator]

Hello all......

Are Dual Battery Isolators all the same?
From spending too much time searching the net on this, it seems that most of them are pretty much the same: isolate starting battery at X voltage, link batteries for charging once starting battery has exceeded Voltage threshold, and protect accessories from voltage spikes at startup.
I realize they differ slightly, depending on: continuous voltage, temp. voltage, cut in & cut out voltage.

So is there any real difference after that?.....because the price range would seem to suggest so.

[Slunnie]

I'm not sure how different they all are, but they all seem to do the trick.

I just use a Redarc that connects the battery when the engine is running (and charging) and disconnects when the engine is stopped (not charging). At the end of the day I'm not sure what more could be asked of it.

That said, a lot on here like the Traxide one and apparently that is the go for the more modern charging systems for some reason.

[ThorneGator]

Thanks for this Slunnie,

One thing that has me wondering though..... if they are so similar, why aren't the Jaycar DBI's mentioned on here more often? Is there something legitimately wrong with something that cheap?

[mrs]

If it anything from TD5 on then you will be best with a DC/DC charger as they have a smart alternator and therefore they will alter the voltage output as they see fit.

[Slunnie]

Its really worth reading Drivesafe's posts on the DC-DC chargers. He manufactures the Traxide equipment and he is very switched on with all of this - I think the Traxide DBS is the only unit approved for modern type (ieD3/4, RRS etc) LandRovers. Hopefully I don't put words into his mouth, but I thought that he recommended not to run them as they increase charging time.

[drivesafe]

Hi ThorneGator, what is your intended use for a dual battery system?

This will be more important as to what DBS can do for you.

[drivesafe]

If it anything from TD5 on then you will be best with a DC/DC charger as they have a smart alternator and therefore they will alter the voltage output as they see fit.

Hi mrs, and there is no advantage to fitting DC/DC devices to most new vehicles, not just Land Rovers.

But in the case of a D3 or D4, as Slunnie correctly pointed out, you will need to do a hell of a lot more driving time to give a DC/DC device enough time to recharge batteries as compered to what your alternator can do by itself.

A perfect example is if you fitted a 55Ah Optima Yellowtop under the bonnet of a D4.

If the battery was flat, your would need to drive for around 3 hours for a 20 amp DC/DC device to get the battery up over 95%, and nearly 2 hours for a 40 amp DC/DC device to do the same.

Whereas, just charging via one of my isolators and you will have the same battery over 95% SoC in under an hour.

The major advantage to using a D4 alternator as the primary charge device is that it runs at 14.7v and has at least 100 amps available for charging the Optima.

[DiscoMick]

I think Traxide units allow some of the starting battery to be drawn in addition to the second battery while saving plenty for starting. Have a look at the Traxide website for details.

Sent from my A1601 using AULRO mobile app

[mrs]

A lot of new vehicles do not put out a constant 14 plus volts if they don't think they need it so unless you can step it up then batteries such as AGM will not reach full charge. I have had this issue in my TD5 disco

[drivesafe]

Hi again mrs, you do not need a constant 14v to fully charge any lead acid battery, AGM or otherwise.

Most lead acid batteries can be fully charged with 13.5v, the only difference is that it will take a little longer.

There are now well over 4,000 D3s, D4s, Defenders, RRS and L322 RRs with my gear in, and quite a number of the D4s are used to tow a caravan with as many as 3 x 120Ah batteries, and the D4 alternator has no problems charging all these batteries ( 5 batteries ) from a low state to a decent SoC in a reasonable drive time.

And Note, D4s have variable voltage alternators.

[Tombie]

If it anything from TD5 on then you will be best with a DC/DC charger as they have a smart alternator and therefore they will alter the voltage output as they see fit.



Sorry but that's just plain wrong..

[Tombie]

A lot of new vehicles do not put out a constant 14 plus volts if they don't think they need it so unless you can step it up then batteries such as AGM will not reach full charge. I have had this issue in my TD5 disco



All later vehicles come with AGMs [emoji41] so there goes that theory [emoji41]

[Toxic_Avenger]

I run a relatively 'dumb' Blue sea systems ACR (compared to the DC DC things with all their extra circuitry), benefit of this one is its current handling capability over a lot of the other options out there.
Like tim's unit, mine has the ability to combine or isolate bateries on command, useful to self jump start, or combine multiple batteries for high amp draw operations (winching etc).
It's a giant can of worms, be warned, but for the average punter like myself (basic camping, no fridge, no caravan etc), a basic system will more likely than not pull you up.

[weeds]

My first isolator was a manual switch aka idiot switch as your bound to forget to either isolated or de-isolate.

I than moved to a traxide......

Fitting a basic redarc to my new rig.

Having the two batteries connected to give more capacity hasn't isn't a big priority as one I like to leave the starter out of the equation and secondly I have never not parked up long enough without moving where my solar doesn't keep up.

[Dorian]

Thanks for this Slunnie,

One thing that has me wondering though..... if they are so similar, why aren't the Jaycar DBI's mentioned on here more often? Is there something legitimately wrong with something that cheap?

I have used the jaycar unit. Had problems with the USB outlets draining my house battery down to 5v. Put the Jaycar unit between the house battery and the USB outlets to protect the battery. The jaycar unit kept staying closed - not always but 1 in 5 times it would let the battery drain.

[mrs]

All later vehicles come with AGMs [emoji41] so there goes that theory [emoji41]
Some new vehicles come with AGM batteries with an alternator setup for them, definitely not all new cars. Particularly with a lot of the Jap stuff they are having problems with putting out enough voltage to get an AGM past about 85%. This the trouble I was having with my Disco 2. Sometimes the alternator was only giving out mid to high 12s and so my AGM wasn't charging fully. This was with a new alternator so I look it back and had it replaced - same story. Now I have say 12.5 - 13v on battery 1 and 13.9 - 14.5 whilst driving. Looking at the specs for approx 100Ah AGM for float it has 13.6 to 13.8v or cycling 14.6 - 14.8v

[Tombie]

Our Discovery 2 puts out 14.7 at start up, dropping to 13.8 after about 20 minutes and on a very long run about 13.4

This is with the new alternator and the original which failed about 2 years ago.

[drivesafe]

Looking at the specs for approx 100Ah AGM for float it has 13.6 to 13.8v or cycling 14.6 - 14.8v

Hi again mrs, those specs are the MAXIMUM tolerable voltages, not the MINIMUM required to fully charge the battery and relates to charging batteries with a battery charger, not an alternator.

If you have a decent quality AGM battery, then check out the specs for that specific battery, at that battery's manufacturers web site.

Each battery has it's own specific specs but there are some common specs, like MAXIMUM voltage tolerances.

For all modern AGMs, the maximum voltage is 14.7v.

There are some exceptions, like Optima Yellowtops and Bluetops, where they have a MAXIMUM voltage of 15.0v but can be fully charged with as low as 13.65v