Do I need a DC/DC charger in my 105 Landcruiser

Submitted: Sunday, Sep 06, 2015 at 15:56
ThreadID: 130201 Views:5467 Replies:8 FollowUps:1
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I have fitted an Auxilary battery under the bonnet, a 105AH Lead Acid Deep Cycle. Do I hook it up with the standard old isolator or a DC/DC charger. I had dual batteries in my Troop Carrier using an isolator, the deep cycle constantly had corrosion on the positive terminal & the battery clamp was slowly disappearing. The alternator puts out 14.2volts in my 105 series. Thanks.
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Reply By: Athol W1 - Sunday, Sep 06, 2015 at 17:46

Sunday, Sep 06, 2015 at 17:46
Enormous Racing
As your auxiliary battery is located under the bonnet it will work well with just a decent VSR (Voltage Sensitive Relay) type isolator and good heavy cables.
AnswerID: 590046

Reply By: Been-Everywhereman - Sunday, Sep 06, 2015 at 18:50

Sunday, Sep 06, 2015 at 18:50
We have the good ol ARB solenoid style dual battery system in the 105 and a 5 stage do dar do dar wipes your bum DC/DC dual system in the Prado. In both cars the morning after running both fridges all night the aux batteries are 11.5 volts. So there is no difference between our systems at all. Once you start adding in losses due to under voltage and over current I can't measure the difference.
AnswerID: 590049

Reply By: Member - ACD 1 - Sunday, Sep 06, 2015 at 18:54

Sunday, Sep 06, 2015 at 18:54

The good thing about the 105 is its simplicity.

I use a Baintech like this one.

Baintech Dual Battery Setup

Works well - simple as - don't even know it's there - joins the batteries at the flick of a switch if you need the extra boost to get going.


AnswerID: 590050

Reply By: Enormous Racing - Sunday, Sep 06, 2015 at 19:00

Sunday, Sep 06, 2015 at 19:00
Thanks for your replies. I was just about to fork out some cash for a Redarc 1225 or 1240 but thought I should just do a bit more research. There's so many forums on this but none seem to be specific to my situation. I might set one up in the camper trailer eventually.
AnswerID: 590052

Reply By: Member - Bigred13 - Monday, Sep 07, 2015 at 10:24

Monday, Sep 07, 2015 at 10:24
Hi Enormous , I have fitted a C Tek 250s in my 105 series to charge the auxiliary battery as prior to fitting it my battery never reached 100% charge as the alternator will only charge to about 75% as that is what the start battery is needing and then it tapers off .A deep cycle battery needs to be charged to 100% or its life will be short lived .
AnswerID: 590075

Follow Up By: Ross M - Monday, Sep 07, 2015 at 10:39

Monday, Sep 07, 2015 at 10:39
The posters alternator supplies 14.2v and therefore if yours does too, the deep cycle will charge as that is the regulated voltage of the alternator regulator. So, the aux battery WILL get charged if the cabling is suitable and not causing a voltage loss.

I have a 14,3-4v alternator in a Dmax and when connected the main, the AGM aux, AND the two in the Tvan ALL receive 14.3 at least. The multimeter I use reads the same on all batteries.
Two fridges run off the aux batteries. Still going after 5 years.
FollowupID: 858065

Reply By: Member - Bigred13 - Monday, Sep 07, 2015 at 11:13

Monday, Sep 07, 2015 at 11:13
Hi Enormous ,further to my earlier post re DC DC Chargers ,the attached link may be more self explanatory in what a Dc Dc charger does that an alternator does not ,especially in vehicles made after 2007 ,where the alternator is limited in its voltage ,for environmental reasons ,down to 12.7 volts not the 14.2 Volts ,which is there for a short time .
regards John
AnswerID: 590076

Reply By: Capt. Wrongway - Monday, Sep 07, 2015 at 16:14

Monday, Sep 07, 2015 at 16:14
I two have run simple VSR's between my starting battery & deepcycle for over ten years in two Prados. Never had a problem with either battery being charged or lasting five years in both vehicles.
AnswerID: 590086

Reply By: Tim F3 - Tuesday, Sep 08, 2015 at 10:30

Tuesday, Sep 08, 2015 at 10:30
I have a landcruiser 4.2 turbo manual with a triple battery set up. Two batteries under bonnet in factory location.a third battery (wet cell deep cycle 100 amp) in the rear of the vehicle,plus cable to tow bar to charge battery on camper.

I use a simple isolator purchased from ABR an advertiser on this site.

At idle, voltage at front batteries 14.3v ,voltage at rear battery and trailer plug 14.2v so no need for dc charger in my opinion.

I have used this setup in all my vehicles over many years without problems.

All the best.
AnswerID: 590119

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