dual batteries

Submitted: Wednesday, Mar 01, 2006 at 15:38
ThreadID: 31294 Views:2042 Replies:7 FollowUps:14
This Thread has been Archived
question.
if you have dual batteries fitted to you car do they recharge at the same time or does one fully charge first then the other charges up ?

do i need to swap them around to get the same life out of each battery ?

cheers
johno
Back Expand Un-Read 0 Moderator

Reply By: Groove - Wednesday, Mar 01, 2006 at 15:44

Wednesday, Mar 01, 2006 at 15:44
How each battery is charged depends on what type of dual battery management system is installed.

A simple cheap solonoid will charge both batteries at the same time regardless of the level in each battery.

A so called smart solenoid (and other battery managers pirhana, some rotronics etc will only allow the aux battery to charge only when the starting battery reaches a predetermined level , at which time both batteries are charged at the same rate.

Some battery management systems will actually charge both batteries at different rates (more ex bleep ve rotronics etc).

AnswerID: 157855

Follow Up By: the outlaws - Wednesday, Mar 01, 2006 at 15:47

Wednesday, Mar 01, 2006 at 15:47
the unit i have is a stock standard one from arb they fitted it last november.
0
FollowupID: 412169

Follow Up By: Mainey (WA) - Wednesday, Mar 01, 2006 at 15:54

Wednesday, Mar 01, 2006 at 15:54
A simple cheap solonoid will *NOT* charge both batteries at the same time REGARDLESS of the level in each battery!

0
FollowupID: 412170

Follow Up By: Leroy - Wednesday, Mar 01, 2006 at 15:56

Wednesday, Mar 01, 2006 at 15:56
your arb or was that abr isolator...hehe anyway, the starting batt will charge first then when it gets to a preset voltage that it senses of around 13.25v it switches the secondary battery into the charging cct. the starting battery is always charged first to ensure you can always start your vehicle.

leroy
0
FollowupID: 412171

Follow Up By: Leroy - Wednesday, Mar 01, 2006 at 15:59

Wednesday, Mar 01, 2006 at 15:59
Please enlighten us Mainey.

You said, quote "A simple cheap solonoid will *NOT* charge both batteries at the same time REGARDLESS of the level in each battery!"

Well if both batteries are switched in cct......what really happens then if they are not being charged?

Leroy
0
FollowupID: 412172

Follow Up By: the outlaws - Wednesday, Mar 01, 2006 at 16:00

Wednesday, Mar 01, 2006 at 16:00
thanks

is there any benefet in swapping them over will i get longer life out of them?
0
FollowupID: 412173

Follow Up By: Groove - Wednesday, Mar 01, 2006 at 16:05

Wednesday, Mar 01, 2006 at 16:05
Im kind of curious to Mainey, if you are refering to the rate at which a battery will accept charge then ye whatever.
0
FollowupID: 412175

Follow Up By: Leroy - Wednesday, Mar 01, 2006 at 16:10

Wednesday, Mar 01, 2006 at 16:10
I personally don't see any benefit it swapping batteries over periodically. I reckon it's detremental to the starting battery because the aux batt cops a bit of a beating being dischaged at times quite heavily. You can only do this for so may cycles. Generally a staring batt doesn't like heavey disachages - it will just shorten it's lifespan.

Leroy
0
FollowupID: 412176

Follow Up By: Wayne (NSW) - Wednesday, Mar 01, 2006 at 16:22

Wednesday, Mar 01, 2006 at 16:22
Leroy,
In your last reply I think that you meant to say that the Deep cycle does not like heavy discharge.
Just nit picking :-)

Wayne
0
FollowupID: 412180

Follow Up By: Leroy - Thursday, Mar 02, 2006 at 08:14

Thursday, Mar 02, 2006 at 08:14
Nope I did mean the starting batt. The starting batt doesn't like to be heavily discharged. Do this too many times and it die.

Leroy
0
FollowupID: 412349

Reply By: Wayne (NSW) - Wednesday, Mar 01, 2006 at 15:58

Wednesday, Mar 01, 2006 at 15:58
Johno,

It will all depend on the isolating system that you have.

The way I look at it is that the alternator was designed to charge one battery at one time. So the isolating system should charge one battery at one time.

The system that i have got will charge the main battery first, then charge the second battery. I have two heavy duty batteries and it is designed to charge the second battery as a heavy duty battery. Other systems will charge the second battery at a deep cycle rate.

The life of both batteries will not be affected with either of these methods and changing them around will not be needed. Sometimes the batteries can't be swapped because of the pole position.

Now you will get all the post with all the tech advice with all sorts of numbers and fact read out of a book. I can only go by what I have and how it works and has done for over 13 years. I don't need to know all the charging rates at what temp and if it is a Sunday or not. All I need is a system that when I start the vehicle the batteries are charged.

The system I use is IBS available from TJM and the other is the Piranha.

Wayne
AnswerID: 157858

Follow Up By: the outlaws - Wednesday, Mar 01, 2006 at 16:05

Wednesday, Mar 01, 2006 at 16:05
thanks wayne thats the sorta answer im looking for i dont wanna know all the war and piece because i can tunderstand it anyway.
i just want straight advice.

thanks
johno
0
FollowupID: 412174

Reply By: richopesto - Wednesday, Mar 01, 2006 at 16:44

Wednesday, Mar 01, 2006 at 16:44
Hi guys,

Wayne has a very good point. Im sure theres many a auto-elec who can elucidate better than I....
Ive been reading a bit about RAPS for shacks and caravans....
"Other systems will charge the second battery at a deep cycle rate"

This point is (apparently) crucial when it comes to the float level (the point at which the battery stops charging) Despite all I've read I dont quite yet understand it sufficiently to explain it fully.....
Suffice to say, certain regulators/isolators will go into float level at slightly different voltage levels and you may never fully charge your battery, thus shortening its lifespan. Its important to match your battery to your isolator type. That's all Im prepared to say on my very thin level of knowledge. :-)

cheerio
richo
AnswerID: 157868

Reply By: Derek from Affordable Batteries & Radiators - Wednesday, Mar 01, 2006 at 19:03

Wednesday, Mar 01, 2006 at 19:03
This is an open question and can't be answered without more information. The thread could go on for days and members will be abusing each other by the end of it. (Again)

There are many isolators and battery management systems available. The voltages and the charge rates vary and like Groove mentioned battery type also plays a role.

If you want a straight answer without getting totally confused let us all know what batteries are fitted and in what position and if possible which isolator you have fitted.

Regards Derek.
AnswerID: 157891

Follow Up By: the outlaws - Thursday, Mar 02, 2006 at 09:51

Thursday, Mar 02, 2006 at 09:51
thanks derek

my appologies for not putting up all the information i will get it all when i get home and tell you what i have got fitted.

thanks
johno
0
FollowupID: 412376

Reply By: peter d - Wednesday, Mar 01, 2006 at 20:48

Wednesday, Mar 01, 2006 at 20:48
hi everyone, i just have a cheap solonoid with a toogle switch that i turn off and on when i need second battery charged and i haven't had a problem in over two years. but then how long should the batterys last.
peter d
AnswerID: 157917

Follow Up By: Sand Man (SA) - Thursday, Mar 02, 2006 at 03:57

Thursday, Mar 02, 2006 at 03:57
peter,

In your scenario, they will both fail together.

If one is faulty, or becomes discharged, as soon as you switch the second battery into the circuit, it will drain down to the level of the faulty one.

What do you do then?
Bill


I'm diagonally parked in a parallel Universe!

Member
My Profile  My Blog  My Position  Send Message

0
FollowupID: 412331

Reply By: Muzzgit (WA) - Wednesday, Mar 01, 2006 at 22:32

Wednesday, Mar 01, 2006 at 22:32
Johno, if your solenoid is the older style which "clicks in" as soon as the ignition is on, then both batteries are open to charge from the alternator.

If it is the newer style it will wait for the starting battery to charge back to around 13.8v before bringing the second battery into line, and will "click out" as soon as the starting battery gets below 12.5v, car running or not.

I have the newer style solenoid in my patrol with a calcium starting and wet cell deep cycle aux, and I'm not convinced this is the best setup. The deep cycle takes too long to charge and I don't think it reaches full charge properly even when it hasn't been used for 3 or 4 weeks, and I drive to work every day (15 - 25 minute trip)

I would not swap a battery that has been used as an aux to become the cranking battery unless it was an emergency.
AnswerID: 157955

Follow Up By: Mad Dog (Australia) - Thursday, Mar 02, 2006 at 10:01

Thursday, Mar 02, 2006 at 10:01
I have 35mm² welding cable running to the back of the ute and my deep cycle still doesn't charge much above 60% even after weeks of running around. I will be swapping it for either a exide extreme or an AGM. I'm yet to convince myself that the AGM is worth the extra expense
0
FollowupID: 412380

Follow Up By: muzzimbidgie - Thursday, Mar 02, 2006 at 20:36

Thursday, Mar 02, 2006 at 20:36
MAD DOG. Check out the new calcium/calcium batts.

Like AGM they can be used as one or the other, recharge very quickly and don't cost much more than a normal N70ZZ. I have only seen these in the local auto elec a few weeks ago.

I have the older style calcium/calcium cranking battery and have been told they don't like aux battery type use, but they tell me these new ones are up to it.

Cheers,

Muzz
0
FollowupID: 412550

Reply By: phil - Thursday, Mar 02, 2006 at 16:20

Thursday, Mar 02, 2006 at 16:20
A solenoid system, smart or otherwise, just connects the 2 batteries in parallel so they both have the same charging voltage.
However... having the same voltage does not mean that they have to have the same state of charge, even with identical batteries.
For example if the starting battery is fully charged and the auxillary battery is half flat the alternator will still keep the voltage on both at the regulated voltage but most of the current will flow into the auxillary because it will have the lowest internal voltage. Most alternators these days can deliver enough current to lift the terminal voltage of even a quite flat battery to 14.2 volts, or whatever it is set to regulate at, so a smart solenoid will still connect the auxillary even when the main battery is near flat. However the alternator can probably deliver enough current to charge both at whatever current they will take.

Hope this helps,

Phil I
AnswerID: 158114

Sponsored Links

Popular Products (13)