dual batteries 75 series Troopy

Submitted: Saturday, Apr 21, 2007 at 21:22

ThreadID: 44580 Views:5478 Replies:6 FollowUps:19

This Thread has been Archived

Bluey221

G'day,
so who out there are the experts on dual batteries? if you know anything about this subject ca you give me some advice please? All I need to run is a 50 - 60 litre fridge and some fluros. How hard is it to install yourself?.........what brand should I go for?....... and anything else you might like to pass on would be great.
Thanks and drive safe
Joe

Back Expand Un-Read 0 Moderator Share

Reply By: Willem - Saturday, Apr 21, 2007 at 21:43

Saturday, Apr 21, 2007 at 21:43

We are all bloody experts on batteries here....but I will let some of the younger ones reply to your question

Cheers

AnswerID: 234994

Follow Up By: Rod W - Monday, Apr 23, 2007 at 10:00

Monday, Apr 23, 2007 at 10:00

Now Willem, do ya understand all that gobbledegook below... bugger if I do.

FollowupID: 496309

Reply By: Rust bucket - Saturday, Apr 21, 2007 at 22:07

Saturday, Apr 21, 2007 at 22:07

You asked for experts on this issue and I'm not one. One thing you should decide on is whether or not you want a truly independent battery management system. There are plenty of good reasons to go for this type of system but they are very expensive. By truly independent I mean one that will actually deliver the full electric current from the alternator to the second battery during the recharge phase. The absolute majority of systems are not independent at all despite some very missleading and at times downright dishonest advertising claims. This means that the second battery will only ever receive the "overflow" of current from the main battery once it is fully charged. This overflow will never be as high a current as the one direct from the alternater so the second batery will never be charged to 100% of its capacity. Appart from obviously not having as much available power as you might like, the life of the battery will be shortened because they really don't like being partially discharged all the time. The only independent system I know of (and there may well be more) is made by Rotronics. They cost about $700 just for the controler! I actually bought the Rotronics system because I wanted absolute reliability. It comes with clear instructions for self instillation. A really basic system might be a fair investment however, because you can buy quite a few batteries for $700. Everyone will have a different opinion on this issue and they all have merit. What ever you end up with just understand how it works and what the limitations will be.

AnswerID: 235000

Follow Up By: Willem - Saturday, Apr 21, 2007 at 22:26

Saturday, Apr 21, 2007 at 22:26

My Rotronics lasted 24 months and then passed away. So I binned it.

Now run a simple solenoid. But you are right in saying that not all the charge gets to the second battery.

Absolute reliabilty? There is nothing absolute about electrics or mechanical stuff.

FollowupID: 496006

Follow Up By: Rust bucket - Saturday, Apr 21, 2007 at 22:59

Saturday, Apr 21, 2007 at 22:59

Fair call Willem. The KISS principal has a lot going for it.

There you go Bluey; even the really expensive systems aren't perfect. Be very wary of the big name brands and their systems. They are expensive and are not all that much different in opperation to a simple solenoid. Which while as cheap as chips, seems to work well for thousands of blokes.

FollowupID: 496018

Follow Up By: Member - Davoe (Nullagine) - Monday, Apr 23, 2007 at 23:53

Monday, Apr 23, 2007 at 23:53

the best FULLY independant battery management system isactually pretty cheap. Has been around or years and is%100 per cent reliable
It is a cole - hersy switch

Had problems with solonoids they alow a good battery to mask a stuffed one while letting mostof the charge get thieved by the stuffed battery until when you need it most your 4by dont start and thats the first youknow of it

FollowupID: 496588

Follow Up By: drivesafe - Tuesday, Apr 24, 2007 at 07:40

Tuesday, Apr 24, 2007 at 07:40

I don’t where people get these ideas from because once the motor is running, the alternator's voltage is higher than any of the batteries connected, by what ever means, to the vehicle’s electrical system so the alternators voltage is going to go to ALL the batteries at the amount of current that each battery needs.

There is no such thing as an “overflow of current” from one battery to another.

The only thing that causes problems when charging multiple battery arrangements is the use of wire that is too thin.

If you use adequately thick enough wire, both positive and negative, then the only thing that will control the amount of current each battery gets, is each individual battery’s own current requirements and no one battery in the system will effect the charging of any other battery in the system.

FollowupID: 496599

Follow Up By: Member - Davoe (Nullagine) - Tuesday, Apr 24, 2007 at 09:24

Tuesday, Apr 24, 2007 at 09:24

Personall experence thats where drivesafe. While the alternator may well be providing heaps of charge. Electriciy is inherently lazy just like water - it takes the path of least resistance which a stuffed battery provides.
I was in that boat with a previos vehicle as well as work vehicles one stuffed battry leading to the good battery going flat

FollowupID: 496621

Follow Up By: drivesafe - Tuesday, Apr 24, 2007 at 11:29

Tuesday, Apr 24, 2007 at 11:29

Hi Daveo, if a battery is that stuffed then there is no way you are going to start the vehicle in the first place.

If you read Rust bucket’s post, he is talking about a situation where the motor is already running, otherwise, the first battery could not get fully charged.

Furthermore, ANY decent dual battery controller would have separated the good battery from the defective battery while the motor wasn’t running.

Only with a manually operated set-up might you have a problem.

In any case, if the stuffed battery is drawing that much current while the motor is running, then nothing is going to be working for long, not only any other batteries.

Cheers

FollowupID: 496638

Follow Up By: Member - Davoe (Nullagine) - Tuesday, Apr 24, 2007 at 14:44

Tuesday, Apr 24, 2007 at 14:44

I was refrring specifically to solnoid operated duel batt setups . I know little of rotronocs, redarcs etc. A full manuel one yo pick up a stuffed battery when starting on the batterys seperatly as part of your pre start
You can disagree with me as much as you like but like i said it is knowledge gained from previos experience and not just a oneoff either

FollowupID: 496679

Follow Up By: drivesafe - Tuesday, Apr 24, 2007 at 22:44

Tuesday, Apr 24, 2007 at 22:44

Again, even with a solenoid system, if the battery is that stuffed that it would be capable of pulling most if not all the current being produced by the alternator then it is highly unlikely that you will be able to start the vehicle in the first place.

BTW, I do agree with you on one point Davoe, knowledge gained from previous experience is worth it’s weight in gold and as I have put many, many thousands of dual battery system out there, I also have a little experience in this area.

Cheers

FollowupID: 496806

Follow Up By: Member - Davoe (Nullagine) - Wednesday, Apr 25, 2007 at 02:06

Wednesday, Apr 25, 2007 at 02:06

got zero intrest in how many duel batt setups youve installed - anyone can do it. But how many bosses vehicles have you had to drive to there place , jump start there vehicle and then drive it to the auto leccies place tofind the charging systm is fine delivering about 13.8 to both batteries but when both have been put on the charger only one comes up on a load test - replace that battery and all is good
PERSONAL EXPERIENCE BEATS THEORY EVERY TIME

FollowupID: 496833

Follow Up By: drivesafe - Wednesday, Apr 25, 2007 at 06:25

Wednesday, Apr 25, 2007 at 06:25

Davoe, as you were the one that raised the point about having experience, I just thought I’d point out that there are plenty of people on this site with genuine experience and try to put it to good use for the benefit of other site uses.

Genuine experience that would have made it obvious to replace the regulator as well, because the 13.8 charging voltage is probably half the problem.

Any one with the slightest knowledge of vehicle electrics know that 13.8 volts is absolute border line for charging automotive batteries and if there is any sort of a problem, particularly like a stuffed battery then there is no way such a low charging voltage is going to be able to maintain the vehicles electrics and yes personal experience, when you learn from it, beats ignorance any day.

Cheers

FollowupID: 496848

Reply By: Alan H (Narangba QLD) - Sunday, Apr 22, 2007 at 07:59

Sunday, Apr 22, 2007 at 07:59

I've always only run a simple solenoid and do not have battery problems. I run a fridge, lights and sometimes an inverter.

Our style of travel is to keep on the move so this keeps the battery charged. Would require something else if you went to a location and camped for a week. We tend to change camps every night due to lack of time and so many places to go.

I think the trick is not to short change the cables. Make sure the main cables connecting the batteries are large

AnswerID: 235054

Reply By: Phillipn - Sunday, Apr 22, 2007 at 08:10

Sunday, Apr 22, 2007 at 08:10

Go to www.fridge-and-solar.net
All the info you need is their.

AnswerID: 235056

Reply By: furph - Sunday, Apr 22, 2007 at 08:42

Sunday, Apr 22, 2007 at 08:42

Because the vehicle manufacturer wants a reasonable life from the battery, the alternator is regulated to a maximum voltage output of 13.8 - 14.1v. (sensed at the alternator). This will recharge the battery to about 70% of its capacity. The fact the alternator has a current output of (say) 100a. is to deal with power loads (lights, w/wipers, heater fan etc.)

Having said that, the optimum charging rate for a 12v. battery is 14.7v @C/10 a.
(14.7 derived from 2.45v/cell x 6 =14.7, C/10 being battery ahr. capacity/10, 100ahr. battery/10 = 10amp charge rate)

This 14.7v. has to be at the battery terminals, so voltage drop in the cable/connections has to be taken into account. I also follows that to thoroughly recharge (not simply "surface" charge) a discharged battery it will take around 12hrs.@ 10a. Periodically the charge voltage should be increased to 15.5v. to "equalise" the battery cells.

Because the vehicle alternator initially whacks 30-40a. into the battery then fairly quickly reduces back to 8-10a. does not mean the battery is charged but that the battery voltage has become equal to the control point of the alternator voltage regulator.
As installed in the vehicle the alternator will never fully charge a 12v. battery. A check with a hydrometer will quickly verify this.

A system which addresses the problems here is to use a 12/240v. inverter near the starting battery with a 3stage 240/12v. battery charger located adjacent to the aux. battery. This is the system used for years in motorhomes. Of course, for this to work, the engine has to be running otherwise the starting battery suffers!

Collyn Rivers, who used to post on here, has written some excellent books on this subject, highly recommended reading.
firph

AnswerID: 235062

Follow Up By: drivesafe - Monday, Apr 23, 2007 at 11:20

Monday, Apr 23, 2007 at 11:20

furph, quite a number of batteries CAN NOT be boost charged or charge equalised as it will permanently damage the battery.

Before anybody tries to charge equalise a battery, go to the manufacture’s web site and check to see if your specific battery can tolerate this sort of charging.

Another point, besides the fact that using a 240vac inverter while driving is not only unbelievably dangerous and not just to the user but should your vehicle be involved in an accident, you will be endangering the lives of rescuers. If a vehicle’s wiring and dual battery set-up is installed correctly with the right material, there is no reason for using an inverter/battery charger in the first place.

Last but not least, probably the best site on earth for battery related info is this one.

Just remember when going through the info on this site that most of it relates to car battery use but the info is still excellent.

Good Battery Info

FollowupID: 496335

Follow Up By: drivesafe - Monday, Apr 23, 2007 at 11:22

Monday, Apr 23, 2007 at 11:22

furph, quite a number of batteries CAN NOT be boost charged or charge equalised as it will permanently damage the battery.

Before anybody tries to charge equalise a battery, go to the manufacture’s web site and check to see if your specific battery can tolerate this sort of charging.

Another point, besides the fact that using a 240vac inverter while driving is not only unbelievably dangerous and not just to the user but should your vehicle be involved in an accident, you will be endangering the lives of rescuers. If a vehicle’s wiring and dual battery set-up is installed correctly with the right material, there is no reason for using an inverter/battery charger in the first place.

Last but not least, probably the best site on earth for battery related info is this one bellow.

Just remember when going through the info on this site that most of it relates to car battery use but the info is still excellent.

Good Battery Info

FollowupID: 496336

Follow Up By: drivesafe - Monday, Apr 23, 2007 at 11:23

Monday, Apr 23, 2007 at 11:23

Sorry for the double post

FollowupID: 496337

Reply By: ross - Monday, Apr 23, 2007 at 10:13

Monday, Apr 23, 2007 at 10:13

Im all for the KISS projects too. I wanted to run 2 batteries with a marine battery switch.
I had a marine battery switch on a 60 series but alas I sold it before I got to fully explore its possibilities.

Is it ok to run a deep cycle battery for the fridge and a starting battery for the engine and swap over to the deep cycle battery occasionally to recharge it when your on the move?

AnswerID: 235249

Follow Up By: drivesafe - Monday, Apr 23, 2007 at 11:05

Monday, Apr 23, 2007 at 11:05

Hi ross, once the motor is running, there is no reason why you can't simple parallel the two batteries, as the alternator’s output voltage is going to be higher than ether battery so it will charge both batteries at the same time.

FollowupID: 496327

Follow Up By: ross - Monday, Apr 23, 2007 at 11:26

Monday, Apr 23, 2007 at 11:26

By paralel do you mean permanently. I want the switch so I can isolate the batteries or run them in tandem if I want.

FollowupID: 496338

Follow Up By: drivesafe - Monday, Apr 23, 2007 at 12:14

Monday, Apr 23, 2007 at 12:14

Hi again ross, I gather from what you have posted, but correct me if I’m wrong, you switch from the cranking battery to the auxiliary battery to charge the auxiliary battery.

All you need to do is have an ON / OFF type battery switch and once the motor is running, simply connect the auxiliary battery to the cranking battery.

When you turn the motor off, turn the battery switch to the OFF position to isolate the auxiliary battery again.

You don’t need to disconnect the cranking battery at any time, in other words, you don’t have to, as you put it, “swap over“ to get both batteries charged.

Cheers

FollowupID: 496349

Follow Up By: ross - Monday, Apr 23, 2007 at 19:11

Monday, Apr 23, 2007 at 19:11

I dont think that is the set up Im thinking of. The marine battery switch allows you to use battery 1 or battery 2 or both 1 and 2 at the same time or you can switch both battery off in case of fire or if the vehicle is not in use for long periods

I had one once before ,great set up

FollowupID: 496452

Follow Up By: Mainey (WA) - Monday, Apr 23, 2007 at 23:48

Monday, Apr 23, 2007 at 23:48

Ross posted-> "is it ok to run a deep cycle battery for the fridge and a starting battery for the engine and swap over to the deep cycle battery occasionally to recharge it when your on the move"

Ross, I presently use a 5 yo Deep Cycle battery as my Cranking battery, or do you mean swap the actual 'charge' over to the Deep Cycle battery? the 'marine battery switch' does that for you, as you posted.

FollowupID: 496587