Maintainance deep cycle batteries

Submitted: Sunday, Feb 29, 2004 at 14:52
ThreadID: 10895 Views:2001 Replies:6 FollowUps:15
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I have just purchased a new deep cycle battery for my auxillary set up. The paperwork that came with it states " new batteries will only reach full capacity after 20-50 cycles " has any one found this the case that the charge capacity becomes better after some use. Any comments would be appreciated .
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Reply By: Wayne (NSW) - Sunday, Feb 29, 2004 at 15:06

Sunday, Feb 29, 2004 at 15:06

Sorry I can't answer your question, but you might be able to answer mine. In the paperwork that came with the battery, does it mention any thing about the rate of charge or how long it should take to fully recharged.

With any battery, using them will prolong the life cycle. This could be the case with the battery, the more it is used the better it is. Just thinking out loud.

WayneAlways Out'N About
AnswerID: 48651

Follow Up By: Member - Nobby - Sunday, Feb 29, 2004 at 15:31

Sunday, Feb 29, 2004 at 15:31
I have been going through the same problem myself. I have 2X105 DC Trojans and running one Evakool off them. Went away for two weeks and they seemed to go flat overnight (12.8v to 11.8). Rang Trojan and they said that they mustn't have been fully charged to start with. I had them on a 15amp charger for a full day before leaving and assumed that was enough. When I came back, gave the Batteries to Trojan to test and they said the power was down a bit but they would give them a good charge for me. Got them back on Friday and hooked the fridge up to see what would happen. As of 10 Min. ago I have used approx .2Volt (12.6 - 12.4V) which equates to 32amp, so I guess they need a real good squirt after several uses.I used to put them on charge for a day, once a month. I may have to go longer as they were obviously not getting enough.Jack at sleep
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Follow Up By: -OzyGuy- - Monday, Mar 08, 2004 at 19:48

Monday, Mar 08, 2004 at 19:48
A one word answer Yes.

FollowupID: 311367

Reply By: ThePublican - Sunday, Feb 29, 2004 at 16:58

Sunday, Feb 29, 2004 at 16:58
Try any and all anyone would want to know about batteries.
AnswerID: 48658

Follow Up By: Wayne (NSW) - Sunday, Feb 29, 2004 at 17:42

Sunday, Feb 29, 2004 at 17:42
I need another bex. Everthing you wanted to know about batteries and then some more.

Thankyou Publican I don't know how you found the site, but it is good

WayneAlways Out'N About
FollowupID: 310472

Reply By: Roachie - Sunday, Feb 29, 2004 at 20:54

Sunday, Feb 29, 2004 at 20:54
I keep my Exide Orbital (blue top) in the camper trailer on almost permanent trickle charge, but also leave one of those el-cheapo 8w flouro lights running constantly too and also have a Megapulse on it too.
My understanding is that it pays to keep a load on the battery, but also keep it charged up.
Seems to work okay.
I used to have a wet cell deep cycle battery, but once they started to lose their charge, it would take a bloody long time on my little charger to come back to full more deep cyclers for me.
AnswerID: 48682

Reply By: Member - Peter- Sunday, Feb 29, 2004 at 21:19

Sunday, Feb 29, 2004 at 21:19
You will certainly need to put those deep cell suckers on charge for a good week or so. They build up a charge fairly quickly and then take a bloody long time to get the full charge into them. One day a month wont do it.

Depending on your battery charger output you can take days to charge a 70amp/hour wet cell. So size, as always, really does matter.


AnswerID: 48686

Reply By: Phil G - Monday, Mar 01, 2004 at 09:03

Monday, Mar 01, 2004 at 09:03
I believe the problem here is the charging systems on the newer vehicles.

All regulators sense voltage and attempt to keep it about 14-14.2 volts. But the newer alternators also have "current sensing". They monitor how much current is coming out of the alternator. They measure current by detecting the millivolt different at two points between the alternator and battery.

Typically what happens is that the current output is high immediately after starting the vehicle - mine shoots up to 14.3 volts. When the alternator's current output drops off to a lowish level (my guess is about 3-5 amps), the regulator drops the voltage. It does this to protect the battery from overcharging and prolong its life. My voltage will drop below 13.8 volts when on the highway on a long trip, and has been down to 13.5v. This is at a time when you expect the battery to be 100% charged.

I think this system works - a friend's Prado is still on its original battery after 6 years. Main problem with this system is it will not fully charge wet cell Deep Cycle batteries. I suggest to people to either use a starting battery or gel cell for auxillary batteries.

The alternator/regulators was designed for starting batteries with a low internal resistance, that accept high charging currents.

While its good to read the battery FAQs, what we really need is an alternator/regulator FAQ.

AnswerID: 48718

Follow Up By: Eric Experience. - Monday, Mar 01, 2004 at 22:42

Monday, Mar 01, 2004 at 22:42
I am interested in you current sencing theory, where did you get that from? The voltages and times you mention are about normal for standard charging system. If you measure the votage at the referance piont which is where the output of the alternator is connected to the mian loads ie the common piont of the fusable links, the voltage will be constant, if you measure the voltage at the battery it will rise as the charge reduces and if you measure the voltage at the alternator it will drop as the battery charges. The modern vehicles use a resister between the common piont and the battery to limit current which is why you can not charge a second battery by connecting it in paralel with the mian battery but you must charge it from the common piont via a small resistance. Eric.
FollowupID: 310630

Follow Up By: Phil G - Monday, Mar 01, 2004 at 23:51

Monday, Mar 01, 2004 at 23:51
Hi Eric,
As I said, current sensing is one of the factors that the regulator uses to determine the voltage it regulates at.

My sources are a 4wd mechanic with 30+ years experience and it has been discussed over the past couple of years on the Landcruiser email lists.

To my knowledge, vehicles don't actually use a "resistor" but measure the small voltage drop that occurs when current flows through any length of wire - might even be the fisible link.

You CAN charge a second battery in a parallel system. That is the way most electronic isolators are wired. When I start my vehicle and the batteries have been connected by the isolator, they both will read a higher voltage to indicate that they are both charging. The only other limiting factors in the charging of the second battery is the additional resistance in the wiring, connectors, isolator and especially the earth from the aux battery which needs a fat earth to the motor. All this creates some voltage drop when the aux battery is drawing 30-40 amps during the initial phase of recharging.

Diode systems may be the exception (because they have 0.7V voltage drop) to which you are referring, but they are largely in the past.

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Follow Up By: Phil G - Monday, Mar 01, 2004 at 23:56

Monday, Mar 01, 2004 at 23:56
Just to add, that my whole point here is that the newer vehicles don't hit the wet cell Deep Cycle batteries with enough voltage to charge them fully. This is easily seen with the other people's responses on this thread.
FollowupID: 310643

Follow Up By: Mad Dog Morgan (Geelong) - Tuesday, Mar 02, 2004 at 11:09

Tuesday, Mar 02, 2004 at 11:09
For anyone not prepared to accept a compromise with the charging system after market smart regulators are available at a price. They have temperature compensation and the ample power reg can be set for different battery chemistry and perform equalization, how smart is that.

Amplepower Smart Alternator Regulator:

Fast, Full, Multi-Step Charging
Automatic Compensation for Battery Temperature
Adjustable Dual Current Limits
Automatic Equalization Termination
`Smart' Error Lamp Output Identifies Problems
`Smart' Status Lamp Indicates Charge State
Dip-switches select Charge Set-points
Compatible with all Battery types
Synchronizes operation with Energy Monitor II, H1 unit
Lockable at 13.8 (27.6) Volts
Easy Installation with pluggable terminal block
Precision Reference Control Over Time and Temperature
Field Driver is Short Proof
Signals available for remote error and status indicators
Voltage runaway indication even without engine running
Operates parallel solenoid for cross charging house and starter battery for any charge source, (battery combining function).


FollowupID: 310661

Follow Up By: Mad Dog Morgan (Geelong) - Tuesday, Mar 02, 2004 at 11:14

Tuesday, Mar 02, 2004 at 11:14
By the way, the amplepower reg is $US450. BEAM ME UP SCOTTY

FollowupID: 310663

Follow Up By: Eric Experience. - Tuesday, Mar 02, 2004 at 23:42

Tuesday, Mar 02, 2004 at 23:42
I agree with you that the second battery does not get fully charged. If you read you own answer you will see the problem, if the current is limited to the mian battery by the loom resistance then you can not expect to charge a second battery, that is why it is so important to connect the second battery to the common piont where the voltage is higher and constant and not connect it to the main battery.
Just a few minutes with a good meter and you will work it out. Your mate who talks about current sensing, have you got a phone number for him as I would like to find his source. Eric.

FollowupID: 310790

Follow Up By: Phil G - Wednesday, Mar 03, 2004 at 15:29

Wednesday, Mar 03, 2004 at 15:29
I went looking on the net for you. and this is what I came up with:
Rotronics site

They say its a temp effect in the new alternators. My observation is that there's a significant current effect. I still maintain that there is no deliberate resistance in the charging circuit. Wire to isolator must be hooked up directly to the batteries (unless its a "primitive" diode system).

The whole point of all this is that deep cycle batteries do not get properly charged by modern alternators putting out 13.5 volts, and lose capacity and die early.
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Follow Up By: Phil G - Wednesday, Mar 03, 2004 at 15:30

Wednesday, Mar 03, 2004 at 15:30
And while you're there, phone up Rotronics and talk to them. They have an excellent technical service.
FollowupID: 310864

Follow Up By: Phil G - Wednesday, Mar 03, 2004 at 15:48

Wednesday, Mar 03, 2004 at 15:48
Just another reference in relation to battery sulphation:

FollowupID: 310869

Follow Up By: Eric Experience. - Thursday, Mar 04, 2004 at 22:32

Thursday, Mar 04, 2004 at 22:32
I feel I must explian my posting to you. When reading the postings on this forum I was amazed at the amount of misinformation that was/is posted so I tried to put some of it right but mostly got told I was wrong or ignored so I gave up. I was reading your coments on the charging system and I thought that you had the best understanding of the theory of all the postings, so I then thought if I could just correct your error then you would be able to correct others as you are a well regarded by others on the forum but all I have achieved is to get your back up so let me apologise and I give up on trying to teach people about charging system untill such time as I can post a wiring diagram of a modern charging cct. Just in case you think I am an upstart I can explian that I have had a life time of R+D in this field. All the best Phil. Eric.
FollowupID: 311073

Follow Up By: Phil G - Sunday, Mar 07, 2004 at 21:36

Sunday, Mar 07, 2004 at 21:36
Hi Eric,

I have read and re-read your posts and my posts, because I'm very worried that I have missed something here, and may be spreading furphys.

I thought I'd check out my Prado with a DMM to find the "resistor between the common point and the battery" that you refer to. I put the headlights on for a little while, then started the vehicle. I then measured voltage drop between the common point and the battery + immediately after starting the vehicle, as I wanted the alternator to be putting current into the battery. Voltage drop was 0.06 volts. Starting battery was 14.30V, common point (located in the fuse box on the Prado) was 14.36V. This voltage drop is negligible, and consistent with the wiring, connectors, and the current flow at the time.

I then thought I'd measure the voltage drop between the two battery pos terminals to measure the voltage drop after the isolator allowed current flow to the aux battery - current drop over about 5ft of 8Ga cable was 0.07volts - again negligible.

I then hooked up my 30amp, variable voltage power supply to the starting battery, and checked the current output into the battery at both 14.30 and 14.36 volts - there was very little difference - not easily discernible with the resolution of a 30amp ammeter.

I would appreciate you doing your own measurements on your own vehicle. I don't discount at all what you say - I just know that on my vehicle, that is not the case.

I also checked my workshop manuals for my current vehicle as well as previous model Landcruisers, as I have manuals for back to '75. The Prado has a different setup with the alternator wires in that it has an extra wire leading back somewhere to the "common point". Its an extra voltage sensing wire.

I don't think I'm being difficult. I enjoy a technical discussion, but my measurements on my current vehicle don't fit with your description of the way a charging system works.

Phil G
FollowupID: 311281

Follow Up By: Eric Experience. - Sunday, Mar 07, 2004 at 23:24

Sunday, Mar 07, 2004 at 23:24

The figures you measured are consistant with the charging systems I am talking about. The voltage differences indicate a fialy low current was flowing at the time. If you alternator was pushing out its full capacity the voltages would be about x10. The resistance in the loom is low but significant at high currents when you consider that the difference between a half charged and a fully charged battery is about .5 volt. The extra wire shown on the later cct is the votage referance connection to the common piont. If you wish to conferm this place you meter on the common piont and then with you motor running at modest revs switch on everthing, the voltage should be constant, repeat with the meter on the alternator output and the votage will rise with load. If you repeat this test on an older vehicle the result will be the reverse because the voltage reg references the alternator output. If you consider that the output of the alternator rises as the current increases in the modern cct then someone who does not understand resistance could be fooled into thinking that the alternator is sensing current. Thanks for the reply. Eric.
FollowupID: 311284

Reply By: Mick - Monday, Mar 01, 2004 at 17:26

Monday, Mar 01, 2004 at 17:26
Peter & phill are dead correct, deep cycle batteries sometimes need a week to fully revive if they have been flattened.
The trick is to not flatten them below 12 volts, as they will take forever to trickle charge back, even with an 80 amp alternator in your vehicle, as they will only accept a small trickle charge.
The new Bosch alternators have a charge sensing regulator which will put it into overload and charge at 17 volts for a small period of time to get the charge up faster, then back off to 14.2, or even lower. But as we know your better off with a cranking or Agm battery which will accept a faster chrge than the deep cycles.
When your camping, you dont want to have battery chargers running 24 hours per day.
AnswerID: 48770

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