Maintainance deep cycle batteries

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

A one word answer Yes.

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

Phil.
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.

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.

Cheers
Phil

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.

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).

BEAM ME UP SCOTTY


Hooroo
Ray

By the way, the amplepower reg is $US450. BEAM ME UP SCOTTY


Hooroo
Ray

Phil.
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.

Eric,
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.

And while you're there, phone up Rotronics and talk to them. They have an excellent technical service.

Just another reference in relation to battery sulphation:
http://www.rotronics.com.au/TechnicalP2.AuxiliaryBattery.htm

Phil

Phil.
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.

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.

Sincerely,
Phil G

Phil.

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.