Battery Wont hold Charge

Bill,

He doesn't say what vehicle he has, but many late model vehicle charging systems output is as low as 13.2 volts. eg my 2007 Prado, 200 Series LC, and others.

The old standard of 14.2 is not applicable in all cases, so his alternator may well be quite ok.

Cheers

Frank

Hi Frank,

I accept what you're saying but if that is the case Toyota is putting alternators into their expensive 4WD's with inferior output.
Many folk would buy say a Landcruiser to tow their big rig, but also want to charge the batteries in the van while travelling. They wouldn't know the standard alternator is not up to the task.

The only solution in these cases is to upgrade the alternator to one that does the job and/or install a dc-dc charger to boost the voltage input into the auxiliary/remote batteries.

Anyone who understands DC charging principals knows that 13.2v is not enough. (even for a starting battery in my opinion)
Why then is a manufacturer like Toyota putting inferior products into their vehicles?
This would not be saving any costs on production, so the logic escapes me.

G'day Bill,

It's not just Toyota. I know the ones I quoted for a fact, and I also know other brands do it too, but not specifically which ones so I didn't name them. If you are interested you could check any of the Japanese brands and probably the Koreans.

Upgrading the alternator won't fix it, as it's all done in the EMS computer. You CAN do a cheat with a diode to increase the voltage, but personally I am hesitant to undo engineering that's been designed by people much smarter than me. I prefer the DC-DC smart charger route.

I don't think vehicle manufacturer's design engineers lack knowledge of DC charging principles, so it's not an oversight nor a deliberate attempt to install inferior products. I believe it's done in an effort to shave load off the engine and therefore reduce fuel consumption, no matter how small the margin.

(For the same reason, electric power steering is becoming more common, particularly in vehicles from Europe where fuel consumption is a priority. This is because electric PS systems only load the engine (via the electrical system) when there is a steering input, whereas hydraulic ones load the engine all the time, with constant excess pressure in the system being bled off through a relief valve.)

This charging issue has become so common in new vehicles that we should all be aware of it now. To its great shame, the automotive electrical service industry does not seem to be sufficiently aware of it. Witness the number of problems people have, and reported here and in other forums, with second battery systems installed by supposedly trained auto sparkies.

Cheers

Frank

Quote "This charging issue has become so common in new vehicles that we should all be aware of it now. To its great shame, the automotive electrical service industry does not seem to be sufficiently aware of it. Witness the number of problems people have, and reported here and in other forums, with second battery systems installed by supposedly trained auto sparkies."

The only thing new about this is that with the newer batteries the designers have reduced the hot/running voltages. From way back alternators and generators have had temperature compensation built into their regulators.

The earliest I can recount is my 1940 Austin 8. The instructions in the workshop manual gave different output voltages for different regulator temperatures. The higher the temperature the lower the voltage. The only one of my vehicles that did not have temperature compensation was the Nissan E20, the replacement non genuine replacement regulator did not have it, just as well that the battery was not in the engine compartment but way down the back.

Have a look and see what your alternator does. Just use an old cigarette lighter plug and connect it to your multimeter. Connect it to an unused outlet. Turn it on before you start your motor and you can see what is going on. When I start my motor the voltage will go to 14.5 V (or higher, depending on the ambient temperature.) As the motor warms up you can see the voltage drop. By half an hour the alternator will have reached its running temperature and voltage, generally 13.5 - 13.8 V

A lot of auto electricians will deny the existence of temperature.

Ian,

Your cheapo charger could bust an otherwise recoverable battery.

Try to borrow a smart charger.

Over 14V at idle? - I think maybe on fast idle with a hand throttle if you have one, or a stick between seat and accelerator and set it at about 1100-1200rpm.

Cheers

my 4WD my company car is a Commodore sportwagon.
Going by the readout on the gauges on the dash it has shown up to 15 v but normally it can sit on 14.8 volt nor worries even at idle.
This was checked by the RACQ when the kids flatten the battery running the laptop of the on rear socket and is very accurate.
It does have a calcium battery and they are in the back so a higher voltage may be to compensate for voltage drop over that distance.
when I tow the camper with the wagon I would assume there would be no problem charging the camper batteries to 100% charge.

Honky

Bantam,

"but to claim that you can not fully charge any given lead acid battery, with a car alternator is over stating the issue."

I just re-read the whole topic, and no-one said that. You're throwing in a red herring.

Leaving aside calcium batteries for the moment because they are a special case, if a car charging system puts out the required 14.2 to 14.4 volts and delivers that to the battery wherever it is (under the bonnet, in the camper) UNDER LOAD, then the battery will get charged.

The physics and chemistry of lead-acid battery charging determines that you cannot fully charge a lead-acid battery with an applied voltage of 13.5, let alone the increasingly lower outputs from late model vehicles.

And it's the voltage AT THE BATTERY under load that counts. Even if you have a charging system delivering 14.4 volts, if the battery is well down it may be asking for 30 amps or more. If the wiring is inadequate (and it so often is, especially in a long run from isolator to camper battery), the voltage AT THE BATTERY can be too low to to properly charge it.

Physics, chemistry, Ohm's Law - it is simple, undeniable fact. Not bull bleep , not even verging on it.

Cheers

Frank

QUOTE
"13.5 volts won't charge it - you'd be lucky to get 75% to 80% charge into it at that voltage. It looks like it's charged, but it's not. "

And if that isn't over stating the situation I don't know what is.

As for the physics and chemistry, lets concentrate on the simple basics before we diagnose some sort of complicated sysdrome.


The calcium charge resistance aside'
You most certainly WILL "Fully Charge" most lead acid batteries with 13.5 volts, but it will take some time.

It is very common and usual practice to float charge lead acid batteries at 13.8 volts indefinitely, let me assure you, you WILL "fully charge" a battery including a calcium battery from constant 13.8 volts ( calcium charge resistance aside)...but it will take some time.

The only people I have see pushing this whole "wont charge" malarky are certain battery charger manufacturers.

I have seen none of it in battery manufacturer documentation..and I have read large volumes of that over the years.

There is the calcium charge resistance issue though..extra voltage may be required to overcome that.
AND
extra voltage may be benificial.

As for the replacement alternator not solving the problem...I have receltly replaced the alternator in my hilux....there is suposed to be some amount of ECU interaction with the alternator..how much good question.
The original nominal regulator set point was 13.8 volts, the replacement alternator nominal regulator set point is 14.5 volts...I can assure you that the actual charging voltage measured has increased.

Because the majority of newer cars are comming with sealed maintenance free batteries...that contain calcium in the plates and have altered electrolite.
The higher voltage is better tolerated with newer batteries , old style screw top wet cell batteries would boil away their electrolite very quickly at 14.5 volts.


Now to the matter of voltage drop in charging cables.....unless the cables are rediculoulsy small, all the voltage drop will do, is slow the charging rate in the earlier parts of the charge cycle, and the battery nears a significant state of charge the current will drop and the voltage drop with it.


Unless of course there remains a heavy load on the end of that cable in addition to the battery being charged....again yet another seperate issue

Lets measure the charge voltage at the battery before we dis someones wiring.



Yes there may be all sorts of complicated things to discuss about batteries, but in my experience by far the most common reasons for battery failure and disapointment are in the simple basics.



Most commonly, over draining batteries, and failing to allow sufficient TIME to recharge them.



I've been dealing with batteries, for both work and play now for arround 30 years
Arround my shed at the moment there are probaly arround a dozen batteries in regular use, differing ages, types and sizes.

I regugarly service portable PA systems that have multi stage chargers built in.....but the customers can still kill a battery very quickly by continuously deep cycling the batteries and failing to allow sufficient TIME to recharge

Then of course, there is the question of "what is fully charged", It occurs to me that some people are trying to move the goal posts there.

It occurs to me that what some people are now calling "fully charged" most of us with traditional training would consider in the early stages of over charge.

The bottom line is and I see this over and over again, people fail to understand how much TIME is required to charge a lead acid battery properly.

Yes it does come back to MATHS, physics and chemistry... ( people forget or fail to understand the maths with batteries)....and all those factors limit how fast a battery can be charged....it comes down to TIME.

NOW
I have an alternator capable of delivering well over 80 amps, I have nearly new batteries in my 4wd, and a nearly new alternator, I have short very heavy wiring ( sufficient to winch off) to my second battery.

With my battery deeply discharged 11.5v, my fridges have shut down.
The best I have seen is a 40 amp charging current, this drops away very quicly to 15 amps or less. Measured with a very accurate little DC clamp meter.
As the battery charges that current continues to drop into single figures over the first hour or so.

Do the maths, how long is it going to take to fill a 120 AH battery with a progressivly reducing charge rate, and don't forget to factor losses.

remember too heat effects everything about lead acid batteries dramaticaly, including charging efficiency.

Lets stick with the simple basics, cycle as shallow as you possibly can and allow sufficient TIME to recharge the battery.
If you don't pay attention to those two things, no technology will help you.

cheers

Bit surprised this wasn't mentioned. A deep cycle battery discharges slowly and also recharges slowly. So to recharge takes time.

Also have to agree that if the lights came on and the voltage dropped a lot, then I would be checking the regulator.

shane c5

OH yess , this is one thing very commonly disregarded.

Some of the deep cycle batteries, particularly some deep cycle AGM have very low maximum initial charge rtaes.

One popular 120 AH deep cycle AGM has a maximum initial charge rate of 20 amps.....so half cycled it will take at least 6 hours to charge at the nominated rate even if you could keep the charge rate up with some sort of DC to DC buggery box.......which you wont for the entire cycle...so 8 to 10 hours is more likley the safe half cycle depth recharge time.

If you want to rappidly recharge a battery, deep cycle may not do the job..well not for long anyway.

Seems to me people want to maintain a "fuel tank View" of batteries, wishing that they could be rapidly filled and emptied, when the reality is they are a slow acting thing and they need to have a long term view.

The slower you discharge a lead acid battery and the shallower you cycle it the more efficient it will be and the longer it will last.

and it must be understood that its generally recognised that the most efficient charge rate is arround the 10 hour rate, 1/10 of the AH capacity.
And that would take a half charge battery arround 8 to 10 hours maybe 12 to "fully charge".

cheers

I've been charging batteries off variable regulated supplies for years, but let me tell you a good multistage charger is a better thing.

If you run a high continuous charge voltage, you may have issues with overcharging depending on the battery..better to stick with a lower voltage and a little more TIME.

A multistage charger will make charge stick better and quicker that any constant voltage charger

I have a couple of the Benton units from jaycar/electus....they are great things but have one problem and that is the membrane switch that changes the functions....I have replaced the switch in both of mine..that no problem for me but for the average bloke it would be a bugger.......

cheers

Ok,thanks Bantam.I have heard of them,they cost around $250 ish dollars?

They sound like they do more things to condition battery,and make charge 'stick' better.Will have to look into getting one.Feel free to advise or post links on any you feel are suitable.Thanks.

Oh hell if you want to spend $250 on a basic multistage charger...come arround to my place, I'll sort you out..and I've got a special on harbour bridges too.

You can get into a basic generic multi stage charger for arround the $50-60

step up into something half decent in a 3.5 amp unit for arround the $90

7 amps for arround $150..and a fairly respectable generic 15 amp unit for under the $200.

You can spend more on fancy brand names, but a decent generic multi-stage charger is better than an old type battery boiler.

Check out Jaycar, Altronics, the boating discounters or even Supercheap

the place is lousy with em.

cheers