Thread: BATTERY CHARGING in 4WDs–How to get it right - What do people reckon of?

Originally Posted by Geedublya

A question for Traxide.

I've seen a few people saying that AGMs need at least 14.6v to charge fully and as alternators are usually a maximum of 14.4v this is harmful and a DC to DC is needed?

Since my D4 had two AGMs and they lasted quite well I'm sceptical but I did look up manufacturers specs for some AGMs and a voltage of 14.6 -14.8 was specified for deep cycle AGMs.

Hi Mate and that data causes problems that battery manufacturers could resolve by them being more detailed about charging requirements for their specific batteries.

You, like most people look at that statement and because it is so vague, you think 14.6 - 14.8v is the required charge voltage or the battery will not be charged.

This is a common mistake and not of your doing.

That voltage is actually the MAXIMUM voltage that a given battery can be SAFELY charged with, and going any higher will result in damage being done to the battery.

They fail to tell you this little bit of "TRIVIAL" info.

The reality is that most AGMs can be fully charged with as little as 13.5v and some can achieve a fully charged state with as little as 13.0v.

BUT and there is always a but, the lower the voltage, the longer it takes to charge a battery and some of Fullriver's batteries can be charged with voltages as low as 13.0v and the "BUT" is that it will take around 30 hours to bring their battery from flat to fully charged.

Originally Posted by DAMINK

My isolator does infact charge one first then the other mate.
Here is a quote from a supplier of a similar product to mine.

"When the engine is started, the starting and auxiliary batteries are separated allowing only the starting battery to be charged. When the charge voltage reaches 13.3 volts the VSR engages allowing both starting and auxiliary batteries to be charged. "

Which isolator?

I ended up getting a Redarc by stealth(ie. I didn't buy it, brother did, but then didn't use it, so I did).
The Redarc connects after about 3 sec or so after a start. no matter how to treat the engine after the start. rev it to high heaven or just leave it at idle, it only takes about 3 sec.
Even if the battery is 'dead flat'(ie. below 10v first up).

That is, the alternator can't have charged the dead flat start battery in 3 sec, and then connected the Aux? That dead flat ended up being a dud with a dropped cell and subsequently replaced under warranty.

But like drivesafe said, these VSR are just that voltage sensing not battery charge state sensing .. so as soon as the alternator pumps out it's 12.7v(min) but more like 14+ volts, the solenoid waits it's pre programmed switching time(about 3sec in the case of the Redarc) and it switches the Aux into the grid.

Haven't see ASPW's current vid yet, I'm a bit of a fan .. not because of his breadth of knowledge, he just has a good sense of humour, presents well, albeit a bit commercialised as Eevo said.
Even without seeing his vid, I can almost feel it's just pandering to some company with a vested interest to sell some 'must have' flavour of the month accessory.

1. Ignition on, motor not running.
2. Motor just started, idling, throttle stabbed to kick regulator in.
3. 8 minutes idling.
4. 10 minutes, lifted to fast idle.
The volt meter is 40' from the batteries, probably more in cable length.
20180824_103435.jpg20180824_103458.jpg 20180824_104500.jpg 20180824_104649.jpg

Hi again Ian and while the last photo shows good voltage, the others show a very slow voltage rise.

My suggestion would be to check all your connections.

Also, how often do you drive it?

And for how long when you do drive it?

Thanks for your time Tim. It's rarely driven, I've just replaced the batteries so I can start and run it regularly. It's still undergoing conversion. The old story, either time or cash poor.

ian, can you throw a "trickle" charger on it so they are kept full?

Only if self contained, ie solar.

Originally Posted by V8Ian

Only if self contained, ie solar.

This is the best option.

I take it the solar is connected permanently?