Thread: DC-DC charger- which one?

Originally Posted by Tombie

Deep Cycle AGM:- AGM batteries should be charged using a charger with a mode switch for AGM type batteries. It is recommended to use a charger, current limited to 20% or 0.2C of the batteries capacity at a charging voltage of between 14.6-14.8V following deep cycle use, or 13.6V-13.8V for standby. Silver calcium batteries generally require more charging voltage (14.4 to 14.8 V)

Does my D4 know/do this ?

Brett....

Yes (if pre-14 or post software update)
The battery is Silver Calcium factory...

RoverLander, you have no idea what you are posting up about.

The voltage displayed while the motor is running is a loaded voltage and is the one you need to be able to see how the alternator and battery are working.

If you disconnect the battery and wait, for at least 12 hours, not a few hours, you will then need an OPEN CIRCUIT VOLTAGE TABLE.

Here is a LOADED VOLTAGE TABLE, the correct one to use. This is the only table relevant for RV use, like in your D4.



The monitor on the cranking battery's negative lead can only monitor the current going though the cranking battery.

ALL OTHER NEGATIVE CURRENT GOES STRAIGHT BACK TO THE ALTERNATOR VIA THE BODY, CHASSIS AND MOTOR. it does not go anywhere near the monitor on the negative cable on the cranking battery and as such, there is no way for a D4 or any other vehicle to monitor anything but CRANKING BATTERY CURRENT.

This has already been covered.

"Here is a LOADED VOLTAGE TABLE, he correct one to use. This is the only table relevant for RV use, like in your D4"


Please provide a source for this chart and how it works for variable loads on the battery. I cant imagine how a load chart would work unless the load is specified.


The material I read states that the only way to measure SOC through voltage is to leave the battery rest and then measure voltage. The chart you provide is used to indicate that. But it is open circuit and rested.


Also please explain how moving a device drawing power from the negative battery post to the car body results in different behaviour in the car voltage. You seem to be saying that it doesn't make a difference as the car cant tell anything except the cranking battery.

Originally Posted by RoverLander

"Here is a LOADED VOLTAGE TABLE, he correct one to use. This is the only table relevant for RV use, like in your D4"

Please provide a source for this chart and how it works for variable loads on the battery. I cant imagine how a load chart would work unless the load is specified.

Correct, one needs to know the current load being drawn to be able to get the exact SoC of a battery, but this table is something that can give you a rough idea of the SoC of the battery while you are driving.

As you yourself pointed out, you need to disconnect the battery and let it rest for a few hours.

I would love to see you do that while you are driving.

Folks, my comment above is in jest. Under no circumstances should you ever disconnect the leads from a cranking battery while the motor is running.

This can stuff the alternator and is the one event that can spike electronics in your vehicle.

Originally Posted by RoverLander

Also please explain how moving a device drawing power from the negative battery post to the car body results in different behaviour in the car voltage. You seem to be saying that it doesn't make a difference as the car cant tell anything except the cranking battery.

For this one, you need to go and look at the schematics of the D4 to see that the only negative current that can pass the monitor on the cranking battery's negative lead, is the current coming from the cranking battery.

Please show me where any other negative current can go from the body or chassis, up the cranking battery's negative lead, turn round and come back down again.

You do not understand the basics of how electrical circuits work, but you're an expert on how to charge batteries ????????????????

"For this one, you need to go and look at the schematics of the D4 to see that the only negative current that can pass the monitor on the cranking battery's negative lead, is the current coming from the cranking battery.

Please show me where any other negative current can go from the body or chassis, up the cranking battery's negative lead, turn round and come back down again."


I think we are saying the same thing. I was saying that any device connected directly to the negative terminal of the battery can not be measured by the shunt on the negative battery cable. Once you move the device's negative cable to the body then the current drawn by the device goes through the shunt and is therefore observed by the car and taken into account in the cars electrical energy management system. My point is that the devices current is visible to the car so the car can do its normal power management.


Still on topic and no disparaging remarks fro me....

Originally Posted by Tombie

Yes (if pre-14 or post software update)
The battery is Silver Calcium factory...

Actually, new batteries are AGM Exides, after about 2014. I saw a pile of about 7 dead ones at the dealer a couple of weeks ago, when I was picking up a new bonnet latch/switch.

I wonder if these batteries were a symptom of the 12.2V charging schema?

Originally Posted by Silenceisgolden

Nor can Drivesafe or Blknight understand it, but it is not that complicated really. The requirements of the house battery and the cranking battery are quite different, and hence different types of batteries are used and require different charging regimes.

fairly confident that I've got at least a marginal grasp on different battery technology and its requirements.

I'll offer up the same challenge as I offered up the last DC DC charger advocate that insisted his tech was better.

I'm assuming that you're using a 25 Amp DC dc charger, bring your set up along, I'll bolt in an n70 cranking battery as your start battery, hook up 400AH of flooded lead acid deep cycle batteries drain the starter to 50% soc the house batteries (as you would call them) to 0% soc as in 0V at rest and then we'll start our vehicles.

I dont care what vehicle you use or what size alternator you use to charge the cranking battery but you must use the 25A DC-DC to charge the 400Ah worth of deep cycles.

Im going to use the 35A alternator out of my series and my multi battery hookup system which is stunningly un electronic and makes some relay driven systems seem excessively complicated.

if you've got a 40A DC DC you'll have to let me take ten minutes to bolt in a 50A alternator.

First to fully charged by means of hygrometer testing of the acid in the cells of the batteries wins.

want to bet a house?

once I've gotten settled we can then repeat the experiment using one of these new fangeld D4 alternators we'll again wire up whatever youre using and your 25a or 40a dc-dc charger and I'll just go old school. maybe (since its not going to be my car) even through a traxide unit that the owner can keep afterwards (i figure I'll just bet you the cost of it) and we'll see how you go agaisnt that.

Just FYI... the last dc-dc proponent got of lightly with just the cost of a fuel load and a carton of 5 apples cider.