Charging Voltage Math

Hi ya Merl,
Well I would have thought the same as you, That the ‘Bulk’ time of 14.7v at near to full pelt would stay on for longer until Battery is around 80% charged, Then Dropping down on to ‘Absorption’ Still at 14.7 in this case but less & less Current until it’s around 97% full & goes on to ‘Float’ (13.8v) at a trickle to Top off.
But ‘Bulk’ seems to always be around the Minute or 90sec mark irrespective of the hours parked up. & THATS what I don’t understand.

Note, Mo has a pretty consistent & acceptable draw of 1.5 to 2amp per hour running ’Stuff’ aboard 24/7 so that’s anything around the 40amp per 24hr mark.
I’m then Guessing that once I use Lights, Water Pump, Phone Charging it would be around 45amp per any 24hr period aboard normal, Rising to around 50amp if I run the Heater at a guess 🤷🏻‍♂️.

I just don’t understand HOW I can use say 40amp from the battery, Then have 40amp replaced by a 30amp charger in around 40 Minutes 🤯🤔🤯
 
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Nesting Zombie said:
I just don’t understand HOW I can use say 40amp from the battery, Then have 40amp replaced by a 30amp charger in around 40 Minutes 🤯🤔🤯
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Simple answer to that is....YOU CANT! so something else is going on.
How old is your battery?
Approximately what is the wiring distance and gauge of cable between the Leisure Battery and the DC-DC charger?
 
About 800mm from Starting Batt to Charger, About 800mm from charger to the new 225ah Leasure battery.

All joking aside ive just switched the engine off -
IMG_7534.png

I’ve got Heat, Power, Nothing has failed, it’s all working as it should, I just can’t get my head around the Mathe‘S’ (👍) & that annoyed me.

I think it could be too many ambiguous readings from questionable quality meters, & I should get someone to fit a proper meter & test the system.

👍
 
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Despite just getting three electrical answers right on UC 😝 I hate trying to remotely diagnose these things.
I'll throw this in, how's your solar connected, if you have it, and could that be interfering with the charging figures.
 
colinm said:
Despite just getting three electrical answers right on UC 😝 I hate trying to remotely diagnose these things.
I'll throw this in, how's your solar connected, if you have it, and could that be interfering with the charging figures.
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Good wasn't it? I got some of them right tonight but not the electrical ones.
 
Robmac said:
Good wasn't it? I got some of them right tonight but not the electrical ones.
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I was surprised that they couldn't answer several easy questions, but then if you know the answer it's easy, if you don't it's hard. I was very impressed with the winner of tonight's Mastermind.
 
This is a new one on me !.

Started engine 10:22 this morning &
Charger went straight on to Bulk charge as normal.
Bulk charge ended & switched to Absorption 10:36. About 6min longer than normal, but ok 🤷🏻‍♂️.
However it Stayed on Absorption for 3h & 5min until I switched the engine off at 13:44 with it STILL not switching to Float ! 🫣😳
(No eggy smell, Smoke or over heating visible).
I hope I notice the difference in a better battery start capacity tomorrow morning 🤔.

Now.
I’ve got an Orion B2B 12/12/30 charger that charges the battery to 80% on Bulk before switching to Absorption.
I’ve got a 225Ah battery so that means it would have had around 45amp to go.
3hr & 5min later it was still in the process of putting this 45amp in on absorption !.
Normal take between 30 or 35min like clockwork
 
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Sooo. The first thing to grasp is that the output of the charger is connected to the battery, therefore the output voltage of charger and the battery voltage are the same. We've touched on how these two voltages can in fact be different due to resistance but for now let's assume a perfect world with perfect connections and perfect cables and view the battery voltage equal to charger output voltage.
A charger is simply an elaborate power supply, it's able to control it's own voltage and also limit it's output current, BUT and here's the bit that you need to get your head around to understand fully what's going on, IT LIMITS IT'S OUTPUT CURRENT BY ADJUSTING (lowering) IT'S OUTPUT VOLTAGE.
So, if we have a 30A charger which is set to a bulk voltage of 14.5 volts then the charger will attempt to deliver 14.5 volts into the battery BUT if the current reaches 30A then it will lower its output voltage enough to limit the current to exactly 30A.
So when you started the engine this morning the battery was sufficiently flat to be capable of drawing more than 30A so the charger lowered it's voltage sufficiently to keep the current at 30A, the output voltage would be lowered to maybe 14.2V in order to limit the current.
As the battery absorbs power from the charger it's voltage and hence the output voltage at the charger begins to rise slowly, all the time the charger will be delivering and maintaining exactly 30A and the voltage will be less than 14.5v but creeping up slowly. This is the BULK stage where the charger is delivering it's maximum permissable current of 30A and a slowly increasing its voltage.
When the voltage reaches the setpoint voltage of 14.5v the charger now MUST maintain the battery at exactly 14.5v, if it were to keep pumping in 30A the voltage would rise higher than this so it maintains the 14.5 volts by limiting the current, this is the ABSORBTION stage and the battery will be maintained at a constant voltage of exactly 14.5v, in order to do so the charger lowers it's current delivery and current will gradually decrease down from 30A as the battery becomes further charged.
The absorbtion continues for either a set time (between 1/2 and hour to 2 hours) or until the current drops below a preset level(something like 1/2 an amp to 1.5A) depending on the design of the charger, some charger's use just a timer, some use just the low level current sense, some use both but whichever method is used at the trigger point the charger stops delivering 14.5 volts and now delivers 13.5V, the battery is now in float mode.
 
I would still stick with my original recommendation of getting a Battery State of Charge monitor. Having that will tell you far more accurately about what is happening generally with your charger as well as being useful all round, especially in a vehicle you live in and rely on the battery power so much.
 
Hi ya matey
Well it looks like I will be definitely getting something like that now because -
IMG_0023.jpeg

Noticed today when I took readings 😡
It is only the insulation, the cable is still intact & works, but had it’s day
 
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