Charging Voltage Math

[Nesting Zombie]

Very confused over my Voltage math !.

MO has got a NEW 225a/h sealed wet lead acid battery.
It’s also got a NEW Victron Orion 30a B2B Charger thingy.
SOwhen the voltage at the terminal shows 12.3v I’m kinda thinking that’s used around the 80a from the Battery.
So WHY does it ONLY take 10min on Bulk, & 25mun on Absorption to put it BACK onto Float Fully Charged !.
That’s only say 20amp of charge put back in .

 

[Robmac]

Can't help I'm afraid Paul.

But it's Maths!

 

[Nesting Zombie]

Fanks Rob, (Jam on my fingers, & Bad Spelling )

 

[trevskoda]

Wildbus is the man for that.

 

[Nesting Zombie]

I’m still keeping the jam though !

 

[wildebus]

Very confused over my Voltage math !.

MO has got a NEW 225a/h sealed wet lead acid battery.
It’s also got a NEW Victron Orion 30a B2B Charger thingy.
SOwhen the voltage at the terminal shows 12.3v I’m kinda thinking that’s used around the 80a from the Battery.
So WHY does it ONLY take 10min on Bulk, & 25mun on Absorption to put it BACK onto Float Fully Charged !.
That’s only say 20amp of charge put back in .

Well, number 1 is you need to get a battery State of Charge Monitor as using a Voltage Reading to do this is very unreliable.

35 minutes of running on a 30A charger would not even be 20Ah of charge but let's say it is?
1) Charger is not working correctly or configured correctly?
2) If charger IS good then battery was not down 80Ah?
3) If using the reading of 12.3V is an accurate way to evaluate the Battery SOC and 20Ah got it full again, then the battery is nowhere close to 225Ah in capacity and is probably faulty. Is the 12.3V taken directly off the battery terminals?

Given this is your home and you need to know the level of power in your battery, I think a Battery Monitor is step 1 and checking the charger setup is needed.

 

[Nesting Zombie]

The reading was taken from the digital display that is on my inverter (No Load taken from it)

I’m actually just parked up now & the app thingy is saying-

Just turned the engine off & it now says-

I will see what it says tomorrow before starting it up,

 

[Nesting Zombie]

Apparently the voltages shown are from the INPUT & OUTPUT Terminals of the Charger itself.
So the INPUT reading would be ‘FROM’ the Engine start Battery & OUTPUT reading would be ‘TO’ the Domestic 225ah Battery at a guess

Obviously it’s showing OFF at the moment because the engine is off, & therefore the Charger ISNT allowing it to go through the B2B charging unit, so the INPUT reading is showing a fully charged Engine start battery dropping & settling having just been switched off.
& there is no OUTPUT reading as,,,,Well the B2B charging unit isn’t allowing the discharge from the Engine Start Battery.

. I think

 

[merl]

Apparently the voltages shown are from the INPUT & OUTPUT Terminals of the Charger itself.
So Input would be ‘FROM’ the Engine start Battery & OUTPUT would be ‘TO’ the Domestic 225ah Battery at a guess

Yes, correct but as David has already mentioned you really should check the battery voltage with your multimeter AT THE BATTERY POSTS while it's charging to eliminate the possibility of a high resistance connection somewhere that's messing up the readings and charging.
From the fact that it's charging and then going into float that indicates that you've got decent current but you'll need one of those DC clamp meters to actually confirm
.If a battery is charging faster than you'd expect you typically see faster discharge too and that's typically because the battery has lost its capacity to store and release energy, basically it's very likely cream crackered.

 

[Nesting Zombie]

I will get the multi meter on it tomorrow & get some readings

 

[wildebus]

Also, something to bear in mind generally - and makes the situation more confusing - the closer a Lead Acid battery is to full charge, the less charge it will take, so if the battery was that close to being full the 30A maximum the charger will put out will end up being a lot lower.
One of the limitations of the Orion-Tr Smart is it has no way to display the current in or out which makes knowing what is really happening more tricky.

 

[Nesting Zombie]

Yeah, you would have thought that a cpl of fitted meters on the unit would have been helpful.
My cheap inverter has got one & I find it a Brilliant’Guide’ as it’s connected straight to the Battery Terminals.
This is the reading (with NO Load) at the moment-

 

[wildebus]

12.8V with no charging would be a full battery. It doesn't tell you how much capacity the battery has though and once you are using it the voltage is pretty useless at telling you what you have left.

Something that is fairly common when a battery is playing up is people don't think their battery is a problem, they are just surprised how fast their charger is (the smaller the effective capacity of a battery is, the faster the charger fills it up).

 

[Nesting Zombie]

Making sense .

I’ve just been using this as a rough indication of what’s happening power wise-

So in my mind I couldn’t work out 35min of charge would only have given around 20amp at best, That means I should have seen readings up around the 12.5 mark & NOT the 12.3 I actually seen !.

It IS however interesting that , the 35min charging, in line with My GUESS of 20amp being put back in the battery over that time WOULD IN FACT BE around the 10% mark of the 225Ah Battery capacity .

Oh it makes your head POP .

Ooo Dinner time !


Well according to. Everything I can think of, MOs Batteries are full at the moment & are settling down on the voltages. I’m actually not using anything other than my phone charger tonight, so will take some readings in the morning.

 

[merl]

Making sense .

I’ve just been using this as a rough indication of what’s happening power wise-
View attachment 137036
So in my mind I couldn’t work out 35min of charge would only have given around 20amp at best, That means I should have seen readings up around the 12.5 mark & NOT the 12.3 I actually seen !.

It IS however interesting that , the 35min charging, in line with My GUESS of 20amp being put back in the battery WOULD BE around the 10% mark of the Battery capacity .

Oh it makes your head POP .

Ooo Dinner time !


Well according to. Everything I can think of, MOs Batteries are full at the moment & are settling down on the voltages. I’m actually not using anything other than my phone charger tonight, so will take some readings in the morning.

Thing is though, using a chart like that is at best a very rough guesstimate of remaining capacity and ONLY works if the battery is in good condition, with older/ knackered batteries the chart will be a mile off.
Capacity meters that monitor the energy going into and out of the battery are way more accurate and relatively inexpensive.