# Battery voltage vs. load vs. capacity?



## ActiveCampers (Jun 17, 2005)

My old man reckons his leisure batteries are shot, and hence we are gathering info for the dealer so they can be swapped under warentee.

2 batteries (110AH each ). Both fully charged with van charger for a few days.

Q1 - what should the "NO LOAD" voltage be?

We then isolate the batteries and test each one, and put a 5A load on (5A confirmed accurate).

What sort of voltage drop should we get over time, and how long can we run the 5A constant load for?


Our figures seem to show that (for Battery 1):-
As soon as 5A load on, v=12.23
1hr in, v=11.91
5hr in, v=11.15
9hr in, v=10.4 and then the electronics drop out saying battery flat.

That is 45AH usable per battery which strikes me as low (I'd expect 60-80AH usable per battery, 120-150AH usable on both?)

The second battery had a slightly different curve, but after 9hrs is still 10.4v so pretty consistent.

So - at 45-50AH usable per battery before the control unit shuts down, would you agree the batteries are our of expected performance range and due a swap by dealer?


----------



## ActiveCampers (Jun 17, 2005)

Decay graph below.

Both batteries charged together. Battery 1 tested 30 mins after charger was removed; Battery 2 tested 24 hours after charger was removed which may explain the differing starting voltages.

X = hours from start of test; Y = Voltage


----------



## joedenise (Jul 20, 2007)

I would say they are shot what is the voltage if you take them of charge and leave them for 24 hrs


joe


----------



## ActiveCampers (Jun 17, 2005)

joedenise said:


> I would say they are shot what is the voltage if you take them of charge and leave them for 24 hrs
> 
> joe


Battery 2 was left unconnected for 24 hours after charging before test, and start v=12.52 with no load. 5A load straight to 11.82 then as per graph above (red line)


----------



## ActiveCampers (Jun 17, 2005)

Incidentally this all stemmed from being sold a motorhome specifc TV that kept dropping out, and the manufacturer said for the TV to work it needs >11.8v! Hence only worked for a few mins when away from hookup....


----------



## rayc (Jun 3, 2008)

These are general voltage ranges for six-cell lead-acid batteries:

Open-circuit (quiescent) at full charge: 12.6 V to 12.8 V (2.10–2.13V per cell)
Open-circuit at full discharge: 11.8 V to 12.0 V
Loaded at full discharge: 10.5 V.

From that you can see that an unloaded battery with a terminal voltage of 11.8 to 12.0v is considered discharged.
How quickly a battery gets from a charged to discharged state is determined by it's AH capacity. This is now generally quoted on a 20 hour cycle so a 110AH battery should be capable of being loaded by 5 Amps for approx. 20 hours before it is considered fully discharged at 10.5v.

To determine how long your TV can work you will have to connect it to the battery and measure how long the battery voltage remains above 11.8v. Assuming the TV draws 3 amps then you may be surprised how little time it takes for tis to happen. Of course with two batteries in parallel the time should be doubled.


----------



## ActiveCampers (Jun 17, 2005)

TV was lasting only minutes.
Watching battery 2, and it went to 9v after exactly 10 hours of 5A load (plummeted after 9hrs) - the electronics turn it off at 9v.

So fair to say, they are not working at 110Ah or even close to.

Time for dealer to arrange a swap me thinks.


----------



## rayc (Jun 3, 2008)

ActiveCampers said:


> TV was lasting only minutes.
> Watching battery 2, and it went to 9v after exactly 10 hours of 5A load (plummeted after 9hrs) - the electronics turn it off at 9v.
> 
> So fair to say, they are not working at 110Ah or even close to.
> ...


It would be interesting to know the characteristics of the van charger. I assume it is a 3 stage charger, that is one that charges initially at 14.2v which eventually drops off to 13.8v as a trickle charge.
Is it possible for you to monitor the unloaded battery terminal voltage from discharge state and switch the charger on. What voltages do you get?
If the charger only charges at a maximum of 13.8v then the batteries will never reach full charge.

Perhaps a 12v voltage stabaliser would help for TV operation
http://www.in21now.co.uk/acatalog/DC_DC_Adapters.html


----------



## ActiveCampers (Jun 17, 2005)

rayc said:


> ActiveCampers said:
> 
> 
> > TV was lasting only minutes.
> ...


Its a special motorhome charger/gizmo/combi unit http://sargentshop.co.uk/EC325-Power-Supply-Unit

On charge, 11A charging current, voltage still 12.x v and going up (as batteries were both "flat").

When charging the vehicle battery (selectable on control panel) - I saw 13.5v before swapping to charge leisure.

The EC325 is brand new. Looking at the manual now, it says "ntegrated CHARGER 
Input 220-240 Volts AC +/- 10%, Frequency 50 Hz +/- 6%, 
Current 3A max. 
DC Output 13.5 Volts nominal, Current 25 Amps max (325 
Watts). "

edit: The TV just didn't work - dropped out on another van, and even on mine after a few hours. (Our TV runs for "days" if I so desired) so the TV itself just isn't suited. Yep we could sort out a voltage converter, but TV was brand new so just sent back and I'll point the old man towards a cheaper and less fussy TV


----------



## spatz1 (May 19, 2011)

Expensive bit of kit  

should charge 2 x 110ah to full at 14 .8 v bulk in 6 hours ....( my 20a in tandem with 4 amp van charger does )

i can draw 11a for 10 1/2 hours off those before inverter cuts out and they are the pre 2009 batteries marked at 110ah that dont give a genuine 110ah as prescribed post 2009 output standards.....


----------



## ActiveCampers (Jun 17, 2005)

spatz1 said:


> Expensive bit of kit
> 
> should charge 2 x 110ah to full at 14 .8 v bulk in 6 hours ....( my 20a in tandem with 4 amp van charger does )
> 
> i can draw 11a for 10 1/2 hours off those before inverter cuts out and they are the pre 2009 batteries marked at 110ah that dont give a genuine 110ah as prescribed post 2009 output standards.....


11A @ 10.5hrs on 2 batteries is the same (roughly!) as 5A for 10hrs on one battery that we are getting. The batteries are probably 2009 era on this van?

But not sure the charger will give out > 14v.


----------



## spatz1 (May 19, 2011)

ActiveCampers said:


> spatz1 said:
> 
> 
> > Expensive bit of kit
> ...


o crap... my batteries must be stuffed :lol: :lol: :lol:


----------



## rayc (Jun 3, 2008)

ActiveCampers said:


> rayc said:
> 
> 
> > ActiveCampers said:
> ...


Far be it for me to question a Sergeant product but my charger is 14.6 v untill the charging current falls to 2Amps when it falls back to 13.8v.


----------

