New charging problem

[Mitchellmoxo]

Hello,

 

So after thinking I solved the battery problem yesterday I went about concealing the cables. Tested again after concealing the cables and the charge voltage now only goes up to 13.1V max.

 

If I connect the battery charger to 1 battery I'm getting 14.V straight away, as soon as I add another I get a max of 13.5V. Does this mean it is still charging or is there now a new problem?

 

Thanks

Mitch

[RLWP]

Maybe the second battery is discharged and is dragging the voltage down

 

Richard

[Bill]

What do you get by connecting the charger to the second battery on its own?

[Mitchellmoxo]

Hi Richard thanks for the reply I have isolated each battery and checked voltage and they are all around 12.4V?

[Bill]

Hi Richard thanks for the reply I have isolated each battery and checked voltage and they are all around 12.4V?

 

I think that means they are roughly 75% charged.

[RLWP]

Hi Richard thanks for the reply I have isolated each battery and checked voltage and they are all around 12.4V?

 

There you go. When you connect the first, you aren't making a good connection, so the charger shows the volts it can deliver open circuit. The charger is pushing 14V into nothing, the first battery sits at 12.4V.

 

You are making a proper connection to the second battery, so the charger is actually charging. The voltage drops to 13.5V as it does some work charging the battery

 

Richard

[Mitchellmoxo]

Hi Richard,

 

So is this behaviour normal or is it not charging correctly when it's charging at 13.5V?

 

Thanks for your help

And if it is normal should I expect the voltage to slowly rise to 14.1V once they become more charged?

 

The thing I don't understand is if I isolate 1 of the batterys that is 12.4V and then connect the charger it goes up to 14.V so why not with 2?

[bizzard]

Leave the charger on. The voltage should gradually creep up as the battery charges up. It will probably creep up to maybe 15 volts depending on charger and then drop back to about 13.5v trickle.

[Mitchellmoxo]

Bloody batteries! Thanks for the replies just want to get it sorted before winter properly sets in

[RLWP]

The thing I don't understand is if I isolate 1 of the batterys that is 12.4V and then connect the charger it goes up to 14.V so why not with 2?

 

I think you have a bad connection on one battery - that's the 'first' battery

 

Richard

[nicknorman]

I think you just need to leave the charger on for longer. If some or all of the batteries are well discharged, you will inevitably get a lower charging voltage whilst the charger is outputting its maximum current. The voltage should gradually rise as the batteries become more charged.

 

Can I suggest you get yourself some means of monitoring the current, at the very least a DC clamp meter such as the UNI-t UT203. As I often say, you can't see electricity so without adequate monitoring/measuring equipment you are very much "in the dark"!

[RLWP]

If some or all of the batteries are well discharged, you will inevitably get a lower charging voltage whilst the charger is outputting its maximum current. The voltage should gradually rise as the batteries become more charged.

 

Just to reinforce this, with the charger disconnected - not doing any work - it will show 14 and a bit volts. If you connect it to a discharged battery, the voltage will drop and slowly rise over several hours as the battery charges

 

If you connect it to a 12.4V battery, the charging voltage will drop. If you connect it to a 12.4V battery, and the voltage doesn't drop, there is something wrong. Either the battery is faulty or you haven't made a good connection

 

Nick's ammeter suggestion is a good one. For instance, our ammeter tells me that our flat batteries take over 30 amps when we start to charge them. Four hours later, the charging voltage is sitting around 14V and the batteries are taking about 10 amps. No way will 330AH of batteries go from dead flat to 14V in four hours - our batteries are shot. Which is no surprise really

 

Richard

[bizzard]

 

Just to reinforce this, with the charger disconnected - not doing any work - it will show 14 and a bit volts. If you connect it to a discharged battery, the voltage will drop and slowly rise over several hours as the battery charges

 

If you connect it to a 12.4V battery, the charging voltage will drop. If you connect it to a 12.4V battery, and the voltage doesn't drop, there is something wrong. Either the battery is faulty or you haven't made a good connection

 

Nick's ammeter suggestion is a good one. For instance, our ammeter tells me that our flat batteries take over 30 amps when we start to charge them. Four hours later, the charging voltage is sitting around 14V and the batteries are taking about 10 amps. No way will 330AH of batteries go from dead flat to 14V in four hours - our batteries are shot. Which is no surprise really

 

Richard

My battery is on 12.4v at the mo. I'll plug my 12amp charger in and see what it reads

[bizzard]

My battery is on 12.4v at the mo. I'll plug my 12amp charger in and see what it reads

12.6 and rising, 12.9,,13,0, 13.1,steady, 13.2, ........13.3..........13.4....................13.5-13.6 and holding.

[WotEver]

12.6 and rising, 12.9,,13,0, 13.1,steady, 13.2, ........13.3..........13.4....................13.5-13.6 and holding.

If it rose that quick then like Richard's batteries, it's shot. Unless it's really tiny.

[bizzard]

If it rose that quick then like Richard's batteries, it's shot. Unless it's really tiny.

Its in good nick. I only have one 110a dom battery. 13.7 now and holding. The last time I charged it was last Thursday, only led lights and water pump use though.

[Mitchellmoxo]

Hi Bizzard like you said after about 35-40 mins it rose to about 13.9 and then my generator cut out but they were rising gradually so nothing wrong hopefully just a bit of education was needed! Thanks

[bizzard]

Hi Bizzard like you said after about 35-40 mins it rose to about 13.9 and then my generator cut out but they were rising gradually so nothing wrong hopefully just a bit of education was needed! Thanks

Yes, mines at 13.8 now. Sometime later this afternoon it'll reach about 15v and hold for a while before falling back 13.5 trickle.

[ditchcrawler]

Hi Bizzard like you said after about 35-40 mins it rose to about 13.9 and then my generator cut out but they were rising gradually so nothing wrong hopefully just a bit of education was needed! Thanks

To check that you are charging both/all batteries and there is not a bad connection measure the voltage on the battery posts while its on charge, make sure it is the posts and not clamps.

[Chewbacka]

I don't think you said the rated output (current) of your charger.

If it is fairly small, say 10Amps with a single battery that is not too discharged then the charger would drop the volts a bit to limit the current, add a second battery and the volts will drop a lot more to limit the current.

 

So you need to know the current output of your charger and the actual charge current as well as the voltage, without those 3 values it is hard to say what is wrong.

[cuthound]

I don't think you said the rated output (current) of your charger.

If it is fairly small, say 10Amps with a single battery that is not too discharged then the charger would drop the volts a bit to limit the current, add a second battery and the volts will drop a lot more to limit the current.

 

So you need to know the current output of your charger and the actual charge current as well as the voltage, without those 3 values it is hard to say what is wrong.

It's the other way round, the charger reaches its maximum rated output power when feeding into a flat battery, and this forces the charger to lower its voltage to avoid damaging the charger.

 

As the battery charges, it accepts less current and consequently the charger is within its rated output, so the voltage can rise and keep the charger within its rated power output.

Edited September 26, 2016 by cuthound

[WotEver]

It's the other way round, the charger reaches its maximum rated output power when feeding into a flat battery, and this forces the charger to lower its voltage to avoid damaging the charger.

 

As the battery charges, it accepts less current and consequently the charger is within its rated output, so the voltage can rise and keep the charger within its rated power output.

That's what he said

 

One slightly discharged battery will depress the charger voltage 'a bit'. Two slightly discharged batteries will depress the voltage 'a bit x 2'.

 

Edited for an errant word wot I never rote

Edited September 26, 2016 by WotEver

[cuthound]

That's what he said

One slightly discharged battery will depress the charger voltage 'a bit'. Two slightly discharged batteries will depress the voltage 'a bit x 2'.

Edited for an errant word wot I never rote

Whoops, apologies to Chewbacka, I misread it.

[Chewbacka]

It's the other way round, the charger reaches its maximum rated output power when feeding into a flat battery, and this forces the charger to lower its voltage to avoid damaging the charger.

 

As the battery charges, it accepts less current and consequently the charger is within its rated output, so the voltage can rise and keep the charger within its rated power output.

We are both saying the same thing as power is volts times current, so for a 'fixed' current in this case 10A (the limit of the charger) or max power the parameter to be adjusted is Voltage,

[Richard10002]

When discharged to about 40%/50% SOC, mine start charging at about 12.7V/13V and max Amps around 79A - this is the Bulk charging phase. During the Bulk phase, the volts rise and the Amps stay the same until the voltage reaches about 14.9V, (or whatever max I've set). At 14.9V the voltage remains the same, and the Amps fall until I decide they are low enough to call the batteries full, about 4-6A in my case with a nominal 450Ah bank - this is the absorption phase. At this point most chargers would revert to trickle charging at a bit over 13V and not many Amps or, in my case, I turn the genny off, stop charging for a few days, then start again.

 

In simple terms, it is normal for a discharged battery to charge at what look like low volts, and these should rise over time.