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24v charging problems


MattyB

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Hi all, I was hoping somebody might shed some light on a problem I have with my new setup.

 

I have a Victron MultiPlus 24/2000/50 inverter/charger connected to 2x Banner 250ah 12v batteries wired in series of course. Everything in my setup is brand new. I charge with an lpg generator. I programmed my charger to charge at a maximum voltage of 14.4v as stated on the Banner website.

 

My problem is that while charging, one battery was reading a perfect 14.4v but the other battery was reading 15v. There was a fair bit of gassing going on and a faint smell of eggs. I thought this may be due to a difference in charge level in the batteries so charged them to float independently of each other on my old 12v charger. I left them to settle for 24 hours, and upon re-connection to my new Victron unit the individual voltages were identical (within 0.01v). However this didn't fix the problem. I have dropped the maximum charge voltage to 14.1v yet one battery still gets 14.6v while the other gets 14.2v. I'm obviously very concerned about under/over charging, can anybody explain the possible cause here or if it's even something to worry about?

 

I spoke to the battery supplier and they told me to speak to Victron. Victron told me to speak to the charger supplier. They told me to speak to the battery supplier. Given that they won't help, I had hoped somebody here might!

 

Any comments will be greatly appreciated,

 

Many thanks

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22 minutes ago, MattyB said:

Hi all, I was hoping somebody might shed some light on a problem I have with my new setup.

You have a 24 volt battery bank ?

You are trying to charge at 14.4v ?

 

You cannot charge 1x 12v battery out of a pair.

 

Do you have a 24v alternator or do you always charge using the generator and Combi (presumably the combi is charging at 24+ volts ?) You should be adjusting your charger to 28.8v max

There seems to be a big surge in boats with problems with 24v electrics by folks who seem to not understand electrics.

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Assuming that the OP really means that he’s charging at 28.8V or thereabouts the most likely scenario for the problem he describes is that he’s taken a 12V tap from the series bank in order to feed his 12V appliances. If so, that wants removing and a 24V-12V buck converter using instead. 

 

This is now the third 12V / 24V problem we’ve seen on this forum in as many weeks. 

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13 hours ago, MattyB said:

Hi all, I was hoping somebody might shed some light on a problem I have with my new setup.

 

I have a Victron MultiPlus 24/2000/50 inverter/charger connected to 2x Banner 250ah 12v batteries wired in series of course. Everything in my setup is brand new. I charge with an lpg generator. I programmed my charger to charge at a maximum voltage of 14.4v as stated on the Banner website.

 

My problem is that while charging, one battery was reading a perfect 14.4v but the other battery was reading 15v. There was a fair bit of gassing going on and a faint smell of eggs. I thought this may be due to a difference in charge level in the batteries so charged them to float independently of each other on my old 12v charger. I left them to settle for 24 hours, and upon re-connection to my new Victron unit the individual voltages were identical (within 0.01v). However this didn't fix the problem. I have dropped the maximum charge voltage to 14.1v yet one battery still gets 14.6v while the other gets 14.2v. I'm obviously very concerned about under/over charging, can anybody explain the possible cause here or if it's even something to worry about?

 

I spoke to the battery supplier and they told me to speak to Victron. Victron told me to speak to the charger supplier. They told me to speak to the battery supplier. Given that they won't help, I had hoped somebody here might!

 

Any comments will be greatly appreciated,

 

Many thanks

I think the first problem is to do with the arithmetic and charger settings.

Two “12 volt” batteries in series to give “24 volt”, manufacturers recommended charge voltage for each “12 volt” battery is 14.4 volts; so you think you’ve set your charger at 24.8 volts for two of them in series. However if you measure (during charging) 14.4 on one battery and 15 on the other, then the charger must be set to charge at 29.4 volts! You then believe that you have set the charger to 28.2 volts and see 14.2 and 14.6, meaning that the charger is set to 28.8 volts!

The second problem seems to be with one of the batteries, as I wouldn’t expect to see that much difference with two new and identically spec’ed batteries. I frequently see this type of inbalance on preserved rail vehicles which have a 12 volt bank either side of the vehicle which are series connected to provide 24 volt. It’s usualy just old age and a slightly weaker cell causing the issue; not something you should be seeing with your setup.

As far as I can tell you’ve simply taken the available manufacturers data and adjusted accordingly for a 24 volt setup, not sure what everyone else is reading?

 

Edited by Eeyore
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1 hour ago, Eeyore said:

As far as I can tell you’ve simply taken the available manufacturers data and adjusted accordingly for a 24 volt setup,

From the OP's post, I'm not sure that he has the necessary skills or understanding to do that.

He specifically says he is charging with a '12v' charger, maybe he is trying to charge each of the batteries in the bank individually, having failed to sort it with the 24v Victron he has even changed to :

 

14 hours ago, MattyB said:

I thought this may be due to a difference in charge level in the batteries so charged them to float independently of each other on my old 12v charger.

I can well understand both Victron and the Battery supplier 'washing their hands' of the problem as neither of them knows what the system is like.

 

As the OP charges 'using a generator' I wonder if this is a non-moving boat (maybe doesn't even have an engine).

I did ask earlier what engine alternator was in use, but, no response yet.

 

 

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33 minutes ago, Alan de Enfield said:

I did ask earlier what engine alternator was in use, but, no response yet.

It appears that OP joined, made his first post, then left. Perhaps he only has access to the internet in the evenings?

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2 hours ago, WotEver said:

It appears that OP joined, made his first post, then left. Perhaps he only has access to the internet in the evenings?

I think a lot of people posting questions dont realise how fast the responses can be on this forum.

I've been to quite a few different forums in the last year asking questions and on some, you are lucky if they get a new response every two days.

This site has to be one of the few that can generate a few dozen answers in a day......and when the OP doesnt realise this, you end up with loads of speculation on what is going on as it is far from clear in the first post.

OP...why are you charging a 24V system with a 14V charger?  As Wotever said in post 4,  how does this work?

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Wow thanks for all of your replies! Sadly, notifications of your responses went to my junk folder hence my lack of input..

 

The problem is pretty much cleared up now after connecting a battery balancer although I do wonder why most people get away without having to use one of these. It also emerged that my voltmeter slightly overstated the voltages after I borrowed a better quality voltmeter from a friend.

 

As for the confusion about charging voltages, what I meant was that I had the charger set to 28.8v (or 14.4v per battery), and receiving uneven voltages on each battery. The 12v charger was a different unit that I used to bring the batteries up to full charge independently. There are no 12v appliances involved, only 230v. Temp sensor was fitted.

 

Anyway, like I said the problem is pretty much sorted and the voltages have levelled up and are fairly consistent with what you'd expect.

 

Thanks everyone for your enthusiastic input, sorry I was off the radar for so long!

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19 minutes ago, MattyB said:

The problem is pretty much cleared up now after connecting a battery balancer although I do wonder why most people get away without having to use one of these. 

That'll be the topic for Part II before too long, I imagine!  ;)

Glad you got it sorted and thanks for updating all those who'd worked on your behalf.

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1 hour ago, MattyB said:

The problem is pretty much cleared up now after connecting a battery balancer although I do wonder why most people get away without having to use one of these.

They get away with it because one shouldn’t be necessary. Think about a 12V battery - that has six cells in series. They don’t require a balancer to keep the bottom 3 in sync with the top 3. Adding another battery in series simply means that you now have 12 cells. There’s no reason why the batteries should be unequal unless you’re tapping 12V off the bottom battery.

 

You state “there are no 12V appliances involved” so can you confirm that the only cable between the +ve of the bottom battery and the -ve of the top battery is the single fat battery link? Absolutely no other connection (apart from your new balancer)?

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1 hour ago, Sea Dog said:

That'll be the topic for Part II before too long, I imagine!  ;)

 

 

26 minutes ago, WotEver said:

They get away with it because one shouldn’t be necessary. Think about a 12V battery - that has six cells in series. They don’t require a balancer to keep the bottom 3 in sync with the top 3. Adding another battery in series simply means that you now have 12 cells. There’s no reason why the batteries should be unequal unless you’re tapping 12V off the bottom battery.

 

You state “there are no 12V appliances involved” so can you confirm that the only cable between the +ve of the bottom battery and the -ve of the top battery is the single fat battery link? Absolutely no other connection (apart from your new balancer)?

Hmm, Part II already - we got there rather quicker than I thought we would! :D

 

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57 minutes ago, WotEver said:

They get away with it because one shouldn’t be necessary. Think about a 12V battery - that has six cells in series. They don’t require a balancer to keep the bottom 3 in sync with the top 3. Adding another battery in series simply means that you now have 12 cells. There’s no reason why the batteries should be unequal unless you’re tapping 12V off the bottom battery.

 

You state “there are no 12V appliances involved” so can you confirm that the only cable between the +ve of the bottom battery and the -ve of the top battery is the single fat battery link? Absolutely no other connection (apart from your new balancer)?

 

Indeed, I used to work on 400 volt batteries, so 200 cells in series, with no balancer required.

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I figured for an extra £60 the balancer couldn't hurt, and gives me some peace of mind at least. But it does appear to have helped.

 

There is no other cable between the batteries, however, due to space restrictions the batteries are kept one above the other rather than side by side, meaning that the joining cable is 500mm long (50mm2 section). Would this longer joining cable be responsible for any issues?

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28 minutes ago, WotEver said:

Nope. It’s a mystery. 

Do the batteries have a date stamp? Are they both more or less the same age?

 

That is the only reason I can think of for the differing voltages, where the older battery has a faulty cell, unless there was an unidentified 12 volt tap.

 However it doesn't explain why they both charged properly when individually charged, so I'm inclined to think there is an unidentified 12 volt tap.

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I think the OP was saying that he separated the batteries and charged each one individually on a 12 v charger to float stage. What is confusing me (not difficult of course!) is how would he be able to take independent readings of two batteries in series? If being charged at 24v or thereabouts, it wold read the same on wither terminals. If he is getting a 12v reading then he's charging a 24v bank at 12v in series!?

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51 minutes ago, Markinaboat said:

I think the OP was saying that he separated the batteries and charged each one individually on a 12 v charger to float stage. What is confusing me (not difficult of course!) is how would he be able to take independent readings of two batteries in series? If being charged at 24v or thereabouts, it wold read the same on wither terminals. If he is getting a 12v reading then he's charging a 24v bank at 12v in series!?

 

Yes the OP says he eventually charged each battery individually from a 12 volt charger.

 

If you connect a 24 volt charger across two 12 volt batteries in series you will measure 12 volts if you put your meter across the terminals of the first battery, 12 volts if you put your meter across the terminals of the second battery and 24 volts if you put you meter across the positive of the first battery and the negative of the second battery (or vice versa).

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56 minutes ago, Markinaboat said:

What is confusing me (not difficult of course!) is how would he be able to take independent readings of two batteries in series?

Cheap digital multi-meter? both prods onto (opposite ends of) one battery, then both prods (ditto) on the other?

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