Jump to content

battery replacement tips


pquinn

Featured Posts

hi all,i am contemplating replacing my battery bank before winter and was wondering if any one had any tips ie.do's and donts,for a person who has never done this operation before.i would say its a pretty standard setup as in 4 110ah leisure,1 starter,sterling battery charger and invertor,2 alternators.is there a sequence i should follow or just rip em' out and stuff the new ones in[if ya' know what i mean].allso i read here somewhere that when you buy new batteries that sometimes they can have dud cells,how do i ensure against this when i go to buy new ones.i was just going to replace them with the same ones that came with the boat,which i am pretty sure are just standard exide car batteries.they have lasted over four and a half years liveaboard (genny charging and no landline).so i dont see the point in fixin' what is not broken.am i mistaken?

thanks in advance.

  • Greenie 1
Link to comment
Share on other sites

To replace the batteries it's as simple as...


  1. Remove the negative connection from the bank
    Remove the links between the batteries
    Remove the positive connection from the bank
    Remove the batteries
    Place the new batteries in the same place and reverse the above procedure.

 

I'm firmly in the "If it ain't broke don't fix it" camp, so go ahead with the same batteries if you've got a good price on them.

 

Dead cells are rare, but if these are wet batteries then your hydrometer will indicate a dead cell pdq.

 

Tony

Link to comment
Share on other sites

Remove the negative connection from the bank

 

Unfotunately you're showing your age Tony :lol:

 

Sometimes this is ok, but it depends upon the installation too much to make this the general rule. If there is more than one connection to the negative this can be lethal for equipment.

 

The general rule should be... "Whatever you do, don't disconnect the negative first. Disconnect all the positives first"

Link to comment
Share on other sites

Unfotunately you're showing your age Tony :lol:

 

Sometimes this is ok, but it depends upon the installation too much to make this the general rule. If there is more than one connection to the negative this can be lethal for equipment.

 

The general rule should be... "Whatever you do, don't disconnect the negative first. Disconnect all the positives first"

Oh well... I'm getting quite used to being wrong :lol:

 

Cheers for the correction :lol:

 

Tony

 

so we're all in agreement then?

:lol:;)

Link to comment
Share on other sites

Oh well... I'm getting quite used to being wrong :lol:

 

Cheers for the correction :lol:

 

:lol:

 

The problem is mainly (though not entirely) due to all this modern equipment.

 

Take the case of something like a Mastervolt combi with the battery monitor. Often the battery monitor will have its own connections directly to the battery bank. Then the "remote" cable between the monitor and the inverter. If you take the main battery negative cable off, and the inverter is switched on (or switches itself on because of the messing round with the grounds - a common occurrence because it crashes the remote) then the inverter tries to pull its negative return current through the remote cable. At best it melts the cable, at worst it destroys the remote. In the case of a Heart Freedom with Link 2000 this also causes a small problem in the inverter that later results in a great big bang when full power is restored.

 

The same thing can happen with central heating boilers that have a timer. And lots of other kit.

 

Removing negatives is a bloody nightmare for electronic equipment.

Link to comment
Share on other sites

I always switch off my isolator first and check there is no power on the system. Then I disconnect the negatives. I don't see the point in replacing batteries till they've been tested. I do an open voltage test and then test each cell for specific gravity. Also, it's important to make sure the terminals are clean and that there is no tracking across the battery.

I once met a couple of boaters who came to renew their entire battery bank. They'd been having serious charging problems. I tested a battery and it registered flat as a pancake. The electrician who refitted the new battery bank winded up with holes all over his shirt and trousers because there was battery acid all over the place. I myself suffered damage to my multimeter - a light blemish of the casing.

It turned out later I found the battery terminals were rusted to the point they'd not been connected to charge.

 

To replace the batteries it's as simple as...


  1. Remove the negative connection from the bank
    Remove the links between the batteries
    Remove the positive connection from the bank
    Remove the batteries
    Place the new batteries in the same place and reverse the above procedure.

 

I'm firmly in the "If it ain't broke don't fix it" camp, so go ahead with the same batteries if you've got a good price on them.

 

Dead cells are rare, but if these are wet batteries then your hydrometer will indicate a dead cell pdq.

 

Tony

Link to comment
Share on other sites

But shouldn't everything (other than perhaps a battery monitor such as SG) have its neg connection to the main neg stud on the hull?

 

Tony

 

But that's no good when it should be like that, isn't like that, someone pulls the neg off and wrecks £2,000 worth of inverter and battery monitor. I've seen the results of this many, many times.

 

It's just far easier to say "FFS don't remove the negative first".

Edited by Gibbo
Link to comment
Share on other sites

But that's no good when it should be like that, isn't like that, someone pulls the neg off and wrecks £2,000 worth of inverter and battery monitor. I've seen the results of this many, many times.

 

It's just far easier to say "FFS don't remove the negative first".

So you can't stand back and say "You really shouldn't have wired it like that" then?

 

:lol:

 

Tony

Link to comment
Share on other sites

So you can't stand back and say "You really shouldn't have wired it like that" then?

 

:lol:

 

Tony

 

That's exactly what I used to say as the poor customer handed over half his life savings for having his inverter and battery monitor rebuilt :lol:

Link to comment
Share on other sites

hi all,i am contemplating replacing my battery bank before winter and was wondering if any one had any tips ie.do's and donts,for a person who has never done this operation before.i would say its a pretty standard setup as in 4 110ah leisure,1 starter,sterling battery charger and invertor,2 alternators.is there a sequence i should follow or just rip em' out and stuff the new ones in[if ya' know what i mean].allso i read here somewhere that when you buy new batteries that sometimes they can have dud cells,how do i ensure against this when i go to buy new ones.i was just going to replace them with the same ones that came with the boat,which i am pretty sure are just standard exide car batteries.they have lasted over four and a half years liveaboard (genny charging and no landline).so i dont see the point in fixin' what is not broken.am i mistaken?

thanks in advance.

Something worth doing with new non sealed batteries to remove the tops and look for a lip or bar at the bottom of the 'filler well'. Check the acid is up to this level, if not the battery may well be underfilled with acid, so it would be worth the supplier double checking.

 

If possible give the batteries a 24hr charge to 100%, then check the S.G with a hydrometer and put it on a sticky label nearby for future reference.

 

cheers,

Pete.

Edited by smileypete
Link to comment
Share on other sites

  • 1 month later...

Something worth doing with new non sealed batteries to remove the tops and look for a lip or bar at the bottom of the 'filler well'. Check the acid is up to this level, if not the battery may well be underfilled with acid, so it would be worth the supplier double checking.

 

If possible give the batteries a 24hr charge to 100%, then check the S.G with a hydrometer and put it on a sticky label nearby for future reference.

Also after a 24hr charge to 100%, if possible let them sit disconnected for 24 hours (for 'surface charge' to dissipate), then check the voltage with a decent meter make a note of that too.

 

cheers,

Pete.

Link to comment
Share on other sites

  • 3 weeks later...

But that's no good when it should be like that, isn't like that, someone pulls the neg off and wrecks £2,000 worth of inverter and battery monitor. I've seen the results of this many, many times.

 

It's just far easier to say "FFS don't remove the negative first".

 

Easier no doubt and in the specific circumstances quoted probably the best of two evils BUT I think this is highly dangerous advice unless very heavily qualified - especially on a canal forum where metal boats are probably more than the norm and many boat builders seem to take delight it placing batteries under steel decking.

 

One slip of the spanner when removing positives first on many metal boats will get you a dead short and on a number of occasions I have seen the results where that ended up with exploding batteries. The equation is risk wrecking £2000 of equipment which seems to have been poorly wired or risk your eyesight.

 

It is up to each of us to draw our own conclusions - especially for anyone with isolators in the positive.

Link to comment
Share on other sites

OK to expand on what Tony said, maybe it should be...

 


  1. Isolate any connections on the 'wrong' (ie battery) side of the battery isolator.*
    Open the battery isolator.
    Remove the negative connection from the bank
    Remove the links between the batteries
    Remove the positive connection from the bank
    Remove the batteries
    Place the new batteries in the same place and reverse the above procedure.

*Should be easy if they're fused as they ought to be!

 

cheers,

Pete.

Edited by smileypete
Link to comment
Share on other sites

OK to expand on what Tony said, maybe it should be...

 

 

*Should be easy if they're fused as they ought to be!

 

cheers,

Pete.

 

I do not see how having a take off on the battery side of the isolator can cause the problem Gibbo identified unless the master switch is turned off leaving the feed on the battery side live. In this case disconnecting the negatives one at a time with the isolator turned on should kill all negatives at the same time as the last post is disconnected.

 

I do see how it could occour if the "extra" negative wire was taken from some other point on the bank rather than the negative end of the bank, but we are back to poor wiring practise.

Link to comment
Share on other sites

I do not see how having a take off on the battery side of the isolator can cause the problem Gibbo identified unless the master switch is turned off leaving the feed on the battery side live. In this case disconnecting the negatives one at a time with the isolator turned on should kill all negatives at the same time as the last post is disconnected.

 

I do see how it could occour if the "extra" negative wire was taken from some other point on the bank rather than the negative end of the bank, but we are back to poor wiring practise.

I think Gibbos point is that where there's interconnected equipment, removing negatives one at a time can cause a mischief.

 

For example you remove a negative that goes to the diesel heater, then it tries to fire up and destroys the timer! :o

 

cheers,

Pete.

Link to comment
Share on other sites

I think Gibbos point is that where there's interconnected equipment, removing negatives one at a time can cause a mischief.

 

For example you remove a negative that goes to the diesel heater, then it tries to fire up and destroys the timer! :o

 

cheers,

Pete.

 

It can not fire up if there are no negative connections still connected to the battery bank when others have been disconnected and that implies connections to "mid bank" battery negatives.

 

Perhaps I did not word that as well as I should, I am talking about disconnecting battery posts not negative "feeds" from applinaces..

 

If the appliance negatives are connected to more than one battery negative post then What Gibbo says in undoubtedly true. However with all the appliance negatives connected to the "end of bank" negative post then lets say there are three batteries in the bank: disconnect negative 1 and the other two batteries still supply 12v to the end post or if its the end post clamp that has been taken off then the other two batteries will still supply the clamp with 12v neg. or less depending upon how well the connection is between appliance leads and the post. Ditto with battery 2. When battery 3 is disconnected then the whole negative circuit is lost to all the negatives whichever side of the master switch they are connected.

 

In fact one could use Gibbo's argument to make a good case for fitting the master switches in the positive which I do not agree with.

 

We have endless discussions about the correct way to connect batteries and none of them advocate sprinkling the appliance negatives along the bank. I thought that we had established that they should all be at one end.

Link to comment
Share on other sites

<snip> I am talking about disconnecting battery posts not negative "feeds" from applinaces..

 

<snip>

 

I've inherited a built-in steel-sided battery box ... it is nigh on impossible to get a spanner on the battery posts without touching the spanner against the sides ... and, indeed I did raise a spark the first time I tried to undo the positives first (thankfully no damage done) ... since then I've put isolators on both the positive and negative feeds for both the starter and the domestic banks ... I switch all of them off first, then disconnect the positive posts first.

 

(.... waits to be told this is all wrong)

Link to comment
Share on other sites

This isn't rocket science.

 

A battery monitor needs to have a permanent feed. If it doesn't have one, it can't monitor the batteries.

 

An inverter doesn't need to have a permanent feed.

 

So, when you turn the isolator off, the inverter has no feed, but the battery monitor does have a feed.

 

If the isolator is in the negative then when you switch the isolator off, the battery monitor still has a feed (because it bypasses the master switch) but the inverter does not have a negative return.

 

If that battery monitor is also the remote for the inverter (Link 2000 with Heart inverters, MICC with Mastervolt inverters etc) the inverter actually does still have a negative. Through the little remote cable and the battery monitor.

 

If the remote (the battery monitor) tries to switch the inverter on then the inverter will try to draw its battery negative current through the remote cable and the remote.

 

At best this will result in a burnt out remote cable. At middling it will blow the remote up, at worst (as it did with the Link 2000 and Freedon inverters, the earlier Mastervolt combi and MICC or with the early MICC and Dakar) it leaves a latent problem in the inverter that then goes BANG as soon as it gets its proper battery negative. Grand's worth of damage, instantly.

 

Because someone didn't know that putting the isolators in the negative was a stupid idea.

 

Same thing happens with certain diesel heaters using a remote timer/thermostat.

Link to comment
Share on other sites

I might be being thick here, but, if all the negatives are at one end of the battery bank (as they should be & mine now are) and all the positives are at the other end (ditto) if you removed a pair of links between two batteries would this not effectively kill the whole system?

 

Steve :unsure:

Link to comment
Share on other sites

:lol:

 

The problem is mainly (though not entirely) due to all this modern equipment.

 

Take the case of something like a Mastervolt combi with the battery monitor. Often the battery monitor will have its own connections directly to the battery bank. Then the "remote" cable between the monitor and the inverter. If you take the main battery negative cable off, and the inverter is switched on (or switches itself on because of the messing round with the grounds - a common occurrence because it crashes the remote) then the inverter tries to pull its negative return current through the remote cable. At best it melts the cable, at worst it destroys the remote. In the case of a Heart Freedom with Link 2000 this also causes a small problem in the inverter that later results in a great big bang when full power is restored.

 

The same thing can happen with central heating boilers that have a timer. And lots of other kit.

 

Removing negatives is a bloody nightmare for electronic equipment.

Would it help to fuse any connections that bypass an isolator in the negative batt cable?

 

cheers,

Pete.

Link to comment
Share on other sites

Would it help to fuse any connections that bypass an isolator in the negative batt cable?

 

Yes it can do and is indeed often used. Many ABYC standards now demand it. For instance a fuse panel with a 200 amp +ve feed into it and a (say) 3 amp negative feed into it (for return LED currents etc) really needs the negative fusing.

 

If possible I try to avoid it as much as possible because of the huge number of other problems it can cause. I'll do almost anything involving redesigning entire systems in order to avoid such situations.

Link to comment
Share on other sites

Hi

I want to remove my batteries I have read your pinned thread but still confused too technical for me.

I have three domestics and engine start one isolation switch for domestic and one for engine.

Do I just turn off isolations switches and disconnect negs first then pos and reconnect in reverse

I have no battery monitor ect.

  • Greenie 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.