How do you check/ replace batteries

[Hessie]

Hi, I know this has all been covered in the forum before, but when reading the threads the technical jargon tends to make my eyes glaze over and the need to make a cuppa becomes all encompassing. So please can anyone help spell it out for me in a way I can understand.

 

My domestic batteries are no longer taking a full charge/ are dying way too fast. The alternator is working as they still take some charge, but I don't want to replace the bank of batteries if there is something simple wrong that can be fixed. In view of this I have a few questions.

 

- Is there some way I can check to see that my batteries are still functioning?

- Can batteries be mended?

- If they are dead, how complicated a process is it to replace them myself (considering my total lack of electrical knowledge/ willingness to try)?

- What type of batteries are best to replace them with?

 

Sorry for sounding stupid, but I guess I need to start somewhere.

[Chalky]

Hi, I know this has all been covered in the forum before, but when reading the threads the technical jargon tends to make my eyes glaze over and the need to make a cuppa becomes all encompassing. So please can anyone help spell it out for me in a way I can understand.

 

My domestic batteries are no longer taking a full charge/ are dying way too fast. The alternator is working as they still take some charge, but I don't want to replace the bank of batteries if there is something simple wrong that can be fixed. In view of this I have a few questions.

 

- Is there some way I can check to see that my batteries are still functioning?

- Can batteries be mended?

- If they are dead, how complicated a process is it to replace them myself (considering my total lack of electrical knowledge/ willingness to try)?

- What type of batteries are best to replace them with?

 

Sorry for sounding stupid, but I guess I need to start somewhere.

Gibbo is the expert on this topic but as a quick guide:-

 

- Is there some way I can check to see that my batteries are still functioning?

If you have a volt meter you can disconnect the batteries in the bank and measure the voltage of each battery. You're looking for 12.4V or more. If it's less than 12 then they're sick. 10V or less indicates a dead cell. You'll need to leave the batteries a while after charging before you measure the voltage to allow the voltage to settle down (surface charge to dissipate). If you can check the water level. If it's very low (top of battery plate showing) then it's not a good sign.

 

- Can batteries be mended?

Not normally for the type used on boats. Assume that if they're dead they're dead.

 

- If they are dead, how complicated a process is it to replace them myself (considering my total lack of electrical knowledge/ willingness to try)?

If you know the business end of a spanner dead easy. If you've not done it before take some photos of what's there as a guide. Make sure the engines not running, any chargers are disconnected and that the battery isolators are turned off. Automotive practice is to disconnect the negative (black) wires first, then the positive (red) wires - often it's a 13mm spanner 1/2" af for older ones. There may be other wires connected to the battery terminals - record where they go and make sure you re-connect them when you fit the new batteries (thus the photos). Undo any clamps holding the batteries down (there might not be any) then lift them out of the battery compartment being careful not to touch the battery terminals against anything metal - be careful since the batteries are heavy (they contain lead and sulphuric acid). If you're concerned wrap some electrical tape round the battery terminals first. Re-assembly is the reverse. Put new batteries back into battery box, fit and tighten any clamps holding them down. Connect up the positive wires first (red) then the negative (black).

 

- What type of batteries are best to replace them with?

You're looking for batteries the same physical size as the ones that came out with the terminals the same way round (avoids possible re-wiring battery box) and at least the same Amp hour rating (measurement of how much power they store). What type, where to buy them from etc is a continuous thread on here and its worth doing a search.

[Kiwipeter]

A great response Chalky - some forums get impatient with newbies - glad to see this isn't one of them.

[Nickhlx]

As to suppliers, Tayna Batteries http://www.tayna.co.uk/ is one suggestion where people have purchased from...

 

If you are on a budget, our own Vince, from this parish, sometimes has good used batteries at £25 each.... Vince1969 is his "alias"

 

Nick

[alan_fincher]

If you are on a budget, our own Vince, from this parish, sometimes has good used batteries at £25 each.... Vince1969 is his "alias"

Although if I remember correctly, it has been said that most (and possibly all?) of Vince's batteries come with something other than the standard "post" connectors that the OP presumably currently has ?

 

If so, it will not be a simple swap-over, and the OP would need to balance any saving on a good "hardly used" battery bank, against the cost of getting someone to do the rewiring, (as they don't sound to have the skills to re-terminate heavy battery cables themselves).

Edited February 14, 2011 by alan_fincher

[RobinJ]

My domestic batteries are no longer taking a full charge/ are dying way too fast. The alternator is working as they still take some charge, but I don't want to replace the bank of batteries if there is something simple wrong that can be fixed.

I take it then there is no problem starting the engine and you ar eonly worried about the domestic side!

- Is there some way I can check to see that my batteries are still functioning?

First of all do you know where they are, which ones are starter, which ones are domestic, how many are there?

 

Assuming there are two banks, at least one will be used for starting, the remainder for deomestic, these will generally be linked (-ve to -ve, +ve to +ve) by thick cables.

 

You need some sort of voltmeter. With everything switched off, measure the voltage on the starter and the domestic batteries. The starter will probably read higher than the domestic, but both should be at least 12.5V and no more than ~13.5V

If the domestic bank is reading very low (8-10V) then there is a good chance a battery has a failed cell.

The only real way to determine which one in the bank is at fault, is to remove each battery in turn and try charging it!

If you charge a battery up and then leave it disconnected overnight, it should hold its charge. To do this with a large bank of batteries could take some time!

[Nickhlx]

Although if I remember correctly, it has been said that most (and possibly all?) of Vince's batteries come with something other than the standard "post" connectors that the OP presumably currently has ?

 

If so, it will not be a simple swap-over, and the OP would need to balance any saving on a good "hardly used" battery bank, against the cost of getting someone to do the rewiring, (as they don't sound to have the skills to re-terminate heavy battery cables themselves).

 

Good point !

 

It would be possible to use an adaptor - i.e. adapt the post type from one type to another ? http://www.thefind.com/electronics/info-battery-post-adapter Not the most elegant solution, but if there are only a few to convert and the budget is tight.....

 

Nick

[Gibbo]

Automotive practice is to disconnect the negative (black) wires first, then the positive (red) wires

 

Re-assembly is the reverse. Put new batteries back into battery box, fit and tighten any clamps holding them down. Connect up the positive wires first (red) then the negative (black).

 

 

This one keeps coming up.

 

It is indeed standard automotive practice.

 

It is safe in an installation with ONE battery and only ONE connection to battery negative.

 

If there is more than one battery bank and/or if there is more than one wire to the battery negative then it can result in, literally, thousands of pounds worth of damage to onboard equipment.

 

I've seen it happen, I've seen the results of it happen, I've also filled my wallet several times from the proceeds of it happening.

 

Examples:-

 

Heart Interface Freedom 25 and Link 2000R battery monitor/alternator controller. Total rebuild required. Cost to customer in excess of £1,000. This was in about 1998. I actually did about 25 to 30 of these in total.

 

Mastervolt Dakar and early MICC. Same as above. Cost to customer £1,200. About year 2000.

 

Furuno Radar and remote duplicate display. Cost to customer: About 20 quid inspection cost. Entire equipment total write off.

 

Eberspacher heater with remote time switch. Cost to customer £450

 

All because someone disconnected the battery negative first

[Hessie]

Although if I remember correctly, it has been said that most (and possibly all?) of Vince's batteries come with something other than the standard "post" connectors that the OP presumably currently has ?

 

If so, it will not be a simple swap-over, and the OP would need to balance any saving on a good "hardly used" battery bank, against the cost of getting someone to do the rewiring, (as they don't sound to have the skills to re-terminate heavy battery cables themselves).

 

To be honest I don't have the skills for this and so will prob try purchase new and get the same type as is in at the moment.

 

I take it then there is no problem starting the engine and you ar eonly worried about the domestic side!

 

First of all do you know where they are, which ones are starter, which ones are domestic, how many are there?

 

Assuming there are two banks, at least one will be used for starting, the remainder for domestic, these will generally be linked (-ve to -ve, +ve to +ve) by thick cables.

 

 

Yes there are three domestic batteries and one starter. The domestic ones are on the opposite side of the boat from the starter one. I have had no problems starting the boat, but will check the starter battery when I check the rest (as soon as I become the proud owner of a volt meter).

 

This one keeps coming up.

 

It is indeed standard automotive practice.

 

It is safe in an installation with ONE battery and only ONE connection to battery negative.

 

If there is more than one battery bank and/or if there is more than one wire to the battery negative then it can result in, literally, thousands of pounds worth of damage to onboard equipment.

 

All because someone disconnected the battery negative first

 

Why is it different with more than one battery in a bank?

You're making me nervous, I'm starting to think I should get someone to do it and watch what they do closely.

[WotEver]

Why is it different with more than one battery in a bank?

I can't think of a non-technical way to explain (it's covered in one of the pinned articles at the top of this page which you said you'd found too technical to follow).

 

Just accept that it is, and therefore you need to turn off the isolator and then disconnect the positive connections first.

 

You may also need to consider whether you're charging your batteries sufficiently, because if you're not then you could kill the new ones quite quickly. How long have the existing set lasted?

 

Tony

[Gibbo]

Why is it different with more than one battery in a bank?

 

Don't take this as me nit-picking what you've said, instead allow me to use it as an example of why the subject is misunderstood.

 

I didn't say "more than one battery in a bank" I said "more than one battery bank". Grammatically the difference is subtle. Electrically the difference is huge.

 

With two battery banks, and a complicated negative and/or split charge arrangement, disconnecting one of the negatives can result in 24 volts appearing on 12 volt equipment (bang) or 12 volts with reverse polarity appearing on 12 volt equipment (bang).

 

Again, all because someone disconnected the negative first.

Edited February 15, 2011 by Gibbo

[kendo]

With two battery banks, and a complicated negative and/or split charge arrangement, disconnecting one of the negatives can result in 24 volts appearing on 12 volt equipment (bang) or 12 volts with reverse polarity appearing on 12 volt equipment (bang).

Thanks Gibbo. Top Tip!!

 

If I hadn't read your words on here, i too would have followed the

"perceived wisdom" of other people, and removed my negatives first.

 

I feel like i've just saved myself 2 grand.

 

Cheers..

[Peter Reed]

just a thought, have you checked the electrolyte level in the batteries?

[Hessie]

I can't think of a non-technical way to explain (it's covered in one of the pinned articles at the top of this page which you said you'd found too technical to follow).

 

Just accept that it is, and therefore you need to turn off the isolator and then disconnect the positive connections first.

 

You may also need to consider whether you're charging your batteries sufficiently, because if you're not then you could kill the new ones quite quickly. How long have the existing set lasted?

 

Tony

 

1. Does this mean I need to disconnect all positives on all batteries and then all of the negatives, or the positive then negative on each battery in turn? (sorry if stupid question)

2. Not sure how much is a long enough charge period, I run the engine a couple of hours a day when moored and generally two days a week the engine has been ran for around 7 hours/ day.

3. Existing set came with the boat when purchased in october, no idea how old they are.

 

Don't take this as me nit-picking what you've said, instead allow me to use it as an example of why the subject is misunderstood.

 

I didn't say "more than one battery in a bank" I said "more than one battery bank". Grammatically the difference is subtle. Electrically the difference is huge.

 

 

Ahhh you mean't my separate starter and domestic battery banks, not the individual batteries. I get there in the end.

 

just a thought, have you checked the electrolyte level in the batteries?

 

The answer to that one is no (i didn't realise that batteries could lose water) but I shall now.

[RLWP]

1. Does this mean I need to disconnect all positives on all batteries and then all of the negatives, or the positive then negative on each battery in turn? (sorry if stupid question)

 

<snip>

 

All the positives, then all the negatives.

 

Richard

[smileypete]

Why is it different with more than one battery in a bank?

You're making me nervous, I'm starting to think I should get someone to do it and watch what they do closely.

 

Put it this way.

 

For safety ANY connections direct to battery positive that bypass the isolator must be protected by an appropriate fuse close to the battery.

 

If this is the case then you can open the isolator and remove all these fuses, then disconnect the battery negatives first if you wish.

 

However some (many?) boats are dangerously wired with unfused connections direct to the battery positive.

 

If this is the case then it's best to remove the battery positives first. And of course ensure that any connections direct to battery positive are fused close to the battery with appropriate fuses.

 

If you'd like to learn more about boat electrics, I'd recommend having a look at Tony Brooks website or better still go one one of his courses.

 

cheers,

Pete.

[WotEver]

2. Not sure how much is a long enough charge period, I run the engine a couple of hours a day when moored and generally two days a week the engine has been ran for around 7 hours/ day.

I strongly suggest you invest in a Smart Gauge.

 

Instant elimination of guesswork when charging.

 

Sure, there are much cheaper ways of determining charge status, but they all involve a certain amount of 'faffing around' and also require a reasonable knowledge of battery characteristics. A SG simply tells you the State Of Charge as a percentage of battery capacity (75% full, 85% full etc) with no other knowledge required.

 

Tony

[Hessie]

Thanks everyone for all your help and advice, it's much appreciated. I feel a happier about tackling this problem now.

 

Though since I've learn't just how lacking my knowledge was/ is I think I shall also definately be going on a maintenance course.

 

H