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Electrical leak from batteries


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Both the house and starter batteries have been discharging quicker than I'd like. Today I measured the current leak from both……with the battery switches off.

 

Starter - 12 mA. I separated out the various connections and it seems that this leak is through the voltage sensitive relay.

House - 5 mA. I have a 24 hour essential circuits connection and this is only wired to the bilge pump.

 

Should I be investigating it further (ie. getting a sparky to look at it) or is it normal to have some leak?

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Sooooo, if you have isolated the starter, why is the VSR still connected?? This unit has an electronic sense circuit in it and 12mA is quite possible.

As for the bilge pump though, 5mA is very low, but I would not expect you to read anything, unless the level switch is electronic.

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Hi Wheels. I did not know that the VSR had a circuit in it. It has a neg and positive connection to the battery which must power this circuit. I can't trace a leak to the battery through the neg only through the pos. However I haven't checked whether there is any circuit between the house and starter batteries when all the various battery selector switches are off. Confusing.

 

I'll check out the float switch.

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I had an interesting problem some years ago... same thing a battery discharging with nothing attached! I realise internal resistance accounts for a little but what it was, was a considerable amount of wet salt and electrolyte ON the battery slowly shorting out the terminals!!!. (should have measured the resistance!! :-)

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.... what it was, was a considerable amount of wet salt and electrolyte ON the battery slowly shorting out the terminals!!!. (should have measured the resistance!! :-)

 

Probably more resistance than than a spanner WD!..................... :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol: :lol:

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anyone see the LITHIUM 12v batteries at the Boat Show? (next to Gulf Harbour's stand). Was going to enquire about them (very light, great charge and discharge capacities) then I saw the price...... $660!! :wtf:

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Both the house and starter batteries have been discharging quicker than I'd like. Today I measured the current leak from both……with the battery switches off.

 

Starter - 12 mA. I separated out the various connections and it seems that this leak is through the voltage sensitive relay.

House - 5 mA. I have a 24 hour essential circuits connection and this is only wired to the bilge pump.

 

Should I be investigating it further (ie. getting a sparky to look at it) or is it normal to have some leak?

 

That doesn't seem like a big current draw. If you are seeing your batteries go flat faster than you think they should be then you may have a problem with charging your batteries rather than discharging them. Are you sure they are taking a full charge?

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Your 12mA discharge equates to about 2 A/hr per week loss so it's not huge as FL said. The self discharge rate of a lead acid battery is around 4% a week (see below) so for a 125A/H battery that's 5A per week. It all adds up over time.

 

You may want to consider an isolation switch for the start battery just in case and perhaps a small solar panel to keep everything topped up.

 

Is this leakage causing you any issues?

 

http://www.progressivedyn.com/battery_basics.html

 

Do lead acid batteries discharge when not in use?

 

All batteries, regardless of their chemistry, will self-discharge. The rate of self-discharge for lead acid batteries depends on the storage or operating temperature. At a temperature of 80 degrees F. a lead acid battery will self-discharge at a rate of approximately 4% a week. A battery with a 125-amp hour rating would self-discharge at a rate of approximately five amps per week. Keeping this in mind if a 125 AH battery is stored for four months (16 weeks) winter without being charged, it will loose 80 amps of its 125-amp capacity. It will also have severe sulfation, which causes additional loss of capacity. Keep your batteries charged while not in use!

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and using lots of de-ionised water.

Huh?? I think you are over charging then. Does the charger have a float or trickle charge mode?? You should hardly ever have to top up. If the top of the battery is wet, then it is a sure sine you are overcharging, or maybe over filling the battery. About 5mm (10 at the most) of water over the top of the plates is all you need.

What I suggest is you top up the battery to the correct level, Disconnect and charge and then leave for 24hrs unconnected. Then measure the voltage. 12.5 -12.8V (perfect accurate reading should be 12.6V) means you have a really good battery. Under 12.5 means it is getting a little older in the tooth. Under 12.3V and the battery is not so hot. Under 12 means it is past it's used by date.

A really good test is to use a proper load tester. This will tell you if you have one or more faulty cells and how many amphrs the thing has left. You would need to find a Battery guy to find on of those things and they most likely would not loan it out. You would have to take the battery into them.

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I would check the specific gravity of the electrolyte with a hydrometer first. If you have run the batteries very low you may see a hint of black in the electrolyte... the black stuff is sulphite. If you have sulphite or the hydrometer shows that one or more of the cells are not charged then you may be able to save the battery by adding Inox to the battery and then giving it a really good charge.

 

How many amps does your battery charger put out?

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save the battery by adding Inox

It doesn't work. Well, yes it does work kind of. But it does not actually do anything to the Sulphate. The result is a very short term gain in Voltage and then the battery will die again for good. Once you have Sulphation on the plates, that is it.

Nor can those so called pulse Chargers turn sulphate back to Lead.

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Wheels - I have been relying on the charger, which is a three stage charger, to go into trickle (maintenance) mode. Maybe it is faulty. When left disconnected the batteries maintain their charge over 24h - it is the leak that discharges them.

 

 

Fineline - I don't know the output. It is a car battery charger from Jaycar so I can't imagine it puts out lots. I used to do all the SG stuff and it never really showed anything bad - now the hydrometer is broken.

 

Thanks for the input.

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save the battery by adding Inox

It doesn't work. Well, yes it does work kind of. But it does not actually do anything to the Sulphate. The result is a very short term gain in Voltage and then the battery will die again for good. Once you have Sulphation on the plates, that is it.

Nor can those so called pulse Chargers turn sulphate back to Lead.

 

I've recovered a few batteries with Inox and had good service out of them for sometime after.

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've recovered a few batteries with Inox and had good service out of them for sometime after.

I would suggest maybe the Inox was not the only thing that helped. A good hard charge may have stirred the electrolyte up or "equalised" the battery. Once a battery grows hardened Lead Sulphate Crystals, they can not be turned back into lead. There are two forms of Lead Sulphate. One is the normal PbSo4 that occurs during normal discharge. iot is part of the chemical reaction that creates the Electrons. Basicaly, the Sulpur in the Acid goes through a chemical reaction on the Lead plates and becomes Lead Sulphate. This type of sulphate is a spongy material. During a recharge, it undergoes a chemical reaction again and becomes Sulphur in the Acid. The second type of Sulphate is a hard crystal. This crystal starts to grow from the spongy material once a cell is discharged below 1.225V, or 12.4V for a 12V battery. The more the battery discharges the faster those crystals are formed. A low electrolyte exposing the plate to air also causes the crystals to grow. Once these crystals have formed, they progressively get harder and harder. Eventually they are so hard that they can no longer be turned back into lead and Sulpur. The ruff rule of thumb of a 50% discharge being the max you ever want to discharge a battery, is due to a sum of life of battery due to sulphation over cost of battery.

Because a plain 12V charger or Alternator can never fully recharge a battery, the Crystals are always being formed. A three stage charger, or one that has the ability of going into the absorbtion charge, means that the battery gets fully charged and the maximum amount of sulphation is restored back into Lead and Sulphur. The Float stage just maintains the battery voltage above that 12.4V to stop crystals from forming.

The hardened crystals become an insulator on the plates and eventually the plates are so coated they can no longer perform. A really hard shock of Voltage and or Current can knock some of the crystals for six but that can also destry the plates. So the Pulse chargers take that idea and basically give a Pulse if high energy into the plates. It depends on whos design as to whether the Pulse is high Current, high Voltage or a combination of both. There are a couple of units that do seem to do some good, but many also don't.

How Cadmium Shulphide Works is that it actually changes the chemicle make up of the electrolyte by adding Cadmium ions. But it does not actually work on the crystals themselves. Eventually they are all used up and the result is more damage done to the plates. So you can get a short term entension from a battery, but it doesn't tend to last.

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Fineline - just had a look at my charger - output is 6 A, and it is a 4 stage one.

 

Wheels - After a 4 day rest while disconnected the batteries show:-

Starter - 12.65 V

House 1 - 12.72 V

House 2 - 12.56 V

I separated the house batteries and House 2 is (obviously) the oldest battery.

 

So, as far as I can determine, there is nothing wrong with the batteries or their charging. The problem remains the 'leak' and should I be doing something about it? The 12 mA and the 5 mA leaks are apparently 'not much' but they do discharge my batteries quite quickly….well, enough for me to go looking for a leak rather than thinking the batteries were not charging properly or had come to the end of their life.

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They are all reasonably good figures, but it does depend greatly on what kind of battery you have also. The newer Calcium/lead batteries tend to give a higher reading again. But after 4 days of rest, 12.5V is an OK reading for an older bank and a 12.6V reading is great. Assuking you have a good accurate multimeter ofcourse.

The 12mA draw I am not too worried about due to the electronics in the switch. But the 5mA draw from a theoretical open circuit does. You need to disconnect that circuit at various points and track down the point at where the current is going to. It maybe a we connection allowing a path between conductors. The 5ma is not a lot, but if such a problem exists, then expect that current leak to get worse and become a major problem.

One question though, do you leave the charger on 24/7? because if you can you should.

And if you have the ability to do an equalisation charge, do so. It is good to do so once a month if they are not in heavy cycle use.

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Multimeter is a cheapie digital (from Jaycar) and seems to agree with my analogue voltmeters in the boat all the time.

 

The batteries are just your normal lead wet cell type - 2x85 Ah and 1 starter with more than enough CCA's to turn over a 18hp engine.

 

The 5 mA leak is through my 24h systems circuit…which only goes to the bilge pump. I'll chase it down.

 

Should I think about connecting my VSR through the starter battery switch instead of having its own circuit? I don't know why it is not included in the present set up….it was wired up professionally about 6 years ago.

 

What's an equalisation charge?

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Just remember that the difference between fully charged and fully flat is 0.5V. So meter accuracey is important. The analogue meters are often not that great. But even most cheap digital multi's are fairly accuarte.

The VSR I assume is for protecting the start bank form being discharged to much??? Personally I prefer a charge splitter and to keep the start battery completely for start only, most especially if you have seperate house banks.

Equalisation charge: The Electrolyte in a battery is a mixture of 35% suphuric acid and 65% water. Acid is heavier than water and wants to settle out of the water. So then you have a poorly performing battery. An equalisation charge causes the battery to rappidly gas and it stirs the Eletrolyte up. Normally a low current but high voltage is used. Often 17 or more volts. When this charge is used, it is recommended that all other electrics are turned off. Most manufacturers recomend this to be done montly.

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