Batteries .... Am I safe?

[Luki-lusaki]

Hello helpful people. Can you give me your advice again please.
I believe one (of 2) of my service batteries has packed up. It felt a little warm, not hot, but I could smell something greasy, but not rotten eggs. It does not need maintenance.
I have moved to a new marina in Italy and know nobody. The office is closed today, but I have sent an email for an electrician.

I have turned off the battery charger. AM, I SAFE?

My battery spec is EXIDE Excell **
EB 1000 100Ah 720A(EN) 12V.

As always, thank you.

 

[pmagowan]

No Idea. If worried about a battery remove it. Then you can do some testing or leave it to the professionals. Unless you know the fault, you don't know the risk but the risk is likely to be small and mitigated/reduced by no charge current.

 

[B27]

If you disconnect the battery, be very careful of creating a spark.
The bad battery has probably created some hydrogen.

It's possible the good battery is draining into the bad battery.
This should be much less with the charger removed,
I would probably just leave it alone, with plenty of ventilation.

 

[jdc]

I am equally wary of giving advice - I'm NOT a qualified professional electrical installer - but I suggest that you might disconnect the batteries from the boat electrics¹ (carefully - ventilate well before-hand, don't make a spark, and wear safety goggles and a boiler suit or at least not much exposed flesh while doing it), and then measure the Voltage of each battery. The latter can probably be done having carried the batteries on deck (100AHr is not a very heavy battery). This would tell you and us whether you have a shorted cell in one, and in which one.

A good battery will likely have an open-circuit Voltage of around 12.5, whereas one with a shorted cell will probably show about 10.5.

(1) The professional electrician will have to disconnect the batteries in any event, but may have special procedures or measuring instruments to help him make it safer to do.

Edit: do you have a CO detector aboard? If so, is it going off? Have you placed it reasonably close to the batteries? CO alarms are usually very sensitive to H₂.

 

[B27]

But how do you disconnect a battery without risking a spark?

 

[jdc]

But how do you disconnect a battery without risking a spark?

If current is flowing into or out of a battery there may be a spark, but conversely if no current is flowing there will not be a spark. In the case that there is current flowing (why I mentioned specialist measuring instruments; you'd have to have a clamp-on ammeter which can measure down to DC) then I would do the following:

1. On the positive side of the battery, clamp on some extra leads either side of the cable you want to disconnect. Take these extra leads to a box containing an explosion-proof switch (or, simpler just leading out of a hatch to the cockpit) with the switch closed. This way, you've attached the extra leads across zero Voltage drop, so nothing will happen.

2. Disconnect the existing cable. Because by this time it is bridged by the extra ones you've just attached, there won't be a spark; ie even if there was current flowing it could only generate a few milliVolts due to the short you've just put across it.

3. Then open the switch in the non-explosive environment, breaking the current flow in the bridge. No spark in the potentially explosive environment, even if there is at the switch.

4. Now there is no current flowing, you can safely remove the battery from circuit.

You'd have to be careful not to break other connections inadvertently (such as the -Ve connections) so it needs doing in a sensible order. That's why the OP should really get an electrician to do it...

Disclaimer: I have done this sort of thing, but not for many years since I used to work with explosives and detonators (perforating the tubing in oil wells at the selected depth), so my knowledge is not guaranteed to be in accordance with modern H&S practice.

 

[William_H]

I would suggest that while jdc advice is correct perhaps the procedure is OTT. Essentially OP should leave the batteries well ventilated for some hours with not charge or discharge. If he has a multimeter check the voltage. (if not get one) The presumably the batterie are connected directly together in parallel. It should be safe to disconnect the batteries. Check the voltage of each. We might expect one battery to have a low voltage compared to the other. Leave the batteries isolated from one another for a while before this test. If one is obviously bad then connect up the good battery and charge it observing performance/ temperature. Replace bad battery when convenient. ol'will

 

[Stemar]

I would suggest that while jdc advice is correct perhaps the procedure is OTT. Essentially OP should leave the batteries well ventilated for some hours with not charge or discharge. If he has a multimeter check the voltage. (if not get one) The presumably the batterie are connected directly together in parallel. It should be safe to disconnect the batteries. Check the voltage of each. We might expect one battery to have a low voltage compared to the other. Leave the batteries isolated from one another for a while before this test. If one is obviously bad then connect up the good battery and charge it observing performance/ temperature. Replace bad battery when convenient. ol'will

I agree. Hydrogen is pretty hard to store because it disperses so easily, so the likelihood of an explosive mix is very small. Open the battery compartment to the air, have a cuppa and just get on with it.

 

[jac]

I agree. Hydrogen is pretty hard to store because it disperses so easily, so the likelihood of an explosive mix is very small. Open the battery compartment to the air, have a cuppa and just get on with it.

That would be my approach. Turn all electrics off and cover your solar panel if you have one. Ventilate the area properly then disconnect.

 

[shanemax]

But how do you disconnect a battery without risking a spark?

Use a manual dinghy pump or any manual pump to de-gas the area near the batteries. pump the gas over the side, if necessary by extending the hose. This method can also be used to get rid of a gas leak with the heavier than air propane/butane landing up in the bilge. Remember to turn off the cylinder. Do not operate anything electrical even lights until completion of pumping.

 

[PaulRainbow]

Use a manual dinghy pump or any manual pump to de-gas the area near the batteries. pump the gas over the side, if necessary by extending the hose. This method can also be used to get rid of a gas leak with the heavier than air propane/butane landing up in the bilge. Remember to turn off the cylinder. Do not operate anything electrical even lights until completion of pumping.

Hydrogen is very light and disperses quickly, trying to pump it out with a dinghy pump would be futile.

 

[PaulRainbow]

I agree. Hydrogen is pretty hard to store because it disperses so easily, so the likelihood of an explosive mix is very small. Open the battery compartment to the air, have a cuppa and just get on with it.

If the batteries are not being charged, ie no longer gassing, the hydrogen will disperse fairly quickly and soon be safe. But, if it's still on charge/gassing, even though there likely not be much gas in the locker/boat, there can easily be enough within/around the battery and that's a real explosion risk.

 

[shanemax]

Hydrogen is very light and disperses quickly, trying to pump it out with a dinghy pump would be futile.

It depends on the shape of the battery locker. If open to the air you are correct but if there is any type of overhead ceiling then you can get a gas pocket (air pocket) as it rises and has no where to go.

 

[PaulRainbow]

It depends on the shape of the battery locker. If open to the air you are correct but if there is any type of overhead ceiling then you can get a gas pocket (air pocket) as it rises and has no where to go.

How will you open the locker and get in there with a dinghy pump, without the gas escaping ?

You can't.