batteries totally flat in 3 weeks!

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ChasB

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I left the boat for 3 weeks with the batteries switched off and the charger unplugged. I got back to find both batteries totally flat! /forums/images/graemlins/frown.gif

Is this a fair indication that they weren't in good shape? They certainly won't be now! I guess it would explain why I've been having problems getting my engines to start.

But still, flat in 3 weeks..? And one is only 2 years old.

/forums/images/graemlins/confused.gif
 
Totatly flat - like 0 volts? If so, seems like battery switches are not completely isolating batteries. Put a bit of chargesinto the batteries m then use a meter to check for small leakage current.
Also, if batteries buggered, a Megapulse might restore them.
 
Yes first thing is to ensure that there is no current being drained from the batteries as you left them. So charge the batteries then use a multimeter on current range between each battery terminal and the connector that you have removed. You should not be able to measure any current. ie less than 1 ma.
Next ensure the batteries are being charged. A amp meter on the charger will indicate actual current going in. ie 10 amps for 10 hours for a 100AH battery.
Then try starting the engine. Put a voltmeter across the actual battery posts. Volts should not drop much below 10 volts when the engine is cranking.
Now put on some lights of known current drain. ie 5 amps worth should give more than 11.5 volts for 10 hours for a 100AH battery.
A bad battery will fail both the above tests dismally.

Something in these tests will indicate that the batteries are both individually dead. Or marginally OK. Or you have a electrical fault that has flattened the batteries. (make sure the battery tops are clean and similarly the back of the battery switch is clean. Marginal batteries may be worth persevering with. But my gut instinct is put any money towards new batteries rather than gadgets. (megapulse)
olewill
 
You certainly have to find the problem before connecting any new investments. Do you have an isolator in the common negative line? Lots of people connect direct to the battery for car radio memory, bilge pump etc. and if there is leakage on any of those cables the 1-both-2-off type of isolator won't stop the drain. Is the electrolyte up to level? How well charged were they before you left - how do you know?
What do you use to charge them (Smart or not) Can you get them fully charged then leave extra cables disconnected (labelled first) to see if the isolators work. Then put 1/2 the wires back if still OK 1/2 of the remaining etc. to find the culprit(s).

These questions and many more will be answered in episode 2 of "Amps Are Not Forever - The Premature Discharge"
 
Batteries !!! More than one ? If you're talking about a battery tank with two or more batteries make sure ALL batteries are the exact same make, type, size and age. If it is a mixed configuration this might be the reason why the batteries is totally flat.
 
I managed this feat last spring by leaving a voltmeter connected. You need to find the cause of the current leak.
 
[ QUOTE ]
I left the boat for 3 weeks with the batteries switched off and the charger unplugged. I got back to find both batteries totally flat! /forums/images/graemlins/frown.gif

Is this a fair indication that they weren't in good shape?

[/ QUOTE ]

Maybe, but not necessarily.

When my batteries are switched off, the monitor show a usage of 0.4A .... which turns out to be the Navtex which, according to the instruction manual, doesnt have an off switch - which is stupid, unless someone can suggest a good reason. The Navtex must be connected directly to the batteries.

The bilge pump is also connected directly to the batteries, so it runs even if the batteries are turned off.

0.4A x 3 weeks = 200A or so.
 
I'll be back on with my voltmeter later today.

2 separate batteries. One marine charger. A proper isolation switch.

Of course I'm now asking myself if they were properly charged when I was last there. I've left it all charging overnight, so will investigate today. Can't see how two completely independent batteries can both be in such bad shape and run down like that...

Maybe something silly the previous owner did (again!)
 
Richard,

Do you have a NASA Navtex? I had this problem, so installed a simple rocker switch in the positive power feed cable. This switch was located on the instrument panel next to the Navtex, and I simply switch it on every time I get to the boat and switch if off every time I leave. Seems to work well. Switch was around 32pence from CPC.

Alternatively - you could just wire the Navtex into the main battery isolator switch so it only turns on when the battery power is turned on. Leaving it without power doesn't do it any harm - just takes a few minutes to refresh itself when you turn it on.

In any case - why would anyone need a Navtex on when they're not on the boat for a sustained period of time?

Jonny
 
[ QUOTE ]
Richard,

Do you have a NASA Navtex?........ Switch was around 32pence from CPC.

In any case - why would anyone need a Navtex on when they're not on the boat for a sustained period of time?

[/ QUOTE ]

Pretty sure it's a NASA, and had also thought of either a switch or into the panel, which is connected to the battery isolator .... only discovered it was the Navtex causing the draw when I read the manual a short time ago, so havent got a round tuit yet.

I'm on the boat loads, and cover fair distances, but havent used the Navtex in anger since we left the UK in August last year. If I'm honest, I no longer know how to use it properly and will be posting about this at some point... but it's not a priority whilst I can get mobile internet access in most places.
 
There was an earlier thread on the possibility of one or more of the diodes in the alternator having failed? Or; in your case, the charger circuit.

Usually the alternator is directly wired so even isolation switches will not prevent the batteries from discharging through the A/C windings if there is a fault.
 
[ QUOTE ]
Leaving it without power doesn't do it any harm - just takes a few minutes to refresh itself when you turn it on.

[/ QUOTE ]

1.Navtex transmissions are generally made only twice per 24 hours by each station (if that, down here we find it very spasmodic). You could have to wait 12 hours or more to get updated Navtex.

2. Navtex is part of the GMDSS system which assumes that mariners have a hard copy backup and if you don't leave the set running you might miss important warnings. The solid state memory sets are not acceptable where the codes require you to carry a Navtex as the memory capacity is deemed insufficient. They are for voluntary users only.

Having said that, I wouldn't flatten my batteries leaving the Navtex on on the yacht when away for weeks (though I have solar cells) but don't forget that it replaces a regular check of Notices for many people.
 
[ QUOTE ]
This battery is ideal for EDTA+

[/ QUOTE ] That's sold as a treatment for sulphated batteries. On what evidence do you deduce that both of ChasB's batteries, especially one only 2years old, are sulphated and not discharged as a result of a current drain he still has to identify.

I am also still waiting for you to tell me what EDTA + is. I know what EDTA is (Ive used it often enough) but what is the + all about.
 
My GUESS as I can not take his battery to bits is that they have been left in a part charged state.
the plates have sulfated up .

before I did anything else I would dose with EDTA+

Very quick, easy and cheap.

I hope it works for him as it has done for me on numerous occasions.

I put a link in to your posts so he could see your concerns.

I have my own definitive proof it works.
You don't have any proof it doesn't work.

If chasB tries it there will be two of us with proof .
 
[ QUOTE ]
before I did anything else I would dose with EDTA+

[/ QUOTE ] Sorry but the first thing to do is to look for a possible small drain on the battery as EDTA (+ or otherwise) will not cure that.
The next step is too charge both, preferably off the boat, and see if they still lose their charge. If they do then EDTA is a possible course of action. If they don't then its back to the boat to determine why they lost their charge.

The fact that they have been allowed to go completely flat will have done them no favours so they may still be candidates for some form of remedial action. EDTA is one, a pulsed desulphation device is the other. It must be noted however that a pulse device does consume some power and is therefore only really suitable for use in situations where the battery is recharged regularly, as in a vehicle in daily use or a boat normally left with wind, solar or shore-power charging in use continuously.
 
Agree 100% with all of that - and would add that EDTA is the very last resort. As you say, we have to rule out leakage in the boat wiring/equipment. If the batteries are knackered then pulsers can be good. But, as you say, they use power themselves.

I'm still waiting to learn whether EDTA is different to EDTA+ or maybe EDTA R/W /forums/images/graemlins/wink.gif
 
Quick test to do if batteries are compleatly flat - disconect the batteries, leave them an hour then recheck the voltage it should be about 8v if its much less with no drain there is an probably an internal short but in anycase batteries are probably unrecoverable
 
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