Battery help

[dave12]

Hi,

I have a couple of questions about Batteries, and would be grateful if anyone could offer some advice.

I have a Large Wet Cell Lead Acid Battery. This has been in my garage for about 12 months. Unfortunately, when I when to use it I found that all the cells were dry. So I topped each cell up with distilled water and put it on charge (6A Charger). After a couple of days on charge the voltage of the Battery was around 13V. However this just dropped right off when a load was put accross it.

So my first question is this, is this battery knackered? Is there nothing I can do to bring it back to life? The battery is quite an exspensive one and I would really like to get it going again.

Many thanks for your advice.

Dave

 

[333rocky333]

Might be worth a look in the motoring section.
I remember seeing a few similar posts there.

Personally I think if they are left dry too long, something internal happens and they become useless.

 

[big-all]

dont you need electrolite or battery acid !!!!!!!

 

[breezer]

distilled water works fine.

how ever the lead plates may have buckled.

 

[Spark123]

If the battery voltage drops off when a load is applied then the battery is shot.
If you want to be really fancy you can check the SG of the battery using a hydrometer, if it reads above 1.24 then the cell is good.

 

[blondini]

If a lead acid battery is left unused for long periods the plates become 'sulphated' and this reduces the capacity of the battery.

Depending how bad it is, it may be possible to recover some of the capacity by running the battery through several charge/discharge cycles. Just charge the battery then discharge it by leaving a modest load on it. Repeat this several times and it may improve. Don't let it get too deeply discharged at any point though as this is also bad.

PS. Always take great care not to cause any sparks in the near vicinity of a lead acid battery as they can vent explosive gasses.

 

[roberta1000]

... as they can vent explosive gasses.

<pedant> only asses say gasses </pedant>

As mentioned above if the battery has lain for 12 months (and long enough for much of the electrolyte to have evaporated) it will be next to useless. There is no realistic chance of recovering a sulphated battery which has lain uncharged for this time.

 

[blondini]

... as they can vent explosive gasses.

<pedant> only asses say gasses </pedant>

Still worth a punt with my suggestion however idiotic it may seem. There's nothing to lose and it has worked for me before.

 

[dave12]

Thanks for the replies everyone. Looks like its probably knackered then. What a shame! That battery would have been worth quite a bit too as it was quite a big one (640).

Not to worry, I just picked up another battery from the scrappies for a tenner, works fine!

What would you recommend for wintering the battery? I am using it for a boat , so it is only used 6 months of the year!

thanks again

 

[big-all]

why not cycle it with your car battery every 3 or 4 weeks!!!!!

 

[DESL]

Dave12

What is the battery used for on the boat? Is it a motor boat or sail boat?

If it is a 'engine starting' battery it can be used on the car during the winter.

Hoowever, if it is a 'domestic' deep cycle battery it will be killed by the car battery system. Deep cycle batteries need to use a different charging system than normally used on a car.

A deepcycle battery is design to supply a few amps over a long period, whereas a starting battery is designed to give bursts of 100s of amps for a few seconds.

To try and recover your dead battery (if a deep cycle) then place a 21W lamp across terminals until voltage drops to 11V then recharge using deep cycle charger and repeat discharge.

AFAIK if the termial volts drop below 10.8 V you may not be able to recover it.

All details are in a great book called "Electrics Afloat"

 

[blondini]

What would you recommend for wintering the battery? I am using it for a boat , so it is only used 6 months of the year!

thanks again

Motorcycle and classic car owners have the same problem as their babies don't come out to play in winter. Do a Google for 'battery conditioner', these are chargers which are designed to be left connected and safely maintain charge without overcharging. Some also have a routine for recovering sulphated batteries.

 

[dave12]

Hi DESL,

The battery is for a Sailing boat with an inboard engine. So it is used for starting the engine and supplying onboard lights and electronics.

The Dead Battery is not a deep cycle battery, as I got it off a 1000kVa Generator set (hence its quite big).

I suppose I could winter the battery by swapping it with the Car Battery, the only problem with that is I'll have to find the security code for my Radio

 

[DESL]

For a sailboat with inboard you ideally need twin batteries and a split charging system.

One battery for starting and a domestic battery for lighting and instruments.

You will severely reduce the life of either battery if not used for correct purpose.

Incidently what sailboat do you have - I have a Cobra 750 which I have fully fitted out with twin batteries and a battery management system & split charger fed from solar panels.

My domestic battery can run nav lights over night and instruments for 24hrs before it needs a bit of a boost.

The solar panel keeps both batts topped up when the boat is not in use.

 

[Softus]

distilled water works fine.

No it doesn't. You can replace the water that evaporates with distilled water, but the resulting electrolyte is weak sulphuric acid, not water.

how ever the lead plates may have buckled.

This happens when the battery overheats, not when it sits in a shed.