Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[Stuart]

Hi, I bought from new two 6v lead acid batteries which when tested showed to both have 6 volts. I got the batteries in July and finally went on the water with them in November. They are now flat and showing 4.5 volts.

To charge them I was sold a JP Lead Acid Auto Charger '12'volts. This charged should illuminate the LED when charging, however when all connected it does not. Could someone advise, are the batteries possibly now defective and new one's are therefore required? Also do I have the correct charger, should it be '6' volts instead of '12' volts? Thanks, Stuart.

[Shipmate60]

Stuart,
If the battery voltage is very low it sometimes takes a basic charger a little time to show it is charging.
With the charger are you charging 2 x 6volt batteries in series to give 12 volts?
This charger if put on a 6 volt battery will overcharge the battery, cause internal heat which will destroy the plates within the battery.

Bob

[Stuart]

Bob,

I was putting the charger onto one of the 6 volt batteries.

I think your suggesting that they should be charged in series with the charged l have, which on reflection does make sense. If so l will try this.

Stuart.

[Seaspray]

You could get a 6v/12v charger which does the two voltages like I have. Which would give you more flexability in charging them @ 12 volts together or separately @ 6 volts.

But charge them in series as Bob says  on your 12 volt charger, and it may take time to get them up and running.

Check that your charger is delivering at least 13.2/5 volts to the batteries Chargers need to put a slightly higher voltage than the battery voltage.

You may have to knock them into shape by charging/discharging and again and again.

Mind you its a long time since July to November to sit not used or charged, hopefully you've got a good multimeter.

I've been there. Better get charging myself and some of you lads to.

Seaspray

[toesupwa]

But charge them in series as Bob says  on your 12 volt charger, and it may take time to get them up and running.

My understanding is that you should only charge 6v SLA's individually on a 6v SLA type charger. Charging 2 6v SLA's in series with a 12v charger is asking for trouble, the first battery in the 'chain' gets charged first and the second one gets nothing... the first one is likely to be overcharged and could explode...

[Seaspray]

No two batteries are the same thats why I gave the lad the option of a 6/12 volt charger. I have also charged the SLA 12 v battery with a car charger (carefully)

Ive charged a lot of truck batteries (in series) over the years and its a would have been a pain to do one at a time, but it always got the beggars started.

Just checked my 12volt batt its 12.82 volts and the 6 volt one is 6.30 volts. thats good as I haven't used them for months but I am charging anyway today for wee while

I've been there.

Seaspray

[catengineman]

I have also charged two batts from one charger with no problems

I still do for Tito Neri she has two 12v SLA and 2 6v SLA on one occasion I use just one of my chargers but had all the batts linked so it was like one bat 12v just a lot more cells.

The charge unit on the ship is 24v and that has 10 batteries to look after output is still only 24v amp hours is off the scale emg lights etc last around 18 hours.

just make sure you have good contacts

R,

[tigertiger]

I have a 48v charger and charge 4 x 12v SLAs in series. They were designed that way. No problems.

[malcolmfrary]

Any SLA is a series chain of 2 volt cells in a box.  Putting extra boxes of cells in series does no harm as long as they are the same capacity, and start the charge in roughly the same condition. 
The reason for cautioning non-electric people to charge each battery separately is that if a slightly discharged battery is hooked to a well discharged battery, the slightly discharged one will become fully charged first, and become over-charged while its mate is charging up, with the resulting probability of damage. 
When I find cells not taking a charge, I quite often remember to check that the charger is actually working and putting out the appropriate voltage.  Remembering to switch on at the mains socket(eventually) has saved me buying a few new batteries on occasion.

[Bartapuss]

Stuart the majority of SLA's are meant for standby use in alarms, computer networking systems, emergency lighting and other similar devices to keep them in a "low mode" in the event of a mains power failure and as such are constantly on a trickle charge. As these have been adopted by modellers and model boater's in particular these batteries are put to work running powerfull motors in some cases to the point when the nearly exhausted, a task for which they're not best suited or designed for. This is where the problem lies, when you say they were tested at 6v was this when you made your purchase in July only to find when you come to use them in November they were flat at 4.5 v. If this is so, as they have been left for so long the charge has naturally decayed to the point to become so discharged that they'll may be damaged internally and will not accept any charge. 4.5v sounds pretty terminal here, as even after  running to the point of exhaustion they should still show just a little under 6v if that, however this is another important point SLA's respond better if rested for an hour or so and then immediately put on charge and not left lying around for days or even weeks as this also will cause damage resulting in diminished capacity. Also to bear in mind is a SLA is designed to provide a certain amount of current over a given time frame and is  usually rated milliamps per hour or mah, in our models were pulling hundreds of times more than that.

[Seaspray]

They were for alarms originally as Bartapuss says.

Was it brand new ones you bought or old stock from alarm systems ?


Seaspray

In the old days we poured the acid out of the car/truck batteries. Then filled them with new acid. They worked a treat

 I think H & S would do their nut if you done that today.

[kiteman1]

Perhaps Stuart can clarify whether the batteries are Lead Acid or Sealed Lead Acid.

If the former then a car type charger is ok.  If the second only a dedicated SLA charger should be used because the batteries will then be charged at a constant rate and not subject to pulsing caused by variations in AC voltage supplies.

This is what I was taught having fried SLA's in the past by using the wet acid type charger.

It would be interesting to know what others think......

[catengineman]

I have 2 chargers bot can be switched between 12v and 6v
1 is an old halfords (yes really old)
2 is a new plug in the socket type (instructions say SLA is OK)
now I may or may not have been lucky but I have charged my batts from the No 1 charger and also from the No2 charger and never noticed any difference.
If I do all my TN batts at the same time I use the No1

This is where I find out I have been doing it wrong         [but its worked for me syndrome ]

R,

[dougal99]

Using a car battery charger can fry SLA batteries as the amperage they put out is usually too great. Dad managed to totally wreck some expensive SLA's for Mum's invalid scooter expensive lesson £100+

HTH

Doug

[Stuart]

The batteries are of the sealed lead acid variety and I have now joined them in series and they appear to be charging ok. They had 6 volts from new and when l went on the water. I have basically let them go totally flat through use on the water so they are now 4.5 volts. They have been charging for 14 hours now, and l am waiting for the auto charger to let me know when they are fully charged.

[Shipmate60]

For these batteries they should take 9 hrs to charge, but wont do any more harm leaving them longer.
1 thing to check even if they show 12 volts is to put on a load to see if the capacity has reduced.

Bob

[Bartapuss]

is this the first charge they've had since purchase??

[Stuart]

It is the first time that I have charged these batteries. As they were taking longer than l was expecting l switched off the auto charged and measured the voltage. One was reading 6.5 volts and the other 6.3 v. I stopped charging after this fearing that the batteries may get damaged if they are not already. I was disappointed that the auto charger did not switch off as it should have, there again it was not expensive and you get what you pay for l suppose!

[Bartapuss]

Could be as they've been left so long and become so discharged they may be damaged, after say 5 days check the voltage again to see if it drops below 6v if they do then there had it, if not run them down in your boat and note what sort of run time/performance you get and then if possible charge each one individualy, thats if you've got a 6 volt charger and recheck the voltage after charging, see if there's any improvement.