Battery charging

[tsmyth]

I have a 65Ah wet cell 12 v marine battery.

I have just charged overnight it using one of those golf cart chargers. The LED on the charger shows fully charged. Using a battery tester the LED shows fully charged, and a volmeter shows 13.03 v.

However, a hydrometer shows red (1.15) for each cell.

Is this because the more dense electrolyte has settled to the bottom of the cells?

Ray

 

[William_H]

Hi Ray I don't believe you can put too mu8ch trust in the LED on the charger telling you bwhen the battery is charged and for that matter the SG of the acid is not much help either unless you knew the SG before you started.
I suggest you get a multimeter if you don't already have one with a 10 amp current range. Observe the current from the charger at various stages and this will give you an idea of the percentage of charge that has gone in and the total if you stated with it discharged. I think an over charge of 50 or 100 percent is good occasionally provided it is not at a high current. You might find that your charger charges at quite a low rate so will need a long time on charge. just a few thoughts olewill

 

[Anonymous]

As will says, it's a good idea to check the current but in any case 13.03V is not high enough, charging is not complete. What sort of golf cart charger - some are for NiCds, some for gel,...you need to know what sort of battery and whether 6V or 12V. You really need to get the volts above 14V for a while to complete the charge. Modern chargers then fall back to a float level of around 13.1 to 13.6V though not everyone agrees on the exact range. 13.03 does sound far too low.

If you are just trying to put some charge into it for the start of the season, you could connect it across your car battery with jump leads, with the engine running, for half an hour.

 

[halcyon]

!3.03 volt you are stating, if this is the on charge voltage, this equates to a flat battery on charge, and thus agrees with your sg reading. The sg reading is the norm for cheaking charge level, the voltage method is based on an approximate relationship between sg and volts, but is not totally accurate. You need to charge to 14.6 volt for a normal lead acid, above this voltage you get bad gassing, and not a lot of gain in recharge. The float charge of 13.6 volt does nothing but provides a power supply to the boat, and stop self discharge of the battery. Back in 1983 when we started making dual voltage chargers ( there not that modern Lemain ), we did a lot of testing, and one thing we found was running at 13.6 volt for extended periods reduced battery life. This voltage 13.6 volt, came from the maintainance charge for reserve power batteries you found in telephone exchages etc, and they needed a periodic boost charge to high voltage.

Brian

 

[Anonymous]

[ QUOTE ]
The float charge of 13.6 volt does nothing but provides a power supply to the boat, and stop self discharge of the battery. Back in 1983 when we started making dual voltage chargers ( there not that modern Lemain ), we did a lot of testing, and one thing we found was running at 13.6 volt for extended periods reduced battery life.

[/ QUOTE ]Brian, Could you amplify that at all? How significant is the problem and was the testing across a wide range of types, sealed, gel, AGM or flooded? What do you mean by 'extended'? As a liveaboard, during the winter we are on float charge all the time, and ours is set to 13.2V. Is that likely to cause premature ageing of flooded lead acids? Is there a way round it? When our shore power trips out (it does, every week or so) the Mastervolt goes into equalisation mode of around 14.4V for 4 hours. Does that help? David

 

[halcyon]

David, back in 83 we had lead acid, and basically that was it for boats. It was running for like six months, at the time we put it down to stratophication (?) active material settling out into bottom of battery. By raising the voltage and gassing the battery it had a stiring action, and removed the poblem. I do not give a warrenty on this gen, but at the time it worked. So by recycling the charger to 14.4 volt you are ding the above, and at the worst you are loosing nothing.
A few years later we had sealed batteries in AC Delco Freedom, these a lot of problem with Westerly that was using them, with regard to charging. We found out that they required ( at the time ) a higher charge voltage, somewhere near 15.5 volt from memory. If not you got the straophication (?) problem and lost a lot of capacity, to this end we made Westerly a special charger that charged to 15.4 volt and floated at 14 .5 volt ( or there abouts). We advised at the time not to discharge below 50%, and bench charge at the end of the season, before storage over winter.
With regard to all the batteries available to-day, they have come along since we stopped making chargers, but reading all the bits on the forum on batteries and charger's, I am going to have a look at charging them over the summer. May dig out the alternator regulator agian and do some tests, then I can have fun with the tax man on how much sailing is work useage testing new products!!!!

 

[Stoaty]

This is a subject where ten people would give ten similar answers, but none of them exactly the same. So this is what works for me in my set up. If I had a volt reading of 13.03 volts I would consider this battery as either discharged but not desperately so or sulphated up. Sulphation is where tiny particles of sulphate get into the plates and cause the battery to become inefficient. I would find that I could still start my engine if my battery voltage was 13.03 volts, however, I would be concerned if the voltage was below 13.6 volts after running the engine for an hour or after charging. It's proper to say here that I check the voltage after the battery has been idle for a while. For a full charge I charge at 14.5 volts, on a float charge I charge at 13.8 volts. I find that 14.5 volts fully charges the battery with some gassing and a 13.8 volts float gives me minimal gassing and around an 80% charge. I find that long periods of charging at 13.8 volts causes sulphation of the plates. I counteract this by making sure that my battery gets fully charged. I consider 13.6-13.8V after standing fully charged. Then I charge the fully charged battery at 14.5 volts at an amperage of one twentieth of the Amp Hour capacity of the battery, for 6-8 hours. As an example I would give a 14.5v 5Amp charge to a 100 AH battery. This will cause the battery to gas and fluid will have to be topped up. However it will remove some or all of the sulphation. I do this about every 2 months. I find my batteries last about 5-7 years and I am happy about that.

I gave up using an hydrometer as I found that unless you bought a very expensive calibrated one, then the readings were inaccurate. I also felt that somehow dipping the hydrometer into the battery was causing contamination and that led to sulphation. The final straw was treading on my nice expensive hydrometer.

Heres a couple of links that might help.

http://www.roadpro.co.uk/techTips01.asp?TechTipID=23

http://www.cyb.com.au/industrial/Motive_PS/Technical_Advice/Charging/default.htm

http://www.hoppecke.com/upload/docs/stan...ising%20charge'

 

[Anonymous]

[ QUOTE ]
I gave up using an hydrometer as I found that unless you bought a very expensive calibrated one, then the readings were inaccurate. I also felt that somehow dipping the hydrometer into the battery was causing contamination and that led to sulphation.

[/ QUOTE ]I agree - plus the fact that you've got a hydrometer dripping with H2SO4 to take over your batteries and terminals until you can make it safe is a wet cloth, water or whatever. Sulphuric, even at battery strength, is evil stuff and best left in the cells. Besides, it's totally unnecessary, one can manage perfectly well with a combination of accurate voltage and current measurements.

 

[Anonymous]

Thanks for all that. I have nice new Varta semi-traction flooded lead acids and I don't want to degrade them. I have three means of charging - direct from the Yanmar engine, via an 80A Mastervolt (fed by shore power of our generator) and 360W of solar panels controlled by a Morningstar Prostar controller. I am still waiting to get the solar system up and running but I think that it will be floating the batteries at about 14.4V which sounds high - but only when the sun shines so maybe that's OK.

 

[tsmyth]

Thanks chaps.

The chareger is a Boska. It is designed for batteries of 17 - 30 Ah cpacity but the local battery man said I could use it - perhaps he was wrong. I have just conected another charger I have. It is charging at 14.7 v, so I will keep an eye on it for a while.

Ray

 

[Anonymous]

Sounds to me as though the charger is designed to provide a fixed current for a fixed time which is quite common with NiCds, especially when they are always recharged from nearly flat. I suspect that it isn't suitable for lead acid. What else can you tell us about the other charger that is charging at 14.7V?