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I remember at around 10 year old rebuilding a radio, and using a lead acid gel cell I found in the loft, it must have been second world war surplus bought by my dad, and it worked fine early 60's, but also seen 6 month old batteries fail on taxi's.
In the late 60's early 70's I was into auto electrics, and attended collage to learn more, we were give what seemed a simply home work, "why does the voltage reduce as a lead acid battery?" at that time no internet, only collage library, and I could not find a definitive answer to the question.
Loads on Daniell cell and Leclanché cell, but lead acid was missing, I had to assume the action was some thing similar, and wrote my essay, for which I got 9½ out of 10, but the lecturer never said what mistakes I had made, and still today not really sure why the voltage falls, I would have expected it to be like the Daniell cell and maintain the voltage until completely discharged, and in 1980 working in Algeria I found the batteries from USA with built in hydrometer did seem to both retain voltage much better than the non sealed lead acid I had used up to that date, construction methods clearly had a bearing on volt drop.
But as to battery care, although the traction battery did not shed it's active material, it still died, but the half way between traction and vehicle battery called the leisure battery, also showed how construction methods varied, and replacing a 60 Ah vehicle battery with a 90 Ah leisure battery and yes it did last longer, however when I was short of lead to repair battery posts and I broke open some batteries to get the lead, only to find lumps of what looked like polystyrene and realising the battery could have been made 2/3rds of the size, and the large 110 Ah battery would fit in a 90 Ah battery case, it was clear you did not always get what you thought you were getting.
The small VRLA (valve regulated lead acid) seemed a great idea with small 2 to 12 Ah batteries, the valve was in real terms a rubber cap, but in alarms, stair lifts, and emergency lights these batteries became common, however in my mothers stair lift the batteries seem short lived, but lasted a lot longer in father-in-laws, and on looking it seems 30 plus volts was rather high, and I realised the designers assumed the lift would be used at least 4 times a day, and if it was used, the batteries lasted, but if only used once a week, batteries were over charged.
We know the traction batteries in a narrow boat should last around 10 years, but also in real terms they only last 2 years, so the big question was why, 4 x 180 Ah batteries are not cheap. And what the hydrometer showed was with 6 hours cruising per day, the two massive 70 amp alternators even with an inverter which combined the outputs using a pulse charging system, the batteries were never fully charged as the boat moored up, call at the Pub once a fortnight and plug into shore supply, and the batteries would last. In the 30 hours they could fully recharge (6+18+6) but the power used over night was otherwise never fully replaced in the 6 hours.
And this seems to be the whole problem with lead acid, the time they take to charge, one can replace 90% reasonably fast, but the last 10% takes ages. And the longer the battery is left discharged the longer it takes to recharge, so use a starter then drive off there are seconds when battery discharged, but leave the boot open so interior light discharges the battery, and it can take weeks for the alternator to replace that power, as the battery is not charged for long enough.
The stage charger shows this, with 5 stages 3.8A, 3A, 0.8A, 0.1A and zero, we see a 90 Ah battery half discharged drop out of 3.8A rate in maybe 2 hours if not less, the 3A rate a further 6 hours so 8 hours in all, the 0.8 amp rate 2 days, and the 0.1 amp rate 2 weeks before it drops to zero. (Assuming not connected to car)
Likely well before 2 weeks are up we have taken the battery off charge, but on the car each time we drive a little more is returned, until the pandemic where cars have stood without use for months at a time, in general it takes ½ the time to recharge as to discharge, so sitting for a month working intruder alarm and it takes 14 days to replace that power with a 13.4 volt supply, raise the voltage to 13.8 then will take less time, but at 14.8 volt you start to look at drying out the cells, so may be able to shorten it to a week using a stage charger, but most people are removing charger next day.
So net result battery never gets fully recharged, and bit by bit it gets more and more sulphur building up in it, so the Ah capacity slowly reduces.
Clearly at some point batteries do fail, but although with a traction battery the active material can't fall off, and so an equalising charge and a top up with pure water allows faster charging, this option is not open to us with an AGM battery, so it simply takes time.
In the late 60's early 70's I was into auto electrics, and attended collage to learn more, we were give what seemed a simply home work, "why does the voltage reduce as a lead acid battery?" at that time no internet, only collage library, and I could not find a definitive answer to the question.
Loads on Daniell cell and Leclanché cell, but lead acid was missing, I had to assume the action was some thing similar, and wrote my essay, for which I got 9½ out of 10, but the lecturer never said what mistakes I had made, and still today not really sure why the voltage falls, I would have expected it to be like the Daniell cell and maintain the voltage until completely discharged, and in 1980 working in Algeria I found the batteries from USA with built in hydrometer did seem to both retain voltage much better than the non sealed lead acid I had used up to that date, construction methods clearly had a bearing on volt drop.
But as to battery care, although the traction battery did not shed it's active material, it still died, but the half way between traction and vehicle battery called the leisure battery, also showed how construction methods varied, and replacing a 60 Ah vehicle battery with a 90 Ah leisure battery and yes it did last longer, however when I was short of lead to repair battery posts and I broke open some batteries to get the lead, only to find lumps of what looked like polystyrene and realising the battery could have been made 2/3rds of the size, and the large 110 Ah battery would fit in a 90 Ah battery case, it was clear you did not always get what you thought you were getting.
The small VRLA (valve regulated lead acid) seemed a great idea with small 2 to 12 Ah batteries, the valve was in real terms a rubber cap, but in alarms, stair lifts, and emergency lights these batteries became common, however in my mothers stair lift the batteries seem short lived, but lasted a lot longer in father-in-laws, and on looking it seems 30 plus volts was rather high, and I realised the designers assumed the lift would be used at least 4 times a day, and if it was used, the batteries lasted, but if only used once a week, batteries were over charged.
We know the traction batteries in a narrow boat should last around 10 years, but also in real terms they only last 2 years, so the big question was why, 4 x 180 Ah batteries are not cheap. And what the hydrometer showed was with 6 hours cruising per day, the two massive 70 amp alternators even with an inverter which combined the outputs using a pulse charging system, the batteries were never fully charged as the boat moored up, call at the Pub once a fortnight and plug into shore supply, and the batteries would last. In the 30 hours they could fully recharge (6+18+6) but the power used over night was otherwise never fully replaced in the 6 hours.
And this seems to be the whole problem with lead acid, the time they take to charge, one can replace 90% reasonably fast, but the last 10% takes ages. And the longer the battery is left discharged the longer it takes to recharge, so use a starter then drive off there are seconds when battery discharged, but leave the boot open so interior light discharges the battery, and it can take weeks for the alternator to replace that power, as the battery is not charged for long enough.
The stage charger shows this, with 5 stages 3.8A, 3A, 0.8A, 0.1A and zero, we see a 90 Ah battery half discharged drop out of 3.8A rate in maybe 2 hours if not less, the 3A rate a further 6 hours so 8 hours in all, the 0.8 amp rate 2 days, and the 0.1 amp rate 2 weeks before it drops to zero. (Assuming not connected to car)
Likely well before 2 weeks are up we have taken the battery off charge, but on the car each time we drive a little more is returned, until the pandemic where cars have stood without use for months at a time, in general it takes ½ the time to recharge as to discharge, so sitting for a month working intruder alarm and it takes 14 days to replace that power with a 13.4 volt supply, raise the voltage to 13.8 then will take less time, but at 14.8 volt you start to look at drying out the cells, so may be able to shorten it to a week using a stage charger, but most people are removing charger next day.
So net result battery never gets fully recharged, and bit by bit it gets more and more sulphur building up in it, so the Ah capacity slowly reduces.
Clearly at some point batteries do fail, but although with a traction battery the active material can't fall off, and so an equalising charge and a top up with pure water allows faster charging, this option is not open to us with an AGM battery, so it simply takes time.
