Plevier
Well-Known Member
A bit of battery history may help here. Bear with me, it does end up relevant!
Lead acid batteries used to be made with an alloy of lead (Pb) and typically 8-10% antimony (Sb).
The high Sb content lowers the gassing voltage which is why charging voltages used to be low and water consumption high. It also increases the self discharge rate.
Efforts to improve performance and reduce use of nasty toxic Sb went two ways.
In Europe, improved casting techniques and other additives got Sb content down to typically 1.8% in my days in the industry and I believe typically 1.5% now.
In USA, they came up with an alloy using around 0.1% calcium (Ca) (plus other minor additives) instead of Sb.
(Because of the history, batteries of PbSb alloy tend to be known just as lead acid, while ones of PbCa alloy tend to be known as lead calcium, making people think they are fundamentally different from lead acid but in fact they are just a minor variation.)
Compared with traditional high Sb, Pb with low Sb will take higher charging voltage, gas less and self discharge more slowly. However it won't have such a good cycle life.
Pb Ca will take even higher voltages, gas even less and self discharge even more slowly. However it's even worse than low Sb for cycle life and high temperature tolerance. (Some advertising claims in this area are blatantly untrue!) Ca is much less toxic than Sb and easier to handle environmentally, a good reason for manufacturers to prefer it. PbCa alloy is however harder to cast than PbSb.
Treated sensibly (without too much fast charging) a PbCa battery will get through its whole life without needing topping up if it has a decent reserve volume. The marketing people got hold of this and invented the "sealed for life maintenance free" battery. The low Sb producers copied them. I stress there is really no difference technically in the "sealed for life" other than the deletion or hiding of the refill plugs; it's a marketing invention. These batteries dominate the market now.
However for serious cycling applications, Sb content of 5% or more offers much better durability and a few manufacturers inc Trojan still produce them (not all Trojans mind you.) These batteries will gas more, particularly if charged vigorously, and self discharge quicker.
Another problem with Sb at this level is that through the life of the battery it migrates from the +ve plates to the -ve plates and deposits in spots which then gas much more freely.
So finally getting to the point, if the water consumption of your Trojans has increased a lot, yes it's an indicator they are probably approaching end of reliable life. The increased gassing isn't harmful per se - just a nuisance - but it does mean other damaging things have been going on. You won't see the same increase happening with low Sb or Ca.
As regards testing, only a discharge test at a realistic rate will give you a reliable idea of their remaining capacity. A garage tester will not.
PS Above remarks relate to flooded only, not gel or AGM, that would be another essay! Gel has no place on a boat in my view, some AGMs are very good, many are rubbish.
Lead acid batteries used to be made with an alloy of lead (Pb) and typically 8-10% antimony (Sb).
The high Sb content lowers the gassing voltage which is why charging voltages used to be low and water consumption high. It also increases the self discharge rate.
Efforts to improve performance and reduce use of nasty toxic Sb went two ways.
In Europe, improved casting techniques and other additives got Sb content down to typically 1.8% in my days in the industry and I believe typically 1.5% now.
In USA, they came up with an alloy using around 0.1% calcium (Ca) (plus other minor additives) instead of Sb.
(Because of the history, batteries of PbSb alloy tend to be known just as lead acid, while ones of PbCa alloy tend to be known as lead calcium, making people think they are fundamentally different from lead acid but in fact they are just a minor variation.)
Compared with traditional high Sb, Pb with low Sb will take higher charging voltage, gas less and self discharge more slowly. However it won't have such a good cycle life.
Pb Ca will take even higher voltages, gas even less and self discharge even more slowly. However it's even worse than low Sb for cycle life and high temperature tolerance. (Some advertising claims in this area are blatantly untrue!) Ca is much less toxic than Sb and easier to handle environmentally, a good reason for manufacturers to prefer it. PbCa alloy is however harder to cast than PbSb.
Treated sensibly (without too much fast charging) a PbCa battery will get through its whole life without needing topping up if it has a decent reserve volume. The marketing people got hold of this and invented the "sealed for life maintenance free" battery. The low Sb producers copied them. I stress there is really no difference technically in the "sealed for life" other than the deletion or hiding of the refill plugs; it's a marketing invention. These batteries dominate the market now.
However for serious cycling applications, Sb content of 5% or more offers much better durability and a few manufacturers inc Trojan still produce them (not all Trojans mind you.) These batteries will gas more, particularly if charged vigorously, and self discharge quicker.
Another problem with Sb at this level is that through the life of the battery it migrates from the +ve plates to the -ve plates and deposits in spots which then gas much more freely.
So finally getting to the point, if the water consumption of your Trojans has increased a lot, yes it's an indicator they are probably approaching end of reliable life. The increased gassing isn't harmful per se - just a nuisance - but it does mean other damaging things have been going on. You won't see the same increase happening with low Sb or Ca.
As regards testing, only a discharge test at a realistic rate will give you a reliable idea of their remaining capacity. A garage tester will not.
PS Above remarks relate to flooded only, not gel or AGM, that would be another essay! Gel has no place on a boat in my view, some AGMs are very good, many are rubbish.
Last edited:
