East Midlands Berlingo project

[Flying John]

Sorry but that is simply not true. If you read the tech spec of the STM range and the SAFT ULM range for aircraft use the construction of the cells is the same.

The seperator failures in early STM 100's is well documented and was a recognised early failure mode of these batterys.

The statement "the Maint charge is designed to get the cells hot", is absolutely untrue and false and SAFT warn many times in their technical manual for these batterys that heat will destroy the cells. This is why there is such an elaborate cooling system in place.

The watering within 30 mins is nothing to do with heat , but is the point at which the maximum amount of liquid electrolyte is expressed by the plates of the battery. A fully discharged SAFT STM 100 will be dry with no free liquid in the cell. The plates are not covered in the same way a lead acid battery plates are covered

These SAFT aircraft starter and aux batterys ARE designed for very high discharge rates for starting applications and continuos (not so high) constant loads (100Amps+). and in fact may exceed the max discharge currents that are allowed in the STM range (in excess of 500Amps for 10 second bursts) and the cell plate construction is virtually identical and it is only the encapsulation of the sintered plates that is different.

You say that "..... and hopefully balanced out the cells and the plates having fully absorbed the max electrolyte."

This is the complete opposite of what happens the electrolyte is ONLY absorbed at max discharge - not charge. The electrolyte is NOT absorbed at max charge. The opposite is true, there is most free liquid at maximum state of charge.

I agree that the STM's are not designed to be "Reconditioned" , although in the early days of these cells SAFT did offer a reconditiong service, which they later withdrew at about the same time as they withdrew the offer of new batterys for sale.

Having said all that, anything is worth a try for a known apparently dud battery, hence the reason for my removing the electrolyte and rinsing, as this could dislodge a high resistance growth or particle on a plate that is reducing the capacity of an individual cell after this the reccomended method (by SAFT) for trying to regain capacity for a failing battery set is to charge at 10Amps for 15 hours, constant current, no end point voltage.

Dont forget it is not in the makers interest to refurbish or try and fix a dud, they would rather you bought a new one, that is back in the day when they would actually sell one to you.

If you do need more electrolyte then the concentration is 400grams/litre KOH.

So just to recap - the plates are not covered in electrolyte in the discharged state. By charging gently at very low currents, as i suggested in earlier post , you will not generate enough heat to bend the plate. If the cell is dry , it will not charge (nothing to carry the Ions). As you charge more liquid is expressed therefore more of the plate is covered. If a cell wont take any charge then a small amount of water could be added to kick start the charge process.

John