On Thu, 1 Feb 2018 23:31:45 +0000, (Roger Hayter)
wrote:

Harry Bloomfield wrote:

submitted this idea :
I'm puzzled by your comments. What sort of lead acid charger is not voltage
regulated?

I didn't actually mention it not being voltage controlled. I had in
mind it might have been a very basic simple charger, using basic
voltage sensing to switch a relay when a set voltage was reached across
the battery. I have one such in my workshop, which charges an emergency
starter battery/ min compressor type thing. You plug it into the mains,
it charges until the battery reaches a set voltage then switches the
charge circuit off. It then remains off/ not charging until the next
time the mains supply is cycled. It is rather a neat way to do it and
proving the mains supply is cycled very occasionally, such a battery
will be kept in good condition for decades, with little electrolyte
evaporation.

I think that would only work for trickle charging. If you want to
charge at a decent rate then the battery has to be charged at a somewhat
higher voltage, overlapping what would be the fully charged voltage.

It's interesting, not something that I have come across.

Not sure exactly how it would be done, probably using the terminal
voltage after a small load resistance and then using a timer to ensure
that charging was maintained for a significant period.

The terminal Volts alone couldn't be used as 12V batteries seem to be
happiest being charged at 13.8V, settling to 12.6- 12.7 V on removal
of the charger.

Although it,s a fair while since I played with batteries, I seem to
recollect that 13.8V was the voltage measured at almost every state of
the recharging process.

'Couldn't find anything via Google, one or two curves but really the
charge Voltage is to a great extent dependent on the source resistance
of the charger.

AB