Equalisation charge

[tobble]

how to do this?

I want to apply an equalisation charge to my batteries, two 110 ish Ah wet lead acid, Rolls brand. they are about a year old, and have been discharged a bit too low on two or three occasions - low enough to notice tungsten bulbs are slightly dimmed (I didn't measure the voltage, silly me). There is a bit of discrepancy between the SG readings, last time I checked it was a range of two or three 1/100ths

a) How best to achive the desired voltage - I have a sterling alternator controler type charger, thought I could temporarily add a diode between the voltage sensing wire and the battery +ve, so the controller boosts the voltage by 1.2 V - If I recall correctly this would mean it would give 14.8V plus the 1.2 so 16V. If this isn't appropriate, any other ideas that don't involve serious outlay?

b) How long should an equalisation charge last for this size bank?

c) are there any other tips on the proceedure? I'm guessing it'd be best to make sure the batteries are fully charged first? presumeably make sure they are topped up so the off-gassing doesn't present serious issues... don't lick the teminals... anyhting else?!

cheers in advance...

 

[Gumpy]

A: could be a problem with this as the sterling has a cut off at 15.5v not sure where the reference point in the circuit is.

B: It should be as long as it takes until the specific gravity of all the cells are equal.
This means that you should monitor it every so often by taking SG readings.
Can take up to 8 hours, in practice when I do mine I just switch the charger into equalisation and leave it until it times out (8 Hours)

c: make sure that they are fully charged and that there is plenty of ventilation as there will be a fair amount of gas produced.

 

[saltwater_gypsy]

The equalization charge should be about 5%of the battery cpacity and applied for a period of 3-4hours until a voltage of 16V is reached. This should only be done periodically.

Re: John Payne's Electrical Bible

 

[tobble]

thanks for the replies chaps.

saltwater, I'm a bit confused by your comment on the 5% of battery capacity. clearly this is 11Ah of my 220 ish Ah bank, are you saying that over 3 hours I should be looking to average just under 4 Amps? how is this achieved in practice where my only real control is over the voltage applied?

I'll try to find a copy of John Payne, thanks for the reference. might give sterling a shout too to find out thier view...

cheers again

 

[Gumpy]

Yes the charge should be current limited, my 65amp charger does the equalisation charge at 10 amps IIRC.
If you just up the voltage then the charge rate goes up as well.

 

[tobble]

Hello again, just had the folowing reply from Charles Sterling:

For safety reasons we only allow the voltages to rise to a certain level before we switch the unit off, f you want a high voltage blast then remove the red wire ( so there is no battery sence ) and remove the brown wire from the d+ ( which kills the safety wire , the the alt will go up to about 17 volts. Do not go to the pub and leave it there make sure you batteries do not get to hot

hope that might help someone else. Just to clarify, the regulator is the Sterling DAC12

 

[tobble]

Just to report back that I sucsessfully got about 15.5 to 16V from the alternator with the regulator wired as suggested. Happy days!