Batteries

[mick]

I bought two new Lucas LX24MF 86ah leisure batteries a year ago, to serve as my service bank. They have had a fair amount of use as we practically live aboard 5 months of the year. I've charged them regularly over the winter. Two days after their last charge one reads 12.8 and the other 12.6v. Why the discrepancy?

 

[sarabande]

were they conjoined series or parallel when in use, or used as single entities ?

 

[mick]

were they conjoined series or parallel when in use, or used as single entities ?

Linked as one bank of two.

 

[Plevier]

Are they topped up to the same level?
More water = lower specific gravity = lower open circuit voltage.
V per cell = s.g. + 0.85 at 25 deg C.

 

[neil_s]

You have a poor connection to one of them, maybe?

Neil

 

[VicS]

Charge the one reading 12.6 some more.
See if you can get it to the same reading as the other.

If you charged them together in situ do as Neil suggests; check the connections

Troubadour asks if they are both topped up to the same level but they are sealed aren't they?

 

[Plevier]

Charge the one reading 12.6 some more.
See if you can get it to the same reading as the other.


asks if they are both topped up to the same level but they are sealed aren't they?

Sorry didn't realise that. Suppose MF in type number is the clue

However they aren't AGM, they are just "sealed maintenance free" (i.e. wet without accessible vents) and if used with a multi rate charger are likely to have gassed some off.
Agree with charging the lower one some more, but 12.8V - if that's after an hour or two off charge, not as soon as you turn the charger off - implies s.g. higher than 1.280 - that's high.
I would see if you can remove the vent cover and check if the electrolyte level is low on the high voltage one. Often it's just under a sticky label.

 

[stevensuf]

was the one with the higher charge the one closest to the charge source? sometimes the battery further away gets less charge to resistance of the terminals, one extra jump so to speak to the next battery, also the one closest to the terminals will usually supply a slightly greater share of any power used, again its resistance to any load is lower.

 

[VicS]

was the one with the higher charge the one closest to the charge source? sometimes the battery further away gets less charge to resistance of the terminals, one extra jump so to speak to the next battery, also the one closest to the terminals will usually supply a slightly greater share of any power used, again its resistance to any load is lower.

They should be connected so that does not happen.
Positive connection on one battery, negative connection on the other.

Details in the technical info pages on the Smartguage website

 

[SlimRick]

They should be connected so that does not happen.
Positive connection on one battery, negative connection on the other.

Details in the technical info pages on the Smartguage website

24v?

 

[VicS]

24v?

No connecting to batteries in parallel .

Dont connect the positive and negative leads to the same one ... one to each

Oh heck, heres the link to the item on the smartgauge website

http://www.smartgauge.co.uk/batt_con.html

 

[Gypsy]

Were they disconnected when you measured them - that is were they standing "free" of each other?

 

[mick]

Were they disconnected when you measured them - that is were they standing "free" of each other?[/QUOT

Each charged independently, off the boat. Thanks for all replies. I'll try some suggestions.