Leisure battery - how fast does voltage recover?

[Burnham_Bob]

I have a 90 amp hour Leisure Battery I inherited with the boat. It has never had the oomph to turn over the engine ( a 2 cylinder 13 hp beta) but as i have another starter battery that's no problem. But should it turn over the engine? - or is it past its sell by date? I have a dsc radio that tells me when the 12 v battery is low. The leisure battery hadn't been charged for over a month a week or so back and it read low but after an hour or so of engine running it seemed fine. Today that battery read just under 12 volts on meter, but after three hours charging at home, the charger says its full and its reading 12.6. On an earlier post i read that these batteries recover faster. I did find that the cells needed topping up with water when I charged - its the first time I've taken it off the boat. Advice please.

 

[Steve Clayton]

Your battery is in a similar state to the parrot in the Monty Python sketch

A "full" battery will read 13 to 13.2 volts and it should have no problem in turning your engine over

 

[VicS]

Charge it at home. If you have bog standard, non automatic, charger with no bells or whistles that can deliver say 4 to 6 amps charge it until the volts have risen to 14.4 or thereabouts and maintain it at that for say an hour. Then let it rest for say 12 hours and take a reading with a digital voltmeter. If you have got 12.7 to 12.8 ish volts you've got it fully charged to all intents and purposes. If not try charging for a bit longer.

If you have a fancy machine with all the bells and whistles then I guess you charge until that says its charged and rings the appropriate bell. (Dunno my charger predates everything but the lead acid battery itself.)

12.2 would be about half charged and around 11.7 effectively flat.

Assuming you've successfully charged it let it stand and monitor the volts over several days and weeks if possible.

The volts will fall quite quickly at first but if its good it'll still show 12.7 a week later and 12.6 several weeks later.

Its not the final answer. having it tested professionally is that but it will tell you whether it will charge fully and whether it will retain its charge.

 

[William_H]

A 90 AH battery is pretty big by any standard and so should IMHO easily start the engine. Engine start batteries are designed for high starting capability for their size. Leisure batteries are made for deep cycle but a big leisure battery should still provide enough start current. On that basis because you need it as a standby engine start battery chuck it out.
You might want to ensure it is fully charged. To my mind the best way to do that is to know you have put in at least an equivalent to the AH rating. So 4.5 amps fopr 20 hours it must be charged. Not so eas however on these fancy auto chargers. If it still won't start the engine it is no good to you.
You will probably find that if you do a discharge test say with a car headlight it will go very dim after a short while. Proving again it is dead. A 50 watt auto bulb should stay bright for at least 12 hours.

Ave a noo 1 Olewill

 

[VicMallows]

I think both VicS and I (not to forget Nigel Luther who seems to have vanished into Latvia) are 'experts' at salvaging batteries others have discarded /forums/images/graemlins/grin.gif

You really need to provide an open-circuit-voltage in the region of 18v, and then current-limit it to typically 3 or 4 amps; then charge for around 36 hrs and float charge for as long as you like. So-called intelligent chargers just don't do this.

I use a home-brew brute-force charger, with a hefty rheostat that originated in wars before I was born.

Vic

 

[VicS]

[ QUOTE ]
I think both VicS and I (not to forget Nigel Luther who seems to have vanished into Latvia) are 'experts' at salvaging batteries others have discarded

[/ QUOTE ] Good heavens not me.

 

[gandy]

[ QUOTE ]
A 90 AH battery is pretty big by any standard and so should IMHO easily start the engine. Engine start batteries are designed for high starting capability for their size. Leisure batteries are made for deep cycle but a big leisure battery should still provide enough start current.

[/ QUOTE ]
Our experience suggests the same. We used an 85AH Leisure battery as the main engine start battery for several years. That was starting a Volvo MD7A and I imagine that would need at least as much power as a 13HP Beta.