What voltage to allow batteries to go down to?

Fergus

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Just wondering - on a long passge how low should you go before recharging with the engine? Safe to go below 12.2V when under load from nav lights etc?
 
When in use, the readout on my 2 service (deep cycle) batteries is depressed - not surprising. So, without load, when they approach 12v I take flight and top them up.
Seems to work. But reloading them and also running systems simultaneously does take time, more then one would hope!

PWG
 
Just wondering - on a long passge how low should you go before recharging with the engine? Safe to go below 12.2V when under load from nav lights etc?

As a rule of thumb, 11.85 volt under load, around 5% of battery capacity, will be about 50% discharged. so 11,85 - 12.0 should be a recharge point.

I have used this value on the display section of the VSR systems we have made for the last 30 years, and it's always worked resonably well.

But realy start there, and tune it to your needs.

Brian
 
battery charge

Any battery on a yacht/boat that falls below 10.8v is to dead. A deep cycle battery in reasonable condition can be allowed to fall as low as 11v whilst under use and then you must charge. We never allow our batteries to fall below 12v whilst under load. The choice is yours.
 
they nusually reckon on no more than 50% discharge on the sort of "leisure" batteries most of us use and that translates to 12.2v
50% is 12.2 volts on a rested battery. That is one which has not been on load or on charge for say 12 hours. In service the volts will be lower and depend on the load.

The life of a battery is related to the depth of discharge AND the number of cycles. For bog-standard and "leisure" batteries the number of cycles to 50% can be pretty low but for good genuine deep cycle and traction batteries can be quite high. Some battery manufacturers give some good info on their websites .
 
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