Battery Life

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TonyS

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My OE Bosh wet, lead acid batteries, 2 x 140 Ah, 1 x 60 Ah, have nearly completed their 10th season. Boat new in Jan 2003.
I have a BM1 monitor and during the sail today from Port Haliguen to Groix, (4hrs) with the plotter and fridge together (10 Amps) the voltage drops to 12.4V. When the fridge cuts out it returns to 12.6 V.
It takes a 23 Amp charger about 3 hrs to restore 100% capacity on the BM1.
I have never seen the voltage below 12.4 in the life of the batteries. I have a 40 W solar panel.
When should I replace the batteries?
 
TonyS said:
My OE Bosh wet, lead acid batteries, 2 x 140 Ah, 1 x 60 Ah, have nearly completed their 10th season. Boat new in Jan 2003.
I have a BM1 monitor and during the sail today from Port Haliguen to Groix, (4hrs) with the plotter and fridge together (10 Amps) the voltage drops to 12.4V. When the fridge cuts out it returns to 12.6 V.
It takes a 23 Amp charger about 3 hrs to restore 100% capacity on the BM1.
I have never seen the voltage below 12.4 in the life of the batteries. I have a 40 W solar panel.
When should I replace the batteries?
Click to expand...

Obviously 2 years ago!!
 
TonyS said:
My OE Bosh wet, lead acid batteries, 2 x 140 Ah, 1 x 60 Ah, have nearly completed their 10th season. Boat new in Jan 2003.
I have a BM1 monitor and during the sail today from Port Haliguen to Groix, (4hrs) with the plotter and fridge together (10 Amps) the voltage drops to 12.4V. When the fridge cuts out it returns to 12.6 V.
It takes a 23 Amp charger about 3 hrs to restore 100% capacity on the BM1.
I have never seen the voltage below 12.4 in the life of the batteries. I have a 40 W solar panel.
When should I replace the batteries?
Click to expand...

When you cannot recharge them or when they don't retain their charge for long enough to serve your needs.

Preferably before being unable to start the engine on the starter battery alone. Presumably the 60 AH one is a separate and dedicated starter battery.

If they are 10 years old they dont owe you anything!
 
VicS said:
When you cannot recharge them or when they don't retain their charge for long enough to serve your needs.

Preferably before being unable to start the engine on the starter battery alone. Presumably the 60 AH one is a separate and dedicated starter battery.

If they are 10 years old they dont owe you anything!
Click to expand...

Hi,
I agree that they don't owe me anything. Many on this forum replace at intervals like 3 years. I don't want to come to France next year, which takes us about 10 weeks, and have them fail. New here will cost €500.
Are there any signs that they are in their last season?
The lowest voltage last year was 12.5 but this year we have only anchored twice because the weather has been so poor.

I have the 10 year old Pathfinder RL 70C colour plotter with radar (on standby) and an electric ram plus the other 60 series instruments. It was working quite hard with 20kts of wind. The fridge is also the original and takes 5 amps for about 12 mins every hour.

There is no sign that I know of that the batteries are not as in as good condition as when they were installed. They consume about 2 litres of water a year as they always have.
 
Not having a battery monitor I've always just used the batt volts as my main charge level indicator.

The voltage you're seeing on the batteries after the load is disconnected (12.6) suggests that they were still nearly full of charge, or very nearly, when you then re-charged them. And under a 10A load for them to only go as low as 12.4 or 12.5 confirms that also. I used to roughly guess mine were less than half discharged (the lowest I would let them get) if they went much below 12.0V with 5A coming out of them (my bank was about 200ah at the time) based on what they would then bounce back up to under no load.

But perhaps your solar panel was keeping the reading of 12.6 a little higher than it would have been without it?

Many sites list charge levels when under no load approx. Like this one:

http://www.energymatters.com.au/renewable-energy/batteries/battery-voltage-discharge.php

So if that's the normal levels you've seen you've probs hardly ever discharged them much so perhaps they're still in fine fettle.

But I know nothing of one way degradation over time that is not manifested in the voltages.
 
Sailfree said:
Obviously 2 years ago!!
Click to expand...

Excuse my initial flippant answer as they seem fine to me but note your subsequent question about increased cost if replaced in France.

I think I would do some market research from now on and as Vic says they don't owe you anything so replace them when a good buy comes up.
 
My Bosch starter battery lasted 9 years and the 140A domestic has just failed after 12 years so you are near the mark. Both failed without warning. The problem with the 140A is that it weighs 39kg so not the easiest to replace.
 
Wet cell batteries do not often last much more than 10 years so they probably have not got much life left in them, but there is nothing in the voltages you quote that suggests a problem with the batteries.
If you are concerned you can do a capacity test which requires no extra equipment, but it does shorten the life of the battery.
 
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