Battery dead???

[lumphammer]

Following on from various battery threads I thought I would capacity test my batteries. My procedure was charge using Sterling Pro 30A charger till it went into float mode. Disconnect battery and leave overnight. Following day battery was sitting at 13.3 v off load.
Connect an ebay battery load tester similar to the ones used to test LFP batteries, I set it to disconnect at 12.2v (50% SOC) and as they are 130Ah batteries I used the C20 discharge rate of 6.5 amps. In theory I should have been able to come back 10 hours later to watch the capacity test finish, but in just under 2 hours the voltage had dropped to the 12.2v level and the test ended.
The batteries are just over 3 years old .
Am I missing something in my test procedure, or have my batteries had it.
We are full time live-aboard and the batteries are normally continually connected to the charger in float mode.

 

[RupertW]

12.2V is 50 percent SOC when resting not under a load test. I’d be really insterested what voltage the batteries went back up to 15 minutes then an hour later under no load. But I still would have expected more than 2 hours.

 

[Boater Sam]

Would seem to be sulphated and have reduced capacity.

 

[William_H]

The results were somewhat disappointing for you. However I don't think it is time to throw away the batteries. 50% actual demonstrated capacity is not uncommon especially as you selected a fairly high cut off voltage. The real test of battery efficacy is in your usual operating mode. If they will not do the job you ask of them in terms of capacity then it is time for replacement. If however you are normally connected to mains charger you will not know if the batteries will do their job until you go on that voyage and anchor away from mains. I would risk it if you have engine charging. In any case keep note of the results of the test and try again in a year for comparison. ol'will

 

[fredrussell]

…Connect an ebay battery load tester similar to the ones used to test LFP batteries, I set it to disconnect at 12.2v (50% SOC) and as they are 130Ah batteries I used the C20 discharge rate of 6.5 amps. In theory I should have been able to come back 10 hours later to watch the capacity test finish, but in just under 2 hours the voltage had dropped to the 12.2v level and the test ended.
The batteries are just over 3 years old .

Your batteries are dead I reckon. Just been through this with my 2 year old no-brand batteries. If/when you replace, I would suggest name-brand batteries such as Varta, Exide, Bosch, Banner or the like.

 

[Boater Sam]

If you don't know how to charge and look after good expensive batteries they will die as fast as the cheapies.

 

[GHA]

Following on from various battery threads I thought I would capacity test my batteries. My procedure was charge using Sterling Pro 30A charger till it went into float mode. Disconnect battery and leave overnight. Following day battery was sitting at 13.3 v off load.
Connect an ebay battery load tester similar to the ones used to test LFP batteries, I set it to disconnect at 12.2v (50% SOC) and as they are 130Ah batteries I used the C20 discharge rate of 6.5 amps. In theory I should have been able to come back 10 hours later to watch the capacity test finish, but in just under 2 hours the voltage had dropped to the 12.2v level and the test ended.
The batteries are just over 3 years old .
Am I missing something in my test procedure, or have my batteries had it.
We are full time live-aboard and the batteries are normally continually connected to the charger in float mode.

A few thoughts...... charger going to float doesn't necessarily mean they are fully charged, the charger has no idea where the power goes so if you have a fridge & laptop running then the charger could drop to float very early.
Temperature makes a *big* difference. The state of charge against voltage graphs are really not a lot of help, voltage will vary depending on temperature, battery make, age & health. Istr capacity tests are at 80F

Might be an idea to try a few hours equalizing with the charger & have another go.

Liveaboard is a tough life for batteries if away from mains power, at a guess most batts will rarely actually get back to 100%. They hate that.

 

[lumphammer]

If you don't know how to charge and look after good expensive batteries they will die as fast as the cheapies.

[SARCASM]Thanks that's really helpful [/SARCASM]

 

[roaringgirl]

I killed a pair of mastervolt AGMs from new to dead in 18 months of living aboard. It was a combination of:
- Rarely getting to float due to inadequate solar installation
- 12v watermaker
- incorrectly installed alternator regulator causing overcharging
- multiple charge regulators all trying to simultaneously impose their float / bulk cycles simultaneously

 

[Boater Sam]

[SARCASM]Thanks that's really helpful [/SARCASM]

Not at all.

Its a truism. If you think it was sarcastic then you do not understand looking after lead acid batteries. But that is your problem, I will ignore you and leave you to continue wrecking batteries in your ignorance and unwillingness to take sensible advice.

 

[Resolution]

Not at all.

Its a truism. If you think it was sarcastic then you do not understand looking after lead acid batteries. But that is your problem, I will ignore you and leave you to continue wrecking batteries in your ignorance and unwillingness to take sensible advice.

So that makes two unhelpful replies.

 

[lumphammer]

So which bit of your original reply was helpful advice?

 

[jez56uk]

I killed a pair of mastervolt AGMs from new to dead in 18 months of living aboard. It was a combination of:
- Rarely getting to float due to inadequate solar installation
- 12v watermaker
- incorrectly installed alternator regulator causing overcharging
- multiple charge regulators all trying to simultaneously impose their float / bulk cycles simultaneously

what voltage was the alternator outputting to the batteries?

 

[roaringgirl]

what voltage was the alternator outputting to the batteries?

14 ish (once the batts were charged)

 

[Refueler]

My battery test is whether it will start my engine. I don't use leisure batterys - so both my batts are crankers ... either can turn my engine over without buckling plates.

If engine starts - then I'm fairly confident that battery is OK.

Tests of time vs amp discharge rates .... yes a viable test - but I've seen batterys survive a time vs amp test giving impression all is OK ... then when trying to start engine - failed.

The question of course is what is the intended duty of the battery ?
Is it slow discharge for light / moderate domestic ... even a clapped out cranker can often be sufficient, or is it also to provide high demand such as engine starting ? It comes down to age and ability of battery to maintain voltage under load.

 

[Refueler]

14 ish (once the batts were charged)

???? Alternator should pump out over 14V whatever state battery is in.

 

[roaringgirl]

???? Alternator should pump out over 14V whatever state battery is in.

When you measure the voltage of the alternator, it's in a circuit with the batteries. The voltage shown is dependent on the charge state of the batteries, the type of batteries you have, the power of the alternator and the decisions the alternator regulator makes.

 

[PaulRainbow]

When you measure the voltage of the alternator, it's in a circuit with the batteries. The voltage shown is dependent on the charge state of the batteries, the type of batteries you have, the power of the alternator and the decisions the alternator regulator makes.

The voltage reading at a charging source will be the output voltage of the charging source. The SOC is irrelevant, save for any influence that may have to the controller/regulator of the charging source. The power of the alternator has no bearing, power out is amps, not volts, a 25a alternator can output exactly the same volts as it's 125a equivalent.

 

[roaringgirl]

Hmm, until my batteries are at 99-100% full, with my 20A alternator running, the 'output' voltage is 13.2V, it creeps up as the SOC increases. At 95% it is 13.5V the current flowing into the battery as measured by the shunt is a steady 20A the whole time. Once the battery is full the voltage goes up to 14.2.

Does this mean my alternator is broken?

 

[alahol2]

Hmm, until my batteries are at 99-100% full, with my 20A alternator running, the 'output' voltage is 13.2V, it creeps up as the SOC increases. At 95% it is 13.5V the current flowing into the battery as measured by the shunt is a steady 20A the whole time. Once the battery is full the voltage goes up to 14.2.

Does this mean my alternator is broken?

If that is what truly happens then several things are likely to be broken.
Getting 20A out of a 20A alternator for the whole of a charge cycle is vitually (I'd say definitely but someone will prove me wrong) impossible.
If the shunt is reading 20A for the whole cycle than the shunt or meter is kaput.