Would you say these batteries are stuffed?

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DaveNTL

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Been charging the house batteries via the genny / mastervolt charger, and then the main engine / alternator.

2 gel batteries cells 165 AH each in parallel, so 330 AH.

I get the feeling that they aren't holding a charge or charging up as they should.

This what happened:

Charging through charger

Time (of day) / Amps (total capacity)
4.45 / 242.5
5.15 / 243.4
5.35 / 243.8
6.05 / 244.1

Genny / charger off for half an hour, amps dropped to 239.5 in half an hour. Started main engine / alternator / smart (3 stage regulator).

Ran for 15 mins, capacity rose to 242.7 Amps. Charge could be seen to be slowing down as voltage rose to regulator set point of 14.3V.

It's now 40 minutes later and voltage is at 12.73V, and charge is 234.8 A.

Annoying if they are duff because they were only installed March last year. Eleven month layup may be to blame but still.
 
How do you measure AH capacity?

AFAIK (that you probably already know) is that gel batteries are slow in charging...
 
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How do you measure AH capacity?

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I have THIS monitor system to tell me.

Yeah, I know they are slow on the absorption phase - the mastervolt charger is set to go to 'float' after 4 hours on absorption phase if the voltage set point is met, which means even slower charging.

I've been running the genny again and now (10.15pm) its where it was at 5pm. Battery temp is 93F.
 
But surely you should stand and measure voltage later ...

I apprecaite all these gixmos .... batt monitors etc. - but they are only estimating against voltage etc.

Surely the way to do it is to charge up fully. Disconnect and leave to stand for a short period ... meter the voltage across each separately. Go back 2 or 3 days later and meter voltage again.
IMHO using a batt monitor and also leaving battery connected to drain no matter how small will interefere with your diagnostic .....
 
Re: But surely you should stand and measure voltage later ...

[ QUOTE ]
I apprecaite all these gixmos .... batt monitors etc. - but they are only estimating against voltage etc.

[/ QUOTE ]

Some battery monitors measure current discharge against time - ie actual amp hours used. They then measure charging current against time for the recharge cycle and factor in a % for losses in the charge /discharge cycle.

They DO NOT all 'estimate' capacity from voltage.

Voltage is not always an accurate way of measuring charge state of a battery. Surface effects or one 'slightly faulty cell' can produce odd readings on a purely 'voltage' indication. If you cannot measure current and voltage against time with an automatic monitor, then the only accurate way to measure the capacity of a battery bank is to disconnect it from everything elese and discharge it into a known load and measure its voltage with an accurate voltmeter. Remember that capacity is also a function of the drain current. Low loads will produce higher capacity readings. You need to choose a load current similar to the domestic load you normally experience.
 
I am not a battery expert but I have had a similar experience with gel batteries. Others may know more, and I am happy to be corrected if wrong but gel batteries don't seem to like to remain discharged for a long time and can be reluctant to accept a full charge when asked to "wake up" after a long time discharged. It may be that you need to have them brought up to a fully charged state over a longer period of time to "wake them up". Either way, true or not, as you have two batteries, I would disconnect them one at a time, and leave on charge at a lower rate of charge for 48 hours or more. If they don't give you a better performance after that time they are junk. Either way you may find it's only one that is duff and the other is OK if you test them seperately. The problem may only be with one duff cell.
 
[ QUOTE ]
I am not a battery expert but I have had a similar experience with gel batteries. Others may know more, and I am happy to be corrected if wrong but gel batteries don't seem to like to remain discharged for a long time and can be reluctant to accept a full charge when asked to "wake up" after a long time discharged. It may be that you need to have them brought up to a fully charged state over a longer period of time to "wake them up". Either way, true or not, as you have two batteries, I would disconnect them one at a time, and leave on charge at a lower rate of charge for 48 hours or more. If they don't give you a better performance after that time they are junk. Either way you may find it's only one that is duff and the other is OK if you test them seperately. The problem may only be with one duff cell.

[/ QUOTE ]No lead acid batteries like to be discharged fully and left discharged. The quickest and surest way of killing a battery...

Rule of thumb - try not to discharge to less than 50% and always recharge as soon as possible.
 
Try resetting some parameters...

The Ample Power EMON2 monitor is a very sophisticated bit of kit, but it's also quite complicated to set up correctly. Before you believe what it's telling you about your batteries, you ought to check that the EMON2 parameters are correctly set.

The main ones you need to check are the FULL V and FULL A settings, in particular to ensure that the FULL V is in line with the settings of your mains charger and smart regulator (both of which have presumably been set up for gel batteries). The SIZE setting might be better set to say 300Ah rather than the theoretical 330Ah. You could also set the PEUKERT exponent to 1.1 rather than the default 1.125, as gel batteries have a lower Peukert number than regular lead-acid types.

Next, you need to discharge the bank by at least 50% and then recharge it until the EMON2 says the batteries are full. If you do this a couple of times, the EMON2 will compute the recharge efficiency and will then be able to show more accurate information.

Hopefully, the end result will be that the EMON2 will show a capacity closer to 300Ah. It's unlikely that an extended lay-up will have damaged the gel batteries, as they have a very low rate of self-discharge.

Best of luck!
 
I am no expert either but I have had problems with low performance on my battery lately and I did come across this website which indicates that the cold of the winter may have something to do with it since as it gets colder the battery loses capacity. I know your sample times were not that far apart but, maybe taking the battery home and trying it in a warm room would give you a more accurate test. I am going to give it a try anyway.

http://www.solarsense.com/Spec_Your_System/Run_Times.html
 
Re: But surely you should stand and measure voltage later ...

[ QUOTE ]
Surely the way to do it is to charge up fully. Disconnect and leave to stand for a short period ... meter the voltage across each separately. Go back 2 or 3 days later and meter voltage again.

[/ QUOTE ]

Comments appreciated, and yes, that would also be a way, but I'm living on it, at anchor and hoping to move off for 4 days where i won't be able to do anything about it inbetween.
 
thanks for that - I'm not sure gel batteries are ideal either (especially with the cost) but at the moment i'm living with them as to change to, say, wet cell, will involve a lot of joinery with the housings.

on the trip here they did charge to 100% off the engine / alternator
 
Re: Try resetting some parameters...

good points pvb - i did study the ample power literature thoroughly last night as i was wondering along the same lines.

i checked that the dip switches are right for the gel batteries - all seems fine - it could have been that. I'll look into the lowering of the 100% capacity setting - only doubts i would have is that it has charged to 100% in the last few weeks.
 
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