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Sandero 12-07-2014 06:34

Optima Battery Dying?
I have an Optima Blue Top 55ah battery (2006) for the starting battery. It is charged via an Echo charge. The main house batts are a pair of 8D AGMs and have a pair of 55watt Siemens solar panels to trickle charge them via a PV14 regulator.

So typically the Link 20 will show the Optima at 12.70 or as high as 13+ volts... depending on what's up with the house batts.

No problem starting the engine ever.

Last evening when it was dark and no solar... the house were at 12.8 (topped up) and I noticed the Optima was reading 12.6 which to me means discharged or "dead" for an AGM... engine fired right up however.

This sunny AM the Optima is reading 12.75 and the house are at 13 (solar charge voltage???)

I think the echo charge is masking that the Optima is now essentially kaput. But how does it start the engine?

Any thoughts?

djmarchand 12-07-2014 07:26

Re: Optima Battery Dying?
12.6V is dead for an AGM? No it isn't dead at 12.6.

Google voltage state of charge agm, and you will find lots of SOC tables. Admittedly none of them are from a well known battery manufacturer, but they do say that 12.6 is approximately 80% charged.


barnakiel 12-07-2014 07:29

Re: Optima Battery Dying?
My thoughts: it is 2014. Replace.


Sandero 12-07-2014 07:35

Re: Optima Battery Dying?
Thanks! Clearly not dead... but seems to have lost capacity... I think of battery capacity as a glass full of water.... empty and refill..... but as they age it's as if the glass has more and more sand inside and can take less and less water... (refill) and empties sooner... less volume of water and more and more sand. At the end of the service life it's a glass full of sand and only a bit of water can fit in there!

S/V Illusion 12-07-2014 07:44

Re: Optima Battery Dying?
It might be a capacity issue, however, if you are depending on a 6 yr old battery which when new had a total 55 amphr capacity, I think the real problem should be self-evident.

Sandero 12-07-2014 08:18

Re: Optima Battery Dying?
The optima has performed perfectly as a start batt. Batts do have a service life and the Optima is a maintenance free one and has been maintained at proper voltage its entire life. Whether it's actually totally finished or not.... it seems to be near the end of its life.

It will be replaced soon.

btrayfors 12-07-2014 08:30

Re: Optima Battery Dying?

Batteries begin losing capacity right from new, and the process continues until they are deemed no longer useful by individual owners.

Think about the start battery in your car. It starts the car every morning for years.....until it doesn't. And you wonder why it started yesterday but won't start today.


Because it takes less than 1AH capacity to start the average cruising boat diesel. That's right, less than 1AH.

Yes, it will draw 150amps or so, but only for a few seconds until the engine starts. Multiply it out, and you'll find that the total energy used (amp-hours) is less than one AH.

Now, while you contemplate all the math and things which can intervene in reducing battery capacity and useful life over a multi-year period, order a new start battery. A plain old group 27 or group 31 will be fine, and will last as long or longer than the Optima. EchoCharges love 'em :-)

Also, keep in mind that a battery with almost all it's capacity eroded may still indicate normal voltages. Voltage does NOT equal capacity....only state-of-charge (SOC). A bad battery may have a 100%SOC, but only a small percentage of its original capacity remains -- e.g., if the plates are heavily sulfated and only a fraction of their original area is available to store and deliver electricity.


Sandero 12-07-2014 08:36

Re: Optima Battery Dying?
Thanks Bill... I can always depend on you for the straight story. I will get a new batt but I don't want one which requires maintenance... so I'll stick with the Optima.

zboss 13-07-2014 14:05

Re: Optima Battery Dying?

Originally Posted by btrayfors (Post 1582862)

Batteries begin losing capacity right from new, Bill

That is contrary to what Trojan says in their literature, which states that their batteries do not reach full capacity until after 50 to 100 cycles.

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