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Old 13-04-2019, 10:41   #31
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Re: Resting 12v Battery Voltage Reading Is 13.2v; What Am I Missing?

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Originally Posted by john61ct View Post
That is not a quality battery for true deep cycling usage. ATLASBX is a Korean firm.

If you require AGM, then a maker like Lifeline or Odyssey would be a much better source.

FLA would be much better value though.

Where are you located?

True deep cycle batteries are what the OP needs. I don't have any experience with Ca lead acid so can only take the advice that they are only useful as starter batteries.


I used to recommend AGM batteries for cruisers but have found that they die as fast with constant cycling without getting back to a full SOC as do LA batteries. The Fireflys may help with that but when I tried to buy them they were always sold out and did not come in a case size that I could accommodate.
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Old 13-04-2019, 10:59   #32
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Re: Resting 12v Battery Voltage Reading Is 13.2v; What Am I Missing?

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Originally Posted by lewisa View Post
You can buy a reasonable quality battery load tester (a big resistor and a meter) on line or at NAPA for about 25-35 US dollars. Well worth having aboard and useful to monitor battery condition.
These are not in any way precise for measuring SoH, remaining capacity for deep cycle banks.

A 20-hr load test or similar is really the only practical way if you want to be proactive about judging EoL.
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Old 13-04-2019, 11:02   #33
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Re: Resting 12v Battery Voltage Reading Is 13.2v; What Am I Missing?

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Originally Posted by exMaggieDrum View Post
Somehow you will need to find a way to routinely recharge your batteries (probably new ones) to as close to 100% as possible.
Or for those for whom that is literally impossible, live with much shorter lifespan.

Buying the cheapest-still quality batts **designed for deep cycling** is required to ensure that is still as cheap per Ah per year as possible.
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Old 13-04-2019, 12:00   #34
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Re: Resting 12v Battery Voltage Reading Is 13.2v; What Am I Missing?

Although I certainly agree that the 20 hr test is the most accurate method of determining the ultimate deep cycle battery condition, it is a difficult and time consuming test and requires figuring out a load that will provide reliable results. Even the CBA (computerized battery analyzer) has been shown to be less than highly accurate. In over 45 years of experience with FLA batteries (mostly Trojan T-105's), I have found that, after battery equalization, the load testers and specific gravity measures correlate well and do a remarkably good job of predicting battery condition. And they are quick and inexpensive. This assumes that the house bank is also used for starting or other high amperage demands.. Even a battery in fairly poor condition will run many devices that have a fairly small amp draw on start-up (radios, LED lighting, etc.) while failing to deliver the high initial amp draw of devices such as refrigeration compressors.
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Old 13-04-2019, 17:39   #35
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Re: Resting 12v Battery Voltage Reading Is 13.2v; What Am I Missing?

Yes, huge difference between people wanting to be proactive, replacing their bank at 75-80% SoH, vs those that want to keep pushing until signs of approaching EoL are readily apparent, want to try to eke another 6mo or a year out of them
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Old 14-04-2019, 00:02   #36
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Re: Resting 12v Battery Voltage Reading Is 13.2v; What Am I Missing?

If you were in the U.S. I would recommend two or maybe four GC2 size golf cart batteries from Sams Club, as a backup bank for when you want to do a 20 hour capacity test on the main bank. It is a cheap and practical solution. In Greece? I would look for a pair of T105s though in Europe I don't think the price gap between LiFeP04 prismatics and FLA is as much as in the U.S. so a LiFeP04 setup would have its charms, yeah.



Are you running LED lights? Way cheaper than incandescent in terms of watts. Modern inverters are fairly efficient but still it is a good idea to have your inverter no more than 50% over your usual load. You could have a big one and a little one. Turn the one you don't need, or both when you don't need either one, OFF. Switching from power hungry laptop to a Raspberry Pi and a 7" touch screen will save some juice, too. Or buy a refurb Note3 or Tab2 7" tablet. DC/DC converter and USB port work nicely to power a tablet, Pi, or phone. One per device. Keep VHF, HAM, Marine SSB, SWL, etc radios off when not needed. You can probably do a LOT of things to reduce your power needs. Then look at upgrading your solar. Solar is great for topping off and float charging. Main Engine or Genset are not very efficient for that, but work okay for bulk charging, if your solar is not up to the task or you are getting a lot of cloudy weather. I personally dislike wind chargers but it might be a thing, for you and your situation.
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Old 14-04-2019, 15:18   #37
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Resting 12v Battery Voltage Reading Is 13.2v; What Am I Missing?

Good Afternoon.

I used to design batteries a while back and flooded cell, including absorbed glass mat (AGM) and gel cell, and actually quite simple. Each cell is designed to output 2.25 Vdc so 6 cells typical in a 12 volt battery is designed to have 13.5 Vdc (6 x 2.25 Vdc) at rest. As batteries age due to cycling their rest voltage tends to change. However a battery with a rest voltage between 11.5 and 13.5 Vdc is typically a healthy battery. A common problem with determining battery health is that voltage alone is not a good indicator. Batteries have to be able to do 2 things provide voltage AND load current.


The easiest way to determine battery health is connecting a battery load tester similar to this one https://www.walmart.com/ip/Milton-12...kaAl1qEALw_wcB (copy and paste into your browser).


The nice thing I like about battery testers is that they're fairly cheap, load test the battery, and give a instant indication of whether the battery is healthy enough to provide duty voltage and current (load power to drive house items and/or start engines). The load tester can be applied to any battery and you don't have to disconnect any wires to perform the test on any battery at rest (unloaded and without engine operating).


However if you don't have a battery health (load) tester but do have a volt meter …… you can perform a two person poor man's battery test. Method isn't great but it works. One person applies the volt meter a battery to test and watches the read out. A second person starts the engine while the first person watches the volt meter. If the volt meter reading drops below 10.8 VDC while cranking the engine it is probably time to think about a new battery. You perform this test on each battery cranking the engine each time.


To test your charging system, apply a volt meter to the battery string typically 12.5 Vdc to 13.5 Vdc at rest then start the engine. The voltage should increase to 13.8 to 14.8 Vdc to replace the charge drawn out to start the engine. If batteries are really depleted this voltage may be lower in the beginning but slowly increase. If this occurs everything should be okay and the battery string voltage should increase to 13.8 Vdc and be stable when the battery string is fully charged. If the battery string voltage changes by 1-2 Vdc while charging …. it could indicate an open or short in one of the battery cells and you should determine which one and replace it ……. or replace the whole string if unsure. Typical 12 Vdc deep cycle boat batteries are good for 3 to 5 years depending on how often they are discharged / recharged. Usually when one battery begins exhibiting problems they all follow suit and should be considered for replacement.

A bit long post …… but I hope this helps.

Cheers!
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Old 14-04-2019, 17:29   #38
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Re: Resting 12v Battery Voltage Reading Is 13.2v; What Am I Missing?

Sorry but again, the sort of methods and gear used for testing **cranking** batteries is maybe not useless for a big expensive deep cycling bank, but saying "no accuracy, only roughly approximate" is a major understatement.
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