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Old 26-07-2017, 05:48   #1
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Are My Batteries Toast?

Actually the title should read more like "How Can I Tell When My Batteries are Toast?" Is there a test I can do using my using my Fluke 374 clamp meter to determine the health of my batteries? I also found my hydrometer that went missing for a few months, but I don't know how to use it. Everything seems to be working fine with our 24v, 450ah Trojan house bank of 6v wet cell batteries, but what got my attention was inside my new Smart Gauge instructions which stated that the energy saver mode would self initiate anytime the voltage was to drop below 26.4v, but it didn't indicate if this was average or any one time event. I see the voltage dropping below this figure all the time, but the gauge doesn't go into energy saving mode.

So I finally got around to installing the "Smart Gauge." Can anyone explain why the voltage varies so much? Most of the time it hovers up aroud 28v, but after I use the microwave it'll drop down to as low as 24.5v then slowly creep back up over the next 5 minutes or so. When the freezer of fridge turns on, it drops down in the 26.5v-27v zone, then creeping back up to 28v with the fridge still running over the next 2 minutes. Anytime there's cloud cover and the solar production drops, the Smart Meter voltage indicator will read figures in the 25v-26.5v volt range with the fridge running. The sun comes out, then back up to 28v.

Also, since I added the solar and got it online, the batteries are using much less water. I refill the water every 30 days per maintenance schedule, and this month nearly half of the cells didn't require any water to be added.

Why the change? In the past, I've always needed to fill each cell with nearly the same amount of water, approximately 50-75cc in each one. Now almost nothing required.

One more note: I've been noticing a big drop off in the performance of our windlass over the past two months which actually began last season. If I revv the engine in idle or run the generator while taking up the anchor, it runs OK taking up the chain but still struggles with the anchor in 45ft depths. I've ordered a new set of windlass motor brushes per manufacturer recommendation, but is this maybe a symptom of something more sinister? I've already cleaned the contacts and will need to wait a week for help to arrive in order to do further testing and change the brushes.
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Old 26-07-2017, 05:55   #2
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Re: Are My Batteries Toast?

microwave is a big draw that sucks down the batteries and it takes a little while form them to recover due to internal resistance (my batteries will go into alarm while running the microwave on the inverter)

less water because the solar charging is slower (I only check mine every couple months and hardly use any water)

windlass - is it a separate battery measure the voltage under load to see how far it drops. have you cleaned the connections? when was the last time you took it apart and cleaned and lubed it
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Old 26-07-2017, 06:06   #3
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Re: Are My Batteries Toast?

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microwave is a big draw that sucks down the batteries and it takes a little while form them to recover due to internal resistance (my batteries will go into alarm while running the microwave on the inverter)

less water because the solar charging is slower (I only check mine every couple months and hardly use any water)

windlass - is it a separate battery measure the voltage under load to see how far it drops. have you cleaned the connections? when was the last time you took it apart and cleaned and lubed it
The windlass gets serviced prior to the start of every season, so two months ago. When help arrives late next week, we'll be taking apart the entire windlass while replacing the motor brushes. There're three projects on the list before we can get underway, another being that all the bearings on our main sail furling swivel from 73ft up came raining down on me the other day, they'll need replacement otherwise no mainsail for a while... which isn't the end of the world.
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Old 26-07-2017, 06:53   #4
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Re: Are My Batteries Toast?

1) 28 volts would be a good example of a battery bank under charge at near full charge state
2) The voltage drops you refer to all look very normal, as above things like microwaves draw a lot of power(as does your anchor windlass.
3) Not using so much water would be due to better controlled voltage in put and not as much as a alternator in most cases, the higher amp input the more gas is given off during charging , there some good battery caps available that will bring that down even more and have other benefits as follows

http://www.rollsbattery.com/wp-conte...RollsR-CAP.pdf

4) To test your batteries you need a "load tester" which is connected to both battery posts for a very short time (every tester is different) but it basically puts a huge load on the battery and registers the condition.

https://www.harborfreight.com/100-am...ter-61747.html

Cheers Steve
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Old 26-07-2017, 06:57   #5
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Re: Are My Batteries Toast?

I do know that as they get old they lose capacity... which is almost impossible to restore.

As they are getting very old they charge in less time... because they can only absorb less charge.

Think of the batter as a glass of water... The following is not a perfect analogy but it illustrates what we are up against.

The amount of water is the AH capacity Bigger glass more capacity of course ... when you use the battery you are "drinking" the water and when you are charging you are refilling the glass. However the problem is that when you refill the water has some sediment in it... and this sediment builds and builds and it reduced the capacity of water... so as the batt ages it can only take a smaller and smaller about of water because the bottom of the glass is filling with sediment. The battery is toast when the sediment is up to the rim. At some point it becomes impossible to add capacity.

There are strategies for getting the crap which coats the batteries off... de sulfating. However the sulfating of the battery is simply an artifact of its use.

Sulfation is a build-up of lead sulfate crystals, is the number one cause of early failures of lead-acid, sealed AGM or flooded (wet cell-filler caps) batteries. A sulfated battery can lead to: loss of cranking power. longer charging times.
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Old 26-07-2017, 06:58   #6
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Re: Are My Batteries Toast?

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Originally Posted by Captsteve53 View Post
1) 28 volts would be a good example of a battery bank under charge at near full charge state
2) The voltage drops you refer to all look very normal, as above things like microwaves draw a lot of power(as does your anchor windlass.
3) Not using so much water would be due to better controlled voltage in put and not as much as a alternator in most cases, the higher amp input the more gas is given off during charging , there some good battery caps available that will bring that down even more and have other benefits as follows

http://www.rollsbattery.com/wp-conte...RollsR-CAP.pdf

4) To test your batteries you need a "load tester" which is connected to both battery posts for a very short time (every tester is different) but it basically puts a huge load on the battery and registers the condition.

https://www.harborfreight.com/100-am...ter-61747.html

Cheers Steve
Thanks Steve
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Old 26-07-2017, 07:53   #7
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Re: Are My Batteries Toast?

As Steve says, the proper way to test a battery is with a battery tester. It puts a great big amp draw on the battery for about 10 seconds and measures its voltage whilst doing so. If the battery stays above around 11.5v it is probably good. If you don't have a load tester, you could just run the windlass, assuming that it is connected directly to your battery bank and assuming that it doesn't have an incoming charge. If your bank stays above 24v while the windlass is running you can be pretty sure that your batteries are OK.
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Old 26-07-2017, 07:59   #8
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Re: Are My Batteries Toast?

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As Steve says, the proper way to test a battery is with a battery tester. It puts a great big amp draw on the battery for about 10 seconds and measures its voltage whilst doing so. If the battery stays above around 11.5v it is probably good. If you don't have a load tester, you could just run the windlass, assuming that it is connected directly to your battery bank and assuming that it doesn't have an incoming charge. If your bank stays above 24v while the windlass is running you can be pretty sure that your batteries are OK.
I'll try this as soon as my wife returns. Good idea.

No, I can do it today. I'll wait until the solar stops charging this evening, then video record the Smartgauge voltage while using the windlass using my iPad.
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Old 26-07-2017, 08:03   #9
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Re: Are My Batteries Toast?

Your voltage variations seem normal to me. Give the SmartGauge a little time to settle down as well. They can be a bit erratic while they learn the bank.
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Old 26-07-2017, 08:05   #10
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Re: Are My Batteries Toast?

I should add that you may have a voltage drop in your windlass circuit. Check all connections and clean them. Also visually inspect the entire cable for signs of chafe.
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Old 26-07-2017, 08:06   #11
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Re: Are My Batteries Toast?

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Your voltage variations seem normal to me. Give the SmartGauge a little time to settle down as well. They can be a bit erratic while they learn the bank.
Will it eventually display an average voltage after settling down, or will it continue to be kind of all over the place?
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Old 26-07-2017, 08:20   #12
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Re: Are My Batteries Toast?

Do you ever equalize your batteries?'your new charger will most likely have that option.....not that this answers any of your questions.
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Old 26-07-2017, 08:42   #13
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Re: Are My Batteries Toast?

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Do you ever equalize your batteries?'your new charger will most likely have that option.....not that this answers any of your questions.
I don't know how to equalize the batteries.
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Old 26-07-2017, 08:53   #14
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Re: Are My Batteries Toast?

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I don't know how to equalize the batteries.
Your battery manufacturer should have information on that, voltages and times and all details.
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Old 26-07-2017, 08:57   #15
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Re: Are My Batteries Toast?

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I don't know how to equalize the batteries.
That should be high on the list of priorities. It sounds like you are like a lot of us: your battery knowledge may be "partial, in depth". Things like "rest period after charge" and "ambient temperature of bank correction" are not that esoteric, but if you don't know some basics, you could either do some damage, fail to service the bank correctly, or misinterpret what your testing is telling you.

I would try to absorb, pun intended, the basics of battery charging, especially with a big 24-volt bank as you have, as I would wager it's a PITA to change them out more than every seven years or so.
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