Battery trouble, so I ran an experiment.

[vmattiola]

Hi all,

I've been having serious problems with my batteries holding charge, so today did a bit of a charging/loading experiment to try and get some data. I'll preface by saying that my knowledge of electrical engineering is limited, but I understand the basics.

Here's what happened: For the 1.5 months I was away from the boat. No solar, no wind genny, just sitting on a mooring ball. I had everything turned off on the panels, EXCEPT for the auto bilge pump. We take some rain water down the mast and leak a bit, so every few days the float switch activates and drains the bilge for me. I knew this would be an issue with the battery life, and had only planned to be away for a week or two. Life got in the way, so the boat sat. I had nightmares about the batteries dying, bilge pump not working, and boat sinking. Bad.

Now I'm back at the boat. Batteries totally drained (duh...) and water in the bilge. Pumped clear, generator on, batteries charging....but I think I might have damaged my cells.

The long and short of it is: they don't hold charge anymore.

Here's what we've got: 2 x ONE YEAR OLD Exide Gel 210Ah batteries AND 2 x older "Chloride Industrial" 100Ah wet cell batteries.

I ran generator (Honda EU 2000i - with 120V / 13.3A output) for 90 mins today and recorded the meter readings on batteries.

Time (min) Voltage
0 8.78
*generator on*
15 13.39
30 13.43
60 13.48
90 13.47
*generator off*
*ALL lights, fridge, instruments, water pump, sink pump, bilge pump ON*
0 12.04
2 11.84
4 11.79
7 11.68
9 11.49
30 11.26
47 10.83
60 10.05

I observed that my charger was blinking yellow "Boost/Absorption" up until 90mins, and never went to "Floating" mode....what does this mean?

I also observed at t = 0 min (generator off) that my OLD battery bank was at 12.02, while NEW battery bank at 11.85.

Questions:
Have I permanently damaged my cells in new batteries?
Am I simply not charging long enough?
Can you visually inspect gel batteries?

Thanks,

Vinny

[Sailmonkey]

So you have 600 ah of storage capacity and you charged for 90 minutes..........you haven't even made a dent in the needed electricity!!

How many amps is your charger? Maybe 40 max?

You'll need to charge for 15 hours in a zero loss world. In reality closer to 30.




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[Whitebread117]

What he said.

I boost my 1040ah bank with the same Honda when we have cloudy calm days. In bulk charging mode (sub 75% state of charge) it can only put about 120a per hr in the bank. Your absorption rate is less with a smaller bank you didn't even get 1/4 charged in 90 minutes ( and your charge rate will drop off drastically as you get closer to full charge). Your Honda has a whole lot more work to do.

[Wanderlust]

What Sailmonkey and Whitebread said.

When you used the generator, did you charge from the 12V outlet or 120V and then into a battery charger? From your description I assume you were feeding into a battery charger. Not the most efficient and you would not achieve the full 13 amps. However, specs show the 12V outlet only produces 8 amps ... they don't list the voltage. Presumable 12V is a nominal voltage and it produces over 14v as needed for battery charging. So 120v into a battery charger may give the best result despite the inefficiencies which would give you less than that 13 amps. Perhaps someone with a similar unit can offer advice here.

Your battery bank is 620 amp/hours, which will require a long time to bring back up with a 13 amp charge rate. Running for 90 minutes at 13 amps only put 1 x 30th of a charge into them, so you would see negligible change. But running the generator for 30 times as long will still not be enough as the charge rate diminishes when the batteries near their full state of charge.

If you have no alternative to the Honda, I would separate the batteries and do them one at a time. Doing one at a time gives you power to operate things while you attend to the next one. After charging, allow each to sit overnight without being connected and then test voltages. Also, get a hydrometer so you can more accurately assess the state of charge.

The other issue I note is that you appear to have mixed different battery technologies, which prefer different charge rates, and discharge differently. There have been a few discussions on here about that issue. I would not put them in the same bank.

[Fishman_Tx]

Ditto to both. I maintain DC battery systems and generators for AT&T that use much larger batteries, but the theory is all the same.

Your vdc at 13+ is the charger. At charger off your voltage is low due to insufficient charge time.

You should be floating any where from 13 and some change to a very low 14vdc, depending on the controller float point settings. At float, any individual cell that reads in the high twelves consistently should have an eye kept on it. Anything less than 12.50 vdc on an individual cell at float should have a boost charge done. You can do a boost charge on any single cell in situ with a common car charger, but read the controller manual before doing this to see what it will tolerate. All else, de-strap the cell and put the charger on for 24 hrs. Re-strap and allow 24 more for equalization, then recheck the float. If it is declining under 13 and/or drops back into the low twelves, replace it. The newer sealed marine cells are best (no acid hassle or spills).

Start keeping a log of the overall string float vdc and the individual cells once a month and you'll always catch the trouble before it catches you.

[socaldmax]

Originally Posted by Wanderlust

What Sailmonkey and Whitebread said.

When you used the generator, did you charge from the 12V outlet or 120V and then into a battery charger? From your description I assume you were feeding into a battery charger. Not the most efficient and you would not achieve the full 13 amps. However, specs show the 12V outlet only produces 8 amps ... they don't list the voltage. Presumable 12V is a nominal voltage and it produces over 14v as needed for battery charging. So 120v into a battery charger may give the best result despite the inefficiencies which would give you less than that 13 amps. Perhaps someone with a similar unit can offer advice here.

Your battery bank is 620 amp/hours, which will require a long time to bring back up with a 13 amp charge rate. Running for 90 minutes at 13 amps only put 1 x 30th of a charge into them, so you would see negligible change. But running the generator for 30 times as long will still not be enough as the charge rate diminishes when the batteries near their full state of charge.

If you have no alternative to the Honda, I would separate the batteries and do them one at a time. Doing one at a time gives you power to operate things while you attend to the next one. After charging, allow each to sit overnight without being connected and then test voltages. Also, get a hydrometer so you can more accurately assess the state of charge.

The other issue I note is that you appear to have mixed different battery technologies, which prefer different charge rates, and discharge differently. There have been a few discussions on here about that issue. I would not put them in the same bank.

Please tell me that you aren't confusing 13A @ 120V AC with 13A @14V DC.

Depending on what output rating his battery charger is, he may have been putting up to roughly 120A into the bank per hr.

He left out a lot of important information. What brand and rating of battery charger he uses, what was the charge rate when he stopped at 90 minutes, etc. I also agree that 2 different types of batteries shouldn't be mixed.

Even a single 120W solar panel with a cheap $100 controller would have kept the batteries topped off and the bilge pump running. There could be one dead battery, or multiple. They'll all have to be fully charged, then tested individually to determine actual capacity. Even identical batteries will respond differently to being fully discharged.

[socaldmax]

Originally Posted by Fishman_Tx

Ditto to both. I maintain DC battery systems and generators for AT&T that use much larger batteries, but the theory is all the same.

You should be floating any where from 13 and change to a very low 14vdc, depending on the controller float point settings. Any individual cell that reads in the high twelves consistently should have an eye kept on it. Anything less than 12.50 vdc at float should have a boost charge done. You can do a boost charge on any single cell in situ with a common car charger, but read the controller manual before doing this to see what it will tolerate. All else, de-strap the cell and put the charger on for 24 hrs. Re-strap and allow 24 more for equalization, then recheck the float. If it is declining under 13 and/or drops back into the low twelves, replace it.

Start keeping a log of the overall string float vdc and the individual cells once a month and you'll always catch the trouble before it catches you.

I think you mean batteries when you used the term "cells."

A lead acid cell produces roughly 2V, 6 of those comprise a 12v battery. You can isolate a 12V battery from the bank, but you can't isolate a cell, nor do most people have 2v chargers.

[Wanderlust]

Originally Posted by socaldmax

Please tell me that you aren't confusing 13A @ 120V AC with 13A @14V DC.

You got me. I was.

I'm certainly aware of the substantial difference but my mind was focused on what I would do ... I only have a 15 amp charger for mains power. So charging via the DC outlet compared to AC outlet into a charger would not make a huge difference for me .... both methods far too slow.

I agree that a high output charger connected to the 120v @ 13 amps will be a vastly better option. Nevertheless, the principle still stands that only a small percentage of a full charge would have been applied in the 90 minutes even with a very substantial charger.

[Adelie]

Several things.

The generator putting out 13a at 120v becomes 130a at 12v. With actual charger voltage about 14v and various inefficiencies lets call it 100a at charging voltage. What's your charger rated for? At 80% DoD (Depth of Discharge) you need to make up 496a-hr or about 5hr at 100a. The reality is that the batteries will move from bulk charging to acceptance charging at about 25%DoD and then the current the batteries will accept tapers off and that drags on almost forever. The bulk charging from 80% to 25% DoD will be about 2h50m and as a guess acceptance will be at least twice that long.
Float is when the batteries pretty much get to fully charged and the charger switches to a specific voltage that is current limited to maintain the batteries at full charge with no load on them. The reason for this is that lead acid batteris, including gel and agm, self discharge at a significant rate.

Which leads to item 2, self-discharge of lead acid batteries. The best self-discharge rate you can expect is 0.5% capacity per day. It can be as bad as 5% depending on age and battery chemistry. See the following for a discussion: http://www.gelcoservices.com.au/docs...ge%20Paper.pdf
Add even a small intermittent loads on that and it's not a surprise your batteries were dead in 45 days. You really need to get a modest solar panel and charge controller, say, 30-50w panel with a cheap PWM controller to maintain charge and keep the pump going.

Mixing battery types and ages. Bad mojo. Different types require different charging voltages and regimens. Even different ages of the same battery leads to problems. However different sizes of the the same type and age battery is fine. Once the batteries are off a charging source the weaker battery will draw the rest down with it by recharging off the others, said recharging involves efficiency losses. You could separate the 2 types of battery you have into separate banks that are kept isolated except for short high demand periods. If you go with a full solar panel setup you don't have to isolate specific panels to specific batteries, but you need separate charge controllers so the 2 banks are fed the way each likes.

In the short term, isolate the 2 types of batteries in separate banks and charge them separately with your charger. Make sure you change the settings on the charger to match the battery type you are charging. Possibly even charge each battery alone if you have the time. For the FLAs get a specific gravity meter from an auto parts store and check individual cells before and after charging. That may tell you if one battery has a bad cell and that battery needs to be out of service so it doesn't drag the others down. You can't do that with Gels. It may be worth your while to get a battery load tester. Don't know what they cost but probably not cheap nor terribly expensive.

In the long term go with one type of battery. For preference FLAs. Gels are fine but much touchier about charging. AGMs would not suit you at all. See the following discussions:
Systems.
AGM Batteries - Making The Choice | SailboatOwners.com Forums

Good luck

Edit: Oh, yeah; get 6v golf cart batteries unless you get Rolls or Trojan. For second tier suppliers, most or all of what they list as Marine deep cycle is really a hybrid deep cycle/starting battery that doesn't last as well as true deep cycles. Rolls and Trojan have real deep cycles in smaller sizes. For everybody else 6v golf cart is the only way to be sure unless you do a lot of technical reading to figure out what is really deep cycle and what is really a hybrid.

[Fishman_Tx]

Originally Posted by socaldmax

I think you mean batteries when you used the term "cells."

A lead acid cell produces roughly 2V, 6 of those comprise a 12v battery. You can isolate a 12V battery from the bank, but you can't isolate a cell, nor do most people have 2v chargers.

Yup, but you're singing to the choir here. LOL!
I've been doing this for 17 years now, so we needn't banty semantics over terminology. Don't want to confuse the OP.
But.. "whatever floats the boat".

When dealing with 11 strings of 24 "batteries" each we just refer to them as "cells". Old school lead-acid batteries have individual cells that you can add water, acid, etc. Sealed batteries can be referred to as cells in a string as they do not have individually serviceable "cells" and are components of the whole; i.e. cell A24 = 12.29vdc @ 0.25A. We use many strings of multiple (24) "cells" in series-parallel to start 2mw turbine generators for backup power in multi-floor buildings.

Just the way we at AT&T play the game.

[socaldmax]

Originally Posted by Wanderlust

You got me. I was.

I'm certainly aware of the substantial difference but my mind was focused on what I would do ... I only have a 15 amp charger for mains power. So charging via the DC outlet compared to AC outlet into a charger would not make a huge difference for me .... both methods far too slow.

I agree that a high output charger connected to the 120v @ 13 amps will be a vastly better option. Nevertheless, the principle still stands that only a small percentage of a full charge would have been applied in the 90 minutes even with a very substantial charger.

Absolutely!

[socaldmax]

Originally Posted by Fishman_Tx

Yup, but you're singing to the choir here. LOL!
I've been doing this for 17 years now, so we needn't banty semantics over terminology. Don't want to confuse the OP.
But.. "whatever floats the boat".

When dealing with 11 strings of 24 "batteries" each we just refer to them as "cells". Old school lead-acid batteries have individual cells that you can add water, acid, etc. Sealed batteries can be referred to as cells in a string as they do not have individually serviceable "cells" and are components of the whole; i.e. cell A24 = 12.29vdc @ 0.25A. We use many strings of multiple (24) "cells" in series-parallel to start 2mw turbine generators for backup power in multi-floor buildings.

Just the way we at AT&T play the game.

I agree - we wouldn't want to confuse anyone, that's why I suggest we stick to the proper terminology that is commonly used. If the OP strolls into a battery store and says he wants to replace 2 of his cells, he's going to get either funny looks or laughed out of the store.

Just wait til StuM pops by and does a 140 page discourse on the errors of amps/hr and the correct usage of amps and amps per hour.

[pesarsten]

I have to ask, Is the Honda eu1000 a pure sine output generator or a modified sine output? I had problems using a large boost charger with an eu1000 and thought it was due to the output. If it is modified sine, then his charger output would be degraded wouldn't it?

[Fishman_Tx]

Originally Posted by socaldmax

I agree - we wouldn't want to confuse anyone, that's why I suggest we stick to the proper terminology that is commonly used. If the OP strolls into a battery store and says he wants to replace 2 of his cells, he's going to get either funny looks or laughed out of the store.

Just wait til StuM pops by and does a 140 page discourse on the errors of amps/hr and the correct usage of amps and amps per hour.

You know how it is though. Been drilling and stuffing boards since 1977 with a lot of inbred slang across 4 full rounds over 40 years of basic ac/dc through advanced digital as technology changed.

Re: StuM
God and the Saints preserve us!!!!
Not that!

[jeepbluetj]

Originally Posted by pesarsten

I have to ask, Is the Honda eu1000 a pure sine output generator or a modified sine output? I had problems using a large boost charger with an eu1000 and thought it was due to the output. If it is modified sine, then his charger output would be degraded wouldn't it?

yup. But the OP still needs about another 25 hours of charge no matter what.

Pull the batts. Put em on a charger in your garage. equalize the flooded ones. Then do a timed discharge and see what you got left. You may be fine, you may be hosed. I had the RV batts down to zilch once and they're fine now (2x GC6's)

90 min of charge is nothing if you're talking 400AH of battery on something like 30 or 40A charger.