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Old 09-20-2015, 12:07 PM   #1
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Deep cycle battery load testers ? Experience with ?

Maybe this thread should go in electrics forum but I am specifically concerned with the health of batteries when used in engine starting. In particular, I have twelve "no maintenance" Deka 1231MF batteries, rated at 1000 CCA @ 0 degrees F.

Seeing as they are sealed with no possibility of checking specific gravity....would a 500 amp capacity battery load tester, such as below, be adequate to give definitive thumbs up or down on any of these dozen batteries ?

http://www.ebay.com/itm/BRAND-NEW-50...992053&vxp=mtr

For that matter, would a 100 amp load tester be of any use for a battery this size ?

But getting back to the 500 amp ones....any thoughts on which one to buy ? The prices are all over the place...from $65 to $2,500. And from $65 to $150 on the lower end ones that all look the same in photos (except for black or red paint !) Is the $150 one really exactly the same as the $65 one ?

Thoughts ?
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Old 09-20-2015, 12:16 PM   #2
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I am a little puzzled about the inconsistency between the thread's title and your text. But assuming that 12 batteries wired together must be for house use, not starting here is my answer:

There is no simple ten second test for a deep cycle battery. You can put a 500 amp load on a battery and see how much the voltage drops over a few seconds, but that is a starting spec and not directly relevant for deep cycle use. But if a battery fails the 500 amp test then it probably isn't going to work real well for deep cycle house use either.

The proper way to test a deep cycle battery is to put a load on it equal to 1/20 of its amp hour capacity (that is how amp hours are rated) and see how long it lasts. If the voltage drops to 10.5 in 10 hours then you have half of the original capacity.

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Old 09-20-2015, 01:02 PM   #3
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I am a little puzzled about the inconsistency between the thread's title and your text. But assuming that 12 batteries wired together must be for house use, not starting here is my answer:
No wiring diagrams with the boat except for helm toggles, bilge pumps and the automatic fire system (ridiculous, I know), so, how the batteries are temporarily configured when one hits the "engine start" button is still a bit of a mystery.

All I know so far is 8 batteries are wired together as a unit and the other 4 are wired together as another unit. They are all 12 volt each, but the main engine starters are 24 volts. There are two "Big Boy" relays that combine the batteries when "engine start" button is pressed. But exactly which batteries are combined, not sure yet. It's not as simple as the 8 batteries combining with the 4, was there are two positive and two ground wires coming from each set (i.e. 4 plus and 4 negative cables total)

But really all that is irrelevant to my question...which is simply how best to test each battery to make sure there is not one or two suspect in the dozen...without waiting 10 hours to find out !
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Old 09-20-2015, 02:10 PM   #4
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Sounds like these are start batts, not deep cycle batts. All deep cycle batteries I'm familiar with are rated in AH, not CCA. All start batteries I'm familiar with are rated in CCA, not AH.

I'm ignoring all those in the middle that are considered "dual purpose" which seems more marketing that material.

Sorry I can't help with load testers. I'm more of a specific gravity guy. Some 'maintenance free' batteries have removable caps beneath the label, making it possible to check the SG.
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Old 09-20-2015, 02:30 PM   #5
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How old are they? We replace our house bank after ~5 years with regular use. Our SOC gives us an indication when the capicity is falling.

If your concerned about one battery in the bank, after the batteries have been fully charge, then disconnect everything; charger and interconnecting cables. Come back the next day and check the individual voltages with a digital DVM. They should all be about 12.6 volts. Not perfect but it should give you a general indication.
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Old 09-20-2015, 03:21 PM   #6
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How old are they? We replace our house bank after ~5 years with regular use. Our SOC gives us an indication when the capicity is falling.

If your concerned about one battery in the bank, after the batteries have been fully charge, then disconnect everything; charger and interconnecting cables. Come back the next day and check the individual voltages with a digital DVM. They should all be about 12.6 volts. Not perfect but it should give you a general indication.
Don't know how old they are... will call Deka tomorrow and hope they can tell me by the bar code number. Re your come back the next day idea...I thought of that, but the bilge pumps being without power while I'm away gives me pause. Not that the boat is taking on any water but I figure that would guarantee it would start to

Plus I'd prefer something more definitive than a "general indication"
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Old 09-20-2015, 03:27 PM   #7
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Sounds like these are start batts, not deep cycle batts. All deep cycle batteries I'm familiar with are rated in AH, not CCA. All start batteries I'm familiar with are rated in CCA, not AH.
All I know is they are heavy duty commercial batteries...maybe MF stands for multi function...will ask Deka tomorrow. Maybe they are not even the best choice for the boat...just what previous owner happened to put in there. My sense is just looking at them they are probably over 5 years old. They have no corrosion on the terminals or elsewhere, but are dirty enough on top I can't imagine them being very recent considering how clean the engine room is.
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Old 09-20-2015, 03:58 PM   #8
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I'm posting here to stay in the loop... in case a fast way for checking individual batt's condition in a House Bank gets posted.

Our HB has four (they call em - maintenance free??) East Penn 31 deep cycle batts. Strip back the sticker and there are screw plugs for distilled water servicing/topping-off. 7 yrs old since installation; needed to top off twice so far - I don't let them get below 50% charge. All four HB batts seem to still be going strong. I have a multi meter wired into the bank and sitting on top of 2/3 high master bedroom closet... for checking when desired. I use the HB too for engine starting of our twins. 7.5 Kohler gen set has it's own 27 starter batt; it is charged by gen's charger and trickle from solar panel on fly bridge front. I keep a totally isolated 27 starter batt in black batt box at constant 100% charge... just in case all else fails. Also have commercial jumper cables if needed.

PS: See post 372 - Your Best Technique or Invention

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Old 09-20-2015, 05:45 PM   #9
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I'm posting here to stay in the loop... in case a fast way for checking individual batt's condition in a House Bank gets posted.

Our HB has four (they call em - maintenance free??) East Penn 31 deep cycle batts. Strip back the sticker and there are screw plugs for distilled water servicing/topping-off. 7 yrs old since installation; needed to top off twice so far - I don't let them get below 50% charge. All four HB batts seem to still be going strong. I have a multi meter wired into the bank and sitting on top of 2/3 high master bedroom closet... for checking when desired. I use the HB too for engine starting of our twins. 7.5 Kohler gen set has it's own 27 starter batt; it is charged by gen's charger and trickle from solar panel on fly bridge front. I keep a totally isolated 27 starter batt in black batt box at constant 100% charge... just in case all else fails. Also have commercial jumper cables if needed.

PS: See post 372 - Your Best Technique or Invention

From another forum I'm getting word the below Snap On unit may be the cat's meow....

https://store.snapon.com/Electronic-...d-P823712.aspx

There is a less expensive version of this ($229) but it only tests 12 volt batteries. Although my current need is for 12 volt only I can see the need of 6 and 24 volts in the future. I think my bow thruster uses two 6 volt batteries and the 24 would come in handy for electric pallet jacks at my shop.
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Old 09-20-2015, 07:33 PM   #10
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From another forum I'm getting word the below Snap On unit may be the cat's meow....

https://store.snapon.com/Electronic-...d-P823712.aspx

There is a less expensive version of this ($229) but it only tests 12 volt batteries. Although my current need is for 12 volt only I can see the need of 6 and 24 volts in the future. I think my bow thruster uses two 6 volt batteries and the 24 would come in handy for electric pallet jacks at my shop.
Cala -TY for posting. I punched-up link contents. Did a fast review; didn't notice if/where/how/when this tester could pinpoint a specific batt in a bank bank that is getting weak or failing... did you??? Plan to call mfg/sales for questions.
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Old 09-20-2015, 11:04 PM   #11
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Here is my experience with battery load testing. When I was diving seriously and I had to know with certainty that my electric scooter batteries would carry me a given distance, I would set up a load test. I had put together some large resistors, I think they were Around 3 ohms, a pair of them. I would hook up the load to a pair of 12v batts in series and time them until they hit 20 volts. I'd do this to a new pair and before any dive I could not afford to not get a predictable run time. The resistors simulated pretty closely the burn time of actual use. I had the resistor bank in a mount well clear of anything else as they would get hot enough to be hazardous while babysitting them for over an hour. They would heat my shop.

Now, those batts were 17 amp hour. The house bank on my boat is around 1200 amp hours. I could not even imagine safely setting up a resistive load for such a thing. You could set up space heaters, but as the room warms they are not going to run continuously, and for how long?

In short, it's not a practical solution.

Get a good amp hour counter and keep a log of resting battery voltages at typical amp hour counts. It gets pretty clear over time as the capacity starts to shrink.

As noted, if this is a starting batt, you don't need a timed load test. You can simply measure amps during cranking. I've never had to do that, just listen for the starter pitch.
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Old 09-21-2015, 01:47 AM   #12
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First let me say I only test start batteries at work. The electronic testers are wrong about 1/3 of the time we test batteries. The "toaster" testers with a carbon pile are never wrong. No matter what size the battery (start battery remember) when you suck 500 amps out the voltage drop gives you the answer. So, I don't know if my results are typical or not and I don't know that electronic testers might not work perfectly on a deep cycle battery but I know I would not spend the money on one for myself.
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Old 09-21-2015, 06:47 AM   #13
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The best testers for deep cycle batts are at the golf cart shop.

These will test the batts , charged or not and allow a decision to be made.

About $400 or so last time I looked.
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Old 09-21-2015, 11:57 AM   #14
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How about pull one of the batteries and take it to a shop for a load test?
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Old 09-21-2015, 12:05 PM   #15
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How about pull one of the batteries and take it to a shop for a load test?
There are 12 batteries at over 60 lbs each...only one of the 12 is likely to fail a test but I don't know which one. In other words...not a practical idea just from a physical hassle standpoint.
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Old 09-21-2015, 12:32 PM   #16
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First let me say I only test start batteries at work. The electronic testers are wrong about 1/3 of the time we test batteries. The "toaster" testers with a carbon pile are never wrong. No matter what size the battery (start battery remember) when you suck 500 amps out the voltage drop gives you the answer. So, I don't know if my results are typical or not and I don't know that electronic testers might not work perfectly on a deep cycle battery but I know I would not spend the money on one for myself.
Interesting.... can you elaborate on the "1/3 wrong" part ? Do you mean they sometimes show batteries as ok that in reality need replacement ? Or the opposite ? Or could go either way ?

And are they WAY off....or just a little off.... or you never know ?
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Old 09-21-2015, 12:34 PM   #17
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Cala -TY for posting. I punched-up link contents. Did a fast review; didn't notice if/where/how/when this tester could pinpoint a specific batt in a bank bank that is getting weak or failing... did you??? Plan to call mfg/sales for questions.
Re finding specific weak battery.... I just assumed that was impossible, and each battery would need to be disconnected from the bank and checked individually.

Although I know from experience if a battery in a bank is really in bad condition you can feel it overheating compared to the rest, during charging.
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Old 09-22-2015, 12:10 AM   #18
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Re finding specific weak battery.... I just assumed that was impossible, and each battery would need to be disconnected from the bank and checked individually.

Although I know from experience if a battery in a bank is really in bad condition you can feel it overheating compared to the rest, during charging.
Thanks for the suggestion... but...I usually don't contort into position to feel my individual house bank batts' temps

Do wish there were an affordable way to tell each batts condition without too much trouble.
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Old 09-22-2015, 06:36 AM   #19
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"Do wish there were an affordable way to tell each batts condition without too much trouble"

Hydrometer , get the temp measuring style.

Charge all the batts overnight , disconect them from each other (good time to clean the cable ends), wait a day or two and measure the SG of each.

The problem is even after you find it sticking a new bat in with a bunch of old ones is never good.

Perhaps its time to re do the entire start - house setup.

NO strings longer than 4 batts.
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Old 09-22-2015, 08:55 AM   #20
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Our house bank of 4 deep cycle, wet cell 31's has been doing fine for 6+ yrs. I've multi meter hooked up in master state room for an anytime reading of charge level of the pack. Don't let them drop below 50%. Always recharge to 100%+. Keep distilled water at correct level. Simple is as simple does!


The multi meter lets me instantly know what level of charge amps are being put into HB of batts by the boat's charger while on dock or from gen set power or from starboard engine's alternator. Also lets me know what level of draw is happening while using various DC components aboard boat. Our HB is used to start engines too. Gen set has independent 27 starter batt held at 100% by solar panel and GC's own alternator when its running. For redundancy (pretty much fail-proof safety)...keep a 100% charged 27 starter batt in an isolated black box... just incase!!
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