Die Hard deep-cycle batterys 27M 29M 50%?

[liveaboardL]

I've been using these Diehard deepcycle lead-acid batterys I got for 30% off at Sears. K-mart also sells them. Seemed like a bargain, but I wonder if they were discounted because they were old & lost some sort of capacity.

I've read that a deep-cycle lead-acid battery shouldn't be discharged below 50%. The best way to see if the battery is at 50% is with a good quality hygrometer, but if you don't have one, you can use your voltage read-out with a multimeter to see if you're at 50%.

That's where my question comes in. What voltage should a Die-Hard deep-cycle lead-acid 27M battery read out using a digital multimeter to indicate that the battery is at 50%?

I read a chart that says it's at 50% when the voltage reads 12.25 volts, but this seem to be only after the battery has been resting, unused, for about 30 minutes. Because I can start with a full battery and discharge it with a 100 watt load for about 15 minutes before my GPS volt display says it's at 12.2. That's not very long.

This morning I'm going to experiment & run it down to 12.0 & see how much the voltage climbs back up after 30 minutes. So far it's been going for 1 hours 10 mins w/ the wind-generator helping and it just started remaining stable at 12.0 volts according to the GPS voltage indicator.

Now I'll disconnect it & see if it climbs back up to 12.2 when unused & I'll turn the charger off.

Has anyone already figured all this out with the Die-Hard lead aci 27m or 29M battery brand?

[liveaboardL]

So after about 30 mins, w/ everything off, the battery reads out 12.46 volts according to the digital multimeter, which is 62% charged.

It looks like I can take the battery even lower than 12.0 volts, under a 100 watt load, next time I run this test.

There's very little info available on the Die-Hard brand battery in particular. I've been very careful with them so far. I've had them for about 2 months.

• Amp Hours at 20 Hour Rate:
  105
• Cold Cranking Amps (CCA at 0 deg.F):
  575
• Reserve Capacity (RC):
  180 min.

So, 105 amp hours? Lets see. The inverter & laptop power supply draw bout 100 watts, which is 8.3 amps. Running for 1.1 hours, costs about 8.5 amps or so.

So if the battery has 105 amp hours and I take it to 65%, it should be at 68 amp hours, a difference of 37 amps.

I should have had 37 amps available to get to 65%. Instead, I only drawed 8.5 amps.

Something's not right w/ my setup. Either the batteries aren't good, or there's a load I don't know about that's taking up way too much juice, or there's a short somewhere. I turned the power off at the big red knob, but that's another problem w/ this boat's setup, cause even after I turn that knob off, some things still have power. I need to put in a real power disconnect switch. Or maybe it's just Die-Hard batterys, or DSH.

[denverd0n]

Originally Posted by liveaboardL

...this seem to be only after the battery has been resting, unused, for about 30 minutes.

No, 30 minutes is really not long enough. If you want a reasonably accurate measure of how full your battery is you need to let it rest for 10-12 hours at least.

But all lead-acid batteries are going to be the same, in terms of the voltage and depth of discharge. The brand doesn't matter, and the size doesn't matter. The only thing that matters is different types of batteries, like AGM, Gel, and so on.

[noelex 77]

As others have said the batteries need to rest longer to get a relevant "resting" battery voltage. 24 hours, or more. Even with a resting battery voltage you need to make a compensation for temperature and the measurments needs to made with a calibrated multimeter.

It is difficult to accuratly concclude the relevant SOC from voltage alone.

There are also some other factors that need to be considered:

Did you charge to100%? This takes a long time and a good quality charger.

You are discharging higher than the 20hr rate. This decreases the capacity of the battery

8.3A is a high draw for a laptop have you measured this?. If it is correct 8.3x1.1= 9.1AHrs

[ontherocks83]

As a guideline (this is a rough guideline, ambient temp will effect this) resting voltage of 12.7 is fully charged and 12.2 is 50%. You should try not to let it drop past 12.2 volts before recharging to 100%.

What type of charger do you have? Charging to 100% can take a long time. You should get up to roughly 80% in a few hours but the last 20% can take a while.

To give you "ball park" numbers 1 group 27 battery should have 96ah which means you get to use half of that. Theoretically you should be able to use 48ah per battery before being at 12.2 volts. Again these are rough numbers and can vary but should at least give you a guideline.

Check your water level and fill with distilled water if needed. Bring to 100% charge and test from there. If you are Positive that you have exactly a 100 amp draw you should get between 5-6 hours of draw before getting to 12.2 volts. If you have 2 batts in parallel double that to 10-11 hours.

[liveaboardL]

It uses a Blue Sea Systems charger. The wind was blowing & it was charging all night. It got to the point where the wind-mill kept jolting to a stop. You can hear it in the night. It does that when it gets near 14.5 to 15+ volts or higher for too long. I assumed it was charged, but next time I'll let it rest & make a note of the voltage.

If I don't let it drop below 12.2, I'm not going to get much usable juice from it. My laptop's battery can go from 7 to 15 minutes of charge with the inverter plugged in, before the die-hard deep cycle hits 12.2 volts.

My multi-meters abilty to read amperage always quits working after a few weeks. I don't know if I'm overloading it. They should have a fuse to prevent them from being damaged, but I cannot measure how many amps it's pulling.
The adapter says:
input: 1.3 amps (assume 120 volts)
output: 2.37 amps @ 19 volts
The Die-Hard inverter doesn't list anywhere how efficient it is, but often those cheap 120 watt inverters are rated at 15% maximum efficiency & I've read somewhere that they are often 60% efficient. Maybe it's drawing more than I thought. One of the metal connection tabs did melt off! Cheap K-mart Die-hard junk. I'd really love to know what it's drawing. It's a very small laptop adapter & I chose it cause I thought it might draw less power overall, but now... I have to wonder.

[ontherocks83]

If it drops below 12.2 that quick then it sounds like the battery is junk. Obviously we need some more concrete evidence and tests to condemn it but it doesn't sound good.

Again dropping below 12.2 consistently is causing damage. If you get new batteries try to refrain from doing that. Also leaving a battery in a discharged state for long periods is also not good for it.

I dont remember where I read it but there was a great quote along the lines of.... batteries want to age gracefully and live a long useful life but unfortunately the vast majority of them are brutally murdered through neglect and abuse.

[liveaboardL]

I've never had numbers like those. No where near that many amp-hours. Even w/ the 29M battery I've never been able to run the 7-watt LED bulb for more than 3 hours. It's as if I have a smart-drain on my system. It will drain the batteries to near 50% charge & stop. I can never charge any of the batteries for long. The GPS draws 1/4 amp w/ the sonar turned off. I have nothing that I know of drawing power escept the GPS, occasionally a 7-watt bulb, the radio is usually off although it has a flashing blue LED, and I charge my laptop while I can before the battery reads too low.

I think it's just the Die-Hard batteries. I think they were on sale cause they got stale sitting in the current economy (sorry, but it's true) & I was sold batteries that are worn out.

[Maine Sail]

Originally Posted by liveaboardL

It uses a Blue Sea Systems charger. The wind was blowing & it was charging all night. It got to the point where the wind-mill kept jolting to a stop. You can hear it in the night. It does that when it gets near 14.5 to 15+ volts or higher for too long. I assumed it was charged, but next time I'll let it rest & make a note of the voltage.

If you are pushing above say 14.6V on a regular basis you need better voltage regulation. You have perhaps cooked your batts if you regularly hit 15V..

Originally Posted by liveaboardL

If I don't let it drop below 12.2, I'm not going to get much usable juice from it. My laptop's battery can go from 7 to 15 minutes of charge with the inverter plugged in, before the die-hard deep cycle hits 12.2 volts.

A "loaded" voltage reading is pretty useless unless you know exactly what it means at the particular SOC, load & temp. That said it does sound as if your batts are pretty toasted, not getting charged properly or the batteries are physically cold when you are applying this load..

[liveaboardL]

Dropping below 12.2 causes damage, BUT, if I drop it to 12.0 & get a good hour's of laptop charging out of it, and shortly after I unplug the inverter, the voltage reading jumps right up to 12.3, did it still cause damage?

I read that even using a microwave w/ deep-cycle batteries can quickly bring the charge down to 11.8 in a few minutes, but that doesn't mean damage has been done to the batteries. Cause when you take the load off, it's above 50%. Right?

I totally concur that my batteries are probably worthless due to Sears having stored them & not maintained them for too long. That's probably why they were on sale, but I cannot prove this. The batteries were always like this from day 1. I've only owned them 2 months.

[liveaboardL]

It was a very cold day! High of 44, Lows in the 30's.
If the charge gets too high, the charger turns off the wind-gen for a few minutes, & then lets it run for 1 minute, repeatedly. It's an expensive unit. The batteries were like this from day 1.

[Maine Sail]

Originally Posted by liveaboardL

Dropping below 12.2 causes damage, BUT, if I drop it to 12.0 & get a good hour's of laptop charging out of it, and shortly after I unplug the inverter, the voltage reading jumps right up to 12.3, did it still cause damage?

I read that even using a microwave w/ deep-cycle batteries can quickly bring the charge down to 11.8 in a few minutes, but that doesn't mean damage has been done to the batteries. Cause when you take the load off, it's above 50%. Right?

I totally concur that my batteries are probably worthless due to Sears having stored them & not maintained them for too long. That's probably why they were on sale, but I cannot prove this. The batteries were always like this from day 1. I've only owned them 2 months.

Don't write them off yet. Cold weather performance will not be the same as when the batt is in the 70's. Your batteries should not be getting to any more than 14.6V during charging unless you are purposely equalizing them. You really need to address that.

In cold weather resting or rebound voltages for accurate SOC can take FAR LONGER than 24 hours...

Don't judge your batts based on how they hold voltage in the low 40's.. You will have less capacity when cold but you need to determine how much less by allowing them to rest with no load or charge for a long while when cold.

I have a Deka G27 (your Die Hard is a Deka/East Penn battery) I took off charge two weeks ago and it is still reading 12.89V due to the temps...

Again the "loaded" voltage is meaningless and dipping below 12.2 loaded is not harming them unless the actual SOC is actually there too, which it is not if you are at 12.2 loaded at 40F..

[liveaboardL]

I talked to Brett, the manager of the Automotive center of Sears here, and he said that he would have to test the battery and it would have to show up as having failed the test before allowing it to be refunded or exchanged.
He said they would have to charge it & then test it.
I brought up the issue of batteries showing false positive tests immediately after a charge, and he agreed to wait an hour or however long I wanted after charging it to let the resting-voltage stabilize, before running it through the testing device.
Naturally, I wasn't offered a ride. It's 13 miles to Sears from the river.
I really don't want to wait 2 or 3 hours at Sears to get these batteries refunded. I have a full 1-year warranty on paper.
I've read from other people who had the same problem that they will often require that a car's alternator be tested before refunding. One boat owner said that they wanted him to bring his 45' boat in to be test before they would refund the money.
Actually, there were a lot of complaints about people who've bought bad batteries from Sears.
Brett didn't say anything about requiring an alternator test & I didn't ask.

I told him that the battery is opperating at 60% capacity only less than 3 months old, and it should be at 90% capacity. I told him its never worked well, right from the start, but I held on to it in hopes that it would perform better after it warmed up. It's warm now. It hasn't improved.

I'm considering converting it to an alkalyne battery using cooking alum in each cell. There are a lot of reports from people who've tried it, but rarely do they offer long-term results, which I find disturbing. Lil red flag.

Also, it seems like you can run a Alum-converted 12-volt Lead-Acid battery down to 0 volts without damaging the battery, unlike the normal LAB, but, very few of the tests are using deep-cycle systems and only 1 actually gave out some real-world usage #s. His #s indicated that the battery was rated for about 60 amp hours, and put out about 25 amp hours of work before ending up at a 11.2 volt resting state.
My inverts cutoff point is 11.5. Hrm... It would be nice to actually be able to use maybe 40% of the batteries amp-hour capacity instead of the 10% available to me now from Sear's 30% off brand-new Die-limp deep-cycle battery.

Sears probably just let it sit on the shelf for a few years & never bothered to give it a maintenance charge, creating a sulfation layer, ruining the battery. If only Sears had some sort of maintenance charging routine schedule. In the old days, when they didn't stay on the shelf so long, they could probably get away w/ not maintaining it, but Sear's ain't Walmart. Point in case, I don't care how discounted the batteries are, don't buy Die-Hard deep cycles unless you're happy with 10% of the battery's reserve capacity after having it charged to 99%.
Ideally, 40% of a brand-new battery's reserve capacity should at least be available, but this one has 10%. This makes a great case for trying the alum, doesn't it? What do I have to lose? Sulphation is supposed to actually make alum-converted LA batteries work better!

[btrayfors]

Congratulations for trying to figure all this out, and making the calculations. This indicates to me a healthy interest which can, in time, be converted to real knowledge.

There are only two accurate ways to measure the capacity of a flooded battery:

1. The best way is a 20-hour test. You disconnect the battery in question, then fully charge it (@ 14.6-14.8VDC absorption, then 13.6-13.8VDC for many hours...at least overnite). When you are sure it's fully charged, you put a C/20 load on it and measure the time before it reaches 10.5VDC. In your case, a C/20 load would be 105/20 = 5.25 amps.

2. The next best way, much easier and quite reliable, is to use a sophisticated conductance/impedence tester like the Midtronics series. This can be done while the battery is connected and at any state of charge (SOC). It takes only seconds to give you a pretty good reading of the capacity of the battery being tested. Downside: these testers cost $600 or more. See if you can find someone with such a tester. Where are you located?

Note that what you've been trying to do -- estimate SOC by resting battery voltage -- can be a reasonably accurate way provided that you do it right. The resting voltage as measured when the battery has been sitting with no charge and no load for at least 24 hours...will tell you the present SOC, e.g., 12.2 volts equals approximately 50% SOC.

However, SOC in itself tells you NOTHING about the capacity of the battery. To measure capacity, you must do a controlled full charge then fixed load testing, preferably at the 20-hour rate.

One thing you might do before testing: give the battery a good equalization treatment: first fully charge it, then equalize it with 15.5VDC for 4-6 hours. That can help to knock off some of the lead-sulfate crystals (PbSO4) from the plates, stir up the electrolyte, and regain some capacity.

Bill