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Forum Index : Solar : Can you get a bad batch of batteries?
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
About 4 months ago I purchased a new set of 8 Crown 235Ah 6v batteries to replace my 5 year old's. I installed them, topped up the water to the indicator mark, and put them into service. I've used Crown batteries in the past with no issues, other than I overcharged them once, but they are still OK as a backup bank. A week after installing the new batteries I went to check the specific gravity's at the end of the day and found them on the low side, and uneven between batteries. The gravity's were around 1.23 to 1.26, but voltages were even at around 6.3v per battery bank, 50.4 for the bank. I notified the supplier, and continued monitoring for the next few months. Things have not improved, and I'll take some readings this afternoon to confirm, but I suspect they are worse. I checked 3 cells yesterday afternoon and they were around 1.21. Voltages are still OK, all batteries within 0.02 volts of eachother. A couple of mornings ago I checked the battery bank at 5:30am and it was sitting at 47.4v! That night I had drawn about 2.5kWh, which would be around 20% of the battery bank capacity. The other thing I've noticed is the batteries have used very little water since new, about 3mm drop in level. Charging voltages are all to spec, and charging current limited to 30 amps. They reach boost voltage by 9am usually, then sit at absorb for a couple of hours and then float for the rest of the day. I've run a couple equalizing cycles at 61 volts to try and stir them up a bit but didn't make any difference, the batteries didn't even get warm. So I suspect I have a bad batch of batteries, but how likely is this? One or two bad batteries I can understand, but a whole bank? Could it be a bad mix of acid that was used for the whole bank? Has anyone ever had a similar situation? Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Boppa Guru  Joined: 08/11/2016 Location: AustraliaPosts: 814 |
Quite possible the acid was badly mixed I dont know if they are still 'dry transported' ie no acid in them That was one of my jobs as an apprentice many years ago, filling the batterys at the railways We got the acid in 20l drums, then diluted it 1:10 with water before filling the batterys up We were supposed to get acid proof overalls- never did mind you, so we used to shop at the charity shop for dollar teeshirts and pants-after a single day the acid fumes in the battery room would literally leave your clothes like tissue paper, slightest touch and they would tear... least we got double filter respirators to breathe with... maybe if they still did it, someone didnt measure the acid/water amounts correctly? |
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yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
Battery acid usually comes in 3 versions. SG 1.84 99% SG 1.40 50% SG 1.22 to 1.29 30% to 38% premixed for the batteries specific application the old dry uncharged Exide traction batteries used to be filled with SG 1.25 33% or SG 1.26 34.5% then we charged them and we would use 50% concentration and distilled water to adjust them to hit the target fully charged of SG 1.285 (after a good gassing and temp adjustment) SG 1.23 is down in backup battery territory where cells are left on float for months at a time and plate corrosion is a factor. SG 1.26 is correct for some stationary batteries. it is possible to get a dodgy reading on specific gravity with a puny hydrometer with a small chamber and short hose even with good mixing technique on some cells, particularly those with a baffle and large amounts of acid above the plates. its also possible to have a high resistance connection somewhere in the pack or wiring that can play hell with charging. The only reliable way I have found to track this down is looking for hot spots under very heavy load. Thermal imaging helps but its not foolproof. I dont have a problem with adjusting the acid concentration on new cells if I am satisfied I have eliminated the two things listed above and I have vigorously gassed all the cells. cheers I'm confused, no wait... maybe I'm not... |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
I have seen batteries I suspect were accidentally filled with water get a skin on the plates and not take a charge. I probably could have saved them but they got replaced under warranty and it wasn't one of mine so I was happy to not get involved. I'm confused, no wait... maybe I'm not... |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
I've done a couple of 1000W load tests looking for weak cells, but battery voltages all pretty even. Ill do another test tonight and in the morning. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
Crown users guide says the battery spec for specific gravity is 1.270 Reading between the lines you could probably expect a SG of 1.275+ @ 2.45 volts per cell with a newish battery. edit A fault is going to be pretty bad to show up as a voltage drop at 1000W. At 3.5 kw you might only see 0.1 volts difference if only one cell is affected. I'm confused, no wait... maybe I'm not... |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Nice find Yahoo, I looked everywhere for that data. Figures today are sad. This is at the end of a sunny day, normal charging cycle. There are 3 columns below, the first was taken at 7am a month ago. The 2nd was 5pm that afternoon. The 3rd was taken today. It appears they are getting worse.  Thoughts? Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
in my opinion there is 14 cells that have acid concentrations that are 15% to 21% lower than where they should be. There is only five cells that are even close to reasonable specific gravity. the h2so4 concentration should be close to 36.5% SG 1.2775 I can see a couple that are at 28% I have never seen that much variation in new cells. They have either plated the sulphate out due to some sort of contamination or the cells were partially filled with acid and topped up with water. I would not be persevering with them. I'm confused, no wait... maybe I'm not... |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Thanks Yahoo I'm going to give them a few equalizing cycles, see if it makes any difference. Voltages are OK, and this morning before the sun was up I plugged in a 1200watt heater for 10 minutes and measured between 5.7 and 5.8 volts on all batteries, holding nicely. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
I really think your charging regime is too conservative.... traction packs are designed to cop a flogging both in and out. I can't help but feel your idea of eq is a good one. Far more batteries have died because the owners have been too conservative, as against being over charged to death. Provided there is plenty of water in them, and the temp stays reasonable, it is very difficult to cause much mayhem by more charge than less.... less is death to FLA.... and stratification is every bit as bad...... a good steady boiling is in order I think. I am talking of a cycling bank... a back up/floating bank is totally different, and erosion can become prevalent... but a cycling bank is unlikely to get that for more than a few hours..... very unlikely to damage the plates from that. .......oztules Village idiot...or... just another hack out of his depth |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
An update on the batteries. I contacted the local supplier about my concerns, sent a copy of my logs, and was advised to "charge the batteries at 20 amps for 20 hours"! Now I knew a constant 20 amps for 20 hours would effectively cook the battery bank and take years off its life, if not stuff them within days, so I didnt take the action and put the problem on hold for a few weeks, I had a business trip to Mackay I needed to prepare for and other more pressing problems. On the morning I was to leave for the 11 hour drive to Mackay, I turned on the kettle, and the power tripped out. Walked down to the shed, and the inverter was beeping, and battery voltage was 44v, unloaded. No unusual load overnight, normal sunny day the day before. One battery was down to just under 4 volts, the others less than 6 volts. Seams like one cell died the day before and the rest of the bank didn't charge properly as a result. I swapped the dead battery for a 6 year old spare, and waited around for an hour to make sure the bank was charging properly. I eventually left Toowoomba about 10:30am, got into Mackay about 9:30 that night. Contacted the supplier, and was advised I still needed to do the 20 amps at 20 hours. So I contacted the manufacturer, Crown, in the USA. I told them I was advised by the local supplier to charge at 20 amps for 20 hours, was this OK? They replied within a day, and the reply basically said 20 amps for 20 hours would be a bad idea, and then went into charging routines, etc, etc, it was very comprehensive. I replied to them with more of the bank history, serial numbers and my log files, below.  Crown got back to me and said they were going to replace the whole battery bank  They even offered to deliver them, but I decided it would be better if I pick them up so I could test them before loading them into my car.So hats off to Crown.  Now I have a quick question. The supplier has advised they have the new bank charged ( hopefully not at 20 amps for 20 hours ), and ready to be picked up. I wanted to check the voltages and gravity's before I load them into my car, its a 300km round trip and I dont want to get home and find one battery is way off spec. What would be a acceptable range of gravity's for a new bank of batteries? Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
I think that they should be at least 1.2775 but that is anecdotal, you need someone with a set of crowns to confirm that they read 1.28+ when new. I would be checking their acid premix SG if the numbers are low SG to %h2so4 tables conversion table pdf this helps me as I tend to think an calculate in % concentration rather than specific gravity. I'm confused, no wait... maybe I'm not... |
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Madness Guru Joined: 08/10/2011 Location: AustraliaPosts: 2498 |
Maybe this is what happened with the first lot. There are only 10 types of people in the world: those who understand binary, and those who don't. |
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| Phil23 Guru Joined: 27/03/2016 Location: AustraliaPosts: 1664 |
Absolutely Excellent Service PR. Best and cheapest advertising a company can do. It never ceases to amaze me how some companies choose to bicker & skimp when it comes to warranty etc, & ultimately customer relations. Phil. |
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