cereal tiller Posted January 19, 2017 Report Share Posted January 19, 2017 bummer! let us know how you get on with the return. Will you try another or ask for refund? I hope to test mine next week. Was contacted by the Vendor and offered a replacement or Refund,I chose the refund The refund was credited to my Paypal account this morning No request for PSU unit to be returned CT Link to comment Share on other sites More sharing options...
MtB Posted January 19, 2017 Author Report Share Posted January 19, 2017 Was contacted by the Vendor and offered a replacement or Refund,I chose the refund The refund was credited to my Paypal account this morning No request for PSU unit to be returned CT That's very honourable of them. Which one are you going to buy next? Or are you planning to pull the dead one apart and identify/replace the part that burned out? Link to comment Share on other sites More sharing options...
cereal tiller Posted January 19, 2017 Report Share Posted January 19, 2017 That's very honourable of them. Which one are you going to buy next? Or are you planning to pull the dead one apart and identify/replace the part that burned out? You are guessing well Michael CT Link to comment Share on other sites More sharing options...
MtB Posted January 19, 2017 Author Report Share Posted January 19, 2017 (edited) A brief update on mine equalising saga. I gave the bank another good equalising at the weekend using the Sterling charger and could not get the low cell any higher than the exact same value as last time, 2.266. I gave the bank a further 45 mins of equalising at 32.0V using the buck converter before the donkey battery set died, during which the low cell subsided to 2.265. (Probably measuring error.) I've ordered another buck converter that steps down so I can equalise one singe battery at a time from the donkey set. When that arrives I'll have one more go at the battery with the dud cell then if still no success, I'll replace it. Edited January 19, 2017 by Mike the Boilerman Link to comment Share on other sites More sharing options...
dmr Posted January 19, 2017 Report Share Posted January 19, 2017 Don't wait too long as the other cells will be getting harder sulphate as I assume the bad cell is preventing the others from getting to full charge. I had something similar a few years ago with my first set of Trojans, it wasn't a shorted cell, it was a single cell that just wouldn't charge. I think someone came up with a plausible theory when I posted but dunno how I could find that thread. The failure was probably after 800 cycles or thereabouts so I was not too upset about paying for replacements. However the other pair from the original 4 are still going now, though their days are numbered. It also sounds like Tom and Bex (I think) are having a similar issue on another thread...we currently have two separate equalisation threads running, arn't batris excitin! .............Dave. Link to comment Share on other sites More sharing options...
mross Posted January 19, 2017 Report Share Posted January 19, 2017 What have Trojan batteries got in common with Trojan condoms? They both carry a load? Link to comment Share on other sites More sharing options...
cuthound Posted January 19, 2017 Report Share Posted January 19, 2017 Yup, defiantly sounds like a battery with a dud cell. Nothing to do but ask for ask replacement. Link to comment Share on other sites More sharing options...
MtB Posted January 19, 2017 Author Report Share Posted January 19, 2017 Don't wait too long as the other cells will be getting harder sulphate as I assume the bad cell is preventing the others from getting to full charge. I don't really understand this, given all 12 cells are in series (24v bank). So when charging and equalising all cells are carrying the same current, so I don't get how one cell failing to charge can prevent the others charging, given they have a charge current of 30a flowing through them. 1 Link to comment Share on other sites More sharing options...
mross Posted January 19, 2017 Report Share Posted January 19, 2017 Aren't they in series-parallel? Link to comment Share on other sites More sharing options...
bizzard Posted January 19, 2017 Report Share Posted January 19, 2017 (edited) We've been done! The beauty of the the old batteries with exposed cell links on top was that you could isolate a dead or dead cells by sawing links out and re-linking to make various voltages from a 12v battery. 2, 4, 6, 8 or 10v, by just drilling and tapping for terminals on the selected links, very useful especially 6v. I used to do this with customers old 12v batteries for my first car which was a 1936 Ford Y type, 6v. Edited January 19, 2017 by bizzard Link to comment Share on other sites More sharing options...
bizzard Posted January 19, 2017 Report Share Posted January 19, 2017 (edited) We've been done! The beauty of the the old batteries with exposed cell links on top was that you could isolate a dead or dead cells by sawing links out and re-linking to make various voltages from a 12v battery. 2, 4, 6, 8 or 10v, by just drilling and tapping for terminals on the selected links, very useful especially 6v. I used to do this with customers old 12v batteries for my first car which was a 1936 Ford Y type, 6v. I also did this for my dads 1939 Standard flying 10, also 6v. We never bought a battery, just a bit of alteration to the carriers. And for his 6v 1936 Royal Enfield 500 combination. I mounted the down-rated 12v battery on a dexion frame between the bike and side car. Edited January 19, 2017 by bizzard Link to comment Share on other sites More sharing options...
MtB Posted January 19, 2017 Author Report Share Posted January 19, 2017 (edited) . Edited January 19, 2017 by Mike the Boilerman Link to comment Share on other sites More sharing options...
tosher Posted January 19, 2017 Report Share Posted January 19, 2017 A quick question please --- Am I right in thinking that the tail current of a fully charged battery should be approx 1 to 2 percent of the current capacity of the battery and not the capacity of the battery when new?? Link to comment Share on other sites More sharing options...
MtB Posted January 19, 2017 Author Report Share Posted January 19, 2017 A quick question please --- Am I right in thinking that the tail current of a fully charged battery should be approx 1 to 2 percent of the current capacity of the battery and not the capacity of the battery when new?? Generally yes, although it can be higher on an old, well used battery. The tail current is really the current once it stabilises and stops falling. (Which can be 4%, 2%, 1% or 0.25%, depending on your patience.) Link to comment Share on other sites More sharing options...
WotEver Posted January 20, 2017 Report Share Posted January 20, 2017 As Mike says, whilst aiming for a low percentage, the most practical and economical point to stop charging is when the charge current has stopped reducing over a 45 minute period or thereabouts. Link to comment Share on other sites More sharing options...
tosher Posted January 20, 2017 Report Share Posted January 20, 2017 Thanks Mike & WotEver. Mine stabilse at about 12 amps. They were 810a/h when new but I recon they are down to about 400a/h now so the tail current is in the right ball park. Link to comment Share on other sites More sharing options...
MtB Posted January 20, 2017 Author Report Share Posted January 20, 2017 (edited) Don't wait too long as the other cells will be getting harder sulphate as I assume the bad cell is preventing the others from getting to full charge. But sir, what is the mechanism by which this can happen when all the cells are in series? The charge current in all of them must be the same, so how can one cell prevent others from charging (when there is a hefty charge current flowing through the lot of them? While the dud cell only gets up to 1.266, the cell at the opposite end of the same battery goes up to 1.278. during equalising. Edited January 20, 2017 by Mike the Boilerman Link to comment Share on other sites More sharing options...
dmr Posted January 20, 2017 Report Share Posted January 20, 2017 But sir, what is the mechanism by which this can happen when all the cells are in series? The charge current in all of them must be the same, so how can one cell prevent others from charging (when there is a hefty charge current flowing through the lot of them? While the dud cell only gets up to 1.266, the cell at the opposite end of the same battery goes up to 1.278. during equalising. Right, I've not been paying full attention cus Im on holiday, I did not realise that you had got the other cells right up to 1.278. The problem is the same one that gives the "wisdom" that if you mix old and new batteries the new ones will be pulled down to the capacity of the old ones, and this is true with batteries in series. During normal charge the current will reduce once the weakest cell has taken its full charge so the others will never get their full charge. However I am not 100% sure this was true when I had my strange cell. In your case you are equalising so likely will get the other cells up to full charge, indeed surely this is what equalising is all about?? I suspect once you revert to normal charge the sg of the other cells will rapidly fall....but you can test this and replace hypothesis with facts. .............Dave Link to comment Share on other sites More sharing options...
ditchcrawler Posted January 20, 2017 Report Share Posted January 20, 2017 But sir, what is the mechanism by which this can happen when all the cells are in series? The charge current in all of them must be the same, so how can one cell prevent others from charging (when there is a hefty charge current flowing through the lot of them? While the dud cell only gets up to 1.266, the cell at the opposite end of the same battery goes up to 1.278. during equalising. The current through your series cells will be the same for each cell, but the voltage across them will be different depending on the cell condition, if one was short curcuit it would still have 5 amps going through it but the voltage across it would be zero. Link to comment Share on other sites More sharing options...
WotEver Posted January 20, 2017 Report Share Posted January 20, 2017 Thanks Mike & WotEver. Mine stabilse at about 12 amps. They were 810a/h when new but I recon they are down to about 400a/h now so the tail current is in the right ball park. Try giving them a good long (3 hrs) equalise at 16V or thereabouts. Link to comment Share on other sites More sharing options...
MtB Posted January 20, 2017 Author Report Share Posted January 20, 2017 Try giving them a good long (3 hrs) equalise at 16V or thereabouts. Well that's the problem! Where do I get 32.0v from? (24v bank) I suppose I could equalise 3 in series at 24v... Link to comment Share on other sites More sharing options...
WotEver Posted January 20, 2017 Report Share Posted January 20, 2017 Well that's the problem! Where do I get 32.0v from? (24v bank) I suppose I could equalise 3 in series at 24v... Do 'em two at a time at 16V, or indeed 3 at 24V. Link to comment Share on other sites More sharing options...
cuthound Posted January 21, 2017 Report Share Posted January 21, 2017 (edited) Right, I've not been paying full attention cus Im on holiday, I did not realise that you had got the other cells right up to 1.278. The problem is the same one that gives the "wisdom" that if you mix old and new batteries the new ones will be pulled down to the capacity of the old ones, and this is true with batteries in series. During normal charge the current will reduce once the weakest cell has taken its full charge so the others will never get their full charge. However I am not 100% sure this was true when I had my strange cell. In your case you are equalising so likely will get the other cells up to full charge, indeed surely this is what equalising is all about?? I suspect once you revert to normal charge the sg of the other cells will rapidly fall....but you can test this and replace hypothesis with facts. .............Dave Exactly this. I once came across a DC power system, where each 2 volt cell had a transistor shunt across it. When the first cell was fully charged, the shunt allowed the charge current to bypass that cell, allowing the whole battery to charge quicker, and reducing stress on the plates in the cells which reached a fully charged status earlier. Made topping the cells up a bit of a bugger though! Edited January 21, 2017 by cuthound Link to comment Share on other sites More sharing options...
WotEver Posted January 21, 2017 Report Share Posted January 21, 2017 Exactly this. I once came across a DC power system, where each 2 volt cell had a transistor shunt across it. When the first cell was fully charged, the shunt allowed the charge current to bypass that cell, allowing the whole battery to charge quicker, and reducing stress on the plates in the cells which reached a fully charged status earlier. Made topping the cells up a bit of a bugger though! How did the shunts know? Link to comment Share on other sites More sharing options...
cuthound Posted January 21, 2017 Report Share Posted January 21, 2017 How did the shunts know? By measuring the cell voltage. Link to comment Share on other sites More sharing options...
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