gwhy Posted December 12, 2016 Report Share Posted December 12, 2016 Gwhy, thanks for the response. Got momentarily distracted by work and life, but back on to this project now. Assuming I go with the 4x 16,000mAh 6S to build out a 32,000mAh 12S pack does it matter if I connect them in series first and then parallel? I don't see any impact to the calculations of the packs - the constant discharge rate of 64A and peak of 160A would seem to stay the same - or am I missing something? Reason I ask is I can get hold of 2 well priced 48V (adjustable) CC/CV power supplies to bulk charge, but they're only rated to 240W/5A so was thinking of connecting each of the 2 packs as 12s and then to parallel to simplify the disconnecting for bulk charging to the 2 chargers. Hope this makes sense. Cheers, Hosko no you are not missing anything.. dependant on the psu's you can acutally parallel then to make a 10A psu but you will have to do a bit of digging on the web to find out how. the problem with having 2 12s packs and then joining them in P is if a pack ( 12s ) if faulty or a cell is bad withing the pack it will pull down the other pack (makng the second pack bad ) and could also cause a very large spark when connecting them in P. Also I would recomend getting a small 12s bms to use on the charger that will balance the cells and help protect from any over charging ( they are very easy to wire up and gives a extra margin of safety). Quote Link to comment Share on other sites More sharing options...
hosko11 Posted December 14, 2016 Report Share Posted December 14, 2016 no you are not missing anything.. dependant on the psu's you can acutally parallel then to make a 10A psu but you will have to do a bit of digging on the web to find out how. the problem with having 2 12s packs and then joining them in P is if a pack ( 12s ) if faulty or a cell is bad withing the pack it will pull down the other pack (makng the second pack bad ) and could also cause a very large spark when connecting them in P. Also I would recomend getting a small 12s bms to use on the charger that will balance the cells and help protect from any over charging ( they are very easy to wire up and gives a extra margin of safety). Not long after making the post I came across the parallel PSU idea so am going ahead with that approach - makes it much simpler. The chargers are Mean well HLG-240H-48A's. Actually managed to get 4x 2nd hand ones at a good price, so can build a charger with a conservative 16A capacity. I like the idea of the BMS as well. I imagine I'll need to parallel the balance leads for pairs of packs (series packs) to make this work? I'll dig through the thread - I'm sure the answers here already Thanks again! Quote Link to comment Share on other sites More sharing options...
gwhy Posted December 14, 2016 Report Share Posted December 14, 2016 I have a couple of 10A bulk chargers ( turnt down to around 7-8A output ).. ( mean well (clones) £20 from fleabay :-) ) and always use a bms connected to it just to protect the cells during the charging process, the bms's are cheap enough as you dont need them to be able to supply very high current for the discharge as they are only used for charging, i have 15A ( charge ) 12s bms also a 13s bms and a 14s bms.. if you go down this route for the first couple of charges monitor the voltages of the cells as if the charge current is to high and the bms's can not bleed the high cells fast enough than the cells are charging there is a possibility that the cells can over charge. once you have a good safe setup then the whole process becomes a very cheap plug'n'play setup. the taps are permently P'ed on my battery packs so there is less room for error and less ware and tear on the tap connectors.. cant stress enough to make sure that the bms you choose can bleed the cells ( when cells are fully charged ) faster than they are being charged!! Quote Link to comment Share on other sites More sharing options...
hosko11 Posted December 21, 2016 Report Share Posted December 21, 2016 I have a couple of 10A bulk chargers ( turnt down to around 7-8A output ).. ( mean well (clones) £20 from fleabay :-) ) and always use a bms connected to it just to protect the cells during the charging process, the bms's are cheap enough as you dont need them to be able to supply very high current for the discharge as they are only used for charging, i have 15A ( charge ) 12s bms also a 13s bms and a 14s bms.. if you go down this route for the first couple of charges monitor the voltages of the cells as if the charge current is to high and the bms's can not bleed the high cells fast enough than the cells are charging there is a possibility that the cells can over charge. once you have a good safe setup then the whole process becomes a very cheap plug'n'play setup. the taps are permently P'ed on my battery packs so there is less room for error and less ware and tear on the tap connectors.. cant stress enough to make sure that the bms you choose can bleed the cells ( when cells are fully charged ) faster than they are being charged!! Seems no one mentions the bleed capacity of the BMS or is there a parameter I'm not understanding that tells me this or is it trial and error? If charging 12S @ 12A I'm assuming you want something that can bleed at up to 1A per channel/cell? I'm looking at this 12S BMS from Supower - http://www.ebay.com.au/itm/44V-48V-50-4V-12S-30A-Lithium-ion-Li-ion-LiPo-Li-Polymer-Battery-BMS-PCB-System-/221274094989 Quote Link to comment Share on other sites More sharing options...
gwhy Posted December 21, 2016 Report Share Posted December 21, 2016 (edited) You need to look for balance current and in the bms case in the link its 60mA .. the higher the balance current the quicker it will fully charge as the bms will not keep turning off should a cell go over the shut down voltage which is 4.20v ( which I hope is a typo in the link as its the same as the balance voltage, normally the shut down voltage is around 0.1v higher than the balance voltage spec) because then the cell needs to be bled back down to 4.05v before charging will continue and if the cells are out of balance by a lot this can take ages to do.. the reason I said to make sure it can bleed fast enough is that I have had some types of bms's that dont always turn off when a cell goes over voltage and they rely on the bled current to protect the cells from over charging but if you keep the overall top off charge current to a sensible level then this should not be a problem i.e set your charge voltage to maybe 50.45v ( for 12s lipo ) this should help stop the bms turning off ( unless you have a really out of balance cell ) but also keep the other cells charging when a cell is being bled. I have not run through the figures for the bms in the link but this is about where you need to start . monitor the cells as they become fully charged i.e 4.2v they should be held @ 4.2v and any low cells will still be charging , turn the current up or down ( well.... the voltage ( 50.4 -50.8v ) ) to find that sweet spot when you are still charging the cells even if higher cells are bleeding because if the bms turns off then its a long wait ( that cell needs to come back down to 4.05v ) before it come s back on to charge again .. Once setup then thats it but its that final charger voltage that is the key ( if its to low the battery do not balance and if its to high it can take a very long time to top off the battery.. so there is a bit of trial and error as no 2 bms's are the same spec ( even the same make bms's ) ... oh just remembered the clone MW psu's I have turn off the output when the output current is very low and this was a small problem for my setup as when the battery is near fully charged the current is near zero.. just keep that in mind.. i over came htis problem by just putting a permainat load on the output of the psu just enough to keep the output on. sorry to waffle on and i hope it makes sense.. Edit: If you want to get even more fancy with the setup what I done was to fit a break out socket from each set of 6s from the battery balance taps that I fit some 6s cell monitor alarms to when charging, this gives me the real time voltages of each cell plus the alarms i use also has a HV alarm that sounds should any of the cells go above 4.3v... or you can fit a couple of battery medics to the break outs, these do not have HV alarms but they do have a bleed/balance function so you can increase the bled current and also monitor the cell voltages.. either way its a good addition to have break out sockets on the balance taps. Edited December 21, 2016 by gwhy Quote Link to comment Share on other sites More sharing options...
lennie Posted December 21, 2016 Report Share Posted December 21, 2016 After reading this thread I had decided what to buy to make a oset 36v battery but all the recommended stuff seems to be out of stock on hobby king, left it 6 weeks hoping it would come back into stock but no luck, emailed them and no eta either. I did plan on using 3 of these amd the bms posted earlier in this thread. https://hobbyking.com/en_us/zippy-flightmax-8400mah-4s2p-30c-lifepo4-pack.html Can anyone suggest reliable sources for similar batteries or a suitable alternative, I cant see any similar stuff they are all much lower capacity. Thanks. Quote Link to comment Share on other sites More sharing options...
gwhy Posted December 21, 2016 Report Share Posted December 21, 2016 so you are in Australia?.. got these is stock https://hobbyking.com/en_us/zippy-flightmax-4200mah-4s2p-30c-lifepo4-pack.html just works out a little more expensive as you will have to get 6.. make sure they have 6 in stock before you order. or you could go down the lipo route ?.. a bit cheaper,lighter,smaller,higher capacity. Quote Link to comment Share on other sites More sharing options...
lennie Posted December 21, 2016 Report Share Posted December 21, 2016 (edited) so you are in Australia?.. got these is stock https://hobbyking.com/en_us/zippy-flightmax-4200mah-4s2p-30c-lifepo4-pack.html just works out a little more expensive as you will have to get 6.. make sure they have 6 in stock before you order. or you could go down the lipo route ?.. a bit cheaper,lighter,smaller,higher capacity. unfortunately not, Hertfordshire!!!!!!!! Im looking at anything that's uk or Europe stock to avoid import tax. My lad is very tall for his age so I got him a 16 on his 4th birthday as he was far to big for the 12.5 we borrowed. The extra size and weight has knocked his confidence so I had planned to buy 6 of the batteries I linked and run 3 in series for now and swap them for the other set if he want to ride more to keep the weight down then parallel the two sets at a later date when his a bit stronger to increase the ride time without messing about swapping batteries part way through the day. Edited December 21, 2016 by lennie Quote Link to comment Share on other sites More sharing options...
gwhy Posted December 21, 2016 Report Share Posted December 21, 2016 :-) the reason i asked because the link to the batterys that you posted was Austrailia... yes i see where you are coming from about the batterys, they do hvae the 4200mah in stock in the uk ( but check with them before ordering ) as I said you will have to get 6 of them to make up to the 8400mah capacity , just permently wire them in P in pairs to make up 3 8400mah batterys. just works out a little more expensive Quote Link to comment Share on other sites More sharing options...
lennie Posted December 23, 2016 Report Share Posted December 23, 2016 (edited) Understand what your saying, could be a good idea. seems they are getting less and less in stock so I am hoping that means a shipment is coming and they will have the "ideal" batteries in stock before spring, at the moment the woods are too wet for a little bike so he just wants to blast around the fields so they weight isn't a issue as much as it will be when it dry's out and we can try the rougher stuff again. Edited December 23, 2016 by lennie Quote Link to comment Share on other sites More sharing options...
lennie Posted December 23, 2016 Report Share Posted December 23, 2016 (edited) Just checked and these have appeared on hk https://hobbyking.com/en_us/zippy-compact-5800mah-10s-25c-lipo-pack.html Pair of those in parallel could be good? Edited December 23, 2016 by lennie Quote Link to comment Share on other sites More sharing options...
gwhy Posted December 23, 2016 Report Share Posted December 23, 2016 yes those look ok.. I have not seen these before on the hk website, cust reviews seem good. what charger have you got to charge them if you go down the lipo route ? as 36v volt lipo (10s ) is a different top of voltage than 36v volt lifepo4 (8s) , there are a few types of 10s lipo bms on ebay but not many CV/CC 36v (lipo) chargers. Quote Link to comment Share on other sites More sharing options...
lennie Posted December 23, 2016 Report Share Posted December 23, 2016 thanks for the reply, I have nothing for lipo at the moment so am not steered in any direction to suit a existing set up. Quote Link to comment Share on other sites More sharing options...
greg555 Posted December 23, 2016 Report Share Posted December 23, 2016 Just checked and these have appeared on hk https://hobbyking.com/en_us/zippy-compact-5800mah-10s-25c-lipo-pack.html Pair of those in parallel could be good? I don't see any 10s Chargers on hk Quote Link to comment Share on other sites More sharing options...
mikedufty Posted December 23, 2016 Report Share Posted December 23, 2016 Just sort them from most expensive to least and you will find this one near the top. https://hobbyking.com/en_us/turnigy-reaktor-30a-1000w-balance-charger.html Quote Link to comment Share on other sites More sharing options...
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