battery charging voltage - Page 1
Forum section: electronics / beginners

author: ME
author_rank: Frequent Contributor
timestamp: April 30, 2025, 06:49:25 am
content: Hi folks , I have a hankook dc27mf calcium leasure battery,it has been sat unconnected for about a year , terminal voltage is 12v , what is the best way to charge it using a lab psu ? ,i see some mention of charging it a c/10 at 16.5v is that ok?.cheers.

author: mikerj
author_rank: Super Contributor
timestamp: April 30, 2025, 07:49:32 am
content: The Hankook battery catalogue (https://www.tayna.co.uk/leisure-batteries/hankook/dc27/) states 16.0v for flooded cells when using constant voltage charging.

author: ME
author_rank: Frequent Contributor
timestamp: April 30, 2025, 08:08:41 am
content: Where does it say that?, I have looked at the link but see no mention of charging voltages for any !,cheers.

author: BeBuLamar
author_rank: Super Contributor
timestamp: April 30, 2025, 09:53:16 am
content: I think the information is in this pdfchrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://cdn.tayna.com/datasheets/HANKOOK%20Battery%20Range%20Datasheet.pdfYou can do a constant current/constant voltage charging at 4.5A and 16V.

author: mikerj
author_rank: Super Contributor
timestamp: April 30, 2025, 03:09:41 pm
content: Quote from: ME on April 30, 2025, 08:08:41 amPage 39 of the "HANKOOK Battery Range Datasheet", not the DC27 datasheet.

author: ME
author_rank: Frequent Contributor
timestamp: April 30, 2025, 04:12:10 pm
content: can i use this with a blocking diode?https://www.aliexpress.com/item/1005006161942505.html?spm=a2g0o.productlist.main.2.39a33338d42IYr&algo_pvid=c45a34f3-21c0-4e3e-bc69-503287da12ca&algo_exp_id=c45a34f3-21c0-4e3e-bc69-503287da12ca-1&pdp_ext_f=%7B%22order%22%3A%224939%22%2C%22eval%22%3A%221%22%7D&pdp_npi=4%40dis%21GBP%2142.73%2112.39%21%21%21403.85%21117.12%21%40210384b217460293738458815e3d7e%2112000036053221199%21sea%21UK%212308464272%21X&curPageLogUid=D7FLOYwF7MNX&utparam-url=scene%3Asearch%7Cquery_from%3A

author: Zenith
author_rank: Frequent Contributor
timestamp: April 30, 2025, 04:30:23 pm
content: I wouldn't expect too much if it hasn't been charged for a year and the voltage is now 12V. Sulphation starts below 12.4V.To counter self-discharge, charge them every few weeks, or use a float charger which will just balance the self-discharge.

author: ME
author_rank: Frequent Contributor
timestamp: May 01, 2025, 12:52:00 am
content: i set my psu to output 16v at 100ma,what oc terminal voltage should the battery read when 100% FULL?.

author: BillyO
author_rank: Super Contributor
timestamp: May 01, 2025, 01:35:10 am
content: Quote from: ME on May 01, 2025, 12:52:00 am100ma? That's unlikely to charge it in less than a year or so since the self discharge rate is going to be near 100mA. Set your voltage to 16V, set the current to maybe 2A for a low trickle charge then once it gets to 16V @ 500ma you are done.Oh, and you also need to allow for the forward voltage of the diode, which you should use when charging a battery from a bench PSU - so 16.6V.

author: ME
author_rank: Frequent Contributor
timestamp: May 01, 2025, 01:47:21 am
content: well i set my psu to 16v then connected it to the battery then turn the psu current pot untill its ampmeter reads 2 amp.

author: BillyO
author_rank: Super Contributor
timestamp: May 01, 2025, 02:13:19 am
content: That should do it. Monitor it over the next few hours.

author: floobydust
author_rank: Super Contributor
timestamp: May 01, 2025, 03:13:38 am
content: Also ensure the electrolyte level is above the plates.edit: It's a sealed battery? This makes 16V way off as you aren't supposed to equalize-charge these, too much water loss unless you are very careful.For the size 27 PbCaflooded90Ah that is OP's... Many other manufacturer's spec:Equalize is 16.2VBulk charge is 14.7V to 0.01-0.03C which is 0.9-2.7Aso there is a fair chance it never makes it to 16V with 2A.

author: BeBuLamar
author_rank: Super Contributor
timestamp: May 01, 2025, 12:36:18 pm
content: If you have a PSU with current limiting then set the voltage to 16V and current limit to 4.5A. That what I read in the brochure at the website. 4.5A is only 1/20C which is a very slow charging rate. Lead acid batteries generally charged at 1/10C. NiMH and Li-Ion they charge at much higher rate. Some even at 1/C.Now if you have only the PSU with constant voltage but no current limit then you have to adjust the voltage to that the current is 4.5A. But in this case the current will continue to drop as the battery charged which is quite a difficult thing to do. When you raise the voltage ot 16V and the current lis 4.5A or lower then leave the voltage at 16V until the current gets very low then the battery is fully charged.

author: ME
author_rank: Frequent Contributor
timestamp: May 01, 2025, 01:31:30 pm
content: So i will ask againe what voltage should it meaasure at its terminals with the psu disconnected when its 100% state of charge ie open circuit volts?,is that clear?, thanks.

author: bdunham7
author_rank: Super Contributor
timestamp: May 01, 2025, 01:46:05 pm
content: Quote from: ME on May 01, 2025, 01:31:30 pmIt depends slightly on temperature and exact battery chemistry, but OCV of a fully-charged flooded battery at room temperature that has been disconnected from the charger for an hour or more will be very close to 12.6V.

author: ME
author_rank: Frequent Contributor
timestamp: May 01, 2025, 02:03:25 pm
content: Quote from: bdunham7 on May 01, 2025, 01:46:05 pmthis is a deep cycle lead acid calcium jobby ok.

author: BillyO
author_rank: Super Contributor
timestamp: May 01, 2025, 02:04:10 pm
content: As was already pointed out, everything you need to know is in this datasheet:https://cdn.tayna.com/datasheets/HANKOOK%20Battery%20Range%20Datasheet.pdfGo to page 36.The reason I suggested 2A and monitoring it was to see if would take a charge at all. As BeBuLamar suggested. the recommended charge rate is 4.5A @ 16V. The data sheet puts the expected OCV at 12.75V.

author: BeBuLamar
author_rank: Super Contributor
timestamp: May 01, 2025, 03:41:50 pm
content: Quote from: ME on May 01, 2025, 01:31:30 pmIn the HANKOO Battery Range Datasheet it said 12.75V.

author: ME
author_rank: Frequent Contributor
timestamp: May 01, 2025, 04:49:43 pm
content: Well i let it go untill it was sitting at 2a at 15.6v then took it off charge,its been 30 mins and measures 13.36v, also its eye is green,time to dig out my 250w inverter and see what capacity has vanished.

author: floobydust
author_rank: Super Contributor
timestamp: May 01, 2025, 05:49:37 pm
content: I would have kept charging at 14.4V until below 2A, to see if it is sulfated. If that settles down then I go up to 16V for equalize charge.The battery needs more than a one-phase charging scheme like the 2021 datasheet implies, especially if sitting for a year below say 12.4VOK it's called an "SMF" sealed maintenance free, I could not see the removable caps to check electrolyte level and though maybe AGM.

author: ME
author_rank: Frequent Contributor
timestamp: May 03, 2025, 02:46:00 pm
content: Well i hooked up a 250w inverter with the oc voltage of 12.16v at 7.42am with it drawing 2.25amps at 9.42pm it tested off load at 12.06v, does that look rite?

author: bdunham7
author_rank: Super Contributor
timestamp: May 03, 2025, 03:50:08 pm
content: Quote from: ME on May 03, 2025, 02:46:00 pmIf the OCV dropped to 12.16V on its own then it wasn't fully charged or has a bad cell. I may have misunderestimated the time it would take to settle, but eventually it should end up about 12.6V or so if fully charged. The fact that your voltage went as high as it did without charging the battery fully does indicate some trouble, perhaps sulfation or possibly a bad cell. Does/did the OCV recover from 12.06V after a rest? That voltage indicates about a 25-30% charge, but you only drew about 32Ah from a 90Ah battery so either it was not fully charged at the beginning or the battery has lost capacity. Try another charge with more current if you can. If 2A is all you have, then go for at least 48-72 hours with a 16V limit.Do you have a thermal camera? If one section of the battery gets warmer than the others when charging that is a big clue that you have an issue. If it is bad enough or if you use a high enough charge rate you might be able to feel the temperature difference.