Re-sealing SLA batteries - Page 1
Forum section: electronics / projects

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: May 02, 2020, 01:14:54 pm
content: I've watched multiple YouTube tutorials on refilling UPS SLA batteries with distilled water and using a de-sulfator, I was able to restore a battery's capacity from 2 Ah to 7 Ah.The only issue now is keeping it sealing as the pressure of the released gas while charging/discharging either pops the lids off or starts leaking when taped all around.Has anyone here had any luck with this or should I just toss them out and get new batteries instead?

author: 2N3055
author_rank: Super Contributor
timestamp: May 02, 2020, 01:36:18 pm
content: Quote from: drummerdimitri on May 02, 2020, 01:14:54 pmThrow them away. You cannot refill SLA, electrolite is in a gel format...

author: Gyro
author_rank: Super Contributor
timestamp: May 02, 2020, 01:37:44 pm
content: It makes an interesting experiment, but the dangers of leaking acid into your equipment are probably too high to risk.Dead Lead Acid batteries have a significant scrap value too, which helps offset the cost of a new one(s) - it obviously helps if you have a few to trade.

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: May 02, 2020, 01:42:04 pm
content: I will be keeping them on a flat surface outside of the UPS beneath a glass tray just in case they leak.They have no scrap value where I live unfortunately!

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 02, 2020, 01:46:32 pm
content: LiFePO4 batteries plus a BMS are a mostly drop in replacement for lead acid. LiFePO4 is often cheaper than SLA nowadays, especially for small packs.

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: May 02, 2020, 02:06:55 pm
content: Quote from: NiHaoMike on May 02, 2020, 01:46:32 pmDo you have proof to backup this claim? My findings show the opposite.Either way, I don't mind switching to LiFePO4 however it would need to be a drop in replacement for the typical 7AH lead acid batteries found in most commercial UPS units.Would it be like building a Li-ion battery pack? Shouldn't be a problem as I have made some of those for power banks in the past.

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 02, 2020, 03:23:39 pm
content: LiFePO4 has a different voltage range than regular lithium ion. 3.6V, the maximum charge voltage for LiFePO4, times 4 for a 4S pack is 14.4V which is exactly the maximum charge voltage for 12V lead acid. The float voltage is somewhat lower but also about the same as for lead acid.

author: splin
author_rank: Frequent Contributor
timestamp: May 03, 2020, 01:59:35 am
content: Quote from: drummerdimitri on May 02, 2020, 02:06:55 pmI bought 8 of these '7000mAh' 32700 LiFePo4 cells recently:https://www.aliexpress.com/item/32998328673.html?spm=2114.12010615.8148356.11.5c8f5451McipjNThe 700mAh headline number is obviously fake and does them no credit but they do state 6500mAh as the real capacity. I measured the actual capacities @ 1A discharge rate:6323, 6353, 6373, 6375, 6379, 6381, 6381, 6381mAhThat's a 1% spread. 6 out of the 8 are within +/-0.08% of each other! I wasn't expecting 6500mAh so I wasn't dissapointed having seen a couple of youtube tests and this review which I believe to be the same cell under a different brand name:http://budgetlightforum.com/node/65598The author of the review, HJK, is a member here. Oddly the above review isn't on his websitehttp://lygte-info.dk/. Again the spread in capacities was very small but around 5950mAh. That was 12 months ago, so perhaps the latest cells are higher capacity or there are larger variations between batches. I have ordered some more but it will take at least 4 weeks before they arrive.4 cells to make a 6Ah+ 12V battery currently costs £10.5 or £130/kWh ($163/kWh) which is the lowest cost Li-ion price that I know of for small quantity purchases. I don't know how much a suitable BMS and case would cost but the total cost isn't going to be much more than the £10 typical cost of a 12V 7Ah SLA. I'd be surprised if you could get below the cost of an SLA though.You could fit 8 cells, 70mm x 32mm, into the SLA case to get 12.6AhQuoteFor a drop in replacement the BMS is key. Li-ion cells must not be charged below 0C so won't be suitable for all uses; ideally a BMS with temperature sensor should be used to prevent charging below 0C but I guess most UPSs aren't installed in such environments.

author: NiHaoMike
author_rank: Super Contributor
timestamp: May 03, 2020, 03:20:37 am
content: https://batteryhookup.com/products/emc-12v-module-with-8x-a123-26650$10 for 8x 2.5Ah A123 LiFePO4 cells and BMS with built in voltage regulator. Granted, it would take some rather involved reverse engineering to use the BMS.

author: james_s
author_rank: Super Contributor
timestamp: May 03, 2020, 03:29:47 am
content: Quote from: splin on May 03, 2020, 01:59:35 amI will never understand why they fake the ratings on batteries. It's not hard to find out the true capacity and the fact that it's overstated makes me not want to buy them. Will China ever realize the value in honesty? Happy customers that don't feel cheated are repeat customers.

author: edpalmer42
author_rank: Super Contributor
timestamp: May 03, 2020, 03:34:37 am
content: Quote from: drummerdimitri on May 02, 2020, 01:14:54 pmThere shouldn't be any significant pressure developed during charging and there shouldn't be any pressure at all during discharge.SLA batteries aren't really sealed. They all have a pressure release arrangement that allows a small amount of pressure during charge. Anything more means the battery is being overcharged. You should NOT try to completely seal them up.What size are these batteries and how are you charging them?Ed

author: splin
author_rank: Frequent Contributor
timestamp: May 03, 2020, 03:26:50 pm
content: Quote from: NiHaoMike on May 03, 2020, 03:20:37 amThat's a good price but they are used cells and unlike the Ali express cells I linked it doesn't include shipping which could more than double the cost. I tried to get the shipping cost but it's one of those intensely annoying websites that won't tell you before you've given them complete details including address, telephone numbers, bank A/C numbers, National Insurance number, a signed photo of your genitals as witnessed by an official notary/doctor/solicitor and the name of your first pet.

author: james_s
author_rank: Super Contributor
timestamp: May 03, 2020, 05:35:33 pm
content: Quote from: splin on May 03, 2020, 03:26:50 pmI ordered a couple of those packs since I happened to be in the market for some of those cells already and shipping was $16.97. They're based in the USA though so shipping international is going to be prohibitively expensive if they offer it at all. International shipping from the US has gotten absurdly expensive in the last decade or so.