Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Converting SLA to Lithium Ion
#1
Hey Guys,

I'm currently looking to change a Rechargeable ZS4C 12V12AH SLA Battery to a lithium ion battery pack. I'm trying to increase the burn time on an underwater scooter.

Currently (the one above) that comes with the unit is a SLA battery. It is rated 12v 12aH and gets about 120 minutes.  amazon : Sea-Doo-Sea_scooter-GTI Battery  (first post so can't give link =/ )

What do you think the max aH I can put in this size similarly sized battery to get the most time? I'm shooting for 160-200 minutes (which is my typical dive time)

How do you think this would handle under pressure? (scuba diving)

Thanks,
O

Link to battery https://www.amazon.com/Sea-Doo-Sea-Scoot...B00CRY0QUQ
Dimensions: 6" x 4" x 4" i believe.
Reply
#2
Just a couple of thoughts.
How much does operation or failure of this device affect your safety while diving?
I would be trying to work out if the battery does experience any unusual pressure and if that is ok for any replacement batteries.
You would need to see what size configuration of cells fit in the battery compartment.
You will need to consider the voltage the device operates at when designing a replacement battery pack.
Reply
#3
The operating voltage is 24V, altho the range of the voltage is probably same as any SLA, ~22.4V - ~29V.

I personally wouldn't go with reclaimed cells in this case, and I wouldn't go with anything other than LiFePO4 cells. They would work a lot better in this application as they are a "direct" replacement for LA batteries.
The linked battery is a very common one used in Battery Backup systems, as well. Only difference might be the connectors.

For the case, I don't believe anything fancy would be needed as the compartment where these are housed in are sealed as well, correct? Water can only get in if you open the compartment, right?

However, the case should be a proper case where the cells are not exposed on the sides like most powerwall builders have done, but inside an enclosure of some sort. Maybe even a 3D printed one.
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

Please come join in general chit-chat and randomness at Discord Chat (channels: general, 3d-printing, linux&coding, 18650, humor, ...)
(this chat is not directly affiliated with SecondLifeStorage; VALID email req'd)
Reply
#4
What about buoyancy? I've never used such devices, but I expect they're designed to be nearly neutral with the weight of the SLA inside?
Modular PowerShelf using 3D printed packs.  30kWh and growing.
https://secondlifestorage.com/t-AJW22-s-...PowerShelf
Reply
#5
(07-30-2019, 05:51 AM)ajw22 Wrote: What about buoyancy?  I've never used such devices, but I expect they're designed to be nearly neutral with the weight of the SLA inside?

That is an interesting point.

If you filled the battery compartment with 18650 cells, there would probably be a fair amount of extra air in the compartment that was not there when the SLA battery was installed.

There will be gaps between the 18650 cells and the cells are unlikely to completely fill the compartment the way the SLA battery did.


I think it would probably be fairly easy to add extra weight to get things back to the same sort of balance.
Reply
#6
Not only more air pockets, but a SLeadA is _much_ heavier (denser) than any Lithium cell.
Doing some rough maths:

SLA: 4000g 1400cc (2.8g/cc)
1x 18650 Li-Ion in "grid" bracket: 45g 27.6cc (1.63g/cc)
Stainless steel: 8g/cc
...>
18% of the space needs to be filled with solid stainless steel weights.
82% of the space with 18650 LiIon cells.

Of course, this could be optimized by using lead weights and offset (non-grid) 18650 brackets.
And this is without the BMS, which is also much less dense than a SLA.
Modular PowerShelf using 3D printed packs.  30kWh and growing.
https://secondlifestorage.com/t-AJW22-s-...PowerShelf
Reply
#7
(07-29-2019, 11:03 PM)Korishan Wrote: The operating voltage is 24V, altho the range of the voltage is probably same as any SLA, ~22.4V - ~29V.

I personally wouldn't go with reclaimed cells in this case, and I wouldn't go with anything other than LiFePO4 cells. They would work a lot better in this application as they are a "direct" replacement for LA batteries.
The linked battery is a very common one used in Battery Backup systems, as well. Only difference might be the connectors.

For the case, I don't believe anything fancy would be needed as the compartment where these are housed in are sealed as well, correct? Water can only get in if you open the compartment, right?

However, the case should be a proper case where the cells are not exposed on the sides like most powerwall builders have done, but inside an enclosure of some sort. Maybe even a 3D printed one.

The case that holds the battery is water tight. It needs to be. 

(07-30-2019, 07:18 AM)Oz18650 Wrote:
(07-30-2019, 05:51 AM)ajw22 Wrote: What about buoyancy?  I've never used such devices, but I expect they're designed to be nearly neutral with the weight of the SLA inside?

That is an interesting point.

If you filled the battery compartment with 18650 cells, there would probably be a fair amount of extra air in the compartment that was not there when the SLA battery was installed.

There will be gaps between the 18650 cells and the cells are unlikely to completely fill the compartment the way the SLA battery did.


I think it would probably be fairly easy to add extra weight to get things back to the same sort of balance.

Yes, the system has a front compartment for lead weights specifically to make the device neutrally buoyant (and adjustable for salt/fresh water) only thing is, you can't make the device 'heavier' and hope to achieve this. You can't add air to the device Smile

(07-29-2019, 10:49 PM)Oz18650 Wrote: Just a couple of thoughts.
How much does operation or failure of this device affect your safety while diving?
I would be trying to work out if the battery does experience any unusual pressure and if that is ok for any replacement batteries.
You would need to see what size configuration of cells fit in the battery compartment.
You will need to consider the voltage the device operates at when designing a replacement battery pack.

If a failure occurred, I should be fine. I'm only at 20-30 ft of water, and would have all my scuba gear on me.

(07-30-2019, 08:23 AM)ajw22 Wrote: Not only more air pockets, but a SLeadA is _much_ heavier (denser) than any Lithium cell.
Doing some rough maths:

SLA:    4000g  1400cc   (2.8g/cc)
1x 18650 Li-Ion in "grid" bracket:  45g  27.6cc  (1.63g/cc)
Stainless steel: 8g/cc
...>
18% of the space needs to be filled with solid stainless steel weights.
82% of the space with 18650 LiIon cells.

Of course, this could be optimized by using lead weights and offset (non-grid) 18650 brackets.
And this is without the BMS, which is also much less dense than a SLA.

Yeah ajw, the sizes/weights are much different. The device has a compartment for counterweights to keep the device neutrally buoyant , reducing the general weight is ok since we can always add more weights... making it heavier would be the issue
Reply
#8
Could we just hot swap out a LiFePO4 battery with the same dimensions as long as they are both 12V? just find one with a higher capacity?
Reply


Who read this thread?
28 User(s) read this thread:
daromer (07-30-2019, 02:53 PM), Solardad (07-30-2019, 01:04 PM), ajw22 (08-01-2019, 06:16 AM), RikH (07-30-2019, 10:07 PM), OffGridInTheCity (07-29-2019, 08:10 PM), Lucan (07-31-2019, 12:00 AM), Wulffi (08-01-2019, 04:16 PM), nero1986 (08-03-2019, 03:13 PM), Tektiitti (08-02-2019, 07:35 PM), kimbo (07-31-2019, 05:50 AM), stok (07-30-2019, 09:03 AM), Otakar (08-01-2019, 08:22 AM), Oonej (08-01-2019, 10:22 AM), Bastler_Ro (07-29-2019, 07:47 PM), Wolf (07-30-2019, 04:58 PM), Sean (07-30-2019, 03:24 PM), Korishan (07-30-2019, 02:52 PM), PAF (07-30-2019, 07:37 AM), Geek (07-31-2019, 12:09 AM), Oz18650 (07-30-2019, 11:37 PM), CarelHassink (07-30-2019, 04:53 PM), gpn (07-30-2019, 04:18 AM), Dala (07-30-2019, 08:27 AM), Crimp Daddy (07-30-2019, 01:42 AM), jonyjoe505 (07-30-2019, 02:39 AM), mishok (08-14-2019, 02:39 PM), Katarn_89 (08-02-2019, 07:08 PM), Funkadelicious (08-13-2019, 09:51 AM)

Forum Jump:


Users browsing this thread: 1 Guest(s)