[PSUBS-MAILIST] Magnacom SW-1000-sc Battery

[Alan James via Personal_Submersibles]

Hi David, 
using a 2 cel configuration to illistrate; the most basic set up with lithium batteries would be to have 2 cels in series with the main positive & negative wires coming off the ends. Additionally there would be 3 smaller gauge wires running from the positive, the negative & the point where the two batteries join. These smaller wires go to a particular connector compatible with a balance charger. The balance charger reads the voltage of each individual battery & draws current away from over charged batteries and adds it to under charged batteries. The balance charging is needed because lithium batteries can go out of sink in time to the point where one battery gets charged to a dangerously high level & another gets low in comparison & can be damaged by being run too low. I have lithium packs with just these balancing wires added but in the applications I'm using them on (drones & lights) that's all I need as I have a flight controller on the drones checking the power level & volt meters on the lights. Most rc lithium battery packs just have the added balancing wires. 
What you need additionally depends on what electronics is already in the module.
A low voltage indicator or cut-off is important. In some of my uses the high & low voltage
limits are programmable. Am mentioning this in case any integrated circuits in your current electronics are pre-programmed.
Alan

On Saturday, December 19, 2020, 03:07:26 PM GMT+13, David Colombo via Personal_Submersibles <personal_submersibles at psubs.org> wrote:


Hi Alan, one of the fuse is a self reset fuse based upon temperature. The other im not so sure.  The original batteries were 1.2 volts (5) total for 12v. If i go with the 16050 li batteries I have as new cells, they are 3.7v, charge to 4.2, discharge to 3.0v. I was thinking that I would go with 4s2p for a total of 8 batteries at 14.8v I could be wrong, but dont I even need a bms even for this small quantity? As I have never built a Li battery before, I figured that a small unit will be the start to be a bigger battery pack. 

Best Regards,
David Colombo

804 College Ave
Santa Rosa, CA. 95404
(707) 536-1424
www.SeaQuestor.com



On Fri, Dec 18, 2020 at 5:35 PM Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
David, the electronics may be a low voltage protection circuit, or a low high voltage protection circuit so you don't overcharge the batteries. 
As Sean says, if you replace with lithium you have to match the battery voltage. Lithium Iron batteries have a nominal voltage of 3.7 but can be charged to 4.2, & discharged to a minimum of 3V. So that gives 2 options, a 3 cel or 4 cel configuration. So 4 cel would be just above 16.6V and could be used down  to 12V (very minimum) or 3 cel 12.6V & 9V minimum. 
Alan

On Saturday, December 19, 2020, 09:24:43 AM GMT+13, David Colombo via Personal_Submersibles <personal_submersibles at psubs.org> wrote:


Hi Alan, The unit in the sub I can. The topside unit I was hoping to keep the unit intact in case it could also be used as a diver unit.

Best Regards,
David Colombo

804 College Ave
Santa Rosa, CA. 95404
(707) 536-1424
www.SeaQuestor.com



On Fri, Dec 18, 2020 at 12:03 PM Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
David, 
can you just wire them in to 12V in the boat & forget about the battery packs, or are you intending to use them for scuba diving. 
Alan

On Thursday, December 17, 2020, 06:39:22 AM GMT+13, David Colombo via Personal_Submersibles <personal_submersibles at psubs.org> wrote:


Hi guys, I torn down the one battery I got with my magnacom units so I can build a couple more.  Attached are photos of the teardown. Only problem is one component that only had labeling on one side. The other side had only the letters va with a smudge over other data. I think it's a fuse based on the fact it interrupts the circuit.  I sketched out the circuit for reference. I thought taught there might be a BMS, but apparently not.  Jon, to recreate the circuit board component, would you recommend having done by a fabricator? Any ideas or thoughts would be appreciated.
Thanks,
David
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