Battery Question?

oli · 14th July 2007, 23:54

I also use 2 batteries 3,6 Li SAFT 14500 and each time my digital "tester" show me 7,2 Volts before . However , in the Meg , this value goes down between 6,7 and 6,8 maximum.
But don't be worry, the life is really bigger than the 5 batteries from ISC

ps: Sorry for my bad language

Oli

***jradomski*** · 15th July 2007, 04:36

Quote: (Originally Posted by sensor330)

I soldered to 3.6 lithum batteries today for my Meg. When I test them on the volt meter I get 7.2vdc, and when I put them in the Meg I only get a reading of 6.5v. Does anyone know why that is?

Scott

Just look at the satasheets for the cells.. It explains it all...

3.6v is the open circuit voltage.. true no load.. The meg no load voltage is the voltage when the handsets are "idle" that is not holding the solenoid open and probably no backlight..

I know that the displays that the meg uses are quite power hungry (relatively speaking - 15ma bl off, 45ma bl on), The total power draw "idle" should be somewhere between the 125ma and 35ma curve (alot closer to the 35ma curve), so voltage per cell should be about 3.35 or 6.7v. for two.. It should be able to maintain this voltage (at this constant load) for about 50 hours(then a gradual drop in voltage over the next 30 hours, and then a steep drop).. Of course the solenoid firing and the backlight will lower the duration.. Drawing a load in the cold will drop the life of the cell by about 10%

sensor330 · 15th July 2007, 04:56

They says change the alkaline batteries at 5.2v, what would be the estimated voltage to change lithium?

Scott

***jradomski*** · 15th July 2007, 11:28

Quote: (Originally Posted by sensor330)

They says change the alkaline batteries at 5.2v, what would be the estimated voltage to change lithium?

Scott

I would change it at the same voltage, although the lithium cells can still provide reasonable current at 2.5v, (5v for the pack), the limiting factor is probably the voltage regulation within the meg electronics. Buck style voltage regulation (whether linear or switching) will have an inherent voltage drop.. (I am pretty sure this is the type of regulation thats present in the Meg), and the electronics have specific voltage requirements..

Changing it at 5.2v is only a loss of about 10% of the rated battery capacity..

**JPJones** · 15th July 2007, 12:21

Quote: (Originally Posted by jradomski)

I would change it at the same voltage, although the lithium cells can still provide reasonable current at 2.5v, (5v for the pack), the limiting factor is probably the voltage regulation within the meg electronics. Buck style voltage regulation (whether linear or switching) will have an inherent voltage drop.. (I am pretty sure this is the type of regulation thats present in the Meg), and the electronics have specific voltage requirements..

Changing it at 5.2v is only a loss of about 10% of the rated battery capacity..

If your talking about the same Saft batteries that we us in the O2ptima I agree 5 volts should work.

***jradomski*** · 15th July 2007, 16:11

Quote: (Originally Posted by JPJones)

If your talking about the same Saft batteries that we us in the O2ptima I agree 5 volts should work.

We are talking about using C size saft cells which actually have better current ratings than the AA sized cells..

I just found anewer doc and updated the times above..

sensor330 · 15th July 2007, 16:13

Quote: (Originally Posted by jradomski)

We are talking about using C size saft cells which actually have better current ratings than the AA sized cells..

I just found anewer doc and updated the times above..

I used the AA size.

***jradomski*** · 15th July 2007, 16:26

Quote: (Originally Posted by sensor330)

I used the AA size.

The doc that I originall referenced I think was an error since the run times were very close to that of the AA cells.. I verified the current AA and C cell sizes and the voltages under load are very similiar, just the point at which they start to drop off differs (the cell voltage remains constant for most of the battery life unlike alkaline cells that have a constant voltage drop). The AA drop off at 20hours and quickly decay after that, where the c cells can hold on longer during the drop off..

In both cases by a cell voltage of 2.6v they are well into the steep decay curve..

14th July 2007, 23:54	#11 (permalink)
oli New Member Current Rebreather/s: Megalodon Dolphin Other Rebreather/s: Dolphin Join Date: Jun 2006 Location: Belgium Posts: 12	Re: Battery Question? I also use 2 batteries 3,6 Li SAFT 14500 and each time my digital "tester" show me 7,2 Volts before . However , in the Meg , this value goes down between 6,7 and 6,8 maximum. But don't be worry, the life is really bigger than the 5 batteries from ISC ps: Sorry for my bad language Oli
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15th July 2007, 04:36	#12 (permalink)
*jradomski* Moderator Current Rebreather/s: Inspiration Classic Sport Kiss Optima rEvo Other CCR Home Build Other Rebreather/s: Inspiration Vision Evolution Megalodon Classic Kiss rEvo Other CCR Home Build Join Date: Mar 2005 Location: "Da" Bronx Posts: 2,998	Re: Battery Question? Quote: (Originally Posted by sensor330) I soldered to 3.6 lithum batteries today for my Meg. When I test them on the volt meter I get 7.2vdc, and when I put them in the Meg I only get a reading of 6.5v. Does anyone know why that is? Scott Just look at the satasheets for the cells.. It explains it all... 3.6v is the open circuit voltage.. true no load.. The meg no load voltage is the voltage when the handsets are "idle" that is not holding the solenoid open and probably no backlight.. I know that the displays that the meg uses are quite power hungry (relatively speaking - 15ma bl off, 45ma bl on), The total power draw "idle" should be somewhere between the 125ma and 35ma curve (alot closer to the 35ma curve), so voltage per cell should be about 3.35 or 6.7v. for two.. It should be able to maintain this voltage (at this constant load) for about 50 hours(then a gradual drop in voltage over the next 30 hours, and then a steep drop).. Of course the solenoid firing and the backlight will lower the duration.. Drawing a load in the cold will drop the life of the cell by about 10% __________________ Joe Radomski CCR Trimix Instructor Trainer ANDI Instructor Trainer Director #10 All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated. Last edited by jradomski : 15th July 2007 at 16:18.
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15th July 2007, 04:56	#13 (permalink)
sensor330 Custom Title Allowed! Current Rebreather/s: Megalodon Other Rebreather/s: Not Bought Yet Inspiration Classic Join Date: Feb 2005 Location: Victoria, British Columbia, Canada Posts: 581	Re: Battery Question? They says change the alkaline batteries at 5.2v, what would be the estimated voltage to change lithium? Scott
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15th July 2007, 11:28	#14 (permalink)
*jradomski* Moderator Current Rebreather/s: Inspiration Classic Sport Kiss Optima rEvo Other CCR Home Build Other Rebreather/s: Inspiration Vision Evolution Megalodon Classic Kiss rEvo Other CCR Home Build Join Date: Mar 2005 Location: "Da" Bronx Posts: 2,998	Re: Battery Question? Quote: (Originally Posted by sensor330) They says change the alkaline batteries at 5.2v, what would be the estimated voltage to change lithium? Scott I would change it at the same voltage, although the lithium cells can still provide reasonable current at 2.5v, (5v for the pack), the limiting factor is probably the voltage regulation within the meg electronics. Buck style voltage regulation (whether linear or switching) will have an inherent voltage drop.. (I am pretty sure this is the type of regulation thats present in the Meg), and the electronics have specific voltage requirements.. Changing it at 5.2v is only a loss of about 10% of the rated battery capacity.. __________________ Joe Radomski CCR Trimix Instructor Trainer ANDI Instructor Trainer Director #10 All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated.
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15th July 2007, 12:21	#15 (permalink)
JPJones O2ptima Test Dummy Current Rebreather/s: Inspiration Classic Megalodon Sport Kiss Classic Kiss Optima Titan Other Rebreather/s: Join Date: Sep 2005 Location: Florida Posts: 367	Re: Battery Question? Quote: (Originally Posted by jradomski) I would change it at the same voltage, although the lithium cells can still provide reasonable current at 2.5v, (5v for the pack), the limiting factor is probably the voltage regulation within the meg electronics. Buck style voltage regulation (whether linear or switching) will have an inherent voltage drop.. (I am pretty sure this is the type of regulation thats present in the Meg), and the electronics have specific voltage requirements.. Changing it at 5.2v is only a loss of about 10% of the rated battery capacity.. If your talking about the same Saft batteries that we us in the O2ptima I agree 5 volts should work. __________________ NSS/CDS Training Chairman www.jpjscuba.com
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15th July 2007, 16:11	#16 (permalink)
*jradomski* Moderator Current Rebreather/s: Inspiration Classic Sport Kiss Optima rEvo Other CCR Home Build Other Rebreather/s: Inspiration Vision Evolution Megalodon Classic Kiss rEvo Other CCR Home Build Join Date: Mar 2005 Location: "Da" Bronx Posts: 2,998	Re: Battery Question? Quote: (Originally Posted by JPJones) If your talking about the same Saft batteries that we us in the O2ptima I agree 5 volts should work. We are talking about using C size saft cells which actually have better current ratings than the AA sized cells.. I just found anewer doc and updated the times above.. __________________ Joe Radomski CCR Trimix Instructor Trainer ANDI Instructor Trainer Director #10 All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated.
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15th July 2007, 16:13	#17 (permalink)
sensor330 Custom Title Allowed! Current Rebreather/s: Megalodon Other Rebreather/s: Not Bought Yet Inspiration Classic Join Date: Feb 2005 Location: Victoria, British Columbia, Canada Posts: 581	Re: Battery Question? Quote: (Originally Posted by jradomski) We are talking about using C size saft cells which actually have better current ratings than the AA sized cells.. I just found anewer doc and updated the times above.. I used the AA size.
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15th July 2007, 16:26	#18 (permalink)
*jradomski* Moderator Current Rebreather/s: Inspiration Classic Sport Kiss Optima rEvo Other CCR Home Build Other Rebreather/s: Inspiration Vision Evolution Megalodon Classic Kiss rEvo Other CCR Home Build Join Date: Mar 2005 Location: "Da" Bronx Posts: 2,998	Re: Battery Question? Quote: (Originally Posted by sensor330) I used the AA size. The doc that I originall referenced I think was an error since the run times were very close to that of the AA cells.. I verified the current AA and C cell sizes and the voltages under load are very similiar, just the point at which they start to drop off differs (the cell voltage remains constant for most of the battery life unlike alkaline cells that have a constant voltage drop). The AA drop off at 20hours and quickly decay after that, where the c cells can hold on longer during the drop off.. In both cases by a cell voltage of 2.6v they are well into the steep decay curve.. __________________ Joe Radomski CCR Trimix Instructor Trainer ANDI Instructor Trainer Director #10 All posts are personal opinions and DO NOT reflect any affiliated agency unless specifically stated.
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