[Outlaw]

Quote: (Originally Posted by Gilles)

Ask me a legal question, then you'll see


By connecting the batteries parallel (+ with + and - with -) you will double the charge capacity (physical equivalent of doubling the size of a cylinder). These 9V batteries have a capacity of about 625 mAH. By connecting them in parallel, it now becomes 1250mAH, still with 9V.

If you were to connect them in series (+ with -) as we do with the 5 AA cells, then you add the voltage (physical equivalent of doubling pressure to your cylinder), and you would end up with 18V, and frying the electronics.


The 5 AA in series have some 8V and some 2800 mAH capacity, so will still last twice as long as the above paralleled 9V cells. I have had welded cells fail on me during a dive, and thus have preference for something like this if it works.

It seems ok on the secondary, and I will see how it lasts and how the voltage drops with time. Depending, I'll then try on the primary.

hmm,

thanks Gilles,

especially for reassuring me that there are plenty of "stupids" around, and in different fields...

i am trying to find the link on that 9v battery. i can imagine how it would be if you can actually connect them with your way....

i'll let you know. am in the unfortunate position of formatting my pc and forgot to back up my "favorites" folder and i lost all the links i had saved before....

yeah, yeah, i know....am stupid in many "fields"...


Spyros

[Skipbreather]

Quote: (Originally Posted by wedivebc)

Does anone know what minimum voltage is accecptable when using 9v batteries? There must be some point where battery failure is imminent and should be changed.

My sense is that would be highly dependent on both the brand of battery and the type of chemistry (alkaline, lithium, other). The only hard numbers I can give you are with an alkaline Rayovac. I did a test with it running the primary. After 4 1/2 hours it read about 7.5 v no load and 7.1 or 7.2 load and was working normally. A long time (many months) later same battery had recovered to well over 8 v.

Ken

[Outlaw]

Hey Gilles,

i found a link. i think this is one of those batteries i was talking about. i guess they cannot get any cheaper than that price ha? So, think about connecting 2 of those.

Spyros

[RonMicjan]

Right then, thats what I always do, take an idea for an field expedient temporary fix, then make it my normal routine, then find the cheapest batteries to use for it.

And we wonder why there are Darwin Awards.....sheeze!


ITS A TEMPORARY FIX, SAVE A DIVE, USE ONLY WHEN ABSOLUTLY NECESSARY TECNIQUE PEOPLE!

5-AA battery packs or 2-C 3.6v lithiums are the recommended battery packs for the Meg Apecs system. They give 3-6 month, or 6-12 month service, are easy to make, easy to order (from ISC) and the prudent diver will have extras on hand, aleviating the need for temporary fixes.

[Outlaw]

Quote: (Originally Posted by RonMicjan)

Right then, thats what I always do, take an idea for an field expedient temporary fix, then make it my normal routine, then find the cheapest batteries to use for it.

And we wonder why there are Darwin Awards.....sheeze!


ITS A TEMPORARY FIX, SAVE A DIVE, USE ONLY WHEN ABSOLUTLY NECESSARY TECNIQUE PEOPLE!

5-AA battery packs or 2-C 3.6v lithiums are the recommended battery packs for the Meg Apecs system. They give 3-6 month, or 6-12 month service, are easy to make, easy to order (from ISC) and the prudent diver will have extras on hand, aleviating the need for temporary fixes.

Hey Ron,

pricing was not the main factor to decide on this. it was just that i thought there maybe less failure points. instead of connecting 5 together, you have one single battery. if it works fine, and it last a bit, then why not?

What do you think on that?

Spyros

[Gilles]

Quote: (Originally Posted by RonMicjan)

5-AA battery packs or 2-C 3.6v lithiums are the recommended battery packs for the Meg Apecs system. They give 3-6 month, or 6-12 month service, are easy to make, easy to order (from ISC) and the prudent diver will have extras on hand, aleviating the need for temporary fixes.

There is necessity. ISC is a little more than a pissing distance away (something like 21,000 km, across the Pacific ocean, and a gauntlet of postal delivery, and customs agents. Ok Cyprus is closer, maybe only 15,000 km

Welding of batteries, especially Lithium ones, is hazardous in itself. They have a much lower temperature tolerance and should only be welded with a specialized tak welder. Proper Lithium C's need to get imported from Singapore, another gauntlet of post and customs. A real pain when you fry a cells trying to get a proper weld on it with a soldering iron. Normal AA cells have a somewhat higher tolerance, but I have had the rig re-set itself, all because of a bad weld.

Aknowledged however, is one should use the best cells available.

[RonMicjan]

I understand that shipping is difficult in many places and there is some skill involved in making up battery packs. I have made up several hundred AA packs and 50 lithium C packs so have had lots of practice. A tac welder is more than $1,000 so making the C lithium packs is even more difficult. I live a couple hours from ISC so when I make packs I do it using their welder, the best of all worlds. I might suggest getting a few guys together and ordering enough batteries for a year or two at a time, split the postal costs and the shelf life of AA alkaline is 3 years at least. Or finding one diver in your group (dont all meg divers travel in packs??) who has the skill to solder packs and do a bunch at a time whilst your mates buy the pizza and beer, but only let the tech drink beer after the work is done eh?

There are safeguards built into the Apecs that alert you when your batteries are getting low, backlight quits first, then the lo bat indicator comes on. Neither of these will work when you are using 9v batteries and you run the danger of a battery failing with zero warning, as in, during a dive. Using the correct voltage packs will allow the system to help you decide when its time to change batteries.

Anyway, you can do what you want, but I didnt want any lurkers to read your posts and decide that your idea was a great one without knowing the drawbacks.

Thats what I think...

y'all should have seen the 10-12 foot waves coming in over the Bar this afternoon, I was out surfing down the faces of waves in my 26 foot boat...yeee-hawww!

[wedivebc]

Quote: (Originally Posted by RonMicjan)

There are safeguards built into the Apecs that alert you when your batteries are getting low, backlight quits first, then the lo bat indicator comes on. Neither of these will work when you are using 9v batteries and you run the danger of a battery failing with zero warning, as in, during a dive. Using the correct voltage packs will allow the system to help you decide when its time to change batteries.

Good point. Never thought of that.

[jdicediver]

Quote: (Originally Posted by RonMicjan)

Using the correct voltage packs will allow the system to help you decide when its time to change batteries.

y'all should have seen the 10-12 foot waves coming in over the Bar this afternoon, I was out surfing down the faces of waves in my 26 foot boat...yeee-hawww!

Ron, you are right...again.

The ISC battery pack in my COPIS gave up the ghost on the coast whilst diving with Dave in July, and it was the lack of backlight that alerted me.

Ummm...didn't anyone tell you that small of a RIB isn't meant for surfing? Think you best sell it to me for around 15K and get something bigger. PM me and we can work out the small details...LOL

[Skipbreather]

Quote: (Originally Posted by RonMicjan)

y'all should have seen the 10-12 foot waves coming in over the Bar this afternoon, I was out surfing down the faces of waves in my 26 foot boat...yeee-hawww!

Hey Ron-

Narley dude, were ya hangin' ten?

As far as welding C lithium batteries there is an ultra simple solution: simply buy them w/ tabs already spot welded on. It costs all of $0.25 extra per cell, the tabs solder almost effortlessly, and they conduct very little heat into cell compared to direct soldering.

Ken