Old EPIRB batteries

[Moondog55]

I have 4 of these and after 10 years they still have more than 3 V showing on test. Panasonics service dept can't help [ or won't]
I want to arrange these is series to give a 12V power source to have a backup supply for my mobile phone and i don't have the time to arrange a stable 5V supply either. I'm wondering what's the best wire size to use as a solder on connection.
I'll silicon them to a sheet of something light first

[Maelgwn]

As they are not rechargeable - whats the point? They cant have very much capacity as an EPIRB is not exactly a high power device ... So you would just end up throwing them out after very little use?

IMO, any size cable would be fine. Think about how small the cable is on your phone charger - a similar size would be fine.

[Moondog55]

Good point. But as they were at the end of their life in the EPIRB the cost is nil.
Good point on capacity, I'll google it. In that case any of the wire I have here will do. Tabs were very easy to solder on anyway, just had to clean a little corrosion from one battery +

[Moondog55]

Reasoning is this way. No contact with boss I can't go
Old phone with limited battery life
5A/Hr capacity on the Panasonics, 1 Amp pulse and 300mAmp continuous
The cheapest way for me to get a stable 5V recharge supply was a phone charger through eBay for $4-[post included] which itself needs a nominal 12V input. The phone needs 2 hours @ 890ma so I should be able to top up the phone at least 4 times during my 3 weeks up there and it means I don't have to ski into the village and buy coffee and cake to use the 240V. I know it's not perfect or even ideal but it is what is with in my budget

[Maelgwn]

Wow - that is actually quite a bit of capacity. Be interested to see how much battery remains tho - assuming they are 5 to 10 years old.

Google suggests a minimum cross sectional area of 0.18mm2 - which even if we assume is wrong/not conservative enough and multiply it by say 4 still gives a cable size of whatever you have already will be fine

Also worth remembering that batteries have more capacity when discharged slowly than when discharged quickly.

[Moondog55]

Done

Quite quick to do really although the silicon needs a little extra time

[Moondog55]

I just put the package together and it works, and a LOT cheaper than the dedicated solar charger. This would work well with a pack of rechargeable AAs

[Strider]

They cant have very much capacity as an EPIRB is not exactly a high power device

Really? I would have expected it to take a fair bit of grunt to transmit something thousands upon thousands of kilometers into space near continuously for a 48 hours period?

[Moondog55]

300mA/h is quite a current for modern devices. I think all of these devices use a pulsed current which increases battery life.
With 5 A/Hr available the batteries should last a lot longer than 48 hours too.