Garmin VHF Battery^

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MikeB
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Garmin VHF Battery^

Post by MikeB » Wed Oct 19, 2005 6:52 pm

The NiCad for my 725 has put its legs in the air and died! Probably the combination of not using it and then leaving in the charger for 3 days (duh!) didnt help it much either.

So - a new NiCad is £30 - or I could get another NiMH at £62 - but before I blow that much dosh it strikes me that of course I also have the AA battery tray! Now, were I to buy some nice 2700 rechargables, that would be cheaper - - -

But, can any of our electronic tech specialists give me some idea of performance / battery life between the NiMH and a set of AA's?????

Mike.
Last edited by MikeB on Fri Jun 02, 2006 9:33 am, edited 1 time in total.

John W
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Post by John W » Wed Oct 19, 2005 7:24 pm

Mike

Can't say I've got around to trying my 725 with AA's yet. But whichever route you take, I've found both the following companies very good customer service and good prices also:

Garmin 725 -- http://www.offroadstore.co.uk

AA rechargeables -- www.picstop.co.uk

John

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MikeB
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Post by MikeB » Wed Oct 19, 2005 8:19 pm

Cheers John - I'm intrigued as to why an Off-road store is selling MARINE vhf - - - - (illegal to use on-land and all that)

Mike.

Chris Bolton
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My batteries also

Post by Chris Bolton » Wed Oct 19, 2005 10:05 pm

I was about to post similarly; both the Ni-Cad and the Ni-Mh battery pack for my Garmin 725 have ceased to hold charge. I am guilty of leaving them unused for a while, although not of leaving them in the charger for more than about 7 hours. It doesn't say in the manual how long they should be charged for (except 12hrs when new), or whether the charger protects against overcharging.

I have an AA tray, but it seems to have an intermittent fault and the set sometimes report it as flat even when filled with brand new duracells; fiddling with it causes it to work just long enough to contact the coastguard but not long enought to talk - embarrassingly.

I had a problem last year where the screw holding the battery pack corroded in place (on closer inspection it's outside the seal). When I eventually freed it I treated it with a small dab of vaseline. Although it's nowhere near the contacts, cleaning this off seems, accountably to me, to reduce but not eliminate the problem of intermittent aparent flat batteries.

Anyone able to report a 725 that has working batteries?

Chris

John W
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Post by John W » Wed Oct 19, 2005 10:21 pm

Chris

My 725 still has working batteries after nearly 2 years, it sounds like I may be the lucky one.

Mike

Not too sure myself why Patriot Offroad have VHF for sale either... But then he was extremely helpful too me when my first unit had a problem whilst I was in the South Atlantic. He also got me an extra car charger free of charge, has to be recommended.

John

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MikeB
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Post by MikeB » Thu Oct 20, 2005 2:31 pm

These folk have 1 NiCad left - just bought one at £15 which seems reasonable. The NiMH's in their ad have all gone, sadly!

http://www.boatsandoutboards.co.uk/view/BMB219/

Chris - had the same problem - I now use a little Copaslip (used for back of brake pads to stop sqeaks, and as anti-seize on bolts etc). Halfords and the like sell it, or your local garage might give you a small quantity.

The death of the NiCad appears (i'm told) due to it having been seriously overcharged - seems the Garmin charger doesn't cut-out automaticlally and will fry the battery.

Mike.

Chris Bolton
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Copaslip

Post by Chris Bolton » Thu Oct 20, 2005 11:30 pm

Mike,

Thanks for the suggestion of Copaslip; I take it that worked OK for you, and I think you must have posted it previously. It was the first thing I tried and I found it to have the worst effect on the apparent battery performance. Vaseline was not as bad, and Boshield T9 seems to have much less.

Chris

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MikeB
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Post by MikeB » Fri Oct 21, 2005 12:14 am

Interesting. I shall strip the dud NiCad tomorrow and report back on whether there's any connection between the screw and the rest of the battery.

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MikeB
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Post by MikeB » Fri Oct 21, 2005 2:55 pm

Well, some delicate surgery involving an engineers vice, a 5lb lump hammer and a hacksaw reveal no connection between the retaining screw and the internal battery gubbins! The screw is a captive fitting in the base of the battery pack, but its only a flange and other than carrying the screw and the charge terminals doesn't do anything electrical as far as I can see.

The battery pack is made up of 6 AA cells with interconnecting strips between the individual cells and a couple of wires leading to the charging terminals on the base.

Perhaps the constant fiddlying with the pack to remove / apply some form of anti-seize to the screw, resulted in a dodgy internal connection being improved, albeit temporarily. Certainly Copaslip on the actual terminals would degrade connectivity, but thats not what you were doing.

All of which suggests that careful dismantling of the battery pack (cut off the outer cover) and replacement of the cells (would require some soldering) MIGHT allow a pack to be rebuilt, assuming one knew what type/spec of cells to buy.

I suppose. But not this one, 'cause it's well knackered now!

Mike.

Chris Bolton
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Battery internals

Post by Chris Bolton » Fri Oct 21, 2005 6:27 pm

Mike,

Thanks for that; interesting, as you say. I'll keep the forum posted if I find anything else out.

Chris

Neily
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Garmin 725

Post by Neily » Fri Oct 21, 2005 7:23 pm

Mike, I've had very good results with the 2500mAH Uniross batteries in the 725. The batteries were obtained on ebay - miles cheaper than elsewhere including Maplin. The secret with the uniross AA's is that they need a good few charge and discharge cycles before they start to become worthwhile. I use a delta V charger. Mine now perform really well. The next thing you need to do is fool your garmin that it has normal alkaline AA's in so that the radios battery indicator works correctly. To do this you need to bridge two of the three contacts inside the radio. I'll be specific here because you don't want to get it wrong. Take the 725 battery pack out and look inside at the three sprung contacts with the keyboard upwards. You need to bridge the two contacts on the left hand side when the pack is inserted. I did this by sticking some conductive foil to the top of the battery back so that it contacts the bottom AA cell in the series pack (top left one) and sits halfway across the top of the battery pack so that when pushed home it makes a connection with the middle sprung contact in the radio. You'll find you get many days worth of life out of the 725 using these rechargeables. One charge did us for the Scillies this year. I also keep a backup 6 cells in reserve. Hope this is useful. Post back if not clear.

Neil.

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MikeB
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Post by MikeB » Sat Oct 22, 2005 11:41 am

Fascinating - do you know why this "mod" is necessary to make the indicator work???

Mike

Dave Thomas
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Post by Dave Thomas » Sat Oct 22, 2005 11:07 pm

Presumably because 6 NiCads/NiMHs give 7.2V whereas 6 alkalines give 9v (both 'nominal' values, of course)

Dave Thomas

Neily
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Post by Neily » Sun Oct 23, 2005 8:46 am

Correct.

Neily

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