H/H GPS...batteries

Appleyard

Appleyard

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Evening all.
I have a basic H/H . It's a bit battery hungry,so I tried rechargeables in it. They don't last any time before needing recharged,I assume that this is because they are 1.2 V to begin with and thus the voltage falls below the required fairly quickly. Is there any better solution,eg is it possible to get 1.5 rechargeables? The rechargeables in question are fairly new ,so age is not the issue. Ant suggestions?
 
if it's just to be used on the boat, why not run it off the 12 volt electrics. i have power to mine from the boat electrics to the helm position. if need to plot down at the chart table just remove and run off internal batt's for a few mins.
 
Can you get a 12V lead for it?
Otherwise, look for cheapest AA Alkalines- 10 for £1.50 at IKEA...
You could get some tagged rechargeables and wire in a resistor and diode to 12V perhaps to trickle charge , care needed- one dodgy connection could put 12V on the gps...
I'd go for a 12V adaptor if at all possible, although you could buy a lot of AA's for the price unfortunately.
What model GPS is it?
 
I had a similar problem. I now use 12V on the boat and Costco's own-brand cheapies elsewhere; these last a lot longer than the much more expensive Duracells & similar.
 
Aidy I should have mentioned in my original post....I use it mainly off the boat......hillwalking etc. (so a 12 V source would be a bit heavy!!!!) However I was thinking about getting a 12 v adaptor for on- board use as a backup to the main chartplotter/gps Thanks
 
I use NiMh recchargeables for everything I can: if you buy high-capacity ones (AA sizes now up to about 2700maH capacity) they should last even longer on one chge than a throwaway Duracell or Energiser, though not as much as the stupidly expensive lithium batts.

The rechargeables you often see in supermarkets seem to be very low capacity - sometimes only 900 or 1300 maH. The other factor is that the cheaper chargers may not be very good - showing them fully recharged long before they really are.

If you use battery powered kit a lot (I do, though not just on the boat) NiMhs are the way to go. For stuff you use only occasionally they are not so good, as they don't hold their charge well for months or years. After 2-3 months they need a recharge even though they have not been used.
 
John does the fact that all rechargeables seem to be 1.2 V as opposed to 1.5 V for non rechargeables have any bearing on the life?
 
No - ordinary throwaway batteries start life at 1.5 volts plus but very quickly drop to 1.2 or so anyway, then gradually drop further till at about 1.0 to 1.1 volts they have too little oomph left to power anything properly. So most of the time nomilnally 1.5 volt batts are actually only putting out 1.2 or so anyway.

NiMhs start at about 1.3 to 1.4 charged, quickly drop to 1.2, but then hold up to that voltage for a long time, till they finally drop out quickly.

For a torch the voltage matters, so a torch with NiMhs will never be as bright as one with throwaways in, but for electronics such as VHFs or GPSs (or digital cameras and flashguns, which is where I use them a lot), 1.2 volts is fine to run them, and they will go for a long time if you use good batteries.

The higher the load the better off you are with NiMhs, excellent for high-power stuff that runs a battery down in 4-48 hours constant use. Rubbish for a low-power item like a clock that runs for five years on a Energiser.

A bit non-technical but that is the way it works in practice. I could probably do the technical but haven't got time now!
 
I use an Etrex and while I have a 12v connection for the boat I don't bother using it. Mainly cos I keep it around my neck. I have 2300Ah Ni M H rechargeables which seem to do a good job. I don't tend to leave the GPS running all the time but just turn it on when wanted. But I reckon it would last quie a while on the rechargeables. You might just need to carry a spare pair in case of battery failure.
Yes I agree with John the 1.2 v of Nimh lasts through virtually all the life of the battery wheras 1.5 volts of alkaline diminishes in a linear manner. So a rechargeable actually has a higher average voltage over the life of the battery. But when it is discharged it dies suddenly.

god luck with the walking olewill
 
I also run my etrex on NiMH 2700's and it seems to work nearly as well as if I use ordinary Duracell's. Note It pays to freshly charge your NiMH's before use as I understand they self discahrge over around about 3 to 6 months. So battery's charged at the begning of summer can not be expected to match Duracells left on board for use at the middle to end of summer.
 
[ QUOTE ]
John does the fact that all rechargeables seem to be 1.2 V as opposed to 1.5 V for non rechargeables have any bearing on the life?

[/ QUOTE ]
Yes it does - anything that attempts to monitor the battery level will struggle with rechargeables. So if I put a fully charged set of NiMH batteries in my HH VHF it immediately complains of low voltage. The same set of batteries made up into a rechargeable battery pack will run it for hours (because it has an additional sensor to tell it when it is using rechargeables, hence expects lower voltage).

Some HH devices do have a setting to tell it whether you are using rechargeables and adjust the voltage accordingly. Even so you can't really trust the battery level indicated for rechargeables as they have different discharge characteristics to alkalines.

The cheapest source of AA batteries I know is Maplins, they regularly have them on special offer. At the moment you can buy 100 AA for £12.50
 
I have a basic Etrex and get a full day - 15-18 hrs constant use- using 1500 or 2300 mAh NiMH from a full charge, no problem. Is your charger/batteries okay? - the only problem I ever had was a duff battery, didn't hold charge and power kept going off after an hour or so.
 
Many thanks for all the replies fellas. As usual ,plenty of good advice.I reckon I will get some 2500 nimh rechargeables and start using them. Off to the boat 3 weeks today!!!.
 
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