F5 batteries

[Nap]

Hi - two F5 questions really. At what point on the battery meter do you change the batteries? If the voltage is dropping but most segments are filled is it still working at peak?
Second - can you use rechargeables ? Was thinking that with rechargeables I could change batteries when I lost a segment so that it was always running at full voltage...

anyone know?

Thanks

 

[crusher28]

I change mine when 2 bars left and use them in something (like a clock). In my manual it says not to use rechargeable????

 

[BH_Landstar_]

I use these in my F5 and F4. They work well and last well over 10 hours. I've yet to see them drop to 4 bars after 12 hours of use.

 

[Nap]

Thanks guys. Had another look at the manual and it doesn't say do not use rechargeables it says use only alkalines. Now they could mean use only alkalines or they could mean don't use the cheaper zinc chlorides ..... and although they mention the battery graph they don't say what it means (as in, when do you change them) - though they do mention that the F5 will run on one battery .... hhmm ... nice to see at least one person using rechargeables - cannot see why not ... hhmm .. shall write Fisherlabs and ask them - will post back.

Thanks

 

[Roland58]

9v rechargeable batteries (Nickel Metal Hydride, NiMH) have a pitiful mAh (milliampere hour) rating. That is probably why they don't recommend using them. Also, the voltage really doesn't diminish as the batteries discharge, the amperage declines (think of amperage as what pushes the electrons through the conductors). Operating on low amperage would certainly impact performance.

 

[Alimo88]

the batteries pictured have a mA/Hour of 280 that means you can draw 280 mA for one hour, or 140 mA for two hours, or 70 mA for four hours. I figure If someone is getting 10 hours that would mean the Machine draws about 25mA. Because the stated voltage is "Nominal" they actually charge to a lower Volt value. Maybe about 8.2V (not too sure and can't be bothered looking it up).
So maybe only three bars will ever light. My guess is the power supply might be 5v? so add a couple of Volts for the transistors and diodes and smoothing give about 7v, and again a guess, you would probably be replacing them above the 7V. so lets say at 7.5 Volts the machine will run perfectly. mA rating is an indication of the amount of time available for a given current draw. Ergo, less current, more time. More current, less time.

 

[Roland58]

+1 with alimo88. Basically, what I was trying to say......he just did a better job of it. Oh yeah, the voltage rating for the NiMH rechargeables is 8.4v, you were very close. The big thing I failed to mention is that the mAh rating for an alkaline 9v is normally around 580 mAh (you can get higher), so you can readily see, based on what alimo88 has said, that they will last a LOT longer. I don't think you would hurt anything by running the rechargeables, but, you would be changing batteries frequently and could possibly experience diminished performance as a result of the rapidly declining amperage.

 

[Nap]

Ok - so if the average alkaline 9v is 580MaH and the F5 manual says batteries last on average 40 hours then 1160 MaH divided by 40 = F5 draws about 29Ma per hour .... and the manual also says that it can run with one battery - which suggests that it isn't voltage the machine is looking for but Ampage .. though.... we aren't looking at dead batteries at the end of that 40 hour useage are we .. or are we?

I find that my batteries drop to 7 volts within ten hours of detecting .... am waiting for Fisher to reply about when to remove them ..

so, two 280Mah rechargeables ... 560MaH ... is just about the one battery that Fisher says it can run on, and that is a fully charged one and it will drain those as quickly as it would running on one fully charged alkaline? ... hhmm ... unless I can find 580MaH rechargeables I think I shall stay with alkalines and buy lots of clocks to put the batteries in that I take out that still have low useage usability ..

thanks for all these responses - this is good fun.

 

[Alimo88]

@Nap
Forget your amps theory
You need to be above a specific Voltage, The circuit is voltage dependent.
look at discharge curves for different types of batteries and you will see that once they start to roll off from their Nominal voltage it's all downhill quite quickly. More so for re-chargeables.

I have never seen the part in the manual that mentions running on one battery.

In regards to amps. A power supply needs to be able to supply the current draw required by the device used. Digital cameras are HIGH draw devices and hence flatten batteries quickly.
You can't draw 4 amps from a 2 amp power supply. A battery is somewhat unlimited in it's ability to provide current. I guess you could draw 5 amps from a battery. It would run out real quick and get real warm but it would do it. Your 9 volts are rated well above your current draw requirements so no problem there.

you calculated 29mA and I calculated 25mA so we might be close hahahhahah

 

[Nap]

Ah - this is what happens when I try to use arithmetic to understand an electrical question! (Which is why I asked).

So ... back to rechargeables. If I buy four or six of the highest MaH I can get and keep an eye on the voltage I can insert fresh ones as soon as there is a, say, 2-bar voltage drop - keeping optimum performance and minimum expenditure (once I've bought the kit) as well as no need for countless increasing number of clocks all over the house?

Sounds good.

Re one battery ...

Issue 2010 F5 manual, page 22, "Unit Specifications:" "Batteries: two 9 volt rectangular alkaline (will run on one)".

 

[Alimo88]

Your maths is fine. we came to a similar mA value from different directions
The detector should work fine until the last bar maybe even with the last bar flicking on and off.
nothing to be gained by changing them any sooner
9 volts over here (Australia) are 28 bucks a piece and the charger is about 50 total cost 162 dollars. I can get about 100 standard batteries for that price.
fully 50 sets.
if it works on one battery the batteries must be in parallel. Therefore the Voltage remains the same (9V) but the total mA hours of running time is doubled
PS MAKE SURE they actually fit in the detector some can be a touch large

 

[Roland58]

I know the F75 uses the AA batteries (four), but, I wanted to relate this story. I bought eight NiMH rechargeables, 2500 mAh rating, charged them fully and put them in my machine. Let me start by saying the alkaline batteries that came with my F75 lasted well over 40 hours (fairly close estimate based on how many trips I made). The NiMH batteries lasted two hunts that totaled approx. 7 hours! And once these babies begin to show a decline on the battery meter, they go down fast! I know you are talking about the 9v batteries, but, with the lower mAh ratings, I would be a little concerned about how long they would work before needing to be replaced.

If you do use these, please, report back on how long they last in your F5. Thanks.

 

[BH_Landstar_]

I've used the batteries as pictured above for 4 days now @ 2 hours each time and they still read as full, I've not charged them for over a week now. I don't have much time to detect during the day due to working 10 hour days. I'll run them til they start to fade and report back here on the outcome.

 

[Roland58]

I've used the batteries as pictured above for 4 days now @ 2 hours each time and they still read as full, I've not charged them for over a week now. I don't have much time to detect during the day due to working 10 hour days. I'll run them til they start to fade and report back here on the outcome.

They have already outlasted the 4 AA batteries in my F75!!!

 

[Nap]

Try Ebay UK, you can get good 250MaH pp3 9v rechargeables for

 

[Nap]

And then, thought I, ... one could get round the possible ampage problem of pp3 rechargeables by setting up two boxes of six AA's in series so that each gives 9volts and making up two dummies with pp3 connectors on fly leads at the end to insert into the battery box .. then strapping the AA boxes to under the armrest -

Thing is .. you can get 280 MaH pp3's but 2,700 MaH AA's .... so that would be a stunning amount of amperage at the correct voltage

And as the F5 is just a little coil heavy, there may be better balance? ... or am I missing something?

 

[BH_Landstar_]

I've yet to find mine coil heavy with the standard coil, I've yet to try it with the 11" DD tho.

I used the F5 last night, the voltage was still reading full after an hour out with it, not been out today so I can't report any extra info at the moment.

 

[BH_Landstar_]

Update

I managed to get out this afternoon for 4 hours, the voltage as dropped to 8 volts on the F5 after 15 hours of use from the batteries (see below), it's still doing good at the moment with them, I've not noticed any side affects yet.

Thats 15 hours from them without a recharge. Will update as soon as I can with more info.

 

[Roland58]

Thanks for the updates, BH. I'm certainly glad these are working out for you. The AA's in my F75 just don't hold up long enough to be worthwhile, but, it looks like these may pay off for you......very good!

 

[marcomo]

I've yet to find mine coil heavy with the standard coil, I've yet to try it with the 11" DD tho.

With the stock coil or the 5", the F5 is ergonomically just fine IMO.

Put on the 11" and the performance improves but it does get a little bottom heavy, although not enough to get me to take off the 11" for the majority of the F5 hunting I do.