Battery suggestion for handheld unit?

[Joseph]

I'm making a handheld unit and the enclosure that was dictated to me does
not have a battery compartment door on it...so I have to use internal
rechargables. my. The unit will get used 1hr/day, 5V @120mA, so my initial
thoughts are to use 2 or 3 AA in series. The product life needs to be 5
years without having to open the unit and replace totally dead batteries.

Anyone know if the Sanyo NiMH Eneloops (low self discharge) will last 5
years with proper care? How about the idea of just trickle-charging (C/10)
the batteries overnight? A 13 hour timeout is still recomended for safety
reasons - is there an easier way to do the timer than a separate processor?

Li-ion are $$. Are they so 'good' you recommend them?

Are pre-made battery charger OEM circuit-boards available? Somethng powered
from a cheap wall-wart.

thanks in advance

 

[Charles Schuler]

I'm making a handheld unit and the enclosure that was dictated to me does
not have a battery compartment door on it...so I have to use internal
rechargables. my. The unit will get used 1hr/day, 5V @120mA, so my initial
thoughts are to use 2 or 3 AA in series. The product life needs to be 5
years without having to open the unit and replace totally dead batteries.

Anyone know if the Sanyo NiMH Eneloops (low self discharge) will last 5
years with proper care? How about the idea of just trickle-charging
(C/10) the batteries overnight? A 13 hour timeout is still recomended for
safety reasons - is there an easier way to do the timer than a separate
processor?

Li-ion are $$. Are they so 'good' you recommend them?

The 5 year issue is going to be a problem. I like NiMHs (perform well and
cost-effective) but I don't think you can count on 5 years. Li-ions are
often rated at a maximum life of 3-4 years, even if not used (unless stored
at a low temperature).

 

[Eric R Snow]

I'm making a handheld unit and the enclosure that was dictated to me does
not have a battery compartment door on it...so I have to use internal
rechargables. my. The unit will get used 1hr/day, 5V @120mA, so my initial
thoughts are to use 2 or 3 AA in series. The product life needs to be 5
years without having to open the unit and replace totally dead batteries.

Anyone know if the Sanyo NiMH Eneloops (low self discharge) will last 5
years with proper care? How about the idea of just trickle-charging (C/10)
the batteries overnight? A 13 hour timeout is still recomended for safety
reasons - is there an easier way to do the timer than a separate processor?

Li-ion are $$. Are they so 'good' you recommend them?

Are pre-made battery charger OEM circuit-boards available? Somethng powered
from a cheap wall-wart.

thanks in advance

I've been looking at Li Ion batteries recently as NiMH replacements.
Different sellers rate their lifetimes different. Their self discharge
is considerably less than NiMH chemistry. Especially after the
batteries are a couple years old. Li Ion can also be charged no matter
how discharged they are (or are not), NiMH batteries cannot. Li Ion
also have a higher capacity by weight and volume. There several
companies making and selling charging ICs for cheap. Note that some
batteries do not come with over discharge protection. However, ICs are
available cheaply to remedy this also. After all the research I've
done NiMH batteries lose in the final analysis. Over the lifetime of
the battery they are more expensive to use.
ERS

 

[Rich Grise]

I'm making a handheld unit and the enclosure that was dictated to me does
not have a battery compartment door on it...so I have to use internal
rechargables. my. The unit will get used 1hr/day, 5V @120mA, so my initial
thoughts are to use 2 or 3 AA in series. The product life needs to be 5
years without having to open the unit and replace totally dead batteries.

Anyone know if the Sanyo NiMH Eneloops (low self discharge) will last 5
years with proper care? How about the idea of just trickle-charging (C/10)
the batteries overnight? A 13 hour timeout is still recomended for safety
reasons - is there an easier way to do the timer than a separate processor?

Li-ion are $$. Are they so 'good' you recommend them?

Are pre-made battery charger OEM circuit-boards available? Somethng powered
from a cheap wall-wart.

thanks in advance

Find an old-style "cordless" phone, and hack into it to see how they
do it. I've had one where the battery lasted about 5 years, but it
was on trickle charge all of the time I wasn't using it. It used a 3-cell
(about the size of AA cells) NiCd pack.

Good Luck!
Rich