NiMH batteries in GPSR

[Guest progun]

I can only assume that many are using NiMH batteries in their GPSRs.

 

I would like to know how they hold up compared to normal akaline batteries.

[Guest SteveL]

Not as well if you use your GPSR infrequently (NiMH have a poor shelf life - they loose about a 1% or so a day). Also, since nominal voltage for a NiMH or NiCad cell is 1.2V (instead 1.5V), my etrex Legend shows 3/4 full batt. with a full charge. Other than that, I LOVE THEM! Other then the day I got my GPS, NiMH has been the only batt I use.

 

SteveL

[Guest ClayJar]

How do they hold up? MUCH cheaper!

[Guest ClayJar]

How do they hold up? MUCH cheaper!

[Guest k2dave]

get apx 19 hrs w/ alks and 12 hrs w/ nimh (1550 and 1600 mAh). don't mind using the backlight w/ nimh at all.

 

if your gps doesn't have nimh as a setting for your batts use alk - not nicd - reason is at the low end of the scale alk is closer to the true reading of nimh then nicds. if you use nicd you will get a low batt alert too soon.

 

try to recharge your batts a day or 2 before you want to use them - but don't let totally dead batts sit in the gps.

 

Also don't buy too many nimh batts - you want to have a just in time inventory system so you always have fresh batts. If you are just using them in your gps - get 2 sets - no more.

 

bring good alks as backup.

[Guest badbitbucket]

my GPS12 (uses 4-AA)

 

20-24hrs w/NiMh, no backlight.

 

About 10hrs w/recharagle alks, no backlight

 

20-24hrs w/energizer alks, no backlight

 

charge time for NiMh is about 12-16hrs when fully discharged.

 

I carry a set of disposable alks as backup, and sometimes I carry the rechargable alks when I know I'll be away from power for a few days.

-BBB

 

[This message has been edited by badbitbucket (edited 19 October 2001).]

[Guest k2dave]

badbitbucket are you using your gps's battery timer or are you estimating the 20-24hr time? If you are using nimh's and your gps does not have a nimh setting your bat. timer (if you have one) will most likely not reset and you will have to do it manually. Also when I stated the 19 hrs alk and 12 hrs nimh - those figures are accurate to within that one hr 90% of the time (i.e. 90% of the time alks will last 19-20 hrs, 10% of the time it will last more then 20 hrs or less then 19). You seem to have a greater variation (4 hrs).

 

It seems unlikely that you will get the same run time with nimh they alks even if you use the new 1800mah batts.

 

Please don't misunderstand me I am not calling you a fibber. I have done work on batts in the past and have a lot of experence with nicd, nimh, pb-acid and some with li-ion even theough the technology has changes a lot with that one; and am generally curious about batts.

 

Also do you use the batt saver setting on your gps (if it has one)?

[Guest ClayJar]

By the way, Rayovac has a new NiMH/NiCd charger out there that will fully charge a 1600mAh NiMH cell in 1 hour. It can charge up to four (4) AA/AAA cells at one time, and each one is charged individually. (You can stick a AAA and a AAA in there, add another AAA as soon as you find the darn thing, and put in the AA you found in the couch; there's none of this pairs/quads thing going on.) You can even get an optional lighter adapter to use it in your car.

 

It's the "PS4", and they have a product page on their site. It seems to be getting good word of mouth on news:sci.geo.satellite-nav (and charging 1600mAh in 60 minutes or less is sweet). Oh, and it comes with a pair of 1600s, and is available at the Wal and other places (see the link).

[Guest Point2Point]

...but be careful with rapid chargers. I have had poor results with a Radio Shack 1 hour rapid charger with some of my NiMH batteries because it seriously overheated them - and that ruined them. Too much juice in a short period of time = heat = fried batteries.

 

Here is the link to forum thread I started on this subject if you want to read more:

 

http://forums.Groundspeak.com/ubb/Forum13/HTML/000652.html

[Guest ClayJar]

There are other fast chargers around for AA cells, but most of them use one charge control circuit for multiple cells, and it's important that all of the cells monitored by a single control circuit are of the same type and state of charge so they reach full charge at the same time. This is not normally a problem if you have a "set" of 2 or 4 cells that you always use in your GPSR together, and always charge together. But if you have many devices that use NiMH AAs in varying quantities, you have to watch out for this.

 

The Radio Shack 23-410 "pulse charger" can charge 1-4 cells, but all are charged in parallel with a single charge monitor circuit. All the cells being charged at once should match, but you can charge 1-4 cells at one time. It can handle AAA through D size, plus 9 V.

 

The Maha MH-C204F has two completely independent charge circuits, each of which charges exactly 2 cells - which should match. So you can charge two "sets" of 2 cells independently, but there's no way to charge 1 or 3 cells. Each side can handle AA or AAA cells.

 

There is a compact charger sold by Kodak, Epson, and others which charges AA cells only. It has two independent charge circuits that each charge two AA cells in parallel. This allows charging 1 or 3 cells as well as 2 or 4, but the charge rate will be double what it normally is for the lone cell - OK for NiMH but too high for NiCd.

 

The Radio Shack 23-034 portable charger has a single charge circuit which charges either 2 or 4 cells in series. In the "2 cell" position, it just shorts across the two unused battery chambers. So you can charge 2 or 4 cells that match, but not two sets of 2 simultaneously, and not 1 or 3. It can handle AA and AAA cells.

 

In comparison, the Rayovac has 4 charge positions, each with its own charge control circuit and monitor LED, each of which can handle one AA or AAA cell. So you can load it with any 4 cells, any mixture of sizes, in any state of charge - as long as they are *all* NiMH or all NiCd (see below). Or any number of cells less than 4.

 

Also, most of the other chargers named above have a single fixed charge rate of 500-650 mA (for AA; less for AAA). This is safe for both NiCd and NiMH, and gives charge times of about 1 hour for NiCD and 2-3 hours for NiMH depending on capacity. The PS-4 has a NiCd/NiMH switch that changes the charge rate. I measured an initial AA charge rate of 850 mA on the NiCd setting and 1820 mA on the NiMH setting. It really does charge 1600 mAh NiMH cells in under an hour.

 

The charge algorithm seems to charge at the set rate for 30 seconds, then stop for 0.5 seconds while the controller measures something, then charge for another 30 seconds. Once full charge is reached and the LED goes off, the charger seems to continue to provide brief charging pulses at 0.5 second intervals - this is probably a trickle charge.

 

It does seem to work well. At the end of a full charge cycle, NiMH cells in the charger are quite warm, but not hot - by this I mean you can hold your finger on them indefinitely without being burned. In addition, it seems to be able to detect bad cells (it flashes the LED if it detects one). I tried charging all my rechargeables with it, and it complained about two of them. They were bad; probably dried out with high internal resistance (one was visibly leaking).

 

The charger is uglier than most, and it's one of the most difficult I've used to actually insert and remove cells from. It's large enough that I will probably take something else instead when travelling.

 

It operates from 12 V, so you can use it in a car if you want. It doesn't come with a cigarette lighter cord, but Rayovac sells this as an accessory - or you can make your own. In fact, it uses the same size DC input connector and polarity as the Maha MH-C204F, so if you've made a car cord for the Maha you can also use it for the PS-4. You may have to change to a larger fuse, though - the Maha needs 0.5 A, while the PS-4 needs 1.5 A maximum.

 

Finally, as an additional bonus, the PS-4 will charge 9 V batteries. It's supposed to take 3 hours or less for a NiMH 9V, and it seems to detect full charge and shut off early just as for AAs. Most of the other chargers above will not handle 9 V batteries at all, and the RS 23-410 charges them for a fixed time.

 

The PS-4 package includes two 1600 mAh NiMH AAs. They have a plastic or fibre insulator around the positive terminal, so they're safe for the eTrex battery springs.

 

I found one of these in Zellers, a large retail chain in Canada, at $70 CDN. But Active Electronics was selling the same thing for $50 CDN, so I bought mine there.

 

Note: Rayovac also sells a couple of other chargers that claim to charge rechargeable alkaline, NiCd, and NiMH cells. I recommend AVOIDING them. I've had two separate PS-1 chargers fail to shut off when charging NiMH cells, so I no longer use this charger for anything but alkalines. The PS-4 is designed for NiCD and NiMH *only*.

 

Dave

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[Guest morganw]

I use NiMH batteries in my MAP76 and it has sat unused for nearly a month before, and the batteries were still good.

 

What I want to know is WHY can I not get lithiom ion rechargeables in a AA/AAA form factor. These are the ultimate in rechargeable technology today yet you only find them as 'builtin' batteries. Does anyone know where to find them (and a charger)?

[Guest progun]

Thanks for all the posts, and the post about the Raovac charger.

 

One of my employees just bought the Rayovac unit and has been pretty happy with it so far.

 

Looks like it is time to head out and get one.

[Guest ClayJar]

quote:

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Originally posted by morganw:

What I want to know is WHY can I not get lithiom ion rechargeables in a AA/AAA form factor. These are the ultimate in rechargeable technology today yet you only find them as 'builtin' batteries. Does anyone know where to find them (and a charger)?

---

The main issue is that you don't get that much better life out of it. If battery life is that important to you, use alkalines. Otherwise, NiMH cells are almost as long-lasting, and among other things, they're much cheaper.

[Guest Gliderguy]

one set of 1600s I ran 3 times. The first time they were ever used they only got the same as a set of broken in 1300s. the second and third times they ran 16:17 and 16:40 respectively.

 

I tried using the Alkaline setting for the battery type, but the INSTANT you get the low battery warning the unit shuts down. I mean the act of acknowledging the warning seems to shut the unit down. Using the NiCd setting gives the warning in a more timely manner, with maybe an hour of useful juice left. Using NiCd kept the battery meter pegged at full for several hours before it started dropping, where using alkaline would have it be at about 80% initially and drop to 50% and hold FOREVER. Then it would quickly drop to 0% once it started down from about the 50% mark. NiCd seemed to track proportionately once it actually started down, with no serious change in the rate it dropped on the meter. The battery type setting didnt seem to affect unit runtime, It just affected the low battery warning voltage and how the battery meter was scaled.

 

[This message has been edited by Gliderguy (edited 20 October 2001).]

[Guest k2dave]

I guess the low bat. point is not the same between units - so the best thing is to try out both and see what you like better. for me the nicd setting is pegged at full for the 1st few hrs then starts falling - when i get to about 1/4 power left (about 3 hrs run time left) I get the low batt alert. Sometime it comes up multiple times which gets anoying.

 

using the alk setting I get a reading of 90-100% on freshly recharged nimh and about 70-80% on week old nimh's. it quickly drops to 1/2 and holds for about 1/2 it's useful life then slowly decends. Low bat alert comes in at about 20-40 min useful running time remaining.

[Guest TeamCNJC]

quote:

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Originally posted by progun:

One of my employees just bought the Rayovac unit and has been pretty happy with it so far.

---

 

I purchased the Rayovac 1-hour charger and it fried 4 batteries - too hot to touch and shrinking/peeling lablels. I contacted Rayovac who advised me to send the unit in - 2 days later, I had a new unit, plus new batteries. It was still a PS4, but the label on the packaging said PS4-B! It works fine, and the batteries get warm during charging, but not hot. I'm going to find/buy/build a car adapter for the unit, but since a single pair seem to last most of the weekend, I'm not sure that I need to. -Craig

[Guest st_richardson]

I use NiMH mostly to save money. I use the charger that came with my camera. I keep 3 sets of NiMH batteries. (labled G1, G2, & G3)

Use time is not as important that way. (I do try to have a backup set of disposable batteries, also, since their shelf life is better.)

 

I also plug in to external power at home & in the car.

 

quote:

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Originally posted by progun:

I can only assume that many are using NiMH batteries in their GPSRs.

 

I would like to know how they hold up compared to normal akaline batteries.

 

---

[Guest progun]

quote:

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Originally posted by TeamCNJC:

I purchased the Rayovac 1-hour charger and it fried 4 batteries - too hot to touch and shrinking/peeling lablels. I contacted Rayovac who advised me to send the unit in - 2 days later, I had a new unit, plus new batteries. It was still a PS4, but the label on the packaging said PS4-B!

---

 

I picked up the Rayovac unit this weekend. It also is a -B model. Things went fine with the charge. My Magellan 315 reports about 3/4 battery life with the freshly charged batteries. I carried a set of backup akalines on my caching trip this weekend, but they were not needed. After the whole weekend, the batteries are still reporting as being 1/2 good. I will carry the GPSR around with me this week and see how long it takes.

 

So far I am pretty happy with the charger and the life I get from the batteries.

 

Scott

[Guest SteveL]

quote:

---

Originally posted by morganw:

What I want to know is WHY can I not get lithiom ion rechargeables in a AA/AAA form factor. These are the ultimate in rechargeable technology today yet you only find them as 'builtin' batteries. Does anyone know where to find them (and a charger)?

---

 

Lithium-Ion cells are 3.6 Volts - no good for the AA/AAA form factor (which is 1.5V). NiCad and NiMH are around 1.2V - a little low but OK. This is why freshly charged batteries generally do not show "full" on your GPS's batt meter, unless it has a NiMH setting.

 

SteveL

[Guest k2dave]

The Li-ion cell would have to be double lenght or width to actually work most of the time. I know my 3+ can opperate anywhere from 4-30 vdc but not sure it can handle 3.6x4= 14.4 VDC from the battery compartment instead of external power.

 

Another option is the use of a dummy battery that could allow a 3.6v cell along with a 0v 'dummy' battery. But in general consumers are too law suit happy to risk putting out 3.6 v cells.

 

what is the voltage of a disposable LI-ion batt?

[Guest SteveL]

time under low drain at several times the cost of Alkaline - not worth it in my opinion. I don't know what my Garmin Venture draws, but is not all that much.

[Guest CharlieP]

Does anyone know what the service life of NiMH cells are, considering a low cycles per year rate? They are supposed to last 300 to 500 cycles, but if you only cycle them 40 times a year, and don't abuse them, how long will they last, 3 years? 5 years? I know the answer for nicads, it's about 4 or 5 years, although it varies some depending on the quality of the cell. And if you consistently ovecharge nicads, it will kill them quickly, I think the same is true for NiMH.

 

CharlieP

[Guest joshuabrand]

Does anyone know how NiMH works in the cold? This is a major concern up here in North Dakota, as we experience sub-freezing temperatures about 3-4 months out of the year.

[Guest peter]

NiMH cells do lose capacity in the cold like alkalines and NiCds. Lithium cells retain the best performance. However, the LCDs in GPS receivers also suffer from poor performance in the cold, so it may be best to use an external antenna and keep the receiver inside your jacket most of the time.