D4 Lamp modification
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fmerkel
Contributor
You can put in a higher wattage bulb BUT it won't help much. The bulb defines the draw on the batteries but alkalines have to small a "pipe" (my term) to feed the higher demand of the brighter bulb.
That's why the D4R is rechargeable. The rechargeable batteries have the ability to feed the brigher bulb. If you open the battery pack of a D4R what you'll find is 4 x 4400 MAh (milliamp hours/high capacity) D-cells wired together.
If you buy similar cells and a decent charger you'll end up with the equivalent of a D4R. I have 1 UK400R (older single bulb model), and 2 UK400's I've converted over. The only difference in the water is the converted lights are just a tad more floaty, indicating either there is a little more airspace in the UK400 model or the batteries aren't quite as "dense". They perform exactly the same.
FWIW, I'm using Radio Shack 4400 MAh Nicads in one and 4400 MAh NiMh in the other. Total cost of the conversion including batteries, bulb and chip controlled charger (high end) was about $80. Half of that was the charger.
Don't be fooled by the cheap 2200 MAh D-cells in the drug stores. They aren't the same quality and won't make it through an hour long dive.
Fritz
That's why the D4R is rechargeable. The rechargeable batteries have the ability to feed the brigher bulb. If you open the battery pack of a D4R what you'll find is 4 x 4400 MAh (milliamp hours/high capacity) D-cells wired together.
If you buy similar cells and a decent charger you'll end up with the equivalent of a D4R. I have 1 UK400R (older single bulb model), and 2 UK400's I've converted over. The only difference in the water is the converted lights are just a tad more floaty, indicating either there is a little more airspace in the UK400 model or the batteries aren't quite as "dense". They perform exactly the same.
FWIW, I'm using Radio Shack 4400 MAh Nicads in one and 4400 MAh NiMh in the other. Total cost of the conversion including batteries, bulb and chip controlled charger (high end) was about $80. Half of that was the charger.
Don't be fooled by the cheap 2200 MAh D-cells in the drug stores. They aren't the same quality and won't make it through an hour long dive.
Fritz
Let me get this right.
If I put 4 high capacity 1.2V 4500MAh batteries into a UK C4, it should theoretically power an 18-watt bulb for just as long as the D4R would, right?
Would there any drawback to do this?
Also, if the MAh are equal, aren't the NiMH batteries better? ... because of the charge memory problem with NiCads.
FYI: I've seen rechargable D-cells with MAh as high as 8000 on line at: www.onlybatteries.com
If I put 4 high capacity 1.2V 4500MAh batteries into a UK C4, it should theoretically power an 18-watt bulb for just as long as the D4R would, right?
Would there any drawback to do this?
Also, if the MAh are equal, aren't the NiMH batteries better? ... because of the charge memory problem with NiCads.
FYI: I've seen rechargable D-cells with MAh as high as 8000 on line at: www.onlybatteries.com
Let's look at this a bit.
The "standard" bulb for the C8 is what - 10 watts?
So let's assume the C8R is 18 watts, as was noted for the D4R.
Ok. With 8 "C" cells @ 1.5V you have 12V. If the bulb is 10 watts you have a draw of 0.833 amps. This means that the total resistance in-circuit to get this flow of current is approximately 14.4 ohms.
Now we put in an 18W bulb.
If you have 4500 mah batteries, assuming you drain no more than 80% of the charge (good practice if you'd like the batteries to last!), you have 3.6ah of usable capacity in those cells.
With a D4 light, and an 18 watt bulb, you would have the following:
18 / 4.8v (NiMH batteries are 1.2v, not 1.5v) = 3.75 amps of draw.
You have 3600 mah of available capacity, so your burn time would be roughly 57 minutes, assuming you do not overdraw the batteries.
Now if you use 8000mah cells, then your burn time at 80% discharge is 102 minutes, or pretty close to 2 hours.
For the C8 light, the math works like this:
3500mah cells are the largest "C"s available. You have 9.6v of drive to the bulb. With an 18w bulb, you would have a draw of 1.875 amps. With a usable capacity of 2800 mah, you could burn that lamp for an hour and a half.
If you use a 10 watt lamp, then your burn time leaps to 2.7 hours with those cells - which is pretty doggone good!
Note that the "R" lamps may well be designed for a lower drive voltage, as the rechargable batteries have a lower voltage. What this means is that the light from a "standard" bulb may be more "yellow" when used with rechargables.
Also note that rechargables give little or no warning before going "dead". You won't get much time between noticing it getting dim and the lamp going out, and if you try to "push" the batteries you may reverse-charge one or more of the cells, which will reliably destroy it.
The "standard" bulb for the C8 is what - 10 watts?
So let's assume the C8R is 18 watts, as was noted for the D4R.
Ok. With 8 "C" cells @ 1.5V you have 12V. If the bulb is 10 watts you have a draw of 0.833 amps. This means that the total resistance in-circuit to get this flow of current is approximately 14.4 ohms.
Now we put in an 18W bulb.
If you have 4500 mah batteries, assuming you drain no more than 80% of the charge (good practice if you'd like the batteries to last!), you have 3.6ah of usable capacity in those cells.
With a D4 light, and an 18 watt bulb, you would have the following:
18 / 4.8v (NiMH batteries are 1.2v, not 1.5v) = 3.75 amps of draw.
You have 3600 mah of available capacity, so your burn time would be roughly 57 minutes, assuming you do not overdraw the batteries.
Now if you use 8000mah cells, then your burn time at 80% discharge is 102 minutes, or pretty close to 2 hours.
For the C8 light, the math works like this:
3500mah cells are the largest "C"s available. You have 9.6v of drive to the bulb. With an 18w bulb, you would have a draw of 1.875 amps. With a usable capacity of 2800 mah, you could burn that lamp for an hour and a half.
If you use a 10 watt lamp, then your burn time leaps to 2.7 hours with those cells - which is pretty doggone good!
Note that the "R" lamps may well be designed for a lower drive voltage, as the rechargable batteries have a lower voltage. What this means is that the light from a "standard" bulb may be more "yellow" when used with rechargables.
Also note that rechargables give little or no warning before going "dead". You won't get much time between noticing it getting dim and the lamp going out, and if you try to "push" the batteries you may reverse-charge one or more of the cells, which will reliably destroy it.
at my spare bulb for my C8 and it is plastered as "13.2 watts" on the package, and claims to be for both the C8 and C8R.
At 9.6v for NiMH or NiCAD batteries, this would put the draw at 1.375A.
For a 3500mah pack, 2800mah usable, this puts your burn time at roughly 2 hours.
For a 4500mah pack your burn time would be 2.6 hours, again, assuming use of 80% of capacity.
At 9.6v for NiMH or NiCAD batteries, this would put the draw at 1.375A.
For a 3500mah pack, 2800mah usable, this puts your burn time at roughly 2 hours.
For a 4500mah pack your burn time would be 2.6 hours, again, assuming use of 80% of capacity.
Aquamaniac
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I think what fmerkal was getting into (Im guessing), Is more related to Peak Power Capability, not so much the Ah capacity rating.
This is the maximum power a battery can produce for a short period without any degredation of terminal voltage (about 33% of the Open circuit voltage), Usually we test with a 30 second time base.
Basically even though your 2000mAH cell can produce 2 amps for 1 hour, It doesnt mean that you can produce 16 amps for 7.5 minutes.
Think of it like water, If you have 3000 gallon tank, with a 1/2 pipe in the bottom, you wont get 3000 liters per minute out of it, but if you have a 3 " pipe you will. Hence the "pipe analogy"
That being said, given the figures quoted, I doubt that your even close to the PPC for those cells.
Dave
This is the maximum power a battery can produce for a short period without any degredation of terminal voltage (about 33% of the Open circuit voltage), Usually we test with a 30 second time base.
Basically even though your 2000mAH cell can produce 2 amps for 1 hour, It doesnt mean that you can produce 16 amps for 7.5 minutes.
Think of it like water, If you have 3000 gallon tank, with a 1/2 pipe in the bottom, you wont get 3000 liters per minute out of it, but if you have a 3 " pipe you will. Hence the "pipe analogy"
That being said, given the figures quoted, I doubt that your even close to the PPC for those cells.
Dave
batteries have extremely low internal resistance.
What you're talking about, Aqua, is the cell's internal resistance. That is what controls the maximum discharge rate - the cell produces heat as it discharges from that resistance (the internal drop in the cell) which, if it gets out of control, will damage it.
Alkaline batteries have a relatively high internal resistance. NiCADs and NiMH batteries have an EXTREMELY low internal resistance, to the point that you can start fires or even get them to expode if you short them out and they are fully charged. Alkalines won't do that, primarily due to their higher resistance.
BTW, internal resistance is a fairly accurate negative correlation on self-discharge rate. The lower, the faster. This is why alkalines will last years on the shelf, but your NiCADs will be completely flat in two to three months in storage.
Both NiMH and NiCADs like to be discharged fully. The problem is that you can't do that in a battery pack, because there is always one cell that is weaker than the others (even if by just a bit). What happens is that the weak cell ends up becoming exhausted and it is reverse-charged - this is extremely damaging as it will almost immediately produce an internal short in the cell, destroying it. What this means is that ideally you would charge each cell INDIVIDUALLY (which none of the chargers do - most charge 2 cells in series, a few charge 4) which would top them off independantly. This inherent imbalance, by the way, is the reason for the 80% "safe" burn restriction - it prevents a reverse-charge on one of the cells. By the time you notice a light going yellow on you its a good bet you're impressing a reverse-charge voltage on one of the cells - bad karma.
NiCADs have the memory effect too which makes for russain-roulette - if you don't fully discharge, you drop their capacity over time! NiMH batteries don't have that problem and as such are "safer" in this regard. I recommend them over NiCADs for most applications for this reason - just be aware that the price for this flexability with discharge profiles is that they do have a shorter cycle life (number of cycles before they die completely).
Decent NiMH cells should tolerate 200 cycles or so before their capacity is degraded by more than 20% or so. NiCADs might get you 300. Considering that "C"s are roughly a buck a piece, and the NiMH 3500 Mah Cs are $7 or so in "no-name" brand, its not hard to do the math on them. If you get 10 cycles out of them you're ahead of the game. Get 20 and the charger is free
Occasionally NiCADs can be "brought back to life" after being abused if you have a BIG capacitor. You charge it up and good and then "dump" it into the battery. The HUGE current surge literally burns off the electrolyte material that is causing the short! You need to be careful doing this though - its not an entirely risk-free procedure; I think you can figure out the possible failure modes :boom: I have no idea if NiMH batteries are similarly amenable to this treatment; I've yet to kill one in this fashion.
What you're talking about, Aqua, is the cell's internal resistance. That is what controls the maximum discharge rate - the cell produces heat as it discharges from that resistance (the internal drop in the cell) which, if it gets out of control, will damage it.
Alkaline batteries have a relatively high internal resistance. NiCADs and NiMH batteries have an EXTREMELY low internal resistance, to the point that you can start fires or even get them to expode if you short them out and they are fully charged. Alkalines won't do that, primarily due to their higher resistance.
BTW, internal resistance is a fairly accurate negative correlation on self-discharge rate. The lower, the faster. This is why alkalines will last years on the shelf, but your NiCADs will be completely flat in two to three months in storage.
Both NiMH and NiCADs like to be discharged fully. The problem is that you can't do that in a battery pack, because there is always one cell that is weaker than the others (even if by just a bit). What happens is that the weak cell ends up becoming exhausted and it is reverse-charged - this is extremely damaging as it will almost immediately produce an internal short in the cell, destroying it. What this means is that ideally you would charge each cell INDIVIDUALLY (which none of the chargers do - most charge 2 cells in series, a few charge 4) which would top them off independantly. This inherent imbalance, by the way, is the reason for the 80% "safe" burn restriction - it prevents a reverse-charge on one of the cells. By the time you notice a light going yellow on you its a good bet you're impressing a reverse-charge voltage on one of the cells - bad karma.
NiCADs have the memory effect too which makes for russain-roulette - if you don't fully discharge, you drop their capacity over time! NiMH batteries don't have that problem and as such are "safer" in this regard. I recommend them over NiCADs for most applications for this reason - just be aware that the price for this flexability with discharge profiles is that they do have a shorter cycle life (number of cycles before they die completely).
Decent NiMH cells should tolerate 200 cycles or so before their capacity is degraded by more than 20% or so. NiCADs might get you 300. Considering that "C"s are roughly a buck a piece, and the NiMH 3500 Mah Cs are $7 or so in "no-name" brand, its not hard to do the math on them. If you get 10 cycles out of them you're ahead of the game. Get 20 and the charger is free
Occasionally NiCADs can be "brought back to life" after being abused if you have a BIG capacitor. You charge it up and good and then "dump" it into the battery. The HUGE current surge literally burns off the electrolyte material that is causing the short! You need to be careful doing this though - its not an entirely risk-free procedure; I think you can figure out the possible failure modes :boom: I have no idea if NiMH batteries are similarly amenable to this treatment; I've yet to kill one in this fashion.
Aquamaniac
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Yep, But I was just trying to keep it simple.....Not all of the readers want to get into the specifics.
Now if anyone wants more details, such as the formulas we use to calculate these I squared R losses, feel free to drop me a PM.
Dave
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