7.3 volt power source for an SD2200d.

Hi guys (& gals),
Got a 12v to 7.3v regulator on the SD machine, but the 12v batteries are quite heavy. Looked at the Coiltek Li-Ion Regulated System, but the cost is about $405. Thought to myself, does it really need a regulator? Why can't I connect the battery direct? It would need a regulator to cut it to the 6.7v needed for the GPs, but for the SDs as they need about 7.3v, does it really need any sort of regulation between the battery and the detector?
A possible reason why it may need one, and I'm only guessing here, is that the battery might charge to over 7.3v (maybe as much as 8.3v at full charge) and then it would be not good for the SD. So designing a small system to keep the voltage at 7.3v would be a safety net. So what is needed is one that limits the volts to 7.3v at the output when the battery is about that, but doesn't drop too much voltage in the circuitry so when the voltage of the battery gets close to 7.3v, it does very little limiting. Otherwise if this curcuit used even 1v in its process, then as the battery dropped to 7.3v, the output to the detector would be 6.3v....not the desired effect.
Does anybody have any suggestions, or has anyone looked inside the Coiltek Li-Ion Regulated System?
Many thanks in advance

Hi Costesdee
If your battery is one of the bigger ones, 7aH or bigger then it will be pretty heavy. You can easily cut back the weight by using a half size battery that will give you about 5aH and weighs not much more than half the big one, and a lot less than the original 6 volt battery that came with the SD. 5aH will give you about 4 to 5 hours detecting time.

And yes, you definitly do need a regulator. The 12 volt battery will be about 12.8 volts when fully charged and this will cause your SD to shut down - if you are lucky. If not it will do some serious damage.

I found that by using the 5aH all morning then topping it up at lunchtime it would give me what I reckoned was a full days detecting. If you want more time detecting buy two 5aH batteries and change them over at lunchtime, they only cost about $35 wired up and ready to go from the Coiltek Gold Centre. Give the guys there a ring on 03 5460 4700 and see what they have in stock.

But seriously, do not connect your SD direct to a 12 volt battery.

Cheers, Jim

Cheers, Jim

Thanks for your reply Jim.
I do think I didn't explain it right. I wasn't going to connect the SD straight to a 12 battery. My idea was to replace the 12 battery with a 7.2-7.4v Li-Ion battery, similar to the one Coiltek sell in their "Coiltek Li-Ion Regulated System". That system uses the 7.2v battery and has a switch for you to sellect 6.7v ot 7.3v. I'm saying, I'm starting with a 7.2v battery, why do I need regulation for the SD that's good for 7.3v? I understand the GP needs regulation to get the 7.3v battery down to 6.7v, but why does the SD? Except for the reason I gave above, (the over charge when just out of the charger) and tat's what I'm trying to find a simple solution to. Hope this clears the confussion.
Many thanks again Jim.

You are on the right track but you will need a bit more than the 7.2v to 7.4v as the regulator needs about 2 extra volts higher to operate on. Just add another Li-Ion batt and get it up around 11 volts or so and then use a regulator.

I made up this one a fair while ago to run a GP extreme on. It has a trim pot that you can adjust to your desired voltage. The full charged battery voltage was around 12 volts and then the regulator dropped that down to around 6.8 volts. I could get all day and then some from a charge




cheers dave

ps: If you start with a 7.2 volt or 7.4 volt battery you probably wont need a regulator, but you will find it will soon drop below that. Also a battery of this voltage will charge to about 8.1 volts or so when fully charged and this is where yuo will get into trouble as the voltage is to high for the detector when fully charged.

Note: a battery is rated on its flat volts not its charged volts so a 6 volt battery for example is in theory flat at its rated 6 volts and is fully charged at around 6.8 volts.

Thanks for the reply Davsgold. Now I do agree with you that every curcuit I found seemed to need 2-3v more in that out. Hence to get 7.3 out, you'ld need about 9.5v or more in. My question then is how does the Coiltek system work when they use 1x 7.2v battery to achieve their goal? It mustn't be regulated on the 7.3v switch position and possibly have diodes on the 6.7v switch position (to drop it down the .6v). Unless they have a really good curcuit that does what I was asking in the initial question...
Cheers again

PS I do like your design and I'll probably do a similar one if I cant find a way to do it with the one battery..

PSS Thanks for explaining the voltage rating for batteries. I didn't know that, but I should've realised it as it makes perfect sense. Cheers again.

I know what your saying about the Coiltek setup, and I guess they use a diode for the drop down instead of a trim pot type system. then they rely on the 7.2v battery actually charging up to around 8.0 or a bit more when fully charged.

As the 7.2v rating is in theory their flat voltage. You just need to add battries in parellel to get the required A/H so for example a 7.2v 4a/h times 2 will give you 7.2 volts for 8 hours at a draw down rate of 1a/h per hour.

Mostly I found that the detector will use about 0.8a/h per hour.

cheers dave

Thanks again davsgold. 2 batteries are good, but it could be done with one and changed at about the 4 hour mark (lunchtime ). What I was thinking is getting the following
http://cgi.ebay.com.au/NP-F970-Battery-BC-V615-Charger-Sony-FX1-Z1U-SC55-/250743250859?pt=AU_Cameras_Digital_Video_Accessories&hash=item3a61765fab
and the following
http://cgi.ebay.com.au/AU-AC-Battery-Charger-Sony-NP-F770-NP-F960-NP-F970-/170486878322?pt=AU_Cameras_Digital_Video_Accessories&hash=item27b1cf5072
and then gut one of the chargers and instal a switch, a diode, some velcro and the correct wiring to the detector and headphones, and I've made my own power supply. I put it on the forum to see if there where any mistakes in my reasoning, or if anyone new of a circuit that was similar to the one I asked about earlier in the discussion.
Cheers again

PS And all for under $100

Hi CostasDee,

Have a look at these batterys,
http://cgi.ebay.com/Hi-Capacity-Battery-Canon-BP-970G-XH-A1-XL1-S-XL-1S-/190517396494?pt=Batteries_Chargers&hash=item2c5bb8c40e
You would also need to look out a charger. Make sure the ones you buy use Japanese cells not chinese cells.
They charge up to about 8.4v, which is fine for an SD. If you wanted to drop the voltage a little, use a diode in series with the power output from the battery. The other thing you will have to do however is bypass the battery protection CCT as the current that is drawn by the detector when you initially turn it on is high and the protection CCT will fail. You will need to also add some sort of fuse(2A) or thermal breaker as close to the battery as practical.

This is a battery that I have bypassed the protection cct on.


I don't know if this will be any use to you but I hope it helps!

Cheers Mick

Cheers and thanks for your reply Mick. Although I would definitely agree that Japanese cells would be better quality than Chinese, there sometimes is a big difference in price between the 2 nations. I will definetly look for the Japanese cells, but may get 1 or 2 Chinese cells to experiment with.
Cheers again

The link that I gave, is for a battery that does have Japanese cells. By the time you land it here it will be about $45. There are other cheaper chinese ones you can get that will include a charger as well. Perhaps opt for a cheaper one first to see that you like the system.

Cheers Mick

Ps I will just double confirm that a sd2200 will be happy to operate off 8.5v

Hi CostasDee,

The sd2200 will not run off 8.4v. A diode would need to be added to lower the voltage below 8v.

Cheers Mick

I was wondering if anyone has managed to make up a successful Li-Ion battery system for an SD2200 using only one 7.2v battery. I agree with CostasDee that some of the commercially available systems, such as the Coiltek, do it with one 7.2v volt battery and no apparent regulator although they are advertised as regulated (or internally regulated)
Is there any reason why a battery such as a Sony NP-F960, with appropriate connections or gutted out charger, couldn’t be wired up directly to an SD2200?
This is sort of repeating the original question but the posts so far didn’t really provide an answer. I’m trying to save a few bucks on making one up myself before diving in and spending $300 or more a real one!
Cheers, Warren

G'day Warren

Some of the commercial ones you can buy are made from camcorder type battries. So if you know what your doing and how to do it you could make one up like you say.

Just make sure that you test the output voltage when the battery is fully charged and it is within the detectors acceptable range to use, ie: 7.3v to 7.6v for the older SD machines as they have no internal regulator in side themselvs.

cheers dave

Buy a Lucky lark if you can get one, they can be adjusted to any voltage you need, and can be converted to suit the GPX models. here is one on fleebay http://www.ebay.com.au/itm/Reeds-Lucky-Lark-Battery-Minelab-SD-GP-/230622355446?pt=AU_Gadgets&hash=item35b229dff6

Regards Johnny

I'll probably end up going with a camcorder battery but I'm still curious about the claims they make about being "regulated" but only running a single battery.

Damn Johnny! I thought I was the only one watching that Lucky Lark, now the whole world knows.

Cheers, Warren

As mick posted above, I you want to use just the one battery, put one or two or more 3 amp diodes in series with the power output from the battery.
I have not looked at my Coiltek battery pak but I would bet that they use diodes to regulate the voltage.

Hey scraps...I ended up buying a Coiltek one off fleabay, so I put a pause on making my own. I can tell you that the batteries are 7.4v (remember that, that is the voltage of the flat battery) and reading the voltage of a fully charged battery is 8.37v. I can tell you also that although the regulator is suppose to operate at 7.3/6.7v, mine actually works at 7.72/7.05v without headphones or a speaker attached (slightly less when attached). I have not run the battery all the way down so I can't tell you what the actual battery voltage is when flat or what the regulator pushes out just before the battery gives up. I will though go out in a week & 1/2 and I'll be able to see first hand what those missing figures are. With that info, you should be able to put one together.
Don't forget though,although the detector uses approx .7A whilst running with an 11DD, the startup current is a lot higher and this might make the safety chip in the battery think that there is a short and cut the battery out (needing you to put it in the charger to reset). The Coiltek system supposedly has a current limiter to somewhat stop this from happening, but like Inhere, I haven't opened mine to look inside....
Let me know if I can be more help...

G'day CostasDee, If you don't wan't any shutdown at startup with these coiltek paks,
turn on power at the control box BEFORE switching on power at the battery pak.

Thanks Inhere, I know this and do it 99% of the time, but it's that 1% that I do it that I'm always miles from the car. I carry the spare in the backpack just incase now...I've learnt the hard way.

I've been reading this thread with interest. Some great ideas here. Can anyone tell me just how high the current draw on start up is with the SD2200 ?
panhead.

Hi Panhead, the continuous draw using a 14"D Elite is about 0.91 Amps. The startup current draw is a little harder to read with my digital readout as it fluctuates too quickly to be read correctly, but at a guess I imagine it to be about 2 Amps, but I stand to be corrected.
Cheers

panhead wrote:I've been reading this thread with interest. Some great ideas here. Can anyone tell me just how high the current draw on start up is with the SD2200 ?
panhead.

Hi Panhead,

I have never actually measured the current inrush when an sd is turned on, but I would imagine that the current would start off fairly high, like 10A or more. As the large capacitors charge up the current drops down to about .8A when the detector is running. This happens in about 200mS which is why the thermal breaker does not trip out when you turn the detector on, but the protection cct on a li-ion battery can fail if it is not rated to handle the current peak.

Cheers Mick

Hmmm. I was looking at a 5amp voltage regulator module on ebay. To build myself a 7.3v power supply. A 2 amp start up current would be OK. But if startup current is approx. 10 amps I will have to look at a different one.
panhead

Hi Panhead,

Do you have a link? It may be ok if you have your detector turned on and then turn on the power-supply.

Cheers Mick

Yep. Here it is.

http://www.ebay.com.au/itm/5-Amps-Voltage-Regulator-Module-Out-1-5-32V-Based-LM338-/400250378671?pt=LH_DefaultDomain_0&hash=item5d30c819af

G'day Panhead,

Yeah that will handle it no probs. You will however have to use a power source that is at least 1.5v higher than the voltage you are trying to achieve. 12v would be the best bet. Make sure you use a thermal breaker between the regulator and your detector. About 1 to 1.5A breaker would do the job.

Cheers Mick

Thanks Mick. I was looking at using a 12v battery. Still have to do a little investigation on that front (size, weight, etc), but good to know that the reg will work.
panhead.