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SISCO,
What do the TH1 and TH2 pots do in your minipulse???
What do the TH1 and TH2 pots do in your minipulse???
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Hi Sisco. I don't agree
. You must charge the batteries for 12 hours with current 1/10 of the battery capacity, or 24 hours with current 1/20 of the battery capacity, etc.....
If you charge with current 1/20 of the battery capacity then you can charge the batteries for more than 24 hours without any danger to destroy them because they are not heated.
Regards
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1843 , This is not minipuls .
In fact , this is minipuls with minediver control .
If this work good I send schematic , only must wait for 2~3 days . before
send , I must test this in all function.
Geo,my information about battery not good,but I think this is true because
write on my battery box, MODEL : 12V2.2Ah 20H
maybe mean charge 220mA for 20 hour.
can somebody help me for current battery charge ?
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Hi Sisco,Originally posted by sisco View Post
20hours means that you have to apply a slow charging strategy to avoid battery damages, not 220mA for 20hours: that way you will damage the battery.
(well depends... sometimes hours indicate the suggested maximum discharge rate:
2.2/20 = 110ma maximum... but don't belive it... I have some similar and dicharge happens also at 400mA and with no damages)
If is a common gel lead-acid battery like you can find e.g. in UPS of computers...etc you can charge in 12 hours safely.
You need a current limiter like the one in the picture and a 13.8 v power supply (1ampere or more max current).
Battery must be discharged first for at least 80%... so you have to read e.g. 11.8 or less volts.
Ok, current limit 2.2A/12 = 185mA (about)
Now say that you'll lost 3% due to internal leakage (often is 5%)
add it 185 *0.03 = 5.5 mA
Ok you need 190mA limit
Your R would be 1.25/0.19 = 6.58 ohm
You can use 4 resistors of 27ohm in parallel to get (about) the right value or others to suit better.
You need 1W for it so use e.g. 4 * 1/4W resistances.
LM317 need a small heatsink... cause initial charge is heavy and have to dissipate some heat.
So put the 13.8 volt supply on ,connect the battery and leave on charge overnight (12H).
That's all.
Best regards,
MaxComment
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Originally posted by Max View Post
Hi Max,
What's 1.25?
My battery is 12V 1.3A lead acid... What number must I use to calculate the R?
I calculated by 1.25... R should be about 11ohms...
Thanks in advance,
1843Comment
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Hi Sisco,
Why more than 10 hours?
The reason NiCad batteries are charged an extra 20% is for two reasons: First you cannot expect to achieve 100% charging efficiency so you must provide more than the exact calculated amount of charge to take care of losses. The charging efficiency will depend on the condition of the battery and how many times it has been cycled, as well as the temperature of the battery.
The second reason why NiCads are charged more than 100% is because there is an easy method to electronically detect when the cells have reached full charge. There will be a battery voltage peak that occurs approximately at 120% of the rated charge. When this peak voltage is reached, then continued charging will result in a slight drop in voltage. Some automatic battery chargers take advantage of sensing this voltage peak in order to switch the charger from charge mode to trickle mode.
Fast Charging
Nicad batteries can be charged at much higher rates than C/10. Some chargers will hot-charge NiCads in less than an hour. The danger in this practice is seen when the batteries become overheated. The heat will destroy the capacity of the battery, and can cause the built-in vents to allow gases to discharge from inside the cells. There are some smart chargers that use temperature sensors as well timing circuits and integrators to begin with a high charge rate, then decrease the charge when the battery temperature becomes too hot. These smart chargers then continue with the charging at a lower rate until the correct amount of charging has been delivered. When the charging is done, the charger switches to trickle mode which delivers only small occasional pulses, while watching the battery voltage. If you don't have a smart charger, then a safe method is to use the slow charger rate of C/10 overnight, where the charger will not cause damaging heat conditions.
NiCads or Nimh?
A question that comes to mind is why do you use NiCad batteries instead of Mimh? The Nimh batteries have all the advantages of NiCad, but with over double the power for the same size, and very little memory effect. The only advantage to using NiCads is they have lower internal resistance to deliver very high current, for use in model race cars etc. For most metal detector applications, the Nimh batteries will deliver twice the operating time, and can be used as a direct replacement for NiCads.
Sanyo is the world leader in producing quality Nimh batteries, as they are the company who developed this technology. Today you can use 2700mah AA size cells to replace the 700mah Nicads of similar size used in Minelabs excalibur detectors. These 2700mah Nimh batteries require 270 ma for overnight charging at C/10. Sanyo D-cells are rated at 5000mah if you need more power.
The real info from the manufacturer:
I believe what you need is real information. Here are links for the Sanyo data sheets for their NiCads and their Nimh batteries that they call "Twicel". These data sheets tell every detail of NiCads and Nimh including how to design a proper battery charger:
NiCad Data Sheet: http://us.sanyo.com/batteries/pdfs/cadnicaT_E.pdf
Nimh Data sheet: http://us.sanyo.com/batteries/pdfs/twicellT_E.pdf
Best wishes,
J_PComment
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Hi Sisco,
Why more than 10 hours?
The reason NiCad batteries are charged an extra 20% is for two reasons: First you cannot expect to achieve 100% charging efficiency so you must provide more than the exact calculated amount of charge to take care of losses. The charging efficiency will depend on the condition of the battery and how many times it has been cycled, as well as the temperature of the battery.
The second reason why NiCads are charged more than 100% is because there is an easy method to electronically detect when the cells have reached full charge. There will be a battery voltage peak that occurs approximately at 120% of the rated charge. When this peak voltage is reached, then continued charging will result in a slight drop in voltage. Some automatic battery chargers take advantage of sensing this voltage peak in order to switch the charger from charge mode to trickle mode. Even smarter battery chargers will sense a change in the dvolt/dtime just before this peak to shut off the charger before it hits the peak (overkill, in my opinion).
Fast Charging
Nicad batteries can be charged at much higher rates than C/10. Some chargers will hot-charge NiCads in less than an hour. The danger in this practice is seen when the batteries become overheated. The heat will destroy the capacity of the battery, and can cause the built-in vents to allow gases to discharge from inside the cells. There are some smart chargers that use temperature sensors as well timing circuits and integrators to begin with a high charge rate, then decrease the charge when the battery temperature becomes too hot. These smart chargers then continue with the charging at a lower rate until the correct amount of charging has been delivered. When the charging is done, the charger switches to trickle mode which delivers only small occasional pulses, while watching the battery voltage. The best method to determine when a NiCad has reached full charge is to measure the voltage and shut off the charger when the peak has been reached. If you don't have a smart charger, then a safe method is to use the slow charger rate of C/10 for 12-14 hours, where the charger will not cause damaging heat conditions. This 12-14 hours is a safe estimate of what an average condition NiCad battery will require to reach a full charge. If a small percent of overcharge occurs at C/10 rate, this has minimal bad effects compared to hot charging where the cells are overheated.
NiCads or Nimh?
A question that comes to mind is why do you use NiCad batteries instead of Mimh? The Nimh batteries have all the advantages of NiCad, but with over double the power for the same size, and very little memory effect. The only advantage to using NiCads is they have lower internal resistance to deliver very high current, for use in model race cars etc. For most metal detector applications, the Nimh batteries will deliver twice the operating time, and can be used as a direct replacement for NiCads.
Sanyo is the world leader in producing quality Nimh batteries, as they are the company who developed this technology. Today you can use 2700mah AA size cells to replace the 700mah Nicads of similar size used in Minelabs excalibur detectors. These 2700mah Nimh batteries require 270 ma for overnight charging at C/10. Sanyo D-cells are rated at 5000mah if you need more power.
The real info from the manufacturer:
I believe what you need is real information. Here are links for the Sanyo data sheets for their NiCads and their Nimh batteries that they call "Twicell".
These data sheets tell every detail of NiCads and Nimh including how to design a proper battery charger:
NiCad Data Sheet: http://us.sanyo.com/batteries/pdfs/cadnicaT_E.pdf
Nimh Data sheet: http://us.sanyo.com/batteries/pdfs/twicellT_E.pdf
Best wishes,
J_PComment
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So, my first calculate is true , must charge 1/10 battery current for 12H .
(Rx=1230/(1/10 battery current) for 12H)
1843 , this is mean you must use Rx = 1230 / 130 = 9.5 ohm for your battery.Comment
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Comment
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Hi Geo,
There is no magic to 12-14 hours at C/10. This is simply an average time needed for NiCads and Nimh to charge. Each battery will have a different amount of charging required that will be different from each manufacturer, and for the age of the battery, and the temperature while charging. Also, the charging efficiency is less when charging faster than C/10, and will require more correction to the formula at higher rates. The only way to know when a NiCad battery is finished charging is to watch the voltage during constant current charging. When the voltage reaches a peak and then starts to fall, then you know it is fully charged. Using the 12-14 hours at C/10 is a simple method to charge the battery without damaging it, in case you don't want to sit and watch the voltmeter or design peak sensor circuit.
Read the data sheets to find out the real methods for NiCad and Nimh. The engineers who developed these batteries are much more knowledgeable than we are. You will find near the bottom (section 8 ) some circuits for chargers to be used in different applications. They make a caution against using constant voltage design, and prefer constant current. You will also see diagrams to use for temperature controlled chargers and voltage peak sensing chargers:
NiCad Data Sheet: http://us.sanyo.com/batteries/pdfs/cadnicaT_E.pdf
Nimh Data sheet: http://us.sanyo.com/batteries/pdfs/twicellT_E.pdf
Very smart, these Japanese engineers!
Best wishes,
J_PComment
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I saw one of friends told , can replace LF357 (peramp) with MAX410 and
replace TL082 (Amp) with MAX412 and told work very better.
I try for find this parts near one month but can't find , can somebody find
this parts and test in minipuls and tell me how work ?
please somebody help me for this project
because if this work better,
good for all us .Comment
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Originally posted by 1843 View Post
Hi,
1.25 is the internal reference voltage of LM317.
The limit is set at about 1/12 of capacity to preserve battery integrity.
With gel type you could use also e.g. 0.5 ampere as max limit for 1.3AH... but then you could damage your battery.
H2 gas bubbles pressure can break easy the container... though there is always a valve there... then break the plastic (battery explode).
Best regards,
MaxComment
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Hi JP,
NiCd and NiMh are another topic. We were talking about gel-type lead-acid batteries.... the kind used in UPS.
The formation of H2 during charge is the big problem there... there is a valve that opens automatically when pressure rise over a fixed limit. The valve is hidden under the contact plastic cover. Sometimes the rapid release of bubbles and the wrong behaviour of the valve cause that batteries explode.
This happens frequently when charge current rise over 1/4 of nominal capacity, due to the huge gas bubble formation in the time unit.
Other gel-type have adsorbent medium to trap H2, like in other kind of batteries... but this normally for smaller current capacity (under 1Ah) like some digital camera batteries.
Manifacturers always reccomend slow charge rates or very small trickle charghing for in-line UPS and the like.
12h is a good timing for overnight chargers... nothing bad if you charge in 10 or 14 hours... same thing.
Problems arise when one use "fast charge" e.g. 1/4 capacity... then could damage battery, batteries could explode...etc.
Charge is almost always at fixed voltage on lead-acid batteries, but current limiter is required to avoid above problems.
Kind regards,
MaxComment
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Hi Sisco
MAX is right. ceramics and bricks are very big problem on PI detectors.but you must know what kind of bricks and ceramics detects by your detector . i guess the place that u live is full of broken shard cruse and pottry ... that made by heated soil , so you must it not on fresh brick but test on ancient bricks of rocks and castels or potterys specially that have black soil inside and red soil around , not only PI detects that objects but almost all good vlfs (IB , BFO) like Minelab explorer or White's XLT , DFX , CXIII & GTI2500 garett (I tested them ) detects that bricks.
i hope you don't have such problems !
regards
AlexComment
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