Float charger? Cut off at 13.5v rest until 12.5v before switch on? - Page 10 - diyAudio
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Old 25th September 2012, 07:45 PM   #91
AndrewT is online now AndrewT  Scotland
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if the maximum charge rate you require is 5A then set your CCS to 5A.
That's all you need to do for current limiting.
Then set your maximum voltage to what you require.

Finally, if there is an option to set the timer, then set that to what you require.
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Old 25th September 2012, 09:36 PM   #92
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On the Hawkins design, the current limiter is the transformer itself.
That's why they've used a 10a SCR for a 3a charger.
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Old 28th September 2012, 12:44 PM   #93
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At this time, I'm inquiring about a replacement 15a to 20a SCR for increasing the safety margin for current handling. I don't know if a more sturdy plug-in replacement exists.

Like this:
3a charger uses 10a SCR
5a charger uses 15a SCR (I hope to find it)
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Old 28th September 2012, 02:10 PM   #94
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Thanks to Azfal at Hawkins technical support, I've ordered a nice sturdy Motorola 2n6509 SCR to increase safe current headroom.
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Old 29th September 2012, 05:15 AM   #95
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Default Charging controller cct

This any help? It's from the "circuit notebook" section from the Aussie Siliconchip magazine, August 2008.
From the description:

This simple charging regulator circuit is connected between the charger and the battery and is easily adjusted to prevent the battery being overcharged beyond the optimum level between 13.8V and 14.0V.........As soon as the battery terminal voltage rises to 13.8V (or the preset voltage), TP1 rises above 7.2V and this causes the output of IC1 to switch high. The current through LED1 falls to zero and Q1 is switched off, preventing any further charging. The 47kW resistor between pins 2 & 7 of IC1 provides about 0.5V of hysteresis so that the battery voltage will need to drop by 500mV or so, before the circuit can turn back on to provide more charge.

Silicon Chip Online - Circuit Notebook
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Last edited by marcus1; 29th September 2012 at 05:17 AM.
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Old 29th September 2012, 05:23 AM   #96
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Thanks Marcus! Finally some documentation about correct battery charging voltages and cycling. I'm really grateful to see that. It can protect the Marine/RV/Industrial "not a start battery" types.

Quick, everyone look at the footnotes in red. 13.8v max. That is true, except for "car start" batteries.
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Last edited by danielwritesbac; 29th September 2012 at 05:25 AM.
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Old 29th September 2012, 12:10 PM   #97
AndrewT is online now AndrewT  Scotland
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Daniel,
that charging information comes from the battery manufacturer.
Do not expect the charger manufacturer to know what every manufacturer and every model from each of those manufacturers needs as a charging requirement.

Go to your battery manufacturer and ask them what your battery needs !!!!!!!!!!
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Old 29th September 2012, 02:16 PM   #98
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Quote:
Originally Posted by AndrewT View Post
Daniel, that charging information comes from the battery manufacturer. Do not expect the charger manufacturer to know what every manufacturer and every model from each of those manufacturers needs as a charging requirement. Go to your battery manufacturer and ask them what your battery needs !!!!!!!!!!
That's really good advice that should have worked. I tried that. Hawkins tried it too. The battery manufacturers respond with typical car battery specs or sometimes just no response.

The "slow drain" type of batteries, a "not a start battery" huge marine/rv/industrial type, all measure to resist charge and get really hot at 13.5v when new or 13.8v when older. They all run down to about 12.5 when new or 12.8v when older, if left unattended for a few days. Car alternator voltages and the higher current chargers from the auto parts store all break this type slow drain battery--it is not a car battery. The expense is terrible. But, the 1a transformer limited trickle charger doesn't break the battery and the weak solar doesn't break the battery. This would be okay except for a boat or RV that has appliances.

With a boat/RV's onboard converter-charger that does right voltage but never lets the battery idle/rest, the energy bills for slowly destroying batteries are about $40 per month and this in addition to battery replacement costs of about $130 yearly. So, the approximate average yearly waste is: $610, and $130 of that (subtract retail store margin) is unfortunately profitable for the battery manufacturers. SO, both the store and manufacturer profit from this problem at regular and expected intervals.

I said a bad word when the battery manufacturer told the battery charger people to charge the "slow drain type" batteries at breakage voltages. Although you could probably do it, if disconnecting the charger, the prospect, based on wrong data with no real-life measurements, is financially very unpleasant for nonstop maintenance charge. The typical electricity bill for abusing batteries nonstop is about $40 per month; however, if it is not charged, the circuit boards of the charge monitor, radio and fridge will eventually pull the battery down lower than 9.5v damage threshold for yet another way to break the battery. An additional method is allowing a non-full battery to freeze, which also breaks the battery.

This is an expensive problem with so many ways to break the battery!

For charger, I dreamed a low cost version--15v 90w laptop power pack, diode for reverse voltage protect, Elvee's voltage regulation circuit and 3 parallel 18w #1156 light bulbs for 54w current limiter. But that would be too easy! Yay for simple vacuum tubes/valve diode current limiter! lol!!!
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Last edited by danielwritesbac; 29th September 2012 at 02:37 PM.
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Old 29th September 2012, 07:49 PM   #99
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would not a simple fixed curret charger circuit help?
say.. something around 20-50 mA ?
that should be close to float charging, charge current would be cose to the batterys own discharge current.
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Old 30th September 2012, 08:12 AM   #100
AndrewT is online now AndrewT  Scotland
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Daniel,
ask the battery manufacturer.

Don't go trawling many different manufacturers hoping to find a consensus.
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