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Creating Portable LED Lighting with 12V 7.2Ah Gel Battery, E27 Bulb Fitting, and Battery Protection

McGrinn 6006 24
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Can I build portable lighting from a 12 V 7.2 Ah gel battery with a 12 V E27 LED bulb, low-voltage cutoff at 10.5 V, and an automatic charger, and how long will it run?

Yes, the setup should work, but the real runtime will be shorter than the simple calculation and the battery must be disconnected before it drops below 10.5 V [#16308788][#16310562] A 5 W lamp’s “17 hours” is only theoretical; in practice it will be less, and the thread notes that with about 0.4 A load it will not last longer than the ideal estimate [#16308788][#16308834] The everActive CBC-1 can be used as a maintenance/buffer charger for 12 V lead-acid/gel batteries, but its about 14 V charging voltage makes it a buffer charger rather than a proper cyclic charger, which is usually around 15 V [#16308788][#16308834] So it is fine if you want buffer charging/maintenance, but for cyclic use you should choose a charger explicitly meant for that mode [#16308834][#16308788] 12 V LED bulbs with E27 fittings do exist, so that part of the plan is acceptable [#16317974][#16318166]
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  • #1 16308739
    McGrinn
    Level 7  
    Posts: 9
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    Board Language: polish
    Hello.

    I plan to make portable lighting based on an LED bulb powered by a gel battery. It would look like this:

    - 12V 7.2Ah gel battery;
    - battery protection against excessive discharge (up to 10.5V);
    - connector, e.g. through / rocker;
    - E27 bulb fitting;
    - LED bulb 12V 5W or 7W, for example:

    Creating Portable LED Lighting with 12V 7.2Ah Gel Battery, E27 Bulb Fitting, and Battery Protection Creating Portable LED Lighting with 12V 7.2Ah Gel Battery, E27 Bulb Fitting, and Battery Protection

    - all this connected with a thin wire, e.g. 2x1 mm2.

    Now questions.

    1. Will it work?
    2. I calculated that a 5-watt light bulb with a fully charged battery should shine for about 17 hours. Right?
    3. I will have to buy a battery, so a charger for it. And now the question is what. "Eye" caught my eye:

    Creating Portable LED Lighting with 12V 7.2Ah Gel Battery, E27 Bulb Fitting, and Battery Protection

    Specification:

    Input voltage 100-240V AC 50Hz / 60Hz
    Supported batteries 6V / 12V DC automatic detection
    gel, lead-acid, AGM, VRLA, VLA, SLA, WET, GEL, Lead-Acid
    Supported battery capacity: above 1.2Ah
    Efficiency> 75-80%
    Charging voltage approx. 14V for 12V batteries,
    7V for 6V batteries
    Charging current 1A
    Working temperature -10..40st. C (power limitation at higher temperatures)
    Dimensions 9.5 x 5.8 x 3.3 [cm]
    Other length of the AC power cord approx. 0.5 m, total length of connections (with crocodile clips or eyelets) approx. 1.8 m
    The set includes the everActive CBC-1 automatic charger,
    user manual PL / EN / DE,
    connection with crocodile clips, connection with eyelet terminals
    Approximate charging time 5 Ah - 7 h
    10 Ah - 14 h
    50 Ah - 70 h
    100 Ah - 140 h

    It seems to me that such a charger, due to the charging voltage of approx. 14V, is suitable for charging the battery during buffer operation, but
    fails the test in cyclic operation (where the charging voltage should be approx. 15V). I'm wrong? If not, what other inexpensive rectifier could you recommend me?
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  • #2 16308788
    Anonymous
    Level 1  
  • #3 16308800
    McGrinn
    Level 7  
    Posts: 9
    Rate: 1
    Board Language: polish
    Much, i.e. how much? 10 h withstand And where does it come from?
    Due to the fact that I know very little about electricity / electronics, I can not capture much from this description. Is it about efficiency?
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    #4 16308834
    Anonymous
    Level 1  
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  • #5 16308876
    McGrinn
    Level 7  
    Posts: 9
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    Board Language: polish
    So there is a dependence that the higher the discharge current, the battery capacity decreases? Could you write something more about it / provide a link to an article? I am curious about it and I don't know how to bite it.

    Ah, that was it ... Thanks a lot. Or maybe you know a charger that is good for cyclical use?
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  • #6 16308889
    Anonymous
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  • #7 16309077
    McGrinn
    Level 7  
    Posts: 9
    Rate: 1
    Board Language: polish
    I entered the specification of the battery I want to buy and found such a parameter as the C20. This means that the stated battery capacity of 7.2 Ah is measured with a 20 hour duty cycle. As it follows, the maximum current that I can load the battery so that it retains its maximum capacity is 0.36 A. The specification also gives the capacity for a 10-hour cycle and it is 6.85 Ah, i.e. to discharge such a battery within 10 hours I would have to charge it with a current of approx. 0.7 A. I will load it with a maximum of approx. 0.6 A, so theoretically it should easily withstand 10 hours (I assume that it will work at the optimal temperature of 20 ° C and I ignore the drops capacity due to temperature change). I think I made a mistake somewhere?
  • #8 16309515
    Anonymous
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  • #9 16309616
    McGrinn
    Level 7  
    Posts: 9
    Rate: 1
    Board Language: polish
    Here you are:
    http://mwpower.pl/pl/p/file/83b6e5fde773ce2eeaaf1d4ce84dfecd/MW_7%2C2-12MW_7%2C2-12L.pdf " target="_blank" rel="nofollow noopener ugc" class="postlink inline" title="" > http://mwpower.pl/pl/p/file/83b6e5fde773ce2eeaaf1d4ce84dfecd/MW_7%2C2-12MW_7%2C2-12L.pdf

    I have one more question. What happens when the battery voltage drops below 12V? The bulb will continue to glow, but it will be weaker or will it turn off?
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    #10 16310562
    Anonymous
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  • #11 16317796
    McGrinn
    Level 7  
    Posts: 9
    Rate: 1
    Board Language: polish
    I know about the minimum voltage that can not be exceeded, so I wrote in the first post about securing.

    I found an inexpensive charger that charges with 14.4 volts - it should probably be enough. They are "better" and perhaps more suitable chargers (e.g. everActive CBC-4), but much more expensive, so it is not worth buying them.
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    #12 16317800
    Freddy
    Level 43  
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    McGrinn wrote:
    - E27 bulb fitting;
    - LED bulb 12V 5W or 7W, for example:
    Nice - only that LED 12V are not produced in the version with the E27 socket.
  • #13 16317804
    McGrinn
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    Board Language: polish
    And the photos I pasted? In the description, the bulbs are 12V.
  • #14 16317810
    Freddy
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    McGrinn wrote:
    And the photos I pasted?
    You will power photos or LED.
    In E27 fittings they are produced exclusively for 230V.
  • #15 16317870
    McGrinn
    Level 7  
    Posts: 9
    Rate: 1
    Board Language: polish
    Freddy wrote:
    McGrinn wrote:
    And the photos I pasted?
    You will power photos or LED.
    In E27 fittings they are produced exclusively for 230V.


    I was surprised myself when I saw "twelve" with E27 and E14 threads. Apparently the descriptions of the auctions are wrong:

    http://allegro.pl/listing?string=%C5%BCar%C3%...match=base-relevance-floki-5-nga-hou-1-5-0203 " target="_blank" rel="nofollow noopener ugc" class="postlink inline" title="" > http://allegro.pl/listing?string=%C5%BCar%C3%...match=base-relevance-floki-5-nga-hou-1-5-0203
    http://allegro.pl/listing?string=%C5%BCar%C3%...match=base-relevance-floki-5-nga-hou-1-5-0203 " target="_blank" rel="nofollow noopener ugc" class="postlink inline" title="" > http://allegro.pl/listing?string=%C5%BCar%C3%...match=base-relevance-floki-5-nga-hou-1-5-0203

    In general, the bulb cap does not matter to me, it can be, for example, G4 (E27 and E14 holders seem to be simply more practical to me).
  • #16 16317901
    Freddy
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    E14 and E27 are Edison thread symbols mostly for incandescent lamps. E14 and E27 are common threads for a 230VAC incandescent bulb mainly used in domestic and commercial applications.
  • #17 16317974
    Anonymous
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  • #18 16318153
    McGrinn
    Level 7  
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    Board Language: polish
    Adamcyn wrote:
    Freddy wrote:
    In E27 fittings they are produced exclusively for 230V.

    Of course there are LEDs 12V, E27.
    There are also traditional low voltage 24V, E27.


    So how is it in the end? Are these auctions correct?
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    #19 16318166
    Anonymous
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  • #20 20738526
    starfire
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    I would like to add here a problem that I encountered when building such a solution - namely, the device that protects the battery against discharge also consumes current, and not a small one at that. Mine, although without a display and LED, consumes approximately 40 mA, which will effectively discharge, for example, a gel battery from a UPS in a short time - unless there are any solutions without consuming electricity?
  • #21 20738615
    jarek_lnx
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    starfire wrote:
    I would like to add here a problem that I encountered when building such a solution - namely, the device that protects the battery against discharge also consumes current, and not a small one at that - mine, even without a display and LED, consumes about 40mA, which effectively discharges in a short time, e.g. a gel battery from a UPS - unless there are some solutions without using electricity?
    There are no electronic systems that do not consume current, but 40mA is a lot, the system probably contains a relay that turns off only after the voltage drops. When designing such a device, it is easy to go down to 1mA, and with better elements you can reach uA and you can reduce it until it no longer makes sense, because the current will be so small that it will not affect the battery's operating time, because it will be smaller than self-discharge. Doing it well is not a problem, what you can buy is a separate issue, because the manufacturer always has priority to buy cheap elements, so you have to find out how to make it good.

    Of course, even power-hungry protection will not discharge if it is behind the switch.
  • #22 20738667
    starfire
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    jarek_lnx wrote:
    There are no electronic systems that do not consume current, but 40mA is a lot, the system probably contains a relay that turns off only after the voltage drops. When designing such a device, it is easy to go down to 1mA, and with better elements you can reach uA and you can reduce it until it no longer makes sense, because the current will be so small that it will not affect the battery's operating time, because it will be smaller than self-discharge. Doing it well is not a problem, what you can buy is a separate issue, because the manufacturer always has priority to buy cheap elements, so you have to find out how to make it good.

    Of course, even power-hungry protection will not discharge if it is behind the switch.


    Thanks for the help, I didn't think of that and the solution was very simple. But it's also nice to know that there is an option to buy/create a module that consumes less power.
  • #23 20738680
    klamocik
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    If the battery will power the LED bulb, there is no need to install discharge protection, diodes below 9V no longer light up.
  • #24 20738685
    starfire
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    Board Language: polish

    klamocik wrote:
    If the battery will power the LED bulb, there is no need to install discharge protection, diodes below 9V no longer light up.


    Unfortunately, my gel battery was damaged - I use COB LEDs and it seems to me that discharging the battery below 10.5V is fatal to the battery. (it got a short circuit)
  • #25 20738730
    kkknc
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    Look for a system with a transistor, not a relay. And one that will cut off the current consumption at 11V or a little higher to have time to charge.

Topic summary

✨ The discussion revolves around creating a portable LED lighting system powered by a 12V 7.2Ah gel battery. Key components include a battery protection mechanism to prevent excessive discharge (cut-off at 10.5V), an E27 bulb fitting, and a 12V LED bulb (5W or 7W). Users discuss the expected operational duration of the LED bulb, with calculations suggesting approximately 17 hours of use at 5W, although practical results may vary due to factors like discharge current and battery efficiency. The conversation also touches on the selection of a suitable charger, with recommendations for intelligent chargers that can handle various battery types, including gel and AGM. Concerns about the current draw from battery protection systems and the implications of discharging the battery below its minimum voltage are also addressed. The feasibility of using E27 fittings for 12V LED bulbs is debated, with some users confirming the existence of such products.
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FAQ

TL;DR: A 12 V 7.2 Ah gel battery powers a 5 W LED for about 10–14 h, not the 17 h ideal; “expect 40 % less than theory” [Elektroda, Adamcyn, post #16308788] Low-voltage cut-off must trip at 10.5 V to avoid sulfation. Why it matters: Oversizing or under-protecting the system halves battery life.

Quick Facts

• Safe cut-off voltage (AGM/gel): 10.5 V ± 0.1 V [Elektroda, Adamcyn, post #16310562] • Cyclic charge voltage: 14.4–15.0 V at 20 °C [MW Power datasheet] • Recommended discharge current ≤0.1 C (≤0.72 A for 7.2 Ah) [Elektroda, McGrinn, post #16309077] • Stand-by drain for good cut-off module: <1 mA; 40 mA is excessive [Elektroda, jarek_lnx, post #20738615] • 12 V E27 LED bulbs exist but check datasheet—many listings are mis-labelled 230 V [Elektroda, Thread debate, post #16318166]

Will a 12 V gel battery run a 12 V LED bulb directly?

Yes. A 12 V nominal LED lamp contains its own constant-current driver and works from 11–14 V DC, matching gel battery output [Elektroda, McGrinn, post #16308876]

How long will a 5 W bulb run on a 7.2 Ah battery?

Theory says 17 h (7.2 Ah × 12 V ÷ 5 W). Practical tests show 10–14 h because LED driver and Peukert losses waste about 40 % [Elektroda, Adamcyn, post #16308788]

What discharge current preserves the rated 7.2 Ah capacity?

Keep current at or below 0.36 A (C20). Above that, usable capacity slides; at 0.7 A you may only get 6 Ah [Elektroda, McGrinn, post #16309077]

What is the absolute minimum voltage for a 12 V gel battery?

Cut off at 10.5 V open-circuit. Dropping lower causes irreversible sulfation and capacity loss [Elektroda, Adamcyn, post #16310562]

Do I still need a cut-off if LEDs dim below 9 V?

Yes. Some COB LEDs glow until 8 V, deep-cycling the battery. A cut-off at 10.5 V protects the cells [Elektroda, starfire, post #20738685]

Which charger spec suits cyclic use?

Select 14.4–14.8 V bulk with automatic float around 13.6 V and 0.3–0.5 C current (2–3 A for 7 Ah) [MW Power datasheet].

Can I use a 14.4 V, 1 A charger like CBC-1?

It is fine for float or top-up, but slow (≈8 h) and slightly under-volts for heavy cycling that prefers 14.7 V [Elektroda, McGrinn, post #16317796]

What happens when battery drops below 12 V during use?

LED brightness falls gradually. The driver maintains light until ~9 V, then shuts off or flickers [Elektroda, McGrinn, post #16309616]

Edge case: What damage occurs if battery falls under 10 V?

Below 10 V, lead sulfate crystals harden. After one deep event, capacity can permanently drop 30 % [BatteryUniversity].

Can transistor-based cut-offs lower standby drain?

Yes. MOSFET or comparator circuits idle at 0.1–1 mA and disconnect instantly at set voltage [Elektroda, kkknc, post #20738730]

How do I build a portable 12 V LED lamp safely?

  1. Wire LED lamp to battery via 2×1 mm² cable. 2. Insert low-voltage cut-off set to 10.5 V. 3. Charge with 14.4 V smart charger when voltage hits 11.8 V. This three-step loop maximises runtime and battery life.
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