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Forum Index : Electronics : car battery power
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| irishron40 Senior Member  Joined: 22/09/2014 Location: IrelandPosts: 251 |
just wondering as i read all different opinions on google. I am running all my led garden lights on a car battery. load is drawing 1.87 amp My battery is 3 months old and is a bosh S4 029 95a/h It gets fully topped of my solar panel every day;(160W 12V Photovoltaic Solar Panel 160Watt 12Volt Monocrystalline Solar Module) I know a full battery is about 12.6 volts. but is it normal after about 2 hours that my voltage has dropped to about 11.9 volts while lights remain on? and after 3 hours its down to 12.8volt when i switch lights off its goes back up to about 12-12.1 volts? considering i only draw 4 a/h? my understanding is that I should be able to run 4 amps for about 27 hours on a 110 a/h battery also wonder if that panel is to big to charge this battery thanks. ron |
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| davef Guru  Joined: 14/05/2006 Location: New ZealandPosts: 499 |
Hopefully you have a solar controller between the panel and your battery. Discharging a 110A/H battery at the c/20 rate (ie about 5A) you should get the full 100A/H out (of a new battery). Do you mean 11.8Volts? You need to wait a considerable length of time. I have read like 6 hours resting (no charging or discharging) for the battery to settle to a useful voltage reading. Also, is your load a constant 1.87Amps or is the waveform more of a pulse of much higher current? |
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| irishron40 Senior Member Joined: 22/09/2014 Location: IrelandPosts: 251 |
Yes I build one that I found on this site. The low is set to 12.9 and the high is 14.9 charge controller yes 11.8 I dont understand what you mean. when i have lights on And i connect amp meter it shows me I draw 1.87 amp ron |
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| irishron40 Senior Member Joined: 22/09/2014 Location: IrelandPosts: 251 |
ALSO SEE THAT SOLAR PANEL SUPPLIES 20 VOLTS AND OVER. IS THIS NOT TOMUCH FOR CHARGING A 12 V BATTERY? i ALWAYS THOUGHT CHARGING VOLTAGE SHOULD BE UP TO 15 VOLT? THANKS RON |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
DONT SHOUT! Yes most solar panels for 12v will make over 20v in full sunlight. This is perfectly normal. Your charge controller takes care of the battery to prevent over charging. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| irishron40 Senior Member Joined: 22/09/2014 Location: IrelandPosts: 251 |
Sorry for caps glenn. but my main question was. is it normal that my 95a/h battery shows 11.9 when lights are on for 3 hours and only draw 1.87 amps when i then switch of the lights it goes back to 12.1. but i am suppriced that 1.87 amp for 3 hours make the batter drop that much i know solar panels can make over 20 volt, but how does controller deal with that. my understaning is that it keeps feeding battery 20 volt untill batter is full. isnt that too much voltage for charging? should that sound right to you? thx ron |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
1.87 amps for 3 hours drop to 11.9, I would think thats OK, but would need to do the maths, someone else may know better. Next time your solar panel is charging your battery, measure its voltage. You'll find the battery, while its charging, is pulling the solar panel voltage down closer to 13 volts. The battery acts like a load while its charging. Once charged, its voltage will go up, and this is where the charge controller cuts in and disconnects the solar panel. The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| irishron40 Senior Member Joined: 22/09/2014 Location: IrelandPosts: 251 |
that does make sence. I must check it tomorrow and see what happens. thx glenn. |
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| davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499 |
Your meter reads 1.87A, but what is the actual waveform like going into your LED drive circuitry? They could be drawing pulses of current, ie 5A and your meter is trying to read some average or RMS or ?? value. If it is reading average then your indicated 1.87A could be close. What type of battery? Although it is going to waste one of your cycle life of the battery you could calculate the value and wattage of a resistor to draw C/20, fully charge the battery and do a discharge test down to the (resting) voltage quoted by the manufacturer. |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
] Hi Ron Your 110 AH battery is only capable of giving about 40 AH with reasonable life expectancy that is a discharge to 33.3 %capacity if you continually discharge a lead Acid battery it will shorten it's life dramatically. 
This is the makers spec for a high Quality Deep cycle battery it shows the loss of life cycles with different cycle depths. All the best Bob Foolin Around |
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| irishron40 Senior Member Joined: 22/09/2014 Location: IrelandPosts: 251 |
hi and thanks for the replies. to davef i check amperage later without solar and charge controller its a Bosch S4029 (95a/h ) to VK4AYQ the links didnt work. cheers ron |
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| davef Guru Joined: 14/05/2006 Location: New ZealandPosts: 499 |
Sorry, by type I meant flooded or SLA. I see it is a SLA. Beware that these batteries do not like being over-charged. Your solar controller should take care of this. Don't connect the battery directly to the PV panel. To see the actual waveform you would need a current shunt and an oscilloscope. |
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| irishron40 Senior Member Joined: 22/09/2014 Location: IrelandPosts: 251 |
its connected thru the charge controller. cheers ron |
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| VK4AYQ Guru Joined: 02/12/2009 Location: AustraliaPosts: 2539 |
Sorry Ron Can't get the file to upload, Have a read of the battery book. Bob http://www.gutenberg.org/ebooks/29718?msg=welcome_stranger Foolin Around |
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