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karmacoma
Newbie
Joined: 25/08/2015
Location: AustraliaPosts: 17 |
| Posted: 11:50am 26 Aug 2015 |
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Can I charge one 12V battery from another 12V battery without a regulator?
I want to charge a 12V 7.2Ah SLA battery from the solar power storage battery on my tiny remote PV system. The main battery is just a 140Ah car battery.
Can I do this without a regulator?
Ian |
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govertical
Guru
Joined: 11/12/2008
Location: United StatesPosts: 383 |
| Posted: 12:03pm 26 Aug 2015 |
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Greetings, from my experience with SLA batteries it may expand and burst if charged over the 12 volt limit. Hopefully other members will offer better info. Good question, thanks for posting. Edited by govertical 2015-08-27
just because your a GURU or forum administer does not mean your always correct :) |
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karmacoma
Newbie
Joined: 25/08/2015
Location: AustraliaPosts: 17 |
| Posted: 01:00pm 26 Aug 2015 |
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Govertical, that would be a concern! But if the maximum voltage in the main battery is 14.4V or so (when it is itself charging through a PV panel and a high quality PV regulator), would that be too much for the SLA to cope with? |
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govertical
Guru
Joined: 11/12/2008
Location: United StatesPosts: 383 |
| Posted: 01:19pm 26 Aug 2015 |
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Hi, the manufacturer of your SLA may provide max charging information. Different battery types have different charging limitations.
just because your a GURU or forum administer does not mean your always correct :) |
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rustyrod
Senior Member
Joined: 08/11/2014
Location: AustraliaPosts: 121 |
| Posted: 05:29pm 26 Aug 2015 |
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In my experience, the rule of thumb with most batteries the amp hour divided by 10 is the charge rate
7.2 ah is .72 amp
then a 12v x 6 watt bulb draws .5 amp
or 12v x 10 watt bulb draws around .8 amp
install a bulb of choice in your charge circuit.
It will glow brightly for a start if your charging battery is flat and decrease as it charges
when the two voltages are the same it will go out.
you may charge a 6 volt battery in this manner although you will have to monitor when it is charged
using very small bulb you may charge a 1.25v elcheepo rechargeable cell in a few hours
been doing this like for ever
Always Thinking |
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karmacoma
Newbie
Joined: 25/08/2015
Location: AustraliaPosts: 17 |
| Posted: 11:29am 27 Aug 2015 |
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rustyrod, is the idea of the lightbulb to limit the charging current so that the car battery doesn't push energy into the discharged SLA battery at a very high current? |
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rustyrod
Senior Member
Joined: 08/11/2014
Location: AustraliaPosts: 121 |
| Posted: 03:47pm 27 Aug 2015 |
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Yes, this is correct
Different wattage bulbs will give different charging currents.
Always Thinking |
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karmacoma
Newbie
Joined: 25/08/2015
Location: AustraliaPosts: 17 |
| Posted: 12:27am 28 Aug 2015 |
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I like how low-tech this is. Since we will be doing this in a Pacific Islands village, this kind of 'bush mechanic' approach is good. It's pretty elegant actually, because the light acts as a charging indicator - i.e. it goes out when charging is complete. The only thing is that traditional incandescent bulbs are getting harder to find - but hopefully there are still some bulbs in those wattages in the auto-parts shops.
Ian |
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Georgen
Guru
Joined: 13/09/2011
Location: AustraliaPosts: 462 |
| Posted: 11:25pm 31 Aug 2015 |
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Couldn't use LED globes instead of incandescent one?
Edited by Georgen 2015-09-02
George |
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solarwind
Regular Member
Joined: 03/02/2008
Location: South AfricaPosts: 51 |
| Posted: 11:27am 17 Sep 2015 |
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No, unfortunately not. Leds can only pass about 30mA or so max. (depending on the type of LED).
Incandescent lamps make fine current limiters!
You don't have success until you've tried it! |
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