12v emergency start battery as power supply

  • Thread starter Thread starter KAM
  • Start date Start date
KAM said:
This sort of thing.View attachment 163593
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I use a 7 A/hr version of this type of SLA on my ex Soviet mobo.

It has a small trickle charge solar panel direct to it with no need for a controller ... panel is designed for maintaining batterys on various without controller .... I would provide a link to it - but it was bought a few years ago and eBay archive no longer has it.

But here is same from another seller ....

20W 12V Solar Panel Portable Waterproof Power Trickle Battery Charger F | eBay


It powers an 800gph automatic bilge pump, an LED spot light, a combined LED Port / Stbd nav light.
 
Refueler said:
Yes Paul ...... this sort of battery.

SLA may be a generic term - but it is this form of battery that most people think of when SLA term is used ...
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That's ridiculous. It's a boat forum, to most people here SLA means the same sort of battery that most people have on their boats. Not an alarm battery.
 
Refueler said:
I use a 7 A/hr version of this type of SLA on my ex Soviet mobo.

It has a small trickle charge solar panel direct to it with no need for a controller ... panel is designed for maintaining batterys on various without controller .... I would provide a link to it - but it was bought a few years ago and eBay archive no longer has it.

But here is same from another seller ....

20W 12V Solar Panel Portable Waterproof Power Trickle Battery Charger F | eBay


It powers an 800gph automatic bilge pump, an LED spot light, a combined LED Port / Stbd nav light.
Click to expand...
£6 for a 20w panel seems too good to be true.
 
VicS said:
The quoted dimensions, 110mm x 136 mm, mean it is far to small to be a 20 watt panel. I doubt if it is even 2 watts.
.
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Quite so. Another seller also seems to be selling this same panel. In both cases they do not quote max voltage and short circuit (max) current. Then claim "Up to" 26% solar efficiency. Ooh I hate that term "up to" . Which strictly speaking says absolutely no more than 26% with no indication of actual efficiency. Chinese sellers seem to disregard normal western meaning of things like "W" for watts. or have no interest in accuracy of product description. Probably just parrot what their supplier says. But if it is just 5 watts or less it may still have a purpose on a small boat or even a car laid up. Not a bargain but a correct price. ol'will
 
KAM said:
£6 for a 20w panel seems too good to be true.
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Its now 3yrs since I bought and fitted ....

The 7A/hr SLA is still working - pump keeping boat 'dry' ......

During that time - I have re-soldered the leads to the back of the panel 2 or 3x ... but other than that - its still working fine. I doubt it ever puts out 20W ... but then again - the battery is near always topped up - so it would be restricting panel output anyway.

6 quid may seem rubbish ... but the 'proof is in the pudding' as they say ... and the proof is it's still working fine.

You can go to Halfords and other shops and buy car maintainer panels 3x the price or more ... which would be normal mark up compared to buying direct from China ... so why would Chinese price be so ridiculed ???
 
William_H said:
Quite so. Another seller also seems to be selling this same panel. In both cases they do not quote max voltage and short circuit (max) current. Then claim "Up to" 26% solar efficiency. Ooh I hate that term "up to" . Which strictly speaking says absolutely no more than 26% with no indication of actual efficiency. Chinese sellers seem to disregard normal western meaning of things like "W" for watts. or have no interest in accuracy of product description. Probably just parrot what their supplier says. But if it is just 5 watts or less it may still have a purpose on a small boat or even a car laid up. Not a bargain but a correct price. ol'will
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The back of the panel has a resistive load - limiting the voltage to suitable for charging a nominal 12v battery .... it needs no controller .. and anyway at the low W output - a controller would not be needed.

The fact is - despite all these 'nay-sayer' posts - It works. My SLA is charged and has been happy for about 3yrs with it ... what W's it puts out ??? I don't care - it works.
 
Refueler said:
The back of the panel has a resistive load - limiting the voltage to suitable for charging a nominal 12v battery .... it needs no controller .. and anyway at the low W output - a controller would not be needed.

The fact is - despite all these 'nay-sayer' posts - It works. My SLA is charged and has been happy for about 3yrs with it ... what W's it puts out ??? I don't care - it works.
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Hello Nigel
I am very confused by your statement that the back of the panel has a resistive load to make it suitable for charging a 12v battery. A resitor will only waste power. A zener diode might limit voltage to say 14v and be useful but usually it is just panel to battery possibly via a blocking diode. The panel might produce 18v no load but the current will pull the voltage down to that of the battery. The panel has an internal resistance (ie it's natural inability to supply large current) which limits current. The limited current possible makes it OK for all but smallest batteries. Have I missed something? ol'will
 
William_H said:
Hello Nigel
I am very confused by your statement that the back of the panel has a resistive load to make it suitable for charging a 12v battery. A resitor will only waste power. A zener diode might limit voltage to say 14v and be useful but usually it is just panel to battery possibly via a blocking diode. The panel might produce 18v no load but the current will pull the voltage down to that of the battery. The panel has an internal resistance (ie it's natural inability to supply large current) which limits current. The limited current possible makes it OK for all but smallest batteries. Have I missed something? ol'will
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Can we just accept it works ?
 
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