Solar fried battery ?

[Rum_Pirate]

I have a "United Solar" panel, Flexible Model # 437392 on my boat.

The panel (according to the West Marine catalogue advertising blurb) has :
- internal bypass diodes
- Max Watts 5.00
- Max Amps 0.30
- Approx Ah/Day 1.9
- It is not self-regulating.

The blurb also says that voltage regulation is not necessary unless peak amperage exceeds 1.5% of the batteries Ah capasity.

A friend put a voltmeter on the output cable wires. Panel was not attached to the battery. It produces 19 volts.

As an absolute non-electrician, I need and would appreciate helpful advice on the following :
1. How do I determine the Ah capasity of the battery and thereby the 1.5% to determine if I need a voltage regulator?

2. More importantly will I "destroy" the 12 v battery, if it has say "525 cranking amps" and I use the panel without a voltage regulator?

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[snowleopard]

forget the open-circuit voltage of the solar panel - it will drop drastically as soon as you connect something across it.

forget the cold cranking amps. the amount of current it can put out doesn't relate to behaviour with small inputs

as for the AH of a battery, with luck that will be stamped somewhere on the battery. if not, as a very rough rule of thumb, a normal car-sized battery is around 60-80 AH and the capacity is roughly in proportion to the size. if your panel produces a max of 0.3A it is ok for a battery of over 20AH which equates to a small motorbike battery.

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[roger]

At 5 watts I'm not even sure its worth using. It might just slow down the rate at which the battery self discharges

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[tillergirl]

I think that's the point (slows down the rate of self discharge. I have an 11 watt one connected to Battery No 1. On a swinging mooring, at the end of the season it has (according to the battery meter which I accept is not the most accurate device) noticeably more charge than No 2 (not that No 2 is a problem).



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[pvb]

No problems...

You won't have any problems with your UniSolar panel on a battery which has a "525 cranking amps" rating. Many batteries no longer feature an amp-hour rating, but if your battery has 525 cranking amps it's probably at least 60-70Ah. So the panel's output is way lower than the 1.5% you mentioned, and no regulator is needed. You certainly won't destroy your battery!

The open-circuit voltage can be ignored; when it's connected to the battery you're unlikely ever to get more than 16v out of the panel (even in the Caribbean sunshine!).

The "internal bypass diodes" you mention are just a feature of lots of solar panels, and enable some output to be maintained even when part of the panel is in shadow.

However, at just 5 watts, the output of the panel is tiny and you shouldn't expect it to do much more than keep your starting battery topped up (batteries slowly self-discharge). It wouldn't, for example, keep up with the demands of an anchor light, although it might be up to keeping, say, an auto bilge pump going as long as your boat isn't too leaky. If you're expecting it to do much more than this, you need a bigger solar panel.

Solar panels are usually supplied with quite a long lead attached to them - this is so you can arrange the connection to your battery in a nice dry area, so that the possibility of corrosion is minimised. It's worth checking the connection periodically, because obviously any corrosion there will dramatically reduce the panel's efficiency.



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[Micky]

I get the same problem, battery seems to over charge. I have to top up the water every week. Have now fitted a switch into solar wiring loom to switch it off.

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[William_H]

The open circuit voltage of the solar panel of 17 volts is normal. Obviously if you connect the panel to the battery then to measure the panel voltage you are measuring the battery voltage. This will depend on state of charge by will hopefully creep up over time to around 13v or more. Should you have a small battery or one that has just been on charge from the engine the voltage may be over 14v. The 17v open voltage of the solar panel simply means that it could continue to put current into the battery if its voltage got near to 17v which we hopee it doesn't. (definitely boiling) If as is more likely the battery still discharges over time you will need more solar power so add another of the same type in paralell or another bigger panel as substitute or in paralell. To the poster who reckons he has a battery that uses too much water he must have a tiny battery and a huge solar panel to acheive that IMHO. will

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[Talbot]

Re: No problems...

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Many batteries no longer feature an amp-hour rating

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Your statement is correct as far as it goes. The information on the battery is really aimed at the useage of that battery. With a designator of 528 CCA, this battery is obviously designed for use as an engine starter (for a fairly large engine) and is not very happy with use in domestic applications. If the battery was a deep cycle battery it would only have the amp/hr rating, because use of this type of battery for engine starting actually damages the battery, but it is very happy in a domestic bank. Carnon fibre fe-inforced batteries are designed to be used for both deep cycle and engine start, so they have both a CCA rating and an amp/hr rating.

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[robind]

Re: No problems...

Leds are being used on Navigation bouys now so I wonder if the mast head lights are available with them or a convertion "bulb" setup at least?.
Rob

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