7ah / 10 watt solar charge controller? Adam2?

sam_uk · Post by **sam_uk** » 25 Aug 2011, 00:44

Hi all

Anyone know of a appropriate charge controller I could use with a 12v 7ah sealed lead acid battery, and a 10watt 12v solar panel?

Thanks

Sam

Post by **kenneal - lagger** » 25 Aug 2011, 01:53

I got one as part of a kit from Maplin so they do exist but I don't think they are selling hem now.

Post by **adam2** » 25 Aug 2011, 16:51

Any of the smaller and cheaper controllers should be fine.
http://www.windandsun.co.uk/Prices/pric ... ollers.htm Have a good selection, The cheapest is about £20.
Still cheaper ones can be found on fleabay, but I would be a bit doubtfull about such.

Be aware that a 10 watt module will take a while to charge a 7 A/H battery.
In real world conditions a 10 watt module will put about half an amp into a 12 volt battery.
Re charging from flat would take several days in summer and two weeks or more in winter.

Even a small battery can produce enough current to start a fire. Fit a fuse in one battery lead, as close as possible to the battery.

sam_uk · Post by **sam_uk** » 31 Aug 2011, 20:14

Another battery question..

Do you think it would be possible to charge one of these:

http://www.bestofferbuy.com/YSD-998-All ... n=gbase_uk

directly from a fully charged 12v 110ah battery?

Post by **adam2** » 01 Sep 2011, 08:53

Lithium ion batteries are fussy as regards charging requirements and can explode or catch fire if not charged correctly.
I would therefore strongly advise against directly connecting a lithium ion battery to any other battery.

If however you propose to use the 12 volt charging lead* that is said to be supplied, then it should be fine.
Such leads are primarily intended for in vehicle use, but the lithium ion battery does not "know" if your deep cycle 12 volt battery is fitted into a vehicle, or used as part of a PV system.
A nominal 12 volt vehicle electrical system can vary from about 11 volts to about 14 volts, and I would expect the supplied 12 volt charging lead to work correctly over that range.

Take care to carefully follow the instructions with lithium ion batteries, they are far less forgiving than most other types if not used correctly.

*I would expect that the supplied lead contains some variety of regulating or control circuit, and that it is not just a simple piece of wire.

sam_uk · Post by **sam_uk** » 02 Sep 2011, 10:43

Thanks Adam

I willl give it a go

An Inspector Calls · Post by **An Inspector Calls** » 03 Sep 2011, 09:05

adam2 wrote:Lithium ion batteries are fussy as regards charging requirements and can explode or catch fire if not charged correctly.
I would therefore strongly advise against directly connecting a lithium ion battery to any other battery.

Have you warned your acolytes that charging lead/acid batteries also carries a risk of explosion?

Post by **adam2** » 03 Sep 2011, 13:15

An Inspector Calls wrote:
adam2 wrote:Lithium ion batteries are fussy as regards charging requirements and can explode or catch fire if not charged correctly.
I would therefore strongly advise against directly connecting a lithium ion battery to any other battery.
Have you warned your acolytes that charging lead/acid batteries also carries a risk of explosion?

Not specificly.
The risks are minimal with small lead acid batteries.
The battery itself can not explode under any reasonably forseeable conditions of misuse. The contents are neither flammable nor under pressure.
Overcharging will lead to the production of hydrogen and oxygen. The mixture of these gases is undeniably explosive and serious accidents have occured with large battery banks.
However under normal charging conditions with a charge regulator a vented battery will produce only minute traces of gas, and a sealed battery will produce none whatsoever.
In the event of serious and prolonged overcharge then more gas would be produced, but with a battery as small as 7A/H I doubt that a dangerous amount could be produced, except in the most improbable circumstances.
A prolonged moderate overcharge such as from a 10 watt PV module, will eventually destroy the battery, but it would take weeks, maybe months, and the rate of hydrogen production would be extremely small and most unlikely to build up to a dangerous level.
These batteries are very widely used in toys and portable lighting equipment, often with rather crude charging arrangements.
Explosions are virtually unknown.

Lithium batteries though reasonably safe in correct use, are arguably less safe than lead acid.
They are tightly sealed and can burst violently as a result of overcharge or manufacturing fault.
The contents are highly flammable and liable to ignite on contact with air.

Potemkin Villager · Post by **Potemkin Villager** » 03 Sep 2011, 20:32

adam2 wrote:

Lithium batteries though reasonably safe in correct use, are arguably less safe than lead acid.
They are tightly sealed and can burst violently as a result of overcharge or manufacturing fault.
The contents are highly flammable and liable to ignite on contact with air.

They sound really dandy for a pyromaniac!