Electrical safety when using 12 volts.

[Andy Hunt]

Don't mean to hijack the thread but didn't want to start a new one. Anyone know where I can obtain some semi-flexible pv panels to go on a boat roof? I'm looking for something with a reasonable power output (80W and up). The Uni-solar 124W or 136W panels are the right sort of thing but suppliers are few and far between and as usual the UK price is over double the US price. There also appear to be some BP Solar panels that might do the job but I can't find a supplier for those anywhere. Anyone seen anything?

Anything here any good for you?

http://www.energyenv.co.uk/SolarModulesFlexible.asp

[RevdTess]

Anything here any good for you?

http://www.energyenv.co.uk/SolarModulesFlexible.asp

Insanely overpriced, alas, even for UK distributors. But thanks for trying.

[RenewableCandy]

I take it you've tried Ebay? I once saw quite a lot of (non-flexible) PV going there.

[PaulS]

Hi Adam and thanks for your advice.

I am about to install off-grid electrical supply based on 3x1kW wind generators plus about 800W solar panels. Storage will be in 24 heavy duty deep cycle batteries, connected four in parallel to produce 48V, and then an 5kW inverter to power the whole house. Also an automated switch between battery power and mains for when the batteries run down too much.

I plan to house the batteries in my 'office'. MY question is:
Are they going to produce noise/ humming?
Will they produce heat?
Any other dangers/ fumes etc?

Thanks

[adam2]

Hi Adam and thanks for your advice.

I am about to install off-grid electrical supply based on 3x1kW wind generators plus about 800W solar panels. Storage will be in 24 heavy duty deep cycle batteries, connected four in parallel to produce 48V, and then an 5kW inverter to power the whole house. Also an automated switch between battery power and mains for when the batteries run down too much.

I plan to house the batteries in my 'office'. MY question is:
Are they going to produce noise/ humming?
Will they produce heat?
Any other dangers/ fumes etc?

Thanks

I presume that "four in parrallel to produce 48 volts" is a typo and that you meant in four in series.
Presuming that the batteries are 12 volts each, then four in series is correct.

Batteries are virtualy silent in use and produce only very slight bubbling sounds and therefore should be no problem in an office.

Tradditional flooded batteries do produce fumes when being charged, these fumes are both unpleasant smelling and an explosion risk. For this reason some authorites advise against installing any such batteries in a living area.
IMHO the risks are exagerated provided that the batteries are not overcharged, and that smoking and other naked lights are prohibited in the immediate area.
For a very large battery a dedicated room or an outbuilding should be considered.
For a more moderate size battery, it is in my view in order to place it in living/working accomadation.
After all many disabled persons use electric wheelchairs, these are generally used and charged indoors, and many domestic garages are used as workshops without the vehicle battery being considered a risk.

An idea worth considering is to place the battery in a purpose built wooden enclosure, this being airtight to the room in which it is placed, but ventilated to the outside air, either by natural airflow or a fan.
If the wooden enclosure is suitably sized it could be used as a bench seat, or for some other purpose.

Batteries do produce heat, though not that much, it is unlikely to be noticable in most cases.
The inverter will produce a certain amount of noise, not loud, but sometimes of a very irritating frequency, dont place it too close to a desk, armchair or bed, though in the same room should be fine.
The inverter will also produce heat, typically about 10% of the load being supplied, in most cases this is no problem, though in hot conditions it might be.

BTW dont forget to allow for the risk of the inverter failing (during a grid failure, on Christmas eve)
If finances do not permit keeping a spare, then I suggest a few essiential lights be supplied direct from the battery, 50 volt lamps can be obtained for this purpose.

[MisterE]

After reading this thread, I know realise how little I know about low voltage stuff. House wiring is simple by comparison. Great thread

[MacG]

An idea worth considering is to place the battery in a purpose built wooden enclosure, this being airtight to the room in which it is placed, but ventilated to the outside air, either by natural airflow or a fan.
If the wooden enclosure is suitably sized it could be used as a bench seat, or for some other purpose.

Uhh... be careful with this "ventilation" thing if you place ordinary lead/acid batteries in a closed box. They produce hydrogen when charged and if you put the batteries in a box you DO want to have good ventilation!

Having lead/acid batteries indoors is like having a pig indoors. Messy. After a couple of years you will notice that they have produced some kind of aerosol of sulfuric acid which have messed up everything within a meter from the battery/pig.

Keep the darn things in an outhouse, but keep them lukewarm if you can in order to preserve capacity. At -10 deg C they only carry 30-50% of rated capacity.

[MisterE]

A heavily insulated out house, with rad painted black on the roof to circulate hot water inside via pipes to keep the temp up over winter ie the old solar dhw jobby on the cheap / free. I think that is how I'd want to do it, I dont liek the idea of keeping them in the house - yuck

[adam2]

Having lead/acid batteries indoors is like having a pig indoors. Messy. After a couple of years you will notice that they have produced some kind of aerosol of sulfuric acid which have messed up everything within a meter from the battery/pig.

Keep the darn things in an outhouse, but keep them lukewarm if you can in order to preserve capacity. At -10 deg C they only carry 30-50% of rated capacity.

For a large battery bank, I would agree that an outbuilding is preferable, however many on theses forums are considering the use of one or two leisure batteries to supply limited lighting and/or central heating pumps in the event of grid failure.
Building an outhouse is a bit OTT for such small simple installations.

For a large or complex battery system, whether using wind/solar, or grid power I would allways advise consulting an approved electrician or a RE specialist.
My suggestions here refer to the type of small simple systems that many are considering installing themselves without outside assistance. In such small simple systems I would consider it acceptable to locate a few batteries indoors, preferably in a plastic crate or wooden box.

The acid mist emmitted by batteries can certainly be damaging to the surroundings, it may be reduced by proper charge control, to avoid overcharging

[mikepepler]

Time to re-awaken this old thread...

I've been thinking about our batteries and their ventilation. We have them in a small enclosure under the stairs, with a vent to outside:
http://peplers.blogspot.com/2011/04/par ... solar.html

However, there's just one vent, and I'm now thinking I should actually have another one higher up as well, to provide air circulation. Any thoughts?

Also, I currently have plug connectors outside the battery enclosure for the solar panels to the controller, and the controller to the battery. Appropriate fuses are in use, but I was thinking perhaps I should also be using isolator switches for the solar, charge controller and the battery output?

One other question though - I'm thinking of upgrading my pair of 6yr-old second hand batteries for one of these:
http://www.barden-ukshop.com/rolls-12cs ... 1715-p.asp
and getting these hydrocaps to use with it:
http://www.barden-ukshop.com/rolls-hydr ... 2280-p.asp

Now this is a lot of money to spend on a battery, so:
- any thoughts on whether there's a cheaper alternative with the same quality (10yr warranty, 3,200 cycles to 50%)?
- would the use of hydrocaps remove the need to worry about adding more ventilation? (this is what is implied at the above link)

[emordnilap]

And finally I have got the bits together for draining barrels of water, sunk in the ground, which fill from guttering on the polytunnel.

A 'leisure' battery (75Ah), a 13 watt solar panel which was half price in Maplins and came with cabling and a small regulator, a 12-volt timer (http://www.12volttimer.com/ which is just used as a switch until I set up some drip irrigation system) and a Rule 12-volt bilge pump. It's all wired up and works, just have to rig up a barrel in the pt and some piping.

Any issues to keep an eye on, guys? A specific question, do these 'leisure' batteries need some kind of conditioning occasionally, or just a good shaking up?

[adam2]

Since lead acid batteries can produce hydrogen, idealy a high level vent to the outside air should be provided to remove this, and a low level vent to supply fresh air.
In practice though, this may be a bit OTT for only 2 batteries.
An understairs cupboard or similar is most unlikely to be sufficiently airtight for hydrogen to collect to a dangerous degree.
If the hydrogen escapes into the home, it should be so diluted as to be harmeles.
It would be well of course to prohibit smoking or other sources of flame or spark near the batteries.
Switches and plugs/sockets are best placed outside the battery enclosure as they are liable to produce sparks.

As regards placement of fuses, opinions differ.
To limit the length of unfused cable, it is desireable to place the fuse as close to the battery as possible, but that means within the battery enclosure which is undesireable if a spark could result from blowing of the fuse.
My usual practice is as follows.
For a small installation, less than about 15/20 amps maximum current, I use a cheap vehicle type in line fuse holder placed outside the battery enclosure. Any spark resulting should be harmless as it is outside the battery enclosure.
Remember that in a small installation, that this fuse may be the ONLY fuse, and in practice will be replaced live with risk of sparking. To reduce the risks from the unfused wires between the battery and the fuse, the positive and negative wires should take well seperatted routes and be double insulated, such that a short circuit is impossible even in the event of gross damage.

For a large installation, with a potential load or charging current of 40 amps upwards, then I put a MAIN fuse within the battery enclosure as close as possible to the positive terminal. This fuse and holder should be of good qaulity and designed for mains voltage. The style used by the electricty companies for house service cutouts are very suitable. If this fuse blows, it wont produce a spark unlike cheap vehicle fuses.
The main fuse should feed a suitable fusebox outside the battery enclosure.
In the hopefully rare event of the main fuse blowing, then all subcircuit fuses should be removed before replacing the main fuse, to avoid a spark from the fuseholder contacts.

[mikepepler]

Thanks Adam, I've used vehicle fuses inside the enclosure, but inside their own small enclosures.

What do you think about the hydrocaps though? Good idea?

However, I've discovered that Barden will only deliver a battery to kerbside on a pallet. It weighs 123kg. I've not tried moving a battery that heavy before - can two men move it?

[adam2]

Thanks Adam, I've used vehicle fuses inside the enclosure, but inside their own small enclosures.

What do you think about the hydrocaps though? Good idea?

However, I've discovered that Barden will only deliver a battery to kerbside on a pallet. It weighs 123kg. I've not tried moving a battery that heavy before - can two men move it?

The use of vehicle fuses inside a battery enclosure is not ideal since the fuse element is normally not sealed as in a mains rated HBC fuse. At the moment of failure there will be a spark.
Although the fuses are enclosed, I doubt that the enclosure is gas tight.

The hydrocaps save on water, but not much on maintenance time and trouble. Hydrocaps although normally reliable, do suffer from random failures, the battery water level will then drop as if no hydrocap had been fitted. The battery water level should therefore still be checked frequently.

123 KG is borderline for two men to move. Certainly could not be carried any distance by two men of normal strength.
Movement on the level being possible with a heavy duty trolley or rollers, and lifting one end at a time with a crowbar or lever.
Any significant lifting would need either more manpower, or some variety of lifting appliance such as block and tackle or an engine hoist.

I seem to remember dealing with batteries that big once, and vowing never again !
Greased steel plates, scaffold boards, pulleys, ropes, and an ill behaved horse all featured in the job, which took all day for 6 batteries.

[mikepepler]

Thanks Adam. The fuses are a bit like this one: http://www.ebay.co.uk/itm/220950525782

I think what I'm going to do is reorganise the area under the stairs over the coming weeks, and see if I can find a better place to site the electrics, then I can get on with moving the fuses and make a hinged door for the battery compartment. Finally after that I can look at what type of battery I should get - though it sounds like you think there shouldn't be much of a hydrogen issue with the two I have at present, so it's not urgent.

What makes of batteries do you recommend as alternatives to that Rolls 12V one? They don't make any smaller 12V ones in their 5000 series, the best I could do would be to get three 4V batteries - the 6V are still 100kg! But maybe another manufacturer does other sizes?