The whole reason for the selfsufficientish website was to offer a place where anyone can ask, HOW DO I...? So who knows why it has taken us so long to have a HOW DO I? section, but here it is. So if you want to know how to do anything selfsufficientish then here is the place to ask.
Hi!
Im hoping that someone out there can explain to me,in idiot English as I dont do electrics,I dig holes and plant stuff,how can we charge multiple car batteries using a solar/wind turbine.At the moment we are charging each battery individually which is time consuming and of course means that one battery is constantly running low whilst another is on charge. The batteries are different Ah,does that matter? The idea is simple to charge the first battery in the line and when thats fully charged the charge passes onto the 2nd in line and so on,am I in lala land or is that possible? Ive heard about linking each battery negative to negative and positive to positive with jump leads but we want to keep output at 12v not combine the voltage. Can anyone help? Thanks!
As long as all the batteries are the same type (e.g. wet lead-acid rather than a mix of wet and gel-type) then you should be able to wire them all in parallel (neg to neg and pos to pos) to make an array or battery of batteries. Good clean connections required. As soon as you connect them all, the good batteries will charge the flat ones and equalize the voltage across the array. So you need to use thick enough cables to cope with the current. The array will/should settle down to a common voltage.
When you add your solar/wind source it should charge the whole array and raise its voltage en masse.. You really need a charge controller to supervise/automate this process.
If you keep stuffing charge into a lead acid battery it will eventually overcharge and start "gassing" - the water in the battery splits into hydrogen and oxygen off the pos and neg electrodes... and this mixture can be explosive - hope you're not a smoker ! If this happens you will need to top up your batteries with distilled water PDQ
Charge controllers restrict the charge voltage to 13.6v AIUI and some smart ones use pulses of energy to try and stuff more energy into the battery without overcharging.
Car batteries are not the best for storing /delivering solar/wind energy - you need caravan/RV/leisure batteries for relatively continuous energy delivery compared to short 100-amp bursts of starter-motor power. Mixing different types in an array or old knackered batteries with newer ones is probably "interesting". And after a few years whatever you do, you will find that your battery/array's capacity to hold charge/energy has dropped right off. And you can't easily service batteries these days - rip, recycle and replace. Expensive.
wattreesmassive wrote:Ive heard about linking each battery negative to negative and positive to positive with jump leads but we want to keep output at 12v not combine the voltage.
Exactly what Dave said.
Just to explain this part though, if you join several batteries with all their negatives joined together and all their positives joined together, then you will still get 12 volts but the amps available will be the combined battery power.
If you put the batteries in a line and join negative on the first to the positive on the second and continue down the line, and then use the negative on the first battery and the positive on the last battery, you will get their combined voltage (eg 48 volts for 4 bats) but the amps will be the same as availably from just the one battery.
Hope that helps and didn't confuse.
Tony
Disclaimer: I almost certainly haven't a clue what I'm talking about.
Thank you both,I was getting in quite a tizz running around connecting one battery to panel and then charging the next! Ive got better things to do with my time then spend days connecting crocodile clips! Tony,can you explain,what it means to have greater voltage as we have mainly 12v appliances with a few 240 that we plug in an inverter,if we plug a 12v into say a 48v battery "pack" {ie more then one battery combined} will it blow? Im all new to this and keep having "mishaps" Luckily we have a plentyful supply of 12v car batteries so if the worst comes to the worst we can recycle the ones that we mess up but Id like to be able to do it properly!
if you plug a 12volt device (e.g. light bulb) into a 48volt supply (4 x 12 volt batteries in series) then yes it will blow.
Don't do it.
If you have a 12 - volt system and inverter, only ever wire your batteries in parallel (neg to neg, pos to pos), and be very aware of the possibility of high current flows.
Crocodile clips may not handle the current required.... beware...
I used to think 12 volts was safe and nearly burned down my garage.... My 12V solar array was belting out 18 amps and there was a bad connection on a "chocky-block" connector ("bad" meaning high-resistance/dirty/not screwed up tight enough) - it melted and burned! but it survived.. just.
Ask yourself what size cable you need to handle the max current possible... then add 50% for safety. I was using 60-amp cables, but running them thru a lower-rated connection block... big mistake !
When your solar/wind stuff is generating to the max, go around and feel the wires and connections and see if any are getting hot. If they are, you have a potential risk/problem.
Ever seen a paperclip glow bright orange? open it out and drop it across the terminals of a small lead-acid battery - hugely dangerous! - it heats up in less than a second... lead-acid batteries can deliver HUGE amounts of energy very quickly. be careful.
Just by the by, many years ago we set up a Scalextric track on the lawn and powered it with solar panels - for testing purposes of course - marvellous fun !
If you are charging / using multiple batteries in parallel put a silicon rectifier in the lead to each battery. This stops the current flowing back into a dying battery from a good one. Maplins sell them for £0.54 each http://www.maplin.co.uk/3a-silicon-rectifiers-46405
I disagree with the rectifier approach (I think) because you drop a voltage across the rectifier (~0.7v) which will jigger any smart charge controller (e.g. a 13.6V float charge will end up being 12.9v). If you aren't using a smart charge controller then maybe. I had a simple controller once and it was useless - as soon as the sun came out and the battery voltage rose a bit it start dumping energy into its dump load/heater straight away. Smart controllers use pulse width modulation (PWM) to squeeze more energy into the batteries rather than wasting it.
Thanks to you all! I shall have to go back to the drawing board on this one as we dont want any "gassing" or anything that shouldnt be glowing orange! Ok,so I have another connundrum,we bought 15w solar panels from Maplin {God! I love that place!} and on the box it said you could join upto 10 together to increase wattage,but nowhere did it say HOW. I emailed technical services but recieved no reply,so I telephoned and the guy said "just plug one into the other" of course it was only when I tried it that I realised that you could only plug two into each other and then theres no lead to connect to the battery {as its plugged into the next panel! Theres only one lead.....DOH!} Is there any way they can be joined without rewiring them {and invalidating the guarantee!}
Whatever kind of connector they use, get a bunch of the mating connectors. Wire all the new connectors together in parallel, black-to-black, red-to-red. Run wires from the bunch of connectors to your charge controller. Now plug all your solar panels into the connectors.
