12V battery for my solar rainwater pump....

[AV1]

So, the battery (old car battery I had lying around) has failed on my water pump system running a 30 watt pump...is there a battery I should be buying so it last.
Adrian@

[Justme]

All bats will fail quickly if you dont treat them gently / right.

[AV1]

This was an old battery I had lying around and lasted 3/4 months....it has a controller with a relay system  that tripped out as the pump was asking for power, and as soon as I swapped a new car battery on it is back to normal...is there a particular battery I need to buy into.
Adrian@

[SteveH]

 Think the clue is in your post... Old & car battery...

 Also how is it charged & how often is it left less than fully charged...?

 A leisure battery is better designed for the job you are doing... also might be worth installing a low voltage cut-out to stop over discharge....

[SteveH]

 Is your control circuit a constant load & what power does it draw? Does the relay remain energised for a long time?

[AV1]

Granted it was on old battery....I want to purchase the right one this time.
It is running one one of these http://www.ebay.co.uk/itm/New-100w-12v-7a-Solar-Panel-Charge-Regulator-Controller-/190537779301?pt=UK_Gadgets&hash=item2c5cefc865
so has both over-charge and discharge (the discharge cut-out is what was tripping the float switch governed  timed relay system in and out earlier being operated by the pump load).
I fitted a new car battery (customers car that will need to be back on his car soon!) and all is well.
Adrian@
The pump is rated at 30W and I run the overflow warning system and a level system from the same battery.

[SteveH]

How is the battery charged & how often is it left less than fully charged...?

 If your running it right down over several days to the cut-off voltage & then recharging it, that's not good for any lead acid battery. if you trickle charge with a PV, then I suspect its just an old battery problem.....

[AV1]

Solar, and connected full-time to the panel with a 14v overcharge.
Adrian@

[martin]

That's a pretty crude controller, it'll never fully charge the battery, let alone give it a hefty equalisation charge once in a while to blow the sulphate off the plates...
It's always worth "going back to basics" and doing some simple sums - batteries are an expensive hobby, and easily ruined....
Work out roughly what your daily consumption is going to be (how long at how many amperes draw), and lets us know, along with the output of whatever you're charging it with (pv wattage or whatever) and I'm sure you'll get some accurate advice...

[AV1]

That's a pretty crude controller, it'll never fully charge the battery, let alone give it a hefty equalisation charge once in a while to blow the sulphate off the plates...
It's always worth "going back to basics" and doing some simple sums - batteries are an expensive hobby, and easily ruined....
Work out roughly what your daily consumption is going to be (how long at how many amperes draw), and lets us know, along with the output of whatever you're charging it with (pv wattage or whatever) and I'm sure you'll get some accurate advice...

I don't have that technical  know how to work this out...but from what you've said, is there a charger/discharger/ solar controller (smoother as we have for cars in storage) that is out there that will look after a 12v battery AND the system OR do I manage this by discharging and charging with a separate battery to cover whilst I am doing this.
Adrian@

[martin]

It really is simple, and we'll do the sums for you!, but we need to know how long and how often you run the pump, and the wattage of the pv panels - according to how much electricity is going in and coming out of the battery, we can tell you what size of battery (and pv panel), and the type of controller you'll need - if you get the sums wrong you can kill even a good brand-new battery stone dead in weeks

[petertc]

the system i have uses a 12 volt deep cycle battery.
i have 4 x12 volt panels 3 x 15 watt 1 x 18 watt, connected to a 10 amp secta charge controller.
my system supplies 3 toilets and the washing machine in the last 18 months it has used 1.1 kah (1100 amp hours)
it's an on demand pump and has it's own built in pressure switch.
during the last winter battery got down to about 70% charged.

[Justme]

Sounds like a well balanced system with plenty in reserve to allow for the weather.

On average its using less than 1/2 an hours worth of peak PV production per day.

[AV1]

The panel is a 12watt (max output 17.55) running the water pump (30w)  for 2 toilets a water sensor for the overflow tray under a loft tank and level sensor (3 of us in the house and 1/2 flush) and the pump runs for 2-3 mins for each flush 15 times a day (mostly before 9 and after 6) with a anti chatter relay system via 2 float levels...running through the regulator with over-charge at 14v and over-discharge at 10.5v. The pump draw kicked in the over-discharge protection today so the battery (which was never brilliant may not recover, I have it on my accumate now) and from what has been said a better regulator is called for.
Adrian@

[martin]

Excellent - now for some very crude sums (real back of a fag packet job) - assuming we have 15 flushes a day, and each time the pump runs for 3 minutes - so for argument's sake (to take into account any losses), we'll call it an hour of running per day at 30 watts - (2.5 amps at 12v), so every day we need to have that much available to draw from the battery (it's rather like a "profit and loss account") - so we need at least 2.5/3 ampere hours coming in from the pv panel, summer and winter..... (that's the "loss" size of the account)
Your 12 watt pv panel should produce roughly six times the panel's rating per day in midsummer (assuming it's facing due south etc) - so in mid June you have roughly 6 ampere hours of production per day, BUT as the year progresses, it will produce less and less, and in midwinter will probably struggle to produce 1 ampere hour per day............. (and pro rata in the interim months) So somewhere between the two extremes you'll reach a balance (same coming in as is going out), and probably around now it'll be dipping to the position that the system is using more than your poor old panel is producing.... Hence a few dull days and your battery will cream cracker (however good it is) as you're taking more out than you're putting in......
SO, the answer is that the really important thing is that you need a bigger pv panel (I'd say a minimum of 30 watts in total), or you'll just kill batteries - going on the "what would I do" theory, I'd go for a 50 watt panel, 85 or 100 ampere hours of a halfway decent deep cycle battery, and a proper controller (look for the magic "pwm" - power width modulation) - which is affordable, but is a good way of keeping your battery in good nick!