Battery expert please?? advice needed

[long512]

Hi All,

looking for some advice on car battery's. We have opened a clay pigeon shooting range at our farm, and my brother is paranoid about how long we can use these batteries before they start to loose the power to work the traps. they are just standard car batteries (new) some 40ah and some 70ah . we run the traps for about 3 hours and they pull around 5 amp max each time they fire but only for around 4 seconds. its hard to say how long in total they continually run but no more than 1.5 hrs i would say???

questions,

1. what is the best way to test/measure the batteries before we remove them to charge?

2. does it cause damage to the cells charging them to much ie after every time?

any advice would be greatly received, i probably need to give you more information, motor size power ect if so just ask i'll find out tomorrow!

also, we are thinking about supplying them from a 12v transformer ( a big one ) but i'm worried about cable size. we have a huge roll of mullticore 2.5 tri rated but when doing my calculations i fear its not big enough? there are 20 traps in total and at times would be 3-4 pulling supply at the same time.
the cable run will be at least 50m they say you cant have more than 3% vd over the run??? using an online cable sizing guide it recomends a cable 20mm to keep voltage drop bellow 0.036v??

what am i missing? my brother recons 2.5 will be big enough coz his mate says so??

cheers allister

 

[telectrix]

1 hour at 5A equates to 5AH. on a 40+AH battery, that's next to nowt. best thing is to try it and see. the transformer idea is not so good. poertability and getting mains power to them for one. and if the traps require 12V DC as opposed to AC, you'll need rectifiers etc.

 

[i=p/u]

Well say you have 5 traps working off 1 x 40ah battery and they pulling 5A for say 5 seconds = 25A @ 25 seconds divided by an hour =144 clays on 5 machines leaving 15ah left lol

 

[i=p/u]

Would you best trickle charging them = long time so extra batteries

 

[long512]

thanks Telectrix!
is that basically how you would work it out?? 1h at 5amp = 5ah? so a 40ah battery in theory should continually run for 8hrs ish??

yeah i have explained the rectification to him and we have or he went and got a power supply built up from a 240 v feed. quote "well i just thought 12volt was 12volt?? i dont know abou that dc sh£t??)

the transformer will be located in one of our sheds, and we will run one "flying lead" to the first of about 10 supply boxes that will be put away each night, using external 24v safety plugs (the purple ones unless they do a 12v one?) to connect each box and then we can mount them on poles near to each trap. 4 sockets on each box, 2 for the traps 2 to create the ring main.

its a lot of work but a good investment. i have tested a rectifier circuit i built up with an 80amp rectifier and it powers a singlr trap well, its just the cable size i need to get right??

thanks again allister

 

[Des 56]

The first thing you should determine is the efficiency of the batteries you are at present using

Using the ampere hour rating,a discharge test should result in 60% efficiciency discharged at the 1 hour rate.any lower and replace them

If you are using and relying on lead acid batteries for your future needs,invest in a discharge tester a hydrometer,a good charger and a voltmeter

One test you can use is for the specific gravity of the electrolyte,so get and use that hydrometer


Another test is voltage off and on charge for the battery as a whole and for individual cells

The good old nose is another,a stinking smell from one of the cells whilst charging would warn of Hydrogen sulphide gas/bent or buckled plates in the cell is another sign of end of days
Residue at the base of the cells will cause big problems also

Make sure the cells are never left short of their electrolyte level,check this when they are charging and at regular periods of use.topping with distilled water as needs arise

 

[long512]

Well say you have 5 traps working off 1 x 40ah battery and they pulling 5A for say 5 seconds = 25A @ 25 seconds divided by an hour =144 clays on 5 machines leaving 15ah left lol

cheers, each trap holds at least 300 clays and we fill them twice over a 3 hour busy period! some bad shots lol! he (my brother has bought a battery for each trap) wait till i tell him he could have used one for 2-4!! more money than patience!!

it is good fun mind, but an expensive hobby. i'm just the poor spark who has to replace relays and cables and the other things he breaks the rough git! lol

 

[long512]

The first thing you should determine is the efficiency of the batteries you are at present using

Using the ampere hour rating,a discharge test should result in 60% efficiciency discharged at the 1 hour rate.any lower and replace them

If you are using and relying on lead acid batteries for your future needs,invest in a discharge tester a hydrometer,a good charger and a voltmeter

One test you can use is for the specific gravity of the electrolyte,so get and use that hydrometer


Another test is voltage off and on charge for the battery as a whole and for individual cells

The good old nose is another,a stinking smell from one of the cells whilst charging would warn of Hydrogen sulphide gas/bent or buckled plates in the cell is another sign of end of days
Residue at the base of the cells will cause big problems also

Make sure the cells are never left short of their electrolyte level,check this when they are charging and at regular periods of use.topping with distilled water as needs arise

Thanks Des, you have lost me a bit though? i can only do this discharge test with an appropriate discharge tester?
is there any test i can do with a good multimeter fluke or other test equiptment? cheers!

 

[telectrix]

for 5A, 1.5mm cable will be more than adequate. volt drop could be a problem if long runs. the 3% figure relates to lighting. for other circuits it's 5%. so 0.6V ( on 12V ). still think batteries are a better idea.

 

[i=p/u]

I'd say maintain the battery's is now your next call ask des for his number and ring him..

 

[Des 56]

Thanks Des, you have lost me a bit though? i can only do this discharge test with an appropriate discharge tester?
is there any test i can do with a good multimeter fluke or other test equiptment? cheers!

These are about as cheap and nasty and specific for lead acid batteries,not the top end type of test equipment,but it will suit your purpose
Durite Discharge Battery Tester - 6-12V - 0-524-08 | eBay

There are electronic testers,but they are more of a sampling tool and may cost more than the type shown

Here is another example of a tool that will be very handy
Battery Hydrometer Electrical Tester High Quality New | eBay

Add a voltmeter and some distilled water from the chemists and your geared up for an easy life

The items shown are little more than a new decent battery and can probably be found cheaper with a longer search

 

[long512]

Thanks guys!

much appreciated honestly, wot a great forum! ask a sensible question and theres always someone out there that can help.
Des i'm off to ebay for a look!
i work in a factory, based in the boiler house, we maintain steam turbine. the water we use to produce the steam through our boilers is treated better than us so getting a bit for the batteries wont be a problem.

 

[ahtyrrell]

Be careful using standard car batteries they are not made for this type of application and do not take constant charging/discharging very well, car batteries or "starting batteries" are designed to deliver very high currents for very short periods of time and are not designed to be discharged more then a few percent very often. The ideal type of battery would be a leisure battery designed for camper vans these look similar to car batteries but are much more suited to cyclic application. Golf cart batteries would have been another good option as they could just be taken in every night and stuck on charge, also much safer as the are sealed

 

[plugsandsparks]

Absolutely, this is not a car battery application. better with caravan batteries as they can be huge and like the deep discharge, bit cheaper too

 

[Robotstar5]

I was going to suggest leisure batteries as above, also if the batteries are kept in a shed, have you considered a PV (solar) panel on the roof to charge them?

 

[i=p/u]

He fits them lol

 

[ruston]

I was going to suggest leisure batteries as above, also if the batteries are kept in a shed, have you considered a PV (solar) panel on the roof to charge them?

Just to stretch the imagination , I know it's not ideal , but will give you the gist. Safe transportation too.
There will be better set ups but this was just a quick Google.

Electric Poultry Fencing - Solar Power Panel Energizer and Dolly Kit | Electric Poultry Fencing | Chicks and Game Birds from Stromberg's |

 

[long512]

thanks guys, i hAD a look lasat night and the majority of the batteries ARE leisure batteries, sorry my mistake in the original post.

thanks for the suggestions, we have a contact that owns a scrap yard and he's gave us some golf buggy batteries too so were on the right track.
with regards to the solar charging, i was thinking of the units that you can buy for your cars to keep there batteries topped up in the colder months. just about £20 each think its worth a look?