Charging a 12v SLAB

[raynerd]

I have recently got my foundation licence for amateur radio and I want to go portable. I tried lugging a 12v car battery around with me but even between two of us, my dad and I struggled to carry it and gave up half way up the hill to set up camp before getting to the peak. I`ve kindly been given two SLAB - sealed lead acid batteries from work that are apparently ideal for portable use. They are these:
http://www.prolite-lamps.com/products/batteries/lead_acid/pdfs/NP7-12DataSheet.pdf

They are 12v/7Ah, will a standard car charger do the job of recharging? I don`t want to fry them so I was hoping someone might know the best way to charge them.

Chris

[andyf]

Hi Chris,
You could certainly charge them using a car battery charger, but the problem with sealed batteries is knowing when to stop. Old-style car batteries had a removeable cap on each cell, so you could see the electrolyte and stop when it was gassing freely.

Unless you are sure that your charger can sense when the job is done and switch itself to a trickle charge, it might be better to get one like Maplins stock number JC87U, though they are currently out of stock, and cheaper versions are doubtless available. Or you could roll your own: http://www.myra-simon.com/bike/charger.html

Edit - that circuit is for a trickle only charger, rather than a full charge which switches to a trickle when the job is done, but the author says it will charge his battery up overnight.

Another option which occurs to me is that it might be worth investigating the chargers for 12v battery-powered golf-club carts and lawnmowers. They may have the trickle facility.

  I don't know if keeping the batteries in the car connected to the cigar lighter socket so that they charge up as you drive around would work. 

Andy

[HS93]

a lot of the model boat people just put a 12 car dashboar light bulb ( the type in older car instruments ) in line when charging with a car charger, dont use the chrger on BOOST. just solder a pair of wires on the bulb so it can go in series, you will see the buldlight densety chang over the charge time. ill take a picture of the type I mean and get the watage.
that type of battery can be obtained cheap from alarm companys second hand for free, as the have to change them by date not condithion and you will get a year or two out of them.

Peter

has there been a post removed ???

[John Rudd]

I use sla batteries in my flight box for powering my starter and glo panel and have the following advice to offer.........


Sealed lead acid batteries require a constant current constant voltage (CC/CV) charging regime to prevent damaging the cells.

Generally speaking charge termination occurs when the cells reach around the 2.2v value (a typical 12v sla battery terminates around 13.8v)..

You are best following the manufacturer's recommendations for charging. Do not use a standard car battery charger.............

Dont allow the battery voltage to fall below the minimum either(data sheets...) else the battery will not recover....

You could build your own charger that will suffice, built from readily available components....

here's one I built that works very well.. http://shdesigns.org/gcellchg.html

[HS93]

""Sealed lead acid batteries require a constant current constant voltage (CC/CV) charging regime to prevent damaging the cells.""

yes I know, that is what the bulb is for to keep the voltage constant, the charger itself keeps the curent constant

AS I SAID BOAT model boaters have been using this methoud in our are for years, with no problems..

Peter

G0PAH

[John Rudd]

""Sealed lead acid batteries require a constant current constant voltage (CC/CV) charging regime to prevent damaging the cells.""

yes I know, that is what the bulb is for to keep the voltage constant, the charger itself keeps the curent constant

AS I SAID BOAT model boaters have been using this methoud in our are for years, with no problems..

Peter

G0PAH

So if you knew this, why did you not post up and offer the best advice as the op asked for?

I'm am somewhat offended by the tone of your reply to mine......

Perhaps I ought to keep my opinions to myself in future?

[HS93]

. Do not use a standard car battery charger.............

following my post you posted this, the oppersit to my post, but no reson why.

Peter

[Brass_Machine]

Play nice guys. I am sure this was just a simple misunderstanding on tone. Written word doesn't translate very well. Shake hands  

...
Perhaps I ought to keep my opinions to myself in future?

No... all opinions are wanted and valued. So please don't refrain from posting

[John Rudd]

. Do not use a standard car battery charger.............

following my post you posted this, the oppersit to my post, but no reson why.

Peter

Car type battey chargers are not constant voltage or current......

I referred the op to view the manufacturer's website for recommendations on charging to ensure longevity of the battery and to ensure personal safety is not compromised..

[SKIPRAT]

Hi Chris
you may know from the previous posts  the charging requirements for lead acid batteries and sealed lead acid and gel batteries are quite different .As for me i took the easy way out and went to Argos and bought an eight Amp automatic charger with a switched setting for gel batteries or normal lead acid and also a  switched trickle charge it has been used a lot to charge up some hefty ex wheelchair sealed gel batteries and also some smaller ones that i use for amateur radio operation whilst operating portable from some remote hilltop hope this has been some help to you.

Cheers Paul

[raynerd]

All advice and info welcome!

Skiprat - that is cheating!  lol, only kidding you, seems an easier solution.

John Rudd - I`m also going to have a bash at building the one in the link (http://shdesigns.org/gcellchg.html). I`ve just ordered the LM317T volt regs as it is something I don`t have in. Just purchased now off ebay so should be with me shortly. I`ll let you know how it goes!

HS93 - thanks for the advice but I fancy having a go at making the charger unit, I like building things

[crabsign69]

get a cigaret light plug and plug it in the car no problem couple little drives and its charged


was thinking you could use one of those jump boxs as wel that would work well and its all self contained

[HS93]

have a look at the kiys on the link sometimes it works out as cheap to buy a kit than get the bits individualy plus you get a circuit board.


http://www.quasarelectronics.com/smart-kit/1095-lead-acid-battery-trickle-charger.htm

http://www.quasarelectronics.com/batteries-chargers.htm#Battery-Chargers

Peter

[75Plus]

Chris,

Here is a battery charger/power supply I posted back in January. The circuit uses two LM317's so you can not only pick the voltage but you can also limit the current available to the load. I made several back in the late 80's for myself and friends. I have used mine frequently for over 20 years and have never had a problem with it. I am currently charging a Lithium Ion battery in a cordless drill that came to me without a charger.

All the components are mounted on tie strips and no circuit board is required.

http://madmodder.net/index.php?topic=2551.0

Joe

[raynerd]

Well I am having some probs with this build,the output voltage is max 8.8v.. Instructions say adjust the pot for 13.4v output but it just won't go high enough! I may very well build yours as well joe but for now going to get the one in johns link working! Any ideas guys?!?

[Bluechip]

Chris

You should have said re: LM317T, I have loads of 'em you could have had. For nowt ..

Was considering hawking 'em on Antiques Roadshow .. he.. he  

Never use the things, always used a L200 since 1979 for regulators / battery chargers.

Whole heap more reliable.

No minimum output current.
Heatsink tab is Ground, not at some voltage. Nail it to the nearest bit of metalwork. (EDIT Unless you need an isolated output )
Never had one die through having a charged battery on output, with no DC input.
(LM317's don't like it the other way, you have got a diode across it ?? )
Just one chip does voltage regulation and current limit..

All for £2 unless you go to Maplin ( hawk, spit, p'tooing )


http://www.st.com/stonline/books/pdf/docs/1678.pdf

Batt. Charger cct. in this .pdf ........ >>>

http://www.st.com/stonline/books/pdf/docs/1318.pdf

Sorry, no real help.

Usual thing with electronic stuff, if it works, fine. If not, you're on your own ...   too many variables with DIY circuits.. )


End of regulator chip flaming war    

Dave BC