SLA Battery Charger for Golf Cart

Check the battery manufacturer's web site for charging data, it should give the charging voltage, maximum current and trikle current...

Then you just need to design a charger to give a constant current just below the maximum charging current until the voltage reaches the acceptable chrging voltage and then the charger must switch to constant voltage charging... when the current has fallen to a specific level indicating a full charge the charger should switch to trickle charging mode...

So a three step charger is needed, quite simple, but only suitable for that particular battery type.

John.

Hi John...

Didn't mean to step on your toes...

Hadn't read your post before I jumped in...

We pretty much agree...

I just save a stage by going for max voltage 1st stage ... this won't give max current for fast charge...but these things usually get an overnight charge any how.

(Unless you play 2 rounds in a day...anyone that fit gets no sympathy from me as they can obviously carry their own bag!..joke don't shoot)

You win the 'got there first' prize ... drat it.

Dunno if you've looked at those 3 stage chips...the one I tinkered with couldn't decide if it was a SMPS or a charger and had the vaguest app nots...ended in the bin....not enough time at work for a 'homer' if it's that much trouble!

Del

Oh go on Del, you know you really want a cart now don't you?

Add a few more wheels and stuff to your trolley and tell 'er indoors its all the rage...

John.

First whats wrong with the old one. The transformer is most of the cost. If its good than the charger can be repaired. Most Goft Cart charger use rectifiers bolted to heat sink. They have numbers on them and can be obtain from electronic supply store.

The weight of the charger is due to the amount of current need to charge the batteries in a acceptable time. Most are 6 to 8 hour charge time.

Most that size use timers some of the newer models have circuit boards that monitor the voltage potential shut them down when they reach a level of approximately 2.5 volts per cell so for a 48 volt system that would be 60 volts.

Yo ..I'm the man for this one...stand back guys...

I ruined my first gell battery by using a car battery charger...stupid boy!...that coupled with the awful design of my speed controller...(I'd forgetten about/not learned about freewheel diodes...whoops )

My best advice...get figures off the battery mfrs website....and build effectively 2 chargers... each voltage regulated to a fixed voltage (from the website data)

1st stage is a higher voltage for initial 'fast-ish' charge.

2nd is a safe trickle charge voltage.

To switch between the two use a low value series resistor to current sense.. when the fast charge current drops below an appropriate level, switch to the 2nd voltage using a comparator/op amp and a relay...

(Of course this can in reality be a single regulator with two different values on the reg pin switched by the relay.)

Now some may say this is crude....but I wasted lots of time with one of those 3 stage regulator chips which had awful app' notes. What I ended up with is simple and reliable...add a led to indicate when it's in trickle mode, and any other bells and whistles you fancy.

Of course this is built as an awful birds nest stuffed in the car battery charger case...but if it ain't bust don't fix it... it's been reliable for about 2 years now.

Being simple..if it does go wrong...fall off my bench etc I can fix it.

I used the transformer from the original car battery charger with a nice big Capacitor to help the odds n sods of circuitry to work nicely...

I expect to be inundated by indignant posts about my cr*p design now... but I just don't care any more I'm 'ard enough roight?

Hi Niks94

Use http://electronicsforu.com/electronicsforu/default.asp for CKT diagram

That link doesn't really help does it?

Couldn't you put a link to a relevant page?

I could not find a 48volt battery charger on that link, could you clear that up for us please?

Is this a single 48 volt battery, or 4 batteries in series?

If the latter, you would be better charging each one individually if life span is important to you!!

Where you'll connect your charger? In N. America, England , or ...

Look for primary voltage of your charger's old transformator, if you have used it before. Most times it will be single-phase not 3, but check it.

Search for a new one with full protection of charging cycle, this will keep you battery live longer. It is a lot good practitioners on Net who will tell you what to do. Find them and call them, avoid jokers.

Questions are not being answered by Niks94.......and I have a new one:-

What is your knowledge level (electronics, Lead Acid batteries etc.), do you need full details or will a few tips on how to set up the charging circuit and what not to do be enough?

To answer or not to answer. This is THE QUESTION.

I need full knowledge, though I have read about the battery charger.

Your help will be appreciated.

OK, now we know that you do not have the knowledge or background....

I would like to say at this point that although you have SLA batteries, if the gassing is very bad, they can release gas through a pressure valve, this gas is highly explosive! You must only work or charge them in a well ventilated area, no smoking and it would be recommended not to wear clothing that could produce static electricity.

Furthermore, large currents can flow when working on such batteries, there are plenty of people around with permanent scarring and the loss of an eye and other body parts(and worse) due to not handling lead acid batteries correctly! Even SLA Batteries MUST be correctly handled at all times.

I am sure that you could find more extensive rules to follow on the web without my help, with regard to the charging of Lead Acid Batteries generally.

It would be a good idea at this point to tell us your full qualifications for such work, for instance:-

Are you at least electrically trained? High and low voltage?

Can you solder?

Can you construct Printed Circuit Boards?

Are you mechanically good and can make a suitable container for the finished product?

By the way, its not going to be very light if you want to go for the full Monty.....but we have ways!!!

How often is the cart used? eg. How long do we have between charges? This question relates to the fact that must we charge overnight, every night or do we have several days to get the charging done?

I a perfect world, any Battery constructed of smaller cells, the best way is to charge each cell individually, as if a cell gets weak, it can get reversed polarised if the battery is still being used. this tends to "Kill" that cell first.

12 Volt Batteries have 6 cells and the cell to cell connections are rarely reachable nowadays, so your Battery Unit is 6 cells, when one is defective, you replace the 6 cells, eg. one complete Battery.

I would guess that yours is a 4 x 12 volt system and it would be best if each Battery was charged individually for the reasons stated above. (if that is true that it is a 4 x 12 volt Battery). Can we do that?

I asked previously about how your 48volt Battery was constructed, you have not replied to this question! Now I really need to know!!!

(There are several other questions from various members that you also have not answered if I remember correctly, its a good time to answer all right now!)

Just a quick comment to what you said Andy, it may be useful to others...

But even though the lead straps linking the cells are not visible these days, if you want to have a high current source and have a spare lead acid battery with a dead cell you can drill down into the lead strap and fix a self tapping screw into it and short out the dead cell to give you a good 10 volt battery (instead of 12 volt)...

John.

That is a great tip Electroman as long as you are able to alter your charger to suit the new conditions, eg. reduce the maximum voltage to around 11 volts, otherwise overcharging and excessive gassing could result. One must be careful of shorting to this new connector, as one should be with the original + & -....

The other point is that this person has SLA Batteries, which would not be (sealed) anymore!!

Its a great point for someone who knows the rules / technology and follows them fully in all respects, but for people with little knowledge or less, it could again be dangerous.

I have used the tip above, many years ago, when I needed quickly a smaller voltage than a 12 volt battery could give me, but the battery as a whole was in a good condition. But it unbalances the cells and I am sure that for the longterm its probably not a good idea at all, except where a cell is already defect as mentioned by Electroman.

But with a name like that ( Electroman), I am sure that he understands fully all the problems and concerns...! We must not forget the amateur!!

Old English Prover " A little bit of knowledge can be dangerous!" Or something like that!!

Talking about Lead+acid batteries:

In old , very old times there were these type batteries in glass cells, could have removable electrodes and be easy to acid change. I have seen them in huge distribution el-power-station/substations as a power source for relay type HV LINE PROTECTIONS. Also used for telecommunications. Some were rated around 200-250 V dc. Any of them are still alive?

Yes lots in conventional Submarines and telephone exchanges....to name but two.

Due to the fact that you can clean them inside and replace parts, some Lead Acid Batteries for Subs are 60 years old!!! And still giving 100% service!!

Thnx Andy

So... now...I am waiting for replacement of some my old organs (they play with false notes!). But I am not so transparent for repairmen. Only acid is good (my family claim). Where is DEL the CAT?

Honey I'm home .. !

(Actually been working for a change )