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Trickle charger for stand by 12v lights


flatfourfan

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SO about 2 years ago, I installed a 12v lighting system in my in- laws place and as they didn't have the money for a panel or solar controller, they requested that we run it through a small battery that was hooked up to the mains on a trickle charger. This has worked great and when the battery went belly up (it was old to start off with) they asked me to install a larger royal battery so that they could have some standby if required. Upon instruction from an electronics store I built a trickle charger using a DC power adapter, diode and presto, charges at 13.4v and everyone was happy. 

However recently the adapter went, so I replaced it and noticed 13.4v output from the charger, but once hooked up to the battery it drops to 12.5v and the lights have started flickering. Once I hook the battery to a regular charger, it works just fine and the battery charges. 

Any advice?

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Going for 12V backup is a handy solution for lights during load shedding. Yes very affordable .

 

Regarding your problem, you may find that with the battery being a bit flat the initial charge current is too high for the trickle DC charger that you built (LM317 perhaps?)

So the flickering you see could be the current limiter of the adapter cycling on and off. The "regular" charger may be beefier and able to supply the current required by the battery.

What AH rating is the larger battery you have put in ? What is the current rating of the adapter you have ?

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3 hours ago, flatfourfan said:

charges at 13.4v

I have a bit of an issue with this strategy. Not because you are doing it... but because every cheap-*ss chinese-made lantern does. If you leave the thing permanently on charge, it eventually cooks the battery. Sure, it takes about two years, so perhaps acceptable. Much worse though, when there is load-shedding on a daily basis, this kind of voltage is too low to rapidly recharge the battery. It's fine if you have an outage once a week, but not for daily use.

So my advice would be to invest a little into a small-but-proper battery charger. Something that at least has an absorb/float distinction. I've seen small Black-and-Decker branded units at Outdoor warehouse. So granted, those are generally in the range of R350-R450, but are in my opinion worth it... even if it just saves you all the time looking for a better charging solution!

Of course, do check your current use and calculate how much current you need to recharge the battery.

I can of course absolutely recommend one of these. Buuuutt.. they are almost 2k.

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Thanks for the advice. I did some sums last night and noted that you're right. The battery seems to take flack when the outdoor lights are added to the mix and it pulls it down too much. If the battery is charged full with the regular charger, then the small one can manage to top it up with no problem, (green charge light shows). When there is big draw, then the red light comes on, (aka.........I'm not coping). 

The battery is a royal 102AH. The adapter is a cheap ac-DC adapter HN-DC138V100. 

I like the look of that B&D charger, but yeah locally, I'm not finding anything close to that. 

https://www.autostyle.co.za/product/ring-automotive-12v-4a-battery-charger/ - No clue on the name for R660

https://www.builders.co.za/Automotive/Automotive-Spares-%26-Accessories/Auto-Electrical/Powerzone-Battery-Charger---Black-(3-8a)/p/000000000000566619 - No name for R690 and also can't get it anywhere locally.

and something like this is going to put me in the same boat as I am now. 

https://www.takealot.com/x-appeal-automatic-battery-charger-xa300/PLID41165270/description

Then there is a China route. 

https://www.midas.co.za/pebble.asp?relid=1729&t=75

I wish that they would let me put in a panel with a controller and all of these issues would be gone. 

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So just spoke to the battery charger shop(hoping to find the B&D unit and they pointed me in the direction of this

https://www.takealot.com/optimate-3-desulphating-charger-maintainer-tester-for-12-v-batte/PLID40732677/description

hmmm, thoughts? This is pretty much at the max of where I want to spend and this seems small.

Edited by flatfourfan
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On 2019/10/22 at 8:55 AM, flatfourfan said:

So just spoke to the battery charger shop(hoping to find the B&D unit and they pointed me in the direction of this

https://www.takealot.com/optimate-3-desulphating-charger-maintainer-tester-for-12-v-batte/PLID40732677/description

hmmm, thoughts? This is pretty much at the max of where I want to spend and this seems small.

Flat4 that one is too small - in the product description it says " Suitable for all types of 12V lead-acid batteries of rated capacity from 3 to 50 Ah "and you have a 102AH battery. it also seems more suited for charging car (flooded lead acid) batteries.

It is preferable to have a charger that is able to be left on your battery permanently (float charging like alarm and gate motor batteries). And it would need to be powerful enough to handle a large enough charge current if the battery was discharged. I could not find charging data on a Royal 102AH sealed lead acid but IMO a max charge current of between C/10 and C/20 would be fine for your battery. That equates to max charge current of between 10 and 5 amps respectively. 

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Check out our own battery charger manufacturer:

https://digisec.co.za/product-category/hawkins-intelligent-battery-chargers/

These are smart chargers which can be left permanently connected to the battery.

If battery needs to be charged it supplies constant charging current but as the battery reaches full charge the charging voltage follows a sawtooth waveform so it doesn't cook your battery.

   

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Thanks for the input guys, so a few things changed last night.

- We changed the battery for a 60ah unit as the larger one was pretty much overkill for them and what they were running. I've taken it and will use it for storage at my place in case they change their minds or want to have more capacity. 
- I was approached by someone in here who offered me their spare charger and low and behold its the ring branded one that was listed above. She says with the usage that the in-laws have it can deal with the amp draw easily and I can loan it for as long as I need it......(she actually said 6 months...lolzzzz). They used it for a similar purpose and it comes with terminal hook-ups for long term use and has had it with no issues for almost a year. 

This is purely a stop gap because they have the space to go with a nice 120w 12V panel like mine and a solar controller is nice and cheap and I'm just trying to convince them. They're happy though and will do the hook-up over the weekend. 

Will provide an update once installed. 

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So, an update..........the trickle charger failed. I thought that it was a once off because it was a bit older, but we got one for them, new out the box and it lasted less than a month before going toast. 

So The in-laws agreed to go for the panel and charge controller. Job done.............and the way that I wanted to do it in the first place. 

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