UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Other Discussions > Homebrew Equipment

Notices

Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members.

Closed Thread
 
Thread Tools
Old 26th May 2021, 5:41 pm   #1
mark_in_manc
Octode
 
Join Date: Nov 2011
Location: Manchester, UK.
Posts: 1,872
Default Simple questions on battery chargers

Hi folks

Somehow I have ended up the three enormous, variously elderly battery chargers whose control systems are either absent, or look like they spent every bit of the last 30 years they did spend, in a damp shed. None work.

So now they are really big metal boxes with a heavy transformer and rectifier inside. I was looking at an easy way of making them useful, and this appeared

https://www.ebay.co.uk/itm/263205621...kAAOSwmFpZuT~C

But I need to ask - is it OK to use what I assume is some kind of switch-mode thing on the primary side of a big dumb transformer with a big dumb rectifier on the other side? Also, at least one of them used to control by monitoring the current it supplied (there is a large, presumably temp-stable metal strip resistance in series with the load with sensing terminals across it) whereas that Chinese device seems to work by monitoring the battery voltage. I wonder if this is important.
cheers
Mark
__________________
"The best dBs, come in 3s" - Woody Brown
mark_in_manc is offline  
Old 26th May 2021, 10:23 pm   #2
Bazz4CQJ
Dekatron
 
Bazz4CQJ's Avatar
 
Join Date: Apr 2009
Location: Oxfordshire, UK.
Posts: 4,924
Default Re: Simple questions on battery chargers

I have a homebrew battery charger built around an old RS transformer with quite a few taps on the secondary, so I can set it to low, medium and high charge rates. That's all capped off with a relay and a zener that switches off the secondary circuit when V =14.8 (or pretty close) and this simple cut-off has worked very well for some years. Crucially, for me it has meters for both voltage and current, so you can see exactly what is going on. I wouldn't have the meter-less things currently on offer anywhere near the house.

The ebay module may very well do the job; for the princely sum of £3.86, it's worth a look! The rule these days with many modern batteries seems to be keep max current to no more than 4A, whereas I think higher rates were used back in the day when we all had a bottle of distilled water next to the battery charger! If it wasn't gassing nicely, it wasn't fully charged .

B
__________________
Saturn V had 6 million pounds of fuel. It would take thirty thousand strong men to lift it an inch.

Last edited by Bazz4CQJ; 26th May 2021 at 10:30 pm.
Bazz4CQJ is online now  
Old 26th May 2021, 11:30 pm   #3
Terry_VK5TM
Nonode
 
Terry_VK5TM's Avatar
 
Join Date: Oct 2010
Location: Tintinara, South Australia, Australia
Posts: 2,324
Default Re: Simple questions on battery chargers

I would think, if you've got a fairly discharged battery connected, the turn on surge through the transformer would weld the relay contacts together after a while on that module.

As Bazz says, cheap enough to give it a try and see what happens but do make sure your transformers are sound before messing with them.
__________________
Terry VK5TM
https://www.vk5tm.com/
Terry_VK5TM is offline  
Old 26th May 2021, 11:45 pm   #4
emeritus
Dekatron
 
Join Date: Jan 2012
Location: Brentwood, Essex, UK.
Posts: 5,316
Default Re: Simple questions on battery chargers

Although I do now have modern chargers with electronic control, before I got them I used a simple car battery trickle charger in conjunction with a lamp board to limit the charging current of small lead-acid batteries by selecting a 12V bulb of the approriate wattage to determine the charging current. Bulb brightness gave a good visual indication of current and hence state of charge.
emeritus is offline  
Old 27th May 2021, 9:12 am   #5
paulsherwin
Moderator
 
paulsherwin's Avatar
 
Join Date: Jun 2003
Location: Oxford, UK
Posts: 27,787
Default Re: Simple questions on battery chargers

I do wonder if it's sensible for the OP to spend lots of time and money trying to revive this knackered old kit, which sounds like little more than scrap metal. Power supply equipment has evolved a lot since these chargers were made, and it's difficult to imagine a practical use for them even if they were in perfect condition.
paulsherwin is offline  
Old 27th May 2021, 4:21 pm   #6
mark_in_manc
Octode
 
Join Date: Nov 2011
Location: Manchester, UK.
Posts: 1,872
Default Re: Simple questions on battery chargers

That's fair Paul. Not many people are as adverse to letting things go as I am. Well, maybe I'll have a play - I put the question up to see if (as is often the case) I am missing something straightforward and (myself excepted) widely known!

Thanks all
M
__________________
"The best dBs, come in 3s" - Woody Brown
mark_in_manc is offline  
Old 27th May 2021, 5:24 pm   #7
Bazz4CQJ
Dekatron
 
Bazz4CQJ's Avatar
 
Join Date: Apr 2009
Location: Oxfordshire, UK.
Posts: 4,924
Default Re: Simple questions on battery chargers

Quote:
Originally Posted by paulsherwin View Post
I do wonder if it's sensible for the OP to spend lots of time and money trying to revive this knackered old kit, which sounds like little more than scrap metal. Power supply equipment has evolved a lot since these chargers were made, and it's difficult to imagine a practical use for them even if they were in perfect condition.
I'm a bit surprised to hear you say that Paul. Perhaps it is the case that battery chargers fall more under the heading of automobilia than vintage radios? However, on another thread, there is a very long conversation about red light bulbs; quite what heading that falls under, I'll keep to myself .

B
__________________
Saturn V had 6 million pounds of fuel. It would take thirty thousand strong men to lift it an inch.
Bazz4CQJ is online now  
Old 27th May 2021, 5:31 pm   #8
Guest
Guest
 
Posts: n/a
Default Re: Simple questions on battery chargers

I have a "Ring" "intelligent" charger for lead acid batteries, 6 and 12V. It does a very good job and has even recovered a couple of lost causes in it's Hospital Mode. Probably cost less than a new, branded battery.
 
Old 27th May 2021, 5:38 pm   #9
Bazz4CQJ
Dekatron
 
Bazz4CQJ's Avatar
 
Join Date: Apr 2009
Location: Oxfordshire, UK.
Posts: 4,924
Default Re: Simple questions on battery chargers

Quote:
Originally Posted by merlinmaxwell View Post
I have a "Ring" "intelligent" charger for lead acid batteries, 6 and 12V. It does a very good job and has even recovered a couple of lost causes in it's Hospital Mode. Probably cost less than a new, branded battery.
I guess that will include a pulsating mode? I've been an advocate of pulsators for many years and I am totally convinced that they have a very good effect on sulfated batteries, but they don't recover batteries which have died through other causes. I think the pulsator I have produces 16V volt spikes at ~16kHz, though the duration of the spike is too short to measure on any equipment that I have got. I bought it has a kit.

B
__________________
Saturn V had 6 million pounds of fuel. It would take thirty thousand strong men to lift it an inch.
Bazz4CQJ is online now  
Old 27th May 2021, 8:21 pm   #10
mark_in_manc
Octode
 
Join Date: Nov 2011
Location: Manchester, UK.
Posts: 1,872
Default Re: Simple questions on battery chargers

Quote:
Originally Posted by Bazz4CQJ View Post
I have a homebrew battery charger built around an old RS transformer with quite a few taps on the secondary, so I can set it to low, medium and high charge rates. That's all capped off with a relay and a zener that switches off the secondary circuit when V =14.8 (or pretty close) and this simple cut-off has worked very well for some years. Crucially, for me it has meters for both voltage and current, so you can see exactly what is going on. I wouldn't have the meter-less things currently on offer anywhere near the house.


B
On closer inspection, my 24v unit looks like it might have used a multi-tap transformer like you describe, whose taps were once activated as part of some kind of feedback loop. Thanks for your suggestion - that's given me the confidence to have a go at it. It was made by Varta and is convered in German writing, so I imagine the transformer and rectifier might be worth keeping - and there's a huge continental-style ceramic fuse inside too. It's all fairly good stuff, albeit a bit old and dirty.

cheers
Mark
__________________
"The best dBs, come in 3s" - Woody Brown
mark_in_manc is offline  
Old 28th May 2021, 6:20 pm   #11
broadgage
Nonode
 
Join Date: Jan 2010
Location: North Somerset, UK.
Posts: 2,129
Default Re: Simple questions on battery chargers

Back in the days when solid state regulating circuits were just becoming available, but were hugely expensive in large sizes, a type of semi-automatic charger was popular.

This used a simple transformer and bridge rectifier and ballast resistance to give a fast but crude and not regulated charge. When a voltage sensitive relay detected that the battery was almost fully charged at say 14.5 volts, this would "trip" and substitute a much smaller fully regulated constant voltage charging circuit, this could remain connected forever without cooking the battery.

I may still have one somewhere. The unregulated output was about 20 amps, varying a bit with line voltage and battery state of charge, and the regulated output was less than one amp at 13.8 volts.

The relay once tripped to the "slow and regulated" charge, latched in that state and required either manual resetting or isolating and then reinstating the mains supply to fast charge the next battery.
An auxiliary contact on the relay could light a lamp to advise that the connected battery was "done"

The better versions had a "Kelvin connection" to the battery clamps such that the ACTUAL battery voltage was measured and not battery voltage plus losses in the cables.
Standard 3 core mains flex was used, with two cores in parallel for the charging current, and the third core for the sensing connection.
Black sheathed mains flex for negative and orange for positive because red not readily available.
broadgage is offline  
Old 28th May 2021, 8:03 pm   #12
Bazz4CQJ
Dekatron
 
Bazz4CQJ's Avatar
 
Join Date: Apr 2009
Location: Oxfordshire, UK.
Posts: 4,924
Default Re: Simple questions on battery chargers

Quote:
Originally Posted by broadgage View Post
The better versions had a "Kelvin connection" to the battery clamps such that the ACTUAL battery voltage was measured and not battery voltage plus losses in the cables.
I've got that on my homebrew , but it's a bit less essential at my usual 4-5 amps compared with your 20A. One of things I find with meters for both V and I is that no two batteries are alike; they have all had different lives and show individual charging characteristics. Of course, I still have the "old faithful" shop-bought unit from 30 years ago with its selenium rectifier and shaky moving-iron meter (accuracy unknown). It ran almost continuously around the clock in the days when I was working 2m AM with a Pye Vanguard in the 60's, but is rarely used now with modern batteries.

B
__________________
Saturn V had 6 million pounds of fuel. It would take thirty thousand strong men to lift it an inch.
Bazz4CQJ is online now  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 11:11 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.