Cheap battery charger

[Dave_P]

I had a 40a multi-stage sterling charger. One day it stopped working. I put it on the back-burner of jobs since my solar panels were doing the job. From some investigation it may not be a problem with the charger but something else, not sure yet. Then autumn came and my solar started to lag behind my electrical demand. So, as a cheap stop-gap, I bought a 12a Halford charger for £40 and clipped it straight to my battery bank. It says it can be left on as it has a float stage. It's been doing fine for the last few weeks.

 

With that in mind, why would I want to get a new 40a Sterling/Victron/whatever charger? I'm thinking there must be a problem with my Halfords cheapy, but I don't know what it is.

 

[rusty69]

I have been wondering the same. Have just plugged my battery charger in after deciding the solar season has gone. I have noticed that the charger I have doesn't have a very high voltage output, and certainly won't do a 14.8 V equalisation charge.

[WotEver]

The main difference is that the 40A charger will bring the batteries back from a deep discharge up to around 80% three times faster than a 12A charger.

 

The Sterling will also have adjustable voltage to optimally suit the batteries being charged. For the avoidance of doubt I am talking about continuously-variable voltage not just a setting for 'wet', 'sealed' etc.

 

Otherwise they both have Float meaning they can be left permanently connected.

[Dave Payne]

I did this when i was in the marina, same charger i am guessing, left in all the time and had no problems, obviously i only used the 12v for lights, pumps as the fridge and tv and other charging stuff was all done over the hook up.

 

I agree that if you have access to a 240v hook up and dont run power hungry things off your batteries then its a good idea over spending big money.

[Arthur Brown]

If you keep up with electrical consumption over the next few months then it's fine! If not then it's not!! However I'd always want a spare charger if I needed to use 12v and had mains.

 

Make certain that the starter battery gets some charge so that the engine will start when needed.

[Robbo]

My guess is that it only has two stages, bulk and float. If it doesn't have a absorption stage you'll be undercharging. In addition the AC neutral and DC negative are more likely to be connected which is a no no for perment installs (marine battery chargers have a isolation transformer so the negatives aren't connected).

Edited November 11, 2016 by Robbo

[Ex Brummie]

I have a 20amp Hilka charger commoned up with my solar panel. As I only spend occasional nights on the boat, and switch the charger on then, I have no problem. Liveaboards obviously have much greater demands than me, and no doubt push to the hilt, but if you have a reasonably sized harger commonred with solar, then it should work.

Of course, people always look to get the best possible output for the least possible input. Don't push the limits andyou will be O.K.

[bizzard]

I probably use the same 12a Halfords charger. Gave a fiver for it ten years ago. From a battery voltage of about 12.2 it bulks at 13.6v for about 4-5 hours or so and then it creeps up to 15-15.1v and remains there for about 30 mins and then drops back to 13.6v float. Battery nearly 5 years old now and has not lost very much capacity at all.

Edited November 11, 2016 by bizzard

[ditchcrawler]

In my view if you are on a shore supply 24/7 even if everything on the boat is 12 volt you shouldn't need a big charger, just think, 24 hours at 10 amp is 240 Ah per day, do many people use that much electricity without an inverter powering mains appliances

[Murflynn]

In my view if you are on a shore supply 24/7 even if everything on the boat is 12 volt you shouldn't need a big charger, just think, 24 hours at 10 amp is 240 Ah per day, do many people use that much electricity without an inverter powering mains appliances

but it won't actually provide 10A continually for the 24 hr period, will it?

 

therein lies the basis for using a proper charger.

 

I use one of these, and find it provides good service:

 

http://www.ebay.co.uk/itm/12V-20A-Connect-and-Forget-Leisure-Battery-Charger-Caravan-Motorhome-Boat-/112001116420?hash=item1a13c96904:g:qMYAAOSw7I5Tw788

[Dave_P]

Still confused. More questions:

 

1. What is an absorption stage? What will happen to my batteries if my charger doesn't have one?

 

2. Looking at Murflynn's last post I still can't see how 12a charger can be lacking for me. Even if my charger averages 5 amps over 24 hours, that's still 120 amps going in to my batteries? When I'm hooked up, my 12v runs my fridge (max 50a per day, being generous), my lights (led) and my pumps. Surely there's no reasonable prospect of taking more out than the charger puts in?

 

As far as I can understand, a big charger 40a or more is only useful if you're charging your batteries off a portable generator, so you can do the maximum of charging in the shortest time. When I'm off my mooring, I charge with solar or engine alternator of 70a. So the charger is irrelevant?

 

I suspect that most boats do this (unless they have a genny), so why do they often have such big chargers?

 

I can't see a good reason for removing my £40 charger and putting in something like this for over £300 https://www.marinesuperstore.com/batteries-power-chargers/battery-management/sterling-power-procharge-ultra-charger-12v-40a

 

Happy to be convinced otherwise though.

Edited November 12, 2016 by Dave_P

[Robbo]

You can get a decent Victron for around £130, you don't need to spend 100's. You don't need a big charger as you say, and if your on shore power it's better for the batteries if you don't.

Edited November 12, 2016 by Robbo

[WotEver]

Still confused. More questions:

 

1. What is an absorption stage? What will happen to my batteries if my charger doesn't have one?

For the answer to this and much more, take a look at this post: http://thunderboat.boards.net/thread/817/battery-charging-primer

[Bugsworth Tippler]

but it won't actually provide 10A continually for the 24 hr period, will it?

 

therein lies the basis for using a proper charger.

 

I use one of these, and find it provides good service:

 

http://www.ebay.co.uk/itm/12V-20A-Connect-and-Forget-Leisure-Battery-Charger-Caravan-Motorhome-Boat-/112001116420?hash=item1a13c96904:g:qMYAAOSw7I5Tw788

 

 

I was about to purchase one of these today and asked the firm if they were suitable for charging a bank of 3 x 135 ah batteries. They told me I needed a 40A charger.

 

Were they correct? Wouldn't a 20A charger do they same job but slower? Apologies if this is a stuopid question.

[WotEver]

 

I was about to purchase one of these today and asked the firm if they were suitable for charging a bank of 3 x 135 ah batteries. They told me I needed a 40A charger.

 

Were they correct? Wouldn't a 20A charger do they same job but slower? Apologies if this is a stuopid question.

It's not a stupid question but it doesn't necessarily have a simple answer. It's quite possible that they were simply trying to up-sell you however it does depend on the internal diagnostics of the charger. If it looked at the voltage of three well-discharged 135Ah batteries and then charged them flat-out for say 20 minutes, it would expect to see a specified voltage rise. If it doesn't see that then it might determine that the battery is faulty (as opposed to the battery is 'big')

 

I think you need to ask them "Why?".

[Robbo]

 

I was about to purchase one of these today and asked the firm if they were suitable for charging a bank of 3 x 135 ah batteries. They told me I needed a 40A charger.

 

Were they correct? Wouldn't a 20A charger do they same job but slower? Apologies if this is a stuopid question.

The smartguage site answers this, I'll find the link.

It's not a stupid question but it doesn't necessarily have a simple answer. It's quite possible that they were simply trying to up-sell you however it does depend on the internal diagnostics of the charger. If it looked at the voltage of three well-discharged 135Ah batteries and then charged them flat-out for say 20 minutes, it would expect to see a specified voltage rise. If it doesn't see that then it might determine that the battery is faulty (as opposed to the battery is 'big')

 

I think you need to ask them "Why?".

They will go on the 10% rule as because someone told them !

[WotEver]

They will go on the 10% rule as because someone told them !

 

That's quite possible, as I said in my first sentence. However, once OP comes back to us with their answer we'll know. If they say "Because that's how big it needs to be" then it's BS. If they say "Because it could diagnose the battery as being faulty" then that's a different matter entirely.

[Robbo]

Smartguage link here; http://www.smartgauge.co.uk/chargesize.html

[Murflynn]

I use the 20A charger in my link for a bank of 2x110AH - following the 10% rule.

[Bugsworth Tippler]

Smartguage link here; http://www.smartgauge.co.uk/chargesize.html

 

Thanks for that link which I have read carefully. I think the retailer mentioned previously whose receptionist (and a voice in the background) said that I needed a higher amp charger was using the '10% rule' but as they didn't sell a higher amp charger they were actually going to lose a sale not get more money from me. I have bought batteries from the retailer in question and find them very helpful and reasonably priced as well as selling excellent (Banner) batteries.

 

As I am not a liveaboard and won't be taking anything from the batteries except power for the Webasto when the froststat decrees, I think I'm going to get one of those 20A chargers. They seem to be a very good price and the site which sells the 'all singing and dancing top of the range' stuff at 6 times the price just causes me confusion.

[WotEver]

 

Thanks for that link which I have read carefully. I think the retailer mentioned previously whose receptionist (and a voice in the background) said that I needed a higher amp charger was using the '10% rule' but as they didn't sell a higher amp charger they were actually going to lose a sale not get more money from me. I have bought batteries from the retailer in question and find them very helpful and reasonably priced as well as selling excellent (Banner) batteries.

 

As I am not a liveaboard and won't be taking anything from the batteries except power for the Webasto when the froststat decrees, I think I'm going to get one of those 20A chargers. They seem to be a very good price and the site which sells the 'all singing and dancing top of the range' stuff at 6 times the price just causes me confusion.

 

I suspect you'll be just fine with it

[Bugsworth Tippler]

Hello Again

 

Having now got a battery charger I will be connecting it to my bank of 3 x 135ah batteries.

 

Intuition suggests I should connect it as shown in the diagram.

 

 

I have never attempted to load a picture before so, in case it doesn't work, I'll attempt a written description

 

If the three connected batteries are 1, 2 and 3 I would connect the charger to the positive on battery 1 and the negative on battery 3.

 

Is there any reason why this is not a good idea?

 

Ian

[WotEver]

Hello Again

 

Having now got a battery charger I will be connecting it to my bank of 3 x 135ah batteries.

 

Intuition suggests I should connect it as shown in the diagram.

 

Battery Charger Wiring.jpg

 

I have never attempted to load a picture before so, in case it doesn't work, I'll attempt a written description

 

If the three connected batteries are 1, 2 and 3 I would connect the charger to the positive on battery 1 and the negative on battery 3.

 

Is there any reason why this is not a good idea?

 

Ian

 

That is correct. The negative take-off from the bank should also be from the same place - i.e. battery 3, and not where it is shown - battery 1.

[Bugsworth Tippler]

 

That is correct. The negative take-off from the bank should also be from the same place - i.e. battery 3, and not where it is shown - battery 1.

 

Thanks for that. I'll check what the situation is with regard to the battery connections when I next go to the boat.

 

And thanks to everyone on this thread who has been so helpful.