Battery charger wiring advice please?

[Matt341]

HI All,

I recently ordered a Sterling 20 Amp 3 output charger, when it arrived I was surprised to find no leads for connecting it to the batteries.

I know I have left it a bit late to fit tomorrow but went to Maplins and Halfords today, I picked up heavy duty ring terminals to connect to the battery terminals and also some smaller ones to connect to the charger. I tried getting cable but they didnt have a size big enough (I think the max was 15 amp).

I then looked at the manual for the charger and it said to use a 50 amp in line fuse! Halfords didnt sell these, im a bit confused as its only a 20 amp charger! They had 30 amp spade fuses and fuse holders but that was the highest rated they had there.

Do I really need a 50 amp fuse? It sounds very high for a 20 amp charger.

Also, what cable should be used? Halfords didnt have anything big enough, I have standard 16amp household cable and I also have some heavy duty 30 amp cable which I used for wiring in the oven in the house.

Hope the questions dont sound silly.

Im hoping to get the charger fitted tomorrow so look forward to any advice.

Thanks
Ian

 

[VicS]

I am surprised that there is no recommendation in the installation instructions on cable size. Have you read them carefully.

Which one have you bought?

To really advise we need to know the length of the cables in order to allow for volts drop.

They may well end up quite a bit heavier than the "safe capacity " rating for 20 amps.

The fuse must be capable of carrying the max current but must also be no more than the safe capacity of the cable used to ensure that it is adequately protected

If Mr Sterling says 50amp for the fuses then lesser mortals like forumites would not dare to challenge it. It means though that the cables must safely be able to carry more than 50 amps.

 

[Matt341]

HI Vic,

Thanks for your reply,

It suggests a cable size of 6mm for upto a metre in length or 10mm for over a metre.

It wont be any longer than a metre run to the batteries though.

I dont know how to find the size of cable, hafords cable was only rated with amps.

Its just 50 amp sounds a lot when the max output is surely to be no more than 20 amps, or is it? The cable that came with it (small link cable to share the outputs if 3 batteries werent available), is quite thin, I want to try and wire as much up tonight so that its just a case of wiring to the mains and batteries tomorrow. Im assuming the thick cable I used for the oven should be enough, if it can provide a mains oven then surely im not going to need anything bigger just to charge batteries.


Thanks
Ian

 

[Matt341]

Sorry forgot to say, Its the Pro Charge, 20 amp.

Thanks
Ian

 

[Pete7]

Sorry forgot to say, Its the Pro Charge, 20 amp. Thanks Ian

Ian, page 6 of this gives the wire size for different lengths. You might have problems finding a good size of terminal for the wire that will fit on the small terminals of the battery charger. I moved up to the digital version which has bigger charger terminals because I wanted to use 16mm wire.

http://www.sterling-power.com/images/downloads/batt%20charger/Instructions%20A6%20english%20german.pdf

Not much help for you tomorrow, but I bought my cables from Baden Batteries who size them by mm. Do the Halfords wire give the number of strands.?

Pete

 

[Matt341]

Thanks Pete,

That was my concern, the terminals to fit the charger are quite small, if the wire is to thick it wont be able to be crimped.

Im sure the wire we used for the oven was 6mm, it was rated upto 30 amp and its very thick.

As the wire is rated at 30amp then I assume a 30 amp fuse should be used, as Vic mentioned, if the wire is rated less than the fuse then the fuse would be next to useless.

Thanks again both
Ian

 

[VicS]

I'd ignore Halfords current ratings because we dont know on what they are based. It depends on how the cable is run. Singly in free air, in harnesses, buried in walls in the case of domestic wiring etc etc. They cannot allow for volts drop.

6mm² will have a total conductor diameter of approx 2.8mm and 10mm² approx 3.6mm. The nearest sizes in AWG are 9 and 7 respectively

 

[galeus]

Last year I bought a Sterling ProBudget digital 20amp single outlet charger which came complete with battery cables with croc.clips.The cable was about an eighth of an inch thick;I soldered to 8mm ring terminals on to replace the croc.clips.I,d guess the cable length was about 1 metre and no fuse in the cables.

 

[minquiers]

go to your nearest motor factors and tell them what you want , and they will usually have all you need in stock, cable,terminals,and fuses,good luck

 

[NorthUp]

I agree with above, find a motor factors. Look for 120/0.3mm, I think from memory that is equivalent to about 6mm sq., and good for 50-60 amps with 'normal' use (i.e. don't run the length of the boat via the masthead.. DC current..not buried in concrete...etc)

 

[VicS]

Useful table:

http://www.autoelectrics.net/battery_cable.html

 

[Matt341]

Thanks for the advice everyone, its all been really helpful.

I managed to get some spade fuse holders from Maplins (splashproof), 30 amp rating, I checked the charger last night and the fuse in the charger is 25 amp so 30amp wire fuse seems ample.

I then got some 47amp cable (6sq MM) from B&Q, got to the boat and the job went well, as usual it took a little longer to complete than I expected (it took all day near enough!), by the time you have a chat, a cup of tea etc. lol

Once everything was connected up and tacked into place I switched the charger on, SWMBO covered her ears and ran up the bow :s ! Voltmeter was showing 14.7 or maybe a little more. I noticed the lights were a lot brighter! The charger didnt go to Fast charge, it stayed on Absorption, decided not to leave it running while we werent there incase the batteries dried out. I doubt it would have gone to Fast charge as the solar panel had been connected to the batteries so they were fairly full. I imagine it would go to float mode after an hour or so.

Thats another winter job to tick off the list now

Thanks again for all the advice guys.

Ian.

 

[abbott013]

I have just bought a sterling charger and found no leads or fuse holder and fuses, sterling recommend the lives to be fused with a 50 amp fuse which you can buy direct from them, nice 24 carat items. the cable recommended is 16mm as long as the charger is less than 2 metres away from the batteries, I found this site which seem very reasonable for tinned cable. http://www.kojaycat.com/Tinned Battery.htm

 

[ianj99]

I have just bought a sterling charger and found no leads or fuse holder and fuses, sterling recommend the lives to be fused with a 50 amp fuse which you can buy direct from them, nice 24 carat items. the cable recommended is 16mm as long as the charger is less than 2 metres away from the batteries, I found this site which seem very reasonable for tinned cable. http://www.kojaycat.com/Tinned Battery.htm

One of those fuse holders and fuse comes with Sterling's 30amp triple output Prodigital charger so don't know why they don't supply one with the other chargers. (Superb bit of kit, just like their other products, apart from poor sealing against moisture ingress)

I

 

[abbott013]

There is a single fuse holder with fuse supplied, not sure of the amperage because its not in front of me but that is used on the negative lead as wiring diagram shows. a quote from sterling when i emailed them about fuseing the positive leads because also in the wiring diagram it shows the leads are fused,
You do not need the fuse, but its good electrical practice, about 50 amps is fine, yes you can start you engine with the charger on.

 

[ianj99]

There is a single fuse holder with fuse supplied, not sure of the amperage because its not in front of me but that is used on the negative lead as wiring diagram shows. a quote from sterling when i emailed them about fuseing the positive leads because also in the wiring diagram it shows the leads are fused,
You do not need the fuse, but its good electrical practice, about 50 amps is fine, yes you can start you engine with the charger on.

Its in the negative lead on the triple output charger so that the total current from all 3 outputs doesn't exceed the charger rating.

Doesn't obviously make any difference whether its in the + or - lead on single output chargers.

I

 

[abbott013]

I can only tell you what I have read and been told. I have just bought the Sterling pro digital 30, you mentioned moisture ingress, can you tell me if you have had problems with this ?

 

[ianj99]

I can only tell you what I have read and been told. I have just bought the Sterling pro digital 30, you mentioned moisture ingress, can you tell me if you have had problems with this ?

I haven't had any moisture problem as its only been fitted for a month and is in a dry cupboard in the wheelhouse.

But, like their Prodigital alternator regulator that I have on my camper, I am somewhat surprised at the large cable aperture with exposed circuit board and lack of grommet or bush where the cables exit the housing.

It wouldn't have been a big design problem to have grommets which the cable can be run through, that fit into slots in the cover to provide much better sealing.
However, presumably Sterling haven't had any issues or would have done this already. Time will tell whether I am nit picking!

I

 

[abbott013]

I did read in the booklet that they recommend insulated terminals because the charger body is a negative. One little thought after my last post was they recommend placing the charger in a well ventilated place and as such it should run hot preventing any moisture build up.