Dew Controller

[rockystar]

Hi all, 

I've nearly got all the bits to make myself a dew controller; my current plan (as my original one was getting to become an expensive power box - which I don't currently need), is to attach a dimmer switch and jack sockets to my dob base ( encased in some kind of box ) and then have a removable/floating battery box that I can take inside to recharge, and connect via some kind of power pack connector: http://www.ebay.co.uk/itm/320787525779 or http://www.ebay.co.uk/itm/141767902224

In the battery box, I would like to be able to charge it without having to take it out of the box, so can I add 2 sets of terminals, one for charging and one for powering? Is that even necessary? would I need a switch to change from one to the other? and what kind of terminals would I need and where do I get them from (i was thinking some kind of bolt that I can attach a ring to on the outside and a spade on the inside)?

Here is my diagram: Will this work? Have I done something completely wrong? Any other comments?

[Daz69]

You can use the same one set of positive and negative sockets to charge when not using, and to power your dew heater when you want to, so long as the charging amps don't exceed your fuse for the dew heater. If your charging amps are around 4amp as most chargers are , put 2 sets on, and have different rated fuses on each pair, say 5amp for the charge circuit, and 2 amp for the dew heater. 

Use suitably rated banana plugs for the charger to battery sockets, and RCA's for the dew heater. Try not to have any sockets that are trailing from either box, so get surface mount types. Forget the Tamiya plugs as they become loose and fail. The XT90's are good, but again this would mean that you have trailing sockets. 

2m RCA leads are about £2 a pair, so that does 2 dew bands as each lead has an inner core and an outer shield that will happily take a few amps. Banana plugs can be bought in sets so you get both male and female in red and black, again they're about £4 for 5 of each set. I get all mine just from ebay. 

As for teminals, you would be best soldering it all, rather than ring terminals, although you will need some for your actual battery connection, if that's what you meant?

[rockystar]

thanks @Daz69 I'll have a proper read when I get home and see if I can unravel it

[MarkyD]

You can use the same terminals to power and charge.  You can use 4mm banana plugs and panel mount sockets or I use these for my connections rated at 5A

http://www.maplin.co.uk/p/maplin-2-way-audio-locking-connector-line-socket-fk22y

[rockystar]

Are there any issues with charging it through a fuse? I inferred from Daz's post that this would be ok as long as the fuse is of a sufficient size. Or should I move the fuse into the other box, or have 2 fuses?

[Alpollo]

Generally the charging rate is less then the discharge rate of devices, in that case the fuse won't be harmed by charging through it.

Adding a second smaller fuse to just the charger is up to you, as the other fuse might be too large to protect your charger, generally speaking.

[gtis]

This is what you want for you dew strap to plug in

http://www.ebay.co.uk/itm/like/201201547565?lpid=122&chn=ps&adgroupid=42305674521&rlsatarget=pla-278515753909&adtype=pla&poi=&googleloc=9046347&device=t&campaignid=738081070&crdt=0&ul_ref=http%3A%2F%2Frover.ebay.com%2Frover%2F1%2F710-134428-41853-0%2F2%3Fmtid%3D1673%26kwid%3D1%26crlp%3D172726897139_563391%26itemid%3D201201547565%26targetid%3D278515753909%26device%3Dt%26mpre%3Dhttp%253a%252f%252fwww.ebay.co.uk%252fitm%252flike%252f201201547565%253flpid%253d122%2526chn%253Dps%26adtype%3Dpla%26googleloc%3D9046347%26poi%3D%26campaignid%3D738081070%26adgroupid%3D42305674521%26rlsatarget%3Dpla-278515753909%26gclid%3DCjwKEAiA0fnFBRC6g8rgmICvrw0SJADx1_zA-hZDXXGnrPKhU3xgffTCt4fk_ad0wRd02l-VOhHBDBoCcuHw_wcB%26srcrot%3D710-134428-41853-0%26rvr_id%3D1179096255683

[rockystar]

yeah, got some, thanks

got all the bits, just checking that everything looks ok and will work.

[gtis]

Look forward to see the photos 

lee are you going to the DIY star party in Derbyshire 

[rockystar]

1 minute ago, gtis said:

Look forward to see the photos 

lee are you going to the DIY star party in Derbyshire 

got told I couldn't go because it's mother's day

hoping for some clear skies though, I need a trip out. Are you going?

[Daz69]

Check the output in amps for your charger. If it's around 5 amps, and then use the same sockets to power your device, then those devices are fused at the same rate. You will be way over protected, and your device can theoretically pull up to 5 amps if something goes wrong. If you have a short, the dew strap could get excessively hot and cause damage to whatever it is warming. If you know how many amps (or milliamps) the dew straps pull when both used, (if they are shop bought it will be shown, but if home made then you should have used Ohm's law to work out what the draw is), then use a fuse that is slightly higher. So if they both pull 1.2  amp together, fit a 1.5 amp fuse and separate charge and load sockets.

[gtis]

15 minutes ago, rockystar said:

got told I couldn't go because it's mother's day

hoping for some clear skies though, I need a trip out. Are you going?

Yes booked for Friday Saturday night in a pod

hope we get some clear nights

[rockystar]

this may be a silly question (there are no silly questions... ) but how do I know when the battery is fully charged?

[Alpollo]

Look at the Ampere Hours (aH)or Milli-ampere hours (mAh) that your battery is rated for.

Figure out the charging rate of your charger, it will also be measured in mAh etc.

12v - 1mAh charger would take 10 hours to charge a 10mAh 12v battery.

Other then that, it's a bit of guesswork as a weak 12v lead battery may read 12v with no load, but it's capacity is not yet restored. With a typical car battery charger, it's usually charged when the needle drops to a plateau for a while, however it will always accept a trickle charge so this isn't really definitive. Example when the battery is dead, it may draw 6 amps from the charger at first, then slowly drop and hover around 2 amps. At that point it is "charged" enough at least to be able to start the car, the alternator will eventually restore the capacity if it was in fact undercharged.

This is generally speaking for solid lead acid type batteries, other types of rechargeable batteries require different techniques and precautions. These chargers may sense when the cell is full and shut off as to not overcharge. SLA batteries seem to be able to sit on a trickle charge for some time with no harm, but read your specific directions for your products to be sure.

[Daz69]

I use a 4 stage computer charger for my 110ah caravan leisure battery, and my smaller 9Ah 12v deep cycle batteries that I use for my fishing trips. My caravan battery stays connected to this charger EVERY day, and the computer board inside the charger, cycles the battery to keep it at absolute peak. These chargers have dropped considerably in price, so should be considered above the normal type heavy duty chargers that are still out there. My charger has LED's that indicates it's state, and when I take a battery off charge, I let it rest a while, and it normally reads around 13.6v. 

This is the one I use http://www.ebay.co.uk/itm/Sakura-Car-Van-4x4-Bike-12v-6v-5-3A-Automatic-Intelligent-Smart-Battery-Charger-/301663140633?hash=item463c863b19:g:askAAOSwmtJXa-11 

[gtis]

22 hours ago, rockystar said:

this may be a silly question (there are no silly questions... ) but how do I know when the battery is fully charged?

Lee what battery are you using 

[rockystar]

24 minutes ago, gtis said:

Lee what battery are you using 

I haven't bought it yet - planning on the one that Damian suggested: http://www.ebay.co.uk/itm/201258702190

[Daz69]

You would need a gel charger rather than a standard charger for that battery. My one does gel, as shown above.

[Daz69]

On 07/03/2017 at 16:05, Alpollo said:

Generally the charging rate is less then the discharge rate of devices, in that case the fuse won't be harmed by charging through it.

Adding a second smaller fuse to just the charger is up to you, as the other fuse might be too large to protect your charger, generally speaking.

I've only just seen this post, and would like to add that, if your battery is low of charge, and your charger can put out 5 amps, fitting a smaller fuse will be no good, as the charger (unless it's an intelligent type), will punch in the maximum it can, up to the 5 amps. If it is going through a 3 amp fuse it will blow. You could make a split via diodes to stop the higher charge rate blowing a small fuse on the load circuit, but that's just not worth the hassle, rather than take the easy route and have 2 sets of sockets. That way, you'll have the ability to use both sets when not charging.