Joining batteries with a CTEK 250s DUAL system

[taslucas]

Hello, my GU came fitted with a CTEK 250s DUAL. From what I have read they are an auxiliary battery charger, not a system to link batteries. My winch currently draws from the starting battery but it would be nice to have the option of both. Can I set up to draw from both batteries as per the diagram below or will that hurt the ctek?CTEK winch option.jpg

[PeeBee]

The Ctek Dual is rated at 20a charge rate. I cant see why you could not hook it up as shown excepting the two batteries will try to equalise to a common voltage and then you will only get 20a recharge rate to the house battery and I guess the bit left over from the alternator capacity. Also if the house battery is a deep cycle or dissimilar than the crank battery you may shorten its life. I think for an emergency you could do this or if very infrequently you may get away with it. Also remember your alternator is something like a 5% duty rated top up device, so on longer winching you could end up with both batteries depleted , alternator hot or popping diodes. Few things to consider. When I had my Warn 15000 12v winch, it was fed from 3 hybrid deep cycle/crank batteries via a charge controller/isolator. The charge controller was rated at 80amps from memory. When i wanted to use the winch, I had a parallel cable hook up so I could charge the winch batteries without the 80a limitation. I run a 300amp alternator, and it just kept up with the winch drawdown, but still needed a rest every couple of minutes. The difference between your proposed set up and mine is the greater capacity, so depth of discharge is shallower, hence recovery of battery voltage quicker, and the alternator was very large. As mentioned you will probably succeed with your proposal for infrequent and careful management. Hope this helps

[taslucas]

Thanks for the info mate. The idea was to only use the house battery in an emergency if the crank battery is not viable. How about if I put another isolator between crank battery and winch so then the winch can draw separately from either rather than both? And if so, would the winch earth need modifying?

[PeeBee]

Thanks for the info mate. The idea was to only use the house battery in an emergency if the crank battery is not viable. How about if I put another isolator between crank battery and winch so then the winch can draw separately from either rather than both? And if so, would the winch earth need modifying?

Winch earthing will be fine, its common to the chassis I am imagining at some point. Are the batteries the same, ie both crank or crank for start and deep cycle for house? Deep cycles dont cope with high current drawdown at all. A few guys simply run the winch supply off the crank and make sure they dont turn the vehicle off prematurely or before the voltage level has recovered. If you go the isolator, that overcomes the issue you raised around 'unviable', as linking a good to an unviable will just generate two unviables! I think your isolator should be like a Blueseas battery selector switch and then you can select both batteries, crank battery or house battery independently. they have good amp ratings for the duty rating. Something like this
https://www.ebay.com.au/itm/22267249...3ABFBMuO39it1i

[taslucas]

Awesome, cheers. I haven't purchased the second battery yet. I was just going to go for a lead acid deep cycle to keep cost down. Camp trips are likely only overnighters with very little "house power" needed.

.......from under the great down under.

[PeeBee]

Awesome, cheers. I haven't purchased the second battery yet. I was just going to go for a lead acid deep cycle to keep cost down. Camp trips are likely only overnighters with very little "house power" needed.

.......from under the great down under.

OK, I would go with crank for start battery, deep cycle for the normal camp stuff and keep a set of jumper leads for the odd occassion when you deplete the crank battery during winch, or even if you want to parallel the batteries. This would work as well as the Blue Seas switch. I understand the CAT brand batteries have great capacity, they are crankers but have good life as deep cycling as well, not that much dearer than an exide or full river equivalent.

[pollenface]

The proposition looks viable to me

I did the same thing with a D250S although just had a small length of cable I kept ready to screw into position between the start & aux terminals on the Ctek unit (thus joining the batteries together in times of need).

[taslucas]

Do you mean you had both the positive from aux battery AND a bridging cable across the ctek terminals?

[mudski]

FWIW.
I run the D250S with a deep cycle aux battery. Wired in the same as your current setup. I've never had the need to look for more battery power when winching in the last 10 years I've had it setup this way. Not saying that I never will though...

[taslucas]

FWIW.
I run the D250S with a deep cycle aux battery. Wired in the same as your current setup. I've never had the need to look for more battery power when winching in the last 10 years I've had it setup this way. Not saying that I never will though...

Yeah sweet. Ok I think I'll leave it at that and use some jumper leads if I ever need to steal more power.


.......from under the great down under.