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View Full Version : Fuses & winches - question



Cuppa
21st March 2012, 05:21 PM
In my Patrol camper I have a Warn winch - XD9000 which can draw up to 460 amps under full load.

I plan to utilise the 'house/ auxillary' batteries in conjunction with the starter battery when winching.

To date I have never used a winch in a recovery situation - so am green in that respect.

The starter battery is under the bonnet, the house batteries (3 x 120Ah AGM's) are in the canopy behind the cab.

I will have a heavy duty cable running between the two sets of batteries via a suitably rated manual battery switch.

The cable needs to be fused at each end & I'm hoping someone here might be able to assist me to work out what size fuses I need to use.

A mate with an OKA only has 200amp fuses in a similar set up. He carries his winch 'loose' & says "I have 2 sources of power for it. One at the front and one at the rear, and the winch ''plugs in'' to either. Both sources are very close to the batteries (either the crank or the house). Both sources have 400A isolators, so I can manually isolate the power in case of a problem.
The cable between the house and crank systems (via the VSR) is 70mm2 and that is fused with 200A at each end.The winch draws power according to load. Fuses take an overload for quite a while. If you are using full power from the winch you don't want to do it for more than a few seconds at a time anyhow because it will get VERY hot. So there is some 'leeway' there.

I have found a local (ie.Australian) source of 'megafuses' & fuse holders rated up to 500amps (boy that wasn't easy!) & was thinking of using 450amp fuses, but after hearing what my mate has said about 200amp fuses doing the job because they are slow to blow & winching at full load should be restricted to short bursts I'm uncertain if 450amp might be too high? (Cost is the same as lower rated ones).

Would anyone here care to confuse me further by telling me what works for you, or what you think I should do?

Thanks
Cuppa

the evil twin
21st March 2012, 07:42 PM
Easiest way look at it the same as a Starter Motor and... don't bother fusing it. Most Winch Manuf doesn't usually supply fuses either and the cables are pre-terminated for direct connection.

There are a few reasons why High Current Devices have no fuse. One of them is that every connection in a high current path is a potential high resistance point. In high current situations even a few Ohms resistance can generate lots of heat. If you start with a direct connection for the Positive you have two connection points, Battery and Winch Control Box. If you add one fuse you usually add 2 or 4 more connections depending on pattern, Battery, Fuse Holder (in), Fuse Clip (Fuse) another Fuse Clip, Fuse Holder (out), Winch.

If you fuse at the source the fuse should technically be capable of the wiring capacity however dropping the value so the fuse will 'go' if the Winch is at max load is also an option, up too you.

Your mate is pretty much correct in the quote and if you do fuse it don't forget to carry a spare.

MudRunnerTD
21st March 2012, 08:30 PM
Great response ET, I cant say i have seen a fuse in a Winch circuit before and now i know why.

Tweakedoffroad
21st March 2012, 08:44 PM
I would wire the winch straight to the starting battery as that battery is closer to the winch and you will not get voltage drop going all the way to the back, manufacturers recommend and for warranty purposes will not cover it if not connected to the main cranking battery.
Your mate is pretty much correct in the quote, if you are going to use the winch in the rear as well I would not put a fuse in as sometimes u need to winch for a little bit more than a few seconds and would/could be dangerous if the fuse blew mid pull as you would then need to fix the problem when the cable/rope is at full tension

Cuppa
21st March 2012, 09:51 PM
I'm not sure that I have explained well. Hopefully the following wiring diagram will clarify. The two fuses I am talking about are shown as 200amp, between starter & house batteries. My winch will remain in one position on the front of the vehicle. Not sure if this changes any answers???

MudRunnerTD
21st March 2012, 11:50 PM
Hmmmm.....

I dont think that is right cuppa, It looks like you actually have 2x200amp fuses in the one link from your triples (bank) to the crank battery? and an Isolation switch between these 2 fuses? Based on ETs post your looking to have limited potential for hot spots in the link when winching under max potential load, that link has 8 hot spots by my reckoning. You actually dont have a fuse between the winch and the cranking battery in that diagram anyway so why is there a need to fuse between the Crank and the Bank?

Your 3 way switch is a point of isolation at all other times and your quality double insulated wire in the Link will not corrupt during a winch stage so it is either good or not. I think loose the 200amp fuses as being a limitation rather than protection and go with the rest.

You dont though have a fuse from the Bank to the House? or is that just the limit of this diagram and it goes to a Fused distribution point?

It looks well thought out though Cuppa, looking good mate.

Cuppa
22nd March 2012, 08:21 AM
Hi MR,
First I should say that this diagram is the result of collaboration with folk on a motorhome online forum & I have since run it past the tech folk at Redarc who have 'approved' it, although the 'focus' of my communication with Redarc was not those fuses.

The reason (as I understand it) for the fuses between the house batteries & crank battery is to offer protection should the cable be damaged & short out (not to protect the winch). I do understand that each connection carries the potential for voltage drop, but to my way of thinking when the winch is being used a) the motor will be running & therefore feeding the crank battery from the alternator & b) the link between house & crank batteries will be 'contributing' what it can. Although this latter may be a little less than optimal because of the voltage drop reasons ET gives, my hope is that it will be sufficient, whilst giving protection against shorts, especially if I 'oversize' the cable. The bottom line is that the thought of huge amperage shorting out to the vehicle worries me far more that having slightly less than optimal voltage flow from the house batteries.

I do note your comment "quality double insulated wire in the Link will not corrupt during a winch stage so it is either good or not" but my thinking is that if the cable is damaged prior to me connecting the batteries with the 3 way switch that the consequences of a subsequent short when I do connect them could potentially be quite horrific.

So I have the choice of no fuses & hope the cable doesn't get damaged, or fuses which will offer the protection I am feeling I need without blowing when the winch is in use.

I am not trying to argue, or tell anyone they are wrong, just trying to reach a point that I feel comfortable with, whilst acknowledging only limited understanding of matters electrical. Therefore further comments would be most welcome. If anyone wants to tell me that my thinking is 'off beam' I am quite prepared to reconsider.

MudRunnerTD
22nd March 2012, 10:04 AM
Fair call Cuppa, My understanding of all things 12v is based purely on Darren Logic and i have Zero training in the matter.

At the end of the day then, all of the main draw from the winch will be to the Crank battery. All you are really doing is adding your Bank in series when needed. Would it be viable to not attempt to send All of the current from the Bank of 3 to 1 via a single cable? maybe 3 cables, each fused? 1 from each battery? now i am guessing. But i would think that it would reduce the potential Amp spike your most concerned about?

The other note i thought while looking at your diagram, and its interesting that you comment on it above is, Your 70amp Alternator. You have allot of storage capacity there, i know that your Solar is going to be the main supply and top up but the poor old 70amp will really struggle to give you the boost you need when necessary in that system as the bank is massive. There is real benefit in upgrading to a larger output Alternator for your setup. Not withstanding that a 90amp or 120amp will help the topup when winching but will also boost your batteries quicker when on the road. This will mean that (my logic) that you will not need to drive for as long or far before all batteries have had the boost they need?

In a winch situation with your bank connected your looking to have all batteries equalise and provide maximum supply. If you have voltage drop from the bank to the crank then al that voltage drop will cause is slow transfer of supply between? As would be the case with a low Crank battery and a 70amp alternator when drawing 200amps on a winch rope. Solution, Stop winching and allow the Alternator and or the Bank to catchup.

You'd be doing a pretty serious and Long winch mate when that happens though and looking at your setup i am not sure that is your intention?? I know its all about Worst case scenario but you'd want to be in some serious trouble with no time on your side before the system you have outlined will leave you stranded without enough power!

my 2c, as i said Darren Logic ;)

Cuppa
22nd March 2012, 11:43 AM
Hi MR/Darren,

Regarding your argument for a higher output alternator - my thoughts ('Cuppa Logic'). I agree that whilst winching a higher output from the alternator might help a bit , but I doubt an extra 20 or so amps is going to make a huge difference if the draw is 2-400 amps, & it wouldn't be feasible to fit a 400+amp alternator, I doubt anyone with a winch does that. So the batteries are essentially there as a 'buffer' & their capacity is what will limit the length of time you can winch for. As you surmise, it is not my intention to be getting into situations where I would need to be doing LONG winches.

As far as charging the house batteries in 'normal everyday use', the BCDC1240 is a 40 amp charger, so this is the maximum that the alternator will put into the bank every hour that I drive whether I were to fit a bigger alternator or not. Without the use of the winch I have estimated our daily power usage to be around 100 to 120 amp hours per day & would therefore need to drive for around 3 hours to recharge the bank. The solar is for when we are stopped, camped up somewhere. One 130w panel will be permanently mounted on the cab roof, so will contribute a bit after the days driving if the batteries still need it. The rest of the panels are portables, & would be used when camped for a couple of days or more. I would expect all the panels together to feed a maximum of around 125 to 150 amp hours per day into the bank (25 amps x 5 or 6 sun hours per day) so expect that we could remain in one place & be self sufficient in power indefinately, provided the sun was shining. For overcast weather, during which solar input is reduced, the extra battery capacity will enable us not to worry too much. If use of the winch, or longer periods of poor weather mean that the batteries get more depleted (I wouldn't let them drop below 40% capacity as an absolute minimum, generally preferring to keep them above 65% or 70%) then we have two options. 1. If the sun is shining again, solar will gradually take the bank back to 100% because input is greater than daily usage (& we can always economise on power usage if need be) , or 2. We would have to drive for several hours and/or go to somewhere to plug into mains power (I will carry a 240v battery charger), but I don't envisage needing mains power generally (& for the same reason will not carry our little Honda gennie with us).
Having successfully fitted out our bus with solar in which we were self sufficient in power for our 18 month trip around the block, I'm reasonably confident that I've got the solar side of things fairly well balanced, & I envisage the winch as being there for emergencies only, certainly not for regular use. My preference would definately be to avoid getting bogged in the first place - I'm not one of the type of 4WD'ers whose aim is to push the 4wd limits. Nothing against such use - but it's not my thing - I'm just a tourer who wants to 'get off the beaten track'.

Regards
Cuppa

Inkbandit
3rd April 2012, 05:49 AM
Hi Cuppa, the idea of linking your 3 AGM's to help out in a winch is great but not really ideal, as you will be using the bcdc charger (trickle) and not a solenoid(direct from Alt), under winching when linked the AGM batteries will drain and find it hard to recover to power your accesories ie fridge etc due to getting a trickle charge. I have a similar predicimate with my ute at the moment. I have two 100AH AGM's located in the tray to power fridges lights etc which are run of a redarc SBI12 solenoid, I have however installed a momentary switch to assit in starting only, I now plan to install a "common" dual battery tray under the bonnet to house a another N70 "crank" battery, this will be wired in parralel to the main to efficently double thier CCA capicity, there fore leaving the AGM's to keep the beer cold and link if need be if I stall during a pull. Im unsure if you have ever used a winch in anger but these little buggers can draw some current, the 400 amps that you refer to is at max load (anger). winching for 1 second then resting for one second should be enough to get you through and keep the alternator charging the crank battery.

I hope this makes sense, it might not be ideal to your setup but it might be another option to consider

Cuppa
11th April 2012, 04:56 PM
Nope, I've never 'winched in anger' (& hope not to have to really). When you refer to the BCDC as a trickle charger you confuse me. It's a 40 amp charger which is more than I would consider a trickle charger. Admittedly less than the 70 amp alternator is capable of putting out, but the batteries once partly charged won't take the full amount the alternator can output anyway. I did run the setup past the Redarc boffins & they seemed to think it quite workable. I still haven't started to fit the electrics (soon, soon), so currently still have the dual battery system as fitted by Telstra. Auxilary battery under the bonnet charged via a Redarc SB12 VSR, but my intention is to remove this to both save weight & provide an under bonnet spot for an air compressor. A mate with an OKA based motorhome uses his house batteries similarly & does get himself into places where he has to use his winch 'in anger'. It was he who recommended losing the under bonnet auxillary.

regards
Cuppa

cambo
4th May 2012, 07:31 PM
Great info guys just what i was looking for, ive currently got two narva 150amp fuse between both batteries , should be ok for cranking but thats it i think.