need some help on this. Aux Alternator on In series batteries and using 12/24V Loads

Good afternoon Guys, So i m a bit confused and need some Help about this. I m currently building an Offroader equipped with winches each draws around 500A on 12V around 250A on 24V. Currently got a Contactor Box which switches from 12 to 24V manually when needed. This system when is on 24V one battery is not charging therfore the AUX Battery is Always getting weaker when switched back to 12V the charge flows from Vehicle Batt to the AUX Batt which every now and then the Aux Battery would need replacing. The System I was thinking consists of Aux Alternator 24V for 2 AUX Batteries which are to be connected In Series. I ve got 3 winches , 2 to be supplied 24V and 1 12V. Now i got some options in mind , Opt 1: Can i Run 12V winches from a single battery as sounds the easiest way out with 24V Alt. Opt 2: Vehicle alt for Both Batteries and keep this 12/24V Box But would like to modify charging system to keep both batteries healthy. ( Got in Mind if i Put Vehicle Positive lead on Batt 1 VEH and Ground Lead into a contactor and on Batt 2 AUX. The Contactor switches the Negative from Batt 1 VEH to Batt 2 AUX. when on 12V you are flowing current from Both Batteries, when on 24V The contactor switches Negative From the second Battery ( as it will be used in series for 24V winching) and put Negative on Batt 1 to keep charging.

Many Thanks much appreciated if you could help me out on this.. I m a bit stuck on what to go and best options what are.

Sounds like you've quite a vehicle there :-D

My personal opinion on winches is to try and use them on a separate system from the vehicle's operational system. Winches can draw a lot more current than even high output, low rpm optimised alternators can produce and there is always the risk of reaching the point where the vehicle stalls out and cannot be re-started.

In your application, I'd look at a dual alternator setup with a 12V vehicle system, and a dedicated 24V system for the winches with dual batteries - you may wish to run other auxiliaries like lighting, fridges, etc, of that too, if applicable. For redundancy, I'd look at using the same batteries for all, so if you lose the 12V battery or alternator, you can swap them around to get you out of trouble.

However, some vehicles may not have room for driving dual alternators, and there are some available with dual outputs, 12V and 24V that can be run together for setups like yours - very $$$$, though. For example, http://www.wolverinetechnologiesllc.com/DualVoltageAlternator.html

While looking the alternators I had in mind - not as easy as I thought, but I have seen them - I came across several boat forums with similar discussions. Many run the 'house', or main power, off 12V but run 24V winches. For example, https://www.sailnet.com/threads/dual-voltage-alternators.271657/

There are also things called 'equalisers', which are designed for running 12V appliances from 24V systems while balancing the draw from, and charging of, both batteries. Waytek (sp?) and EATON apparently offer them. I don't know what level of current they support, but if it's high enough, it may allow running the 12V winch from the 24V system without needing to tap into the vehicle's 12V electrical system?

Hi Gord you Seems to know how to get the Job Done well :D .. So in another way let's say i leave the vehicle 12v as original equipped. Then do a second alternator of 12V to help charging faster. If I keep the 12/24V System to save costs how can alter it to make the second battery charge from the alternator instead of being connected parallel to the other and getting the main battery dead quickly? I know best way is as you mentioned, 2nd 12/24v alternator connected to 2 seperate batteries only for winching. If i need to get supply of 12V for any other equipment can i get it from just one battery? Thanks

Maybe 20 years, or more, ago ;-) Just trying to dredge up old memories. From looking at the truck pictures (should have done that first ;-) ) much of these comments won't apply, but might help someone else? I've a big soft spot for the old Landy's, neat to see it's being worked hard and still looking very tidy! BTW, there was a chap asking about suspension for 4WD trials, a while back, who was english - was that you?

Hmmm, interesting idea. If I follow it correctly, you would be effectively running two separate 12V systems, bridged to provide 24V as required. In some applications that might work well, but I believe there will be a (literally) potential problem as most alternators, and batteries, use a chassis ground - to do what you're suggesting would require them to be completely separate with one circuit's 'ground' being at the 12V of the other. However, there are alternators that don't, and that use a separate chassis wire to 'ground' the circuit - and there is also the option of using insulated mountings, such as nylon inserts and tensioners, to prevent electrical contact being made. Designed correctly, you 'should' be able to use the same alternator model for both, and so only need one spare.

So, I believe it would be possible, but the 'high' potential circuit will need ALL of it's grounds/earths to be tied to that circuit, meaning return runs rather than chassis grounds. If you go that route, I'd use the 'low' circuit for all the vehicle related electrics as reworking all the chassis grounds would be a massive pain, and the 'high' for the rest that can be given independent returns that don't use the chassis - for example, 12V jackpoints for plugging in equipement (they would need to be insulated from the chassis, though, if the 'body' of the equipent is also grounded), inverters, etc.

[EDIT - from here, it doesn't really apply to you]

You could even use a third battery, with a splitter for charging, and have it dedicated to ONLY the systems that keep the vehicles engine starting and running - with the running, headlights, HVAC, etc, running off the "24V" batteries as best fits their use.

It all will depend, of course, on your exact requirements, but if you need 3 winches on an overland vehicle, it suggests you're going to be going places, alone, where you're going to be very self reliant, and I'd be paranoid about losing the ability to start the vehicle because of a discharged battery, or batteries. Heck, there are some engine-transmissions where there is provision for a left, or right, starter installation - if you're lucky enough to have one, I'd even fit a starter to each, with a cross-over switch if it's needed - or at least keep a spare on board.

Thanks for the reply. No that wasnt me regarding the suspension of the landy :).. what i was thinking is, the alternator got a feed wire to switch 12v through ignition. If you cut that only when giving 24v for the winches will that damage the aux alternator? .. also regarding the main batt lead from the aux alternator could use a contactor that isolates the ground and main so that the battery that is beign used in series when clicking for the 24v supply dont reverse current to the vehicle or alternator? .. circuit of the 24v box attached.

A little distracted with the F1, but that looks like it would work. I would strongly recommend a good splitter for charging the '24V' battery, rather than simply connecting them back in parallel, as there can be rather high currents from cross-feeding for the latter as the charge equalises.

This 12/24v box i ve got it installed. It charges the batteries on parallel and then on once the switch is activated The 2nd batt gets in series but at that moments it stops getting charge from the primary battery. I got in mind to charge the second battery with a seconr alternator so when it drains while using 24v and switch back to 12v they would charge up faster..

That might work, as I said earlier, if you isolate the second alternator - specifically the ground/earth - you can use it full time on the latter, '24V', battery, whether run in parallel or series. They are rare, and may be special order, but there are alternators designed for a positive ground, the output being negative - this wouldn't need to be insulated from the vehicle ground, and the output would be connected to the second battery's -ve terminal with the battery's +ve terminal connected to vehicle chassis - it will mean two electrical circuits, each with an alternator charging full time and one negative ground and the other positive ground. That would keep the vehicle as 12V and negative ground as per normal operation. The winches could be connected +12V to -12V for 24V operation, but, again, they would need to able to run a return to the battery as a chassis earth will just short one battery out.

Another option might be to run a 24V alternator and run the batteries permanently in series, possible with the 12V winch run off one (24V to 12V, and will need to be grounded at the battery, not the vehicle chassis), and the vehicle electrics run of the other with the chassis ground.

You have a LOT of options, all with pro's and con's, so it'll come down to what you think best suits you.

Seems that the Last option is Best... Thanks alot Gord :D Much appreciated

NP.

You may like to post some details of the Landie in the project cars section?

Yeah of course.. i will