# Trailer Winch battery



## Ashful (Sep 12, 2017)

Any wisdom to share on batteries for electric winches?  The application is dragging logs onto a 7000 lb. trailer, so we're talking maybe up to eight 40-foot pulls on 700 lb logs, or some mix thereof (eg. the odd 4000 lb. log).

Winch is rated 40 amps at zero load up to 340 amps at 7500 lb load, so although most seem to use light truck batteries, I wonder if this may fall more into deep cycle territory.  It seems most deep cycle batteries are rated over 500 cold-cranking amps, which is less than half that of a typical light truck battery of similar size, but plenty sufficient for this winch.  But, can they do 300'ish amps for an extended pull?

The odd thing is that, by the numbers, the deep cycles don't seem to get higher Reserve minutes or Amp-hour (20-minute method) ratings than equivalent-size light truck start batteries.  Knowing this is the whole point of having a deep discharge battery, I'm guessing there's something I'm failing to recognize, here.

I have room on this winch mount for two Group 31 (i.e. large) batteries, but would rather just buy and maintain one, if it might have sufficient capacity.  Rig will be setup to charge the battery(s) from the truck, as I drive to/from my logging site, and automatically disconnect from the truck when winch is enabled.

Thanks, guys.


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## johneh (Sep 13, 2017)

Deep cycle batters are made to take a deeper discharge
 and come back to a full charge than a reg. car/truck battery 
They produce the same power but for a longer time before full discharge


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## Ashful (Sep 13, 2017)

johneh said:


> Deep cycle batters are made to take a deeper discharge
> and come back to a full charge than a reg. car/truck battery


This part, I understand.



johneh said:


> They produce the same power but for a longer time before full discharge


I do not think this is correct.  They seem to be limited to lower current (and therefore lower power).  I did expect them to have a higher storage capacity, but their 20-minute amp-hour and reserve ratings don't seem to show that.  Check this example:







Note the 31XHD can do 1000 amps, versus the 600 amp rating of the 27MDCST deep cycle.  You'd think this would come at a trade-off with reserve or Ah ratings, but they almost exactly the same.


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## WoodyIsGoody (Sep 14, 2017)

Ashful said:


> Note the 31XHD can do 1000 amps, versus the 600 amp rating of the 27MDCST deep cycle.  You'd think this would come at a trade-off with reserve or Ah ratings, but they almost exactly the same.



The starting battery can deep-cycle but it won't last very long if you regularly deep cycle it. That's the trade-off.


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## Montanalocal (Sep 14, 2017)

I have a tailgate lift on my truck with a battery powered winch to operate it.  It is connected to the vehicle battery.  The instructions with this unit specifically state that one should keep the vehicle running while using the winch so as to keep the vehicle charging unit charging so as to help keep the battery up.

I am puzzled by the statement that your unit would "automatically disconnect from the truck when winch is enabled."  I would think that staying connected and running during use would be a good thing.  Am I missing something?  (probably)


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## salecker (Sep 14, 2017)

You can get a battery idolator that will charge you winch battery or your truck battery.It will charge whichever one needs it the most.With a little wiring you can have it charge whenever you are hooked up to your trailer.


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## Ashful (Sep 14, 2017)

WoodyIsGoody said:


> The starting battery can deep-cycle but it won't last very long if you regularly deep cycle it. That's the trade-off.


Good info.  To be clear, is this something you just believe to be true, or do you have a reference for it?  I run on hard data.


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## Ashful (Sep 14, 2017)

Montanalocal said:


> I have a tailgate lift on my truck with a battery powered winch to operate it.  It is connected to the vehicle battery.  The instructions with this unit specifically state that one should keep the vehicle running while using the winch so as to keep the vehicle charging unit charging so as to help keep the battery up.
> 
> I am puzzled by the statement that your unit would "automatically disconnect from the truck when winch is enabled."  I would think that staying connected and running during use would be a good thing.  Am I missing something?  (probably)


The wire running to the 7-pin connector on the back of most trucks today is not sufficient for running the winch, and you could quite easily cause damage if winching while connected.  For this reason, it's best to buy or build a battery isolator, for this purpose.  When that winch is running, it can pull 340 amps, and the vehicle wiring is likely rated 20 - 30 amps.



salecker said:


> You can get a battery idolator that will charge you winch battery or your truck battery.It will charge whichever one needs it the most.With a little wiring you can have it charge whenever you are hooked up to your trailer.


I haven't found one that does what I'm looking for, which is basically to charge when the vehicle is powered, and isolate (enabling the winch) when the truck is not powered.  By "powered", I mean that the 12V pin in my OEM connector is only live when the ignition is on, and that's when I want to disable the winch.  Can you point me toward one that works like this?  I was going to build my own (one NC relay, one solenoid), but would much prefer just buying something ready-made.


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## WoodyIsGoody (Sep 14, 2017)

Ashful said:


> Good info.  To be clear, is this something you just believe to be true, or do you have a reference for it?  I run on hard data.



It's backed up by hard data. That's why they make two different kinds. I'm sure you can find the data if you're interested in it. It's well known that starting batteries are not well suited to repeated deep discharge.


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## lsucet (Sep 14, 2017)

You should look into the chargers that they put now a day on dump trailers. Use a deep cycle battery and connect it to the charger. When connect it to the truck the 12 volts from the truck goes to the charger and the charger charge the deep cycle battery. Those chargers can also be connect it to 120 ACV to charge the battery. You just need an extension cord.


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## Ashful (Sep 14, 2017)

WoodyIsGoody said:


> It's backed up by hard data. That's why they make two different kinds. I'm sure you can find the data if you're interested in it. It's well known that starting batteries are not well suited to repeated deep discharge.


Of course.  But it's also well known that deep discharge batteries don't like supporting high current loads for several minutes at a time.  So, for a winching application, which is really worse?

I suspect the deep discharge is the way to go, but it's not what winch manufacturers typically recommend, so one has to ask why.


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## Ashful (Sep 14, 2017)

lsucet said:


> You should look into the chargers that they put now a day on dump trailers. Use a deep cycle battery and connect it to the charger. When connect it to the truck the 12 volts from the truck goes to the charger and the charger charge the deep cycle battery. Those chargers can also be connect it to 120 ACV to charge the battery. You just need an extension cord.


Yeah, this seems to be the way to go!  Looking at this system:  http://purkeys.net/boss-dump-trailer-charging-system/


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## lsucet (Sep 15, 2017)

Ashful said:


> Yeah, this seems to be the way to go!  Looking at this system:  http://purkeys.net/boss-dump-trailer-charging-system/


That is great. I have the system on my dump trailer it came with it. They are real small and compact. I am planning in the future, install a winch in front of my flat bed trailer and I will put the system in the toolbox. I just need to splice the 12 volts coming from the truck.


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## lsucet (Sep 15, 2017)

I will also recommend to get one that can be connect it to 120 AC. Mine still small and compact, it has a converter built-in. That way you have ac/dc alternatives.


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## WoodyIsGoody (Sep 15, 2017)

Ashful said:


> Of course.  But it's also well known that deep discharge batteries don't like supporting high current loads for several minutes at a time.  So, for a winching application, which is really worse?
> 
> I suspect the deep discharge is the way to go, but it's not what winch manufacturers typically recommend, so one has to ask why.



Deep discharge batteries can support high current loads when they are sized appropriately for the load. The best solution depends upon the usage profile. If you go big enough with deep discharge batteries you won't have to worry about stressing them with high current and if you go big enough with starting batteries you will not be cycling them as deeply. I'm not sure if anyone makes something in between a deep cycle and a starting battery in lead acid. Have you explored lithium ion? They are good at both deep discharge and high currents (and will be a fraction of the weight).


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## Ashful (Sep 15, 2017)

WoodyIsGoody said:


> Deep discharge batteries can support high current loads when they are sized appropriately for the load. The best solution depends upon the usage profile. If you go big enough with deep discharge batteries you won't have to worry about stressing them with high current and if you go big enough with starting batteries you will not be cycling them as deeply. I'm not sure if anyone makes something in between a deep cycle and a starting battery in lead acid. Have you explored lithium ion? They are good at both deep discharge and high currents (and will be a fraction of the weight).


The deep discharge I listed above is rated 675 CA, and I'm only drawing 40 - 340 A, depending on the load I'm pulling.  So, it's rated for it, but it's not clear (to me anyway) how that load profile will affect lifetime or reliability.  Probably fine, I'd guess.

I'm sure lithium ion would open up better possibilities, but we can't neglect cost.  I'm looking at batteries that cost $100, and I suspect a lithium ion of similar current ratings would cost many times that.


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## mustash29 (Sep 16, 2017)

I am sorry to say, but if you plan to routinely work the winch that hard, you will quickly kill typical group 31 batteries, especially if you are not "trickle" charging them constantly from the truck.  Winching a rolling car onto a trailer is a lot easier than dragging big logs.

You need to spend $$$ on a good large battery like semi's, front end loaders, etc use.  You also need to keep the truck running and charging it.  If your stock "trailer pin" is only capable of charging at 20 - 30 amps, then you need to install a current limiting device so as to not overload the trucks electrical system.  The next step is to run a dedicated charging cable in the realm of 4 ga, 2 ga or bigger with "Anderson" style disconnect plugs rated for up to 350 amps.  These are plugs similar to what is used on snow plows, electric forklifts, pallet stackers, etc.  Then follow up with an upgraded alternator or dual alternators.

A better option would have been a gas motor, hydraulic pump and a hydraulic winch all mounted on the trailer tongue.

Several times I got tri-axel log truck loads delivered.  20' x 20" diameter oak.  My process was to winch about 5 sticks off the top of the pile so almost 10 feet was hanging out in the breeze, then cut rounds, then split & stack nearby, repeat as necessary.  I was using the Warn M-8000 on my S-10 ZR2.  The stock 100 amp alternator was a piece of crap.  When worked hard it would heat up and the output would drop off.  It also only charged at about 40 amps at idle.  When running this combo (stock alt, stock batt, winch) I could tell the system voltage was dropping off as the winch loaded up, and as the voltage drops current increases.  This is how you overheat everything.  Intermittent winching like this would kill the battery after about 30 minutes.  Hooking up the 10 amp home charger helped somewhat.  Keeping the truck running also helped, but it was hard on the rest of the electrical system.  Keep in mind I was working the winch hard enough that I had to have the back of the truck strapped to a yard tree. 

I upgraded to the largest Duralast Gold battery Auto zone sells that will fit in the stock battery tray.  I upgraded to the AD-244 alternator.  It is spec for a Tahoe / Silverado with the HD factory electrical system.  It puts out 100 amps at idle and maxes out at 145 amps.  It also has a larger cooling fan so it runs cooler.  My duramax has the AD-244 stock.  If you want heavy duty charging you can go with dual 100's or dual 145's.

I have an 06 Wrangler Unlimited that weighs roughly 4000.  I has a Smittybilt 8000 on it.  When I want to re-spool the cable on the drum properly I just winch the Jeep up the 10% grade in my driveway.  Even with the Jeep idling, current draw is enough to stress out the stock electrical system, drag down the engine rpm's slightly and make the dash idiot lights go crazy.

I have 2 batteries in my garage that will eventually become the power supplies for a UPS based boiler overheat protection project.  They are "discarded" batteries from my work that were used to start a 250 hp  emergency diesel fire pump.  They were out of date and no longer certified as "reliable" and had to be replaced.  They are 3x the size of a normal car battery, 1150 CCA, 225 AH reserve @ 20 hrs.


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## Ashful (Sep 16, 2017)

Good info, mustash29, thank you.  But aren't group 31 batteries larger than your stock S10 battery tray, especially when I have room for TWO of them?

I checked the +12v pin on my truck's 7-pin connector today, and it's always hot.  So, it will be charging all the time, if I use the dump trailer battery rigs.  Not ideal, for avoiding a dead truck battery, but maybe I can figure a way around that.

The two dump trailer battery charger/isolators I've looked at so far both seem to run around 10 amps.  If the winch is averaging 100 amps in the pull, and run at 50% duty, that's still a drain rate 5x higher than the isolator charge rate.  But, I only need it to last long enough to load my small trailer, then it will have the entire trip home and back to recharge.


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## greg13 (Sep 16, 2017)

An easier way to reduce the amperage needed would be to use a snatch block and reduce the load pull by 50%.


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## Ashful (Sep 17, 2017)

greg13 said:


> An easier way to reduce the amperage needed would be to use a snatch block and reduce the load pull by 50%.


You are correct... but this uses more energy, overall.  The snatch block isn't without some associated loss, but even if we consider it perfectly lossless, you'd only cut the current by half the difference between full-load and no-load current.  This is because winch draw is fairly linear versus load, between the no-load and full-load current points.

So, if I had a 4000 lb pull, it would average 197 amps without the snatch bock.  With the block, it would average over 120 amps for more than twice as long.  Unless I have a very fast charger, where it might keep up at this lower rate, I think it's overall worse for my battery situation.


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## coaly (Sep 17, 2017)

Ashful said:


> Good info, mustash29, thank you.  But aren't group 31 batteries larger than your stock S10 battery tray, especially when I have room for TWO of them?
> 
> I checked the +12v pin on my truck's 7-pin connector today, and it's always hot.  So, it will be charging all the time, if I use the dump trailer battery rigs.  Not ideal, for avoiding a dead truck battery, but maybe I can figure a way around that.



You need a Battery Isolator for charging. Mounts in engine compartment with one terminal to alternator and one to each battery. Each battery gets the proper charge rate keeping them separated.


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## Ashful (Sep 17, 2017)

Yeah, that would be ideal.  But in this case the battery and all circuitry must be on trailer, and I don't want to modify the wiring of every truck I might ever use to pull this trailer.   That's why the dump trailer rig seems ideal, for this requirement.


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## jetsam (Sep 17, 2017)

Ashful said:


> Yeah, that would be ideal.  But in this case the battery and all circuitry must be on trailer, and I don't want to modify the wiring of every truck I might ever use to pull this trailer.   That's why the dump trailer rig seems ideal, for this requirement.



Put a small charge controller next to the battery. They're small, cheap, and they are always come with flat surface mounts.  It'll pay for itself many times over in extended battery life.


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## Ashful (Sep 17, 2017)

jetsam said:


> Put a small charge controller next to the battery. They're small, cheap, and they are always come with flat surface mounts.  It'll pay for itself many times over in extended battery life.



You mean, like a battery Tender?   This trailer is normally stored several hundred feet from the closest electrical outlet.   I'll have to settle for either letting it charge from the truck on my way to the job site, or hauling it over to my barn to charge the evening before use.


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## WoodyIsGoody (Sep 17, 2017)

Ashful said:


> Yeah, that would be ideal.  But in this case the battery and all circuitry must be on trailer, and I don't want to modify the wiring of every truck I might ever use to pull this trailer.   That's why the dump trailer rig seems ideal, for this requirement.



I know you want a bad ass winch trailer. Here's what you do. Find an mount a used Powerwall 1 on that b-itch. Now you're styling. It has enough capacity to winch to your hearts content. might as well go whole hog and find some solar cells, probably wouldn't take many panels to keep it charged up in the down time. Don't worry about money, you're not gonna starve. You just want a bad ass winch trailer.


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## jetsam (Sep 17, 2017)

No, a 12v charge controller. Commonly used by people with solar/wind/hydro power to keep their batteries from cooking. They get very fancy, but you can also go simple.
http:// https://www.amazon.com/dp/B007VLMRP2/
https://www.amazon.com/dp/B007VLMRP2/

That's a fairly random sample; not endorsing that particular one.


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## coaly (Sep 17, 2017)

Ashful said:


> Yeah, that would be ideal.  But in this case the battery and all circuitry must be on trailer, and I don't want to modify the wiring of every truck I might ever use to pull this trailer.   That's why the dump trailer rig seems ideal, for this requirement.



If you're going to use the tow vehicle charging system to charge the trailer battery, the alternator output must be connected to an Isolator to prevent the two batteries from being connected together. You can ONLY connect two batteries in Parallel that are the same size and age. The old way years ago was to connect both batteries to a solenoid that connected them together when the ignition was on. This allowed the charging system to charge both, and not have them connected together to allow them to stabilize each other or discharge the starting battery. You can't put the isolating system on the trailer since the 12 volt power wire in your Bargman 7 way connector is controlled by the voltage regulator when running and can't charge each battery as it needs. This can only be accomplished with an Isolator on the tow vehicle.

Another trick for longer deep cycle battery life is using a 20 amp auto reset circuit breaker on the charge line. When the battery is depleted, your voltage regulator and alternator will try to fast charge the battery at a very fast rate. The breaker will trip and take time to cool down allowing the battery to slowly come up until the charge rate is lower preventing boiling and battery overheating.

You absolutely need a battery isolator on every tow vehicle that is going to connect to multiple batteries. (truck campers, motorhomes and boats use the same system with multiple batteries - they will also add a momentary solenoid to connect them both for starting)
2 - 6 volt batteries in Series gives you much more time duration. Keep them close to the load with extremely large conductors.


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## Montanalocal (Sep 17, 2017)

One other way to go might be to think about mounting a gas powered generator on your trailer that could directly power your winch.  This has 4000 surge watts and a 12 volt outlet.  They also make integrated gas powered winch units.  More $, but no worry about running out of power with a generator.

http://www.northerntool.com/shop/tools/product_200664807_200664807


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## jetsam (Sep 17, 2017)

Montanalocal said:


> One other way to go might be to think about mounting a gas powered generator on your trailer that could directly power your winch.  This has 4000 surge watts and a 12 volt outlet.  They also make integrated gas powered winch units.  More $, but no worry about running out of power with a generator.
> 
> http://www.northerntool.com/shop/tools/product_200664807_200664807



On one hand that sounds excessive; on the other hand you could put a MUCH bigger winch on and get that stuff winched up there in a hurry. 

I stumbled over a really neat winch aid yesterday- just a hinged A-frame on the back of the trailer. Back up to log, flip the A-frame down behind the trailer, lash the log to the peak of the A-frame, winch thr A-frame back onto thr trailer. As it lifts, so does the log, and the winch just has to pull straight towards the front.
http://bit.ly/2y8tql5
http://bit.ly/2y8tql5


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## Ashful (Sep 17, 2017)

coaly said:


> If you're going to use the tow vehicle charging system to charge the trailer battery, the alternator output must be connected to an Isolator to prevent the two batteries from being connected together.


Coaly, you're thinking old-school.  Have you checked out the dump trailer battery chargers?  They replace the need for the classic battery isolator.

http://purkeys.net/boss-dump-trailer-charging-system/#FAQS



Montanalocal said:


> One other way to go might be to think about mounting a gas powered generator on your trailer that could directly power your winch.  This has 4000 surge watts and a 12 volt outlet.  They also make integrated gas powered winch units.  More $, but no worry about running out of power with a generator.
> 
> http://www.northerntool.com/shop/tools/product_200664807_200664807



Considered that, and I already have the generator, but it would take up space and capacity on the trailer, and it would have to go in the cargo area where it's likely to get a little beat up (and maybe be hard to reach when loaded).



jetsam said:


> I stumbled over a really neat winch aid yesterday- just a hinged A-frame on the back of the trailer. Back up to log, flip the A-frame down behind the trailer, lash the log to the peak of the A-frame, winch thr A-frame back onto thr trailer. As it lifts, so does the log, and the winch just has to pull straight towards the front.
> http://bit.ly/2y8tql5


Been looking at those for a while.  Might end up going that way, long-term, but going to just try rolling with the winch mounted up high to start.


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## Jags (Sep 18, 2017)

I know you mentioned one battery vs two, but if the idea is to be kind to the batteries a dual setup is the way to go.  No matter what you do for charge and discharge you are only beating them half as much.


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## Ashful (Sep 26, 2017)

coaly said:


> You absolutely need a battery isolator on every tow vehicle that is going to connect to multiple batteries. (truck campers, motorhomes and boats use the same system with multiple batteries - they will also add a momentary solenoid to connect them both for starting)
> 2 - 6 volt batteries in Series gives you much more time duration. Keep them close to the load with extremely large conductors.


I've been looking into this some more, and really can't find anything to support either of these claims.  There are too many reference to load-balanced parallel 12V setups than I can count, without any mention of issues, provided the batteries are identical manufacture and age.  I'll be purchasing two identical batteries on the same date, so that issue is solved.  Again, I'm talking about two batteries on the trailer, not referencing the separate battery on the truck, which will be isolated by the dump trailer charging system.  These dump trailer charging systems are designed specifically for this situation, isolating the trailer from the truck battery.

The second point, two 6-volt batteries vs. parallel 12-volt batteries, is very hotly debated.  There is no consensus here, other than the fact that series 6-volt batteries tend to be a little less costly than the same capacity in 12-volt cases at lower ampacities, and they may have better lifetime (although this is also contested).  In my case, the trailer platform is designed to hold two group-31 batteries, and I need 340 amps draw.  My little bit of shopping seems to indicate that would be more than 4x the cost to do in 6-volt cases, versus 12-volt cases.  Doesn't seem like the way to go, but maybe there's something I'm missing here.

I can buy two 105 Ah (20-hour rating) 12-volt deep cycles with 182 minute reserve ratings for $99/ea.  They're rated 675 amps each, which is complete overkill (1300 cranking amps in parallel), but there's nothing wrong with that.  Can you beat $198 total cost for 210 amp hours in series 6-volt configuration, for a load of up to 340 amps?  If so, I'd be interested, but I'm not finding it.


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## coaly (Sep 26, 2017)

I'm referring to multiple batteries as in 1 in the tow vehicle and connecting another for "house" use such as used in a motor home, truck camper, or battery on the trailer. When you plug in with engine off, the vehicle starting battery is connected to the trailer battery through the charge plug. Unless you have a heavy duty diode in the charge line, the two batteries equalize almost immediately. Connecting the alternator output to the isolator, the starting battery to Batt #1 and the charge plug to Batt #2 prevents using the tow vehicle battery through the plug and charges each battery as needed.

Winnebago always used two 6 volt batteries in series and other high end coaches did as well. (for the house battery) This was also low amperage use such as lights, gas furnace blower motor, LP fridge using 12 volt control voltage and water pump over long time duration. It was probably better for low amp draw. All the electric golf carts used a series of 6 volt batteries at the time too. (80's) Perhaps deep cycle battery manufacturing has improved as well.
In the marine industry you'll find isolators for 2 alternator inputs to charge a battery bank of 4. The system prevents batteries from drawing on each other and in a pinch it is easy to change an alternator output to the other side if you should loose one in a dual engine boat at sea.
I retired from the RV industry in 2008 and wired many in the 25 years I was in business. May be new technology in use now, but the basics never change.
Horse trailers were notorious for killing the tow vehicle battery since the trailer battery for brakes was usually old and dead, it would be plugged into the tow vehicle and an hour later when the horses were loaded and ready to go the truck groaned over. Horse owners also had the cheapest ,worst towing equipment yet put their most prized possessions in them. Go figure. I hope that has changed.

Without isolating the batteries, (tow vehicle and trailer) the voltage regulator can't supply each battery with the charge it needs when started.

I learned this stuff before the internet by going to RV factory training such as Coachmen and Jayco where we had factory reps from the equipment suppliers they used hold classes. It would be a 2 or 3 day course where a rep from Shur-flo pumps, Tekonsha brake controls, Dometic fridges, Suburban furnace, Atwood water heater and converter / charging system rep would take over the class. Years ago the guys I worked with at a dealership asked me if I would move to Florida for their new adventure certifying RV techs. They started the first RV tech school, and when I said you mean I have to be certified for my own business now, they said NO ! We want you to teach ! I retired from both the Propane and RV business at the same time.
I did end up specializing in power convertor internal repair and repair of charge boards in them when dealers didn't want to replace an entire convertor that needed internal work.


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## Ashful (Sep 27, 2017)

Thanks, coaly.  I agree the series 6V config is better in theory, but at these high capacity (200Ah) and draw rates (340 amps), it seems the much more expensive route.  Massive parallelization (such as two 12V batteries with 600 - 700 amp capacities) does make me at least a little nervous, remembering the way our old diesel car used to occasionally explode one of its paralleled batteries.  It had the momentary solenoid tie you mentioned in an earlier post.  With two permanently paralleled, I'm thinking the chances of surprise explosions should be reduced, but I haven't found much discussion on that subject.

I haven't bought the batteries yet (will probably make it to the store on Friday evening), so if anyone can point me toward a 200+ Ah and > 340A solution in 6V series near that $200 price point, I'd definitely go that route.  I'm just not finding it, myself.

There is still some chance I could kill my truck battery overnight, if I leave the trailer plugged in, since the +12V pin on my 7-pin connector is direct battery hot.  The battery charger mounted to the trailer self-limits at 10 amps, which won't kill my truck in an hour, but could drag it down over the course of 8+ hours.  I could put a relay on the wiring to the battery charger, which will only connect it to the +12V line when I turn on the running lights (I almost always turn on my running lights when towing), but I'm debating if it's worth it.  As you already mentioned, my break-away battery is a bigger risk to the truck battery.

Another addition I'm debating is a cheap solar RV charging rig.  They sell some at Tractor Supply as low as $25, right next to the batteries.  If that's just hanging on those batteries all day every day, chance are they'll be at or near full charge, any time I hook up my truck to roll.  I only use this trailer maybe 3x - 5x per year, most of the time it's just sitting.


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## jetsam (Sep 27, 2017)

Ashful said:


> Thanks, coaly.  I agree the series 6V config is better in theory, but at these high capacity (200Ah) and draw rates (340 amps), it seems the much more expensive route.  Massive parallelization (such as two 12V batteries with 600 - 700 amp capacities) does make me at least a little nervous, remembering the way our old diesel car used to occasionally explode one of its paralleled batteries.  It had the momentary solenoid tie you mentioned in an earlier post.  With two permanently paralleled, I'm thinking the chances of surprise explosions should be reduced, but I haven't found much discussion on that subject.
> 
> I haven't bought the batteries yet (will probably make it to the store on Friday evening), so if anyone can point me toward a 200+ Ah and > 340A solution in 6V series near that $200 price point, I'd definitely go that route.  I'm just not finding it, myself.
> 
> ...



I find that a 2w panel that gets 3-4 hours of sun a day is enough to maintain charge, but I wouldn't expect it to charge them back up from a winching job.

If you get a panel bigger that puts out more juice than the batteries' natural discharge rate, put a charge controller on it.


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## Ashful (Sep 27, 2017)

jetsam said:


> I find that a 2w panel that gets 3-4 hours of sun a day is enough to maintain charge, but I wouldn't expect it to charge them back up from a winching job.
> 
> If you get a panel bigger that puts out more juice than the batteries' natural discharge rate, put a charge controller on it.


Yeah, 2W is exactly what I was looking at, but do you think it will be sufficient to maintain a bank of two big batteries in parallel?  That would be 83 mA per battery, in maximum sunny conditions, and I usually park the trailer in the shade.

https://www.tractorsupply.com/tsc/product/coleman-2-watt-12v-solar-battery-maintainer?cm_vc=-10005

There are 5 watt panels with controllers, from companies like BatteryTender, but they're larger and more expensive.  I had a plan to make up a stainless sheetmetal "hood" to keep weather off the winch, and mount this atop that, and the 5W panels may not fit there.

The BOSS dump trailer charging rig will be charging them back up between winching jobs.  The panel will just be to maintain while parked.


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## jetsam (Sep 27, 2017)

2w for a few hours a day keeps a big AGM battery above 12v for months. 

I don't know what the difference in self-discharge rate is between AGM and regular lead-acid, so I am not sure if you need more or less maintenance charge.  The safe answer is to get a bigger panel and a charge controller- but since your batteries are getting topped up every time you hook up the trailer, it's likely that you don't need to care. Put the 2w panel on and forget it.  Most of those things are "Indoor Only", so take it apart and put some clear silicone everywhere water could get in the plastic shell.


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## Ashful (Sep 27, 2017)

Bizarre that a solar panel ("solar" meaning "sun") would be rated indoor only!

Reading up on this some more, maybe it's worth the money to get a 3-step controller.  If I go that route, the BatteryTender rig is probably the cheapest:

https://www.batterystuff.com/solar-chargers/5-10-watts/12-volt-solar-panels/021-1163.html


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## jetsam (Sep 27, 2017)

Ashful said:


> Bizarre that a solar panel ("solar" meaning "sun") would be rated indoor only!
> 
> Reading up on this some more, maybe it's worth the money to get a 3-step controller.  If I go that route, the BatteryTender rig is probably the cheapest:
> 
> https://www.batterystuff.com/solar-chargers/5-10-watts/12-volt-solar-panels/021-1163.html




I think the intention with those $10 2 watt panels is that you are going to throw it on your dashboard in the car and plug it into your cigarette lighter.


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