Need Help, Advice on a Dual Battery system set up.

[KhaymanRanger1997]

Hello all, I’m really want to set up a Dual batter system so that I can run my winch, main light bar, and any small plug in devices off of a deep cycle battery that’s re-charged by my trucks alternator.

When I first hear of this set up it sounded like the best idea! But as I’m figuring more out and learning more, I’m lost and confused.

There are a lot of Isolators with diagrams, and they show two battery’s to the isolator and alternator. But a lot of them also show the Deep Cycle Battery or Aux battery having a solar/separate charger? I thought that’s what the alternator was for! Many of the nice “kits” are made for Jeep’s and Tacoma’s, I’m building this on a 1999 Ranger.

I’d like to keep the Auxiliary battery in my truck bed for easier access. Does anyone know or has seen a great kit? Or maybe a good diagram? Pic’s of your own Aux battery? If it’s be smarter to just buy a 370 Amp Alternator? Lol, I’m hoping to run a 34series Deep Cycle battery. Send me a message if you want, I need help!

 

[Mighty Dodge Ram]

I’ll let the more experienced chime in on the different systems but will add my 2 cents on the winch. IMO you should power your winch off the starting battery. They‘re designed for a higher amperage output and somewhat quicker recharge rate as part of their “starting the car” profile. Of course, the engine will be running (ideally at a higher rpm) while you winch. That’s how my system is set up.

 

[Herbie]

The reason you often see solar or other chargers attached is that Alternator-charging alone is very often not enough to maintain a deeply cycled house battery.

Depending on how often you move the vehicle, and especially depending on whether you drive for long durations after sitting for a while, the time where the alternator is actually feeding in to the house may be insufficient to even do a bulk-charge back to near-full, let alone the longer soak times at lower charge rates that are required by some battery chemistries.

The voltage off the alternator is also not always optimal for recharging these batteries. My East-Penn/Deka AGM, for example, wants to see charge voltages in the 13.8-14.8 range during the bulk stage - but my vehicle alternator normally operates at ~13.6-14.0v (so only sometimes in the right range). This is why you often see DC-DC chargers on some folks diagrams - especially for older vehicles where the nominal alternator voltage might be only 13.2v or 13.4v.

Additionally, the operating mode of sitting for several days (deep discharge), followed by either partial or full recharge, puts the most wear on most battery types. Using solar to keep the state of charge closer to full will extend the number of cycles the battery can give - not to mention extending the amount of time you can be parked someplace.

So, the short version is that while an alternator-coupled dual-battery system is convenient and cheap, it isn't the best way to maintain a potentially expensive house battery. I have a version of these on my van, but it mostly serves other purposes - (1) the ability to self-jump from the house battery to the starter, should this ever be needed, and (2) This lets the solar and shore-power chargers I have for the house battery also charge the starting battery (works in either direction.)

 

[DiploStrat]

There are four issues here:

-- Where do you attach your winch. On this, I pass, as I have no special knowledge.
-- How big is your camper/second/auxiliary/house battery? It should, if at all possible, large enough so that you can never run it down.
-- How do you charge your camper battery? Generically, deep cycle lead acid batteries need high voltage (14v+) for a long time (at least two hours beyond "full" charge, and as many amps as you can muster, ideally at least 20% of the capacity of the bank. E.g. 20A of charger per 100A of battery.
-- Finally, you should isolate the two banks when they are discharging.

Grossly:
-- You must know the output of your alternator especially the voltage. If it is not somewhere on the high side of 14v, you will need to boost it.
-- You must size the wire between the alternator and the camper battery so that it can pass at least 50A with no more than 5% drop.
-- You must charge long enough to complete the absorb stage. This typically requires a shore charger or solar.

Finally, isolation.
-- If your truck charges at a steady 14v+, then a relay (aka solenoid), large enough to pass at least 100A, is probably the way to go. I prefer voltage sensing relays as they are automatic and allow you to charge your starter battery from your shore or solar charger with no extra gear.
-- If your truck does NOT produce a steady 14v+, or if you use one of the deep cycle batteries that needs a charge over about 14.5v, then you are probably in the market for a battery to battery charger. Lots of options from Sterling Power, Renogy, Victron, et al. I personally like the REDARC models, especially for a smaller vehicle as they do not require a fan and are dead easy to install. For a smaller set up, they, like some others, will also double as a solar controller.

All of this covered in painful detail under "Documents" on my website. Hope this is helpful.

Good luck!

 

[KhaymanRanger1997]

The reason you often see solar or other chargers attached is that Alternator-charging alone is very often not enough to maintain a deeply cycled house battery.

Depending on how often you move the vehicle, and especially depending on whether you drive for long durations after sitting for a while, the time where the alternator is actually feeding in to the house may be insufficient to even do a bulk-charge back to near-full, let alone the longer soak times at lower charge rates that are required by some battery chemistries.

The voltage off the alternator is also not always optimal for recharging these batteries. My East-Penn/Deka AGM, for example, wants to see charge voltages in the 13.8-14.8 range during the bulk stage - but my vehicle alternator normally operates at ~13.6-14.0v (so only sometimes in the right range). This is why you often see DC-DC chargers on some folks diagrams - especially for older vehicles where the nominal alternator voltage might be only 13.2v or 13.4v.

Additionally, the operating mode of sitting for several days (deep discharge), followed by either partial or full recharge, puts the most wear on most battery types. Using solar to keep the state of charge closer to full will extend the number of cycles the battery can give - not to mention extending the amount of time you can be parked someplace.

So, the short version is that while an alternator-coupled dual-battery system is convenient and cheap, it isn't the best way to maintain a potentially expensive house battery. I have a version of these on my van, but it mostly serves other purposes - (1) the ability to self-jump from the house battery to the starter, should this ever be needed, and (2) This lets the solar and shore-power chargers I have for the house battery also charge the starting battery (works in either direction.)

That is a lot of helpful info, This is my Daily Driver so I'm running it at least twice a day sometimes more. My alternator (Which I just replaced this weekend is 95Amps) so, In our opinion would that even be enough to keep a 34 Series Deep Cycle charged enough? I've gathered I'm going to install the winch to my main battery, with a separate switch in the cab to turn it on and off. (Try and save battery life) I work at a Farm Store and Most likely I'm going to buy the Exide Nautilus 27MDP, it's a Dual Purpose Deep Cycle AGM Battery 730 MCA, 575 CCA, 88AH at 20 hour rate.

 

[KhaymanRanger1997]

There are four issues here:

-- Where do you attach your winch. On this, I pass, as I have no special knowledge.
-- How big is your camper/second/auxiliary/house battery? It should, if at all possible, large enough so that you can never run it down.
-- How do you charge your camper battery? Generically, deep cycle lead acid batteries need high voltage (14v+) for a long time (at least two hours beyond "full" charge, and as many amps as you can muster, ideally at least 20% of the capacity of the bank. E.g. 20A of charger per 100A of battery.
-- Finally, you should isolate the two banks when they are discharging.

Grossly:
-- You must know the output of your alternator especially the voltage. If it is not somewhere on the high side of 14v, you will need to boost it.
-- You must size the wire between the alternator and the camper battery so that it can pass at least 50A with no more than 5% drop.
-- You must charge long enough to complete the absorb stage. This typically requires a shore charger or solar.

Finally, isolation.
-- If your truck charges at a steady 14v+, then a relay (aka solenoid), large enough to pass at least 100A, is probably the way to go. I prefer voltage sensing relays as they are automatic and allow you to charge your starter battery from your shore or solar charger with no extra gear.
-- If your truck does NOT produce a steady 14v+, or if you use one of the deep cycle batteries that needs a charge over about 14.5v, then you are probably in the market for a battery to battery charger. Lots of options from Sterling Power, Renogy, Victron, et al. I personally like the REDARC models, especially for a smaller vehicle as they do not require a fan and are dead easy to install. For a smaller set up, they, like some others, will also double as a solar controller.

All of this covered in painful detail under "Documents" on my website. Hope this is helpful.

Good luck!

That is a lot of helpful info, This is my Daily Driver so I'm running it at least twice a day sometimes more. My alternator (Which I just replaced this weekend is 95Amps) so, In our opinion would that even be enough to keep a 34 Series Deep Cycle charged enough? I've gathered I'm going to install the winch to my main battery, with a separate switch in the cab to turn it on and off. And realistically this AUX/House battery will be running my 40" Light bar, and phone plug ins. Which isn't going to be often since we only get to do so many trips a year. I work at a Farm Store and Most likely I'm going to buy the Exide Nautilus 27MDP, it's a Dual Purpose Deep Cycle AGM Battery 730 MCA, 575 CCA, 88AH at 20 hour rate.

 

[KhaymanRanger1997]

I’ll let the more experienced chime in on the different systems but will add my 2 cents on the winch. IMO you should power your winch off the starting battery. They‘re designed for a higher amperage output and somewhat quicker recharge rate as part of their “starting the car” profile. Of course, the engine will be running (ideally at a higher rpm) while you winch. That’s how my system is set up.

Do you have a separate switch for your winch? So it isn't always on? I was talking to a few guys who all did that but eventually went to separate switches in he cab to cut the power consumption. ( I've got 4 aux. switches I bought for this.)

 

[OllieChristopher]

It will help to know what year and model is your truck and what winch you plan on getting ? I can tell you that a 95 amp alternator is not going to put out enough amps for heavy winching.

Here is what I did to my 2005 GMC Sierra:

Dual battery install 05 GMC Sierra with pics

Hi guys I'm new here. Thought I would share some pictures and my procedures for a dual battery install. This is model specific but can cross over to many other makes and models. First a little background. I have been a lurker here for many years. I'm getting to a point in my life to do some...

expeditionportal.com

 

[KhaymanRanger1997]

It will help to know what year and model is your truck and what winch you plan on getting ? I can tell you that a 95 amp alternator is not going to put out enough amps for heavy winching.

Here is what I did to my 2005 GMC Sierra:

Dual battery install 05 GMC Sierra with pics

Hi guys I'm new here. Thought I would share some pictures and my procedures for a dual battery install. This is model specific but can cross over to many other makes and models. First a little background. I have been a lurker here for many years. I'm getting to a point in my life to do some...

expeditionportal.com

I’m putting all of this on my 1999 Ford Ranger has the 3.0. And the winch I have is the XBull 13,000lb. Winch. Details below.

 

[DiploStrat]

Dual purpose batteries are NOT deep cycle. You really must know your load.

As a rule of thumb, averaged, with a lot of Kentucky windage, you can probably charge about 25A an hour from your alternator.

Sooooo, 100Ah battery, 50% rule, you need to recharge 50Ah. At 25A per hour, you will need to drive 2-3 hours for the bulk charge + two hours of absorb.

Very, very, very gross estimates.

No one can help you until we know your loads and times.

 

[KhaymanRanger1997]

Bare with me, what I'm gathering is that ultimately I really don't need an Aux/House Battery. I'm running this winch and a single light bar off of my main battery to an auxiliary switch into the cab (to cut the power to access.) I really would just need a beefier Battery and maybe a higher amp alternator?

Because really I'm most likely never going to be running them together, it will be either or. And They won't be running very much in general, I've got a trip that I'm planning now but really the winch and light bar are "Just in Case"

 

[DiploStrat]

Does your truck have a factory tray under the hood for a second battery? You might do worse than to simply buy a matched pair of hybrid/dual purpose batteries and wire them properly in parallel.

Done.

Don't make it harder than it has to be.

 

[KhaymanRanger1997]

Does your truck have a factory tray under the hood for a second battery? You might do worse than to simply buy a matched pair of hybrid/dual purpose batteries and wire them properly in parallel.

Done.

Don't make it harder than it has to be.

I've looked and researched and as far as I know they don't have a second battery tray, best thing I could do is take my Air Filter box out and re-route the air intake.

 

[DiploStrat]

It is less than optimal, and will require a couple of long wires, but if you use properly large wires, and wire "diagonally," that is, positive connected to one battery and negative to the second, you can put the second battery wherever you want.

The essential thing is that both are same make/model/capacity/etc. and that they are as close to sequential production as possible. That basically means buy both at the same time.

So, factory battery positive is unchanged. New cable, at least as large as the factory wire (use welding cable for a thousand reasons) runs to the positive of your second battery.

Negative of your factory battery is disconnected and reconnected with a cable, matched in length/size/type/etc. to the negative of your second battery.

Negative of your second battery is run back to the original ground point of the factory battery.

Actually easier to do than to describe. Read this page, especially "Method 2,' until you understand it. http://www.smartgauge.co.uk/batt_con.html

If you can't crimp big wires, there are companies that will sell them preterminated. Just measure twice and order once.

 

[Mighty Dodge Ram]

I do not have a switch…essentially a power cutoff…for the winch, but I should. This would have to be something that could handle high amps. For me, ideally, that cutoff would be located close to the battery under the hood to prevent mischief. Alternatively, I could re-mount the control box from its current location on top of the winch to under the hood. This should not be confused with an in-cab switch that essentially replaces your corded control that operates the winch.

As you mentioned, if you aren’t powering a bunch of different “camping” accessories you probably don’t need a second battery. Or…consider one of those portable units that claim they can be re-charged through a standard port. Of course, be prepared to dig a bit deeper into your pocket. $$$