On board this and that... What about a battery charger

[Danny G]

Anyone done an onboard battery charger? We talked about an aux battery a while back. I plan on doing an on board inverter and have been pondering the merrits of an onboard charger for some time.

Not like a 5 amp tender, but a legit charger ranging between 25-100 amps, like on an RV effectively giving you "shore" power. They make outdoor/onboard units that are relatively small you could slap onto a fender wall, they can also be used to jump a vehicle. Larger units (30+amps) you may want to get creative and mount in a battery box. One of the great things about a bullnose especially the 300-6 is a lot of room under the hood.

This works well for those of us that like to truck camp, for recreation or even travel. Pull up plug it in. Power pole > battery charger > Main and aux battery > trucke stereo etc or > power inverter> accessories/lights/heaters etc.

[Gary Lewis]

If you do add a charger then don't implement a Cole-Hersee smart battery isolator in its normal wiring plan. Because if you do you'll raise the battery voltage to 13.2 volts and the CH isolator will parallel the batteries. Been there, done that.

The solution is to run the ground for the CH isolator through a relay that is triggered by the ignition switch. That way the isolator won't come in unless the vehicle is running.

[ArdWrknTrk]

.... Pull up plug it in. Power pole > battery charger > Main and aux battery > trucke stereo etc or > power inverter> accessories/lights/heaters etc.

Why would you use a transformer to get to 12V and then step it up with an inverter to get 120AC???

or maybe I'm reading this wrong?

At that point I'd just get a whisper quiet Honda or Onan generator and be done with it.

[Danny G]

.... Pull up plug it in. Power pole > battery charger > Main and aux battery > trucke stereo etc or > power inverter> accessories/lights/heaters etc.

Why would you use a transformer to get to 12V and then step it up with an inverter to get 120AC???

or maybe I'm reading this wrong?

At that point I'd just get a whisper quiet Honda or Onan generator and be done with it.

I think my late night brain did not communicate this properly to begin with, because the generator at that point wouldn't make much sense either if you were at a KOA with a power pole lol. In either case just grab a 30amp to standard plug rv adapter and call it a day.

There are two instances I have seen this done and the reason is simply because the need is built into the vehicle. One gentleman had a pick up he used for over landing/camping, with accessory/outlets built into the bed. He then had a canvas tent that affixed to the bed. If over landing he could run power in his "tent" off of battery/engine power. If at a KOA he could plug his truck in, run his stero system, on board CB etc while keeping the batteries fresh and then also running other accessories in the back(heater, truck fridge etc). It was a "newer" truck so he had everything built into a tool box in the bed. The second time I have seen this was in a cargo van -> camper conversion. In an RV the power I believe comes into a PDC from either a generator or shore power and then splits powering the RV and charging the batteries, seems that would take up a lot more real estate.

While not quite similar, when I was in Texas I purchased a old field found Willy's MB for $500 to do something similar. I had a friend group that ran old CJ jeeps with small diesel conversions (like the VW 1.6). They had on board inverters and either tiny trailers or hitch mounted carriers for gear. They would go out (sometimes for multi-day hog hunts), set up a wall tent and idle those tiny diesels to generate power for lights and a little window AC unit, charge radios and cell phones. A 5.5k Onan might have been more efficient but space was a premium especially if you were hauling a canvas tent and little AC unit to combat Texas heat. For fuel sharing they would have needed a more expensive diesel version too adding several thousand bucks vs idling a 1.6l diesel sipping fuel and running an $500 inverter. That build never happened, ended up emptying my storage unit with the parts and jeep selling it off so I could move from San Antonio to Charleston for work.

[kramttocs]

If you do add a charger then don't implement a Cole-Hersee smart battery isolator in its normal wiring plan. Because if you do you'll raise the battery voltage to 13.2 volts and the CH isolator will parallel the batteries. Been there, done that.

Can you explain why this is a problem if the charger is big enough to overcome the isolator draw? As you know, I'll have this situation and also want to use an onboard maintainer.

[Gary Lewis]

Can you explain why this is a problem if the charger is big enough to overcome the isolator draw? As you know, I'll have this situation and also want to use an onboard maintainer.

Good question. If the charger can overcome the draw of the pull-in current of the isolator then there's no harm no foul. In my case the little HF charger couldn't and the relay would pull in and the voltage would head south. Then the relay would drop out and the cycle would start again.

But in this case the charger is going to be adequate to not only overcome the current of the relay/isolator but also that of the inverter, so there's no problem at all. I wasn't thinking.

In your case, check the capability of the charger you are going to use. But also note that the relay will parallel the batteries so the charger will see both of them instead of just one.

[kramttocs]

Can you explain why this is a problem if the charger is big enough to overcome the isolator draw? As you know, I'll have this situation and also want to use an onboard maintainer.

Good question. If the charger can overcome the draw of the pull-in current of the isolator then there's no harm no foul. In my case the little HF charger couldn't and the relay would pull in and the voltage would head south. Then the relay would drop out and the cycle would start again.

But in this case the charger is going to be adequate to not only overcome the current of the relay/isolator but also that of the inverter, so there's no problem at all. I wasn't thinking.

In your case, check the capability of the charger you are going to use. But also note that the relay will parallel the batteries so the charger will see both of them instead of just one.

It's definitely something to be considered when using dual batteries and a smart isolator so I am glad you brought it up.

Amps aside, I looked at tech sheets for three chargers and they had min values of:

#1. 13.4

#2. 12.6

#3. 12.7

Isolator joins at 13.2

Which would be better?

1:

Would keep the batteries constantly connected and thus both charged

Would also keep the solenoid engaged continuously

More prone to short cycling as the solenoid would be a parasitic draw?

2/3:

Would primarily be floating the main battery.

Only triggering the solenoid and charging the secondary battery if the main battery needs topped off as that would go over 13.2.

Chance of the aux battery draining and not being charged

Correct me if my logic isn't right on this.

[Danny G]

It's definitely something to be considered when using dual batteries and a smart isolator so I am glad you brought it up.

Amps aside, I looked at tech sheets for three chargers and they had min values of:

#1. 13.4

#2. 12.6

#3. 12.7

Isolator joins at 13.2

Which would be better?

1:

Would keep the batteries constantly connected and thus both charged

Would also keep the solenoid engaged continuously

More prone to short cycling as the solenoid would be a parasitic draw?

2/3:

Would primarily be floating the main battery.

Only triggering the solenoid and charging the secondary battery if the main battery needs topped off as that would go over 13.2.

Chance of the aux battery draining and not being charged

Correct me if my logic isn't right on this.

This is really easy depending on what you want to do with your tender. 1) To keep both batteries topped off (tended) or topped during low power continuous use. or 2) Plug the truck in to keep the batteries charged while you are running equipment say like a big freaking stereo system for and extended time or other truck equipment.

For item 1 its simple. Get a two bank onboard charger and leave your set up as you planned it. The on board tender connects to each battery separately but only charges typically with 8-12 amps.

For item 2, if you want to keep it topped off with heavier draw you need something more sufficient that more mirrors your alternator so a on board charger putting out 25-100 amps depending on your use would be required.

My plan has always been to use a good isolator/solenoid/relay pick your choice of nomenclature. That is actuated in start/run to connect the batteries.

I know I posted on another thread about this but my mindset is to keep the main battery isolated for cranking/running the engine so with the key off there is no chance for any parasitic drain etc from any other system. Everything else, lights radio etc to the aux battery. When the key is in run/start the batteries are linked so the aux can also add to cranking if needed, and both batteries then share load when the engine is running and both are being charged by the alternator in this state.

Hooking up a 25-100amp charger to the aux battery in this set up does not do anything but supply power to the truck/accessories and keep the battery charged. If you are just running LED lights, a few small items, charging some tool batteries, 25 amps should be more than sufficient. If camping out in the back with your kid and you add a space heater, radio, laptop for some reason(kids or angry wife has you living in your truck bed), or got silly and wanted to run a winch with the engine off (I know doesn't make sense, just a high load example) you probably want something more sufficient in the 75-100 amp ranges.

A few years ago I converted most of my yard equipment to 80v battery driven units. After Hurricane Matthew hit us I also converted my chainsaw. Post hurricane ethanol free pre mix was hard to get a hold of, mixing gas and oil was an option ethanol makes micro carbs run like poop. I and several others ran into some issues that required some in field tear downs. No one dropped $800 on a really nice Husqvarna mind you. My 80V has never let me down, I actually just felled, limbed, and bucked a maple and a red oak in the back yard last week with ease, and no ear plugs. What I did during the emergency times was run an inverter off my vehicle with two chargers. I have several batteries due to multiple tools. Two batteries on the charger, one in the tool kept my 80v chainsaw running none stop during storm clean up. Only thing I needed to do was lube the bar, make sure the oil was good and sharpen the chain from time to time. Long story short, my truck will have two battery chargers in it as part of its payload and one for my porter cable 20v lithium set.

[Gary Lewis]

It's definitely something to be considered when using dual batteries and a smart isolator so I am glad you brought it up.

Amps aside, I looked at tech sheets for three chargers and they had min values of:

#1. 13.4

#2. 12.6

#3. 12.7

Isolator joins at 13.2

Which would be better?

1:

Would keep the batteries constantly connected and thus both charged

Would also keep the solenoid engaged continuously

More prone to short cycling as the solenoid would be a parasitic draw?

2/3:

Would primarily be floating the main battery.

Only triggering the solenoid and charging the secondary battery if the main battery needs topped off as that would go over 13.2.

Chance of the aux battery draining and not being charged

Correct me if my logic isn't right on this.

Scott - Sorry, I missed this.

On the chargers, most battery maintainers, which I think is what you want, will take a 12v battery to something around 14v to get it fully charged, and then go into "maintenance" mode and keep the batttery at around 13.0v.

Battery Tender has a good, but quite lengthy, discussion of the battery charging "algorithm" on the Battery Charging Algorithm Fundamentals" tab here: http://www.batterytender.com/Battery-Basics.

If you want the battery(s) maintained at full charge w/o boiling them dry I'd recommend that you get something like a Battery Tender, or the HF equivalent, to do the job. If I remember correctly, Battery Tenders come in dual versions so you could have one of those permanently mounted and just plug the truck in when the time comes.

[Gary Lewis]

This is really easy depending on what you want to do with your tender. 1) To keep both batteries topped off (tended) or topped during low power continuous use. or 2) Plug the truck in to keep the batteries charged while you are running equipment say like a big freaking stereo system for and extended time or other truck equipment.

For item 1 its simple. Get a two bank onboard charger and leave your set up as you planned it. The on board tender connects to each battery separately but only charges typically with 8-12 amps.

For item 2, if you want to keep it topped off with heavier draw you need something more sufficient that more mirrors your alternator so a on board charger putting out 25-100 amps depending on your use would be required.

My plan has always been to use a good isolator/solenoid/relay pick your choice of nomenclature. That is actuated in start/run to connect the batteries.

I know I posted on another thread about this but my mindset is to keep the main battery isolated for cranking/running the engine so with the key off there is no chance for any parasitic drain etc from any other system. Everything else, lights radio etc to the aux battery. When the key is in run/start the batteries are linked so the aux can also add to cranking if needed, and both batteries then share load when the engine is running and both are being charged by the alternator in this state.

Hooking up a 25-100amp charger to the aux battery in this set up does not do anything but supply power to the truck/accessories and keep the battery charged. If you are just running LED lights, a few small items, charging some tool batteries, 25 amps should be more than sufficient. If camping out in the back with your kid and you add a space heater, radio, laptop for some reason(kids or angry wife has you living in your truck bed), or got silly and wanted to run a winch with the engine off (I know doesn't make sense, just a high load example) you probably want something more sufficient in the 75-100 amp ranges.

A few years ago I converted most of my yard equipment to 80v battery driven units. After Hurricane Matthew hit us I also converted my chainsaw. Post hurricane ethanol free pre mix was hard to get a hold of, mixing gas and oil was an option ethanol makes micro carbs run like poop. I and several others ran into some issues that required some in field tear downs. No one dropped $800 on a really nice Husqvarna mind you. My 80V has never let me down, I actually just felled, limbed, and bucked a maple and a red oak in the back yard last week with ease, and no ear plugs. What I did during the emergency times was run an inverter off my vehicle with two chargers. I have several batteries due to multiple tools. Two batteries on the charger, one in the tool kept my 80v chainsaw running none stop during storm clean up. Only thing I needed to do was lube the bar, make sure the oil was good and sharpen the chain from time to time. Long story short, my truck will have two battery chargers in it as part of its payload and one for my porter cable 20v lithium set.

TheScatch - While for the most part I agree with what you've said, I do have a concern with this plan: "When the key is in run/start the batteries are linked so the aux can also add to cranking if needed, and both batteries then share load when the engine is running and both are being charged by the alternator in this state."

The way Ford's auxiliary battery setup works, as shown below, is that the aux battery only comes in during Run, not Start. I believe that is so you can run that battery completely down and still start the vehicle. Otherwise the Start battery would be trying to charge the Aux battery at the same time as starting the vehicle.

And this is one reason I like the Cole Hersee Smart Isolator. It won't parallel the batteries automatically until one is up to 13.2v, meaning the vehicle is running. But, there's a manual feature where you can force-parallel the batteries by pushing a button. So if you know the Aux battery is charged and want a boost you can do that.