Adding a Second Battery

[Jzack605]

Hey all,
First night using the heater in my Hawk and I think the power got low. It only dropped below 12 very momentarily but it seems the low power may be the reason my heat kept shutting off in the night. I can’t do the lithium battery swap right now but I think I can pull a second AGM. I’m not very electrically savvy so would like some guidance on the best way to add the second battery for better power capacity.

 

[Wandering Sagebrush]

If your current battery is aged, I recommend you replace it at the same time you add a second. Best practice is to use the same age, size and brand. Twelve volt batteries need to be connected in parallel. That means the positive terminals are connected together, and the negative terminals are connected together. The preferred way to connect the camper wiring is for the camper positive wire going to the positive terminal of one battery, and camper negative going to the negative terminal of the other battery.

 

[Jzack605]

Seems simple enough. The battery is new, the camper is only a few months old and battery hasn’t been used a ton. I’m just looking to extend usage time and not be left with no power in the boondocks. Can I get away with a different brand with same specs?

 

[Wandering Sagebrush]

Seems simple enough. The battery is new, the camper is only a few months old and battery hasn’t been used a ton. I’m just looking to extend usage time and not be left with no power in the boondocks. Can I get away with a different brand with same specs?

I suspect you can, but best practice is to have a matching pair.

How are you charging your batteries, any other load on the system (refrigerator)?

 

[Vic Harder]

Don’t underestimate the value of adding a real tool for monitoring your battery’s SOC (state of charge). A volt meter often won’t cut it. The Victron Smart Shunt is a good way to go.

A different cause for this issue could be the heater itself. Have you seen the threads on removing the duct work?

 

[Jzack605]

I suspect you can, but best practice is to have a matching pair.

How are you charging your batteries, any other load on the system (refrigerator)?

Just with the alternator when truck is on.

 

[Jzack605]

Don’t underestimate the value of adding a real tool for monitoring your battery’s SOC (state of charge). A volt meter often won’t cut it. The Victron Smart Shunt is a good way to go.

A different cause for this issue could be the heater itself. Have you seen the threads on removing the duct work?

Someone on a Facebook group mentioned the duct work as well. I removed the small bit of duct by the vent. I have not seen the threads though, I’ll try to find them.

 

[Vic Harder]

Just with the alternator when truck is on.

Oh. That "might" be an issue, especially with newer trucks and their "smart" alternators. Get the shunt based SOC meter first, then you can see just how (in)effective your charging is right now. It can be fixed, but let's be sure about the cause of the problem first.

 

[Wandering Sagebrush]

What Vic said…

 

[Jzack605]

Oh. That "might" be an issue, especially with newer trucks and their "smart" alternators. Get the shunt based SOC meter first, then you can see just how (in)effective your charging is right now. It can be fixed, but let's be sure about the cause of the problem first.

So the display on the deep sea is not a reliable way to determine battery level?

 

[Vic Harder]

So the display on the deep sea is not a reliable way to determine battery level?

Sorry, "deep sea"?? If you mean voltage, no often isn't

 

[veryactivelife]

Hi, a lot of good advice so far. I’m the guy who suggested low voltage on your Facebook post. That foil duct should be removed regardless of what the current issue is, it creates too much back pressure on the sail switch particularly when at higher elevation. From what you’ve said here it sounds like low voltage was the issue. The furnace blower will go through a lot of amp hours if running all night trying to keep the camper at the temperature you might keep your house at. Add the fridge draw to that and you’d easily blast through the usable amp hours of a single battery.

I agree that installing a shunt based battery monitor is the first upgrade any camper owner should make. Voltage fluctuates too much to be of any real use. It will only give you an accurate reading when the battery has been at rest for a while and that never happens when you are using the camper. The shunt will measure all the ins and outs in terms of amps. So you know exactly how many amps have been used. Victron has 2 that many of us have installed, the BMV712 smart and the Smart shunt. Both have Bluetooth and utilize the Victron app. For a basic setup like a FWC I think the Smart Shunt will do the job.

Lots of people make a single battery work for them but it will take close monitoring and conservation of battery use. As has been mentioned now is the time to add a second battery and it should be an exact match to what you have. It hasn’t been mentioned and perhaps you already know, but only half of the battery amp hours are usable. Otherwise you’ll be replacing batteries every year or so.

Dean

 

[Big Al]

Wouldn't it be better to use two six volt batteries wired in series than to have two twelve volt batteries wired in parallel?

The way it was explained to me was that wiring this way gave, in essence, one large twelve-volt battery, except that, since the six-volt batteries had fewer plates, there was more room for electrolyte and therefore more capacity to produce electricity.

 

[Vic Harder]

Wouldn't it be better to use two six volt batteries wired in series than to have two twelve volt batteries wired in parallel?

The way it was explained to me was that wiring this way gave, in essence, one large twelve-volt battery, except that, since the six-volt batteries had fewer plates, there was more room for electrolyte and therefore more capacity to produce electricity.

Sounds reasonable. However, if you already have one 12V battery, adding another is comparatively cheaper and easier, no?

 

[Jzack605]

Hi, a lot of good advice so far. I’m the guy who suggested low voltage on your Facebook post. That foil duct should be removed regardless of what the current issue is, it creates too much back pressure on the sail switch particularly when at higher elevation. From what you’ve said here it sounds like low voltage was the issue. The furnace blower will go through a lot of amp hours if running all night trying to keep the camper at the temperature you might keep your house at. Add the fridge draw to that and you’d easily blast through the usable amp hours of a single battery.

I agree that installing a shunt based battery monitor is the first upgrade any camper owner should make. Voltage fluctuates too much to be of any real use. It will only give you an accurate reading when the battery has been at rest for a while and that never happens when you are using the camper. The shunt will measure all the ins and outs in terms of amps. So you know exactly how many amps have been used. Victron has 2 that many of us have installed, the BMV712 smart and the Smart shunt. Both have Bluetooth and utilize the Victron app. For a basic setup like a FWC I think the Smart Shunt will do the job.

Lots of people make a single battery work for them but it will take close monitoring and conservation of battery use. As has been mentioned now is the time to add a second battery and it should be an exact match to what you have. It hasn’t been mentioned and perhaps you already know, but only half of the battery amp hours are usable. Otherwise you’ll be replacing batteries every year or so.

Dean

Thanks Dean, I think I’m going to add the shunt and second battery. There is no fridge in my camper so there’s no draw from one.

 

[veryactivelife]

Thanks Dean, I think I’m going to add the shunt and second battery. There is no fridge in my camper so there’s no draw from one.

Good plan, let us know how it works out.

 

[CPT Davenport]

Seems simple enough. The battery is new, the camper is only a few months old and battery hasn’t been used a ton. I’m just looking to extend usage time and not be left with no power in the boondocks. Can I get away with a different brand with same specs?

If the camper is new it should be prewired for solar. Consider adding some solar to the mix. Even a portable panel off the back will help. That panel could also keep your battery topped off while your camper sits in between trips. Letting AGM batteries get below 50% SOC is no bueno. I also agree with adding a shunt. I put it off and tried to think of every way possible to keep track of the SOC based solely on voltage readings with very limited success. The shunt is the way to go and takes all the guess work out of the equation.

 

[Jzack605]

If the camper is new it should be prewired for solar. Consider adding some solar to the mix. Even a portable panel off the back will help. That panel could also keep your battery topped off while your camper sits in between trips. Letting AGM batteries get below 50% SOC is no bueno. I also agree with adding a shunt. I put it off and tried to think of every way possible to keep track of the SOC based solely on voltage readings with very limited success. The shunt is the way to go and takes all the guess work out of the equation.

Yeah solar is definitely in the plan. I guess my only issue with solar that isn’t mounted permanently is the truck is still a daily driver and a lot of daylight hours will be spent with it driving. So to really get the value of solar id have to mount it permanently.

 

[Jzack605]

I added a second battery that was as close to identical as the og 24 AGM as I could find in parallel. Turned everything on and didn’t blow myself up (I’m scared of electricity) which was great. I’ve been watching the voltage meter the past 10min. Started at 12.88 and has trickled down to 12.84 very slowly. I may be a bit paranoid, but is this normal?

 

[Jzack605]

Now it’s reading at 14.46v!