# How can I put deep cycle batteries in a semi tractor-trailer?

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1. Dec 27, 2016

### Mike9119

Hello I drive for a truck company and am getting tired of being charged for idling my truck to keep my batteries from depleting. I have a 2000w inverter now that's hooked to the truck. I had the idea of putting a few deep cycle batteries and charging them somehow with truck inverter or outlets while I drive so I don't have to idle. Is this possible? If so what would I need to get? I have never used any kind of setup like this before solar or offers anything tho I have always been interested in it. Thank you.

2. Dec 27, 2016

### anorlunda

Sure, you can do that as long as you have a separate starting battery.

The key thing you need is a charge controller for the deep cycle batteries, preferably a 3-stage charge controller. The controller uses nominally 12 v in and 12 v out. That is commonly used on boats to charge deep cycle batteries from the alternator or from solar/wind sources. A search for alternator charge controller on Google returned numerous results ranging from $79 to$250 in cost.

The cheapest deep cycle batteries are typically 6 volt golf cart batteries. You wire them in series to make a 12 v bank.

Then you need to wire your house loads to draw from the deep cycle batteries, rather than directly from the alternator/starter. If you need help with a wiring diagram, post again.

3. Dec 27, 2016

### Mike9119

Cool seems like i got stuff to reference and research now. What kind of load can I run on that set up? Right now I peak at 1800 watts with a microwave fridge ps3 tv going.

4. Dec 27, 2016

### anorlunda

1800 w ihs a lot on battery load.

http://www.starmarinedepot.com/xant...swNg4yr7hEZ0_2AYqHAfuWmJAVbUhoSpt8aAj8Z8P8HAQ

that is a link for an 1800 w inverter with 88% efficiency.

1800w/0.88 = 2045 w
2045 w/ 12v = 170 amps

As a rule, deep cycle batteries should not be used more than 30% of rated amp-hours. Otherwise, their life is shortened. A 6 v golf cart battery is rated 215 Ah. 215*0.3=65

So, with one bank of 12 v batteries (two 6 v batteries in series), you can run 1800 w for 65/215 hours or about 23 minutes. For an hour, you need three banks (six 6V batteries).

But those numbers assume a steady load of 1800 w, that's good for sizing the inverter, but not for sizing the batteries. Realistically, you need to figure average power, not peak power. For example, your microwave probably doesn't run more than 5 minutes. Your fridge cycles 15 minutes per hour max.

Figure your total Ah use overnight, then do calculations similar to the above to see how many batteries you need.

5. Dec 27, 2016

### dlgoff

Yep.
When maintaining a series of 10 deep cycle batteries for a multi-lab UPS, I wrote the SOP for the weekly and monthly maintance that included documentation. These deep cycle batteries tend to be quite expensive and "most" warranties will only be honored with some sort of documentation.

6. Dec 27, 2016

### Baluncore

Deep cycle batteries tend to use “AGM” construction rather than the higher current “flooded cell” batteries used to start vehicles, which have slightly different voltages. Batteries charged in parallel should be of the same construction and chemistry. If mixed battery types are used, the charging circuit will need to allow for the slightly different voltages or it will not fully charge both types.

At 20°C the 12 volt lead-acid battery charge maintenance voltages are;
13.167 volt Gel.
13.515 volt AGM, (absorbed glass mat).
13.719 volt Flooded cell.

7. Dec 28, 2016

### dlgoff

Construction images for these types compliments of Battery University.