How to maximize/extend a 12v coach battery’s life during boon-docking?

[perlgurl]

I just got back from a week boon-docking in Denali National Park.  I had a great time and no real complaints, but I did run out of power for the coach and I’m wondering why it happened.  We spent most of the time in the park and out of the RV, plus I don’t use many appliances while boon-docking so I’m a bit perplexed by the lack of power.  We only had a few nights with maybe an hour or so using the two overhead lights since we have over 21 hours of daylight right now, plus very occasional use of my water pump for some camp-style dish washing (cold water washing and/or boiling water on the stove for lukewarm washing), yet I found that we had run the battery down after just four nights.  We started the vehicle and ran it for 10 minutes to charge the battery for the first couple days we had low to no power (very, very dim lights) and the last day I even put my little 550w generation on for an hour and 15 minutes with a battery charger on the coach battery to give it a little juice to get us through the night, but it certainly wasn’t enough to fully charge the battery back up.


The battery I have is newly bought this year. I will be taking it to be checked out, but I don’t think it’s the issue.   

Am I just asking too much from a battery to be able to boon dock for a week? IS there something I can do to help extend the life of my battery without being on shore power or having to charge the battery with the generator? 

[Rickf1985]

Well, Seems every time I answer anymore it is in the negative. Hm? You are not going to like me anymore. N:( What you have is a SLI automotive battery, SLI stands for Starting, Lights, Ignition. It is basically made to start the car and provide power while you are driving and during any times when the alternator is not covering the entire load. It is not designed to be used as a reserve supply battery. It will provide a lot of amps for a short blast but it is not good at providing a low amount of power over a long time. You need a deep cycle battery for that. Your best bet is to get a second battery and either a switch to connect it to the charging system when driving or better, a diode type charging system that automatically senses the state of charge in both the vehicle battery and the house battery and will charge both at a decent rate. It is automatic so no need for switches and nothing to forget so you will not draw down the vehicle battery. There is a name for these and it escapes me right now, someone will get it or I will remember it later. They are not that expensive. My slide in has one battery (for the camper only) and I am lucky if I can get a week out of it without charging it. Electricity is math, it is easy to figure out exactly what you are using and how much battery power you need to run it. Just add up all of you power using accessories and subtract that from the amp hours of the battery. It is easier to find online charts that most of the battery places have for that though.

And here is the Isolator I was trying to remember earlier in the post.
https://www.waytekwire.com/item/80067/?gclid=Cj0KEQjwte27BRCM6vjIidHvnKQBEiQAC4MzrbD6VvUWvNKpFfYPvHHhzobpUC2z1aihrj9EaVborgQaApNr8P8HAQ

[Rickf1985]

You could also add a solar panel but check into that with the solar experts because up there in Alaska the sun angle will have a diminished effect on the amount of power you get from a panel. A panel rated at 400 watts may only give you 200 watts. Still enough to replenish a battery during the day as long as you do not really drain it at night and since you have no night.............................

[perlgurl]

Oh, wait! I have a DEEP CYCLE battery for the coach!  That other photo was the new one I bought to run the RV. 

[Rickf1985]

You did that on purpose didn't you? Your deep cycle should have lasted through the week with that little use. How old is it? And have you ever drained down to nothing?

[perlgurl]

And I do have the switch on my dash that allows for battery, DUAL or MOM. On the way out I only had it on battery.  I ran the DUAL on the way home and all lights are bright again, but I wonder if the deep cycle battery was a bit depleted before my trip? 

I also think I need to swap my lights for LEDS since they take less amps.  I like math (I'm a programmer by trade), I just haven't used it for electricity calculations.  I saw a thread where Dave talked about determining power needs so I need to go back and find that....

[Rickf1985]

I think you answered your own question, the battery was not fully charged when you got there. I would have it tested anyway. Math knowledge is a good thing. Little do most people realize that everything in the world runs on math. Think about that one for a bit and you will see what I mean.

[TerryH]

And once you do the math re LED's you will be searching for prices for LED's. Current draw, heat, lens damage, are all high points for converting. Initial cost 'may' seem high, but long term is definitely worth it.

[yellowrecve]

I don't know why shops sell Marine/DC starting batteries in place of true DC batteries. They are not the same. i??

[Aaarrghh]

And once you do the math re LED's you will be searching for prices for LED's. Current draw, heat, lens damage, are all high points for converting. Initial cost 'may' seem high, but long term is definitely worth it.

Amen! LED's are brighter and use a lot less amps. They fit in the old sockets just like the old bulbs. Buy them online. You'll pay ten times as much if you buy them in a store like an auto parts or RV store. It's amazing the prices the stores want!

[Rickf1985]

But do your research, there are good LED's and there are bad LED's. You get what you pay for and sometimes even that formula doesn't work out. I am just starting down that path so I don't have any good places to offer yet but try to find high quality LED's. More money but last much longer. The cheapo Chinese ones will blow out in months, also be sure to get LED's that are rated for voltages up to at least 20 volts since your system can hit 15.5 volts at times. The lower rated LED's are NOT forgiving, the pop instantly. You have to remember that they are not a light bulb, they are a diode.

[Rickf1985]

And the main reason they sell the marine starting batteries instead of true deep cycle is because they are selling them for boats mostly and smaller boats need the starting function. The camper stores can buy these batteries much cheaper than the deep cycles and make more money on them knowing darn well the average camper does not know squat about batteries.

[EldoradoBill]

The date code reveals the battery is over 4 years old, my guess would be it's time has come (and gone). 

[Rickf1985]

Good catch Bill, and on top of that I just read the side of the battery, "Super Start". That is NOT a deep cycle battery, regardless of what it says at the bottom. Deep cycle batteries are NOT starting batteries. You may be able to start a car with one but it is not good for them. If it advertises "starting" on there then it is a marine starting battery.