Pros and Cons of Second Truck Battery

[Jon R]

I did a forum search using the topic title I used above and didn't get any hits.

I'm pretty new here, and discovered this fine site while researching truck campers. I now have Grandby on order, and expect to have a lithium battery system with adequate solar to keep up with camper loads. I don't expect to have to rely on truck battery power for anything other than truck loads.

Since my existing 28 year old K2500 payload capability really isn't quite adequate for the camper plus tongue loads I anticipate, and because I don't want to rely on it for long highway trips and remote camping, I've decided to finally order a new truck. I have generally bought my vehicles new and driven them decades until they are used up, so I hope this new truck will last me twenty years or more. The truck will be used as a general utility truck, Grandby hauler, and 8000 lb boat trailer towing vehicle (sometimes hauling both the camper and the boat). I don't see myself ever towing a large RV.

I am interested in opinions or advice on two electrical system ordering decisions for my new truck (currently planning on a GMC 3500HD CCLB SRW gas with the heavy duty camper front springs (torsion bars) option):

1) Should I order the second battery option? I'm tending to "no" because I don't think I need it for any specific reason, it's a little more weight and complexity, and every six years or so I'll have to replace two batteries instead of one. Any pros or cons I'm missing?

2) The basic alternator is 170 amps. One can order a 220 amp single alternator or a dual setup with one 220 amp and one 170 amp alternators. I'm thinking order the single 220 amp alternator, again thinking a second alternator is more weight and complexity, but wanting the higher output single alternator. Thoughts?

I apologize if this has been covered before. I tried a forum search but didn't get any hits. Feel free to direct me to any previous discussions. Thanks.

 

[JHanson]

Hi Jon,

My answer would depend on what you want to do with the truck and camper. If you hope to do a fair amount of exploring in remote spots, possibly solo, then reliability should be paramount in your priorities. Battery failure is, depending on which statistics you believe, the number two cause of breakdown in the backcountry, next to tire issues. A dual-battery system essentially eliminates this risk, as the chances of both batteries failing simultaneously are remote. All of my four-wheel-drive vehicles have dual-battery systems.

Alternators are fare more reliable and durable, so your choice there is more personal. If your alternator will be charging the "house" battery (s) in the camper while underway, then I'd lean toward the more powerful option.

 

[Jon R]

Thanks for the response JHanson.

I agree that's a very good reason to have the second battery, and I expect some of my usage will be remote camping without a companion vehicle. The option is pretty cheap, and I can choose not to install a replacement battery and disconnect the wiring at any time if I decide I no longer want to pay for the redundancy. I think you've convinced me to get the second battery.

Thanks again for the advice.

 

[Kolockum]

I agree with going for the most powerful alternator. If I had the money I would go with a 2 battery set up for my truck. But I have my camper (house) battery that I can hook up to my truck battery if I need more juice.

 

[rando]

I may be wrong, but is a factory second battery not just in parallel with the first battery? In this case I am not sure it would provide much redundancy. If you were to run the truck battery down, with this setup you would end up with two flat batteries. Furthermore if you were to have a battery failure such as shorted cell, then the failing battery would also take out the other battery. It would protect against an open circuit battery failure, but these are relatively rare.

If you do want redundancy, you would be better served by a dual battery system with isolation between the systems. Ordering the second battery and modifying it to be a dual battery as opposed to parallel batteries may be an easy way to get a dual battery system, but may not be the cheapest. Also, your camper battery already kind of does this.

My solution to this is to carry a lithium jump pack - this gives me redundancy to get my truck going if the starting battery is flat or fails, but also allows me to easily start other vehicles I encounter - which is all I have actually used it for. For $50 - $100 and 2lbs it was the best solution for my needs.

 

[Jon R]

The option description implies they have a battery isolator, but doesn't explicitly say that. I’ll make sure to ask.

The lithium starter pack is a good suggestion for me to consider in lieu of a second battery. I like to help people when I can, but I've always cringed when hooking up my modern computer controlled cars via jumper cables to somebody else's dead electrical system. A starter pack would eliminate that concern.

Thanks for the replies.

 

[Kolockum]

I forgot to mention that I also carry a little jump pack. It says plugged in all the time so it will be ready when I need it. I have used it several time to good effect.

 

[Hoopy]

kllockum,
I like the idea of a jump pack I have a friend with one and he has used it on a trip saved his bacon! I will have to check his out.
hoop

 

[Beach]

My 2 cents is to go for the single battery(largest capacity you can get) with the high output alt.. Carry a lithium jump pack for the rare occasion you might need it. I have always carried a jump pack and have only used it twice(if my aging memory is correct) in the past ten years for my own vehicle, but several times for others. Just replaced my old pack this summer and instead of getting a minimal pack I got one rated for 6.0 diesels, even though I have a 6.2 gas motor.

 

[ntsqd]

I think that the jump-start packs are a good idea. I carry one in all three of our off-pavement capable vehicles. XP-10's in the two serious trucks, some off brand in the DD.

With the dual alternator & dual battery options I'd be inclined to set up one as the starting battery and one as the truck battery. Starting battery only starts the truck, truck battery does everything else. Higher output alternator connected to the truck battery & camper battery(ies) connected to the truck battery via an ACR/VSR.
That would be an over-the-top, blue water marine solution to a ground vehicle problem that may or may not exist. It would be cool though!

 

[JHanson]

Each of our vehicles carries a Microstart; they are brilliant. However, I still prefer to have a redundant main battery system, which as has been mentioned does need an isolator. (And remember those lithium power packs need recharging too!)

 

[ntsqd]

I'm not sure that those lithium jump-start packs want to be constantly charging. My XP-10's appear to hold a charge for a very long time. This is something that I've tested. Yeah that's what it is, I'm not that forgetful. I'm not, I'm not, I'm not.

Maybe their charge controller is fine with having always power applied or always having power applied while driving, but I'd rather not take that chance. Besides, this opens up an opportunity for a Project! I've toyed with various schemes to intermittently charge them while leaving them plugged in. At first I was thinking of a timer that would only close the circuit to the power port for some set time period. Finding the parts to do that simply without resorting to using an Arduino or similar wasn't going well.

Then I realized that a delay-on relay could work. If I wanted to limit each charge time I could use a delay-off relay in series with the delay-on relay. Set the delay-on relay to delay turning on for ~20 minutes after each engine start, which is longer than most of my drives and would only turn on during a trip of some sort. That would effectively space out the charging intervals. Found those, they're only $63 each. and $63 again for the delay-off relay. Argh. Too much cost for the application. Back to thinking on this......

 

[JHanson]

I don't keep our Microstarts on constant charge. Recharge once every few months is sufficient.

 

[ntsqd]

Yeah, if I could only remember to actually do that.....

 

[craig333]

Do you have or are you likely to add a winch at some point? That might be your motivation to add a second battery.

 

[Kolockum]

Do you have or are you likely to add a winch at some point? That might be your motivation to add a second battery.

Oh man. Very good point. You have just convinced me.

 

[fuzzymarindave]

I woke up one morning in the snow country and my truck would not start. I had to jump start it with the camper house battery which i had to remove because I don't have 2-way wiring to the truck. I worked fine until I was able to buy a replacement battery. It was a bit of hassle but not enough to make me want to have two batteries in the truck plus a third battery in the camper. If your camper is on full time you will always have that reserve house battery.

 

[craig333]

I've jumped mine before with the camper batteries. Kind of slow with 10ga wire. I've since upgraded to 6ga but I also put new batts in the truck. Haven't needed to use the new wiring since (either direction).

 

[LuckyDan]

For those who remember when manual transmissions were the norm and fuel pumps were mechanical, I’ve been reminded the easy/hard way that the days of get rolling down hill and pop or bump starting a dead rig are largely a thing of the past. I just aborted a mission to recover my brother who’s Ranger battery died while camped out. He tried the roll and start repeatedly to no avail. I got lucky, I was only about an hour or so out of town when he called that a couple Chucker hunters gave him a jump. He was on day two of no battery.

Point is; if you get truly remote, in places where largely you’re left to your own devices for recovery/repair, for awhile at least and do so fairly frequently, either some sort of redundant or auxiliary system is probably not a bad idea. The work arounds are fewer than they used to be.

 

[Wandering Sagebrush]

For those who remember when manual transmissions were the norm and fuel pumps were mechanical, I’ve been reminded the easy/hard way that the days of get rolling down hill and pop or bump starting a dead rig are largely a thing of the past. I just aborted a mission to recover my brother who’s Ranger battery died while camped out. He tried the roll and start repeatedly to no avail. I got lucky, I was only about an hour or so out of town when he called that a couple Chucker hunters gave him a jump. He was on day two of no battery.

Point is; if you get truly remote, in places where largely you’re left to your own devices for recovery/repair, for awhile at least and do so fairly frequently, either some sort of redundant or auxiliary system is probably not a bad idea. The work arounds are fewer than they used to be.

That’s why I keep a jump start pack with me.