Battery banks. Can I mix different batteries?

[Tom MacCallum]

Howdy,
My first Topic on this forum.
We’re taking off next Summer to travel extensively for what my wife says will be for two years while we look for our next spot to land. This idea sort of came about after we borrowed a friends small Adventurer TC and drove to Alaska for a 12 day river trip that we got a permit for. The river trip was fantastic, but we had a blast with the truck camper. We boondocked all over S. AK, YT and BC. On our 8 day trip back to UT we paid a grand total of $6 CDN to camp.

We bought a 5 year old Adventurer 910 FBS in August and remodeled it for better usable storage, fixed some issues here and there and added 200W of solar panels. The previous owners had replace the batteries this past May with some NAPA group 24 65AH “hybrid” deep cycle marine wet cell batteries. There’s room in the battery box for (2) group 31 batteries. I’m thinking of replacing the present batteries with 125AH AGM batteries. I was thinking of taking the NAPA batteries and installing them in the wheel well of our F-350 LB.

So, how to charge them? I assume I can’t build a single battery bank and hook them all up in parallel. I thought of hooking them up to the truck alternator and installing a rotary switch in the camper that would bypass the AGMs and use the wet cells if we needed to. We do have a Onan generator if we really need it, but on a long weekend down to the southern UT area the panels kept the batteries charged up just fine even with the furnace running at night. It was in the low 30s at night. All of the lights are LED. I’m planning on installing an inverter to run the coffee grinder and drip coffee pot in the morning. Off the top of my head, can’t think of much else that will require a whole lot of power. However, a 6 cu. ft. compressor fridge/freezer could be in our future. I’ve also thought of adding another 100W panel.

Am I over thinking this and the AGMs will be fine? Curious what better minds than mine might think.

[Mello Mike]

If it was me, I’d ditch the Group-24 hybrids and get the Group-31 AGMs. More amp hours and you’ll be much happier with them. You won’t have any trouble selling the old batteries.

[Anonymous]

You should be able to charge both banks if you get one of these:

http://www.xantrex.com/power-products/power-accessories/auxiliary-battery-charger.aspx

On edit, assuming that AGM and the hybrid wet-cell are spec’d for the same (or very similar) charging algorithm, I doubt the charger will ‘see’ much of a difference – I would research each battery types charging requirements…

[Anonymous]

To follow-up, A mix of either AGM and Gel or Gel and FWC would certainly not be doable due to dissimilar algorithms. All JMHO.

[Jeff Sherman]

Tom,
You are right – the AGMs and the deep cycle batteries can’t be hooked up to the same charger. To charge the deep cycles in the wheel well if they are hooked up to the truck alternator for charging, means you would have to run the truck engine to charge them. Sort of inefficient if you happen to be parked somewhere for days and not needing to drive.
And I would never put that type of battery in a place where I could not inspect them – maintenance free or not. If they are ahead of your wheel well in your truck bed you would have to lift the camper to check on them.
I would do as Mike suggests, sell the deep cycle batteries, and go with all AGMs. As for locating the third (or fourth) AGM, the wheel well is a possibility for an AGM.
I would suggest that if you really are intent on getting a third or fourth battery, hook all your batteries in a single 12 volt parallel system, and buy identical batteries all at the same time so the batteries in the camper and the extra(s) all have the exact same charging characteristics. Not a good idea to mix old and new batteries if you were to buy the extras later. And put them all on the same charging systems – your solar charger (set for AGMs) and your Onan/120v converter. That is a lot simpler system to put together and maintain than mixing battery types and involving the truck alternator.
Look at Lifeline AGMs – they have served me well.
Jeff

[Jeff Sherman]

Tom,
One more important consideration. I note you are planning on installing an inverter.
Depending on the amperage/wattage of the inverter, you will be needing some very heavy cables from the battery bank to the inverter. The inverter you choose will likely suggest the gauge cable needed to feed it. Please consider that the extra battery in your wheel well will be some feet away from your in-camper house battery pair. That means when you install your parallel cables to connect all your batteries in to one parallel system, you will have to consider they will need to be at least as large as the cables needed to feed your inverter. They certainly can’t be smaller. Don’t forget if you have a shunt for a battery monitor the negative for the inverter has to come off the load/downstream side of the shunt. All in all, between the battery bank, the extra battery, the shunt and the location of the inverter, you are likely to have surprisingly long runs of cable which means you could have significant voltage drop. There are online DC voltage drop calculators that you can use to check that. You will have to use the relatively high amperage of the inverter when you enter your data into a voltage drop calculator and that will really increase the voltage drop. And remember that the charging voltages from your solar charger and your Onan/converter are measured in tenths of volts so it is easy to have too much voltage drop with too small cables that affects the charging voltage ultimately seen by the most distant battery. Having that extra battery at some distance from your house battery means that it may see totally different voltages then the house batteries if your cables are not big enough.
Long story short, you only install the cables once. Whatever the inverter suggests for a cable gauge to feed it, you may have to upgrade one or even two sizes heavier (larger cable = smaller gauge number) to make sure you totally minimize any voltage drop in your system. Figure your voltage drop length from the inverter, through the shunt and through all the parallel cables to the furthest battery. And I would size the cable so the voltage drop between your in-camper batteries and your wheel well extra battery is negligible. I would make make all the cables in the parallel system and to the inverter all the same size – defaulting to the size needed for the longest run.
And I would suggest ordering marine cable for that purpose – it is much finer stranded and is so much easier to route and install IMO. You can order online any size cable and color from Greg’s Marine Wire Supply. They sell it by the foot and also sell lugs by the piece, heat shrink by the foot, and solder pellets by the piece. I use solder pellets for the heavier cable lugs on my rig so I did not have to find/borrow or buy a hydraulic crimper. Stripping the marine cable does take some care to avoid cutting the fine strands but I do it with a utility knife, take my time, and rarely cut a strand.
Just something to consider when adding an extra battery and hooking up to an inverter.
Jeff

[Tom MacCallum]

Thanks everyone of the responses. I should have clicked on the email notification or I would have seen this sooner.
BTW Mike, love this site since we’re a couple of old rive rats that are new to TCs or RVs of any kind for that matter.
OK, I’m going to ditch the NAPA batteries per you alls suggestions. My Scottish gene getting the better of me. I’ll sell them. It’s not like they’re high end batteries.

I had already decide to go with the Lifeline Group 31 125 AH batteries in the battery compartment. We could easily(except for the cost) put another one in the wheel well which happens to be almost right under the the battery compartment, so minimal voltage drop due to short wire runs. Maybe this is over kill, but if we’re up north and have a few cloudy days in a row, this will delay having to use the generator. On our one and only trip so far with this camper down to “Valley of the Gods” in S. UT, the panels would charge the batteries to 13.5V and they’d be down to around to about 12.6.-12.7 in the morning using the furnace@55* in 32* temps, some lighting, and Sirius radio. This was with blue bird days the whole time. I’m definitely going to add a 3rd 100W panel. Unfortunately, I’ll have to install a large controller since the the Renogy 20A MPPT is only rated for 250W of panel input.
My thoughts on using the truck alternator to charge the auxiliary battery was just to charge when driving, not use it as another generator. This was after reading Cal Willis’ and Duncan Crawford’s articles in TCA. I was thinking of using this isolator or something similar if I go this route. http://hellroaring.com/bic95150B.php

Jeff, Thanks for the very thorough reply and especially the tip about marine gauge wire and how important voltage drop needs to be taken into consideration. TCs aren’t the easiest to route wires around. Luckily, our Adventure has a nice size chase between the wardrobe and the shower shell to get wires from the roof into the camper, but getting them between the cabover floor and the shower is a bear. Having installed the 10ga wire that came with the Renogy kit from the junction box on the roof to the controller and then switched it out to 8ga wire, my wife and I have become quite the contortionists at getting wires where they need to go. After reviewing some of the voltage drop charts, We may be doing it again with a heavier gauge. Getting the wire from the batteries compartment to the inverter location is relatively easy and short. The shunt is right next to the battery compartment.

So, a couple of questions since I’ve got you all here. Where is the best place or site to get the Lifeline batteries from?
The 100w Renogy panels at optimal output, produce 5.29A. If I have (3) panels on the roof is 8ga braided copper wire sufficient to conduct 16a 15′ to the controller and then 8-9′ to the batteries? The various calc table I found confused me by including load in the calcs.

Thanks
Tom

[Tom MacCallum]

Hmmm….after looking at his chart, I think I need #4 wire from panel junction box to batteries.
http://www.affordable-solar.com/wholesale/solar-tools/wire-sizing-charts/

[Jeff Sherman]

Tom,
The cable run from the roof panels to the controller should not be included with the cable run from the controller to the battery in terms of sizing the cable. Two different considerations. Here is why.
Your roof panels are probably producing 17 or 18 volts. Any small voltage drop getting down to the controller will only mean you will have slightly less watts (amps x volts = watts) at the controller. My Bigfoot had 8 AWG already installed to the fridge vent for solar so I was stuck with it – no way to change it. If you already have 8 AWG from the roof to the controller I would leave it. Just might mean a few less watts for the controller to process than 6 AWG. No big deal. And often the wiring to the j-box on the roof from the panels is 10 AWG anyway.
But from your controller to the batteries cable size is a big deal and voltage drop should be minimized. If you look at the Lifeline AGM manual it specifies 14.41 volts for absorption at 70 degrees F. Lets say your controller set for AGMs puts out 14.41 volts for absorption. If you have a 2% voltage drop from your controller to your battery, that is 0.29 volts. That means your batteries are only getting 14.12 volts for absorption. Not good.
So I would leave the 8 AWG to the roof as is. But determine size of the cable from the controller at your distance of 9 feet to the battery. I think you will find that the cable size will not be that bad. You will have to use the max amp and voltage AGM output of your controller for your variables. It won’t be the 17 volts your panels are producing. It will be closer to the 14.41 absorption volts. And the amperage will be based on what your controller produces from your panels. With an MPPT it will be more amps than the panels produce because the controller reduces voltage from the panels in order to increase the amperage to the batteries.
I used 6 AWG in my system from the controller to the battery. And check your controller – it may only take certain size cable. For my Victron 100/30 MPPT, the max cable size was 6 AWG anyway. I like the smart phone control for the Victron MPPT. And now I think on certain models they have the Bluetooth transmitter built in to the controller. But getting the dongle is no big deal either. The graphics are better now, too.
https://www.truckcamperadventure.com/2017/07/review-of-victron-battery-monitor-and-mppt-controller-with-smart-phone-display/
Here is the voltage drop calculator I use:
https://www.calculator.net/voltage-drop-calculator.html
I ran the 16 amps at 17 volts for 15 feet using 8 AWG from your roof and you will only have .30 volts drop. That means your controller will see only 4.8 watts less (16 amps x .30 volts) due to voltage drop on the 8 AWG from the roof. Not a big deal.
Don’t know where you live to get your Lifelines. I googled it a lot when I needed mine and ended up ordering and picking them up at a marine supply house in Seattle, so do not limit yourself to RV supply houses. I did not see too much variation in the low end of pricing – no screaming deals. But you do want to stay away from places that mark them up too much. Freight cost is a big factor. I would not have them shipped directly to your house. A dropped battery along the way and you may end up with a bad battery. I think the freight deliveries to larger supply houses are more reliable for heavy, fragile batteries – JMO.
Hope this helps.
Jeff

[Tom MacCallum]

Jeff,
Thanks again for the detailed reply. Had some log-on issue and couldn’t reply sooner.

Great article on the Victron BM and controller. I have the battery monitor, but I was really dumb and didn’t get the wireless dogle with it. I’ll rectify that. The display on the monitor is practically worthless.

Since I have to change out the controller because I’m adding a 3rd 100w panel, I was thinking of using the Victron 100/30 after reading the article. Since the 100/30 doesn’t have a display, I could mount it closer to the batteries and reduce the wire run from the panels by a couple of feet and reduce the wire run from the controller to the batteries more than that. Possibly 3′ to 4′ The Renogy 20a controller has a display, so I mounted it on a wall sort of close to the batteries. Hence the 8-9′ wire run. FWIW, The Renogy Controllers can only connect using a maximum 8ga wire. My only hesitation on using the Victron controller is that it has a built in temp sensor. It would be on the warm inside of the camper right beside the battery compartment. Actually about a foot or so from the furnace. The Renogy has a remote temp sensor that is in the battery compartment. I need to go back and read the article later today to read how you dealt with that. I’ve got time to figure all of this out. The bummer is that the camper is in our storage unit about 20 minutes away. Not exactly convenient to go running down there to fiddle with it unfortunately.

Thanks again for the help.
Tom

[Jeff Sherman]

Tom,
I agree. As good as Victron equipment is, having the temperature sensor internal to the 100/30 is stupid. Should be at the end of a 10 ft wire so you can put it on a battery or at least in your battery box.
You may want to find a controller that more suits your set up and has a remote temperature sensor.
My 100/30 is right next to the battery box but no issue with a close by furnace.
Good luck.
What river(s) in Alaska did you do? I lived there 42 years….
Jeff

[Tom MacCallum]

Jeff,
I saw you lived there that long. It’s a beautiful place. We did the Tatshenshini-Alsek Rivers. It’s close to Haines…sort of. We rented all of the rafts and gear from a Haines outfitter. We did that because his gear breaks down enough to go in an Otter. He dropped us off at a put-in on the Tat in YT. From there we floated thru BC and then into AK where the Tat confluences with the Alsek. We took out at Dry Bay, near the coast and flew back to Haines. Some folks flew to Yakutat. Due to weather(really bad and low ceilings), we flew back up the river and it was just awesome see what we had come down. We had some amazing weather. At Alsek Lake where two glaciers flow into the lake we had a couple of blue bird days to oar out near the icebergs. Some as big as a small cruise ship. We had an experienced crew. 5 of the 8 of us had about 30+ 20+ day trips down the Grand Canyon between us. The Tat-Alsek was a truly wilderness experience. Although my wife and I saw some grizzlys on our travels, we only saw one from a distance while on the river. Other folks saw a couple, but the bears ran off as soon as they noticed them. There’s not much bear/human interaction in that region.
Our plan (and the reason we’re modding this camper) is to cash out of our house here in the Park City, UT area and go back up to AK around June/July for an extended trip. Then we’ll look for the next spot to land. Possibly MT , but who knows.
Sorry to be so long winded there.
Thanks gain for your great help.
Tom

[Jeff Sherman]

Tom,
When you mentioned your trip was to southern Alaska and you were on a river trip I figured it was the Tatshenshini/Alsek. Never did it but always wanted to. Did a few rivers in other parts of Alaska.
In ’76, some friends and I flew into Bettles, put in on the Koyukuk River, went down it about 80 miles, then lined our Kleppers up the Alatna River about 200 miles to the headwaters, portaged over the continental divide to the Noatak River and went down it about 300 or 400 miles to the village of Noatak. (Not sure my recollection of river miles is still accurate after more than 40 years…) Total of 90 days in the Brooks Range, resupplied only once after the first 3 weeks near the Arrigetch, with another 9 weeks of food. Other than the bush pilot that brought our food, we only saw two other people the entire summer.
Also did some winter X-C ski trips in the Brooks – it is great for that – broad, U-shaped, flat bottom glacial valleys, minimal avalanche danger but some wild overflow (aufeis) in places. Through the Gates of the Arctic with a friend one winter and then the next winter I did a solo ski trip from Anaktuvuk Pass west to the headwaters of the Alatna (to tie into that summer trip) and back – couple hundred miles. Both winter trips with no tent, no stove. Cooking over fires (ability to find dead standing willows or alders is key).
The Noatak is the Queen of the Brooks Range Rivers but there are many others you might consider. But as you well know, you have to fly in and/or out to get into the real wilderness. But a truck camper can get you to some great areas. I imagine you have some ideas of what you want to do.
Driving into Wrangell – St Elias NP is fun on the old Copper River railroad bed. Can’t drive into McCarthy but you can park & dry camp for $ just before the footbridge and walk in. Used to be a tram back in the old days. You could fly in from McCathy and do the Goat Trail.
I did the Grand Canyon just once – in 1980. Three of us from Alaska. Two were in kayaks and I was on an old army surplus vintage 10 man raft. Started off with old split oars, wood rowing frame made of old 2×8’s, leaky old rubber army surplus dry bags, etc. Low budget…. We put in the day after Thanksgiving and took out at Lake Mead the day before Christmas. The Park Ranger at the put in told us no one was on the river ahead of us and no other parties were scheduled till after Christmas. So we had the entire Colorado River in the Grand Canyon to ourselves for 30 days. That is not likely possible anymore. I am reluctant to do it again because I am totally spoiled after that.
Back to Alaska. Other than the road into (or almost to) McCarthy, I can suggest the Denali Highway. If you do the Haul Road (the Dalton) to get into the Brooks Range, I can give you some tips. Lived in several different places in pipeline camps along the Haul Road for two years so know it really well. Would not recommend going further north in a truck camper than Galbraith Lake or Slope Mountain to avoid the flat, dusty or muddy miles to Prudhoe Bay. The road will be hard enough on your truck & camper, no sense prolonging it.
Also suggest getting campground reservations (as soon as possible) in Denali National Park so you can drive your rig deep into the park. Once at the campground you can’t use your truck but you will be in the park and can use shuttle buses. You don’t want to camp outside of the park – too crowded – and you are not in the park. Incredible wildlife viewing in the park.
If you want some ideas or my take on a particular area or truck camper access, let me know. Maybe we could somehow exchange email addresses.
In any case, have a great trip.
Jeff

[Jeff Sherman]

Tom,
Another truck camper / river trip option.
Via road there are only two ways into Alaska: the Alaska Highway (at Beaver Creek) or the Top of the World Highway out of Dawson. You should consider going up via Dawson and the ferry across the Yukon and do the Top of the World Highway. The Fortymile River is designated a Wild and Scenic River and you could do it. Dawson is a great little town. Also consider getting into Tombstone Territorial Park in the Yukon on your way to Dawson.
Coming out of Alaska on the Alaska Highway you could leave as late as late September or early October and still have bare pavement depending on weather. We have done the Alaska Highway / Cassiar maybe 7 times in our truck and once in our camper. Several times in winter conditions.
The Top of the World Highway is only an option when the ferry is running across the Yukon. So leaving late in the season means leaving via the Alaska Highway.
Jeff

[Tom MacCallum]

Jeff,
Wow! A 90 day river trip! In Alaska. Impressive. And in a Klepper no less. I feel like such a whimp thinking our little 12 day trip was such a wilderness experience. 🙂 (It was though) I was surprised at how many other groups we saw on the Tat-Alsek. Three commercial trips and another private trip on our next to last day.
Yeah, the Colorado R. thru the Grand Canyon is not even close to a wilderness experience anymore. It’s glamping. Commercial power raft trips passing you every day. Private and commercial oar trip competing for camp spots. It’s still a cool place. The hikes are always fun. There was one time a few years ago when we hadn’t seen anyone for about 2-1/2 days and we were wonder what had happened. Alien invasion beamed everyone up but us? The Rapture happen? We’ve never run out of beer though. Even on our last 23 day trip.
Thanks for all of the suggestions for Alaska. I read about the McCarthy Road on another forum today. Our timing is a little up in the air. We plan to get our house on the market no later than early June. We’re going to try for May if we can swing the remodel faster. Our neighborhood is super hot right now. If it priced right and isn’t a gambrel roof most houses around here have a contract in one to two weeks. Fingers crossed they don’t hike the rates too much between now and then. As soon as it’s sold, we’re heading north.
Thanks again for all of your help
tom.maccallum(at)gmail.com

[Joe Monstermaker]

Don’t use that or any battery isolator.
They have some voltage drop and are failure prone.
A continuous-duty solenoid is a much better setup.
You can control the solenoid however you like.
I’ve done it with a wire that’s hot when ignition is on, with a manual switch, and I’ve even used an oil pressure switch (you switch the ground to the solenoid instead of the +) so it only connected when the engine was actually running.

Use at least 4-gauge charge wires to your camper batteries.
I use 2-gauage. Your batteries will charge great from the truck that way.

You’ll want at least 2-0 (two-ought, rather huge) cable from your batteries to your inverter to run a coffeemaker. Even bigger is better.
Sometimes when wiring inverters I even double up and stack two positive and negative cables. It really does make a difference.
Be ridiculous about the battery cables.

[Tom MacCallum]

Joe,
Thanks for the advice. I have no problem being ridiculous about gear and mods. I’m probably going to stick to just two group 31 125 Ah batteries at this point. I thought about a 200 Ah Li battery, but the weight savings to cost just didn’t make sense at this junture. (Thanks Mike for the article about Li batteries.)
I haven’t looked at any of the inverters yet. Can one attach (2) pair of heavy cables to them? Probably depends on the brand. Time to start figuring the wiring diagram for this thing. I hate having the camper in our storage unit and not having easy access to it, but this has been one of the epic winters we sometimes get here.
Tom

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