Two battery + Solar + Alternator questions...

[Kodachrome]

Hi gang,

I would post this in the ATC section since that is what I am running, but this side has good info too so I like to split it up a bit. Basically, I added 100 watts to my existing 85 watt panel on the roof in order to power a new AC/DC fridge which has been night and day better than the old 3-way. You can see that set up in this blog post.

Well I am so happy with this set up that I am replacing the 85 watt panel on the roof with a 180 watt so I am fool proof in winter / shady day excursions too at 280 watts. So with all that power, I got to thinking that two batteries would be a smart idea. I have a Sears Die Hard Group 31 that pretty much kicks butt and I also have my relatively new Optima Blue Top sitting in my storage now unused because you need to pair the darn things.

So what I want to do is use the Optima as a backup battery in that it only will get a charge from the truck 90% of the time and solar in a pinch, but not both. The same goes for the Sears. I want to be able to use both batteries in the following fashion: While I am driving the truck, the Optima is getting charged by the alternator while the Sears is getting charged by the single full time 180 watt panel on the roof, the 100 watt under cabover panel is stowed while driving. WIth a switch, I would like to be able to also make the choice of running the fridge while driving off of either the truck charge or solar. This way, while driving, the truck would most of the time only be charging the Optima and there would be less load taken from not running the fridge that could be used for charging phones, iPad's, Laptop and running a GPS. The fridge runs perfectly with just the solar, no alternator needed, not even on cloudy days.

This way, I can use the one heavy Group 31 battery as my primary and my much lighter Optima as the Aux. Having them on switchable load and charge modes would in my mind, eliminate the need to have two of the same kind and date of battery and make replacing them far cheaper since there would not be two to deal with at once.

So what do I have to do here in order to get this going? Do I need a second battery separator? What kind of switches, fusing if any?

 

[billharr]

I used second battery as a back up on a boat years ago. They still sell the switch I used.
http://www.westmarine.com/webapp/wcs/stores/servlet/ProductDisplay?productId=112462&catalogId=10001&langId=-1&storeId=11151&storeNum=10109&subdeptNum=10548&classNum=10597

I am sure there will be some one with more expertise on how to switch the load and the change. Everything I read says you should keep different size and age batteries separated to change.

Looking at a Sears Platinum Group 31 one now to replace my 2002 Optima guess they don't live for ever.

 

[Kodachrome]

I used second battery as a back up on a boat years ago. They still sell the switch I used.
http://www.westmarine.com/webapp/wcs/stores/servlet/ProductDisplay?productId=112462&catalogId=10001&langId=-1&storeId=11151&storeNum=10109&subdeptNum=10548&classNum=10597

I am sure there will be some one with more expertise on how to switch the load and the change. Everything I read says you should keep different size and age batteries separated to change.

Looking at a Sears Platinum Group 31 one now to replace my 2002 Optima guess they don't live for ever.



I have this one in hand:

http://www.amazon.com/Blue-Sea-Systems-Battery-Selector/dp/B000MMFJH0

I just need to get the details figured out, if I need a second separator and another switch for load..

 

[K7MDL]

I think this is what you described:

Truck to isolator/charging relay to Camper power panel and Battery 1 terminal as stock.
Battery 1 to Switch Terminal 1 (wired to the stock isolator/charging relay and charged by truck)
Battery 2 to Switch Terminal 2 (charged by solar)
Solar charger to Switch Terminal 2
Wire the Fridge to the Switch Common
Leave the Switch on Battery 2.

Since you think the solar will cover the fridge 100%, then you should rarely ever operate the switch. In fact I do not see the need for a 2nd battery and loosing the space it takes, plus extra weight.

What is missing from the above switch solution is the ability to use the solar to charge Battery 1 except when "both" is selected. If you want to have this Battery 1 solar charge option (and not parallel both battery long term), yet keep things simple and inexpensive, you could install a fuse (like a ATC/ATO that is easy to pull out without tools) or manual breaker in-line with Battery 2 to isolate Battery 2 and position the switch to 'Both'. Leaving the fuse in would give you a boost option if needed.

So the new wiring would be:

Truck to isolator/charging relay to Camper power panel and Battery 1 terminal as stock.
Battery 1 to Switch Terminal 1 (wired to the stock isolator/charging relay and charged by truck)
Solar charger to Switch Terminal 2
Manual breaker or inline DC switch to Terminal 2
Battery 2 to Manual Breaker (charged by solar)
Wire the Fridge to the Switch Common
Leave the Switch on Battery 2


Select Batt 1 to operate fridge off stock power setup (and Battery 1). Batt 2 is solar charging.
Select Batt 2 to operate fridge off solar charged Battery 2.
Open breaker (or remove fuse) to Battery 2 and select Both to solar charge Battery 1 and run fridge off truck/Battery 1.
Select Both (leave breaker on) to boost and solar charge batteries in parallel for a short time.

I use breakers or fuses within inches of my battery connections and I recommend you do also. That means this plan is very easy to accomplish with the marine battery switch. Many manual marine breakers are panel mount and could be installed easily near the battery under a seat.

- Mike

 

[Kodachrome]

I'll have to think about this some more then. ATC built me a battery box that is right below the sliding window, it will hold both batteries with a minor mod.

The thing is I want all the camper utilities pulling off of the big battery and solar under normal conditions, the smaller Optima as a backup. So let's say the Optima is pretty much always charged by the truck and the big battery by the solar. Then I run into a situation out in Utah in the Winter where there is not as much sun and until I can run the truck, I am slowly running out of juice. It is in that pinch I would want to pull power off of the Optima in the day while the big battery gets a little better top off or vice versa and so on.

I am just trying to do my best in taking advantage of having a crap load of solar, a spare battery laying around and absolutely see the need for all of it in the Winter months.

I think even though it could be easy, I might just put the new panel on this week and then have Marty do the new electrical when I am out in Sac in late October.
When I was in New England last October, it was amazing just how little a single roof mounted 85 watt panel did even with running the 3-way on gas, LED lights, I had to really watch it if I did not move the rig for a few days......even in the noon hour, it was so freaking dark.

By having 180 on the roof and 100 more deployable at any angle, I hope to really be able to stay out there a long time, get work done, charge devices, etc.

 

[K7MDL]

So you want the fridge and the other loads on the same battery, solar charged, not split with the fridge dedicated to the solar charged battery as I had interpreted.

So a revised plan:

Truck to isolator/charging relay (truck side)
Charging relay to Switch Terminal Common.
Remove DC Panel battery feed from charging relay and connect to Switch Terminal 2
Manual breaker (or inline DC switch or fuse) to Switch Terminal 2
Diehard battery to Manual breaker.
Solar charger to Switch Terminal 2
Optima to Switch Terminal 1 (via a fuse close to battery)

Select Batt 1 for normal operation. Truck will charge the Optima.
The Diehard will be solar charged and run all DC loads.
Select Batt 2 to truck charge the Diehard. Solar stays connected.
Select Both (leave breaker on) to boost and solar charge both batteries in parallel for a short time.
Select Both and open the Diehard manual breaker to isolate teh Diehard and solar charge the Optima and power all DC loads. The Diehard is isolated and is therefor not charging either.

A variation is if you wanted the Solar to always charge the Diehard, and never the Optima. Then connect the solar charger to the Diehard and not to the battery switch as above. The Diehard would recover while the Optima discharges. Assuming the truck is not running, no real gain though. Solar left on the Switch terminal means it is charging the Optima so slows down its drain rate and gives you the same total run time in either case.

 

[Kodachrome]

Something tells me you would love to come out to Aspen in a couple weeks to get a personal grand tour of Fall colors, a great five star dinner at one of our fine eateries all for the low price of helping me not burn my camper up....;-D

When you say charge in parallel for a short time, we are talking the kind of thing I may have to do once or twice a year and for no more than what, an hour or two at a time since batteries are not blood related?

Also, what kind of manual breaker are we talking?

 

[K7MDL]

Something tells me you would love to come out to Aspen in a couple weeks to get a personal grand tour of Fall colors, a great five star dinner at one of our fine eateries all for the low price of helping me not burn my camper up....;-D

When you say charge in parallel for a short time, we are talking the kind of thing I may have to do once or twice a year and for no more than what, an hour or two at a time since batteries are not blood related?

Also, what kind of manual breaker are we talking?


I was in Sandpoint ID Aug 12-14 and Glacier NP and Idaho Hwy 12 Aug 15. Was supposed to go to Colorado (Edwards, Pagosa Springs, others) Aug 16-28 to ride dual sport motorcycles with some Moab riding friends. I changed plans late in the game and went for a 4 day islands kayak camping tour on the west side of Vancouver Island (Barkley Sound, Broken Group - had excellent weather, tour), something else I always wanted to do, having fished up there for 7 years. Might be down your way next year, but I doubt you will wait that long

There are multiple ways to to acheive the inline battery isolation. The removable fuse is the simplest, and even better if panel mounted. The next step up is a Rocker switch in series with a fuse or resettable breaker. This is the most common for economic and cosmetic reasons. The most expensive is a combo switch/resettable breaker like this example
http://cgi.ebay.com/ebaymotors/CARLING-40-AMP-BOAT-OFF-CIRCUIT-BREAKER-/190490471006?pt=Boat_Parts_Accessories_Gear&hash=item2c5a1dea5e for $33. A clean solid solution in one package. Of course they come in all sizes. This one requires a square hole which is a bit harder then the round hole options, but it is usually not hard to find a small sheet metal silkscreened panel trim for these.

For the Both in parallel scneario, I would only expect you use it long enough to get the immediate task needed, so maybe a few minutes. As long as the low battery is not failed, it is not a big deal. The problem is from long term scenarios that result in under or over charging and one battery doing more of the work over time. Overheating and cook-off, gas release is another worst case side effect.

 

[Kodachrome]

So like a goof, the 180 watt panel was 24 volt, no good in paring with my 100 watt /12 volt. So I took a drive out to a nice local store and got a good 135 watt that is only 10 pounds more than the 85 watt it replaced.

http://www.solarpanelstore.com/solar-power.large-solar-panels.kyocera.kd135lpu.info.1.html

We had it in within an hour...

 

[K7MDL]

If money is no object, I see there is a package at that link where they include the MorningStar Sunsaver Duo, it charges 2 battery in a priority you determine. Then you do not need to choose

 

[Kodachrome]

If money is no object, I see there is a package at that link where they include the MorningStar Sunsaver Duo, it charges 2 battery in a priority you determine. Then you do not need to choose


Yeah, but that still leaves the truck charging aspect. Besides, it is not MPPT and the terminals for the panel inputs are not very big, I have two sets of leads going into it.

Now, what if I want to have the option of running my DC camper needs like the fridge while driving when charging either battery via the truck? Sounds like another breaker switch...

 

[K7MDL]

...
Now, what if I want to have the option of running my DC camper needs like the fridge while driving when charging either battery via the truck? Sounds like another breaker switch...

The truck charging was taken into account in the last solution proposed. The battery switch will allow charging either or both batteries from the truck if it is running. I also assumed you will have a standard truck/camper battery isolator/relay installed. The DC panel and fridge are wired to the Diehard which is helped by solar (which should have a protection fuse anyway, but can be out of the way, and within several inches of the battery). So you can select the switch to the Diehard and all loads run off the truck when running, solar charged battery when not, Optima is isolated in standby. Flip the switch and the Optima gets charged by the truck, and the loads run off the solar+Diehard exclusively.

The fuse/breaker manipulation was only required for the odd case where you wanted to solar charge the Optima rather than the Diehard. In most cases I do not think you would bother though, just run the truck (or find AC) if things are that far gone.

Seems like this covers 99% of your needs stated. If not them might as well get matched 6V golf cart batteries.

 

[Kodachrome]

The truck charging was taken into account in the last solution proposed. The battery switch will allow charging either or both batteries from the truck if it is running. I also assumed you will have a standard truck/camper battery isolator/relay installed. The DC panel and fridge are wired to the Diehard which is helped by solar (which should have a protection fuse anyway, but can be out of the way, and within several inches of the battery). So you can select the switch to the Diehard and all loads run off the truck when running, solar charged battery when not, Optima is isolated in standby. Flip the switch and the Optima gets charged by the truck, and the loads run off the solar+Diehard exclusively.

The fuse/breaker manipulation was only required for the odd case where you wanted to solar charge the Optima rather than the Diehard. In most cases I do not think you would bother though, just run the truck (or find AC) if things are that far gone.

Seems like this covers 99% of your needs stated. If not them might as well get matched 6V golf cart batteries.



So I am going to get this up and running soon. Question though, will I be able to read the optima / backup battery on the camper water / battery gauge when the load is pulling off of that battery?

And how could I possibly have a separate gauge for the optima so I can check to see how full it is when it is getting juiced up by the truck?

 

[Kodachrome]

A BIG thanks to K7MDL for all the help, I got it wired today and it seems to be working fine. Now I can run two batteries if needed, if one craps out, I don't have to replace both since they are not in parallel. Found a nice & simple battery monitor for the Optima / Backup too:

http://www.ebay.co.uk/itm/ws/eBayISAPI.dll?ViewItem&item=150474037874&refid=store

Nothing like a little overkill...

 

[Gerdo]

It doesn't sound like the two camper batteries are tied, electrically, together. But... If you do have two different batteries (type, size, brand, and even down to different build lots) They will always have different charge states. These differences will cause the lower charged battery to "charge" it's self of the other battery. This will go back and forth between the two batteries causing both batteries to discharge.

 

[K7MDL]

A common strategy to deal with this is the ACR, automatic charging relay, or voltage sensing relay. It monitors the primary battery voltage and after it is reasonably charged and receiving excess charge source, then connects the secondary (aux, house) battery and it rises in voltage as it charges.

As along as the charge source is present, and at a higher voltage, the 2 batteries tied together are not really interacting (of any concern if they are healthy). So being tied together is mostly a concern for discharging batteries, or batteries at rest. The ACR solves that by separating them when the charge voltage goes away and battery voltage drops.


The solution used by Kodachrome only has the batteries separated as you guessed, but the "Both" switch position can be used to have one boost another. Not a scenario likely to be used. Having a manual overide on an ACR is handy to use the camper battery to boost your starter battery if you happen to leave your lights on and need a jump someday. No AC generator DC cable or jumper cables required.

 

[MakersTeleMark]

I've used my "both" setup coupled with my ACR 3 times in the last two weeks from being in a place where I couldn't plug in, and cycling the glow plugs was pulling a ton off of my 2 1000 ca batteries in the truck. When I "both it", I get my optima on board, which is charged by the solar panel, and she with the other 2 can fire those plugs no problem until I get that happy puff, cough, puff of smoke coming out of the exhaust.

Very handy indeed.