28 replies to this topic

[photohc]

I realize the majority of the members here would not normally go down this path, but I though it might be helpful if anyone ever wanted to venture out in the world of Lithium batteries, my experience might help. I've always been a geek and love playing with this stuff. This camper just gives me an excuse to spend money on my electronics/ham radio hobby.

 

I started out last year by replacing my two 75AH AGM batteries with a 100AH LiFePo battery. So you might ask, how can a 100AH lithium battery replace 150AH AGM (2x75AH) battery? A lead acid/AGM battery cannot tolerate a discharge any more than 50%, so the effective energy from a 150ah AGM is really 75ah. A lithium can easily handle a discharge down to 10% for a net energy availability of 90ah. My primary goal was to reduce the weight of the 2 AGMs with a 26# lithium battery.

 

At the time, I had a Morningstar Sunsaver MPPT controller and needed to figure out how I could adapt this lead acid charger to lithium charge profile. Lithium's do not need a float or equalization charge cycle. They essentially just charge to it's top voltage (14.2v) then stops until the charger measures/senses a drop in voltage to restart sending current to the battery. Lithiums, also require cell balancing, which is usually done via external device. At the time, I also became aware of a Kickstarter project by Dacian Toea, who created a charge controller and battery management system into a nice small package. He was creating this primarily for a household system, but it was equally deployable for a small camper/RV.

 

So, I got interested and he was embarking on creating a version 2 of his Solar Battery Management System (SBMS). I decided to wait for his new version and I found a way to program the Morningstar to mimic a lithium controller by changing the the charge parameters via a pc cable and program available on the Morningstar website.

 

Dacian took about a year to complete his Kickstarter and I just received his SBMS60 battery charger and management system. With the SBMS60, I am able to replace all this:

 

with this:

 

So, battery system now looks like this:

 

Another nice touch is the SBMS60 is able to connect via wifi to monitor the status of the battery and solar panels. 

 

I hope this maybe of interest to someone. If I can be of assistance, just pm me and I'll do what I can to help.  Cheers!

 

p.s. I guess I'll try and sell my old gear on the sell/exchange forum.

Edited by photohc, 08 April 2016 - 07:52 AM.

[Atlin]

I'm interested.  pm sent.

[billharr]

Nice job Harv. Some where down the line I can see this being the standard battery for campers. Do you see the cost of the Lithium batteries dropping in the future?

[photohc]

Bill, the Lithium battery I purchased is a 12v 100Ah, for $620. Some Lithiums being sold have fancy cell balancing and battery management systems that cost much more due to the electronics included to make the battery more friendly to standard chargers and look like a drop in replacement for a standard AGM Lead Acid. This one is a plain jane with just the battery.

 

I then added, the key to the system, an all-in-one battery management/monitor from a Kickstarter project by Dacian Todea for $250. This replaces a solar controller and Trimetric monitor. It ties together the solar panels, battery, and delivers the power to the camper at the sametime. It monitors power being generated by the solar panels, status of the battery, and consumption of the RV/Camper. You view the information on the built in color display or via WiFi. Another advantage is dropping the weight from 110#'s to 28#'s.

 

If you factor in two AGM 75Ah batteries at $200 ea., add a standard solar controller and the trimetric monitor, your not that far off from my $870 spent. Plus, the Lithium will last much longer than AGM's, probably by 3x's. (much debate on this due to it's newness)

 

I do think Lithiums will drop in price, but will depend in further chemistry improvement and general acceptance. I view the Lithium price like the LED light bulb. I remember going to Costco and buying a single 60w replacement for $15-20. Now you get a pack of 3 for the same amount.

 

Cheers, Harv

[dasadab]

Thanks for the excellent and helpful information.  Saving 70 lbs and simplifying things is a big plus.  If you factor in the cost of more frequent replacement of the AGMs, it seems like a cost effective OEM option that would be attractive.  

[Kodachrome]

I'll probably go this route once my AGM's are toast although they seem to be doing really well, I am responding to this message as a means to keep tabs on this thread. 

 

For reasons of staying & working in a super remote spot for weeks at a time, I run two entirely separate photo voltaic systems and would likely do the same with two 100AH LiFePO4 batteries. 

 

System One: This is the night time system as it consists of a 100AH AGM battery, Sunsaver MPPT 15 fed by 200W of flex panels in fixed flat position on the roof of the camper. It gobbles the sunlight during the day and works at night with an ample AH rating feeding the power needs. 

 

System Two: This is the day time system that consists of a 50W flex panel on the air dam that keeps the battery always topped and 200W of flex panels on the slide out / removable assembly under the cabover on the camper. It feeds a 55AH AGM via a Sunsaver 20L PWM charger. This works really well to take care of typically higher day time power requirements and keeps the battery topped even when pushing the system well past just running the AC/DC fridge. The fact that the panel assembly is removable makes it easy to soak up sunlight at pretty much any angle. 

 

Both these systems together pretty much make it to where I end the day with two full batteries but the fact they are really only half the AH count and weigh 121 pounds is reason enough for me to upgrade down the road. 

 

Thanks for posting and if you have any new info on how it is all working, I would love to hear it!

[photohc]

I've now have had the system installed with the new SBMS60 Lithium controller/Battery management system for about 2 mos. Took the rig out for a couple small trips. Generally the batteries will be around 75-80% of charge after a cool night. It depends if I have the heater on or not. I have a Waeco 80L 2 way refrigerator that draws 4-5 amps when running. Generally in fair weather, it cycles about 15 mins every hour (cold less, hot more). The majority of power draw is the refrigerator. My lights are all LED's and they consume very little.

 

These last two trips, in the mornings, it was overcast till about 11am. During that time, very little was going into the batteries. Once the sun showed up, the current input to the batteries jumped up to 12-14 amps (150w + 160w panels on roof). Usually, the batteries are back to 100% by 1pm.

 

I have since added the ability to charge from my alternator. I removed the Sure Power Separator and in it's place a manual connect switch that goes to one of the inputs on the charge controller (use to go direct to the battery). When connected, I get about 5 amps from the truck. I have replaced the factory wiring (#10 with #8). I'll need to play around with this more to better understand why I only get 5 amps. I haven't had to switch that on yet. I've only checked it out in idle and might get more in driving mode.

 

Cheers, Harv

Edited by photohc, 04 June 2016 - 06:07 PM.

[enelson]

Harv, what is the voltage difference between the truck and the battery voltage.  I have a SBMS100 (replaced SBMS4080).  The new units can take voltage from two separate inputs.  I've been guessing that there is diode isolation now with the two inputs.  This may drop 0.3V on the input voltage before it's used.  So if the input voltage is only, say, 0.3V above the battery voltage than the charge current will be very low or nothing.  

 

To get around the issue I've purchased, but haven't yet installed, a boost board to raise the truck voltage to something like the Max power point voltage on a solar panel, around 17V.  I've noticed the same issue and am charging just a couple of amps, or less, from the truck when it should be something like 8A.  I don't really even need the truck voltage when the solar is pumping the battery back to 100% easily in the morning.  Winter is another story though.

Edited by enelson, 08 June 2016 - 10:09 PM.

[photohc]

Thanks for the feedback Eric. Yes, Dacian did indicate the isolation diodes on the inputs. I'm using PV1 for the panels and PV2 is on a switch to allow using either my converter (IOTA), when AC is available or alternator. Like you, I'm finding the batteries are back up to 100% usually by noon so I haven't had to think about using the alternator or AC. I have the SBMS60 installed in mine.

 

We're thinking alike, I purchased a cheap buck-boost converter off eBay and will be experimenting with it. I had set it to 14.2 volts but I may need to take it higher. Let me know what results you get.

 

My camper is currently off the truck, so I will need to wait till the next time I put it back on for a trip to experiment.

[enelson]

The switch is a good idea with the IOTA.  I had just disconnected and removed the charger from my Progressive Dynamics system and used a surplus notebook charger to provide "shore" power through the camper 7 pin cable.  The only AC in the camper was from my inverter in this set up.  In the future I'd like to replace the input AC plug with a GFCI outlet to bring inverter power to the outside of the camper.