Mobile Office 12 AC

[Buzz68]

I'm a surveyor that works for a land developing company. We have had an mobile offices since 1997 and all of them have been powered by a Honda 3000iu generator. In 2019 we purchased a new Sprinter 4x4 and was ready to build. I had a hard time finding someone to do the build. When we did, for power they suggested we go with lithium batteries.This was the first time dealing with lithium battery bank. They would be charged by solar and the vans alternator. So I had this Gucci $$$$ upfitter do everything. They also installed a Pro Air 12 volt AC unit. I would like to have your opion on my system and its longevity. If you would do this? I wanted to give you how we use it. We live in Maryland and during June, July & August or any day that it gets above 75 the AC is used. I will run them down to 20% and on the really hot days if nessary we will run the van to help. During the colder part of the year, I'm only using maybe 10% of the battery bank. Did they make a great and long lasting choice?

 

[gnubie]

You've spec'd good quality devices with Victron and LG so you can pretty much remove them from question because with those names you get both reliability and long life.

That leaves the battery. If you get reasonable quality batteries and treat them properly you can expect in the order of 2000 full charge / discharge cycles. They don't then die, they have just fallen to 80% of their original capacity. You can continue to use them for years and years after that so long as they still store enough energy to do what you need. It's important to keep an eye on the battery temperature as you can run into problems with both high and low temperatures so attention to their enclosure is needed. A decent battery will have a BMS on board that is aware of the temperature and will step in to protect the cells if something gets out of spec.

 

[Buzz68]

Yep, I used six 100ah Battle Born batteries and the compartment is climate controlled. I was concerned for about 1/3 of the year only a 10% parcel discharge. This is during the colder months when I don't use the AC unit and only use 8-10% daily. How will that effect the amount of discharge cycles? Thank you for taking the time to respond.

 

[gnubie]

Shallow discharges over 4 months won't cause you any problems at all.

 

[FilterGuy]

It looks like your alternator charges the batteries directly..... That would concern me. The alternator voltage is likely to be too high for charging the Battle Born. I would put a DC-DC charger in place of that relay on the left of the diagram Since everything else is Victron, the Victron DC-DC charger is a logical choice, but they are pricey. Will likes the renogy:

Also, do you know what the relay on the middle right of the diagram does?

 

[FilterGuy]

Edited to correct a false statement. (Sorry) Also, I looked up the settings on the inverter and they are somewhat limited. Make sure they are set for AGM charging. That will be the best setting for your Battle Born.
The multi-plus inverter can be configured with the VE connect Software and a coms addapter. Make sure you select lithium for your battery type in the settings.

 

[gnubie]

From the horse's mouth. As always keep the firmware on things up to date to receive the latest features etc. Victron doesn't sit on its Laureltecs

 

[SolarRat]

The alternator voltage is likely to be too high for charging the Battle Born

And the alternator won't last long without the dc-dc charger....

Otherwise, nice system!

 

[Buzz68]

You know the saying " It's Greek to me ". Could someone explain my system to me why the battery monitor ( BMV-702 ) doesn't indicate any solar power ( Aux ) and I mean zero. The person that set up this system, told me that they had a difficult time. Don't know why that would be. I didn't think this was experimental, at least I hope not. The Up Fitter keep me in the dark and I guess he thought I was going to steal his secrets. The system has worked fine and I have had no problems. ( Knock on wood ) I was told that they had this same system running for 6 years and it and being used everyday. I get it, lots of variables in the equation. I do hope I get a least 10 years with the 20% loss.

 

[SolarRat]

Could someone explain my system to me why the battery monitor ( BMV-702 ) doesn't indicate any solar power ( Aux ) and I mean zero.

In the diagram, there's a fuse symbol near the negative battery terminal. I assume that should be a shunt symbol. The details of how it's hooked to the monitor are not clear so a pic of the shunt would be needed...to start.

 

[Buzz68]

That was a crappy picture from my phone. This is a scan from the original doc. I hope this is clear and it's not the diagram it self. Also my 2nd alternator runs to some type of a CPU before it leaves the engine compartment & enters the power system. Don't know if it's the flux capacitor or not!

 

[FilterGuy]

Also my 2nd alternator runs to some type of a CPU before it leaves the engine compartment & enters the power system. Don't know if it's the flux capacitor or not!

I was going to ask if you had a flux capacitor... but I normally only see them on Deloreans!

OK....I didn't realize they put in a 2nd alternator. That's not unheard of but a bit unusual for a system this size. The CPU thingy is an external voltage regulator. In the original picture I saw MC-614H and looked it up and it is a Balmar external regulator for the alternator. Depending on how it is set up you might be fine. I would have to do some digging to find out if it can be set for a lithium friendly charge profile.

 

[Buzz68]

If your still listening, does Battle Born Batteries hove low voltage cut-off? Will it shut down before any damage?

 

[FilterGuy]

If your still listening, does Battle Born Batteries hove low voltage cut-off? Will it shut down before any damage?

Yes and Yes

 

[Buzz68]

You the man, thank you!!!!!