Sprinter-Forum    
 

Go Back   Sprinter-Forum > Sprinter-Based RV's & Conversions > Sprinter-Based RV Brands > Leisure Travel Vans > Unity


 
Thread Tools Display Modes
Old 07-14-2015, 12:35 PM   #1
Peter Tourin
2012 LTV Unity MB
 
Peter Tourin's Avatar
 
Join Date: Oct 2013
Location: Jericho Center, VT
Posts: 1,981
Thanks: 824
Thanked 780 Times in 500 Posts
Default Replacing OEM batteries with LiFePO4's

My OEM batteries are now toast, and I'm replacing them with SmartBattery SB100's - BCI27 size, 100 AH, 28# each. Installation will be simple since they're slightly smaller than the SRM-27's and have bolt terminals. Charging won't be quite so simple, and I need to replace the 55A charger section in my power center. About time - the power center is a Parallax 7355, which doesn't have a great charger.

I don't know of any drop-in replacement charger that'll charge LiFePO4's. At the moment I'm looking at Progressive Dynamics' 9100L series - they're straight 14.6v chargers designed for lithium batteries - voltage is adjustable, and in any event the batteries want 14.4-14.6. They make several sizes including 60A (input rated 1000W), 70A (1250W) and 80A (1300W). I'd like to install a 70A or 80A charger since the batteries can easily handle the higher charge rate, but the RV has a 30A service.
QUESTION: do I run into problems if I install a larger charger?

The big items are obvious:
Microwave - 1500W convection, 1150 normal (12.5, 9.6A)
AC - 1500W compressor rated load (12.5A)
Charger - 1000, 1250 or 1300W (8.3, 10.5 or 10.9A)


I'd never think of running both microwave and A/C simultaneously (even with the 60W charger I'd be over 30 amps if I ran all 3). So I'm inclined to install either the 70W or the 80W charger. Am I missing anything here? I think some of you have better electric design credentials than I do!

There are 2 drawbacks to the 80W charger - it's physically bigger and it requires a 20A breaker instead of my existing 15A breaker. Both of those issues seem manageable, but the easiest compromise seems to be the 70A charger.

One oddity I saw during my reading: The Dometic site lists specs for the 651815 Penquin II heat pump, and they say the minimum generator size is 3.5 kw. Interesting, given our 2.8 kw units...........
__________________
Peter Tourin
2012 Leisure Travel Unity MB

Last edited by Peter Tourin; 07-14-2015 at 01:09 PM.
Peter Tourin is offline   Reply With Quote
Old 07-14-2015, 03:29 PM   #2
nwboater
 
nwboater's Avatar
 
Join Date: Feb 2014
Location: Whidbey Island. WA
Posts: 220
Thanks: 185
Thanked 108 Times in 71 Posts
Default Re: Replacing OEM batteries with LiFePO4's

Peter, switching to AGM batteries is smart. The battery charger has nothing to do with powering the microwave or anything else electrical in your couch. It only charges the battery. Since the Unity has a single 12v battery with a capacity of 220 Ah, and most charging occurs at lower amperage, a 4 stage regulated charger producing 50-75 amps is more than adequate. Check out the IOTA IQ4 Smart Charger (55A).
__________________
NWBoater / Whidbey Island WA
2014 UnityTB
Willard 40' trawler
nwboater is offline   Reply With Quote
The Following User Says Thank You to nwboater For This Useful Post:
jackfish (07-14-2015)
Old 07-14-2015, 03:49 PM   #3
jackfish
 
Join Date: Nov 2011
Location: Rural Halsey, Oregon
Posts: 1,757
Thanks: 360
Thanked 829 Times in 571 Posts
Default Re: Replacing OEM batteries with LiFePO4's

Instead of looking at a new charger to replace the converter, why not get a Magnum inverter/charger which has a fully adjustable charging profile. Then you could use microwave sans shore power.
__________________
You learn something every day whether you want to or not.

Last edited by jackfish; 07-14-2015 at 03:58 PM.
jackfish is offline   Reply With Quote
Old 07-14-2015, 03:55 PM   #4
jackfish
 
Join Date: Nov 2011
Location: Rural Halsey, Oregon
Posts: 1,757
Thanks: 360
Thanked 829 Times in 571 Posts
Default Re: Replacing OEM batteries with LiFePO4's

Quote:
Originally Posted by nwboater View Post
Since the Unity has a single 12v battery with a capacity of 220 AH...
It does?
__________________
You learn something every day whether you want to or not.
jackfish is offline   Reply With Quote
Old 07-14-2015, 04:17 PM   #5
Peter Tourin
2012 LTV Unity MB
 
Peter Tourin's Avatar
 
Join Date: Oct 2013
Location: Jericho Center, VT
Posts: 1,981
Thanks: 824
Thanked 780 Times in 500 Posts
Default Re: Replacing OEM batteries with LiFePO4's

The catch is that I'm getting lithium ferric batteries, not AGM's. I can't use the Iota or similar chargers because the lith batteries want 14.4-14.6 volts until the reach a certain voltage, and that's it. So I have limited choices for chargers.

I guess I didn't make it clear - but lith batteries can be charged at high rates - a 200 AH battery bank will easily accept an 80A charger - and it would be nice to have the ability to plug into shore power and charge the batteries quickly quickly. So it's appealing to have a high-capacity charger, but I have to stay within the limits of my 30A service. That's what I'm trying to figure out. For example, suppose I install that Progressive Dynamics 80A charger. Let's say I've run my batteries pretty far down - I plug into shore power and the charger is working away and drawing 10.9A. Now the air conditioner comes on. I'm not sure how much it draws when the compressor first comes on, but I don't want to install a charger that causes my main breaker to trip every time my A/C fires up.... It's the A/C that confuses me - I don't know how they behave and how much short-term load they put on the system each time the compressor kicks in.

BTW - my MB has 2 batteries - the OEM batteries were Interstate flooded cell batteries that each were about 95 AH - so I had around 190 AH, and I always tried to keep them more than half charges, so I figured I had around 90 AH available capacity. The lithium batteries don't get damaged as much by deep discharge, so I can use more of their rated capacity without shortening their life much - I'm expecting I'll have about 160 AH capacity from the 200 AH lith battery bank, maybe even 180 AH capacity. How lith batteries behave is another story - I won't get into a rant about that here. But you can see why they're appealing:
1. My 200 AH battery bank gives me about double the useful capacity that a 200 AH standard or AGM battery bank would give me - twice as much boondocking before I have to recharge.
2. The lith batteries weigh 28 lbs each - my Interstates weighed 58 and FullRiver AGM's would weigh over 70 each. I want more cargo capacity, not heavier batteries.
3. The lith batteries life span should be MUCH longer than any standard or AGM battery. Their rated life cycles at 50% discharge would be anywhere from 250 to maybe 900 cycles. Lith batteries are rated 2000 cycles. But the definition of lifespan is different. For flooded cells, end of life is when the battery has deteriorated down to 50% capacity - that is, when a battery rated 100 AH only has 50 AH capacity left. For lith batteries, end of life is when the battery is down to 80% capacity. So if I try to calculate the lith battery lifespan the same way as they do for flooded cell batteries, they're around 4000 cycles - so to 5 to 16 times the lifespan.

BUT - you pay for those advantages. The batteries cost $1300 instead of $250-300 for a good quality AGM battery.

End of rant....
__________________
Peter Tourin
2012 Leisure Travel Unity MB
Peter Tourin is offline   Reply With Quote
Old 07-14-2015, 04:26 PM   #6
OrioN
2008 2500 170" EXT
 
OrioN's Avatar
 
Join Date: Sep 2007
Location: Vancouver, BC
Posts: 7,932
Thanks: 483
Thanked 1,914 Times in 1,413 Posts
Default Re: Replacing OEM batteries with LiFePO4's

Quote:
Originally Posted by Peter Tourin View Post
The catch is that I'm getting lithium ferric batteries, not AGM's. I can't use the Iota or similar chargers because the lith batteries want 14.4-14.6 volts until the reach a certain voltage, and that's it. So I have limited choices for chargers.
Incorrect.

That is a maximum charge voltage. They will charge more than adequately with voltages below that and even down to 13.8V.





.
OrioN is offline   Reply With Quote
Old 07-14-2015, 05:10 PM   #7
Peter Tourin
2012 LTV Unity MB
 
Peter Tourin's Avatar
 
Join Date: Oct 2013
Location: Jericho Center, VT
Posts: 1,981
Thanks: 824
Thanked 780 Times in 500 Posts
Default Re: Replacing OEM batteries with LiFePO4's

That's confusing, as their spec sheet says "Charge voltage 14.4V - 14.6V" - no mention of maximum. If I charge with a lower charge voltage, will they charge to 100% but just slower? Or will they not fully charge? Also, I understood that they didn't want a float charge - they wanted the charger to simply stop charging when they reached a certain voltage. So I understood that I couldn't use a multi-mode charger like I would for a flooded cell battery bank. I'm trying to reach them now to ask exactly what they expect for good charging.
__________________
Peter Tourin
2012 Leisure Travel Unity MB
Peter Tourin is offline   Reply With Quote
Old 07-14-2015, 06:01 PM   #8
Custommm
 
Custommm's Avatar
 
Join Date: Jun 2012
Location: Canada
Posts: 349
Thanks: 314
Thanked 102 Times in 61 Posts
Default Re: Replacing OEM batteries with LiFePO4's

Peter ,Im VERY interested as well... It's also seem that LiFePO4 or those with Mg requires more careful monitoring of each cell during charge and a good temperature management to archive their expected lifespan (just like a smartphone)
I would love to swap my interstate batteries in my MB as well but it's seem that we are more or less in R&D.
Keep posting your finding!
__________________
LTV Unity Murply Bed 2014 Silver
Custommm is offline   Reply With Quote
Old 07-14-2015, 08:06 PM   #9
Don Horner
2012 Unity IB
 
Don Horner's Avatar
 
Join Date: Oct 2006
Location: Okeechobee, FL
Posts: 692
Thanks: 11
Thanked 405 Times in 204 Posts
Default Re: Replacing OEM batteries with LiFePO4's

Peter, same advice I give to everyone when the subject of charger/converters and inverters is raised. Talk to Randy at bestconverter.com. Click here to see his page about Lithium Ion charger/converters...
__________________
...Don
Don Horner is offline   Reply With Quote
Old 07-14-2015, 08:57 PM   #10
smiller
2008 View J (NCV3 3500)
 
Join Date: Nov 2013
Location: North Carolina
Posts: 4,043
Thanks: 450
Thanked 2,740 Times in 1,656 Posts
Default Re: Replacing OEM batteries with LiFePO4's

Quote:
Originally Posted by Don Horner View Post
Peter, same advice I give to everyone when the subject of charger/converters and inverters is raised. Talk to Randy at bestconverter.com. Click here to see his page about Lithium Ion charger/converters...
Interesting, from the brochure/manual it seems that their line of lithium battery chargers are basically just a fixed voltage supply and the local battery BMS takes care of the actual charging regimen. If I understand that correctly than any high quality fixed voltage charger should work, such as the Iota DLS series, etc.
smiller is offline   Reply With Quote

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



All times are GMT. The time now is 11:38 AM.


Powered by vBulletin® Version 3.8.9
Copyright ©2000 - 2018, vBulletin Solutions, Inc.