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Author Topic: Lithium Batteries, how many aH?  (Read 480 times)

ebaierl

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Lithium Batteries, how many aH?
« on: November 26, 2017, 04:53:54 PM »
I have an opportunity to get some LiFePO4 batteries for our RV. But I'm not sure how many amp-hours I should get. I don't have solar panels yet, and we have so far been on shore power most of the time, but we want to change that.

For power consumption DC, we have the fridge+propane, the water pump, the interior lights (not LED yet, but will be soon), a car stereo, a mobley, a small stick PC, and we'll be adding some USB outlets direct from the breaker box to power cell phones and small electronics.

For AC we have two TVs with Apple TVs, though only one is used at a time, an ethernet switch and router, a cell signal booster, once a day use of coffee maker and microwave, sometime use of a crockpot, and charging our laptops.

We are currently in an area that is getting cold at night, so we use an electric heater, but if we are boondocking, we shouldn't be anywhere that needs that or AC.

Thats really about it. The stick PC might be replaced with a slightly larger PC, but still not a big tower. Once in awhile we'll have an Xbox 360 running, but that's not every day.

I think I can get a 300aH battery, but I'm not sure at this point. I don't know if that would be enough though, even if only discharging to 10%, it would still be 270aH. Whatever size battery we get, we'll get enough solar panels to charge it though, but this is being done a little at a time.

Any thoughts?

Paul & Ann

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Re: Lithium Batteries, how many aH?
« Reply #1 on: November 26, 2017, 04:59:10 PM »
300 amp hours of battery power sounds about right to me.
Paul & Ann  Iowa
2005 Winnebago Voyage 38J
http://stoughrvadventure.blogspot.com/

Gary RV_Wizard

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Re: Lithium Batteries, how many aH?
« Reply #2 on: November 26, 2017, 07:41:43 PM »
Based on what you describe, 300 AH may be adequate. However, I would err on the side of caution and get 350-400 AH if I could (and the space and weight capacity were available for it). My rationale is that people who haven't actually monitored their daily power consumption are often surprised when they do so. Determining your power budget (amp-hours per day) is the first and most important step in setting up a battery-powered system, whether re-charging by solar, wind or generator
Gary
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Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

AStravelers

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Re: Lithium Batteries, how many aH?
« Reply #3 on: November 27, 2017, 07:47:56 AM »
Your once a day use of coffee maker is fine, however running a crockpot for 6-10 hours uses a lot of power.  Might be OK with solar on a bright sunny day.  Also using the microwave to heat things or baking a couple of potatoes is fine.  However if you are going to cook something and run the microwave for 30 minutes or so that uses far to much of your batteries.  Or trying to use a convection part of the microwave uses a huge amount of power.

Al & Sharon
2006 Winnebago Sightseer 29R
2009 Chevy Colorado 4X4

http://downtheroadaroundthebend.blogspot.com/

AStravelers

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Re: Lithium Batteries, how many aH?
« Reply #4 on: November 27, 2017, 08:02:15 AM »
The very first thing you need is a battery monitor, such as a Trimetric:  http://www.bogartengineering.com/products/trimetrics.html  If you have a magnum inverter, magnum has a monitor which integrates with the magnum remote panel.

The battery monitor provides you with a running total of battery amp hours used or replaced.  The monitor also will display the current number of amps being discharged or charged as well as the voltage of your batteries.   

If you don't have the monitor you are flying blind as far as the capacity of your battery. 

Al & Sharon
2006 Winnebago Sightseer 29R
2009 Chevy Colorado 4X4

http://downtheroadaroundthebend.blogspot.com/

AStravelers

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Re: Lithium Batteries, how many aH?
« Reply #5 on: November 27, 2017, 08:14:59 AM »
I recommend the 400AH over the 300Ah.  Weight and space wise there isn't a huge difference and price isn't greatly different.  Lithium is expensive no matter what you buy. 

I have 400Ah of lithium and 650 watts of solar and can go almost indefinitely w/o shore power or generator. 

You mention of discharging down to 10% SOC.  I really don't like going that low even though the sellers advertise that.  I prefer to go no lower than about 75%.  It just puts less stress on the battery.   I look at it from the point of, I could drive my car or RV by stomping on the accelerator and getting to speed as fast as possible then waiting to last minute to slam on the brakes to stop.  Puts more wear and tear on the vehicle. 

The other concern is going to 10% puts in the area where lithium has a really steep and extremely quick drop to total discharge which will ruin your battery.  Even if you have a BMS to keep from total discharge, once the BMS disconnects your battery you no longer have 12V to operate your fridge or lights.  (even on gas or 120V elect the fridge requires 12V for the control panel)
Al & Sharon
2006 Winnebago Sightseer 29R
2009 Chevy Colorado 4X4

http://downtheroadaroundthebend.blogspot.com/

Gizmo

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Re: Lithium Batteries, how many aH?
« Reply #6 on: November 27, 2017, 08:44:10 AM »
You may be surprised that you may get away with less Ah with Lithium over LA or AGM batteries, by virtue of the fact that with Lithium, they can be safely discharged to 10-20% before recharging and they charge at a faster rate as well.  The standard lead acid or AGM the threshold is about 50%, so that is huge.  Regardless though you really need to do an energy audit to determine your energy consumption to get a battery bank and solar capacity that will work for you.  In our boondocking experience, we got along nicely with 225AH (2-6V LA batteries).  In our planning to go fulltime I looked at our potential energy consumption and determined if we were to go the LA or AGM route we would need 400-450Ah, but with Lithium batteries we likely would do well with 300Ah which we purchased and installed.  We will begin our fulltime journey in January, so we have not had the "real world" results yet, but so far in our test runs the 300Ah Lithium, it looks like 300 Lithium will be spot on for us.
Regards, Bruce, Lin An, Kenji & Suki
2017 Eagle Cap 1165 Truck Camper With Tork Lift Fast Gun Tie Downs & T.L. Wobble Stoppers
2015 Ram Big Horn 3500 CC Cummins TD Dually 3:73 Gears & AISIN Tranny
Gone But not forgotten:
2014 Northwoods Snow River 246RKS &
2013 Aliner Expedition

Gary RV_Wizard

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Re: Lithium Batteries, how many aH?
« Reply #7 on: November 27, 2017, 09:16:09 AM »
Quote
I recommend the 400AH over the 300Ah.  Weight and space wise there isn't a huge difference and price isn't greatly different.  Lithium is expensive no matter what you buy. 

The low weight of a LiFePO4 battery vs lead-acid is a big plus. A typical 100 AH LiFePO5 is around 30 lbs, so about half an equivalent LA.

Price, though, seems to me like a major consideration. An additional 100 AH appears to add $900 or more to the already steep price tag.

The enhanced ability to deep discharge (down to 10-20%) gives the LI battery more flexibility if your typical load is moderate but you have occasional larger needs. You can get away with occasional ultra-deep discharges with LI, but after a couple such episodes a lead acid (including AGM) will have noticeably lost some AH capacity.
Gary
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Gary Brinck
Summers: Black Mountain, NC
Home: Ocala National Forest, FL

Lou Schneider

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Re: Lithium Batteries, how many aH?
« Reply #8 on: November 27, 2017, 11:41:29 AM »
Another way at looking at LiFe's deep discharge capabilities is a lead acid battery has a built-in reserve for true emergencies.  If you design the system so your normal usage only discharges the battery to the recommended 50% level, you still have power left to cover the unexpected, like when you're caught in a storm (no solar charging) and the generator won't start.

If you design your LiFe system so you normzlly use it's full capacity, there's no emergency reserve.  Once the battery is empty, it's empty.
« Last Edit: November 27, 2017, 11:47:11 AM by Lou Schneider »

Gizmo

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Re: Lithium Batteries, how many aH?
« Reply #9 on: November 27, 2017, 11:50:19 AM »
Another way at looking at LiFe's deep discharge capabilities is a lead acid battery has a built-in reserve for true emergencies.  If you design the system so your normal usage only discharges the battery to the recommended 50% level, you still have power left to cover the unexpected, like when you're caught in a storm (no solar charging) and the generator won't start.

If you design your LiFe system to take advantage of it's repeated deep discharge ability, there's no reserve left.  Once the battery is empty, It's empty.

True enough, however while the very occasional drop below the 50% threshold with LA & AGM's will not significantly affect the batteries life, repeated drops below will.  In my research on Lithium, it seems the prevailing wisdom is to use the 20% threshold rather than 10% to allow for some reserve.
Regards, Bruce, Lin An, Kenji & Suki
2017 Eagle Cap 1165 Truck Camper With Tork Lift Fast Gun Tie Downs & T.L. Wobble Stoppers
2015 Ram Big Horn 3500 CC Cummins TD Dually 3:73 Gears & AISIN Tranny
Gone But not forgotten:
2014 Northwoods Snow River 246RKS &
2013 Aliner Expedition

Kevin Means

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Re: Lithium Batteries, how many aH?
« Reply #10 on: November 27, 2017, 02:39:48 PM »
True enough, however while the very occasional drop below the 50% threshold with LA & AGM's will not significantly affect the batteries life, repeated drops below will.  In my research on Lithium, it seems the prevailing wisdom is to use the 20% threshold rather than 10% to allow for some reserve.
Yep, that's definitely one of the benefits of LI batteries - constant current as they're drawn down to a much lower SOC than lead/acid batteries - and without damaging them. That factor alone can reduce the AH capacity we need to meet our usage needs.

Kev
2011 Winnebago Tour 42QD
Towing a Jeep Rubicon Unlimited LJ or an Acura MDX
RVI Brake 2, Minder TM-66 TPMS, 970 watts of solar
(Can't wait to spend more time RVing)
Lakeside, California

Frank B

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Re: Lithium Batteries, how many aH?
« Reply #11 on: December 25, 2017, 06:30:28 AM »
FWIW, I came across this link for a 200 AH Lithium battery.  It is sold by Starlight Solar in Yuma AZ, and it is my understanding that they are a reputable dealer.


https://www.ebay.com/i/122654243000?chn=ps


Our 6 golf cart batteries were getting tired this year, and we looked at Lithium this time, including the one linked above, which is lower in price than what we have seen so far.  Chickened out and bought 6 more GC-2's, however.


Frank.
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John From Detroit

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Re: Lithium Batteries, how many aH?
« Reply #12 on: December 25, 2017, 08:07:19 AM »
I was looking for an ad for Li batteries yesterday. like 2200 dollars to replace a pair of GC-2's amp hour wise.. I'll pass.
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Gizmo

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Re: Lithium Batteries, how many aH?
« Reply #13 on: December 26, 2017, 08:34:49 AM »
We just bought 3-100ah Battle Borne batteries for $2,700.00 with free shipping.  A very good price as these babies can get hysterically expensive, if we were not going fulltime come January and only recreationally using our rig, I likely would not make  the investment.  Considering our full-timing will be mostly boondocking and considering the expected life span is considerably longer it was worth the investment for us.  The only negative to these I can see is the initial price.
Regards, Bruce, Lin An, Kenji & Suki
2017 Eagle Cap 1165 Truck Camper With Tork Lift Fast Gun Tie Downs & T.L. Wobble Stoppers
2015 Ram Big Horn 3500 CC Cummins TD Dually 3:73 Gears & AISIN Tranny
Gone But not forgotten:
2014 Northwoods Snow River 246RKS &
2013 Aliner Expedition

QZ

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Re: Lithium Batteries, how many aH?
« Reply #14 on: December 26, 2017, 09:05:19 AM »
If you are able to spend for lithium I'd surely first get a battery monitor and see what real life energy use values are. You will continue to use it when you are done, it will be part of your energy management system. Monitors usually also give you some charge history data which isnt critical but can be helpful.  If you dont want to do that then at least get a killawatt or something. I agree with what was said about crock pots etc. I  haven't researched or even considered lith so I dont know about going down to 10 % but I'd look at it more from the point of can I run for more than one day. If you size it to X amount so as to make it overnight  and something happens in a particular night you still have the ability to make it until morning without starting a generator at 3 am.  I agree with the thought of not flat pedaling any electrical component but again I cant comment on 10%. I like to keep the load well below max on any component.
« Last Edit: December 26, 2017, 09:13:33 AM by QZ »

Gizmo

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Re: Lithium Batteries, how many aH?
« Reply #15 on: December 26, 2017, 09:51:40 AM »
I do have a very good battery monitor and was using it with the AGM's that came with my rig upon purchase, in fact the first accessory I have installed on all my rigs.  Regardless of what batteries one chooses, for anyone who boondocks regularly, a good battery monitor is a must IMHO. 
Regards, Bruce, Lin An, Kenji & Suki
2017 Eagle Cap 1165 Truck Camper With Tork Lift Fast Gun Tie Downs & T.L. Wobble Stoppers
2015 Ram Big Horn 3500 CC Cummins TD Dually 3:73 Gears & AISIN Tranny
Gone But not forgotten:
2014 Northwoods Snow River 246RKS &
2013 Aliner Expedition

Frank B

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Re: Lithium Batteries, how many aH?
« Reply #16 on: December 26, 2017, 10:24:42 AM »
Gizmo:


Do let us know how that works for you. I too am attracted by the performance of lithium batteries and their longer life expectancy.  I went with six Costco golf cart batteries again this time, however. We don't full time, so just couldn't quite justify the added cost at this point.
Linux:  Free, open, elegant.
06 GMC 3500 Duramax crew/long pulling 2010 Arctic Fox 30U with 1700 lb Reese Titan Class 5.
1.2 kw solar

Gizmo

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Re: Lithium Batteries, how many aH?
« Reply #17 on: December 26, 2017, 02:23:14 PM »
Gizmo:


Do let us know how that works for you. I too am attracted by the performance of lithium batteries and their longer life expectancy.  I went with six Costco golf cart batteries again this time, however. We don't full time, so just couldn't quite justify the added cost at this point.

I sure will Frank.
Regards, Bruce, Lin An, Kenji & Suki
2017 Eagle Cap 1165 Truck Camper With Tork Lift Fast Gun Tie Downs & T.L. Wobble Stoppers
2015 Ram Big Horn 3500 CC Cummins TD Dually 3:73 Gears & AISIN Tranny
Gone But not forgotten:
2014 Northwoods Snow River 246RKS &
2013 Aliner Expedition

AStravelers

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Re: Lithium Batteries, how many aH?
« Reply #18 on: December 26, 2017, 05:33:39 PM »
FWIW, I came across this link for a 200 AH Lithium battery.  It is sold by Starlight Solar in Yuma AZ, and it is my understanding that they are a reputable dealer.


https://www.ebay.com/i/122654243000?chn=ps


Our 6 golf cart batteries were getting tired this year, and we looked at Lithium this time, including the one linked above, which is lower in price than what we have seen so far.  Chickened out and bought 6 more GC-2's, however.


Frank.
Starlight Solar is considered a reputable dealer.  I bought my 400AH lithium battery kit from them in Jan 2016 and have been happy with it and the support from the owner. 

However before buying the battery you see on Ebay, you should go to Starlight Solar's website here:  http://www.starlightsolar.com/elite-power-solutions-lfmp-battery/about-lfmp-packages.html  and review all the separate parts of the battery kit/package and compare that to what you see on Ebay.  Also give Starlight a call about what they are offering on Ebay.

It "appears" to me that what is for sale on Ebay is only the battery.  No battery monitor system.  Also I am not sure if the interconnecting bus bars are included in the Ebay listing. 

Also note that the battery monitor is shown as "optional" on the Ebay details page. 

Now, what I like about the Elite Power Solutions battery, WITH the monitor package from Starlight Solar.
--  An excellent monitor system which shows the exact details of every battery cell in the battery.
--  The temperature of every cell
--  the Voltage of every cell
--  A video monitor you mount inside the RV to see the information supplied by the monitor systme

It is not always clear to me what you get from some of the "drop in" batteries that "claim" you can just drop them into your existing system and chargers not be concerned about your charging parameters. 

Al & Sharon
2006 Winnebago Sightseer 29R
2009 Chevy Colorado 4X4

http://downtheroadaroundthebend.blogspot.com/

AStravelers

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Re: Lithium Batteries, how many aH?
« Reply #19 on: December 26, 2017, 05:48:37 PM »
I was looking for an ad for Li batteries yesterday. like 2200 dollars to replace a pair of GC-2's amp hour wise.. I'll pass.
Since a single 100Ah lithium battery will replace a pair of GC-2 batteries and give you 2-3 times the life of the GC-2 batteries, I believe you are way off on your price comparison. 

Here is a single 100Ah Lithium for $950 with free shipping:  https://www.solar-electric.com/battle-born-bb10012-100ah-12v-lithium-battery.html?gclid=Cj0KCQiAg4jSBRCsARIsAB9ooavfBeABnwSam5uOH3sRr8UbmWXCezIk1krgj1l-6O5t77irS9nGPckaAtOBEALw_wcB  from a reputable dealer.

However if a person only dry camps or boondocks several days a year, lithium is not worth the investment.
Al & Sharon
2006 Winnebago Sightseer 29R
2009 Chevy Colorado 4X4

http://downtheroadaroundthebend.blogspot.com/

 

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