RV.Net Open Roads Forum: Tech Issues: Lithium batteries and new solar charger

RV Blog

  |  

RV Sales

  |  

Campgrounds

  |  

RV Parks

  |  

RV Club

  |  

RV Buyers Guide

  |  

Roadside Assistance

  |  

Extended Service Plan

  |  

RV Travel Assistance

  |  

RV Credit Card

  |  

RV Loans

Open Roads Forum Already a member? Login here.   If not, Register Today!  |  Help

Newest  |  Active  |  Popular  |  RVing FAQ Forum Rules  |  Forum Posting Help and Support  |  Contact  

Search:   Advanced Search

Search only in Tech Issues

Open Roads Forum  >  Tech Issues

 > Lithium batteries and new solar charger

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 
Page of 8  
Prev  |  Next
Sponsored By:
Slownsy

USA

Senior Member

Joined: 01/16/2011

View Profile



Good Sam RV Club Member

Offline
Posted: 03/22/21 01:45am Link  |  Quote  |  Print  |  Notify Moderator

BLF13 the batteries are rated at 1.28 KWhr each. Yes thanks for reminder re PWM .
Almot currently 4/150V Renogy panels, and yes maybe will still go for 2 or more and MPPT controller. Yes sun is less in summer, but vi will head op north a bit.
Frank.


Frank
2012 F250 XLT
4x4 Super Cab
8' Tray 6.2lt, 3.7 Diff.

phemens

Montreal, Canada

Senior Member

Joined: 09/18/2006

View Profile


Offline
Posted: 03/22/21 07:34am Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:

Your two 100 LFP will actually have 80 usable each so 160 not 200 to compare with the 260. (you don't normally go below about 20% DOD)

Your controller is a 12/24 but being PWM that only means 24 if the batteries are also 24. To go 24 panel and 12 battery, you must have an MPPT with its buck converter that PWMs don't have.


Depends on whether the batteries are 'true' AH or not. The last LiFePo4 battery I bought was rated as usable 100AH, so in reality 120AH.


2012 Dutchman Denali 324LBS behind a 2006 Ford F-250 V10 out of Montreal
1 DW, 1 DD, 1 DS, 2 HD (Hyper Dogs)
1200w solar, 600AH LIFePO4, Yamaha EF2000 gen, Samlex 3000w Inverter

StirCrazy

Kamloops, BC, Canada

Senior Member

Joined: 07/16/2003

View Profile



Posted: 03/22/21 07:40am Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:

Your two 100 LFP will actually have 80 usable each so 160 not 200 to compare with the 260. (you don't normally go below about 20% DOD)



I dont know of any comercially made LFP battery that isn't set up for 100% of advertised AH use, so he will have 200 usable AH.

Steve


2014 F350 6.7 Platinum
2016 Cougar 330RBK

BFL13

Victoria, BC

Senior Member

Joined: 02/15/2006

View Profile



Posted: 03/22/21 05:38pm Link  |  Quote  |  Print  |  Notify Moderator

https://convert-formula.com/ah-wh

Using the above, 1280w x 12.8v =100AH, so he does plan on two "100AH" batts.

If his batts are really 120AH, then they are 1.536Kwh not 1.280

In any case, he has either 200AH usable or 160AH usable to compare with his 6s at 260AH usable (although you can go lower with 6s)

It is a contest between having a big enough bank to get through one day on solar vs having a bigger bank for a reserve in case of X days with no solar.

Adding more solar won't help if you already have enough for the one day and the smaller bank. Adding panels won't add to your reserve, and you don't need them to get through a day because you already have enough solar.
--------
It is cringeworthy to say , "Two times less"! Gads. I think that is supposed to mean, "Half", but who knows? [emoticon]

* This post was last edited 03/22/21 05:59pm by BFL13 *   View edit history


1. 1991 Oakland 28DB Class C
on Ford E350-460-7.5 Gas EFI
Photo in Profile
2. 1991 Bighorn 9.5ft Truck Camper on 2003 Chev 2500HD 6.0 Gas
See Profile for Electronic set-ups for 1. and 2.

Almot

out there

Senior Member

Joined: 03/02/2010

View Profile


Offline
Posted: 03/22/21 07:29pm Link  |  Quote  |  Print  |  Notify Moderator

It is not uncommon for LFP manufacturers to make battery with BMS cut-off very low, so usable charge of, say, 100AH battery is 97-99AH. Doesn't mean you should draw 99AH every time, it will last longer if you stop at 20%. But then, it will last longer yet if you stop at 40 or 50%. They are not different from wet cells in this respect, the shallower is cycle - the longer is life, but LFP are much more tolerable to partial charging than wet cells (with due consideration to cells balancing).

Some manufacturers make ~120AH battery and sell it as 100AH, with BMS cut-off at ~15% so you are getting 100AH without much damage to cycle life. Lynax were mentioned in another thread. They rate some of their batteries this way (not all of them), and call it "true"-something. You run nominal 100AH battery all the way to BMS cut-off and get 100AH with inaccessible 20AH remaining.

StirCrazy

Kamloops, BC, Canada

Senior Member

Joined: 07/16/2003

View Profile



Posted: 03/22/21 10:14pm Link  |  Quote  |  Print  |  Notify Moderator

Almot wrote:

It is not uncommon for LFP manufacturers to make battery with BMS cut-off very low, so usable charge of, say, 100AH battery is 97-99AH. Doesn't mean you should draw 99AH every time, it will last longer if you stop at 20%. But then, it will last longer yet if you stop at 40 or 50%. They are not different from wet cells in this respect, the shallower is cycle - the longer is life, but LFP are much more tolerable to partial charging than wet cells (with due consideration to cells balancing).

Some manufacturers make ~120AH battery and sell it as 100AH, with BMS cut-off at ~15% so you are getting 100AH without much damage to cycle life. Lynax were mentioned in another thread. They rate some of their batteries this way (not all of them), and call it "true"-something. You run nominal 100AH battery all the way to BMS cut-off and get 100AH with inaccessible 20AH remaining.


yup its easy to check, fully charge the battery then take 90Ah out of it and read the voltageif its still over 12.5 you can use the full 100% and not worry about it. even at 100% discharge it will last longer than most rv's

Steve

BFL13

Victoria, BC

Senior Member

Joined: 02/15/2006

View Profile



Posted: 03/22/21 10:53pm Link  |  Quote  |  Print  |  Notify Moderator

https://1t1pye1e13di20waq11old70-wpengin........oads/2019/01/BB10012-2021-Spec-Sheet.pdf

12.5v resting is 14% on this table for a 120 rated at 100 (we are told for a BB?). That is in the knee and voltage will drop very fast if you keep the load on.

So to be clear--are you saying if you got 90AH out so you are at 10% as rated which would be 12.1v if using that graph but voltage is above 12.5 which means it is a 120 and that 10v for zero capacity means it is really at 16.7% (20/120) ?

What would the table for a 100AH that is really 100AH say is zero%? Still 10v?

StirCrazy

Kamloops, BC, Canada

Senior Member

Joined: 07/16/2003

View Profile



Posted: 03/23/21 08:07am Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:

https://1t1pye1e13di20waq11old70-wpengin........oads/2019/01/BB10012-2021-Spec-Sheet.pdf

12.5v resting is 14% on this table for a 120 rated at 100 (we are told for a BB?). That is in the knee and voltage will drop very fast if you keep the load on.

So to be clear--are you saying if you got 90AH out so you are at 10% as rated which would be 12.1v if using that graph but voltage is above 12.5 which means it is a 120 and that 10v for zero capacity means it is really at 16.7% (20/120) ?


doesnt mean a 120 spicificly, you try be to factualy some time, it just means that they are using cells that make a larger capacity than the rated capacity so the advertised capacity is the usable capacity. in todays litigation world people would probably sue if they bought a 100ah battery and could only get 85 out of it.

ya I guess that is a good anology. if you find out that it is a true 100 ah battery then just use 85% of the range so set your bottom end at 15% and your top end at 100% you'll increase the life ore than the 3000ish cycles and probably get closer to 5000. if it is still above that 12.8ish volts when you have used 90AH then they have put a larger pack in and fell free to use 100ah on a cycle with a longer cycle life.

for the extra 60 bucks it costs for the increased capacity the companies are being smart warenty wise building in extra capacity and not using it all.

Steve

BFL13

Victoria, BC

Senior Member

Joined: 02/15/2006

View Profile



Posted: 03/23/21 08:17am Link  |  Quote  |  Print  |  Notify Moderator

With the usual tables for SOC/voltage , they are the same no matter what the battery capacity size is.

If the LFP table is the same way, then how can you tell if your actual 100AH batt is at 15% by its voltage compared with the 120AH battery at 15% when they are calling that zero SOC at 10v?

* This post was edited 03/23/21 08:30am by BFL13 *

StirCrazy

Kamloops, BC, Canada

Senior Member

Joined: 07/16/2003

View Profile



Posted: 03/23/21 08:35am Link  |  Quote  |  Print  |  Notify Moderator

BFL13 wrote:



What would the table for a 100AH that is really 100AH say is zero%? Still 10v?


I am chosing to answer this one seperatly as it is a little trickey.

cheep cells, factory seconds and such yes 0 would be 10V, but most batteries actualy have higher than there rated capacity. this is a tip for people building there own batteries also, you want to get matched cells. this isnt an issue though as when you buy from reputable companies they do exactly that. buying factory seconds or "B" cells can save you a lot of money but capacity wise you will get whats advertised and nothing more usaly. so a 280AH cell might test out around 281 or 281AH. an "A" grade cell might test out at 285 or 290. this isnt the only difference if a termanal is stripped or there is a scratch on the metal shell it becomes a "B" grade and might have the higher testing capacity.

normal batteries are like this also we have two places in town , one will do a capacity test and the higher rated ones get sold for more money, the other place will not accept and returns any battery that tests below a spicit point. but most companys sell the ones that test higher as a "premium" battery.

but I digress, to get back to your original question ya the true 0% capacity point will be 10V. that is why with LiFePo4 set ups I am an advocat of not going below the 15% mark, not because it will hurt the battery as they are rated for 3000 cycles (some up to 5000) at 100% depth of discharge so thats that many times you can tke it down to 10V from 100%. quite a long time. my concern is mor to that 10V isnt enough to properly run stuff in the RV. if you go a bit large bank then set your bottom end at 12.5V your still using what 86% of the capacity and you will get no cut out alarms or anything from inverters or other equipment.

how much of your capacity can you use and stay above 12.5V in any other battery. SiO2 drops below 12.5V bettern 75 and 70% capacity
and Lead acid drops to 12.5V below 90% of capacity. so if you look at usable capacity above 12.5V on 100AH batteries for each type you get 85AH on the LFP, say 33AH on the SiO2, and 10AH out of the regular old Lead acid.

now 12.5 is rather harsh so lets look at 12.0V LiFePo4 will let you use 91AH before it hits 12V, SiO2 aproximatly 65AH, and a normal Lead acid about 50AH.

where this stuff becomes realy important is people that need to run CPAP or other mediacal equipment or use there inverter regulary . a lot fo the previous discussions never realy went into the use of them just the data differences in capacity and charging/discharging temps, I feel that is only part of the discussion as there are ways to elemininate the cold tempature issues with LiFePo4 batteries if your willing to do it and they arent that difficult. to me its the way they actualy preform during use that is the important part. thoes LFP batteries will run a inverter at full blast with no alarms for the full 91% of there capacity, no other battery SiO2 or normal is going to get close to that with out alarming.

Steve

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 
Page of 8  
Prev  |  Next

Open Roads Forum  >  Tech Issues

 > Lithium batteries and new solar charger
Search:   Advanced Search

Search only in Tech Issues


New posts No new posts
Closed, new posts Closed, no new posts
Moved, new posts Moved, no new posts

Adjust text size:




© 2021 CWI, Inc. © 2021 Good Sam Enterprises, LLC. All Rights Reserved.