RV News RVBusiness 2021 Top 10 RVs of the Year, plus 56 additional debuts and must-see units → ×


Reply
 
Thread Tools Display Modes
Old 10-30-2020, 06:26 AM   #1
JCR
Member
 
Join Date: Feb 2020
Posts: 57
On board converter or external charger (Revisited)

This has been discussed before however I have a new question. I noticed that my battery bank (2 - 12 v deep cycle batteries) start out at 100 % when boondocking. As I use the heater or other devices and after some time the battery charge dissipates to about 90%. In effort to top off the batteries back to 100% the generator takes several hours to bring it back up to 100% if at all. This seems to me that the converter is sensing still plenty of battery power and puts out only a trickle charge .I was wondering if an external charger one without trickle capabilities will bring it back to 100% quickly hence saving generator fuel. Appreciate thoughts on this and recommendations.
JCR is offline   Reply With Quote
Old 10-30-2020, 06:41 AM   #2
Site Team - Lou
 
Herk7769's Avatar
 
Join Date: Oct 2009
Location: South Eastern PA
Posts: 22,834
When we boondocked I waited until the 3rd light (GOOD) went out to recharge. The capacity of the battery is 50% when that light just goes out.

The generator/converter takes too long to get the battery above 90%, so I carried a Ship-n-Shore external battery charger that I plugged into the generator.. The genertaor/ship-n-shore plus the converter does an adequate job getting it to 95% pretty quickly (2-3 hours) and that was fine for me.

We boondocked this way for 4-5 weeks at a stretch and when we rotated/traveled to a full hookup site I let it top off the battery to 100% (took a full day (18-24 hours)).
Attached Thumbnails
Click image for larger version

Name:	Battery Display.jpg
Views:	20
Size:	79.2 KB
ID:	242208  
__________________
Lou, Laura, & Freya the wonder dog
2008 GMC Sierra 3000HD Crewcab SB Allison Duramax
2019 Flagstaff 8529FLS - Pullrite 3300
HAM CALLSIGN - KC3FFW
Herk7769 is offline   Reply With Quote
Old 10-30-2020, 07:00 AM   #3
JCR
Member
 
Join Date: Feb 2020
Posts: 57
Thanks for your reply.. That is what I am thinking. If I can get a straight charger (fast charge) without the charger sensing high voltage and kicking it into a trickle charge that would return the battery bank up to 100% within a short time as compared to the onboard converter working in a trickle charge mode . What battery charger are you using ..Ship and shore model #
JCR is offline   Reply With Quote
Old 10-30-2020, 07:10 AM   #4
Senior Member
 
Join Date: Dec 2015
Posts: 182
Don't worry about charging back to 100% all the time. Once every couple of weeks will do fine. I run ours down to around 50-60% and them charge them back up to 80-90%. This takes about 2 hours usually. That last 10-20% is a waste of generator time.
Of course now that we have a solar panel I just keep track of them and once in a while I top them off to 80% if the solar is struggling to keep up (depends on shade.) My wife wanting to use the microwave means the charging is mostly done then.
__________________
N. Brevard County, Florida

2010 Lexington 255 GTS

2000 Jeep Cherokee Toad
dontay is offline   Reply With Quote
Old 10-30-2020, 07:19 AM   #5
PhD, Common Sense
 
Join Date: Feb 2017
Location: Fairborn, OH
Posts: 1,384
This raises the question:

Will constantly charging your battery from 90% to 100% wear your batteries (flooded, I assume) out faster than going through fewer cycles of 50% to 100%?
eye95 is offline   Reply With Quote
Old 10-30-2020, 02:33 PM   #6
Senior Member
 
Join Date: Jan 2018
Location: Raleigh, NC
Posts: 3,376
Wearout process of flooded lead acid batteries

Quote:
Originally Posted by eye95 View Post
This raises the question:

Will constantly charging your battery from 90% to 100% wear your batteries (flooded, I assume) out faster than going through fewer cycles of 50% to 100%?
The chemical processes are completely described here:
https://en.wikipedia.org/wiki/Lead%E2%80%93acid_battery

Basically during discharge
  • At the negative plate, solid lead and sulfuric acid become lead sulfate
  • At the positive plate, lead oxide and sulfuric acid become lead sulfate
Lead sulfate is the white powder you see on the plates of a dead battery.

As I understand it, wearout is during the charge cycle when the lead oxide and solid lead are deposited on their respective electrodes. Years ago, I was warned that the "Fast Charge" in vogue in the 1960s deposited the lead in such big grains that a bumpy road would cause lead particles to fall off the plates. Once off the plates, they no longer contact the charged plate and cannot take part in further reactions.

Another failure mode is conductive lead particles positioned to short adjacent positive and negative plates known as a shorted cell.

A deep charge could even put holes clear through the plate (cheap battery, not a GC2), leaving those spots unavailable for future reactions.

To answer the original question, it seems that if you were recharging after reaching only 90%, that most of the lead remains on the plate and does not contribute to wear. Swiss-cheese plates and shorted cells are less likely to occur if minimal lead is removed from the plates.
__________________
Larry

Sticks and Bricks: Raleigh, NC
2008 Cherokee 38P: at Ivor, VA permanently
Larry-NC is offline   Reply With Quote
Old 10-30-2020, 02:55 PM   #7
Member
 
Join Date: Jan 2020
Posts: 58
That's just the problem with lead acid batteries....the last 10% takes the longest since they can't accept as much charge the closer they get to being full. Its always best to try to get them back up to 100% to keep sulfation to a minimum but using a generator for 4 hours to get that last 10% isn't always reasonable when on a camping trip. This is why lithium batteries are so good. That last 10% takes the same amount of time as the previous 10%..and the 10% before that. Lithium batteries pretty much accept as much as you can give them limited by their BMS.

As far as one discharge to 50% vs 5 discharges to 10%, if you look at a discharge vs cycles, the charts are not linear so you would be better doing more short shallower discharges than fewer deeper discharges.
bradbill is offline   Reply With Quote
Old 10-30-2020, 04:20 PM   #8
Senior Member
 
camaraderie's Avatar
 
Join Date: Feb 2014
Posts: 2,480
Bradbill has it right. The INTERNAL resistance of a battery increases as it charges NO MATTER WHAT CHARGER you use. Only charging to 90% makes sense ON A SHORT camping trip if you then plug in at home and bring it back to 100%. AGM;s are MUCH more sensitive to this so this is advice for wet cells.
It make no sense to charge from anythning but the converter. Now if you have a nice solar panel...you can charge from the genny then leave the panel to top it off while boondocking. Running 3 hours of genny for 10% of the charge prolly will be more expensive than new batteries!
Note that if you do not regularly bring the battery back to 100%...it will become sulfated and 90% will be your new 100%...and 80% will be your new 90% as you begin your trek down the battery death spiral.
And here's a depth of discharge curve for a premium T105 ... ALL wet cell curves follow the same degradation curve but cycles vary by quality and price.
Attached Thumbnails
Click image for larger version

Name:	DODT105.JPG
Views:	15
Size:	31.2 KB
ID:	242218  
__________________
________
Cam
2015 Georgetown 280DS
2019 Vespa Primavera 150's (pair)
camaraderie is offline   Reply With Quote
Old 10-30-2020, 07:40 PM   #9
Senior Member
 
Join Date: Jul 2017
Location: North of Seattle, WA
Posts: 9,792
If a battery is allowed to sit in a partially discharged state the sulfate formed becomes a hard form of sulfate and it's difficult, to the point of often being impossible, to convert it back to lead and other elements.

To use an analogy, charging a battery only partially is a lot like cutting an inch off your shoe laces every time you tie your shoes. You'll have plenty of lace to tie the shoes for quite a while but one day you won't.

Same with a lead acid battery. Eventually you won't be able to fully charge the battery regardless of how long you leave it on a charger.

As for stand alone battery chargers, yes, one can force a charge more quickly if you crank it high enough. Unfortunately that practice can also create excess gassing deep in the plates and not only boil the battery but cause lead and lead oxide to flake off the plates.

Quote:
A rechargeable battery cannot be recharged at an arbitrarily high rate. The internal resistance of the battery will produce heat, and excessive temperature rise will damage or destroy a battery. For some types, the maximum charging rate will be limited by the speed at which active material can diffuse through a liquid electrolyte. High charging rates may produce excess gas in a battery, or may result in damaging side reactions that permanently lower the battery capacity.
__________________
"A wise man can change his mind. A fool never will."

"You only grow old when you run out of new things to do"

2018 Flagstaff Micro Lite 25BDS
2004 Nissan Titan
TitanMike is offline   Reply With Quote
Old 10-30-2020, 10:04 PM   #10
Senior Member
 
Join Date: Jan 2020
Posts: 490
Why not just upgrade the onboard converter to something that charges the lead acid batteries better?
NavyLCDR is offline   Reply With Quote
Old 11-01-2020, 10:15 AM   #11
Senior Member
 
Join Date: Mar 2014
Posts: 2,325
Quote:
Originally Posted by NavyLCDR View Post
Why not just upgrade the onboard converter to something that charges the lead acid batteries better?
That's where I went.

WFCO does not publish specs (that I could find) for when their converters shift from bulk mode (approx 14.4V) to normal mode (13.7V). Let's just say I never caught my 2 WFCO 8735P converters in bulk mode. And they never went to trickle charge mode (13.2V).

When I replaced both with Progressive Dynamics PD4135 converters, I was able to observe all 3 voltages at the appropriate time.

There are 2 major problems with optimizing RV converters for maximum charge rates.
  • maximum charge rate is temperature sensitive - battery temp must be kept below a certain temp to minimize unwanted chemical reactions. This would require wire temp probes plus programming in the converter.
  • RVs with heavy battery usage, and large converters that are located a ways away from the batteries will have voltage drops between the converter and batteries. The converter senses battery voltage at the converter to decide what charge mode to use. A voltage drop in the wiring will mislead the converter.
For these reasons, RV converter makers intentionally use conservative charge rates to avoid overheating or destroying batteries. Better to take an hour or two longer to reach full charge than destroy the battery. WFCO converters are typically the most conservative.

The other limitation on RV converters is sensitivity of other equipment to over-voltages. "12V" light bulbs and LEDs do not like 15V inputs. They tend to let the magic smoke out when voltage goes too high. For that reason, RV converter charging and equalization voltages are limited to 14.4V when higher might be optimum.

Can you charge faster than an RV converter? Yes, but only under very controlled and monitored conditions. The difference in charge times really only matters when recharging via generator. Plugging into shore power - do you really care whether it takes 6 or 9 hours to restore your batteries to 100% from 50%?

Fred W
2019 Flagstaff T21TBHW A-frame with 2 GC-2 batteries for 4 nights boondocking, no generator, no solar
2008 Hyundai Entourage minivan
camping Colorado and adjacent states one weekend at a time
pgandw is offline   Reply With Quote
Old 11-01-2020, 04:52 PM   #12
Senior Member
 
Join Date: Jan 2018
Location: Raleigh, NC
Posts: 3,376
4-wire connection

Quote:
Originally Posted by pgandw View Post
  • RVs with heavy battery usage, and large converters that are located a ways away from the batteries will have voltage drops between the converter and batteries. The converter senses battery voltage at the converter to decide what charge mode to use. A voltage drop in the wiring will mislead the converter.

Fred W
I've never understood why converter manufacturers don't make their products with a four-wire connection. Laboratory supplies all have this option. There are two heavy leads to carry the charging current and two lightweight "sense" leads that provide an indication to the converter of the voltage at the battery terminals. (The sense inputs at the converter or supply are high-impedance. There is minimal current in these leads, hence minimal voltage drop.)
__________________
Larry

Sticks and Bricks: Raleigh, NC
2008 Cherokee 38P: at Ivor, VA permanently
Larry-NC is offline   Reply With Quote
Old 11-01-2020, 05:45 PM   #13
Senior Member
 
Join Date: Jul 2017
Location: North of Seattle, WA
Posts: 9,792
Quote:
Originally Posted by Larry-NC View Post
I've never understood why converter manufacturers don't make their products with a four-wire connection. Laboratory supplies all have this option. There are two heavy leads to carry the charging current and two lightweight "sense" leads that provide an indication to the converter of the voltage at the battery terminals. (The sense inputs at the converter or supply are high-impedance. There is minimal current in these leads, hence minimal voltage drop.)
My Solar controller does a better job of sensing battery voltage as it's installed within inches of the batteries. It also senses battery temp with a thermistor clamped to the positive terminal. Charge can be adjusted according to temp although I've changed to Lithiums and this is now moot.
__________________
"A wise man can change his mind. A fool never will."

"You only grow old when you run out of new things to do"

2018 Flagstaff Micro Lite 25BDS
2004 Nissan Titan
TitanMike is offline   Reply With Quote
Old 11-01-2020, 05:56 PM   #14
Senior Member
 
Join Date: Jan 2018
Location: Raleigh, NC
Posts: 3,376
Location, location, location

Quote:
Originally Posted by TitanMike View Post
My Solar controller does a better job of sensing battery voltage as it's installed within inches of the batteries. It also senses battery temp with a thermistor clamped to the positive terminal. Charge can be adjusted according to temp although I've changed to Lithiums and this is now moot.
The 38' Cherokee trailer has the converter mounted inside at the base of the front wall. The cables are perhaps 4-5 feet long. The trailer is permanently sited and is always plugged in so deep charging is never an issue.

But our 22' SOB, which does travel, has the converter mounted at least half way back, even though there is room to have put it under the bed at the front wall. I suppose I could move the converter and leave the fuse-distribution board in place, using the existing cables to connect the two and providing new short cables from converter to battery.
__________________
Larry

Sticks and Bricks: Raleigh, NC
2008 Cherokee 38P: at Ivor, VA permanently
Larry-NC is offline   Reply With Quote
Old 11-01-2020, 06:54 PM   #15
Member
 
Join Date: Sep 2019
Location: South Jersey
Posts: 56
So leaving mine plugged in to sure power all winter will not damage my batteries?
HemiHemi19 is offline   Reply With Quote
Old 11-01-2020, 07:03 PM   #16
Site Team
 
bikendan's Avatar
 
Join Date: Jan 2007
Location: Camano Island, Washington
Posts: 23,301
Quote:
Originally Posted by HemiHemi19 View Post
So leaving mine plugged in to sure power all winter will not damage my batteries?
I do. I just check the electrolyte level every couple of weeks.
__________________
Dan-Retired California Firefighter/EMT
Shawn-Musician/Entrepreneur/Wine Expert
and Zoe the Wonder Dog(R.I.P.)
2016 PrimeTime TracerAIR 255, pushing a 2014 Ford F150 SCREW XTR 4x4 3.5 Ecoboost w/Max Tow Package
4pt Equal-i-zer WDH and 1828lbs of payload capacity
bikendan is online now   Reply With Quote
Old 11-01-2020, 07:38 PM   #17
Site Team
 
Mr. Dan's Avatar
 
Join Date: Mar 2014
Location: Grayson County, Texas
Posts: 15,134
Quote:
Originally Posted by bikendan View Post
I do. I just check the electrolyte level every couple of weeks.
Same here ó but every couple of months.
__________________
SEARCH is your friend!
FR Wildcat 295RSX / GMC Sierra

Nights Camped: '13 = 49/'14 = 74/'15 = 74/'16 = 85/'17 = 110/'18 = 111/'19 = 86/'20 = 108; booked = 0
Mr. Dan is offline   Reply With Quote
Old 11-01-2020, 08:31 PM   #18
Member
 
Join Date: Sep 2019
Location: South Jersey
Posts: 56
Ok thatís good to know. Thanks for the replies.
HemiHemi19 is offline   Reply With Quote
Old 11-01-2020, 09:35 PM   #19
Salty Senior
 
Join Date: Oct 2020
Location: Pompano Beach
Posts: 21
LEAD ACID BATTERIES 001
First, please look at your battery and get the manufacturer, part number, and specs. Look up your battery on the web. For a house battery it should be aDEEP CYCLE RATING. Look for charge profile. ALL LA batteries (flooded, agm,gel) will have a similar profile. From 12.1vdc, =50%, BULK CHARGE at constant current to 14vdc (varies with bat).
Acceptance charge@ 13.4 vdc until current drops below 0.xx amps dc. (100%)

When you set bat type on your charging device, they provide the correct safe profile. Trying force that last 10% into a LA bat can kill the batteries.

OBTW. A 100ah LA bat gives you 50ah usable, 100ah LiFePO4 gives you �� ah !!

Happy Camping
Captain Gene is offline   Reply With Quote
Old 11-01-2020, 10:15 PM   #20
Senior Member
 
Join Date: Jul 2017
Location: North of Seattle, WA
Posts: 9,792
Quote:
Originally Posted by Larry-NC View Post
The 38' Cherokee trailer has the converter mounted inside at the base of the front wall. The cables are perhaps 4-5 feet long. The trailer is permanently sited and is always plugged in so deep charging is never an issue.

But our 22' SOB, which does travel, has the converter mounted at least half way back, even though there is room to have put it under the bed at the front wall. I suppose I could move the converter and leave the fuse-distribution board in place, using the existing cables to connect the two and providing new short cables from converter to battery.
I left my converter where it was and just ran ~20' of #4 awg wire from converter to battery bank. Also increased negative connections to frame on both ends, converter and battery, to #4 awg. When I still had lead/acid batteries the charging current increased GREATLY and now that I have Lithiums the wire carries enough charge to fill my batteries from 25% to a true 100% in 3 hours when I have to run the generator.
__________________
"A wise man can change his mind. A fool never will."

"You only grow old when you run out of new things to do"

2018 Flagstaff Micro Lite 25BDS
2004 Nissan Titan
TitanMike is offline   Reply With Quote
Reply

Tags
converter

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
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Featured Campgrounds

Reviews provided by

Disclaimer:

This website is not affiliated with or endorsed by Forest River, Inc. or any of its affiliates. This is an independent, unofficial site.



All times are GMT -5. The time now is 03:37 AM.