RV Trip Planning Discussions

Go Back   iRV2 Forums > CAMPING, TRAVEL and TRIP PLANNING > Boondocking
Click Here to Login
Join iRV2 Today

Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts.
Thread Tools Search this Thread Display Modes
Old 01-08-2020, 12:54 AM   #1
Senior Member
Oregon RR's Avatar
Join Date: Oct 2016
Posts: 118
Battery Behavior on Charger

Just finished putting four Trojan T-105 AGM batteries in a Torklift box on the tongue of my toyhauler.

Previously I was running two Trojan T-105 wet cell batteries which I removed and hooked up to an 8-AMP Battery Minder charger. I had the new batteries on the same charger while waiting to install and they would show 14.4 volts and then down to 13.55+ on float. The Battery Minder is supposed to charge at 14.4 and then reduce to 13.6 volts.

The three year "old" wet cells have been on a Progressive Dynamics 9200 charger-inverter 24/7 when not on the road. I've tried to never discharge below 12.2 volts, but have went to 12 volts a couple times. We have solar and a generator to recharge when out camping.

The "old" batteries are showing 14.2 volts, then dropping to 13.4 volts while on the Battery Minder charger - a little short of the stated charging voltage of the Battery Minder.

1) Can anyone explain why there is a voltage drop between new and old batteries while on the same charger?
2) If anyone has experience with Battery Minder chargers, do you think the desulfating process may bring the voltage up some if I leave the batteriess on the charger for a couple weeks? I'm giving a friend the old batteries and I'd like to be able to accurately describe their condition and/or improve them if possible..

I've not taken the "old" batteries off the charger and rested them for a day to get their base charge level.

Desert Fox Toyhauler
Hauls Husqvarna, KTM and BMW Bikes
Likes to Boondock since solar install!
Oregon RR is offline   Reply With Quote
Join the #1 RV Forum Today - It's Totally Free!

iRV2.com RV Community - Are you about to start a new improvement on your RV or need some help with some maintenance? Do you need advice on what products to buy? Or maybe you can give others some advice? No matter where you fit in you'll find that iRV2 is a great community to join. Best of all it's totally FREE!

You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with other RV owners, see fewer ads, upload photographs, create an RV blog, send private messages and so much, much more!

Old 01-08-2020, 09:22 AM   #2
Senior Member
Join Date: Jan 2019
Posts: 142
Having had the Battery Minders for several years (maybe seven?), I can report that my voltage hovers around 13.6 while on the charger. My group 31 batteries are lasting about five years or so. I very rarely let my batteries get below 12.1 volts when I am camping.

I don't know whether the pulsating "desulphation" feature of the Battery Minders really accomplishes anything, since I am not an expert. But my batteries are performing satisfactorily, so I guess the Battery Minder is doing the job.

profdan is offline   Reply With Quote
Old 01-08-2020, 10:22 AM   #3
Senior Member
Ford Super Duty Owner
Join Date: Dec 2005
Location: Buxton, North Dakota
Posts: 3,762
It is more than likely a difference in battery chemistry between Wet Cell and AGM rather than new vs. old. It is withing the margin of error any way.
2003 Winnebago Adventurer 38G F53/ V10 605 watts of Solar
1999 Winnebago Brave 35C F53V10 Handicap Equipped
1999 Jeep Cherokee, 1991 Jeep Wrangler Renegade and 2018 Chevrolet Equinox Diesel
John Hilley is offline   Reply With Quote
Old 01-08-2020, 06:05 PM   #4
Senior Member
Winnebago Owners Club
Workhorse Chassis Owner
Join Date: Nov 2018
Posts: 546
Battery tenders/minders/maintainers I've looked at usually employ a switched float mode, turning the charger on when the battery drops to a given low voltage and turning off at a higher voltage. So depending on what point in the cycle you measured it, you might see a terminal voltage somewhere between those two points.

In my opinion, I think the desulfator/rejuvination mode is mostly a gimmick. Maybe one can show that a battery which has suffered a particular trauma might benefit from it, but in my experience most battery issues are eggs you cannot uncook. Can't hurt, but probably won't help.

You can do a measured discharge on these batteries and can report to your friend exactly what their capacity is.

Mark B.
Albuquerque, NM
Mark_K5LXP is offline   Reply With Quote

battery, charger

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools Search this Thread
Search this Thread:

Advanced Search
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

Similar Threads
Thread Thread Starter Forum Replies Last Post
Weird battery behavior - Ideas? ficodek Newmar Owner's Forum 15 11-24-2017 07:49 PM
House battery isolator... strange behavior? wamcneil Monaco Owner's Forum 2 03-11-2017 07:09 PM
RVI brake battery charger vs toad charger dfwm_newf Class A Motorhome Discussions 8 04-06-2015 05:22 PM
Dimensions inverter/charger - charger off problem Mr_Bill Winnebago Industries Owner's Forum 2 12-06-2009 01:12 PM
Removing the Converter Charger & Installing a 3-Stage Charger Only Klaybus 5th Wheel Discussion 5 03-12-2006 10:06 AM

» Featured Campgrounds

Reviews provided by

All times are GMT -6. The time now is 05:23 AM.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2020, vBulletin Solutions, Inc.