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Old 10-04-2018, 10:22 PM   #1
I Think We're Lost!
Bob Denman's Avatar
Brand: Still Looking
Model: Tiffin Wayfarer 24 BW
State: New York
Posts: 22,195
THOR #8860
A Question About Battery Tenders...

Actually: several questions!
I've got a pair of 12 volt, Group 27 batteries hidden under the stairs.
I've a one Battery Tender Junior, that's left over from my motorcycles.
1. Should I hook that up to just one of the batteries, and let the fact that they're hooked together take care of the other one, or just hook to the ground and one battery, and the hot lead on the other?
2. Is 750 mill-amps enough, or should I just pop for a stouter 'Tender?
3. Will this also take care of the chassis battery at the same time, or should I get a second one for up front?


"What: me worry?"
Good Sam Member 843599689
Current coach: Tiffin Wayfarer 24 BW
Bob Denman is offline   Reply With Quote
Old 10-05-2018, 01:52 PM   #2
Senior Member
Brand: Thor Motor Coach
Model: 2013 ACE 30.1
State: Alberta
Posts: 1,410
THOR #2631
Hi Bob, my 25 cents worth (might be worth less though).......

1. A 3/4 Amp trickle charger should not matter if you just connect to one battery that is paralleled to another battery which is co located (short cables). At that current there is barely any voltage drop across cables to be a concern.

2. Tenders are single stage float voltage trickle chargers and should be enough to keep charged batteries topped up for short term storage. For long term storage using your coach multi-stage converter and shore power to keep all batteries charged would be a better option IMO. Modern multistage converters cycle wet cell batteries to help prevent plate sulphation.

3. If you are in storage mode I assume you turn off your coach and chassis battery latching disconnects. This would mean they are not connected to each other (other than common chassis ground). So likely a second tender would be best assuming you donít do the coach converter and shore power option. There are optional devices for charging both sets of batteries........but I am not familiar with them. Look down the attached link and there is one described there as well as trickle chargers.
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Old 10-05-2018, 02:44 PM   #3
Senior Member
Brand: Thor Motor Coach
Model: Four Winds
State: Ontario
Posts: 265
THOR #9081
Bob, I can only offer you two cents worth. If you have AC power available just use your current onboard equipment to maintain the batteries. Some coaches though are not designed to charge the chassis batteries from shore power/generator and in this case you would add something like a "Trik-L-Start".
2018 Four Winds 31Y
Peterrrr is offline   Reply With Quote
Old 10-05-2018, 07:07 PM   #4
Senior Member
Brand: Thor Motor Coach
Model: Hurricane 27K
State: California
Posts: 623
THOR #2544
Bob, I have battery tenders for all my toys. I have two batteries in the searay and one battery tender charges them both. If they are very low when you hook up the charger it make take a day or more to get the green light. When my son deployed to Bahrain in May, it took three or four days to get to the maintenance mode.
This post is opinion based on experience.
2015 Hurricane 27K
2013 Sea Ray 220SD
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