Forum Discussion

bzp's avatar
bzp
Explorer
Sep 10, 2018

Converter Charger

Hi Everyone,
I have a 2004 Winnebago Journey and recently invested in three new 12V AGM house batteries. The house batteries work great but my converter charger is too slow to charge them properly. I have a model 7455 Parallax 13.6 VDC, 55 amp charger which was original equipment on my coach. My charging problem seems to be two fold in my opinion: First the charging voltage is low and second the charger turns itself down to low amps long before the batteries can be fully charged. These batteries can handle up to 190 amp charge. I am considering replacing my charger with a new three stage 55 amp charger that charges at higher voltage initially (14.7 VDC) and hopefully won't turn down too soon. I don't want to go with a larger amperage because I don't want to overload or replace my current wiring. I am concerned however that the higher voltage could cause some damage to my existing 12 VDC power users. I called Winnebago to ask them and they said they offer no advice concerning modifications.

Will it be safe for me to install a 14.7 VDC charger in my 2004 vintage coach?

Should I consider going with higher amperage and changing my wiring?

Thanks in advance for your time and input.

Bill
  • ScottG's avatar
    ScottG
    Nomad
    Sep 10, 2018
    That's a lousy charger. If you want decent performance, upgrade to something like a Progressive Dynamics converter with 3 stage charging.
    You'll never get that old converter to do a good job.
  • BFL13's avatar
    BFL13
    Explorer II
    Sep 10, 2018
    14.7 will not hurt your RV stuff at all. 15.4v is the limit for a Norcold fridge, eg.

    Before buying, what exactly AGMs do you have? Each AGM has its own specs for charging voltages etc, so not all chargers can do some AGMs.

    You can leave the 7455 in place and use a portable charger or mount a deck mount converter closer to the batteries if you have room, which would perhaps be easier.

    Some (all?) AGMs want a 20% minimum amps recharge at least every so often, so 300AH is at least 60 amps for that, where that is amps at the battery not charger's rating.

    I have 450AH of AGMs and with a 55 amp charger I have to split the bank and do batteries individually to get over 20% amps. AGMs can be a pain, but they do have advantages also.
  • wa8yxm's avatar
    wa8yxm
    Explorer III
    Sep 11, 2018
    I would recommend a better charger (Progressive Dynamics. Stand alone use a 9200, intergrated with your power distribution panel a 4600)

    As for amprage.. Total the C/20 (20 hour amp hour rating) of your batteires

    Group 24 about 75
    27/29 just under/over 100 (use 100)
    31 125-130

    GC-2 PAIRS (note this is for the two batteries in series 220

    Multiple by 0.30 (30%)
    and that's your answer.
  • John_Wayne's avatar
    John_Wayne
    Explorer II
    Sep 11, 2018
    Look at Best Converter at the progressive Dynamics 3 stage charging converter with charge wizard. Easy to swap out and a lot better converter.
  • time2roll's avatar
    time2roll
    Nomad
    Sep 11, 2018
    bzp wrote:
    I am considering replacing my charger with a new three stage 55 amp charger that charges at higher voltage initially (14.7 VDC) and hopefully won't turn down too soon. I don't want to go with a larger amperage because I don't want to overload or replace my current wiring. I am concerned however that the higher voltage could cause some damage to my existing 12 VDC power users.

    14.7 will not be an issue for the RV 12v components.

    What is important is if the 14.7 matches the battery charging specifications.

    If you want to go 100+ amps... consider pulling 120v power close to the battery and mount the converter close for easier 12v wiring and even faster charging. AGM likes to charge fast as long as you stay in specs.

    Please post what brand batteries and converter model you are considering for best answers.
  • MEXICOWANDERER's avatar
    MEXICOWANDERER
    Explorer
    Sep 11, 2018
    Those three AGM batteries will snack on 100 amps much like a wolf can eat a hundred mice and not stop to burp. That's 33 amperes per battery which is way way way within max charge limits. Telecom of course is different. But this isn't telecom.

    Anyone actually see full charge percentage of amp hour capacity at a certain voltage for other than Concorde Lifeline batteries. For instance some AGM batteries claim 14.8 volts for absorbsion. Do they list a finish amperes or percentage?
  • BFL13's avatar
    BFL13
    Explorer II
    Sep 12, 2018
    My two kinds of AGMs don't. One kind wants 14.5 to 14.9 no minimum amps, and the other is 14.4 no minimum amps. Neither has a "full" indicator like that 0.5a/100AH. They both say "full" resting is about 13.0v

    AGMs drive you crazy. Just finished an 8 day session off grid with some solar during the day to keep things going. Started with full AGMs at 450AH as full. After the 8 days was down 167 AH on the 450. so 37% SOC by the end.

    Drove home, alternator charging plus solar got it down to - 135. Plugged in the 55a converter (no attempt at 20%) and by bedtime it was - 96AH. Charging amps tapered way down. Now it is -45AH and amps are 1.9a at 14.5v.

    0.5a per 100AH should be 2.25a, but am at 1.9 and still down 45AH on the AH counter.

    I am thinking this is where LY and Mex will say to run the batts down to 50% SOC and charge them up at 20% or better till they are full, because they are not going to like this whole deal they are on now?

    The actual camping off grid was a total success, but the follow up once home to get back to be able to go out camping again with full batts is a real pain. :(
  • tenbear's avatar
    tenbear
    Explorer
    Sep 12, 2018
    I replaced the single stage charger in my 2005 Thor MH with a Progressive Dynamics, I forget the model. I also replaced the old #8 battery wiring with #4. I only have one battery, no more easy to use space for another battery. The charging is soooo much faster and the one battery seems to work fine for the camping I do, mostly with hookups but some dry camping.

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