Forum Discussion

klm's avatar
klm
Explorer
Oct 15, 2013

Can batteries test "ok", but still be bad?

Let me begin by saying I have no knowledge/skills when it comes to all things mechanical, etc. This saga begins when I was parked for 5 mo season, and used a battery tender on the engine start batteries (2). After several attempts, finally got the tender to get to the "float" mode - needed to clean posts to get there, also had batteries tested, put under load and tested - all good according to the mobile tec. Departure day, the tender was no longer in "green float/charged mode", but indicating low voltage - not sure when that happened as I did not check tender every day. Anyway, the engine starts, first try - good - the dash gauge read slightly below "normal". I am thinking the batteries will charge as I am driving. Wrong, they are draining. The alternator was bad, had it replaced - tec put charge on batteries, tested them, said they were ok. I am leary of their reliability. I have arrived at my winter camping spot and have the tender connected - 1 1/2 days, still in charge mode - this is after 2 days of driving - the batteries should be near fully charged - so not sure why the tender is taking so long. The batteries are Delta, 2 1/2 yrs old. So, is it possible that even after being tested by different tecs that one or both of these batteries are bad? What other steps can be taken to test these batteries? Would you replace them? thanks
Kathy
Class A
  • allbrandauto's avatar
    allbrandauto
    Explorer
    Oct 15, 2013
    to test a battery remove the vent caps with a battery hydrometer test specific gravity all cells should be in 1.275 range if any cell is more than 25 present off battery is bad if all cells are low battery must be charged up and retested if all cells are good battery has to be load tested hook load tester to pos. and neg. battery post load battery for 10 seconds voltage should not drop below 11 volts and volts should come back to over 12 volts quickly
  • ferndaleflyer's avatar
    ferndaleflyer
    Explorer III
    Oct 15, 2013
    If those batteries are fully charged the float charger has nothing to do---until they discharge a bit. Don't make it more complicated than it is
  • prism's avatar
    prism
    Explorer
    Oct 15, 2013
    klm wrote:
    OP back, with a couple of follow up questions. The tender is hooked up to the 2 engine start batteries, not house batteries. Those engine batteries should have been fully charged from 2 days of driving, when the tender was connected. Am I to gather that I should not base battery condition on the fact that the tender is not indicating "charge/float"? Would I be better off using a trickle charge system? I am plugged in to shore power, and will be sitting for about 3 mo before heading to FL for the winter.


    Your post is a little hazy to me.We fully realize its the chassis batterys the tender is hooked up to so not sure why u said that.?
    You said and I quote here"Those engine batteries should have been fully charged from 2 days of driving, when the tender was connected."
    The Battery tender does nothing when driving the unit and your battery has a fair amount of draw when driving.SO after stopping and pluging into Shore power to activate your battery tender it would take about 24 hours for the tender to say or indicate fully charged
    Also to note its not to say your tender is not operating correctly and giving a false reading.Take a volt meter and see what the battey voltage is.Its should be in the 12.7V range or slightly higher
  • klm's avatar
    klm
    Explorer
    Oct 15, 2013
    OP back, with a couple of follow up questions. The tender is hooked up to the 2 engine start batteries, not house batteries. Those engine batteries should have been fully charged from 2 days of driving, when the tender was connected. Am I to gather that I should not base battery condition on the fact that the tender is not indicating "charge/float"? Would I be better off using a trickle charge system? I am plugged in to shore power, and will be sitting for about 3 mo before heading to FL for the winter.
  • prism's avatar
    prism
    Explorer
    Oct 15, 2013
    beemerphile1 wrote:
    You don't specify but most Deltran Battery Tenders are only .75 to 1.25 amp output. If you have any load at all on the battery such as a radio, it will almost continually be charging.

    absolutely how they work.One has to realize there not a battery charger per say.If your batterys get run down u will need to charge them fully before any tender will keep then up and as already posted
    any amount of draw on them while sitting a battery tender will not keep up.If for some reason U need to have a constant draw from your coach batterys then link them to your house batterys and the house inverter/charger will keep them up(one idea)
    To answer the OP question based on what you have posted i would say your house batterys are fine
  • beemerphile1's avatar
    beemerphile1
    Explorer
    Oct 15, 2013
    You don't specify but most Deltran Battery Tenders are only .75 to 1.25 amp output. If you have any load at all on the battery such as a radio, it will almost continually be charging.

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