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  1. #1
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    Default A weekly timer on my battery charger - is this a mistake?

    The scenario:

    The batteries we use for camping and loadshedding backup spend most of their life doing absolutely nothing. Sometimes they spend all this time connected to a float (trickle) charger.

    A good 3 stage charger drops into float mode when the load on the charger is less than 10% of its rated load. A 30 Amp charger will drop voltage to say 13.6V when the batteries are drawing less than 3 Amp. If the UPS inverter circuit is drawing 2.5 Amp continuously, that means the charger only drops into float mode when the batteries draw less than 0.5 Amp. When one battery cell goes bad, it draws more than 0.5 Amp and the whole battery bank is then force-fed over 14V for weeks on end until all the batteries dry and crash.

    For a 12V lead acid battery, the correct float/trickle charge voltage is the subject of some debate. Victron have introduced a "storage" mode whereby the battery spends most time at 13.2 V, substantially less than the 13.6 to 13.8 most other people talk about. Victron does this with a timer . . . most time at 13.2 and then a short full charge once a week. But one battery going bad in the bank again stops the Victron Charger from dropping properly into float and storage mode.

    Am I making a mistake to try this?:

    I want to interrupt the mains supply to the charger with a NC relay/contactor. The control circuit/timer detects the presence of the mains supply. If Eskom fails, the relay is closed and the charger waits for Eskom to come back on. When Eskom is back, a timer waits for say 2 days before opening the relay and switching off the charger. A week later, the relay is closed for 6 hours to allow the charger to top up the batteries. Repeats every week. (will do other controls to stop inverter draw through a storage week)

    So the question boils down to this: Is it better to store a lead acid battery either: a. charger switched off and tiny/tiny current draw (5 mA), or b. being trickle charged at a mystery voltage which sometimes is not really a trickle charge?

    Thank you for listening

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    Default Re: A weekly timer on my battery charger - is this a mistake?

    New batteries have a six month shelve life.

    I have two new 7Ah batteries, to be utilised as needed in the near future, and once a month I put them on a solar trickle charges to top them up.

    If batteries have no draw of any kind then your thinking is not wrong.
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  4. #3
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    Default Re: A weekly timer on my battery charger - is this a mistake?

    The guys with Benton chargers for their auxiliary batteries; do you leave them permanently connected while not camping?

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    Default Re: A weekly timer on my battery charger - is this a mistake?

    Quote Originally Posted by Jonatan View Post
    The guys with Benton chargers for their auxiliary batteries; do you leave them permanently connected while not camping?
    Since they released the bx2 - plus minus 12 years. I manually reset when using big loads as it doesn't always kick into charge mode from maintenance mode.
    Everything should be made as simple as possible, but no simpler.

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    Default Re: A weekly timer on my battery charger - is this a mistake?

    @JONATAN
    You mention a battery bank. Are these batteries then connected in series and at what voltage?
    If connected to a UPS with a built in charger does it imply you want this charger disconnected when you introduce another charger/s?
    My thinking would be to merely use a simple timer to disconnect the AC a few minutes every 2 weeks so that the batteries can do some work and then recharged afterwards.

  7. #6
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    Default Re: A weekly timer on my battery charger - is this a mistake?

    Quote Originally Posted by Jonatan View Post
    The guys with Benton chargers for their auxiliary batteries; do you leave them permanently connected while not camping?

    Yep, all the time.


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    Default Re: A weekly timer on my battery charger - is this a mistake?

    Old days method for lead acid batteries that would be stored or not used for long periods was to charge battery full, then empty out the acid (neutralize and discard acid correctly) and store on shelf. When batterp required for use, buy correct SG acid and fill up battery cells then charge up before needed.

    An intelligent charger also works but like all charging batteries, always check water levels etc.

    Not an expert, just my way of thinking.
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  9. #8
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    Default Re: A weekly timer on my battery charger - is this a mistake?

    Quote Originally Posted by ekkekan View Post
    @JONATAN
    You mention a battery bank. Are these batteries then connected in series and at what voltage?
    If connected to a UPS with a built in charger does it imply you want this charger disconnected when you introduce another charger/s?
    My thinking would be to merely use a simple timer to disconnect the AC a few minutes every 2 weeks so that the batteries can do some work and then recharged afterwards.
    My systems typically have the charger (360Watt) and inverter (1500Watt) as two seperate units. Inverter inputs are all 12V with a variable number of 12V batteries in parallel. Most typical is 3 X 105 AmpHr batteries and often 1 of these 3 batteries are removed while camping. Inverters typically draw 2 to 2.5 Amp switched ON with no load connected to output. We usually switch them off during the months that Eskom is coping - but some of us forget . . . .

    This is what I want to test:

    Click image for larger version. 

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    Would this lengthen or shorten battery life? (Under the Eskom scenario when most of the time the batteries are not needed)
    Last edited by Jonatan; 2021/05/26 at 07:21 AM.

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    Default Re: A weekly timer on my battery charger - is this a mistake?

    I know very little about batteries but believe they must 'work' to keep fit.
    My inverter one powers lights every evening, gets charged by a tiny panel during the day and has lasted forever!
    There is no task too simple for some people to complicate !



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    Default Re: A weekly timer on my battery charger - is this a mistake?

    Quote Originally Posted by Jonatan View Post
    ... Victron have introduced a "storage" mode whereby the battery spends most time at 13.2 V, substantially less than the 13.6 to 13.8 most other people talk about. Victron does this with a timer . . . most time at 13.2 and then a short full charge once a week. But one battery going bad in the bank again stops the Victron Charger from dropping properly into float and storage mode ...
    You can set the voltages on Victron equipment you want it to bulk/absorb/float and all that.

    If you don't have Victron, re. the relay, clever idea.
    But what if it fails unbeknownst to you months later?
    If you planning on checking it regularly then you can also just charge the batt once a month, 2//3/4 months when you remember.

    My thing with batteries, if I've bought it, I won't let it die of old age. Will find a use for it between camping trip.
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    Default Re: A weekly timer on my battery charger - is this a mistake?

    Quote Originally Posted by Jonatan View Post
    My systems typically have the charger (360Watt) and inverter (1500Watt) as two seperate units. Inverter inputs are all 12V with a variable number of 12V batteries in parallel. Most typical is 3 X 105 AmpHr batteries and often 1 of these 3 batteries are removed while camping. Inverters typically draw 2 to 2.5 Amp switched ON with no load connected to output. We usually switch them off during the months that Eskom is coping - but some of us forget . . . .

    This is what I want to test:

    Click image for larger version. 

Name:	Clipboard01.jpg 
Views:	121 
Size:	108.1 KB 
ID:	616694

    Would this lengthen or shorten battery life? (Under the Eskom scenario when most of the time the batteries are not needed)
    These boards are ideal to set the lower and upper limit to switch on the charger via 220V. You thus use your own values.
    Attached Images Attached Images  

  13. #12
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    Default Re: A weekly timer on my battery charger - is this a mistake?

    Quote Originally Posted by ekkekan View Post
    These boards are ideal to set the lower and upper limit to switch on the charger via 220V. You thus use your own values.
    I have fiddled with those boards before but, being voltage based, they won't help to solve my question now. I want to know if I will do worse than a constant trickle charge if I take them off load and charge for 162 hours and then giving them a full charge cycle for 6 hours with a smart charger. If all batteries are good, that full charge cycle will drop to trickle charge within minutes. If there is a bad battery, the charger will hold the voltage at maybe 14.5 Volts for the 6 hours - but the timer is going to stop the charger from holding all the batteries at the high voltage all the time (only 6 hours on instead of 168 hours). Hopefully this gives us time to spot a bad battery and disconnect it from the pack.

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    Default Re: A weekly timer on my battery charger - is this a mistake?

    Quote Originally Posted by Jonatan View Post
    I have fiddled with those boards before but, being voltage based, they won't help to solve my question now. I want to know if I will do worse than a constant trickle charge if I take them off load and charge for 162 hours and then giving them a full charge cycle for 6 hours with a smart charger. If all batteries are good, that full charge cycle will drop to trickle charge within minutes. If there is a bad battery, the charger will hold the voltage at maybe 14.5 Volts for the 6 hours - but the timer is going to stop the charger from holding all the batteries at the high voltage all the time (only 6 hours on instead of 168 hours). Hopefully this gives us time to spot a bad battery and disconnect it from the pack.
    Why not buy a quality intelligent charger, hook it up and leave it on charge. Once every two weeks or month, then do a battery maintenance check... Common practice in the industry where batteries are used.
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  15. #14
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    Default Re: A weekly timer on my battery charger - is this a mistake?

    Quote Originally Posted by hunter26 View Post
    Why not buy a quality intelligent charger, hook it up and leave it on charge. Once every two weeks or month, then do a battery maintenance check... Common practice in the industry where batteries are used.
    That is exactly what I do when I live near the batteries. But, at my children's houses, and their in-laws, they have the quality intelligent chargers, and the only checking is done by myself when I might visit. On two occasions I have gotten there to find the intelligent charger at 14.7Volt, battling to charger one bad battery in the pack of 3. All three those batteries were then effectively on a non-intelligient charger for weeks or months on end.

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    Default Re: A weekly timer on my battery charger - is this a mistake?

    Quote Originally Posted by Jonatan View Post
    On two occasions I have gotten there to find the intelligent charger at 14.7Volt, battling to charger one bad battery in the pack of 3. All three those batteries were then effectively on a non-intelligient charger for weeks or months on end.
    The "joy" of using batteries in parallel. I prefer a regular load and charge test on each one at a time.
    14.7V is at about the switch to trickle.
    Last edited by ekkekan; 2021/05/28 at 01:31 PM.

  18. #16
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    Default Re: A weekly timer on my battery charger - is this a mistake?

    From Victron's "Energy unlimited" found at https://www.victronenergy.com/upload...limited-EN.pdf there is this paragraph (middle page 26):

    "instead of trying to find a delicate balance between insufficient voltage to compensatefor self-discharge and to much gassing at a higher voltage, it would be better to leave the battery opencircuited and recharge, depending on temperature, at least once every 4 months, or to reduce floatvoltage to a very low level, for example 2.17 V per cell (13 V respectively 26 V), and also rechargeregularly at a higher voltage."

    And then middle page 29:

    "For long periods of time the battery is left open circuited or float charged, in wintertime for example.As discussed in sect. 4.2.3, most flooded batteries will deteriorate quickly if float charged at 2.3 V percell for a long time. Ideally charge voltage should be lowered to between 2.15 V and 2.2 V per cell, orleft open circuited and recharged regularly. When the average temperature is 20C or less, at leastevery 4 months. At higher temperatures they should be recharged more often.From my personal experience and from numerous discussions with boat owners, I do also prefer toleave sealed Exide/Sonnenschein Dryfit A200 batteries or equivalent open circuited or on a lowerthan recommended float level instead of float charging them at 13.8 V, because, although in theory theycan be float charged during long periods of time, only too often the result was damage due toovercharging."

    This gives me hope for trying my timer . . . .
    Last edited by Jonatan; 2021/05/29 at 11:07 AM.

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    Default Re: A weekly timer on my battery charger - is this a mistake?

    Quote Originally Posted by Jonatan View Post

    "For long periods of time the battery is left open circuited or float charged, in wintertime for example.As discussed in sect. 4.2.3, most flooded batteries will deteriorate quickly if float charged at 2.3 V percell for a long time. Ideally charge voltage should be lowered to between 2.15 V and 2.2 V per cell, orleft open circuited and recharged regularly. When the average temperature is 20C or less, at leastevery 4 months. At higher temperatures they should be recharged more often.From my personal experience and from numerous discussions with boat owners, I do also prefer toleave sealed Exide/Sonnenschein Dryfit A200 batteries or equivalent open circuited or on a lowerthan recommended float level instead of float charging them at 13.8 V, because, although in theory theycan be float charged during long periods of time, only too often the result was damage due toovercharging."

    This gives me hope for trying my timer . . . .
    Good information.

    Although not in line with your timer design I wanted to indicate to perhaps get a 5/10A power supply. They are cheap and have a adjustable pot which can be set to say 13.2V and left connected all the time. After each discharge/loadshed then go for a full charge via the intelligent charger and then over to the power supply again.

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    Default Re: A weekly timer on my battery charger - is this a mistake?

    Quote Originally Posted by ekkekan View Post
    Good information.

    Although not in line with your timer design I wanted to indicate to perhaps get a 5/10A power supply. They are cheap and have a adjustable pot which can be set to say 13.2V and left connected all the time. After each discharge/loadshed then go for a full charge via the intelligent charger and then over to the power supply again.
    Thanks for suggestion. Okay for systems near me, but those 50 to 100km away are the ones I am trying to automate at least cost.

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    Default Re: A weekly timer on my battery charger - is this a mistake?

    These smart chargers can be permanently connected to your batteries.
    The voltage supply is current limited and will disconnect when it reaches fully charged state and then it repeats.
    The LEDs are simple to read so anyone can check if all is ok.
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  24. #20
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    Default Re: A weekly timer on my battery charger - is this a mistake?

    Methinks, a Optimate or a Victron charger, would solve the problem with ease.

    One bank prematurely aged, pays for the above.
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