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200ah gel battery protection

Chris Kitson

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Good morning clever people. We got my (old) parents a simple load-shedding kit in a box that consisted of a 1000w inverter and a 105ah deep cycle battery just to operate their tv and decoder. We are swopping the 105ah deep cycle for a 200ah gel to allow for longer viewing. Im petrified of over charging and there is no alarm to say when the battery is full or getting empty other than the small screen on the inverter. 

My question, is there a small and simple bms, charge controller or alarm that I can easily add to assist with the management of the battery?

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Care to share who sells these?


It looks like a normal inverter, which means that all it does is DC to AC and AC to DC (For batteries) and that's basically it, as far as I know you cant program these and need a charge controller.

If it was ONLY for tv, decoder and wifi, it would have been an even cheaper option to get a battery, charger and feed DC directly to the TV and Decoder through new power connectors, since they are in essence DC appliances.


I guess this would work for what you need? But his is for 100ah only max, so you need a bigger one



Inverter power in from battery

Battery power in from Charger

Charger power in from Mains



Or something like this, don't know the AH capacity, although I don't really see how this plays a role, I mean if you set your charge settings it will keep charging until it reaches that voltage range, the ah in my eyes has nothing to do with it? - Maybe some smart people can come enlighten me as to why any charger has a ah limit, like between 100ah and 200ah?

Dont know if below will work, so again some more informative people to chime in, but from what it looks like, might be fine.




Edited by Eurard
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With a quick search I have found various suppliers that sell this Fivestar FS-1006 but nobody gives the specifications where one can see what the internal charger is capable off.  So we are in complete darkness to it's operation.

Just about all lead acid chargers are sold for occasional car battery charging, intended for slow and loooong charging cycles of typically 10 hours or longer.  With our current rate of L/S this is obviously not practical.  Also, these chargers are not designed for UPS-like charging that requires constant monitoring and re-enabling of the charge process.  For a car battery application, the charger assumes the battery reaches a full charge and is then returned to normal operation.  So these so-called intelligent chargers might, or might not, re-enable cyclic charging.  In other words, charging might not be automatic and require user input.  I.e. switching the charger off and then back on again.

There are cheap battery management systems like this one https://www.robotics.org.za/XH-M602?search=battery charger but I regard them as completely useless.  A device like this would switch the charger off at the START of stage 2, top-up charging, so the battery would never see a full charge.

I think that over-charging is very unlikely in current SA.  Let's assume you have a 100Ah battery which you discharge to 50% DOD.  That means you need to replenish more than 50Ah (the battery has losses which get burned as heat, so you need to put more in than what you get out).  Most chargers can do no more than 8 or 10A, so it would take about 7 hours to recharge.

It is sad not to know anything about that internal inverter charger.  One could measure the charge current but if it's more than 10A it would blow a multimeter's fuse as they are all maxed at 10A.  Whatever that internal charger can do, with a 200Ah battery, things will get twice as slow.  So I predict that you are more likely to severely undercharge your battery which would be a killer for a lead acid.

There are really not any easy solutions for this.  @Eurard mentioned this link: https://www.takealot.com/12v-10a-pulse-repair-lcd-battery-charger-for-car-motorcycle-agm-/PLID90409460  This is sold as a 10A charger but it is NOT 10A.  I know, because I have one.  This is a 6A charger.  I think this manufacturer does make a 10A version, but it seems that those sold locally, or at least on Takealot, are all the 6A versions that are wrongly claimed to be 10A.  Because these are quite cheap, you could consider trying one of and run it in PARALLEL with the inverter's internal charger.  Especially if you are going to switch to a 200Ah battery.  The Takealot charger actually displays the battery voltage and the charging current, so the voltage indicator could be used to oversee what is going on.  You can even leave this charger connected to the battery but not power it from AC and then use it as a voltmeter.

Note that the above mentioned charger has no AC input filter and produces switching noise that I can hear in my PC speakers whenever the unit is on.  This happens as long as it is charging.  Once fully charged it will display "FULL" and the noise stops.  The unit also has a small fan, but it is not loud.

The problem with all these cheap solutions is that they have never been designed for, or intended to be used on a semi-continues level.  These systems are OK for a 5 day camping trip, but not everyday use. 

Also note that you cannot buy any battery charger that claims to be compatible with 20 to 100Ah but fails to specify the charging current.  Such a marketing statement is totally useless.  If a manufacturer cannot even specify the charging current of their device, the only place for such a product is inside the trash-bin.

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Just to shed some light on these great China pulse chargers. The amps that they provide is like 10A pulses but when we measure the current we get a average just like reading a PWM output. 

The constant pulses during charging is good to prevent sulphation. 

There are many chargers of over 8-10A. See some below. 




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If I reply to someone's needs, I will consider the overall picture.  A person with a flat on a bicycle will not be interested in a 3-phase compressor. @Scorp007 You can buy 50A and 100A battery chargers as well.  Professional equipment that will most likely cost 25K and up.  Those chargers you conveniently show with the manufacturer label cut-off are Victron products.  The 12V 20A charger is  about R 3000.  You surely don't expect people that brought a 1000W modified sine wave inverter that is advertised at about 2K to buy a battery charger costing 3K, to be used on lead acid batteries.  Jy is nou besig om die dam onder die eend uit te ruk.   🙈🙉🙊

Not everyone can afford to drive a Porsche.  And then you get people WITH the money who would never agree to such extravagance either.  I am not impressed with a car manufacturer that builds good cars costing 5 million.  What impresses me is a manufacturer that can build a damn good car for 250K.  THAT takes skill.

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