Custom Charging settings for my AGM batteries -- let me know if I'm still too dim....

Re: Custom Charging settings for my AGM batteries -- let me know if I'm still too dim...

niel wrote: »

cdherman,
you can go off from the factory settings and it is advised that you do to configure better to the particular battery specs that you have. now keep in mind that the agm is a specialized lead acid battery and they sometimes can take up to 30%, but putting it at 20% or 10% is fine too. my agms can go several c, but most others seem to be about 20% tops and this may be good for you. also, do not eq charge your agms as that is a last ditch effort that could downgrade your batteries to achieve equalization. an extended absorb charge should be attempted first. i would enter the same number for volts in absorb and eq as you place for bulk. this prevents a voltage higher than you want there to be from occurring. this is important because agms are sensitive to overvoltage as that can cause vents to pop open and you'd lose water that you can't replace. 14.5v may be a tad on the low side being most of the time temps on batteries are a bit lower than 77 degrees f so i would guess 14.6v to be good for bulk, absorb, and eq. this is especially good is one can't disable the eq from occurring as it would then just automatically revert to an extended absorb charge. i would not go to the max of 14.8v and if you want higher than 14.6v then try 14.7v, but usually right in the middle suffices in most cases. if at any time the batteries are extra hot due to very hot weather you could lower the voltage back to 14.5v if you would like and for the record 14.5v does work too.

the same is true for the float as you will want something in the middle and my choice would be 13.6v, but you can go 13.7v too.

So let me see if I can repeat back what I think you told me would be acceptable:

Set Bulk phase to give 20%C till bat gets to 14.6V, then switch to absorption phase once threshold voltage of 14.6 is reached for 3 minutes. Absorption phase will hold voltage constant, and decrease A accordingly for 8 hours or untill A has declined to 1%C for 3 min, at which point the charger will switch to float.

I don't have to worry about equalization settings -- when the Xantrex has the bat set as AGM, equalization is disabled.

Now for the float phase. You suggest 13.6 or 13.7. What about the threshold? If I am understanding it correctly, the Prosine sort of floats in waves, allowing the charger to shut off completely till the lower threshold is reached and then charging back up to the max float phase voltage. Seems like the threshold should be set high enough to keep the battey happy, but not so high that the charger is constantly cycling on and off. I *assume* that a relatively LOW charging amperage is what is best during a float phase, but that is not what the default from Xantrex was set to do (200%C seems crazy).....

Re: Custom Charging settings for my AGM batteries -- let me know if I'm still too dim...

I got hold of Xantrex, now owned by Schneider it appears...

As to the function of their float. here is a VERY techy response that I think(?) I understood.

_____________________________________________________________________________________________

Max Current (%C)
The maximum available charging current (in A) as a percentage of battery
capacity (in Ah) for the Float charging stage.

During float mode, the charger is in Constant Voltage mode(13.4V default) and in a simple system the battery's acceptance of charge current (State of Charge) is actually what determines how much float current is being absorbed into the battery.
A 200Ah battery bank in good health will usually have a float current well under 10A so setting the charger's Max (output) Current %C setting to 200%C will not force excess current in to the battery. In this scenario, the charger will be idling along in 13.4V float operation at <10% of it's amp capacity.
Now, introduce a typical boat installation where there are other potentially high current 12V loads, boat winch, bow thruster etc which could easily demand an extra 30-100Adc from the battery system: when the Prosine is set to provide 200% of 200Ah it is essentially able to produce full charge power of 100A, and will support the extra DC load up to this 100A max while in float mode without significantly affecting the battery,
By contrast if you select a much lower Max Current %C setting such as 10%C(200Ah) or 20 Amps, the charger would only provide up to 20A total to support potentially a 30-100A load, therefore the difference must be provided by discharging the battery (unnecessarily).

If the charger is overwhelmed with a large parallel DC load during float and the load demands enough current from the battery to drop the system voltage down to the default 12.5V Threshold voltage/time out limit (defaults), the limits are intended to prevent excessively frequent repeat triggers into a new charge cycle, due to minor D.O.D which could result in excessive time spent at the higher absorption voltage for a battery still at 99.9% SOC. If you set the threshold voltage higher it will retrigger into a new charge/absorption cycle sooner. These set points and decisions are best described as a grey area of compromises rather than black and white,

• Max Timeout
This is the maximum amount of time that the charger will be in Float stage.

• Threshold Voltage and Timeout
When the battery voltage goes below this value for the Threshold Timeout
specified, the unit goes into Bulk charging mode.
Hope above helps .

Thank you
Best Regards,

______________________________________________________________________________________________


Soooo.. It would appear that the float max voltage set in the installer programming will set a fixed V for the battery that the charger attempts to maintain. Their decision to set the max amperage charge so crazy high reflects the design of the unit -- when in float, it is assumed that its got a shore power or generator working, AND that some uses of the unit include some high A draws directly from the battery at 12V.

I wish the documentation were better, but the reply from the engineer was top notch and occured less than 8 hrs after I contacted Xantrex/Scheider for their answer.

Cannot complain.....