How is the generator charging the batteries? Inverter/charger
If it is charging through an inverter/charger or battery charger what make, model and amperage rating? Xantrex Freedom 20
You mentioned the word "idiot lights" and the older Freedom chargers could not be any more "idiot" if they tried. Your charger is not as "smart" as you think it is
and usually the absorption charge (time spent at target voltage) is far too short. Without a Link remote these (we need to know what remote you have
) chargers simply default to what amounts to "kitchen timers
". With the standard remote the Freedom 20 will only do 1 hour of absorption when set to Flooded or AGM and only three hours when set to GEL. Alternatively if the batteries drop to less than 10A acceptance they can switch to float before the egg timer
has run out. It is critical that your charger is set to GEL if you are charging GEL batteries.
What is the charge voltage of the batteries? I'm not exactly sure what you're asking. Do you mean the Bulk charge rate? When I press the voltage button on the SmartGuage during bulk, it said 14.something. Will have to confirm.
Bulk = Constant Current; Bulk it is not a "voltage limited
" stage of charging it is full bore from the charger with the battery voltage slowly rising to the absorption set point.. If you have a 100A charger then it *should be
pumping out 100A (bulk) until the battery voltage rises to 14.1V (GEL absorption voltage). *Many older inverter chargers can not develop full charging output when run off a generator as they can be a bit intolerant of the input from a generator. If yours can only develop 70A, and you are doing the mental math on 100A, then you will be frustrated with charging speeds. Once target voltage has been attained (GEL = 14.1V) the current
will begin to cut back as voltage is held steady and SOC rises.
This article, despite being about faster charging AGM batteries, may help explain it a bit further:
How Fast Can an AGM Battery be Charged?
What is the voltage drop at full charger output between the charger or I/C and battery bank terminals? Don't know, not sure I know how to check. Given that the SmartGuage is attached direct to the terminals, does it give the reading?
When the charger is pumping out 100A you need to measure terminal voltage, with a DVM, at the charger end of positive & negative then at the battery end. The best way is to measure the voltage drop of the positive cable & then negative cable but most folks don't have DVM test leads that will reach from the I/C to the battery bank.. There will always be some VD, but too much can dig into your charging speed and cause the charger to hit absorption, and start the timer
, before the batteries ever obtain the proper target voltage..
What brand and model are the batteries? It was a quality brand, but can't recall off the top of my head. They are Gel batteries. Four group 34, I believe.
If they are quality GEL batteries such as a Deka or Sonnenschein (Prevailer) then use the GEL charge setting.
How old are the batteries? Three years
At three years old they likely have a fair bit of sulfation. A good way to tell how much is by how fast the charging voltage rises to 14.1V from 50% SOC. Your charge rate is .25C (25% of 400Ah) if the charger can develop all 100A off your genset, so from 50% SOC the charger should be in bulk/constant current for approx 45 minutes to 1 hour before the batteries attain 14.1V. If the charger turns on at 50% and the battery voltage climbs to 14.1V quickly (eg: less than 35-40 minutes & don't forget about voltage drop) then the batteries are sulfated and charging will simply take longer than it will with healthy batteries.
The math would look like this
400Ah bank at 50% SOC = -200Ah
1 hour of bulk at 100A = -102Ah or approx 75% SOC
At about 75% SOC your batteries should be at, or approaching, 14.1V (dependent upon state of health) and from here to 100% SOC charging gets slower and slower and slower....
From 50% SOC (on SmartGauge) how quickly do they attain target voltage eg: how quickly do they reach 14.1V (typical GEL absorption)? Not sure how I would know this. The idiot light, on the Xantrex panel, took hours. But, the charge rate dropped along the way and the idiot lights saying in float, when the SmartGuage says no where near the upper 90% of charge.
Ignore the idiot
lights on the charger! All they are telling you is what the charger "thinks
" it should be doing and this may be grossly incorrect and usually is especially with "egg-timer
" chargers... Do you have a volt meter on-board? If you know your target absorption voltage is 14.1V we need to know how long it took to get there from 50% SOC. If this climb in voltage happens quickly
that means the battery health is not good..
What is the max charge current when you first fire up the charger? Is this the 14.something you asked above?
Voltage is voltage, current is current. We need to know if the charger can actually develop it's 100A rating running off your genset. Many can't so this number is important to know. Yopu would need an ammeter on-board or a DC clamp meter capable of measuring DC amperage to at least 100A. These are pretty inexpensive these days and are something every boater should own..
I grabbed one of these for a customer and he loves it. They can be had for less too but this one has a lot of good features.
UT207 AC/DC Clamp Meter
How long does full output current last? If you're asking how much time I get from the 400ah bank, before reaching 50%, that's about two days, with two fridges running, electric heads, plotters/radios running 4-5 hrs per day, pot of coffee off the invertor, lights, etc. Of course, the engine runs in/out of the harbor for a short bit.
I am asking how long the charger remains delivering its 100A rating for when started up at 50% SOC.
Bottom line is you're far better to trust the SmartGauge and to ignore the idiot lights. The idiot lights are NOT based on your battery actually being full
before switching to float. Switching to float too early, a phenomenon I call "premature floatulation" only serves to dramatically extend the time it takes to fully charge your batteries. At the dock, no big deal, but when running a genset premature floatulation
leads to slow charge performance..
Look at the SmartGauge each morning before charging
and in the evening before bed. Don't focus on it while it's charging. Once you stop charging it will hone in on SOC.. The longer you use it the better it knows your bank and the faster after charging it will hone in on a more accurate SOC....