# How long to charge? Float stage.



## canfossi (Sep 18, 2005)

I have a 48 volt PV system, when charging up my batteries when they are low how long should I let the generator run for once it's reached the float stage for optimum battery health? Also, the generator is a 3000W Honda, sometimes, though not always, when I am charging the batteries and the well pump comes on, the fuse blows on the generator (it goes into overload) and I have to restart the generator? What's causing this? The solar company the put in my system recommended this size generator and they are reputable. The gen usualyl works fine without blowing the fuse. Thanks Chris


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## Jim-mi (May 15, 2002)

How or what are you charging the batts with . . ??

Float voltage is where you would leave the batts . . .forever . . . (well almost) . . . 
At that point you are putting very little into them . . . your just maintaining them at that -"good for the batts"- level.

Well pump-charging- breaker trip . . . . Thats just plain an overload on the genny.
Simple solution . . . . . .do one or the other.

Slamming the genny with that much overload . . . .Not good for its "long life"


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## canfossi (Sep 18, 2005)

I am charging the batteries up with the generator mentioned when the batteries are low and it's cloudy. Chris


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## artificer (Feb 26, 2007)

Are you using the 12V output on the generator to charge the batteries? What size well pump do you have. 110, 220, or 12Vdc? If you have a separate charger, how many amps is it putting out?

If your well pump is larger than 1.5hp you might have to get a soft start kit for the pump. If the pump is DC, and you're running it on the 12V output of the generator, you need to get either a battery charger or converter to run either the charging or well pump off of the 110 circuit.


My Xantrex inverter/charger will put out 75 charging amps. Thats 900 watts. Thats a significat portion of the generators capabilities. (I'm running a Honda 2000ei) If you have the same situation, It makes sense that you're overloading the generator. If the generator is overloading while the charger is in float mode, then thats a different story. It shouldn't be drawing that much.

You need to get a meter to see how much current the well is drawing at startup, as well as the charger.

Another problem can be the EcoThrottle. The engine speed is slow on the trickle charge, and can't get up to speed fast enough to provide full power before the breaker trips. Try running it with the EcoThrottle set to off. If the pump comes on randomly as its used, this doesn't help, since you really want the economy of the EcoThrottle. It can help in the diagnostics, however.


Artificer


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## Michael Kawalek (Jun 21, 2007)

My deep well pump is 240VAC and I would consider 5000W too low. For my pump I wouldn't use a generator that didn't have at least 30amps of 240VAC. It sounds like clearly that you are overloading the generator with both loads. You can either get a bigger generator, or make sure that one load is turned off before running the other.

By the way, I read in one alternative energy book that chargers work inefficently with lower powered generators, because only a certain fraction of the AC waveform at peak voltage was utilizable for charging current. I don't remember though way that is. I do remember that a significantly larger than expected generator was recommended for battery charging, so maybe a 5kw or larger generator is the way to go!


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## zant (Dec 1, 2005)

Gen is too small....if you have a Trace inverter,see what the HZ is while charging batteries.I'd bet about 55-56,not good-then your well pump kicks on and the gen is trying to power both at probably 51-52HZ-even worse so the fuse trips to save alternator.......Reputable or not I have found many solar people always go for the low end gen size....My home had 8kw diesel with Honda 5000watt backup gen and the Honda would not power bat charger and household needs for the first 2hrs of bat charging if they were low.GEnerally the 60HZ is only seen below 7-8amps of draw..


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## Jim-mi (May 15, 2002)

Must add; You said the installers recomended that size genny.
Fine.
For doing one thing at a time

Another way . . . . .flip the breaker to the well pump OFF when you feel like the batts need a good charging . . . . . .


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## canfossi (Sep 18, 2005)

I flipped the generators eco-switch to off while charging this time and when the well pump did come one things were fine, nothing tripped. I would like to get a biger gen but the funds aren't there right now, maybe in the future. Thanks Chris


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## Ed_Stanton (Dec 28, 2004)

I don't think that there is a perfect answer to your float time question. Your inverter and battery manuals should offer suggestions specific to your set up? Perhaps this article will answer some of your questions about battery charging?

http://www.backwoodssolar.com/newsletter/pdf/SUMMER 2007 NEWSLETTER.pdf

I would think that with a PV (solar panel) set up, it might be helpful to use the sun to run the Float stage of your charging rather than using the generator, unless of course there is no sun when you're charging. Also make sure that your charging set points are not too low and as per the article, consider increasing your Float Charge set point, both from the generator and the solar panels if it's presently low. Your inverter / charge controller will monitor these set points and hold the charge as per whatever time that you input for the 3 charging modes (Bulk, Absorption and Float). 

There are many variables to consider regarding Float charging, such as battery age, how far down you draw the batteries on a regular basis, charging temperature of batteries, is there a temperature sensor on the batteries and is it tied into your inverter/charge controller, general specific gravity of the battery cells after Bulk charging and after your present Float charging methods, etc.. Generally, go by the SG of the battery cells and if it's still low after a Bulk charge, then make your Float Charge longer (and at a higher set point). Again, if it were me, I'd try to use the solar panels to run the Float charge for at least a few hours. If I use my 7.5 KW generator, and with how I run my system, charging routine and use my batteries, I run the Float charge for about an hour, but I also have fairly high set points for Bulk and Absorption charges, so these are fairly long times. I don't know what your system set points are, what inverter or charge controller that you're using, or what your battery cell Specific Gravities before and after charging are to better suggest something (nor am I really knowledgeable to be doing so). I think that these things are more important than the generator or length of time. The sun via your solar panels is your best generator anyway, though any generator will work. The length of time required for float charging (charging in general) will be determined by the specific gravity of your battery cells after charging and over the time of their use.

From my experience, to figure out the right length of time for your system, it is best to go by the Specific Gravity of your batteries. If it's generally low, then charge longer. One problem with the TriMetric meters, is that they only really read voltage of batteries which isn't a complete story of battery charge or overall health, but just a snapshot of voltage at a particular moment. Also get used to monitoring the voltage AND the Amps being drawn over time (Amp Hours used (amps drawn over time) is very helpful as a guide for use rather than just the voltage display or the % indicator (% changes with battery age and health and will be inaccurate anyway unless the amp capacity of the batteries is also changed in the meter, but which is VERY hard to accurately determine, especially for used batteries, so IME, following the % meter indicator is not a great idea, vs. voltage or Amp Hours). Download the TriMetric manual and while complex at first, it is a very good guide on how to accurately use it as a "guide" or fuel gauge estimate. But Specific Gravity measurements are really THE best indicator of battery status and health and should be taken often to really know your batteries.


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