House Batt Questions

[boowho]

OK, I think I may have finally figured out my out-gassing and electrolyte loss issues.

After cutting my charge rate on the Magnum to 50% I got rid of the out-gassing, but was still losing more electrolyte than I thought I should.

Based upon what I read on the batts themselves, I have a total of 464 amp hours on my stack.

The batt manufacturer recommends a C20 charge. So that means 464/20 or 23.2 AMPs max charge rate. The Magnum specs state a max charge rate of 70 amps. Dividing 23.2 by 70 give about 31 percent, so I have set my charge rate to 30%. This according to the Magnum manual.

The above was deduced from a careful reading of the battery specs and also the Magnum inverter manual. Can anyone poke holes in my reasoning? Herk, are you reading?

Finally, with a 464AH total stack capacity, does that mean I can draw 1 amp for 464 hours, or 464 amps for 1 hour or 2 amps for 232 hours and so forth? If not, what does it actually mean?

Thanks

Boowho??

[Joker]

To me, your logic seems sound (I'm a former engineer...civil though, not electrical!!)

Amp-hours would be a measure of the energy content of the battery. This was probably under ideal conditions in the manufacturers test lab on new batteries. But, it gives you a general idea of how much juice is in there.

I really need to get one of those upgraded charge controllers. I have the electrolyte and overflow problems sometimes.

[Joker]

Originally Posted by boowho

OK, I think I may have finally figured out my out-gassing and electrolyte loss issues.

After cutting my charge rate on the Magnum to 50% I got rid of the out-gassing, but was still losing more electrolyte than I thought I should.

Based upon what I read on the batts themselves, I have a total of 464 amp hours on my stack.

The batt manufacturer recommends a C20 charge. So that means 464/20 or 23.2 AMPs max charge rate. The Magnum specs state a max charge rate of 70 amps. Dividing 23.2 by 70 give about 31 percent, so I have set my charge rate to 30%. This according to the Magnum manual.

The above was deduced from a careful reading of the battery specs and also the Magnum inverter manual. Can anyone poke holes in my reasoning? Herk, are you reading?

Finally, with a 464AH total stack capacity, does that mean I can draw 1 amp for 464 hours, or 464 amps for 1 hour or 2 amps for 232 hours and so forth? If not, what does it actually mean?

Thanks

Boowho??

Just realized something...you are mixing amp-hrs and amps...

So if the max charge rate on the magnum is 70Amps per hour and the allowable charge rate is 20 amps per hour, you'd be setting it at the MAX rate for that battery. I'd back off the max a bit. Also, I'm only seeing how the C rating applies to discharge rates, not the charge rates. Another thing... These batteries are set in series and parallel, so the allowable charge rate may be double....gonna have to look into this a lot more or get someone with better electrical knowledge to sound off....Herk?!?

[BarryD0706]

Originally Posted by boowho

...
Finally, with a 464AH total stack capacity, does that mean I can draw 1 amp for 464 hours, or 464 amps for 1 hour or 2 amps for 232 hours and so forth? If not, what does it actually mean?

Thanks

Boowho??

There are a couple of things wrong with your numbers. The biggest thing is that you never want to discharge your batteries by more than 50%, so you only have ~232 amp-hours of usable capacity.

Secondly, the amp-hour rating is measured using a specific current, often 20 amps. So if you're drawing 20 amps, you can use 20 amps for 11.6 hours (=232). If you draw less than 20, you get higher capacity. If you draw more than 20, you get less capacity. This is called the Peukert Effect.

[Great Horned Owl]

Originally Posted by Joker

Just realized something...you are mixing amp-hrs and amps...

So if the max charge rate on the magnum is 70Amps per hour and the allowable charge rate is 20 amps per hour, you'd be setting it at the MAX rate for that battery. I'd back off the max a bit. Also, I'm only seeing how the C rating applies to discharge rates, not the charge rates. Another thing... These batteries are set in series and parallel, so the allowable charge rate may be double....gonna have to look into this a lot more or get someone with better electrical knowledge to sound off....Herk?!?

As a retired electronics engineer, I'll chime in. Talking about amps per hour doesn't mean anything. The current (usually measured in amperes) is a measurement charge flow per unit time. The ampere is defined as a charge flow rate of one coulomb per second.

As an analogy, we measure water flow in terms of gallons per hour. We just haven't assigned a name to the unit. Talking about amps per hour is like talking about water flow in terms of gallons per second per hour.

Joel

[garbonz]

A battery is typically rated in AMP-Hours based on testing at standard temperature and at a discharge time of 20 hours. Your 464 AMPHour stack will produce 23.2 amps for 20 hours before dead. Peukart's law says that you will have more than 464 amphours at lower discharge rates and less at higher. As mentioned, usable amphours are limited if you expect the batteries to last. Charging rates can be higher than the 20 hour rate but are dependent on battery temperature, and voltage. That is why a multi stage charger is need for precise control of the charge cycle. Excessive gassing is almost always caused by an over charge condition after the battery is full or close to full by going over 14.4v for to long a period, or over 13.7 volts in "float". At face value, I would be worried about the float voltage your charger is putting out as the possible cause of your outgassing and electrolyte loss. That will not be effected by your setting the max charging current.

IMO

[Joker]

Originally Posted by Great Horned Owl

As a retired electronics engineer, I'll chime in. Talking about amps per hour doesn't mean anything. The current (usually measured in amperes) is a measurement charge flow per unit time. The ampere is defined as a charge flow rate of one coulomb per second.

As an analogy, we measure water flow in terms of gallons per hour. We just haven't assigned a name to the unit. Talking about amps per hour is like talking about water flow in terms of gallons per second per hour.

Joel

Right, that's kinda my point. One is a flow rate, the other would be a volume (or total amount of charge that the battery could deliver).

But apparently you can get more total coulombs out of a battery if you draw it out more slowly -- that I kind of knew intuitively, but didn't realize was a real documented phenomenon.

Probably some reverse effects are in play too, if you try to cram too many coulombs too fast into the battery (amps). So, slower rate, longer time probably equals more coulombs total that you can in effect push back into the battery?

Never really liked this invisible engineering

[Joker]

Thanks garbonz. I'll investigate that too.

[boowho]

Originally Posted by Joker

Thanks garbonz. I'll investigate that too.

And thanks to all for the responses; some interesting reading.....

One thing I found especially interesting is "Peukert Effect". Apparently it indicates that the Amp Hour rating of the stack is not "linear" across the board (as I mentioned in the OP), but only at a specified rate of discharge (typically 20 amps).

Also, as far as only drawing the stack down to 50%, aren't these batts specified as "deep discharge"? Or does that mean something else??

Boowho??

[BarryD0706]

Originally Posted by boowho

...
Also, as far as only drawing the stack down to 50%, aren't these batts specified as "deep discharge"? Or does that mean something else??

Boowho??

50% IS "deep discharge". You'd never want to take a "starting" battery down anywhere close to that.

[boowho]

Originally Posted by Joker

Another thing... These batteries are set in series and parallel, so the allowable charge rate may be double....gonna have to look into this a lot more or get someone with better electrical knowledge to sound off....Herk?!?

Just to clarify, my stack is four 6 volt 232 AH batts connected in the usual series/parallel arrangement. And yeah, where is Herk when you need him??


Boowho??

[boowho]

Other than voltage, what is the difference between bulk, absorb and float charging (if there is any difference)? My control panel shows float charging but the charging amps are showing right at 21 which is what I expected for a max charge. I thought float was the same thing asl "trickle" charging.

Thanks

Boowho??

[BarryD0706]

Originally Posted by boowho

Other than voltage, what is the difference between bulk, absorb and float charging (if there is any difference)? My control panel shows float charging but the charging amps are showing right at 21 which is what I expected for a max charge. I thought float was the same thing asl "trickle" charging.

Thanks

Boowho??

Yes, no difference other than voltage in the various modes. That does seem like a high current for "float". I suggest testing the voltage to see if it's "in spec" for float mode per the charger documentation.

[NV245]

www.solar-electric.com › ... › Deep Cycle Battery Information and FAQ

check information here may help

[garbonz]

Originally Posted by boowho

Other than voltage, what is the difference between bulk, absorb and float charging (if there is any difference)? My control panel shows float charging but the charging amps are showing right at 21 which is what I expected for a max charge. I thought float was the same thing asl "trickle" charging.

Thanks

Boowho??

The float is just that. It floats the batteries at about 13.7volts with only enough current (amps) to offset the draw from the system. Do you have 21 amps of 12 stuff running? Thats a heck of alot of current, unless you gots all the lights on, furnace etc etc. Turn everything that is 12 volts off and see what you get. It should only be a few 10ths of an amp if the batteries are already charged.