12.5K gen Floats too early

[Moira]

Hi guys,

I have the onan 12.5k on my 2003 Signature and the 2500 pure sine Xantrx inverter. I can run the generator for hours and it never tops off my batteries. I have 4, 6volt golf carts, 220 ah in parrell and series.

The inverter causes it to go to float about 90% or 50 AH from full. I called xantrex we did all kinds of things to the inverter, reset it, changed the absorption time, increase charging ac amps, and other stuff. I dont have my notes with me. I dont have cell service where we are now.

And I am wondering does anybody else have this problem? I use the lifeline temp chart to set the bulk and float according to the outside air temp. It doesn't sound like a lot but with a DC frig and the TV going I really need that 50 amps.

thanks guys
my reply may be delayed.

[twinboat]

4, 6 volt batteries will be at least 400 AH of capacity.
Do you have the inverter setting to that ?

That last 10% of charge probably isn't going to happen in a few hours, you may need 10 hours to get to 100%.

Solar will help during the day or high capacity batteries will give you that extra AH.

[Moira]

Thank you twinboat,

No my inverter does not have a setting for the battery bank capacity.

I guess I can stop worrying over it then. I only have 40% power not 50%.

I did install 1200w solar last year and it's doing good so far. But I will see how much it will charge up on this trip.

I have looked into relocating the house batteries to add 2 more.. But because all cables must be the same length, they all must go in the bedroom somewhere, that is not acceptable. So when I go for new batteries, I'll get 4, 250 ah or whatever I can fit in the small bay. Tbc

[vsheetz]

How determining 90% and 50AH short of full charge?

What is the absorption time set to? Or if using tail current, what value or percentage?

[Ivylog]

Fortunately you do not have the 2012 MSW inverter my 04 Dynasty has as it’s 100A charger will only put out 60 A on generator power and 75A on shore power because the fine print has the 100A at 130V... Truth in advertising??? Instead of replacing the POS, I added a $200 100 A smart charger giving me 150 A initially. After 45 minutes I’ll turn the 100A off briefly to trick it into putting out 100 A again... it’s powered by the block heater outlet. In another 45 minutes I’ll turn the Zantrex off so I get 75+ A out of the smart charger... the Ztrex is making it look like the batteries are full.

Your solar should get you to 100% BUT only if you run the generator bulk charging for an hour in the morning. Even with 1200W you’ll rarely see more than 40-50 A. If you know you’ll have a good solar day, more than 60A you can cut back on the morning generator time. You’ll find you need to run the generator any time you use a high amp item like making coffee in the morning.

PS: I would not worry about equal cable length... just use larger cables than what the chart calls for.

[Moira]

Originally Posted by vsheetz

How determining 90% and 50AH short of full charge?

What is the absorption time set to? Or if using tail current, what value or percentage?

I have a trimetric battery monitor. When I am on shore power for awhile, my percentage goes up to 100% and zero AH from full. As I use power, the trimetric counts down from the full ah I had. I also can reset it to 100% while on shore power just to make sure it is zeroed out. It has been pretty accurate. Checking the AH from full compared to the percentage comes out accurate for a 440 AH battery bank.

The absorption rate is at 2 hours now. I dont know what tail current is.

[Moira]

Ivylog,

That was a little confusing for me. But I understand about the xantrex thinking the batteries are full when they are not. I am not sure but I think my generator is rated at 50 amp ac. When it kicks in, I have seen the charge go up to 80 amps dc on the trimetric. But then it slowly backs down. After a discussion with the guy at lifeline, we set the max charge rate on the inverter to 18 amps ac.

The xantrex lady said that they no longer support my model and they are not interested in updating the software.

So when I have the generator on, does the solar and generator work together or is the generator backing off due to good solar amps.

ps I got a DC conversion nor cold frig in last season.

[twinboat]

Were are you getting the " all cables must be the same length " from ?

All the same length may be the optimum setup, but its not a steadfast rule that they all have to be.

If you cable them with heavy enough gauge wire to cover the voltage drop, they can be different lenghts and even in different locations..

There is only one article that I'v seem on this site that says they must be equal length, but the data is skewed.
They are using cables designed for the maximum current of their test and of course drawing that same maximum current.

If you investigate cable sizes, you will find, that even with everything on, you will not be anywhere near your battery cables maximum capacity.

If your inverter is inverting at maximum capacity and drawing 400 amps, with 2 series sets, that 200 amps each. Add another series set and your down to 133 amps per set. Run 4/0 cables 6 feet and the voltage drop will be less then a tenth of a volt. During recharge, it will be less, and the batteries will equalize.

As far as only having 40% battery capacity, that's not quite true either.
Its a suggestion that you only use 50% of your banks capacity, not a rule.

You will get about 1000 deep cycles from your bank, only using 50%. You will get about 500 deep cycles using 90% of your capacity.

Using more then 50% of your capacity isn't detrimental, especially if your only using 10 or 20% more, it just counts against the cycle life.

FROM Lifeline:
" In general, batteries should be sized such that the rated capacity is at least twice the capacity

required by the load. For example, if 100 Ah is required on average, select at least a 200Ah

battery. This approach will limit the average depth of discharge to 50% and will dramatically

extend the life of the battery (see chart of Cycle Life versus Depth of Discharge in Appendix C) ".

This is from the Lifeline battery maintance manual.

[Moira]

I got the equal battery cable length from a google search. The context was dealing with recharge rather than loads. Unfortunately I cannot provide a link at this time because the internet here is non existent. I wanted to take out the chassis batteries and add 2 more house batteries in that bay but read that unequal cable lengths between the upper 4 batteries and the lower 2 batteries would not work. So there is no other room for them, other than putting all six in the bedroom. (moving the 2 chassis batteries to the engine compartment)

So tonight with the oat at 80*, I increased the float charge on the inverter to 13.7 which helped out a little bit but the charge still eventually went down to 7 amps. And I am still 100 amps from full.

The inverter menu is a bit confusing because it is using AC. While the trimetric is in DC. So the max charge rate lifeline told me to put in was 18 amps ac. I could increase that to maybe 20 amps ac. But other than changing the bulk rate, the float charge and absorption time, I have no other control over the charging process of the inverter.

[richard5933]

If you only have 440 Ah of battery capacity, then a charging rate of 40-50 amps is more than adequate. Trojan (our battery manufacturer) recommends charging at about 10% of total capacity, and I'm sure that your battery manufacturer has a similar number.

Possibly the way you're tracking the input/output from your batteries is at fault. We use a separate battery monitoring system (Victron BMV 712) from our charging system, so it's easy to see clearly the situation. The important thing is that EVERY load in the system has to have the negative side run through the shunt on the monitor - any negative connection to the battery which bypasses it will cause an inaccurate reading.

I think that the problem is your expectations though. Charging systems are designed to run at the higher voltage for only a set period of time and not until the batteries are at 100%. If you did this, you'd experience a high water loss and have to continually add water.

My smart charger puts out 70 amps max and is charging a 780 Ah battery bank. The manual says that it will charge at 'bulk' rate of 14.4v for about 8 hours, and then drop to 'normal' mode with a voltage level of 13.6v and it will stay at that level for another 24-30 hours. After that the voltage drops to the 'float' level of 13.2v, enough to keep things from discharging but not enough to cause water loss.

The amps flowing to the battery will drop as the batteries near full charge. The batteries pull the amps only as they need it, and it is normal for the amps to drop as the charge level gets higher.

One of the reasons that it's so hard to fully charge batteries on a generator is the length of time necessary to run through a full cycle. This is where solar comes out ahead - you can use the generator to run through the more power hungry early phases of charging and then switch over to solar to finish the job.

[twinboat]

Originally Posted by Moira

I got the equal battery cable length from a google search. The context was dealing with recharge rather than loads. Unfortunately I cannot provide a link at this time because the internet here is non existent. I wanted to take out the chassis batteries and add 2 more house batteries in that bay but read that unequal cable lengths between the upper 4 batteries and the lower 2 batteries would not work. So there is no other room for them, other than putting all six in the bedroom. (moving the 2 chassis batteries to the engine compartment)

So tonight with the oat at 80*, I increased the float charge on the inverter to 13.7 which helped out a little bit but the charge still eventually went down to 7 amps. And I am still 100 amps from full.

The inverter menu is a bit confusing because it is using AC. While the trimetric is in DC. So the max charge rate lifeline told me to put in was 18 amps ac. I could increase that to maybe 20 amps ac. But other than changing the bulk rate, the float charge and absorption time, I have no other control over the charging process of the inverter.

The max charge rate, in AC, is a setting so that you don't trip out the incoming AC power, not the DC charging.

There should be a DC charging rate setting based on a % of the inverter/chargers max amp output. If you have a 100 amp charger, and only want a max rate of 80 amps, you would set it at 80%, but Lifeline had no maximum.

There is no voltage setting in bulk mode. The charger will output max set amps UNTIL the battery reaches absorbsion voltage, 14.?
Only then does the charger become a constant voltage charger and will taper off the amp output to maintain the absorbsion voltage. At that point, the max amp setting doesn't change anything, except if set to low. If the voltage was allowed to keep climbing, it would damage the batteries.

Just a question, is the solar negetive cable on the RV side of the shunt ?
If its on the battery side, then its input is not being measured. Batteries could be higher then shown.

Don't lose any sleep looking for the " even cable length " recomendation, its not critical in your installation. Your cables should be sized for 400+ amps of discharge, your much less re-charge amps will not send the batteries out of equalization.

Download the Lifeline Maintance manual and read about charging them.

[twinboat]

Originally Posted by richard5933

If you only have 440 Ah of battery capacity, then a charging rate of 40-50 amps is more than adequate. Trojan (our battery manufacturer) recommends charging at about 10% of total capacity, and I'm sure that your battery manufacturer has a similar number.

Possibly the way you're tracking the input/output from your batteries is at fault. We use a separate battery monitoring system (Victron BMV 712) from our charging system, so it's easy to see clearly the situation. The important thing is that EVERY load in the system has to have the negative side run through the shunt on the monitor - any negative connection to the battery which bypasses it will cause an inaccurate reading.

I think that the problem is your expectations though. Charging systems are designed to run at the higher voltage for only a set period of time and not until the batteries are at 100%. If you did this, you'd experience a high water loss and have to continually add water.

My smart charger puts out 70 amps max and is charging a 780 Ah battery bank. The manual says that it will charge at 'bulk' rate of 14.4v for about 8 hours, and then drop to 'normal' mode with a voltage level of 13.6v and it will stay at that level for another 24-30 hours. After that the voltage drops to the 'float' level of 13.2v, enough to keep things from discharging but not enough to cause water loss.

The amps flowing to the battery will drop as the batteries near full charge. The batteries pull the amps only as they need it, and it is normal for the amps to drop as the charge level gets higher.

One of the reasons that it's so hard to fully charge batteries on a generator is the length of time necessary to run through a full cycle. This is where solar comes out ahead - you can use the generator to run through the more power hungry early phases of charging and then switch over to solar to finish the job.

Your setting and charge rate are for flooded batteries. Max charge rate about 10 to 15 % of capacity.

The OP has AGM batteries. They have a higher charge rate, and that depends on the manufacturer.
Lifeline recommends as high a bulk charge as you can supply.

[153stars]

You are also using power in float mode does is get calculated perfectly. If you stopped charging the batteries after bulk they would stabilize lower as well kind of math vs chemistry vs perfect world issue.
Niche that solar and inverter gens. help fill when you don't need multiple ACs running.

[Moira]

Originally Posted by richard5933

Possibly the way you're tracking the input/output from your batteries is at fault. We use a separate battery monitoring system (Victron BMV 712) from our charging system, so it's easy to see clearly the situation. The important thing is that EVERY load in the system has to have the negative side run through the shunt on the monitor - any negative connection to the battery which bypasses it will cause an inaccurate reading.

I think that the problem is your expectations though. Charging systems are designed to run at the higher voltage for only a set period of time and not until the batteries are at 100%. If you did this, you'd experience a high water loss and have to continually add water.

Yes I do have AGM batterries so there is no water issue. And I do have a trimetric which is like your independent battery monitor. It is on the proper side of the shunt. thank you