Recharge time's for Trojan L16REB deep cell batteries.
90cummins
Solar Expert Posts: 57 ✭✭
I recently placed my order for a Xantrex XW4024 and 4 Trojan L16REB batteries and have been looking for info on recharge times.
Is there a guide or rule of thumb for recharge times based on DOD and battery capacity?
I have looked in Trojans website and done various searches but found nothing.
Thanks
90cummins
Is there a guide or rule of thumb for recharge times based on DOD and battery capacity?
I have looked in Trojans website and done various searches but found nothing.
Thanks
90cummins
Comments

Re: Recharge time's for Trojan L16REB deep cell batteries.
You will need to get a hydrometer and set a baseline charge when new. I think it was Trojan that has you establish a commissioning charge as well.
That is the only real way to tell how they are doing over time. 
Re: Recharge time's for Trojan L16REB deep cell batteries.I recently placed my order for a Xantrex XW4024 and 4 Trojan L16REB batteries and have been looking for info on recharge times.
Is there a guide or rule of thumb for recharge times based on DOD and battery capacity?
I have looked in Trojans website and done various searches but found nothing.
A lot depends on how you charge the battery. The first step is to ascertain what sort of charging protocols your chargers and controllers are capable of. In the gridpowered world it is common to charge batteries with some constant current stages, and there is unlimited time to charge the battery.
Most RE chargers use the voltage based bulkabsorbfloat protocol. An advantage of that protocol is that multiple chargers and loads can be happening at the same time... each of them sees the same battery voltage and doesn't care how much current is going to the other loads or coming from the other chargers.
With that type of RE protocol, you can choose your absorb voltage and the amount of time in absorb. That's really all you can do (assuming you have adequate current available). The higher the voltage, the faster the recharge time. But higher voltages promote positive grid corrosion and make more heat in the battery. Many folks raise their absorb voltage in the winter to speed up the charging process... shorter hours of sun to work with.
vtMaps4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i 
Re: Recharge time's for Trojan L16REB deep cell batteries.
The Maximum continuous rate of charge for the Xantrex 4024 is 150a.
I'm a detail person and there must be a rule of thumb based on the battery rating, battery type, the DOD and the charger capabilities.
Another reason I ask is because I purchased a New 28v 450a military surplus alternator as a more efficient way to recharge the batteries if needed because the speed is not critical as it is in an AC generator. So it can run much slower and more fuel efficient.
It will be powered by a 10hp Yanmar diesel..
90cummins 
Re: Recharge time's for Trojan L16REB deep cell batteries.The Maximum continuous rate of charge for the Xantrex 4024 is 150a.
I'm a detail person and there must be a rule of thumb based on the battery rating, battery type, the DOD and the charger capabilities.
Another reason I ask is because I purchased a New 28v 450a military surplus alternator as a more efficient way to recharge the batteries if needed because the speed is not critical as it is in an AC generator. So it can run much slower and more fuel efficient.
It will be powered by a 10hp Yanmar diesel..
90cummins
For an AGM battery, a rate of C/4 is conservative and higher rates (up to C) may be possible with temperature and voltage monitoring. Check the particular battery specs to be sure.
For a GEL battery, anything higher than C/20 could cause permanent damage (loss of capacity). There is at least one brand of GEL that claims their special construction allows higher charging rates, but that lies outside the rule of thumb.
Running a diesel for long periods at less than 50% of full power can cause a damaging condition called wet stacking. I am not sure whether running the engine at reduced speed but near full mechanical output for that speed would be OK or not. Less than 50% power at full speed will be a problem.SMA SB 3000, old BP panels. 
Re: Recharge time's for Trojan L16REB deep cell batteries.
I'm new to the battery backup scene, could you expand on the terminology C20, C/8.
My new batteries are flooded and rated at 370amp @ the 20hr rate.
Thanks
90cummins 
Re: Recharge time's for Trojan L16REB deep cell batteries.I'm new to the battery backup scene, could you expand on the terminology C20, C/8.
My new batteries are flooded and rated at 370amp @ the 20hr rate.
Thanks
90cummins
Sure.
A battery which is rated at 370 amphours at the 20 hour rate is said to have a C (or more specifically C_{20}) value of 370.
If you discharge it quicker you will get less total amp hours. If you discharge it slower than that you will get more amp hours (Look up Peukert's law as applied to lead acid batteries.)
For an ideal battery, which does not exist, you could draw 370A for one hour or one amp for 370 hours and drain the battery by the same amount, 370 amphours.
When you want to specify a charging rate using a number which will not differ depending on battery size, you use the relative rate form, such as C/20 or C/8.
For your battery the C/20 rate is 370 amphours/20 hours = 18.5 Amps. For a battery half that size, C/20 would be 9.25A.
For your battery the C/8 rate would be 370/8 = 46.25A.
People who are not able to use subscript notation (hint: Go to Advanced when posting) will just write C20. Never confuse that with 20C which will be twenty times the C_{20} capacity.
If the hour value for the rate is not specified, assume that the 20 hour rate is being used.SMA SB 3000, old BP panels. 
Re: Recharge time's for Trojan L16REB deep cell batteries.
One thing caught my attention    a 4000 watt inverter powered by a 24 volt, 370 amp battery bank. At a full 4000 watt load, and without any surge above 4000 watts, the inverter will be sucking roughly 170 amps from your battery bank (depending on battery voltage at any instant), and that's roughly C2, a VERY high rate of discharge that will very quickly lead to battery voltage sag and the inverter shutting down on low battery voltage. Just something to be aware of.
What loads do you have planned for this system? 
Re: Recharge time's for Trojan L16REB deep cell batteries.For your battery the C/20 rate is 370 amphours/20 hours = 18.5 Amps. For a battery half that size, C/20 would be 9.25A.
For your battery the C/8 rate would be 370/8 = 46.25A.
Note that the units of the denominator in "C/20" is "20 hours", but in "C/8" the denominator is "8", NOT "8 hours". The only time the units for these equations make sense is when the denominator is the same as the number of hours that C is based on.
Example: the C_{20} capacity of a battery is 370 ah. If you discharge it at 46.25 amps (C_{20}/8 ), you are NOT discharging it at an 8 hour rate (C_{8}). The 8 hour discharge rate is less than 46.25 amps because the C_{8} capacity of the battery is less than 370 ah.
The equations can be "repaired" with the addition of a Peukert factor to compensate for the Capacity (C) being based on a different discharge rate than the denominator.
vtMaps4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i 
Re: Recharge time's for Trojan L16REB deep cell batteries.Note that the units of the denominator in "C/20" is "20 hours", but in "C/8" the denominator is "8", NOT "8 hours". The only time the units for these equations make sense is when the denominator is the same as the number of hours that C is based on.
Example: the C_{20} capacity of a battery is 370 ah. If you discharge it at 46.25 amps (C_{20}/8 ), you are NOT discharging it at an 8 hour rate (C_{8}). The 8 hour discharge rate is less than 46.25 amps because the C_{8} capacity of the battery is less than 370 ah.
The equations can be "repaired" with the addition of a Peukert factor to compensate for the Capacity (C) being based on a different discharge rate than the denominator.
vtMaps
And the mixing of the 20 hour rate and an 8 hour "time factor" is perfectly appropriate when calculating the maximum or minimum recommended charging rate.
The rule of thumb C/12, C/10 and C/8 numbers are all based on C being in fact the C_{20} capacity of the battery.
It is not based on expecting the battery to be fully recharged in 12, 10 or 8 hours.
So no Peukert factor correction belongs in the recommended amp calculation.SMA SB 3000, old BP panels. 
Re: Recharge time's for Trojan L16REB deep cell batteries.
4kW on 24v is around 0.4 C. Which, is high for FLA. OK for AGM & lithium.
Of course on 48V 400Ah would be 0.2 C, and thus the rule "100Ah per kW" really means "4800Wh per kW" of inverter. But that doesnt roll off the tongue quite the same.waynefromnscanada wrote: »One thing caught my attention    a 4000 watt inverter powered by a 24 volt, 370 amp battery bank. At a full 4000 watt load, and without any surge above 4000 watts, the inverter will be sucking roughly 170 amps from your battery bank (depending on battery voltage at any instant), and that's roughly C2, a VERY high rate of discharge that will very quickly lead to battery voltage sag and the inverter shutting down on low battery voltage. Just something to be aware of.
What loads do you have planned for this system?1.8kWp CSUN, 10kWh AGM, Midnite Classic 150, Outback VFX3024E,
http://zoneblue.org/cms/page.php?view=offgridsolar 
Re: Recharge time's for Trojan L16REB deep cell batteries.Actually, I left both the Amphours units in the numerator and the hours units in the denominator out of the second calculation to save time and space. The units are exactly the same as in the first calculation.
And the mixing of the 20 hour rate and an 8 hour "time factor" is perfectly appropriate when calculating the maximum or minimum recommended charging rate.
The rule of thumb C/12, C/10 and C/8 numbers are all based on C being in fact the C_{20} capacity of the battery.
It is not based on expecting the battery to be fully recharged in 12, 10 or 8 hours.
So no Peukert factor correction belongs in the recommended amp calculation.
So you are saying that the units of the denominator are 'hours'.
Therefore, when someone asks "how do I calculate a 10% charge rate?", will you answer "Multiply the AH capacity of the battery by 0.1 hours^{1}" or will you answer "Divide the AH capacity of the battery by 10 hours"?
When someone asks "how do I calculate a 2C_{20} charge rate?", will you answer "Multiply C_{20} by 2 hours^{1}" or will you answer "Divide C_{20} by a half hour"?
vtMaps4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i 
Re: Recharge time's for Trojan L16REB deep cell batteries.So you are saying that the units of the denominator are 'hours'.
Therefore, when someone asks "how do I calculate a 10% charge rate?", will you answer "Multiply the AH capacity of the battery by 0.1 hours^{1}" or will you answer "Divide the AH capacity of the battery by 10 hours"?
When someone asks "how do I calculate a 2C_{20} charge rate?", will you answer "Multiply C_{20} by 2 hours^{1}" or will you answer "Divide C_{20} by a half hour"?
vtMaps
I suppose I could just say to drop the "hours" units off the C value and then either multiply or divide by a dimensionless number.
But then somebody would probably start listing battery capacity in ampdays or ampminutes and confuse the whole issue again.
Keeping track of units can either be incredibly tedious for not much return or can both serve as a reality check on formulas and give deep insight into what the formula itself is trying to tell you.
I tend toward the latter view except when I am in a hurry.SMA SB 3000, old BP panels. 
Re: Recharge time's for Trojan L16REB deep cell batteries.Oh, you are being clever today!
Cariboocoot likes to call it pedantic. vtMaps4 X 235watt Samsung, Midnite ePanel, Outback VFX3524 FM60 & mate, 4 Interstate L16, trimetric, Honda eu2000i 
Re: Recharge time's for Trojan L16REB deep cell batteries.waynefromnscanada wrote: »One thing caught my attention    a 4000 watt inverter powered by a 24 volt, 370 amp battery bank. At a full 4000 watt load, and without any surge above 4000 watts, the inverter will be sucking roughly 170 amps from your battery bank (depending on battery voltage at any instant), and that's roughly C2, a VERY high rate of discharge that will very quickly lead to battery voltage sag and the inverter shutting down on low battery voltage. Just something to be aware of.
What loads do you have planned for this system?
My selection of a 4kw inverter is based on past experience using my Generac xl4000, it has easily supplied my needs.
Recent fuel consumption and load testing I performed this summer on my 2 Generac XL4000’s showed that voltage dropped off beyond 3500 watts, knowing this it’s apparent I can survive on 3500 watts or less.
I’ve used a Killawatt meter and clampon amp meter to monitor & record all household appliances, lights and entertainment devices including all induction loads. I also use the Killawatt meter to monitor Voltage & Hz while on Gen power.
I have calculated that 3kw (intermittent) is all I need with a base load of 1~1.5kw and 600 to 700 watts at night.
I also used Trojans load calculator to determine how much battery power I need.
I input several scenario’s into Trojans load calculator to get minimum and maximum run times at various loads using the L16REB’s.
My primary concerns are heat in the winter in addition to water, fridge, freezer and lights. I have a wood furnace with a squirrel cage fan motor that draws 465 watts 24/7 and I’m currently looking at a capacitor start/capacitor run motor to reduce that load.
I chose a Xantrex 4024 4kw inverter being realistic; it also has an 8kw surge capacity and can be stacked if needed.
My wife & I are just shy of 60 and our electrical needs have peaked and we are working on reducing them.
I’m fully aware that when the power is out it is about conserving and minimizing consumption.
Thanks for you input.
90cummins 
Re: Recharge time's for Trojan L16REB deep cell batteries.
I received my 4 new Trojan L16REB batteries.
A soon as I got them home I set them up in (2) 12v groups so I could get a charger on them.
The pamphlet I received said that 13.2v is the float charge. After being on the charger all night the voltage was 13.4~13.5, what is the acceptable range?
I'm new to this and don't want to damage $1300 worth of batteries.
Thanks 90cummins 
Re: Recharge time's for Trojan L16REB deep cell batteries.I received my 4 new Trojan L16REB batteries.
A soon as I got them home I set them up in (2) 12v groups so I could get a charger on them.
The pamphlet I received said that 13.2v is the float charge. After being on the charger all night the voltage was 13.4~13.5, what is the acceptable range?
I'm new to this and don't want to damage $1300 worth of batteries.
Thanks 90cummins
Do not judge by Voltage. Float charge is not resting Voltage so it is quite useless as a SOC indicator. Get a hydrometer and measure the Specific Gravity. Trojan will have specs for the SG and probably an Absorb Voltage of 14.8 listed. 
Re: Recharge time's for Trojan L16REB deep cell batteries.I received my 4 new Trojan L16REB batteries.
A soon as I got them home I set them up in (2) 12v groups so I could get a charger on them.
The pamphlet I received said that 13.2v is the float charge. After being on the charger all night the voltage was 13.4~13.5, what is the acceptable range?
I'm new to this and don't want to damage $1300 worth of batteries.
Thanks 90cummins
I just ordered 16 of those. Should be here in a week. We'll see how they all work out for us both!
PS  You said "I have a wood furnace with a squirrel cage fan motor that draws 465 watts 24/7 and I’m currently looking at a capacitor start/capacitor run motor to reduce that load."  Dang that is a big load. I would think there is a more energy efficient fan you could get to replace that?? Or perhaps a combination of a newer fan and a thermostat timer, etc.OffGrid in Central Florida since 2005, FullTime since June 2014  12 X Sovello 205w panels, 9 X ToPoint 220w panels, 36x ToPoint 225w panels (12,525 watts total)  Custom built singleaxis ground mounts  Complete FP2 Outback System: 3 x FM80, 2 x VFX3648, X240 Transformer, FLEXnetDC, Mate3, Hub10, FW500 AC/DC  24 x Trojan L16REB Batteries 1110ah @ 48v  Honda EU7000is Generator and a pile of "other" Generators  HomeMade PVC solar hot water collector  Custom data logging software http://www.somewhatcrookedcamp.com/monitormate.html 
Re: Recharge time's for Trojan L16REB deep cell batteries.I just ordered 16 of those. Should be here in a week. We'll see how they all work out for us both!
PS  You said "I have a wood furnace with a squirrel cage fan motor that draws 465 watts 24/7 and I’m currently looking at a capacitor start/capacitor run motor to reduce that load."  Dang that is a big load. I would think there is a more energy efficient fan you could get to replace that?? Or perhaps a combination of a newer fan and a thermostat timer, etc.
Or leave the fan off.
I removed the one from my wood stove because it made more noise than anything else and didn't really improve heat circulation.
The Ecofan, in this location, does work. It does not work at the cabin because the stove location isn't right for it and there are too many drafts.
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