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sjturbo's avatar
sjturbo
Explorer
Sep 06, 2014

More battery/converter/inverter questions

As many of you know I have been asking many questions and greatly appreciate all of your inputs. It seems the more I read the more questions I have. I have ordered a Mega Watt PS to Top Charge and EQ my batteries based on much feedback. I will likely be getting a PD9260 to replace my WFCO which has given up the ghost. And I will be installing four 6V GC batteries. Now for questions.
1. Should I set up two 6V series banks or one series/parallel bank?
2. I would like to put the new converter close to the batteries. Will I need to run connections back to the DC distribution panel or can I use the wires already there from the WFCO panel to the batteries?
I would like to hook up an inverter to run TV/sat.. Are there any online diagrams that I could study?

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  • BFL13's avatar
    BFL13
    Explorer II
    Sep 07, 2014
    mena661 wrote:
    BFL13 wrote:

    How many amps will four batts accept at 15+ volts at over 90% SOC? Be more than 5a each at 90% at 14.5v. No idea. It will taper from 90-99% SOC whatever it starts at. Say it is 8a per batt for this math exercise--might be more than 8 really--so now you can do 4 x 8 =32a on four at 90%. If you try 40a and they will only take 32, then 32 is what you will see going in even if you try to shove in 40 :)
    If I set the MW to 15.45V (mine maxes out there) and the batt voltage gets to 15.45V, my batts are taking 8 amps.


    Please clarify. What SOC would the batts be when they reach 15.45, and is that 8a per batt or 8a for the bank of 740AH

    My "5a per batt" is really 5a per 110AH of bank to be more exact.

    ISTR Mex says to equalize at 15.5 with 5 amps per 100AH? But that would be on a "full" (97% + ) batt

    I was looking for the acceptance rate per 110AH of bank at 90% SOC for what the bank would take after getting to 90% on the "regular charger" at 14.6ish and then you jumped the voltage to 15.5. That would tell you what amps size of a MW would be good. (where there is no sense getting one that can do more amps than the batts can accept then--unless you would use the MW as the "regular charger" too, not just as a finishing charger.
  • pianotuna's avatar
    pianotuna
    Nomad III
    Sep 07, 2014
    Hi mena,

    Given that your bank is L-16 and a wonderful number of amp-hours, if those numbers are scaled back to four golf cart, I'd expect only about 5 amps instead of the 8 amps you are getting.

    This is where solar can *really* shine.
  • mena661's avatar
    mena661
    Explorer
    Sep 07, 2014
    BFL13 wrote:

    How many amps will four batts accept at 15+ volts at over 90% SOC? Be more than 5a each at 90% at 14.5v. No idea. It will taper from 90-99% SOC whatever it starts at. Say it is 8a per batt for this math exercise--might be more than 8 really--so now you can do 4 x 8 =32a on four at 90%. If you try 40a and they will only take 32, then 32 is what you will see going in even if you try to shove in 40 :)
    If I set the MW to 15.45V (mine maxes out there) and the batt voltage gets to 15.45V, my batts are taking 8 amps.
  • BFL13's avatar
    BFL13
    Explorer II
    Sep 07, 2014
    Say you know your daily AH usage is about 70AH and you want a fast recharge off generator. So you want to operate in the 50-80% SOC zone where the batts can accept full amps.

    To recharge every day, that means 50-80=30% is 70AH so 100% is 233AH
    Great. Grab a pair of Interstate 6s (232AH) Now say you only want to do your recharge every second day. So you will run 140AH in two days but still want that to be a 50-80. So grab a second pair of 6s and now your bank is 464AH.

    Now how long do you want that 50-80 recharge to take? My ugly graph posted here and there shows doing a 50-80 on 220AH with smart chargers will take 60min with a 70a charger, 79 min with a 55a, and 117 min with a 35 amper.

    Double those times for the same amps on four batts for the 50-80. Or you can double the amps on the four that you used on the pair and get the same times as with two batts. Ie to do a 50-80 on four in an hour you need a 140a charger

    Now you need enough generator to run that many amps that you need for the time you want the 50-80 to take. Here is where you have a fixed limit and may already have that generator, so you might have to work back from that to see what you can do.

    Say you have a Honda 2000 and it will run a 70a charger but no more. So you can see that if you want to do your 50-80 in an hour you must recharge every day and only have the two 6s. If you choose to recharge every second day with the 70amper on four batts it will now take you two hours.

    So you have to juggle battery bank size, generator size, charger size, and fit that all within your generator running time, which may not be up to you. EG here the provincial parks allow two hours of gen time 9-11am and 6-8pm.

    If you want to do your 50-80 in the morning (it is dark out 6-8pm in the "winter" here, so who wants to go out there in the dark and maybe rain to play with chargers and generators?) then you are working with a two hour limit.

    So going back to your choices, you can see that to get your 50-80 done in two hours you have to have that 70 amper and the 2000 gen. BUT--bad news! In winter your 70AH a day just went to 140AH day now that you need 70AH for the furnace and keep doing everything else the same as in summer. Drat! Now you need 140a charger, four batts, and a gen that can run 140a recharging.

    Of course you must always have enough of everything so you can at least do one day before recharging so you don't run out of battery at 3am on a winter night.

    EG camping here in February, we use nearly 200AH a day, so on four batts that means a recharge every day, and the Honda 3000 can do 130a.
    I do 50-90s so that adds time (doubles it!) over a 50-80 but gives us another 10% of 460 or 46AH to be part of that 200AH we used. 40% of 460 is 184AH so close enough to our daily usage.

    With 140a it will take about 130minutes to do that 50-90 so we have to cheat and run over the time by 10 minutes. Except we only have 130a so we need to cheat for longer. (No sweat--at that time of year we would usually be the only ones camping in the whole park and nobody cares about the two-hour generator times. :)
  • MEXICOWANDERER's avatar
    MEXICOWANDERER
    Explorer
    Sep 07, 2014
    • A camper sizes a battery so as to discharge 50% between generator charges
    • But with a generator and 60 ampere charger when the battery fills and reaches the point where 15-20 amps charge rate prevails, running the generator is a waste of time and resources
    • But if the camper must have that capacity - needs a full battery then without question he battery capacity is critically too small
    • Imagine thee batteries at the same point where they consume 20 amps each. Well guess what, the generator and charger is not goofing off
    • Sixty amps is sixty amps in anyone's book
    • Sizing a battery cank -intelligently- is NOT repeat NOT just a matter of having enough power to last between recharges when recharging with a generator
    • It is a matter of keeping the generator and charger busy and not allowing them to goof off
    • YES, YES more batteries means more kWh to charge to 100% state of charge
    • But read this carefully, when a camper goes off on a week long boondocking trip, charges his batteries to say 80% state of charge then has access to a power pedestal WHO THE HELL CARES if it takes the charger 17 hours and twenty seven minutes to fully recharge the battery bank?
    • I would not get carried away with this philosophy to the point where the batteries discharge say 30% in three days time, but a compromise between battery bank size and keeping the generator and charger busy is a real goal to shoot for
    • In my case I do not fully recharge the Rolls 24V bank. I charge until total recharging amperage drops to 80, then the Kubota gets shut down. When public power is restored, the 4024 Trace has all the time in the world to recharge at its piddly 120 amp 28 volt rate.
    sjturbo wrote:
    MEXICOWANDERER wrote:
    60 amp charger potential. When two batteries are charged to the point where they are consuming 18 amps, four batteries will consume 36 amps. Think about it, especially when charging using a generator.

    Thanks for coming to the show MEXICOWANDERER! So help me understand, please. Are you saying that the PD9260, (60A), will supply adequate current, Also if I am using the Mega Watt S-250-12 to Top Charge and it has a 30A continuous rating the four batteries I should be ok since by the time I am ready to Top Charge the current draw should be much less? However maybe not so easy "standard charging" for my Honda eu3000?
  • BFL13's avatar
    BFL13
    Explorer II
    Sep 07, 2014
    sjturbo wrote:
    Thanks Niner! Actually the four Crowns are rated at 470ah. And according to the "Crown battery requirements, The Bible" that you linked me to it indicates a charge factor of 1.07 (107%) to be fully recharged. 470ah/2 = 235ah*107%=251.45ah for a complete recharge. I think I have that correct. It appears that none of the PD9200 converters can supply the 15.3vdc needed to top off the batteries, (more like 14.4 to 14.6vdc? with the pendant). I thought that is why MW suggested the Mega Watt power supply since the voltage can be adjusted to above 15vdc likely 15.5vdc. If I am boondocking and the only ac source I have is the Honda eu3000 I thought the Mega Watt was a logical alternative. I certainly like the solar idea and somewhere down the line I may invest in what you have noted. Until then the eu3000 is my only choice?


    My Honda 3000 can run four Vector chargers at the same time doing a total of 130amps (on four batts) but if I try 135 amps the Honda pops its breaker so 130 is it with the Vectors (I think they have PF about 0.8 from some calculations I did a while back)

    However, using my PF corrected PowerMax 100amper (does 103a) instead in the mix with two Vectors doing a total of 50a I can run 150a of charging with the Honda 3000 and not pop its breaker.

    But I did modify the 100 amper to stay at 14.8v instead of dropping to 13.6 once the batts get to 14.6 so I get a faster charge. The PD80 amper is not PF corrected and needs a 20a circuit so it will use more of the Honda to make the 80a (expect more like 75a in real like with the PD due to a design "issue" they have unless mounted really close to the battery on really fat wires)

    Your four batts could take two 80s worth of amps at 160a but the Honda couldn't run both at PF 0.7 It probably could run two 60s for 120a especially since that would likely be two 55a actual.

    A battery will accept about 5a at 14.5v when it is at 90% SOC. So my rule is to stop the charge at 5 amps per batt when doing a 50-90. On two batts that would be when amps get down to 10 and with four batts, 20a.

    So now you would swap to the MW and jack the voltage up to 15+ for the finish charge (inverter will alarm off at 15 so do it when you don't need the inverter---as noted the Honda 3000 will have lots to spare just running the MW so you can use the gen instead of the inverter anyway at that time)

    Now your only problem is generator time past the time it took to do your 50-90. With 120a going in on four batts the 50-90 might take two hours. So you must keep the gen running long enough after that to do the top charge. I don't know how long that would take--another two hours?

    How many amps will four batts accept at 15+ volts at over 90% SOC? Be more than 5a each at 90% at 14.5v. No idea. It will taper from 90-99% SOC whatever it starts at. Say it is 8a per batt for this math exercise--might be more than 8 really--so now you can do 4 x 8 =32a on four at 90%. If you try 40a and they will only take 32, then 32 is what you will see going in even if you try to shove in 40 :)
  • RJsfishin's avatar
    RJsfishin
    Explorer
    Sep 07, 2014
    Quote:
    I've seen 37 amps, max out of my PD9245
    --------------------------------------------
    At what voltage ? If I remember correctly, that was on 1 skimpy little battery. And was it even discharged ?
    I would think the ratings are for low voltage on a battery discharged to at least 50%
  • sjturbo's avatar
    sjturbo
    Explorer
    Sep 07, 2014
    Thanks Niner! Actually the four Crowns are rated at 470ah. And according to the "Crown battery requirements, The Bible" that you linked me to it indicates a charge factor of 1.07 (107%) to be fully recharged. 470ah/2 = 235ah*107%=251.45ah for a complete recharge. I think I have that correct. It appears that none of the PD9200 converters can supply the 15.3vdc needed to top off the batteries, (more like 14.4 to 14.6vdc? with the pendant). I thought that is why MW suggested the Mega Watt power supply since the voltage can be adjusted to above 15vdc likely 15.5vdc. If I am boondocking and the only ac source I have is the Honda eu3000 I thought the Mega Watt was a logical alternative. I certainly like the solar idea and somewhere down the line I may invest in what you have noted. Until then the eu3000 is my only choice?
  • NinerBikes's avatar
    NinerBikes
    Explorer
    Sep 07, 2014
    sjturbo wrote:
    Welcome NinerBikes! You posted while I was responding to MW. So you indicate an 8amp difference from advertised? Maybe I should go with the 9270 to be safe? Any thoughts on the S-250-12 being adequate for Top Charge?


    4 6V batteries, 420 amp hours total capacity... use 50% of that, and you need to replace 210 amps. Your Honda Eu3000i will handle what ever charge controller you throw at it. I'd go with a PD 9280. Your generator will handle it, no problem. 50 to 90% would be 80% of 210 amps to be replaced... 168 amps. Goal would be to have a charge controller that can do that in around 2 hours run time. PD 9280 sounds about right. Get Fat wire direct from stand alone PD 9280 to the batteries.

    Top charge with the Mega Watt. 15.3 volts. Another option... 360W of 12V solar panel and a Solar 30 PWM charge controller set at 15.0V to do the top charge instead.

    Your Honda Eu3000i will be hugely underutilized running that Mega Watt 35 -12.
  • sjturbo's avatar
    sjturbo
    Explorer
    Sep 07, 2014
    Welcome NinerBikes! You posted while I was responding to MW. So you indicate an 8amp difference from advertised? Maybe I should go with the 9270 to be safe? Any thoughts on the S-250-12 being adequate for Top Charge?

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