Generator Battery Tender

MangasMangas Solar Expert Posts: 547 ✭✭✭✭
My old battery tender mounted inside my generator housing bit the dust. It lasted over 8 years plugged in 24/7. Not sure what it was rated at.

I have another waterproof one that trickle charges at about 1 amp which I installed yesterday. Do you guys think it's stout enough to maintain a group 24 marine 12 battery? I have on order a 5 amp waterproof trickle charger too which might be better.

Wonder how much the inverters are drawing from the hard wired generator. Small amount but enough to flatten the battery over time.
Ranch Off Grid System & Custom Home: 2 x pair stacked Schneider XW 5548+ Plus inverters (4), 2 x Schneider MPPT 80-600 Charge Controllers, 2 Xanbus AGS Generator Start and Air Extraction System Controllers, 64 Trojan L16 REB 6v 375 AH Flooded Cel Batteries w/Water Miser Caps, 44 x 185 Sharp Solar Panels, Cummins Onan RS20 KW Propane Water Cooled Genset, ICF Custom House Construction, all appliances, Central A/C, 2 x High Efficiency Variable Speed three ton Central A/C 220v compressors, 2 x Propane furnaces, 2 x Variable Speed Air Handlers, 2 x HD WiFi HVAC Zoned System Controllers

Comments

  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: Generator Battery Tender

    Mangas, what size is the battery? What do you think the daily charge loss is?

    BB likes to use a timer with a 'tender' that turns on once a day.

    hth
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
  • VicVic Solar Expert Posts: 3,145 ✭✭✭✭
    Re: Generator Battery Tender

    Personally, would not use a Trickle Charger, even a one amp one on that battery, which could/should be about 75-ish Ah.
    Keep a close eye on it, as, in time it could boil that battery dry.

    However, do not understand your reference to Inverters, and hard-wired generator. Was the battery being tended running some small inverter ... had guessed that this was the starting battery, that might also have run the Generator Controller (???)?.

    Guessing done for now. Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • MangasMangas Solar Expert Posts: 547 ✭✭✭✭
    Re: Generator Battery Tender

    Vic, the replaced battery tender is automatic and turns itself off when it senses 100% genset battery charge. I had good luck with the old one. It never ran the genset's (1800 rpm propane 20 kw unit) starting battery dry.

    The one I ordered is up to 5 amps and is also an automatic one. If the 1 amp battery tender keeps the genset's battery mostly charged, I'll call it good to go.

    The genset is hard wired to the inverters which are set to run monthly tests or give the batteries an extra infrequent lift. I believe the inverters draw a little power from the genset's battery over time. Since it runs so infrequently, without the automatic battery tender the genset's battery (group 24 deep cycle marine) goes flat.
    Ranch Off Grid System & Custom Home: 2 x pair stacked Schneider XW 5548+ Plus inverters (4), 2 x Schneider MPPT 80-600 Charge Controllers, 2 Xanbus AGS Generator Start and Air Extraction System Controllers, 64 Trojan L16 REB 6v 375 AH Flooded Cel Batteries w/Water Miser Caps, 44 x 185 Sharp Solar Panels, Cummins Onan RS20 KW Propane Water Cooled Genset, ICF Custom House Construction, all appliances, Central A/C, 2 x High Efficiency Variable Speed three ton Central A/C 220v compressors, 2 x Propane furnaces, 2 x Variable Speed Air Handlers, 2 x HD WiFi HVAC Zoned System Controllers
  • VicVic Solar Expert Posts: 3,145 ✭✭✭✭
    Re: Generator Battery Tender

    Hi Mangas,

    OK, sorry I read that these candidates were Trickle chargers, not tenders or Automatic. My mistake.

    Well, some gensets have a controller that uses a bit of the starting battery's power to run it, and therefore means that the starting battery needs more tending than from only silf-discharge of the battery ... Am uncertain of the case with your exact genset.

    The starting battery on the Kubota genset here supplies no loads in the genset, and needs tending every few months, just for good measure.

    Normally, the main inverters, like the SW pluses, would only have the AC leads and the start contacts wired into them, but any genset controller might be drawing a bit of 12 V power continuously, perhaps keeping track of exercise interval, duration, etc ... dunno. Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH [email protected], 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
  • MangasMangas Solar Expert Posts: 547 ✭✭✭✭
    Re: Generator Battery Tender

    Thanks Vic. That's what I think may be going on.

    The inverter controllers and genset relay may be continuously drawing some 12v off the battery or, as you say the genset's internal controller may be a draw too.

    The genset's digital control panel only displays when the genset is running.

    All I can figure is in the past with the tender plugged in the battery stays charged but when the tender is unplugged it goes flat. There is a 110 AC outlet mounted inside the genset cover to receive the battery tender.

    Our genset only runs 60 hours a year, 15 minute bi-monthly tests during the summer and the majority of hours during the winter during inclement weather. Run times are 2 hours when it does. I put a new Exide AGM battery in the genset two months ago (without the tender plugged in) and it's flat.

    Tomorrow, I'll load test the new AGM starting battery to see if it's defective.

    Never had much luck with starting batteries and trailer plugs. . .
    Ranch Off Grid System & Custom Home: 2 x pair stacked Schneider XW 5548+ Plus inverters (4), 2 x Schneider MPPT 80-600 Charge Controllers, 2 Xanbus AGS Generator Start and Air Extraction System Controllers, 64 Trojan L16 REB 6v 375 AH Flooded Cel Batteries w/Water Miser Caps, 44 x 185 Sharp Solar Panels, Cummins Onan RS20 KW Propane Water Cooled Genset, ICF Custom House Construction, all appliances, Central A/C, 2 x High Efficiency Variable Speed three ton Central A/C 220v compressors, 2 x Propane furnaces, 2 x Variable Speed Air Handlers, 2 x HD WiFi HVAC Zoned System Controllers
  • solarvicsolarvic Solar Expert Posts: 1,071 ✭✭✭✭
    Re: Generator Battery Tender

    Mangus! Care to post what brand the battery tender is and where to buy? I need to buy one also. solarvic
  • MangasMangas Solar Expert Posts: 547 ✭✭✭✭
    Re: Generator Battery Tender

    Hi Solarvic,

    I just installed on the genset a 800mA Deltran Automatic Waterproof Battery Tender. I also ordered a 5 amp 12 v Deltran Automatic Waterproof Battery Tender to replace the 800mA unit. Bought them on Amazon. I have no experience with these tenders but will see if that solves it.

    I suspect the genset's internal controller may be slowly drawing current down over a couple of months running down the battery. Like I posted, the genset never ran long enough during tests to give it enough charge.

    When the old battery tender died on me, I decided not to hook up a new battery tender which may be the reason the battery went dead. We'll see.
    Ranch Off Grid System & Custom Home: 2 x pair stacked Schneider XW 5548+ Plus inverters (4), 2 x Schneider MPPT 80-600 Charge Controllers, 2 Xanbus AGS Generator Start and Air Extraction System Controllers, 64 Trojan L16 REB 6v 375 AH Flooded Cel Batteries w/Water Miser Caps, 44 x 185 Sharp Solar Panels, Cummins Onan RS20 KW Propane Water Cooled Genset, ICF Custom House Construction, all appliances, Central A/C, 2 x High Efficiency Variable Speed three ton Central A/C 220v compressors, 2 x Propane furnaces, 2 x Variable Speed Air Handlers, 2 x HD WiFi HVAC Zoned System Controllers
  • BB.BB. Super Moderators, Administrators Posts: 32,597 admin
    Re: Generator Battery Tender

    Hmm... Thought I already made a reply.

    Anyway, I used the one to two hour per day on a lamp timer when floating batteries with the 1 amp charging cubes--The several I tried would otherwise "boil" a battery down to exposing the plates in 1-2 months otherwise. I adjusted the time based on the amount of load from the car's electrical system (an older Lexus would take about 180 mAmps to run the computers, GPS, old On-Star system, Lojack, etc.).

    I eventually replaced the AC charging cube with this Battery Minder:

    http://www.amazon.com/BatteryMINDer-Battery-Charger-Maintainer-Desulphator/dp/B000JFLSL6

    Not cheap, but has worked for 2-3 year very well... And it manages to take care of the "oops" factors better too (somebody leaves the turn cracked open and discharges the battery--The 1 amp cube+timer could not cope with the changes in loads).

    Don't have to monitor/add water now and the car starts reliably even if it sits for a couple of months at a time (originally, the battery would "go dead" in about 2-4 weeks if not driven weekly).

    If it is disconnected from the Battery, I have to reset the charging parameters (defaults to lower current/GEL settings when the battery is reconnected--Which are OK too).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • MangasMangas Solar Expert Posts: 547 ✭✭✭✭
    Re: Generator Battery Tender

    Hi Bill,

    Your unit is better than the one I ordered. Should have checked in with you first.

    Do you think the little 800mA automatic tender will keep the battery in reasonable shape? I'd rather use the smaller one than the 5 amp version I ordered which uses more juice.
    Ranch Off Grid System & Custom Home: 2 x pair stacked Schneider XW 5548+ Plus inverters (4), 2 x Schneider MPPT 80-600 Charge Controllers, 2 Xanbus AGS Generator Start and Air Extraction System Controllers, 64 Trojan L16 REB 6v 375 AH Flooded Cel Batteries w/Water Miser Caps, 44 x 185 Sharp Solar Panels, Cummins Onan RS20 KW Propane Water Cooled Genset, ICF Custom House Construction, all appliances, Central A/C, 2 x High Efficiency Variable Speed three ton Central A/C 220v compressors, 2 x Propane furnaces, 2 x Variable Speed Air Handlers, 2 x HD WiFi HVAC Zoned System Controllers
  • BB.BB. Super Moderators, Administrators Posts: 32,597 admin
    Re: Generator Battery Tender

    More or less--A lead acid battery on "float" should run less than 1% rate of charge when it is in good shape (a good AGM is probably in the 0.1% float current).

    And, if it is >2% rate of charge, it is probably time to change the battery out (will be failing sooner than later).

    So, your 800 mAmp charger should be fine for an ~80 AH group 24 battery. The unknown is the amount of current drawn by the ancillary electronics.

    You can monitor the battery voltage and if it is in the ~13.4 to 13.8 volt range--Probably all is OK. If your battery floats below 13.4 volts--You probably need a larger charger for the application (if you don't have a DC Current Clamp meter handy).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • MangasMangas Solar Expert Posts: 547 ✭✭✭✭
    Re: Generator Battery Tender

    Checked it and I think the voltage is about 13.5-6. The draw must be small but 24/7.

    Always can count on you Bill. Will monitor and report back.

    Thanks!
    Ranch Off Grid System & Custom Home: 2 x pair stacked Schneider XW 5548+ Plus inverters (4), 2 x Schneider MPPT 80-600 Charge Controllers, 2 Xanbus AGS Generator Start and Air Extraction System Controllers, 64 Trojan L16 REB 6v 375 AH Flooded Cel Batteries w/Water Miser Caps, 44 x 185 Sharp Solar Panels, Cummins Onan RS20 KW Propane Water Cooled Genset, ICF Custom House Construction, all appliances, Central A/C, 2 x High Efficiency Variable Speed three ton Central A/C 220v compressors, 2 x Propane furnaces, 2 x Variable Speed Air Handlers, 2 x HD WiFi HVAC Zoned System Controllers
  • RCinFLARCinFLA Solar Expert Posts: 1,452 ✭✭✭✭
    Re: Generator Battery Tender

    I have used battery tender for my 15kw gen and lawn tracker. They float the battery at about 13.5 vdc which should be okay. The problem comes from the quality of the battery. Lead Calcium based plate alloy battery have a low self discharge so a 1 amp capable tender should be very sufficient for a 75 AH class 24 marine battery.

    Long period floats cause some oxidation of positive plates and can weaken (via corrosion) the inter-cell connector straps. Again the quality of battery matters. I have had small lawn tractor batteries that last over 5 years on tender float and other cheap one that only last two years. The cheaper battery would probably have failed anyway with a periodic top of charge.

    Failure mode is high series resistance. They reach 14.5 v quickly when connected to a charger and collapse under load.

    Throwing a load on the battery at least every two to four months seems to help. It burns off some of the lead oxide build up.
  • MangasMangas Solar Expert Posts: 547 ✭✭✭✭
    Re: Generator Battery Tender

    RC,

    You're right.

    I load tested the battery today and a cell was bad to boot. Installed a new battery managed with the automatic 800mA battery tender which should be up to the task. Plan to keep the 5 amp version in reserve. The old one never missed a beat after all those years.

    I didn't realize the genset drew a little 12v from the battery while it sat. After a couple months must add up without a tender helping out. I probably mismanaged it all.
    Ranch Off Grid System & Custom Home: 2 x pair stacked Schneider XW 5548+ Plus inverters (4), 2 x Schneider MPPT 80-600 Charge Controllers, 2 Xanbus AGS Generator Start and Air Extraction System Controllers, 64 Trojan L16 REB 6v 375 AH Flooded Cel Batteries w/Water Miser Caps, 44 x 185 Sharp Solar Panels, Cummins Onan RS20 KW Propane Water Cooled Genset, ICF Custom House Construction, all appliances, Central A/C, 2 x High Efficiency Variable Speed three ton Central A/C 220v compressors, 2 x Propane furnaces, 2 x Variable Speed Air Handlers, 2 x HD WiFi HVAC Zoned System Controllers
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: Generator Battery Tender

    Parasitic draws upon the battery can add up fast. Lets say you have only 100 milliamp parasitic draw. Over the course of a typical month, that's about 72ah down the tubes. So find and fix those parasitics. The tenders / minders can help, but this is a band-aid approach.

    One big problem of using too small a tender on a large battery that is not charged to 100% SOC beforehand, is that the quality tenders have a timeout, and will drop to float after a number of hours in absorb. This timeout can occur way too early for a large battery bank, and in some cases, the minimal current is too inefficient to even charge.

    Unless you are dealing with a motorcycle or other small sized battery, the tender / minder to use would be in at least the 5A range or more.

    Note that the actual battery-tender brand typically uses about 13.2 to 13.4v for float, and in some cases, this can void the warantee from a manufacturer that insists on a minimal 13.5 or higher voltage for float. Choose your tender / minder carefully.
Sign In or Register to comment.