Author Topic: Field Experience With AGM Batteries In MNBE-D3R Cabinet  (Read 3001 times)

icarus

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Field Experience With AGM Batteries In MNBE-D3R Cabinet
« on: July 16, 2012, 02:05:07 PM »
Troubleshooting a failure in an off-grid hybrid Solar / Generator / Battery power system with the inverter, auto generator start, battery monitor kit, and batteries all installed in a MNBE-D3R cabinet.

Design was limited to ( 1 ) MNBE-D3R cabinet based on size constraints. MNBE-D3R cabinet located outside structure and has direct sun exposure in early morning and after ~3 pm.

Loads require ~690 Ah / day. Structure occupied 7x24x365.

Solar array three (3) 240W modules into a MorningStar TriStar-MPPT-45 charge controller. IMP ~ 8A DC. PV Watts average PSH per day, ~5, resulting in ~3 kWh (or 62 AH) per day into the battery bank. PV array size was limited by the size of the structure on which they were mounted. PV provides ~10% of power required on a daily basis.

Inverter/charger is a Magnum MS4448PAE. Generator is a 6kW LP, delivering up to 25A @ 240VAC to the Magnum charger.

Generator start & stop is based on battery bank SOC (state of charge):  GEN ON @ 70% SOC; GEN OFF @ 90% SOC. Generator provides ~90% of power required on a daily basis.

Separate battery temperature sensors for TriStar CC and Magnum charger.

System has been in service ~3 months in a south Texas location. Battery bank failed when two (2) of the eight 6-volt 200AH AGM batteries had melted ( + ) terminals.

Initial thoughts are:  1) two faulty batteries from factory?  2) after initial charge to 100%, batteries may not have reached 100% as frequently as required?  3) GEN ON/OFF SOC percentages need to be changed?  4) Batteries getting too hot in outdoor environment?  5) Battery bank undersized?

Any other suggestions on what caused the battery failures, and possible solution(s)?

Vic

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Re: Field Experience With AGM Batteries In MNBE-D3R Cabinet
« Reply #1 on: July 16, 2012, 03:30:00 PM »
icarus,

Well,  my first thoughts revolve around poor connections on the batteries with the melted terminals.  Possibly poor crimps or battery terminals not clean at time of installation etc.

It is also important to retorque all high current connections once after about 24 hours,  and then periodically re-checked.  Poor connections heat,  and over time,  can become looser and looser as they are temp cycled,  often causing more heat and progressive looseness.

Just my first opinion.  As you know,  no battery likes HEAT,  it is often death for them,  but that is a different topic.  Good Luck,   Vic
Off Grid - Two systems -- 4 SW+ 5548s, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 3X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  Thanks MN for Great Products/Service/Support!

nigel

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Re: Field Experience With AGM Batteries In MNBE-D3R Cabinet
« Reply #2 on: July 17, 2012, 11:53:08 AM »
My intial thoughts are a 200ah battery bank with a 4kw Inverter is a serious  bad match even at 48v. Starting the generator only on state of charge criteria  also means that hi loads can be drawn for a period of time before the genny kicks in. If the battery voltage is low this also increases the amps flow. large current flows generate heat, cycling of hot and cold could have caused loose connections as vic said.

Should have set gen start most importantly  for load start and also voltage start.

My OB and Rolls battery  distributor is a stickler on these mismatches of large Inverters with small battery banks. It is often a cause of early
battery failure.

IMHO Nigel
« Last Edit: July 17, 2012, 11:59:54 AM by nigel »

icarus

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Re: Field Experience With AGM Batteries In MNBE-D3R Cabinet
« Reply #3 on: July 18, 2012, 10:32:59 AM »
MNBE-D3R USERS:
How well do 200AH AGM batteries tolerate heat inside a MNBE-D3R cabinet located outdoors?

VIC:
Thanks for the re-torquing suggesting after 1st 24 hours. I'll make sure that's added to the commissioning procedure.

NIGEL:
Thanks for your response. Loads in this application are about 50% lighting (night-time) and a small A/C unit (draws ~7A AC when compressor runs). Unfortunately the battery bank size was determined based on the space available in the MNBE-D3R cabinet.

This application is set-up as "solar assist" since PV delivers ~10% of power consumed. Your suggestion to change the charging regime from SOC-based to a load and/or voltage start regime is a good one.

icarus

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Re: Field Experience With AGM Batteries In MNBE-D3R Cabinet
« Reply #4 on: July 18, 2012, 11:25:37 AM »
Attached is a photo showing the internal components of the MNBE-D3R cabinet.

SolarMusher

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Re: Field Experience With AGM Batteries In MNBE-D3R Cabinet
« Reply #5 on: July 20, 2012, 10:55:27 AM »
Hi Icarius,
Another suggestion would to check the setting of the Magnum charger to adjust it to the battery capacity, 60ADC (100%) is too strong for this small 200Ah battery bank and as Vic said could cause losse connections.
A+
Erik
Off Grid with 3.2kw PV | Classic 200/WBjr + Classic lite 200 | 2x Outback VFX3648 Epanel | 4x SPD300 | Hub + Mate + PSX-240 | 750Ah Rolls S-480 battery bank + Trimetric | 1200 watts DC water heater | 8000 Generac and 7200 watts Champion gas generators

icarus

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Re: Field Experience With AGM Batteries In MNBE-D3R Cabinet
« Reply #6 on: July 20, 2012, 11:36:42 AM »
Thanks Eric. Per the battery manufacturer, maximum bulk charging current is 30% of the C/20 rate, or 190 x 0.3 = 57A. When the generator is bulk charging, ~55A is delivered to the batteries.

SolarMusher

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Re: Field Experience With AGM Batteries In MNBE-D3R Cabinet
« Reply #7 on: July 20, 2012, 12:06:49 PM »
Not sure that an enclosed inverter like this one would be a good idea. With the 60A Magnum charger running frequently, it can overheat within this small enclosure. What are the inverter wire length and size? The first time I wired a 4448 with 2/0, it was heating too much for me when charging. Now, I always use 4/0 for Magnum 4448 or 4024 and the inverters run and charge cooler which is far better.
Everything here to get trouble with batteries...
A+,
Erik
Off Grid with 3.2kw PV | Classic 200/WBjr + Classic lite 200 | 2x Outback VFX3648 Epanel | 4x SPD300 | Hub + Mate + PSX-240 | 750Ah Rolls S-480 battery bank + Trimetric | 1200 watts DC water heater | 8000 Generac and 7200 watts Champion gas generators

SolarMusher

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Re: Field Experience With AGM Batteries In MNBE-D3R Cabinet
« Reply #8 on: July 20, 2012, 12:18:06 PM »
Hi Icarus,
When I set a S-460 FLA battery bank 350Ah@48VDC/20hr, i adjust this charger to 65%, and when I set a S-600 FLA 450Ah@48VDC/20hr, i adjust this charger to 85% according Rolls specifications...
You'd better charge these batteries at lower rate.
Just what I think.
A+
Erik
Off Grid with 3.2kw PV | Classic 200/WBjr + Classic lite 200 | 2x Outback VFX3648 Epanel | 4x SPD300 | Hub + Mate + PSX-240 | 750Ah Rolls S-480 battery bank + Trimetric | 1200 watts DC water heater | 8000 Generac and 7200 watts Champion gas generators