Helping a member here with a military solar deployment trailer setup. Battery suggestions?

[Supervstech]

Lead acid is of course what it came with, and would offer the most versatility weather wise. But he will have two 60A 24V charge controllers on it, so I calculate average 14KWh solar charging... figure setup 5KW panels so max input throughout the day...
but, 30KWh of lead minimum has charging challenges. SLA isn’t much cheaper than LFP.
LFP doesn’t outgas, but has low temp charging limits, and he is planning this for mountain use... so low temp is a concern.
heating that large a trailer is going to waste a lot of watts... the inverters are in the same area as the batteries, so 10Kw 3Phase under load will put out some heat, for sure... I fear mornings will just be too cold for LFP.
MAYBE he should use SLA and monitor the temps in the trailer under use this winter, and go to LFP later if the temps behave.

LFP with low temp monitoring would prevent damage to them, but also, limit how much charging could be done, if they are getting cold.

thoughts?

Recommendations?

 

[rhino]

Any idea on what the minimum temperature will be? -20F air temp would be a lot harder than 20F .. If you did want to use LFP it would be a lot easier to heat a well insulated battery box within the trailer instead of the entire trailer.

 

[Supervstech]

Need solar tech help

We are a ministry that helps with first responders, veteran's, and people with PTSD. We have just acquired a Zerobased Forge solar trailer, with 3 Outback VFX325M inverters, and 2 Outback battery monitor/chargers. We also have a dozen Sunpower SPR-210-WHT-U panels. We need somebody to help us...

diysolarforum.com

This is the member, and his thread on the job.

 

[2009Bounder2020]

i would go with agm Keep it simple for the userbase

 

[Bruce Wilkinson]

Thanks Supervstech for all you help on this........... I have been asked how will the trailer/solar generator be used....

There are 2 main use profiles for this unit.

1st use case is in Disaster Recovery operations. Since we are in North Carolina most of this revolves around floods and Hurricanes which generally come in the summer and fall time frame. Temps during this time will range from the 50s as the lowest and the high 90s for the hottest times.

2nd use case is for our Wilderness program. Part of our minmistry is working with Combat Vets and First responders recovering from PTSD or other trauma. Part of our process is getting out into the "wilderness" away from cell phone, internet, and distractions. We feel that this allows them to see and experience God and His love for them in a more personal way. In the past we have used the Appalachian and State Parks and gone backpacking into the more remote areas around us. We have found that this excluded some of our men and women that have medical issues that require electricity (like CPAP, insulin pumps, etc). Also the cold weather weather in the mountains forces some to opt out. We will use this trailer to provide electricity in these wilderness places allowing us to take on more people with more diverse sets of needs. This will help us open up that wilderness to a larger set of people. Since this will include winter use the temps for this use case range from the low teens in the winter and the low 90s in the summer.

I hope this helps - it both use case we would want to at least power a 50 amp RV or two - lights, power tools, etc. If there are any other questions, please let us know - thanks again Supervstech.

 

[HaldorEE]

If the system is going to be used by multiple people, I would vote for AGM. If you don't know what you are doing it is easy to ruin a lithium battery pack. Everybody knows that batteries are supposed to be kept topped up. Doing that to lithium shortens the life of the battery.

And I know it shows that I am a bad person, but first thought I had at "Military", was to use LiNMC. You get way cooler secondaries that way.

 

[Supervstech]

Any idea on what the minimum temperature will be? -20F air temp would be a lot harder than 20F .. If you did want to use LFP it would be a lot easier to heat a well insulated battery box within the trailer instead of the entire trailer.

Since we are likely talking east coast mountains at the worst is 5 below F...
Figure the box is 24x48x72 HxWxL
The trailer is aluminum... there is 1/2" rubber on some surfaces, and it likely could be insulated better.
The inverters will certainly heat the space... assuming they don't deplete the batteries overnight, so a cold protect setup should be enough...

 

[Supervstech]

The next issue is getting the system running

We attached batteries, and solar, and the CC'S Are working, and the display shows watts in and battery voltage rises accordingly...
But we cannot figure out how to get the inverters operating.
I can manually trigger the relay, and they operate, but the outback controllers do not seem able to start them.

 

[Supervstech]

Check my math...

Two60 Amp 24V controllers... so 2880W input maximum.
he has many 44V 210W panels, so wi5 a 50% over panel, that means what...20 panels on the rig...
2880W charging will support 17,280 Wh of storage... average 6 sun hours...overpaneling should help that a bit, but to be sure... 17,280Wh charging.
So with lead acid he would need minimum 34,560Wh SLA since this is for disaster recovery, double that for runtime aid...
That’s 69,120Wh or 5400AH of 12V SLA... anybody have a price on that much?
Lithium would be 1/2 the needed capacity due to the discharge abilities...
So, 2700AH lithium.
i hav 4 BYD 24V 3ish KWh banks. That’s 12KWh... a good start and a cheap learning setup.
I will price up BYD, AGM, and new LiFePO4

 

[Supervstech]

Ok, I was calculating on 24V... since the max charge voltage is 29.2, the max wattage charging would be 3504, not 2880
So... kinda gives a little more capacity.
Should support 21,024Wh...

 

[texskeet]

Those bankrupt batteries would work great bet you can get them cheap.

 

[texskeet]

may be just buy the whole reailer.

 

[Supervstech]

I never posted the results! My bad.
I will dig up all the photos, but 4 paralleled at the cell level, split between 2 Daly 150A bms units.
I installed a trigger switch for the inverters, and they function flawlessly.
Power my air compressor, saws, lights, etc. No issues.
Only one charge controller is functioning...
So his charging from solar is limited to 3 strings.
Hopefully, outback tech support can repair the second one so he will have more power available.
I built a 240V connection cord that plugs into the ac output connection. The cord feeds an outdoor RV outlet panel.
It has the requested 240v 50A outlet, on a gfci breaker, and a 120V RV 30A outlet on a gfci breaker, along with a 120V 20A gfci outlet.
The dalys trip when the inverter is powered on, but a battery cycle brings them up.
I figure the caps need a precharge resistor, so that is next on the agenda...

 

[Supervstech]

Ok, another issue with the trailer.
One of the charge controllers wasn’t waking up. They found instructions, so I went over today and investigated my work...
looks like I missed a negative sense wire, and now that it is properly connected, both charge controllers are working!

another issue is when they run the loads overnight, the batteries reach 3V per cell, and the BMS drops out.
we checked he overnight loads, right at 1100W, so it makes sense the banks are depleted in 12 hours, but waking the BMS up requires battery and P negative short... so, kind of a pain...