2000 Watt (1500 Watt), 24v Off-Grid Solar Power System - 1989 MCI 102AW3

TedH

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Jun 5, 2020
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Greetings everyone.

I started several threads about the different components of my 'BUS' solar system. Am going to try to keep my posts to this forum/thread going forward as it is a total system and am trying to keep my conversation in one place.

To start, my bus has a considerable amount of existing RV conversion wiring, power and load generating components. It is equipped with an on-board, 7Kw kubota diesel generator for dry camping power, 50amp shore power cable for camp ground connection and, with the bus running, can power the 24v, 3000watt AIMS Inverter/Solar Charger (includes MPPT) from the two 8D, 12v lead acid starting batteries in a 24v series. So, at this time, I have three power sources: 7Kw diesel generator, shore power and onboard 24v power system.

I have a selector on the shore and generator underneath the bus at the generator so that I can select (manually) depending on if I am boondocking or camping with power connections. Up inside the bus, I have a plywood 'power wall' which has the following:

50amp main switch
50amp selector to switch between the Inverter OR the shore/generator
50amp breaker panel - all 120v appliances
3000watt AIMS Inverter/Solar Charger (MPPT) - produces a stead 30amp power supply to the 50amp selector switch
120v to 12v converter that powers the 12volt 'house' systems breaker panel (water pump, shower tank, fridge, lighting, etc.)
12v AGM battery for the onboard 7Kw diesel generator
Copper cabling between the bus batteries and the 24v Inverter, 120-12v converter and 12v AGM and other leads.

I will be preparing a detailed grid/diagram of my existing systems and the changes I will be making to introduce the Off-Grid Solar Power System:

I will be adding the following components of the Off-Grid Solar Power System:
Six (6) 250watt polycrystalline solar panels with associated cables and 15amp fuses - mounted on roof of the bus, flat and mounted on rails.
Victron Battery Balancer and Monitor (Is this the same as a 'Battery Protector'?
24v battery pack - a set of eight (8), 3.2v, 100Ah lifepo4 cells with BMS and low temp protection
4ga Wiring with fuses, junction blocks and other misc connectors to connect the systems
I intend to leverage the MPPT feature in the AIMS Inverter to process the power from the solar array and to maintain the lifepo4 battery packs
 

TedH

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108
I realize that I am going to have to disconnect the direct connection from the bus 24v batteries from the inverter and put a switch in to select either the bus battery power or solar batteries power to feed the inverter side of the AIMS unit. Also, that I will have to be careful to first turn on inverter, then power then load so that it is not overwhelmed. I intend to study the current connections since the charger side of the inverter is NOT currently in use/connected to anything; it is solely used to invert the 24v DC bus battery power to a 30amp power source for the house electrical systems.
 

TedH

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Quick update:
After studying the features and capacity of the solar charger/MPPT built into my 3000watt, 24v AIMS Pure Sine Inverter/Solar Charger, I have decided to purchase: Aims Power SCC60AMPPT 60 AMP Solar Charge Controller 12V - 24V - 36V - 48V with MPPT.

I will continue to use the 30amp inverter feature of my AIMS 3000watt Inverter. The new solar charge controller will support up to 1700watts of PV solar panels (at 24v) while having the benefit of tuning the charging profile to suit the lifepo4 cells that I am building two, 12v 'batteries' that will be in series. The new controller will be mounted on the power wall inside the bus living area.

I have also purchased a Victron Energy battery balancer and battery monitor BMV-712 Smart (bluetooth). The balancer/monitor, lifepo4 batteries and BMS will be assembled in a hinged storage bin in the belly of the bus.

The panels and solar charge controller arrive later this week. The lifepo4 cells and 8s BMS will arrive later in June.

The rails and hardware to attach the solar array to the roof of my bus will be sourced in early July.
 

TedH

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Jun 5, 2020
Messages
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When I introduce the solar charger controller, I intend to disconnect the 24v power leads between the AIMS Inverter and the two, 8D bus batteries and connect instead to the lifepo4 batteries. In the future, I may re-introduce power leads from the two, 8D batteries behind an automated switch that will switch between the solar power, generator/shore power, and the 8D bus batteries (or the solar power and generator/shore power, leaving the 8D batteries out of the equation).
 
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TedH

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I found a 10-pack of 8s, 9-pin color-coded harnesses for $8 on Amazon.com. I will be using to plug in the BMS and/or the handy $15 CellMeter 8 Battery Voltage Capacity Checker, Balance Discharger/Servo Tester. I plan to run the 9-pin harness into a bus bar the BMS leads will connect to. The BMS handles 7s-16s so it has two, 9-pin connectors. Looking to clean that up.

The 10-pack 9-pin harnesses on Amazon: https://www.amazon.com/gp/product/B01EVINO72/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1
 

Ampster

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I plan to run the 9-pin harness into a bus bar the BMS leads will connect to.
I am not sure i understand the purpose of adding an extra connection to the bms wires. You will introduce possible extra resistance the could create voltage differences from cell to cell. If you want to connect two devices it would be better to run separate wires.
 

TedH

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I found that the 8s BMS doesn't use a single 9-pin connector. it uses a pair of 9-pin connectors and wires from the two connectors will connect to the battery.

For connecting the 8s BMS to the batteries, I will run the selected 9 leads from BMS to the battery. The 8s BMS comes with bluetooth and I can get the app for it once the BMS arrives.

I want the option of a 9-pin 'test harness' connected to the battery to easily connect the CellMeter 8 when I choose to test the battery packs; disconnecting the CellMeter 8 when not in use and leaving the harness attached to the batteries for easy connection .
 

Ampster

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I found that the 8s BMS doesn't use a single 9-pin connector. it uses a pair of 9-pin connectors and wires from the two connectors will connect to the battery.
I thought you said that BMS was a 16S BMS. If you are only using it for an 8S battery you would not need the extra connector.
Do you understand my point of two separate 9 pin connectors to the battery?
 

TedH

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It is a 16s BMS. However, the wiring diagram shows to use it as 8s, that wires from both 9-pin connectors on the BMS will run to the cells.

1592497663205.png
 

TedH

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Messages
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I am adding two (2) DC power switches to my system plans.

One switch will be between the (POS) Solar PV power lead and the Solar Charge Controller and the other switch will be between the (POS) Battery Lead and the Solar Charge Controller. I want to avoid any problems when connecting/working on the solar, battery and charger systems. I already have a switch between the 24V Load (24V, 3000W AIMS Inverter) and the existing 8D batteries on my bus that I will re-purpose to isolate the Inverter from the Solar Charge Controller.

I am still thinking over the option of putting a 3-position switch to select 24V from Bus 245amp charging system or the 24V from the Solar Charger to feed the Inverter. It would come down to whether I would really need it (cloudy day driving, batteries low and I need to keep the house systems running).

PV operating voltage 34-155Vdc @ 24V
Max PV Open Circuit Voltage 155Vdc
Rated PV input 24V 1700W

Blue Sea Systems 300 Amp: https://www.amazon.com/gp/product/B00445KFZ2/ref=ppx_od_dt_b_asin_title_s00?ie=UTF8&psc=1
 
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TedH

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Any experience with 'Automatic Transfer Switches'? I may need one if I am to reliably flip between power from Inverter (solar or bus) and shore/generator.
 

TedH

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I need a reliable transfer switch for my bus to switch from 30amp solar to 50amp shore power.

the following switch only works with a Generator/shore power. Not Solar: PowerMax PMTS-50 50A Automatic Transfer Switch
 
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TedH

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Just received the notification the 50A ATS mentioned in my prior post shipped. Watched Will's video using the 'generator' side of the ATS for the 30amp inverter/solar AC. Will install and see if it works ok. Will advise.
 

TedH

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I purchased a Victron Battery Balancer as I thought I would need it to protect the two, 24v battery packs I am building using the 3.2v, 100ah CALB cells. I am using an 8s BMS across the two packs of 8 cells.

My question: Is the Battery Balancer redundant given I am using a BMS across the 8 lifepo4 cells? I think it is.
 

TedH

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Since posting, I decided to increase the system from 2.4Kw to 4.8Kw. I ordered a second set of eight, CALB 3.2volt, 100ah cells. This will be my second 24v battery and will double my system from 100ah to 200ah. I also ordered a second BMS for this battery pack. Also, in meantime, I have purchased in-line fuses, DC on/off switches, 4gauge cabling (TEMco), 8gauge PV cabling to run from panels to the power wall inside bus (via a plastic 'gland' on roof), dryer vent clamps to assemble and combine the batteries in my battery enclosure, heat shrink connectors and tubing, zip ties, other misc hardware and several tools that I identified during the course of purchases to trim/cut/assemble the wire, connectors and cabling.
 

TedH

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Are you upgrading to a 48V system? How is that going to work with your inverter?

I am adding the second 24v, 100ah pack in parallel to the first pack. It will result in a 24v, 200ah battery configuration. I will have two batteries in serial configuration in the two parallel packs.

I am preparing wiring diagrams on my computer this weekend and will share images of my setup next week.
 

HaldorEE

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I am adding the second 24v, 100ah pack in parallel to the first pack. It will result in a 24v, 200ah battery configuration. I will have two batteries in serial configuration in the two parallel packs.

I am preparing wiring diagrams on my computer this weekend and will share images of my setup next week.
16S BMS won't work like that. A 16S BMS is for a 48 V battery. You need two 8S BMS, one for each string.

Or you could create a single 24V battery consisting of 8 series connected pairs of cells, each pair in parallel. That would work with a single 8S BMS, but that BMS has to be able to handle double the current.

I would use two separate BMS. That way you have created two independent batteries. If one dies you have less capacity, but are not shut down completely.
 
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