LiFePO4 - battery bank on bus - which is best solar panel solution ???

[Rober williams]

I am new here, have scanned for bus installations with apologies if I missed one. Bus is unusual. RCL Route Master Play Bus with Wurlitzer juke box , classic Coke machine, internal lite up posters, internal lighting all running on a 24 VOLT LiFePO4 six battery bank with 3000 watt inverter providing 240 VOLTS and 24 VOLTS when needed. The bus also has it's two standard 130 amp-hour batteries to turn it over. Has a three-way automatic charger, using two of the automatic ways to select between the lithium bank and the standard batteries via a split charger. The bus can plug into a 240 VOLT source like a caravan, where the split charger does its magic ,charging batteries most in need first, or it charges weaker batteries off the alternator when in motion. Just so you know I am serious here. (As a side issue, the engine runs on a two tank veg oil system.) We are renewable energy fans.

My question: In rare circumstances where the six LiFePO4 are run flat, or if the 130 amp pair need charging away from home, in your experience what configuration, make or model Solar Panel(s) would you recommend to charge either/both these 24 VOLT systems?

Would imagine being able to switch what comes off the panel, to concentrate the extra power where it is needed. Looking for the best performance and value panel, obviously.

Note to consider : Route Masters have a slightly curved roof.

[jflorey2]

My question: In rare circumstances where the six LiFePO4 are run flat, or if the 130 amp pair need charging away from home, in your experience what configuration, make or model Solar Panel(s) would you recommend to charge either/both these 24 VOLT systems?

What load will you need to support? (watt-hours per day)
What roof area do you have?
What are the charging requirements (voltage, current limit) of the battery? (I would assume 28.4 volts/.5C but make sure)

[Rober williams]

Off the top of my head, close if not spot on.

1.Juke box says 250 Watts, Coke machine, like a fridge, 40 Watts Lights are LED so not high Lets estimate at 300 Watt total. Important to note that the solar panel will act as an emergency backup. Everything runs well already.

2. Roof total is 8 feet by 30 feet. makes it 240 square feet available

but would like to keep it down to 15 sq feet, 5by3 feet perhaps

3. 28.4 volts sounds about right. I think the lithiums require 29, they have a special charger like they use on boats.

Thanks for your interest

[AzRoute66]

I think the only thing I can contribute is that your roof is not as large as you think. There are things sticking out of it, things that create shade, things to be avoided. You can try to maximize the coverage by doing a survey. In other words, if you try to maximize collection, the physical panel size might be your largest consideration - which is usually a minor point in a roof or ground mount. Some Legos just won't fit well on the baseplate.

Almost all of these installs work best with no tilt at all since one is never sure how one will be parked. I saw a very nice bus install the other day. They had two rows (columns?) of panels, one running lengthwise down the left side and one running down the right. If they were fortunate enough to be parked on a pretty much East-West line for a period of time, they had the inner-most mounts hinged and the outer-most panel mounts tiltable, so by just using a small ladder they could tilt up the panels on the north side to face more south without ever getting on the roof.

[Rober williams]

The bus is 8 foot wide and 30 feet long, so the roof is 240 sq feet, but I really want to keep it down to 15 sq feet, or 5 by 3 feet.

What I am hoping for is what manufacturers you recommend, and what specks. How much power it needs to generate, what would you install with your experience??? there must be several good ways to accomplish his, but only one best way. What would you say is best ?

[Mike90250]

.... all running on a 24 VOLT LiFePO4 six battery bank.....

How many Ah is the Li pack rated for ?
How fast do you want to recharge it ?


The bus starter @ 24V 130ah - should be charged at 10% of it's Ah rating, at 13-15 Amps, to get that from solar @ 29V charging, would be 435w delivered, from about a 650w PV install.
This is enough wattage you would want to use a MPPT charger, with about 50 - 90V solar array

You would NEED to re-configure the charger each time you change to the other battery, the charging specs are close, but NOT the same. Or charge the starter battery off the solar charged LFP with a ballast resistor and Jumper cables.

The Biggest problem, is to prevent the LFP pack from being deeply discharged, so you will need a LVD to trip at your desired voltage.

( Do you need jargon translated ? )

[Rober williams]

How many Ah is the Li pack rated for ?
6 batteries, 110 amp hour each, wired to produce 24 Volts

How fast do you want to recharge it ?
12 to 24 hours

Imagine the bus in a field. The solar panel would be for emergency use. It powers up to 5 days alreadty

[AzRoute66]

[...], but I really want to keep it down to 15 sq feet, or 5 by 3 feet.

If you can go just a skosh over that you can have one GT panel. That will put you in range of a MPPT controller that will fit in the palm of your hand. Calculating your panels first has helped you eliminate many unrealistic scenarios.

[Mike90250]

660ah @ 24v = 15840kwh, of which, with prudent top & bottom reserves, gives you 11088kwh usable. You could charge up to 100A into that bank without a 2nd thought, more if you monitor carefully.. Depends on how low it gets, how long it will get back up to full.