alternator and mppt

[native pepper]

Friend has a 2 cylinder small kubota diesel engine, we bought 8 ex army ones at an auction about 10 years ago, mine still sits on the workshop floor unused. He has 2 x 60amp alternators attached to it charging an array of different size agm's. Yesterday dropped off his 1000ah of new lifepo4 cells, helped him connect them all up, along with the mppt's and equalisers, which took all day.

Connected his panels to the system and then he asked if he could run the kubota through the 60 amp mppt as a backup. Had had to tell him didn't have a clue, have thought about it myself, by using a 24v to 12v dc-dc charger. but yet to get round to doing it.

If anyone can help give him and answer, would be greatly appreciated. However think when he has used his lifepop4 for a couple of weeks, he won't need it.

[BruceS]

For anyone to really answer the question I think they may need to know ..
what voltage (nom) are the batteries configured to?
What voltage are the alt's on the Kubota? I'm guessing 12V?
I'd be inclined to attach a 240V generator to the engine (s) and either run it through a Combo unit or a dedicated battery charger.
That way if there is an unplanned breakdown it can be used as alternative power.
I have my Houseboat wired up like that. Simple changeover switch. (never needed it yet but .....)

[native pepper]

It's all 12v Bruce, he's been advised to put a genny on the engine, but has had this operating for a few years and likes the idea of it almost idling to produce power, while with a 240v genny it would be high revving, using more fuel and noise. Plus car alternators are very cheap and freely available, he has quite a few.

Before we got the engines he had a single cylinder hatz diesel doing the same thing, but it wasn't designed to run at low revs and packed it in after about 10 years.

[BruceS]

It depends on what generator is attached to the engine.
Wendy used to own a little Diahatsu Charade car that had a 3 cyl engine that red-lined at 6500 RPM.
I now have a generator on the houseboat that has that same engine powering a generator but only runs at 1500 RPM. (idling?)
In the car it got 65MPG quite often.
Most 'ordinary' generators run at either 1500 or 3000 RPM. (USA ones are 1800 or 3600RPM) Inverter types aren't so particular.
I'd reckon a 1500 one connected to a Kubota would be so economical ................

[native pepper]

Thanks Bruce, the kubota runs best at 850rpm for him and produces 105amps @ 14v, which is probably all these old alternator he uses can produce. It uses 1 lt per 2 hrs he says, which is pretty economical and is extremely quiet at those revs, as it sits under his house in an insulated room. Just flicks a switch inside and off it goes, you can't hear it unless you go down under the house then all you hear from the room is a low purring sound, the exhaust goes through a series of tanks and water/grease traps and exits away from the house into a grey water pond. That agitates the pond which dislodges all the crap in their grey water and then it goes through some filter beds and into a holding tank for the gardens.

He scrapes the crap off the top of the pond and buries it and has a lift out junk basket in the pond which is cleaned regularly and put into the compost tanks. He's a retired plumber and makes some cool stuff for his property, has water features everywhere and a recirculating waterfall from one of his dams, which runs on solar and will become a small pump hydro generator. He also has a solar hot water heater on his bus he made, which have been meaning to replicate, but never got round to it, the lifepo4 and bus engine heat our hot water.

My old 1500rpm single cylinder 5kva lister genny uses just under 1lt per hr for most things, but 1.5lt per hr when using a mig. Can't see why a 2 x 60amp mppt controllers wouldn't handle it, but not being very smart when it comes to electrical stuff, can't say whether it would work. The only problem I could see is whether the controller can handle a constant 55amp input over many hours, then again there may be other factors which would make it unviable.

Like myself, he likes to make things from scrap and has lots of weird stuff he's made around the property. We both have large amounts of future useful stuff we've collected, it's rare for me to have to go and buy either metal or wood and with a transfer station just up the road, have access to lots of thrown away junk. People drop off their green waste at our place, which saves them dumping fees and the transfer stations sends them to us now as they have no room. So have a couple of huge in ground compost heaps which not only provide great compost, but also heat water.

[Dibsy]

1000 amps of lithium wow I wish lol he could do away with the fuel powered generator and run it of the batteries .

Dibs

[Wilbor]

Why can’t you connect the 105amp alternator direct to the LiFePo4 and keep a close eye on their voltage?

[native pepper]

Dibs, he has a large workshop, with a heap of 3phase equipment and runs those via the kubota/agm and motor controllers. His 1000amp lifepo4 is purely for his house, which is huge and as he has 4 teenage girls, one boy and a crazy wife, they tend to use a bit of power.

I run my 3 phase centrifuge on 12v/inverter/motor controller, unless using the lister. Have a 6kw 3 phase genny which has never been started as this system works really well and have only gone through one motor controller on the last 10 years.

Wilbor, after 11 years using lifepo4, have learnt to treat them gently and learnt long ago unregulated charge into lifepo4 can leads to problems down the track. Know a number of people whose lifepo4 after 3-5 years have lost around 20% of their capacity using lead acid chargers and unregulated/unbalanced charging. So far my packs have lost nothing I can detect and they perform excellently, they are always in balance, never given small charge inputs close to upper voltage parameters and never go over 3.5v per cell or below 3v per cell.

Tried unregulated inputs years ago, using switch relays and standard chargers, you could see from the beginning the cells weren't happy. Now everything runs smoothly, so I'm happy with my setup as my mate hopefully is. He wanted to wait until lifepo4 was proved viable, but knowing how long I've had them, he finally conceded they had proved themselves. Now just have to wait for how he feels after using agms for the last couple of decades and now lifepo4. If he is like everyone else, will be blown away by the difference.

[Dibsy]

Good report pepper . Wonder how much 1000 amp would cost that long ago

Dibs

[bagmaker]

as long as he runs it through the MPPT - AND the MPPT is set for LiPoFe voltages - should be no problem.
Not knowing the type of alternator? could be an issue running at full output if the MPPT can use it (60a?)