DC Generator

[Bob Cofer]

In the process of upgrading/updating Solitude I have come across a Panda AGT-4000 DC Generator.

These were set up to charge FLA banks of batteries. My bank is LiFePO4, 920ah at 12.8v. I got in touch with FischerPanda in Germany as they are the manufacturers and asked them about converting this for use with my battery bank. They advise adjusting the voltage and current output via the VCS.

As far as I can tell this is some uncharted water and I am all for experimenting but the $$ invested in the batteries has me a bit hesitant. Has anyone done this before?

The reason for installing this is to not have to run a generator for our AC loads. I have installed a Victron MultiPlus-II 3k Inverter for our needs; (cooktop, ice maker, coffee maker) and would use this generator to quickly recharge the house bank when needed. It looks like I can get 14.4 volts and 280 amps out of the generator at full capacity.

As far as I can tell there is no multistep charge profile so it would just be blast to capacity. Any thoughts or advise would be appreciated.

Regards,

 

[SteveK]

Adjust the voltage? any more info from them of what they meant. 14.4 is acceptable top end for most LFP. How did it know when FLA was fully charged? I like the 280A charge.
You could manually shut it off by clock time prior to 100% SOC based on SOC at beginning?

 

[DDW]

Do you not own the Fischer-Panda yet? They have a very poor reputation for reliability. You may want to research that before making a decision.

 

[O C Diver]

While I have no experience with that unit, could you simply replace the voltage controls with an external regulator like a Balmar or a Wakespeed?

Ted

 

[Bob Cofer]

Adjust the voltage? any more info from them of what they meant. 14.4 is acceptable top end for most LFP. How did it know when FLA was fully charged? I like the 280A charge.
You could manually shut it off by clock time prior to 100% SOC based on SOC at beginning?

Here's what I got from them:

The AGT 4000 you have is basically designed to charge a lead acid battery.

you can adjust the charging voltage and current at the VCS from your pictures.

the open circuit voltage can be set at the adjstment screw next to the input for the voltage measurement.

Still digging for more info on these parts

 

[Bob Cofer]

More Info

 

[tiltrider1]

I am just a bit confused. You own a Multipas II so you could use an AC generator and not worry about this, unless there is some other issue I have missed.

 

[Jeff F]

The multiplus has a maximum charge rate of 120a, so requires more than double the generator run time vs 280a DC for charging.

Lifpo batteries will accept a high charge rate, but it's not easy or cheap setting up AC chargers to deliver a 4 kw charging current.

 

[twistedtree]

I would not do it for a couple of reasons.

First, as DDW mentioned, they have a horrible reputation for quality and durability.

Second, LFP batteries need accurate voltage regulation, and at least 2-stage programming so they will back off to a float voltage after reaching bulk. The Panda appears to be fixed voltage output only, with no remote voltage sensing.

I would instead spend my money on more AC-powered chargers to supplement the charging capability of your Multi. If it's the model I think, the multi will charge at 120A. Add 100A charger and you have the same charge capacity as the Panda, but using your existing generator. And the charger will be cheaper, much easier to install, requires no maintenance, and will be much more reliable than the Panda. You could even install a second Multi used only for charging and get a total of 240A.

 

[tiltrider1]

I would not do it for a couple of reasons.

First, as DDW mentioned, they have a horrible reputation for quality and durability.

Second, LFO batteries need accurate voltage regulation, and at least 2-stage programming so they will back off to a float voltage after reaching bulk. The Panda appears to be fixed voltage output only, with no remote voltage sensing.

I would instead spend my money on more AC-powered chargers to supplement the charging capability of your Multi. If it's the model I think, the multi will charge at 120A. Add 100A charger and you have the same charge capacity as the Panda, but using your existing generator. And the charger will be cheaper, much easier to install, requires no maintenance, and will be much more reliable than the Panda. You could even install a second Multi used only for charging and get a total of 240A.

This is what I have done. My Magnum inverter puts out 100a for charging. I bought a Li-Time LFP charger that puts out 80a. Between the two I run the generator 3 hours out of 24. I could have gone bigger but the generator is going to run 3 hours anyway so the 180a worker out.

 

[Bob Cofer]

I would not do it for a couple of reasons.

First, as DDW mentioned, they have a horrible reputation for quality and durability.

Second, LFO batteries need accurate voltage regulation, and at least 2-stage programming so they will back off to a float voltage after reaching bulk. The Panda appears to be fixed voltage output only, with no remote voltage sensing.

I would instead spend my money on more AC-powered chargers to supplement the charging capability of your Multi. If it's the model I think, the multi will charge at 120A. Add 100A charger and you have the same charge capacity as the Panda, but using your existing generator. And the charger will be cheaper, much easier to install, requires no maintenance, and will be much more reliable than the Panda. You could even install a second Multi used only for charging and get a total of 240A.

There currently is no generator aboard Solitude. I have two Panda generators sitting in my shop, one 8kw AC and one 4kw DC. The DC generator has a much smaller footprint and will easily fit into the lazarette. The AC unit would have to go into the ER. The infrastructure is in place for either one. It is an interesting exercise to figure out if the DC unit can be made to work for this application.

 

[DDW]

Well, you can always put the Panda in and then use a DC-DC boost-buck converter with all the fancy regulation you want. Will take probably two paralleled. Crank the Panda voltage up as high as it will go.

 

[Jeff F]

If the only purpose of the generator is to charge the house bank on demand I think it could be done without further regulation, assuming close monitoring and common sense. Just use fixed voltage and shut it down before the battery reaches full charge.

That assumes you have other charging sources that will deliver regular top charges for balancing.

 

[slowgoesit]

Google Fischer Panda generator problems . . . . There's hours and HOURS of reading available.
Having said that, if you already one two of them, it's worth a shot, at least for as long as they keep running . . .

 

[Lepke]

Why not a small diesel AC generator. Then you're using the charger system you have now.
If cost is an issue, there small air cooled diesels on ebay, also generator ends.
Someone usually has used military portable AC or DC generators that put put 2kw 120v for about $2500 or the same in 28 VDC that you could regulate or transform into 12v charging for $1000.
And there are many new small diesel engines that could run the Fischer Panda generator end.

 

[SteveK]

I think some of you missed that Bob already has two of these engines and wants to repurpose one to charge the house bank.

AS long as the 280 amps does not exceed the input charge limit, then it seems the random voltage spikes could shut down an LFP bank.
How to prevent that then is the problem to solve.

 

[O C Diver]

At a point in time when I had considered a smaller boat primarily for the Erie canal and the Great Lakes, my thought was to avoid a generator. The plan was to have a second alternator with an external regulator. The alternator could produce full output at an engine speed of 1,200 RPM. For lithium batteries, the external regulator is programmable for slow ramp up to avoid BMS problems. Amperage sizes at 12 volts are up to 300 amps. Also, I would only consider a commercial rated alternator for full engine RPM and the ability run run for a few hours with full output at 1,200 RPM.

Ted

 

[Iggy]

I get it! The op has the generators, so why not use them. But it makes thing more complicated. More of a safety issue I think.

I like TT thoughts on this. The OP can always sell the Pandas to pay for a charger/inverter.

 

[twistedtree]

There currently is no generator aboard Solitude. I have two Panda generators sitting in my shop, one 8kw AC and one 4kw DC. The DC generator has a much smaller footprint and will easily fit into the lazarette. The AC unit would have to go into the ER. The infrastructure is in place for either one. It is an interesting exercise to figure out if the DC unit can be made to work for this application.

OK, I misunderstood and thought the AC generator was already installed and in use.

I think I would still use the AC generator rather than the DC. You will have more power available with the AC unit, and I wouldn't want to risk issues with inaccurate, un-flexible charging control. You already have 120A of DC charging capacity from your inverter, and just need to add 100A or so more.

 

[Barking Sands]

Somewhat related. I recently spoke with Reid Loessberg at Intelligent controls and he turned me on to this very cool Hatz diesel DC generator that can interface with Victron systems for start and voltage controls. Its very slick, and with these large battery banks and inverters seems like a very viable option.

 

[SteveK]

A DC generator certainly has peaked my interest in the concept. We all know that making AC to feed a charger that converts to DC loses some in the transference. Why not go direct to the battery and let the inverters handle the AC loads. This may catch on.

 

[DDW]

I think one problem with the concept is that alternators, particularly running at 12V, are very inefficient. Lots of resistive loss in the windings, and high percentage loss through the diodes. Better at 48V, but better still at 120VAC - 1/10 the current (and associated I^2 loss) and no diodes. There used to be a number of these products sold to the sailboat crowd, of which the Panda was the most widely known.

The advantage of the DC gensets is they run at a load dependent speed, rather than flat out all the time. However some day marine gensets will enter the 21st century and operate like Honda suitcase generators: 3 phase output feeding an inverter to generate the required voltage. There have been a few, but not from mainstream OEMs.