LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

[ebaugh]

Originally Posted by Dsanduril

Steyr/Iskra IFG into LiFePO, wow, I'm envious, and glad at the same time to not be that close to the edge.

If you want to play with the very expensive equipment, it looks like they use a jumper to switch between 13.8 and 14.3 constant voltage. I wonder if that jumper is just bypassing a resistor in the internal sensing circuit? If that's the case you might be able to open the thing up and change the resistance value. I would want to do that kind of tinkering, but there's a lot of $/£/€ on the line, and they're not mine, so that's easy to say.

I missed that. If not already using the gel position with this jumper, I'd try that before adding the diodes. It would probably greatly reduce the power output. If it worked that way, you could also put a toggle switch in there, to go to full charge. But the BMS OV would need to turn it off somehow in a way that requires a manual reset to go back to high mode.

[ebaugh]

Originally Posted by jff

Greetings all

The major issue I have is with charging, in a marina my Victron 50A charger works fine, and is turned off by the bms system,but anchoring out is a problem.

John

How does the BMS turn off the charger. I think the OV output resets when the voltage falls. Does this cause the Victron to keep coming back on at dock once the battery is fully charged? You don't want to float at 3.6 volts.

[T1 Terry]

The down and dirty fix while you wait for the makers to get their act together is to put 2 x 12v agm batteries in series to make 24v and fit them in parallel to the charging circuit of the regulator. This will trick the regulaor into thinking it's charging an agm battery, the agm will keep draining off the charge it receives to the lithium batteries.
Does the GenSun BMS have a low voltage charge cut system like the one that cuts the mains charger? That connected between the AGM batteries and the lithium batteries would protect the lithiums from over charging and the regulator from seeing nothing, it would see the agm batteries. If you do go to the 24v starter for the engines the batteries will have a use there and if the regulator manufacturer can't get their act together you could leave the whole thing hooked up that way.

T1 Terry

[jff]

Thanks for all the replies

I'll try hunting down some diodes tomorrow, and if all else fails, I have a pair of gels that I left installed for emergencies that I could route the charge through.

cheers

John

[downunder]

Great link here.


Someone who has done a conversion well illustrated.


http://psyberspace.com.au/lithium.html


Cheers

[Lagoon4us]

With 42,000+ lookers at this thread there is a lot of interest over a long time...

The link you posted brings it down to brass tacks, the guy has used a low voltage cutout and carefully checked his upper charge voltages to be certain all is within acceptable limits.

He also says that with small installations like these there's no real need to have a sophisticated BMS.

A couple of other questions that would help me to learn the basics are :-
1) Do we need to isolate other batteries from the Lithium bank eg lead acid start batteries, thruster batteries and such.
2) Will Yanmar/Volvo standard alternators with their standard built in regulators suffice?
3) With the setup this guy used will he have to do cell balance checks at some time interval?

Great article good info within...... Cheers Frank

[witzgall]

Yes, you need to isolate. The best setup, imho, is a start battery charged by an echo charger, and a single, series/parallel house bank.

A built in alternator/regulator will not last long if the batteries are deeply discharged. YOu really should have an external regulator, mounted outside of the engine compartment, and tweaked for LIFEPO4. A alternator temperature sensor is nice as well.

Originally Posted by Lagoon4us

With 42,000+ lookers at this thread there is a lot of interest over a long time...

Like anything else on a boat, it should be checked on a regular basis. I hope to install a cellog soon, so I can read the instantaneous voltages of all eight of my cells.

Chris

The link you posted brings it down to brass tacks, the guy has used a low voltage cutout and carefully checked his upper charge voltages to be certain all is within acceptable limits.

He also says that with small installations like these there's no real need to have a sophisticated BMS.

A couple of other questions that would help me to learn the basics are :-
1) Do we need to isolate other batteries from the Lithium bank eg lead acid start batteries, thruster batteries and such.
2) Will Yanmar/Volvo standard alternators with their standard built in regulators suffice?
3) With the setup this guy used will he have to do cell balance checks at some time interval?

Great article good info within...... Cheers Frank

[Lagoon4us]

Thanks, naturally we have two engines with seperate but connectable batteries. The anchor winch i believe runs from the port start battery and the thruster battery is interconnected to this circuit so initially i need to check that this is the setup and isolate this from the house bank and wiring.

So you are suggesting that the start batteries be charged only by an 'ECHO' Charger so there is no engine alternator charge circuit to them? ie the alternators charge the house bank?

Apologies if the questions are simple i'm just trying to get a handle on this... Cheers Frank

[witzgall]

Yes, alternator running to the house battery only. Then, you can have a simple on/off switch for the house bank, and a separate switch to combine in an emergency if you want. Our second switch is one of those plastic key switches. It is a great setup, simple, and easier not to make charging mistakes.

Chris

[witzgall]

Make sure you have an ANL fuse on the lead from the alternator to the house bank, and between the house bank and the house loads!

Chris

[T1 Terry]

Originally Posted by downunder

Great link here.


Someone who has done a conversion well illustrated.


http://psyberspace.com.au/lithium.html


Cheers

Is there any dates etc as to when this conversion was done and does anyone have a contact to these people? It will be very interesting to see how his battery set up servives, he did a few things I would do differently so it would be interesting to see how well his set up goes. To me, the charge voltage is too high, I would have combined the cells into one pack rather than 2 seperate 12v battery packs and there is no individual cell monitoring but rather combined cell voltages so an assumption is made that all the cells will stay together and an average voltage will do.
None of it is hard or expensive to change, simply using the Gel setting would have been a better opion for charging, connecting the cells in series/parallel as in his second option would have avoided one battery doing all the work and a $28 Junsi cell logger would have monitored individual cell voltages setting off an alarm if a cell went over voltage or under voltage.

T1 Terry

[T1 Terry]

Originally Posted by Lagoon4us

With 42,000+ lookers at this thread there is a lot of interest over a long time...

The link you posted brings it down to brass tacks, the guy has used a low voltage cutout and carefully checked his upper charge voltages to be certain all is within acceptable limits.

He also says that with small installations like these there's no real need to have a sophisticated BMS.

A couple of other questions that would help me to learn the basics are :-
1) Do we need to isolate other batteries from the Lithium bank eg lead acid start batteries, thruster batteries and such.
2) Will Yanmar/Volvo standard alternators with their standard built in regulators suffice?
3) With the setup this guy used will he have to do cell balance checks at some time interval?

Great article good info within...... Cheers Frank

1) Do we need to isolate other batteries from the Lithium bank eg lead acid start batteries, thruster batteries and such.
The reason you need to isolate lead acid batteries from lithium ferrous batteries is to stop the lead acid parriste draining the lithium ones. The rested voltage of a lead acid battery is below 12.8v, a lithium battery is greater than 70% discharged before the combined cell voltage drops below 12.8v so the lithium battery would always be trying to charge the lead acid bttery and the lead acid battery would continue to waste the over charge as heat.
2) Will Yanmar/Volvo standard alternators with their standard built in regulators suffice?
If the upper voltage limit is less than 14v they will be fine but if not you will need a method of cutting the link between the lithium batteries and the lead acid batteries if a house battery cell goes over 3.6v
3) With the setup this guy used will he have to do cell balance checks at some time interval?
A simple $28 Junsi cell logger will tell you when you need to do a cell balance, if a cell goes over 3.6v and sets an alarm off while the other cells are still below 3.45v then that cell needs a bit used out of it to reduce it's sate of charge a bit. Otherwise you really don't need to do anything.

I would like all charging systems via the lead acid batteries to the house batteries, that way a simple solenoid can stop the house battery charging and the lead acid batteries will save any back voltage destroying sensetive electronics

T1 Terry

[downunder]

Originally Posted by T1 Terry

Is there any dates etc as to when this conversion was done and does anyone have a contact to these people? It will be very interesting to see how his battery set up servives, he did a few things I would do differently so it would be interesting to see how well his set up goes. To me, the charge voltage is too high, I would have combined the cells into one pack rather than 2 seperate 12v battery packs and there is no individual cell monitoring but rather combined cell voltages so an assumption is made that all the cells will stay together and an average voltage will do.
None of it is hard or expensive to change, simply using the Gel setting would have been a better opion for charging, connecting the cells in series/parallel as in his second option would have avoided one battery doing all the work and a $28 Junsi cell logger would have monitored individual cell voltages setting off an alarm if a cell went over voltage or under voltage.

T1 Terry

here is a link to his website. David Straton. Perhaps could contact him through his blog

Nimrod catamaran: Lithium batteries

[T1 Terry]

Thanks Downunder,
Do you know if David is a member here?

T1 Terry

[Lagoon4us]

TERRY.
"A simple $28 Junsi cell logger will tell you when you need to do a cell balance, if a cell goes over 3.6v and sets an alarm off while the other cells are still below 3.45v then that cell needs a bit used out of it to reduce it's sate of charge a bit. Otherwise you really don't need to do anything." OK makes sense..Do these connect to each cell via a sensor wire or just overall?


"I would like all charging systems via the lead acid batteries to the house batteries, that way a simple solenoid can stop the house battery charging and the lead acid batteries will save any back voltage destroying sensetive electronics" Sorry i'm not quite understanding this bit, are you meaning a solenoid should connect the banks when charging then drop out when not so voltage doesn't bleed from Lithium to Acid banks?

I can get these locally WB-LYP400AHA LiFeYPO4 (3.2V/400Ah) and would get 8 of them connecting to give a single unit at 12volt/800 amps for around $4000 AUD Delivered to Croatia, then as per 'Downunders link' i would fit the under voltage unit plus the 'Junsi' logger.

From what i understand i should fit these into a tightish metal box to prevent expansion etc.

Then recognising and isolating circuits will be the important one, one of the things that i found on the Thruster circuit is there is a charge wire running through the port engine start battery so that the Thruster battery in the bow gets some charge, HOWEVER that battery died and the thruster motor took feed from the starter battery and obliterated the 120amp fuse.

Ok the understanding is growing the more that i read i'm looking at wintering here in Croatia instead of Greece/Turkey now as our Aussie registration won't be completed in time so i'll be doing this project with gloves on brrrrrrr!!!!

Cheers Frank