Protect alternator in Lithium/FLA system

[Newcruiser311]

So I have decided to replace my FLA house bank with 2 Battle Born lithium batteries. The charging profile for the lithium is the same as my Charles charger profile for FLA so I am planning to leave the two starting batteries as FLA as they are relatively new. So for shore power charging I am ok. My issue is with alternator charging. Currently the 2 alternators feed into two inputs on a Guest battery isolator. Then there are three outputs that go to the house and two starter batteries. My concern is that with the charge acceptance of the Lithium bank, the alternator would overheat charging that bank to full. I was wondering of anyone had some good solutions to limit the charge going to that bank so the alternators do not over heat. The two alternators are 70amps each. Thanks!

[smac999]

if you have a lithium bank you should have an external regulator on your alts. voltage can be set, max output can be turned down, and the power can be shut off via your BMS to stop charging in case of an overvoltage issue. and they will have alt temp sensors.

you also need to get rid of that junk battery isolator.

[rgleason]

http://www.cruisersforum.com/forums/....php?p=2726542

This VSR Regulator has more control than a balmar 614 external.

[rgleason]

Also, if the bms can control a relay to disconnect the field wire before disconnecting the charge source on high voltage.when the batteries have been charged. That will help protect the alternator.

[Jon Hacking]

Originally Posted by Newcruiser311

So I have decided to replace my FLA house bank with 2 Battle Born lithium batteries. ... My issue is with alternator charging. Currently the 2 alternators feed into two inputs on a Guest battery isolator. Then there are three outputs that go to the house and two starter batteries. My concern is that with the charge acceptance of the Lithium bank, the alternator would overheat charging that bank to full. I was wondering of anyone had some good solutions to limit the charge going to that bank so the alternators do not over heat. The two alternators are 70amps each. Thanks!

New, welcome to Cruisers Forum!

As mentioned above, you *really* want external regulation for this (& with isolators you need external voltage sensing) & the best regulator we've found is the Very Smart Regulator by Al Thomason (the one RGleason mentioned - Al's contact info is down the page a bit, on the right). Not only does it have a special program for LiFePO4 batteries, it monitors alternator temperatures to keep them from overheating. It also has a switch to run the alternators at about 75% (which we use) just in case. All settings are customizable (although you shouldn't need that) & multiple regulators communicate over a CAN-Bus to keep them from arguing with each other. The best part is they're only $125, mainly because Al's a cruiser himself & likes giving back to the cruising community. Highly recommended (& no, I have no financial interest in these regulators)

[Newcruiser311]

Thanks all. So if I put a regulator in each alternator, should I still connect to some type of isolator to tie it all together? Currently the two feed Iin to it and that's also the point where the charger is connected. Do these regulators work with stock 70 amp alternators?

[john61ct]

Or get a Sterling BB DC-DC charger in between and leave the alt setup as is.

May be cheaper, and can easily move the bank + BB to another boat or vehicle.

[Newcruiser311]

John, I had considered that. Was trying to figure the best way to connect it. Come off one of the start batteries? Wouldnt the alternator still run just as long and hot?

[rgleason]

John did not mention his other favorite way, which I should have, of protecting the alternator diodes, connect it to a reserve battery and use the reserve battery as a place to dump the current when the BMS high voltage cutoff kicks in. I guess you would need a citrix relay or acr to connect the lifepo.

[rgleason]

I just remembered that Jon Hacking has a good website detailing his solar and lifepo installation. I will try to find it again.

[rgleason]

John61ct

Or get a Sterling BB DC-DC charger in between and leave the alt setup as is.

May be cheaper, and can easily move the bank + BB to another boat or vehicle
---------
This sounds like a good idea to me.

[folivier]

Since you're planning to buy Battleborn batteries why not call them and see if this, which they sell, will do what you want?https://battlebornbatteries.com/shop...ation-manager/

[rgleason]

What would be your favorite way of incorporating alternator charging of lifepo, with protection of the batteries and the alternator? Why?

[tanglewood]

Originally Posted by rgleason

What would be your favorite way of incorporating alternator charging of lifepo, with protection of the batteries and the alternator? Why?

I prefer:

1) set the charger to not over charge in the first place.

2) sense per cell voltage and if one gets too high, disconnect the power to the regulator, or disconnect the field wire, and raise an alarm. This is a graceful shutdown with no surges.

3) continue sensing per cell voltage and if one approaches a critical level, then disconnect the LFP. No alarm necessary. Darkness will be your clue.

These are progressive measures, successively invoked if previous measures fail to perform as they should. If you get to the point of disconnecting the LFP, a lot has gone wrong leading up to it. This is why I have a hard time getting too excited about alternator surge protection, mostly because two different attempts will have been made to shut it down gracefully. At this point, alternator surge is the least of your problem.

YMMV

[john61ct]

Originally Posted by rgleason

John did not mention his other favorite way, which I should have, of protecting the alternator diodes, connect it to a reserve battery and use the reserve battery as a place to dump the current when the BMS high voltage cutoff kicks in. I guess you would need a citrix relay or acr to connect the lifepo.

Please don't speak for me.

The protection being spoken of here is limiting LFP acceptance current to prevent alt overheating.

No BMS cutoff issues.

And best not to mention Citrix when speaking of VSR / ACR / combiners.

Relays are something different.