DC/DC or ArgoFet

[Britishsea]

Originally Posted by CaptainRivet

Be careful LTO has a low resistance like lithium so you loose your high resistant protection in your LI system if via an argofet.

Hi Captain, thanks for your always helpful comments.

I did not understand your last point here.

I had assumed that a LTO starter battery pack would, like an AGM battery, act as a "load-dump" for an alternator in the event of a LFP house bank's high voltage cut-off. Are you suggesting that a LTO starter bank's low internal resistance would not absorb the alternator's voltage spike? Or are you making a completely different point ?

BritSea

[CaptainRivet]

Originally Posted by Britishsea

Hi Captain, thanks for your always helpful comments.

I did not understand your last point here.

I had assumed that a LTO starter battery pack would, like an AGM battery, act as a "load-dump" for an alternator in the event of a LFP house bank's high voltage cut-off. Are you suggesting that a LTO starter bank's low internal resistance would not absorb the alternator's voltage spike? Or are you making a completely different point ?

BritSea

Correct, LTO cannot absorb a voltage spike and cannot act as a load dump as it’s internal resistance is even lower then LifePo4.
I remember that you have a balmar with external regulator, in this case you don‘t need a load dump.the bms just cuts the field wire when full or in an HVC event and no spike at all.
But LTO is the most reliable starter and emergency backup battery for your LifePo4 in case of disconnect you can get. Advantage to agm/FLA is You don‘t need a dc to dc charger, just put a battery selector switch in, flip it to LTO start completely independent from disconnected Lifepo4 and charge it directly of the balmar with LifePo4 setting, same with your solar array or every other charge source configured for LifePo4… it will be full in no time in case you drained it. After full or whenever you want/can flip back the switch to LifePo4. It accepts 10C=400A charge and discharge, works even at 8V and can be charged till -30 degrees Celsius and has no significant self discharge and can be recharged even it’s down to 0V. trickle charge is not really needed as no significant selfdischarge but if you want it use what you have…best is a small solar panel with short voltage below 17V. That simple combo most likely still works after a lighting strike
If still want a load dump,add/ use a cheap starter FLA for 60Euro which you can refill(!) as there is no such thing as a maintenance free FLA…I check fluid level and acid density and know it’s condition and can even extend its life… if closed you know nothing till it dies one day and because of Murphy exactly then when you need it

[Britishsea]

Originally Posted by CaptainRivet

Correct, LTO cannot absorb a voltage spike and cannot act as a load dump as it’s internal resistance is even lower then LifePo4.

OK, well very good point, I had assumed otherwise. Thank you for the waring!


I remember that you have a Balmar with external regulator, in this case you don‘t need a load dump.the bms just cuts the field wire when full or in an HVC event and no spike at all.

Good memory. Well, just to complicate my life, I have my Balmar's brown ignition wire on a relay controlled by an Electrodacus "Type 2" signal and something similar on my Solar Charge controller and on my shore-power charger (each max 3.51v any one cell). But as a second line of defence, I also have all these charge sources going to a Victron BatteryProtect relay (220 amp version), which is controlled by a "Type 5" (max 3.7V any one cell). So there is a chance that i have sudden shut down if the chargebus opens and therefore a load dump.


But LTO is the most reliable starter and emergency backup battery for your LifePo4 in case of disconnect you can get. Advantage to agm/FLA is You don‘t need a dc to dc charger, just put a battery selector switch in, flip it to LTO start completely independent from disconnected Lifepo4 and charge it directly of the balmar with LifePo4 setting, same with your solar array or every other charge source configured for LifePo4… it will be full in no time in case you drained it. After full or whenever you want/can flip back the switch to LifePo4. It accepts 10C=400A charge and discharge, works even at 8V and can be charged till -30 degrees Celsius and has no significant self discharge and can be recharged even it’s down to 0V. trickle charge is not really needed as no significant selfdischarge but if you want it use what you have…best is a small solar panel with short voltage below 17V. That simple combo most likely still works after a lighting strike
If still want a load dump,add/ use a cheap starter FLA for 60Euro which you can refill(!) as there is no such thing as a maintenance free FLA…I check fluid level and acid density and know it’s condition and can even extend its life… if closed you know nothing till it dies one day and because of Murphy exactly then when you need it

Thanks this above suggestion. Presumably, an other option is to remove the Argofet, and charge the LFP bank directly from the Alt. to the charge bus and the new LTO battery via a small (8amp, $100) DC-DC Victron Orion-TR (to 15 volts) and then add a Sterling Power Alternator Protect to suppress any potential voltage spike from a "type 5" charge bus disconnect event from the LFP bank. I think I would rather have all the process automated. Do you see a flaw in this design? Obviously a bit more money...

I have no experience with the Sterling Alt. Protect but Mainsail seems to endorse their effectiveness. My alternator is only 110 amp and i'm on Balmar's belt mode # 5, so heavily derated.

BritSea

[Afrinus]

Hi, funny that the original point of this post is long gone, but that the new direction now suits just fine.
As I need to in anyway buy a new start bank, I'm looking into LTO.
if I'm offered 45 Ah LTO cells as grade A, brand new, are you saying these are in fact lower grade 55Ah cells?
So, stay away?

[CaptainRivet]

Originally Posted by Britishsea

Thanks this above suggestion. Presumably, an other option is to remove the Argofet, and charge the LFP bank directly from the Alt. to the charge bus and the new LTO battery via a small (8amp, $100) DC-DC Victron Orion-TR (to 15 volts) and then add a Sterling Power Alternator Protect to suppress any potential voltage spike from a "type 5" charge bus disconnect event from the LFP bank. I think I would rather have all the process automated. Do you see a flaw in this design? Obviously a bit more money...

I have no experience with the Sterling Alt. Protect but Mainsail seems to endorse their effectiveness. My alternator is only 110 amp and i'm on Balmar's belt mode # 5, so heavily derated.

BritSea

You are welcome.

Double security on charge busbar, good intention but wrong execution, sorry like this you do more harm then good.
Additionally Victron battery protects are not really super reliable, they are cheap and good for switching high current loads off/on but Victron itself suggested not to use them as last line of defense for Li installs….know Dacian recommends them and I use one to for my „rest load main busbar“ but as first instance and if fails well I have no radio….

Suggest following:
First line of defense connecting that all to a type 2 is good, keep it.
2nd line of defense connect all from first line of defense to the type 5 too. You can get a type 5 without hitting type 2 criteria’s, Dacian explained it to me.
3rd line of defense Use Victron parameters so device shut itself off eg solar above 14,5V shut down, don’t know balmar but I assume you can define some shut down parameters in the regulator too. With this you have to experiment a bit and find the right values, just lower them step by step till the Victron shuts off before BMS does. If that happens go back to last set of parameters where it didn’t happen.
BMS is much better then a Victron Battery protect here and cutting all off with alternator running under full load I wouldn‘t be 100% sure that via argofet the whole spike is cut…and no damage to other stuff can happen. Chance is small but unnecessary here. So skip the battery protect here. That is the advantage of Electrodacus that you don‘t need these heavy duty relays here.

Doing it like this you don‘t need argofet and AGM as protection and charge directly from alternator, no Sterling protect needed too as field will be cut in a shut down. Charge LTO like you prefer, dc-to-dc from LifePo4 is ok.
But because it’s an emergency backup how do you charge if LifePo4 is shut down/dead? Yes it starts 40x your engine without recharge but at one point you need to charge it and how if LifePo4 is gone. You can put a battery switch to switch between them and charge directly from alternator plus have dc-to-dc for normal operation/emergency start because house bank is low.

[CaptainRivet]

Originally Posted by Afrinus

Hi, funny that the original point of this post is long gone, but that the new direction now suits just fine.
As I need to in anyway buy a new start bank, I'm looking into LTO.
if I'm offered 45 Ah LTO cells as grade A, brand new, are you saying these are in fact lower grade 55Ah cells?
So, stay away?

Yes 45AH can only be derated 55AH, avoid as worst combo.
10AH less on 55AH is already heavily used and degenerated…if new then serious production issues which is common with 55AH…and serious user issues afterwards too.

Look at the cell length, 30Ah and 40AH are 160mm without and 202mm with studs. That’s what you should get, most value for money are new grade b 40AH, they should garuntee 36-38AH per cell and that they are new.

Sometimes you get grade B 30AH for around 20Euro, get 12 and expect a 12V 45 AH LTO that will last another 10years minimum. Not a bad choice either….but only if cells are really cheap…even heavily used have still more life in them then a new LifePo4…..

For Europe: good source, not cheap but very good quality
https://www.lto-store.de/home/LTO-Zellen-Sets-c71346171
No relationship with them, just know a lot ordered there and were happy.
Their active balancer for LTO is great, highly recommended.
I order via my friends NPO but that’s not publicly available.

[Britishsea]

Thxs Captain for your always insightful comments.


l can't help but to feel we are really straying off the OP's topic here and this is becoming very specific to my particular system and BMS choice - so apologies to anyone else reading this. Suggest you ignore..

BritSea[/QUOTE]

Originally Posted by CaptainRivet

You are welcome.

Double security on charge busbar, good intention but wrong execution, sorry like this you do more harm then good. Agreed that it could be more trouble than benefit - but charge-bus disconnect seems to the accepted standard for those systems that are insured. I'm still considering this point.

Additionally Victron battery protects are not really super reliable, they are cheap and good for switching high current loads off/on but Victron itself suggested not to use them as last line of defense for Li installs….know Dacian recommends them and I use one to for my „rest load main busbar“ but as first instance and if fails well I have no radio…. Agreed a soild state relay is really not the best for this application the Victron is nothing special quality wise. I suppose however that those with drop-in batteries are doing just this (a charge disconnect with a FET). I purchased a Midnite Solar (Carling) 125amp, breaker with a shunt-trip intended to be used for my charge-bus disconnect (physical contact and requires a manual reset) but discovered that the shunt circuit does not disconnect from power after it tripped....so reverted to the Battery protect as a plan B.

Suggest following:
First line of defense connecting that all to a type 2 is good, keep it.
2nd line of defense connect all from first line of defense to the type 5 too. You can get a type 5 without hitting type 2 criteria’s, Dacian explained it to me. I see where you are going with this and it an interesting suggestion...I may do that.
3rd line of defense Use Victron parameters so device shut itself off eg solar above 14,5V shut down, don’t know balmar but I assume you can define some shut down parameters in the regulator too. With this you have to experiment a bit and find the right values, just lower them step by step till the Victron shuts off before BMS does. If that happens go back to last set of parameters where it didn’t happen. Well, this is really my 1st line of defense, as all my charge sources are, as you recommend, set below the pack voltage needed to trip the BMS (assuming cells are in balance). I will turn up the SCC periodically while on the boat (at anchorage) to get the BMS's SOC meter to reset to 100%.
BMS is much better then a Victron Battery protect here and cutting all off with alternator running under full load I wouldn‘t be 100% sure that via argofet the whole spike is cut…and no damage to other stuff can happen. Only thing up stream of the Argofet is the Alt, the start battery and the starter. But I could see a voltage spike fry a Argofet. Presumably, it would fail closed? I wonder if anyone has had experience with this? Chance is small but unnecessary here. So skip the battery protect here. That is the advantage of Electrodacus that you don‘t need these heavy duty relays here. Your point is well taken here, and it would simplify things

Doing it like this you don‘t need argofet and AGM as protection and charge directly from alternator, no Sterling protect needed too as field will be cut in a shut down. Charge LTO like you prefer, dc-to-dc from LifePo4 is ok.
But because it’s an emergency backup how do you charge if LifePo4 is shut down/dead? Yes it starts 40x your engine without recharge but at one point you need to charge it and how if LifePo4 is gone. You can put a battery switch to switch between them and charge directly from alternator plus have dc-to-dc for normal operation/emergency start because house bank is low.Yes I do have an emergency parallel switch, for the AGM start battery to take over from the LFP bank if required.

.

[Baronkrak]

Originally Posted by Afrinus

stacking two DC/DC converters (30A each)

A 12/24V battery management system. Do not requires DC/DC converters.

[CaptainRivet]

Originally Posted by Baronkrak

A 12/24V battery management system. Do not requires DC/DC converters.

He is parallelling them to charge with 60A from alternator via FLA or AGM ro limit current from a standard alternaror, nothing to do with conversion

[Baronkrak]

Originally Posted by Afrinus

Or something entirely different?

It remains that a 12/24V system is the way to go.

Search Internet: 12/24V battery management system. cruisersforum

Originally Posted by CaptainRivet

...
6 glow plugs are 600A ...

By the way VA = Power, is the preferable unit to use.

100A per glow plug, are you sure? At 11V that 1100VA

Normally glow plug resistance is between 1 to 6 Ohms

Originally Posted by Statistical

Exactly. I don't think some people realize just how little energy is used to start a motor. …

They do. They also realize that the capacity of the battery need to be sufficient to allow multiple cranking if the engine fail to start or if they wish to bring the oil pressure up before running the engine.

[CaptainRivet]

Originally Posted by Baronkrak

It remains that a 12/24V system is the way to go.

Search Internet: 12/24V battery management system. cruisersforum




By the way VA = Power, is the preferable unit to use.

100A per glow plug, are you sure? At 11V that 1100VA

Normally glow plug resistance is between 1 to 6 Ohms



They do. They also realize that the capacity of the battery need to be sufficient to allow multiple cranking if the engine fail to start or if they wish to bring the oil pressure up before running the engine.

12/24 system very complex, I stay with 12V and very short Thick cables for high current loads close to the battery.

Not sure, don‘t have a common rail on my cat nor experience with them on a boat. Just know cars and there the glow plugs can need 100A or even more.

Smart People realize about the usable capacity in combination with max amps.
A 40AH LTO easily starts a 50hp diesel 100 times and even if down to 9V it cranks it over which no lead manages. You would need a 300AH lead starter to be able to do the same…just what gets lost on a lead when it’s voltages dives down after the first millisecond of high loads due to the peukert effect is massive.