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

[CatNewBee]

Originally Posted by Recy

I got this in a news mail from GWL the other day.
What do think is it something useful or are there better options?

https://www.ev-power.eu/_d7077.html?...-20190926#tab1

A real bms perhaps..
Like REC ABMS or 123 SmartBMS or ESC BMS modules, or the BMS from EV Power, or the Lisunenergy BMS... There are plenty of options with not just protection logic, but also balancing built in.

[evm1024]

A new video from Victron of how to blow up your alternator when charging LiFePO4 batteries. Smoke included.

https://www.youtube.com/watch?v=jgoIocPgOug

[mikedefieslife]

My plan is to get the new DC DC charger from Victron. I've been following the thread about them on their forums. Two of them should work nicely for my setup.

[Maine Sail]

Originally Posted by evm1024

A new video from Victron of how to blow up your alternator when charging LiFePO4 batteries. Smoke included.

Always good to see others finally recognizing this, and the fact that low RPM charging can be the most damaging.. However an over-sized lead bank can result in similar outcomes...

[evm1024]

Originally Posted by Maine Sail

Always good to see others finally recognizing this, and the fact that low RPM charging can be the most damaging.. However an over-sized lead bank can result in similar outcomes...

I thought that you would like this video. It shows dramatically what you have been telling us for years.

[mikedefieslife]

Presumably no-one has ever run their cruising boat like this though.

I bet my old 675ah FLA could have easily killed the default 50a alternator, but it was run through a Sterling Alternator to Battery charger. It has multiple temp sensors and helps to get maximum output from the alt but reduces load when temps get high.

[john61ct]

Originally Posted by mikedefieslife

I bet my old 675ah FLA could have easily killed the default 50a alternator

Yes, that is the sort of extreme imbalance that could cause the same problem with lead.

Say 0.15C acceptance, that large a bank could try to pull 100 actual amps.

The **much** higher demand rate for lithium means even a 20Ah LFP pack could do the same, without any current limiting circuitry in between.

[CatNewBee]

Originally Posted by john61ct

Yes, that is the sort of extreme imbalance that could cause the same problem with lead.

Say 0.15C acceptance, that large a bank could try to pull 100 actual amps.

The **much** higher demand rate for lithium means even a 20Ah LFP pack could do the same, without any current limiting circuitry in between.

... Only if the cells are deep discharged.

LFP are usually above 13V, there is not enough voltage difference to push such high currents.

Try and measure the current.

[newhaul]

Here is a serious question how long can I expect to get a full 50 amps out of a shore power ( rated at 50 amps)charger charging a depleted 200 ah Lfp bank ( drawn down to 20% dod) needing 160ah to bring it back to full charge . Can one reasonably expect 3 hours at 50 amps output to battery?

[john61ct]

The acceptance rate curve as impacted by SoC (and voltage and resistance) climbing, does vary a fair bit by battery.

At C-rate starting below 0.3 I haven't seen much slowing down before 90% SoC, given direct input into bare cells.

Of course a BMS, whether protective, balancing-only, or both, may well have a limiting affect.

But the key factor is, does the charger actually put out that 50A current continuously? "Rated for" does not mean that. . .

Edit: ooh, hit #7000!

[senormechanico]

And 11,880 in 2 years and 9 months.

[newhaul]

Originally Posted by senormechanico

And 11,880 in 2 years and 9 months.

do you have any ideas about the 50 amp shore charger nobody seems to have any ideas yet .

[CatNewBee]

Originally Posted by newhaul

do you have any ideas about the 50 amp shore charger nobody seems to have any ideas yet .

Hi,
It depends on the charger.

What I can tell from Victron Quattro 12-5000/220 100/100 and two 40A legacy Crystec chargers installed is

The Quattro can nominal charge 220A, but rarely does. On shore power with a long lead to shore and then along the dock, it usually outputs about 180A constantly. It measures the voltage drop and reduces charge current accordingly.

On generator, it runs a few minutes about 210A and gets back to 190..205A when it gets warm, but stays there up to 95% SOC, then it reduces the output slowly but significantly down to 30A.

The Cristec chargers are configured to 14.4V, they do deliver around 30A to 40A each until the battery voltage goes over 13.6V, then they drop slowly to 20A because the voltage difference and voltage drop along the cabling seems not sufficient to drive the current.

On shore power I can reliably charge 240...250A to 95% SOC (3.6kW load at the dock line, around 16A at 220V)

[Dockhead]

Originally Posted by CatNewBee

Hi,
It depends on the charger.

What I can tell from Victron Quattro 12-5000/220 100/100 and two 40A legacy Crystec chargers installed is

The Quattro can nominal charge 220A, but rarely does. On shore power with a long lead to shore and then along the dock, it usually outputs about 180A constantly. It measures the voltage drop and reduces charge current accordingly.

On generator, it runs a few minutes about 210A and gets back to 190..205A when it gets warm, but stays there up to 95% SOC, then it reduces the output slowly but significantly down to 30A.

The Cristec chargers are configured to 14.4V, they do deliver around 30A to 40A each until the battery voltage goes over 13.6V, then they drop slowly to 20A because the voltage difference and voltage drop along the cabling seems not sufficient to drive the current.

On shore power I can reliably charge 240...250A to 95% SOC (3.6kW load at the dock line, around 16A at 220V)

Hmm, my Multiplus will put out its rated 70 amps (*24v) for as long as the bulk phase lasts and does not seem to be affected by shore power voltage drop within its specification. Naturally provided the shore power is capable of delivering the 2000 watts or whatever is required.


Why would your Quattro be any different? Maybe high ambient temperature? Mine is in an engine room but with blowers which I leave on when bulk charging so usually not more than 25C or max maybe 30C if the engine has been running recently.

[newhaul]

Originally Posted by Dockhead

Hmm, my Multiplus will put out its rated 70 amps (*24v) for as long as the bulk phase lasts and does not seem to be affected by shore power voltage drop within its specification. Naturally provided the shore power is capable of delivering the 2000 watts or whatever is required.


Why would your Quattro be any different? Maybe high ambient temperature? Mine is in an engine room but with blowers which I leave on when bulk charging so usually not more than 25C or max maybe 30C if the engine has been running recently.

sounds like I will be able to expect about 45 amps consistently then running my 1k genset for charging if it can handle the 50 amp charge consistently and sell off my 3.5k . Wish my little one was a 12v dc generator . As all it will be for is charging the bank.