Technical LifePo4 Charging

[tommin]

I have checked so many articles regarding charging LifePo batteries, each with different views, so hopefully someone can enlighten me here.

I have a Toptron C18 Electrical management system, old but does the job with the 2x 100amp wet batteries. Now I want to put in 2x100amp LifPo4 batteries and am confused by so many different views I have read.

My Toptron schematics read as such:
Output: 12v max 17amp
Characteristic curve I, U, U2 (17amp: 14.2v - 6 hours: 13.8v)

This part is from the manual:

After mains voltage is applied, charger checks whether the voltage of the leisure battery is greater than 2v. This is indicated by a brief flashing of the LED in red. If battery voltage is below 2v or if the leisure battery is not connected, the red LED flashes continuously. If the battery voltage is above 2v, the leisure battery is initially charged with a constant current. To prevent the transformer built into the charger from overheating when the battery voltage is very low, this constant current is lower for battery voltages below 8v than for battery voltages above 8v. If the battery voltage reaches a voltage of approx 13.8v, the current is reduced linearly down to a voltage of 14.2v.

During this charging phase, the two-color LED in the display panel lights up red. If a voltage of 14.2v is measured by the microcontroller built into the charger for a period of 2 seconds, the 6hrs during which the battery voltage is maintained at 14.2v have elapsed. This condition is indicated by a yellow LED. If the battery voltage does not fall below 12.5v within 6hrs due to switched on consumers that are fed from the battery, the trickle charge is switched on. This means that the battery voltage is maintained at a value of 13.8v. This condition is indicated by a green LED on the display and lasts for 2hrs. After two hours of trickle charging of the leisure battery, the engine battery is charged to a voltage of 14.2v. After the engine battery has been charged, the system switches back to trickle charging of the leisure battery. The trickle charge of the leisure battery continues until the battery voltage has either fallen to 12.5 volts or the charger's mains connection is interrupted and switched back on. If the voltage of the engine battery on the charger is below 2v, the charging LED flashes green when the engine battery is to be charged.

Is this Toptron good enough for the LifePo batteries or do I need to supplement with a lithium charger and if so how to go about disconnecting the Toptron charger?

Regards
Tom

 

[deejays]

I have checked so many articles regarding charging LifePo batteries, each with different views, so hopefully someone can enlighten me here.

I have a Toptron C18 Electrical management system, old but does the job with the 2x 100amp wet batteries. Now I want to put in 2x100amp LifPo4 batteries and am confused by so many different views I have read.

My Toptron schematics read as such:
Output: 12v max 17amp
Characteristic curve I, U, U2 (17amp: 14.2v - 6 hours: 13.8v)

This part is from the manual:

After mains voltage is applied, charger checks whether the voltage of the leisure battery is greater than 2v. This is indicated by a brief flashing of the LED in red. If battery voltage is below 2v or if the leisure battery is not connected, the red LED flashes continuously. If the battery voltage is above 2v, the leisure battery is initially charged with a constant current. To prevent the transformer built into the charger from overheating when the battery voltage is very low, this constant current is lower for battery voltages below 8v than for battery voltages above 8v. If the battery voltage reaches a voltage of approx 13.8v, the current is reduced linearly down to a voltage of 14.2v.

During this charging phase, the two-color LED in the display panel lights up red. If a voltage of 14.2v is measured by the microcontroller built into the charger for a period of 2 seconds, the 6hrs during which the battery voltage is maintained at 14.2v have elapsed. This condition is indicated by a yellow LED. If the battery voltage does not fall below 12.5v within 6hrs due to switched on consumers that are fed from the battery, the trickle charge is switched on. This means that the battery voltage is maintained at a value of 13.8v. This condition is indicated by a green LED on the display and lasts for 2hrs. After two hours of trickle charging of the leisure battery, the engine battery is charged to a voltage of 14.2v. After the engine battery has been charged, the system switches back to trickle charging of the leisure battery. The trickle charge of the leisure battery continues until the battery voltage has either fallen to 12.5 volts or the charger's mains connection is interrupted and switched back on. If the voltage of the engine battery on the charger is below 2v, the charging LED flashes green when the engine battery is to be charged.

Is this Toptron good enough for the LifePo batteries or do I need to supplement with a lithium charger and if so how to go about disconnecting the Toptron charger?

Regards
Tom

Hi @tommin , I suggest you go take a look at Victron's website as they have a wealth of information there. But to condense the info, LiFePo4 batteries are best charged with a constant current with a bulk charge voltage of 14.2V, and when the charge current drops to approx. 4% of total capacity in AH, which is known as "tail current" then the charger should drop from 14.2V down to the "float" voltage of 13.5V. Your existing charger has enough current to charge with, but it seems it floats at 13.8V which is fine for lead acid, but not great for LiFePo4. It may work sort of "OK" but if you are spending money on LiFePo4 I would also replace the charger with something from Victron's range and also install a Victron Smart Shunt. I run Victron gear and it works well - and I think good value for money. For a 200AH, I would get the 30A charger. Hope this helps. The description of your existing charger is extremely vague, and it may shorten the life of LiFePo4 batteries. The Victron units are fully adjustable, and the beauty is you can install a Victron app on your phone to monitor the system - particularly if you install the Smart Shunt.

 

[monty200]

Another shout for Victron gear.I build campers and always try and use it as it just works.

 

[theoneandonly]

There is an alternative to Victron products at the high end ie Votronics Deigned and made in Germany. They are also typically more compact than Victron and more reactive to problems than Victron (Motorhomes a much smaller part of victron busieness. I also use a Victron Product the BMV712 simular to the smart shunt in that it can measure SOC and other attributes but imp[ortantly it has a relay that can be switched by SOC or voltage values. I use it to drive SSRs to control charging based on SOC.

 

[Googlebot]

In answer to your original question, yes it will work.

It will probably be bad for your battery long term. However it depends on how you use it, we are hardly ever on mains and rely on a B2B charger and solar, both Victron.

In that case I have chosen to keep the mains charger I have and when the batteries are full, I just turn it off as I put a switch on the supply to it. This means it isn’t automatic as such but does the job of charging the lithium batteries. When required I turn the charger on manually. This was a much cheaper and easier option for me.

If you want something that is fit and forget, then I would change the charger.

The method above also relies on you having an accurate way to see how much charge you have left. The Victron smart shunt is an excellent and accurate bit of kit and isn’t all that expensive.

 

[tommin]

Some good response and advice thanks, I did forget to mention the system also has 160w solar (looking to update to 400w this summer) with MPPT controller connected direct to batteries, how would this fair? I really don't want to start pulling out the old system if I don't need to.

 

[Googlebot]

That will be fine if it’s within the capacity for the controller.

What model and size is the controller for the solar?

 

[deejays]

Some good response and advice thanks, I did forget to mention the system also has 160w solar (looking to update to 400w this summer) with MPPT controller connected direct to batteries, how would this fair? I really don't want to start pulling out the old system if I don't need to.

So long as the MPPT solar controller has a LiFePo4 charging profile and wattage rating for your planned increase.

 

[tommin]

I have a 20 amp mppt but found out it is not suitable for lithium batteries, so just ordered a new 60 amp that does support. I think I will run with this and the Toptron for time being. Thanks to those inputs much appreciated.

 

[Communicator]

@tommin ,
One of the advantages of LiFePo4 batteries is that they can absorb substantial charging currents for extended periods of time, thus allowing faster recharging than lead acid batteries of a similar capacity. Another advantage is that they can withstand a much greater depth of discharge than equivalent lead acid batteries. Your proposed batteries will probably be able to draw large currents typically C/2 (50A each) for over 2 hours, if deeply discharged. The original specificationfor the alternator on your 2.8idTD, is only 80A maximum. I doubt that it would withstand such a current for long periods. The standard answer is to install a B2B with lithium profile to limit the current, and protect the alternator.

I may have missed it, but I cannot see any mention of a B2B in previous posts.

 

[the green vanper]

For best charging conditions check the instructions provided by the LiFePo4 battery supplier / manufacturer. Depends on what BMS have been installed inside.

Victron quality apparently dropped a few years back as they moved the production to Asia. I was considering their products but saw the reviews on Amazon and decided it's no longer worth paying so much more for their products.

I have a 230V charger supplied with my 2x200 Ah LTO batteries. It will be used when hooked up, but as I have an Epever MPPT 100A controller and 1,4 kW solars on the roof, the charger will be there just in case.

I'm still thinking how to organize charging from the alternator, but it shouldn't be hard, as I have 150A BMSes

 

[tommin]

Just a picture of my Toptron BMS info, I am guessing this BMS may not be up to the job? It is all confusing? What size b2b and where to fit it? between battery and BMS or BMS and alternator? If all else fails which BMS would suit my oldie? We live near artic circle, and our solar is sidelined for several months and our utilities use either mains if on site but normal batts otherwise hence changing to lithium.

 

[the green vanper]

Just a picture of my Toptron BMS info, I am guessing this BMS may not be up to the job? It is all confusing? What size b2b and where to fit it? between battery and BMS or BMS and alternator? If all else fails which BMS would suit my oldie? We live near artic circle, and our solar is sidelined for several months and our utilities use either mains if on site but normal batts otherwise hence changing to lithium.

This is the charger, not the BMS (Battery Management System).

The BMS is INSIDE each of the Lithium (generally lithium!) battery housing. The battery terminals are connected to it, not directly to the cells. It manages charging / discharging the cells in a similar way, health etc. So you can't modify the connection. Anything (solar MPPT, AC charger, alternator) you connect to the Lithium battery terminals will go through the BMS.

As for the choice of LiFePo4, having in mind you said you live near the Arctic circle, it's a wrong choice as far as I know.

Li-Ion cannot be discharged nor charged in below zero centrigrade.
LiFePO4 can be discharged but cannot be charged in below zero centigrade.
There's a variant (but can't remember the name, it has an additive/modification like LiFeS04?, or LiFeMn04? I was doing my research a couple of years back, sorry), which can be discharged and charged in below zero centigrade.
LTO is best here, apparently they are used in Antarctica. I've read somewhere that depending on the config they can be used between -100 and +100 degrees. Mine can be used (discharged and charged) since -40 However they have other parameters that make them different (like nominal voltage, energy density).

You NEED to talk to a specialist in arctic camping/caravaning BEFORE you place the order.

Double check the manufacturer's specifications, as there might be variants of the same type (like for the LTO). Don't trust marketing slogans, ask for certificates, declarations, tests results, documents. Those batteries are not cheap, it would not be good to kill them in a year!

Then, you have to understand how the system works. If you plan to have 2 separate lithium batteries you need to assure the exact same length of cables to each of them. Unless you will have an external system to switch between the batteries during charging / discharging. There might be some arduino controlled solutions. From this point of view it is much better to buy one bigger battery, as the internal BMS system will manage all of it for you.

 

[tommin]

Sorry I have been reading so many BMS articles it got stuck somewhere in my degenerated brain cells I was referring to the electrical management system or as you pointed out "the charging system". I understand the climate issue and have sorted that with a purposed made warm storage setup which should suffice (I think).You have given me something to thinks about for sure.

 

[tommin]

Okay just to give an update to this post.
I went and installed 2x100amp lifePo batts, upgraded the solar panel to 430W with a 60amp controller, did a weekend away off grid, weather balmy, we are still minus 5C weather with snow still on the ground. Run the usual items, coffee and toaster machines, alde heater and fridge on constant (gas I know). Anyhow the batts never even blinked, 100% real chuffed with them. Will update further after our annual trip around Norway, that should give us a better idea on performance.

 

[tommin]

Back from a 8 day off grid trip to Norway and survived All I can report is: they worked very well, no problem with charging from alternator or solar, saying that we spent a full 4 days static, no charging except solar one or two days were partly cloudy but our 435 watt panel did well, kept the batts at 100% for most days, only last day did they drop and only to 50% and voltage down to 11.5v whilst making coffee ( we coffeed a lot ) Note: inverter was a 1000w sine wave. So anyway we were happy with them.
On way home we stopped at a camper shop and decided to change our integrated camper to camper van (Adria 640 SL) now I have to start all over again on deciding if we go lithium or not

 

[deejays]

Back from a 8 day off grid trip to Norway and survived All I can report is: they worked very well, no problem with charging from alternator or solar, saying that we spent a full 4 days static, no charging except solar one or two days were partly cloudy but our 435 watt panel did well, kept the batts at 100% for most days, only last day did they drop and only to 50% and voltage down to 11.5v whilst making coffee ( we coffeed a lot ) Note: inverter was a 1000w sine wave. So anyway we were happy with them.
On way home we stopped at a camper shop and decided to change our integrated camper to camper van (Adria 640 SL) now I have to start all over again on deciding if we go lithium or not

Good to hear it all went well! And congratulations on the new Adria - you will love it (I have an Adria 600SPB. And of course, you WILL go lithium! Cheers.