Solar controller for LifePo4 batteries

[Typhoon]

Hi all

I have had my LifePo4 (600 amp hrs Sinopoly) batteries for a few years now and love them . I only charge them with my purposely built generator but am thinking of mounting a 140 watt solar panel on my new hard Bimini .

I have done a little looking around for solar controllers but I am totally out of my element and would like to know what people are using . I would like to have it set very low and not float the batteries , just give them some help when I am away from the boat for a week or more to keep the fridges going and hold the batteries at a midpoint level of around 13.2 volts . Im not hoping to charge the batteries fully with solar, I will use my genset for that.

Regards John.

[SnakeEyes]

Check out Mastervolt Charge Regulator

[44'cruisingcat]

I have an Outback power systems Flexmax which is completely programmable, but would be huge overkill and expense for a 140 watt system.

[john61ct]

The problem is IF the incoming is greater than outgo, you really want to just Stop charging rather than going to a low float.

No BMS? Shunt-based battery monitor with "alarm relay" option?

As for a good value controller. Victron's 75/15 MPPT will give you room for expansion often as low as $100.

A great BM is Bogart's Trimetric, not sure about its readiness for a marine environment though. It can be used to control their SC-2030, yes PWM but IMO a great option.

[SV THIRD DAY]

Hey John as long as the solar controller will let you adjust the voltage of bulk absorption and float it should work fine for you. I usually set my solar controller to 13.4 up to 13.6 depending on what's going on. Here's a link to a video I made of my solar controller on Facebook.


https://m.facebook.com/groups/191122128313?view=permalink&id=10154590539298314

[44'cruisingcat]

Originally Posted by john61ct

The problem is IF the incoming is greater than outgo, you really want to just Stop charging rather than going to a low float.

A low float WILL stop charging.

[44'cruisingcat]

Originally Posted by john61ct

The problem is IF the incoming is greater than outgo, you really want to just Stop charging rather than going to a low float.

A low (enough) float WILL stop charging.

[sea-bee]

Originally Posted by john61ct

...As for a good value controller. Victron's 75/15 MPPT will give you room for expansion often as low as $100...

These are also totally programmable (you need to buy the USB cable for it, software free download from Victron) and have the ability to turn your anchor light on/off automatically.

Chris

[Typhoon]

Thanks guys,

Thats an interesting controller Rich , way more then I need . How many watts is your array ?

All I was only seeing the preset units . I will look for a fully programmable unit.

Im not needing a lot of output , if I get 30 amp hrs a day I will be happy . My fridges use very little power.

I am using a BMS but only a LVC , I am always present when charging . I will add the HVC just for the piece of mind when charging from solar.

Found this little video as well .

https://www.youtube.com/watch?v=7YEq6iOmjPk

Any one use one of these PV controllers? Seems to have all the adjustments . Or is the Victron a better bet , I have not had good experiences with Victron equipment.

Again thanks for all the help guys .

Regards John

[john61ct]

Victron is very widely used and respected all around the world. The ONLY product of theirs ANY I've heard negatives about (out of hundreds) was a low-end VSR.

There are thousands of cheap cr^p from China controllers out there, beware.

Most controllers nearly as good as that low-end Victron are a lot pricier.

[SV THIRD DAY]

I have a BlueSky 3000 on another string of solar and it also has an adjustable outlet voltage. It's a less expensive and lower Amp unit. Despite some of the chatroom sages over on the LiFePO4 thread saying it won't work, as long as you set your solar controller (or battery charger for that matter) at a lower voltage then once your batteries hit that voltage then there is no more driving force and they stop charging. The perfect example has been my last week in the boat yard. I'm plugged into shore power with my 130A battery charger and have set the Bulk and Float to 13.3v. At his voltage my 400AH LiFePO4 battery bank is sitting at -82AH (80% SOC) with no net charge gain or loss. Sometimes I scratch my head at just how easy these LiFePO4 batteries are in comparison to how difficult people want to make them.

[Typhoon]

True true , Rich , they are super simple , just treat them like a light switch , on and off , stay out of the knees and you are good to go.

Looking at this Prostar https://www.morningstarcorp.com/products/prostar-mppt/ Looks like good quality and has all the adjustments on board.

Now to choose a good panel , a little flexibility would be good in the 140 watt range.

Regards John

[SV THIRD DAY]

I just put two of these 140W panels on my daughters boat

https://www.solar-electric.com/solar...ar-module.html

It's her live aboard college dorm and while on the mooring ball gives her all the power she could ever use...hair drier and curling iron an all...ha ha ah

[Colin A]

Originally Posted by SV THIRD DAY

I have a BlueSky 3000 on another string of solar and it also has an adjustable outlet voltage. It's a less expensive and lower Amp unit. Despite some of the chatroom sages over on the LiFePO4 thread saying it won't work, as long as you set your solar controller (or battery charger for that matter) at a lower voltage then once your batteries hit that voltage then there is no more driving force and they stop charging. The perfect example has been my last week in the boat yard. I'm plugged into shore power with my 130A battery charger and have set the Bulk and Float to 13.3v. At his voltage my 400AH LiFePO4 battery bank is sitting at -82AH (80% SOC) with no net charge gain or loss. Sometimes I scratch my head at just how easy these LiFePO4 batteries are in comparison to how difficult people want to make them.

This does seem to work in practice. I have asked a few people in the electric propulsion biz about this and they seemed concerned that solar floating could be an issue. Basically they said longterm float with no discharge may cause capacity loss in the cells or loss of cycles. It's hard to find any data about that thou. Honestly I come across this disagreement so much that I may buy a cell and see what happens if you have no load connected and float it for a few weeks at 13.3 or so.

[SV THIRD DAY]

Originally Posted by Colin A

This does seem to work in practice. I have asked a few people in the electric propulsion biz about this and they seemed concerned that solar floating could be an issue. Basically they said longterm float with no discharge may cause capacity loss in the cells or loss of cycles. It's hard to find any data about that thou. Honestly I come across this disagreement so much that I may buy a cell and see what happens if you have no load connected and float it for a few weeks at 13.3 or so.

Some of the problem is in terminology...we should not use the terms Bulk, Absorption and Float when it comes to LiFePO4 batteries...the only reason we do is because that is the settings and lingo of the charge devices. But in reality you set them all at the same voltages, in my case here 13.3v. So don't think of it as "floating" your LiFePO4 battery. Using the term Float around LiFePO4 causes a kneejerk reaction and the lectures start on how to properly charge a LiFePO4 bank. This of it as charging when the battery falls below 13.3v and then stopping the charge once the voltage hit 13.3v. That's what I see from my charge sources...they are either charging when the voltage drops below the set-point of off when at the set point.

I'm 3 YEARS on my current 400AH bank doing this and my last capacity check and top end balance done a few months ago showed no measurable loss in capacity. That's real life data from a full time liveaboard set-up. Could I be crazy and my system a fluke? Sure...it's the internet and you see wild and crazy stuff and Fake News almost daily. All I can do it post what I know and have seen first hand.