Going solar

[stevemc181]

Can you point me to where Redarc spell out what their charging profile actually is please?

Not sure what info you are after regarding the profile, but the info I wanted is in the manual here: The LifePo4's get a max 14.6v and no float voltage https://www.redarc.com.au/Content/Im...n%20Manual.pdf

The issue with most of the DC-DC chargers on the market that are not LifePo4 specific is that they simply cant handle the constant current demand when charging and will overheat and shut down or fail. LifePo4 will pull every amp you can throw at it out of the charger, some simply can't keep up with the demand. I know the Redarc I am using gets bloody hot when I work it hard, so I am surpised it's still going. There are a few LifePo4 DC-DC chargers beginning to appear now, Sterling BB1260, Enerdrive DC2DC, GSL Electronics, Redarc, these are all pretty similar in that none of them have individual cell management capability. I use a BMS from EV Power in conjunction with individual cell balancing modules as in the picture of my battery below. My HV/LV will shut off supply at 14.7v and LV at 11.6v (User settable) This is really only a back up in case the BMS fails to do it's job.

[Cuppa]

Not sure what info you are after regarding the profile, but the info I wanted is in the manual here: The LifePo4's get a max 14.6v and no float voltage https://www.redarc.com.au/Content/Im...n%20Manual.pdf

Thanks. I guess I have to eat my words. In that link Redarc are more specific in that they state a BMS is required.

“CAUTION When using the Battery Charger to charge a Lithium Iron Phosphate battery, only batteries that feature an inbuilt battery management system featuring inbuilt under and over voltage protection and cell balancing are suitable”.

I had thought that when they referred to the ‘battery set point’ to change to constant voltage that they were referring to some sort of crude on/off BMS based only on the average voltage across the cells. I guess I was wrong. Nevertheless I still cannot find what it needs to ‘see’ in order to change to constant voltage (i.e. how it determines the LiFePo4’s are ‘full’ (or ‘full enough’). I obviously don’t understand how the Battery Management System works in conjunction with the charger if that set point is not user adjustable as I was of the impression that the BMS controlled the switching on & off of the constant current? Can you enlighten me?

[stevemc181]

Thanks. I guess I have to eat my words. In that link Redarc are more specific in that they state a BMS is required.

“CAUTION When using the Battery Charger to charge a Lithium Iron Phosphate battery, only batteries that feature an inbuilt battery management system featuring inbuilt under and over voltage protection and cell balancing are suitable”.

I had thought that when they referred to the ‘battery set point’ to change to constant voltage that they were referring to some sort of crude on/off BMS based only on the average voltage across the cells. I guess I was wrong. Nevertheless I still cannot find what it needs to ‘see’ in order to change to constant voltage (i.e. how it determines the LiFePo4’s are ‘full’ (or ‘full enough’). I obviously don’t understand how the Battery Management System works in conjunction with the charger if that set point is not user adjustable as I was of the impression that the BMS controlled the switching on & off of the constant current? Can you enlighten me?

Sorry, I'm not fully up to speed on it myself, but remember reading somewhere that the setpoint is the nominal voltage, which is usually around 13.2v or 13.3v with LifePo4. The charger then reverts to constant voltage and slowly raises it to the chargers max voltage setting (14.6v in this case) My BMS basically monitors individual cells and will bleed off from one cell to another if required or shut off a cell that is getting over charged etc. It does nothing regarding CC/CV switching of the charger as far as I am aware. The manual for my BMS (BCUPPAK) can be found here: https://ev-power.com.au/IMG/pdf/BCU-PPAK-4C-manual.pdf This may have some info of interest?

[Covo71]

Thanks Steve, for an extra $70 just taking away the extra wiring is worth it. Champion.
That is definitely the way to go. I think for what I want the 25a will do the trick. I think going the 40a version is going to be overkill for me.

[Covo71]

Hi TD,
I am going to mount the Arkpak in the car for now and later on put second battery in the back so I can take the Arkpak out and use for lighting etc. I was taking the fridge out of the car when we went camping but getting to old and fat for that.

[Covo71]

I was just going to get a foldout panel and only use when we go camping but now thinking of mounting on the roof. Would it need to be angled up or sit flat on the racks? Just a bit worried of damage if angled up.
I was thinking of it sitting flat for day to day driving but hinging it so I could prop it up when camping.

[Covo71]

It is lucky I am bald Cuppa as you would not have seen my hair move when that went way over my head. lol

[GQtdauto]

I was just going to get a foldout panel and only use when we go camping but now thinking of mounting on the roof. Would it need to be angled up or sit flat on the racks? Just a bit worried of damage if angled up.
I was thinking of it sitting flat for day to day driving but hinging it so I could prop it up when camping.

Flat is ok , had no problem on the caravan but did have 600 watt , the one on the front of my GQ is angled and has been on for about a year without damage from stones etc , I want a panel that's the width of the roof rack and about 300-400 mm wide .
I would put this on the same angle but make up a mounting bracket that flips back if I hit a tree branch.

[stevemc181]

Thanks Steve, for an extra $70 just taking away the extra wiring is worth it. Champion.
That is definitely the way to go. I think for what I want the 25a will do the trick. I think going the 40a version is going to be overkill for me.

No Worries, I like the idea of not requiring the changeover relay. I have fairly short runs to work each day, so can't leave the fridge on 24/7 as the battery doesn't get enough charge. I think I'll also end up with a roofrack mounted solar panel so it can charge up while I'm parked in the open.

[Hodge]

Yeah I'm very interested in this new unit without the relay. The relay adds a whole lot of new spaghetti wiring which isn't hard but so hard to keep neat and hidden...Might have a look and invest.

Sent from Note 4