Thread: WORLD'S BEST BATTERY CHARGERS

Thanks Tim,

the charger sounds like it is just what I need, but to be truthful, I'm not sure that I'll ever need to use and inverter to charge the batteries while driving along. We have 600 Watts of solar panel mounted on the roof on the van and it has to be a dark day in Hell before we fall into deficit when it comes to charging the batteries by solar.

I do, on the other hand, connect the van's batteries to the vehicle batteries when parked up overnight, mainly so that I don't flatten the cranking battery while still running the car fridge in the back of the car. My biggest problem is that sometimes I forget to isolate this connection when I take off the next day. This wasn't an issue when I had AGM batteries in the van, but could amount to a serious problem with the LiFePO4 batteries.

I have very heavy cable from the engine bay, right through to the van, so the volt drop is stuff all. This means that if the vehicle alternator raises the voltage to the level that the Lead/Calcium battery in my vehicle requires, I am going to kill the LiFePO4 batteries if I forget to isolate them before driving off.

So, my question to you is this, do you have a device that I can put in-line between the cranking battery of my vehicle and the van batteries that will automatically disconnect the van batteries if the voltage raises higher than 14.2 Volts? It would be even better if it automatically resets itself once the engine is turned off and the cranking battery settles.

Cheers

Russ

Hi again Russ and my new DT90 isolators come with over voltage protection and I can easily program one the DT90 isolators so that it has a lower over voltage shutdown.

Because of the way the DT90 works, it can be fitted anywhere in either your tow vehicle or in your caravan.

BTW thats a nice solar set up.

The 14.2v seems a bit low, can you post up the manufacturer’s specs for for your lithos?

Hi Tim,

the following paragraph was lifted straight from the supplier's "Lithium Care Guide"

In the case of LiFePO4 chemistry, the absolute maximum is 4.2V per cell, though it is recommended that you charge to 3.65V per cell. There is less than 1% extra capacity between 3.65V and 4.2V, and going above 3.65V may reduce the cell’s cycle life. Going above 4.2V may result in permanent damage to the cell.

So you can see that they recommend never exceeding 14.6 Volts for a nominal "12 Volt" battery. This is lower than the voltage of the regulator in my vehicle when at its peak. Further to that information I have been advised that once 14.2 Volts is achieved, only 1% - 2% more capacity can be gained by continuing to charge to 14.6 Volts. This seems to be borne out in the graphs that I have seen. In order to be doubly sure of achieving the longest life for my (very expensive) batteries I have taken this advice on-board and have set my solar regulator to boost until 14.2 Volts has been achieved, before going straight to float (as Absorption is not required with this battery technology.)

Limiting the maximum voltage (and hence charge current) in this manner will do absolutely no harm to the batteries and I can live with up to 5% less than peak charge as I have more than enough spare capacity for the load that I have in the van. When I get the time, I will do some real-world testing to see whether the quoted figures are actually correct, but for the moment I will defer to the supplier's wisdom.

Given that I have got about 0.1 Volts of volt drop at the end of the cables at the van battery, I guess a DT90 switch mounted under the hood (at the cranking battery) that drops out at 14.3 Volts would be quite acceptable.

Your product may be useful to me in another guise as well. As you will no doubt be aware, the terminal Voltage of LiFePO4 batteries stays pretty constant over most of its discharge range, but falls away dramatically at about 80% DOD. From the graphs that relate to the discharge rate that I would be experiencing in the real-world situation in my van, that Voltage would be pretty close to 12.7 Volts. I could then get you to program one of your DT 90 isolators to that set-point, thus ensuring that I never over-discharge my batteries. (See how anal I am?)

So, in summary, it sounds to me like the optimum setup would be one of your chargers (40 Amps sounds about right) and two DT90's. One set to 14.3 Volts and one set somewhat lower at 12.7 Volts.

Can you PM me a quote for the above please?

Cheers

Russ

Hi Russ and I thought the 14.2v was a bit low.

The manufacturer’s info about minimum voltage levels for their LiFePO4 batteries is about average.

The 3.65v minimum cell voltage to obtain a 99% charge state is per cell and there are 4 cells in a LiFePO4 “12v” battery.

So your minimum charge voltage is 14.6v but the maximum charge voltage of 16.8 actually seems some what high but manufacturer’s specs are the correct specs to work from.

Does each of your batteries have it’s own built in BMS, if so you need to find out the “SHUTDOWN” voltage level.

This is usually somewhere around 10.5v but I personally prefer not taking LiFePO4 batteries lower than 11.5v.

Next, you will probably find the constant discharge voltage of your LiFePO4 batteries is somewhere around the 13.1 to 13.3v, depending on load size and I would guess that 13.2v would be the working level for your batteries.

As such, leaving your LiFePO4 batteries connected to any lead acid batteries in your tow vehicle will simply waste LiFePO4 battery energy while keeping the lead acid battery(s) fully charged.

Russ, see if you can source the SHUTDOWN voltage for your brand of batteries and we can go from there.

Hi DS,

Can you please post the physical dimensions of the charger, if they are all different I am interested in the 15 and 20. is there any issue having these in an enclosed space or do they need air circulating for cooling?

Originally Posted by onesilop

Hi DS,

Can you please post the physical dimensions of the charger, if they are all different I am interested in the 15 and 20. is there any issue having these in an enclosed space or do they need air circulating for cooling?

click on the links in post #2

Products :: Battery Chargers :: ProNautic P 1215

Hi and thanks Kevin.

Hi onesilop. These chargers have fans, controlled by the charger and will switch on when needed, so they do need to be vented.

Hi Drivesafe, i have 2 x 237 Ah Haze gel batteries i need to charge and run an inverter in a cabin off grid, could i use a 2kva inverter generator to charge them through this type of battery charger? i use the batteries for running an inverter from 12 volt to 240 volt power for lights and laptop power. Thanks Philco