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Mick, you realize the thread is about lithium batteries......Quote:
Originally Posted by DiscoMick
Yes still simple but DC-DC is pretty much a given.
The reference to alternator is no different to your set up, battery accepting charge from the alternator and solar therefore they have a common connection.....DC-DC prioritizes the charge from one or the other.
Yes, I realise lithiums normally need a DC-DC if they're running straight off a smart alternator because they need 14 volts to charge properly.
However, is that still true if they're also getting solar, particularly if it's not a smart alternator?
lithium don't like to have voltage up their butt when they are fully charged so whatever you use to charge them needs to drop off when the lithium is fully charged.
to maximise available space, i use a 24v house panel and an epever mppt controller which has a lithium profile and the ability to setup your own custom profile if needed.
i run my 55ltr fridge, the oven, canopy lights and the compressor from my 100ah lithium battery and it isnt attached to the 130's charging circuit as yet as it hasn't been needed
so far, on cloudy days my setup has the lithium back at full charge by lunchtime at the latest so a lot of solar potential is lost.
i was looking at using a solenoid based setup so that i can use the solar through the controller to top up charge the two red tops i have under the passenger seat of the 130 when at rest and isolate the lithium when driving. there are some substantial issues involved in doing this due discharge rates etc with the lithium, if the wet cells are a little low.
when the caravan is attached to the 130 it hooks into the 130's charging circuit to charge the two 100ah agms.
at rest the caravan has a 160w 12v solar panel setup on a lead that keeps it happy
i haven't had to implement the lithium / wetcell setup above, as my traxide controller and the batteries have coped with everything i have thrown at them thus far
having one of these new fangled alternators would throw the cat amongst the pigeons i think ......
Yes, I realise lithiums normally need a DC-DC if they're running straight off a smart alternator because they need 14 volts to charge properly.
However, is that still true if they're also getting solar, particularly if it's not a smart alternator?
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Hi Mick, while you can charge lithium batteries direct from an alternator, even some variable voltage type, the problem is that the current capable of being supplied by an alternator, particularly a large alternator, can easily exceed a lithium battery’s safe maximum charge current.
If you have a bank of lithium batteries, as the load is spread over a number of batteries, then you could bulk charge the lithium’s and then finish the charge with the appropriate type of charger.
I read that most if not all Lithium batteries have built in BMS to protect them from over and under charge. Does this not control limit both over discharging or over charging, or is this marketing BS than fact?
To be fair, this is a little tongue in cheek too as I don’t trust anyone or anything lol
Hi again Mick, the BMS protects against over voltage charging and under voltage discharging.
Discharging and charging currents are not controlled by the BMS.
While the BMS is supposed to protect against too high a voltage being applied to the lithium’s cells, Caution should still be used to make sure over voltage charging does not occur.
Quote:
Originally Posted by drivesafe
Sorry to prolong this [bigwhistle] but I wanted to understand why 8 B&S gauge cable is apparently too thin for this application.
Surely it's dependent on practical requirements which in turn influence the design parameters.
I used 8 B&S for general charging of a second battery: it was more than satisfactory. For a 5m run carrying a max of 15 amps, the difference in voltage drop between a 6 B&S and 8 B&S was a theoretical 0.063V (0.094V for 6 B&S and 0.16V for 8 B&S). In the scheme of things for charging a battery this difference is " in the noise".
In line with this, I wondered why virtually all mains powered battery chargers (including my good mate's expensive CTek collection!) have charging leads of approx 2m of seemingly 3-4mm cable which has about 10 times the resistance of 6 B&S!
So with due respect to all the practical knowledge in these contributions, perhaps 6 B&S isn't necessary as a one size fits all approach. Surely as long as the gauge of cable used ( in this case 8 B&S) is "fit for purpose" ...which I believe has been demonstrated, then why the angst?
Maybe I'm missing something...
I am hooking up a lithium battery to a CTEK ( new lithium suitable one )
and my starter battery (calcium lead acid)
The ctek has a bifurcated cable that come out of the side
a red branch that is connected up if you have a smart alternator . I don’t so left this unconnected
The BLACK branch is the battery selector cable
the instructions in the ctek manual say
normal battery ……not connected
AGM …………………….earth
lithium………………..+12 v
QUESTION ……where do I connect it to ?
Hi sandman and the instruction relate the the battery type that is being charged.Quote:
Originally Posted by landoman
In your case, the lithium, so connect the lead to the 12v positive ( + ) going into your DC/DC device.
This is the 12v cable coming from your cranking battery.