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19v battery system. Will a programmable MPPT work?

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rruff

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Will a MPPT charge controller work ok with a 19v battery? They say 12v or 24v and that they auto-sense. They also have custom profiles... but does anyone know if any will work with an odd voltage within that range?


Why? Because the biggest load on my system will be a laptop computer (max 230W; it's gaming computer with a video card), which specs 19v input. It's not only the highest max draw in my system, but probably the highest average as well. I'd hoped it would run on 12v (the battery is 3 cell, 11.4v nominal) but it does not. The laptop doesn't actually use 19v internally; rather it takes 19v and converts it to whatever the different components need. I suspect it would run on 24v just fine, since step-down converters usually do ok with a wide range of inputs, but that's kinda risky since I'm not certain.

So... if I built a 19v battery for the camper, the plan would be to use a 19v-12v DC-DC buck converter (these are cheap and very efficient) for 12v loads, which will mostly be lights. Maybe a refrigerator, but I doubt it. Possibly an electric blanket.
 
rruff said:
Will a MPPT charge controller work ok with a 19v battery? They say 12v or 24v and that they auto-sense.
Click to expand...
As a guess and depending on the charge controller the auto sense may go either way, 12v or 24v, if the laptop's battery is flat or fully charged.
Just use the vans battery for the CC, a DC-DC laptop charger ($10 Ebay) for the first trip.

The 2nd trip- a cheap inverter ($50 Ebay) and a couple of power boards holding all the chargers for the phones, cameras, laptops, fitbits, drone batteries......

The 3rd trip - leave all at home and enjoy the outdoors!
 
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I think you might have misunderstood...? The 19v battery is my camper house battery, 6s LFP. I'll be living in this full time, and charging with solar. The reason for 19v is so I can run the laptop directly from the camper battery with no gadgets in between.
 
rruff said:
The reason for 19v is so I can run the laptop directly from the camper battery with no gadgets in between.
Click to expand...

The "gadget" would be a $0.30 LM7818, a $0.25 transistor, a couple of small diodes and a capacitor. Any tinkerer with a soldering iron will build that for you in 10 minutes. And it would also stabilise the (24V) battery output somewhat.
 
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It isn't the cost that concerns me, but the losses, reliability, and failure modes.... Could it kill the laptop? Seems better to make a direct connection to the battery. IME laptops aren't that sensitive to the input voltage; they have internal regulators to step down the voltage for components. I ran other laptops for many years directly from 12v batteries.

Does anyone know if a programmable MPPTs will work with 19v, or are they stuck on 12v multiples?
 
Rather than kill it, it would (somewhat) protect it.
Don B. Cilly said:
And it would also stabilise the (24V) battery output somewhat.
Click to expand...

The 78xx chips are tried, tested and reliable. They're "voltage regulators". 6-7V above output (a 24V battery runs mostly over 26V) are good enough for a stable, clean, regulated output.
Much better to have 24V stabilised to 19 than 19V unstabilised. Your "19V battery" will likely run at some 21-22V most of the time anyway, and have ripples under charge.

[EDIT] If you decide to go the 7818 route (believe me, do :·) just let your tinkerer know about the "diode trick" - if he doesn't know it already. The 7818 will make 18V. To have it make 19, put a couple of small diodes between the common negative and the battery negative. Say they have a ½V forward drop each, two in series will increase output by 1V. And protect the whole against reverse polarity ;·)
- increase output by 1V
 
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rruff said:
I think you might have misunderstood...? The 19v battery is my camper house battery, 6s LFP. I'll be living in this full time, and charging with solar.
Click to expand...
Oh. You mean something like the -
electrodacus
Someone using one may give more info.
Another option, sans mppt, is just using a programmable battery charging module.
 
sunshine said:
Oh. You mean something like the -
electrodacus
Someone using one may give more info.
Another option, sans mppt, is just using a programmable battery charging module.
Click to expand...
I saw those when I was searching for a BMS. Still not available. I'd still need a charger though, right?

I was hoping that off the shelf programmable MPPTs would charge 19v batteries. Is the answer to that no, or has it not been tried?
 
I see two problems, the battery is seldom 19V and no, cheap charge controllers are not set up for random voltages. But, never say never. Perhaps there is one. Instead of a charge controller I would just use a buck converter with current limiting to charge the battery.
 
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afaik my Morningstar will allow about anything appropriate for 12 to 48 volt battery and anything between.
Clear warning that there is no boundaries to prevent destroying the battery.
 
rruff said:
Says up to 1.5A. I need 10x that amount.
Click to expand...
Don B. Cilly said:
The "gadget" would be a $0.30 LM7818, a $0.25 transistor,
Click to expand...

The 7818 would just drive the base of the transistor - which would carry the current.
You can have dozens of amps that way.

Still, you want to have a "19V" battery, feed 22V unstabilised to your laptop, you can certainly do that.
Personally, I wouldn't, but just get a programmable charge controller and tell it to charge the battery to whatever you think best.
-
 
What voltage does the laptop charger put on the internal battery? I doubt there is isolation from the higher voltage.
 
time2roll said:
What voltage does the laptop charger put on the internal battery? I doubt there is isolation from the higher voltage.
Click to expand...
The laptop powersupply says 19.5v. I doubt any components in the laptop are fed that voltage, rather it's stepped-down internally. The battery is 11v.
 
How did you come to settle on building a 6s LiFePO4? That's a very odd configuration to be working with.
 
Don B. Cilly said:
Still, you want to have a "19V" battery, feed 22V unstabilised to your laptop, you can certainly do that.
-
Click to expand...
I've run several laptops directly from 12v systems for years, with no problem. There may be exceptions, but I don't think they are sensitive to input voltage at all, rather it's converted and stabilized internally.
 
rruff said:
The laptop is by far my biggest load, so I thought it made sense to optimize for it.
Click to expand...
Seems odd to build a system to suit a 19v laptop when it'd be easier/cheaper to build a 12v system and just use a small inverter to plug the laptop charger into and deal with the small loss you'll get. You'll probably go through a few laptops in the lifetime of the battery system and who knows what the next one will need for DCV

You need to determine the 24hr laptop draw from the AC as it won't be 230x24
 
It is unconventional... but it's easy/cheaper/safer/more efficient/more reliable to have a system that directly powers the biggest load and most expensive device I use. Turning DC into AC then back into DC is way more complicated and is very inefficient.
 
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