Lithium charger

[bagmaker]

OK, I know my limits, aint too bright on the electrical front. Bright enough to be dangerous.
So-

Why aren't lithiums charged with a high amperage, programmable 3-4v charger?

Yes, I know they don't exist -or at least I couldn't find such a beast.
I recognise that there would be a copper issue with some large cable due to the lower voltage but proximity to batts could solve that.

Considering the bulk of issues dealing with Lithium are cells out of balance, either from low or high voltage - how come we don't charge the individual cells instead of a "battery" @ 12 or 24v nominal? Surely a 3.5v charge running to each cell would be safer and simpler?
What am I missing, is such a thing impossible to make??

All thoughts valued.....

[BruceS]

Yep, I'll have 16 of 'em!
Each one needs to be 100% TOTALLY isolated from each other. Can you do that with 16 connected to 16 cells that ARE connected to each other?
I'm reliably informed there IS a solution in the making.
The problem is trying to ensure the 'invention' remains unique and very difficult to copy. (& mass produce in an inferior way)

[bagmaker]

Yep, I'll have 16 of 'em!
Each one needs to be 100% TOTALLY isolated from each other. Can you do that with 16 connected to 16 cells that ARE connected to each other?
I'm reliably informed there IS a solution in the making.
The problem is trying to ensure the 'invention' remains unique and very difficult to copy. (& mass produce in an inferior way)

Ahhhh, connected, that makes sense....
Diodes?
Not really sure its an invention, just a theory. China will copy it pretty quick

Looking forward to the solution of course, cannot wait!!

[dapope]

the solution is simple. Dont overchargeto the level of cell runaway
Its the how is the issue

[T1 Terry]

There are high output multiple cell chargers available that will both charge and balance the cells, not cheap and must programmed every time they are used. http://www.progressiverc.com/the-big-ri ... combo.html
There are plans afoot to develop cell level charging at better than the 4 amps available at the moment, but once the system is set up and balanced properly the need for balance charging is rare. More a problem with 24v systems and 48v systems, extremely rare for a problem with 12v system...... if they are set up properly and that is the key.

T1 Terry

[Bill]

When I bought my 100 ah cells from Trev of Basically Natural he had for sale 3.7v 4 amp switchmode chargers for $20 each. These are totally isolated and you would need 1 for each cell and a bank of plugboards to power them. I bought one to use to top up weak cells and use some headlight bulbs to drain the high cells to manually balance the bank.
To use that as the only charger they would need to produce much higher amperage, and that is difficult to do and keep heat and cost under control. It works, but the present way is cheaper to do.

[Dot]

Hi & welcome Bill.

[T1 Terry]

When I bought my 100 ah cells from Trev of Basically Natural he had for sale 3.7v 4 amp switchmode chargers for $20 each. These are totally isolated and you would need 1 for each cell and a bank of plugboards to power them. I bought one to use to top up weak cells and use some headlight bulbs to drain the high cells to manually balance the bank.
To use that as the only charger they would need to produce much higher amperage, and that is difficult to do and keep heat and cost under control. It works, but the present way is cheaper to do.

Hi Bill and welcome to the forum. The method you are using is probably the best you will ever need. Monitor cell voltages, stop charging if a cell reaches 3.6v before the battery reaches 14v and drops back to 13.8v float, if one does regularly reach 3.6v then charge the lowest cell with the little charger. Couldn't really be much easier than that and the amount that needs to be added to the low cell is so small the little charger has the problem sorted within an hr or so. The initial pack conditioning and balancing takes quite a bit more, but once it's done it doesn't require much to keep them within an acceptable balance.

T1 Terry

[native pepper]

I've had built dedicated solar charge controllers for lifepo4 and they work magnificently, even to the point where I've disconnected my BMS and active cell balancers. Now only use cheap 4-8 cell voltage alarms from ebay and in the last 6 months of full daily use on my house, the alarms have never gone of and my packs sits on 3.5v when fully charged. The voltage difference between cells is so minute, it doesn't matter and I've deliberately drained them to see how the cells were at 12v and all cells within .2v of each other. The way you connect up and the size of your pack banks I've discovered, makes a big difference to charging and balancing.

I'm now running my system on 500ah banks, my controllers are 60amp and each one connected to 750w solar running in parallel with the other controllers. Doing it this way has made things so much easier and safer. Also changed my bus set up after a lot of experimenting and now have 710w solar running through one 60amp controllers into 480ah lifepo4. Instead of having the extra 300w solar and 2 x 40ah charge controllers, made little difference expect for the ability to heat more water in the afternoon. It only takes about 1 hour to heat our hot water and when driving, it's heated by a heat exchanger from the engine and stored in an 80lt old S/S car LPG tank.

[BruceS]

How have you been traveling Bill? Still got those Li batteries charged up?
Very hard down south at present .... only see the sun for minutes at a time!