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TimV 09-08-2018 10:18 PM

Ac to dc low voltage high current

At the moment i drive an hybrid car witch has in perfect conditions an electric range of 50km. To work and back home is 54km. So i cant do that full electric. The furthest i went was 52km without diesel or recharging.

At work i have 4 AGM 12V batteries and an 2000W ac inverter in the trunk and with that i recharge the car partially so i can get home full electric. The power inverter accepts a voltage up to 16,5Volt. And stops at 11Volt.

I have around 10kWh of lithium cells. And want to build an 4cell serie configuration.

But the current charger is only for lead batteries and wont charge higher then 14,6Volt.

I need an 16V charger so i can use the litium batterie.

I want to build or buy an charger that can charge the batterie in maximum 8 hours.

Is there an solution for me?

Thanks in advance.

Stubby79 09-09-2018 01:50 AM

You can probably modify your lead acid charger to output a few more volts, assuming it outputs enough amps in the first place to charge your batteries in time. How hard that is to do depends on your charger. A "dumb" charger with a simple voltage limit cutoff will require figuring out how to change the circuitry to cut off at the correct voltage. An "intelligent" charger, if you're lucky, will have an adjustable potentiometer to easily change the output voltage, within reasonable limits. Either way, you'll want some kind of BMS to protect you lithium batteries from over-charging.

Or you can look for an inverter that runs on a higher voltage and configure your lithium pack to match it. You'd still need a new charger, but seeing as it would be lower amperage, it would be more affordable. Doubt it would cover the cost of a new inverter, though.

The question that comes to mind is...where's the nearest mains outlet that you could plug in to instead?

TimV 09-09-2018 03:43 AM

The only affordable way to charge is at home or by friends and familie. At work there is no way i can charge. In the city close by there are chargingunits. But the money they ask for every kWh kost more then ik use my diesel engine. And overhere diesel kost 1,40/liter.

I use around 0,5 liter every workday. That cost 0,70. Plus the 1,65 of electricity charging at home. Makes 2,35 for 55km.

Using the battery in the trunk: 1,65 for the car. And 0,5 electiricity makes 2,15 for 55km.

Using the expensive charge units. 0,60 starting and 0,40 for every kWh. And the unitbwil charge the car full. That will be around 6kWh = 3 and then i need to charge the car back full at home witch will be around 1 makes a total of 4 for 55km. And that is riduculus.

The current charger i have is the Telwin Pulse 50. It puts out 40A at the 12V.

Stubby79 09-09-2018 04:40 AM

We're talking about typical lithium batteries, like 18650 cells, judging by the voltage you're trying to achieve. 14.6 would be perfect for LiFePO4 cells, if you don't already own the lithium cells you're mentioning.

I'm not having much luck finding a matching charger. You can buy DC-DC voltage converters that will bump the voltage up. Your challenge there is convincing your smart charger to turn on and stay on to deliver power to the DC-DC converters. Using those will result in a "dumb" charger, so you'd better be sure to use a BMS to protect your cells.

You could build your own charger out of an old welder, but chances are if you have to ask, you don't have the knowledge/skills to do this on your own. Transformer based chargers won't be very efficient.

Delta-Q chargers are efficient and programmable from the manufacturer, but they're on the wrong side of the pond and generally avoid dealing at the consumer level. You might have luck finding a Chinese manufacturer who will send you a charger to your specifications. Look for the guys selling chargers that ask you to supply your chemistry and voltage needs.

teoman 09-09-2018 06:57 PM

Where are these 10kwh worth of cells you speak of?

If you are going to lug them around, might aswell hook them up directly to your cars battery. Or try to charge the batteries without the inverter.

10kwh in 8 hours is like a 1200W charger. Me personally woulg go for several imax type hobby chargers. Can charge anything from anything.

TimV 09-09-2018 08:53 PM

The lithium cells (1200) are in my shed. Ready to be solderd together. The first wish is that it is directly hooked to the cars battery. But there are no electrical schemes available.

teoman 09-10-2018 04:41 PM

Says it has 200 lithium ion cells. Each monitored.

freebeard 09-12-2018 06:05 PM


Is there an solution for me?
Pump up the tires?

TimV 09-13-2018 02:51 AM

Already at 50 psi

ratgreen 09-14-2018 11:09 AM

What type of lithium batteries? 18650 Lion? Lifepo4 ?

If 18650, charge them to 4.15v each, so 16.6v total.

For 10kw, thats 10,000w / 16.6a = 602 a/h

602ah / 8 hours = 75 amp charger. That's pretty serious. Charging also has to be CV, and cut off at when charging current = less than 3% charge current.

You also need to consider what the C (charge/discharge) rating of your cells are to see how much current they can handle when charging. If its 18650, and 10kw like you say, thats 602ah. Which if we assume your cells are 2500mah each for example, thats 240 cells in parallel. So you should be fine actually charging at 75 amps.

(Someone correct me if my maths is wrong)

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